Recently, an electronic transformer for halogen lamps caught my eye in a store. Such a transformer costs a penny - only $2.5, which is several times cheaper than the cost of the components used in it. The block was purchased for experiments. As it turned out later, it did not have protection and a real explosion occurred during a short circuit... The transformer was quite powerful (150 watts), so a fuse was installed at the input, which literally burst. After checking, it turned out that half of the components burned out. Repairs will be expensive, and there is no need to waste your nerves and time, it is better to buy a new one. The next day, three transformers for 50, 105 and 150 watts were purchased at once.

It was planned to modify the unit, since it was a UPS - without any filters or protections.

After modification, the result should have been a powerful UPS, the main feature of which was its compactness.
To begin with, the unit was equipped with a surge protector.

The inductor was unsoldered from the DVD player's power supply and consists of two identical windings, each containing 35 turns of 0.3mm wire. Only passing through the filter, voltage is supplied to the main circuit. To smooth out low-frequency interference, 0.1 µF capacitors were used (select with a voltage of 250-400 volts). The LED indicates the presence of mains voltage.

Voltage regulator

A circuit using only one transistor was used. This is the simplest circuit available, contains a couple of components and works very well. The disadvantage of the circuit is that the transistor overheats under heavy loads, but it’s not that bad. In the circuit you can use any powerful bipolar low-frequency transistors of reverse conduction - KT803,805,819,825,827 - I recommend using the last three. The trimmer can be taken with a resistance of 1...6.8k, we take an additional protective resistor with a power of 0.5-1 Watt.
The regulator is ready, let's move on.

Protection

Another simple scheme, essentially this is protection against overturning. Literally any relay for 10-15 Amps. You can also use any rectifier diode with a current of 1 ampere or more (the widely used 1N4007 does an excellent job). The LED indicates incorrect polarity. This system turns off the voltage if there is a short circuit at the output or the device being tested is incorrectly connected. The power supply can be used to test the functionality of homemade ULFs, converters, car radios, etc., without having to worry about accidentally mixing up the power polarity.

In the future we will look at some more simple modifications of the electronic transformer, but for now we have a simple, compact and powerful UPS that can be used as a laboratory unit for a beginner.

List of radioelements

Designation	Type	Denomination	Quantity	My notepad
T1	Bipolar transistor	KT827A	1	To notepad
VD1	Rectifier diode	1N4007	1	To notepad
	Diode bridge		1	To notepad
C1, C2	Capacitor	0.1 µF	2	To notepad
C3	Capacitor	0.22 µF	1	To notepad
C4-C5	Electrolytic capacitor	3300 µF	2	To notepad
R2	Resistor	480 Ohm	1	To notepad
R3	Variable resistor	1 kOhm	1	To notepad
R4	Resistor	2.2 kOhm	1	To notepad
R5	Resistor

Experiments with the electronic transformer Taschibra (Tashibra, Tashibra). Electronic transformers circuits

Experiments with electronic transformer Taschibra (Tashibra, Tashibra)

I think that the advantages of this transformer have already been appreciated by many of those who have ever dealt with the problems of powering various electronic structures. And this electronic transformer has many advantages. Light weight and dimensions (as with all similar circuits), ease of modification to suit your own needs, the presence of a shielding housing, low cost and relative reliability (at least, if extreme conditions and short circuits are avoided, a product made according to a similar circuit can work long years). The range of application of power supplies based on "Taskhibra" can be very wide, comparable to the use of conventional transformers.

The use is justified in cases of shortage of time, funds, or lack of need for stabilization. Well, shall we experiment? Let me make a reservation right away that the purpose of the experiments was to test the Tasshibra triggering circuit under various loads, frequencies and the use of various transformers. I also wanted to select the optimal ratings of the components of the PIC circuit and check the temperature conditions of the circuit components when operating under various loads, taking into account the use of the Tasсhibra case as a radiator.

ET scheme Taschibra (Tashibra, Tashibra)

Despite the large number of published electronic transformer circuits, I will not be too lazy to once again post it for review. Look at Fig.1, illustrating the "Tashibra" filling.

The diagram is valid for ET "Tashibra" 60-150W. The mockery was carried out on ET 150W. It is assumed, however, that due to the identity of the circuits, the results of the experiments can be easily projected onto instances of both lower and higher power.

And let me remind you once again what “Tashibra” is missing for a full-fledged power supply.1. Lack of an input smoothing filter (also known as an anti-interference filter, which prevents conversion products from entering the network), 2. Current PIC, which allows excitation of the converter and its normal operation only in the presence of a certain load current, 3. Lack of output rectifier,4. Lack of output filter elements.

Let's try to correct all of the listed shortcomings of "Taskhibra" and try to achieve its acceptable operation with the desired output characteristics. To begin with, we won’t even open the housing of the electronic transformer, but simply add the missing elements...

1. Input filter: capacitors C`1, C`2 with a symmetrical two-winding choke (transformer) T`12. diode bridge VDS`1 with smoothing capacitor C`3 and resistor R`1 to protect the bridge from the charging current of the capacitor.

The smoothing capacitor is usually selected at the rate of 1.0 - 1.5 µF per watt of power, and a discharge resistor with a resistance of 300-500 kOhm should be connected in parallel to the capacitor for safety (touching the terminals of a capacitor charged with a relatively high voltage is not very pleasant). Resistor R`1 can replace with a 5-15Ohm/1-5A thermistor. Such a replacement will reduce the efficiency of the transformer to a lesser extent.

At the output of the ET, as shown in the diagram in Fig. 3, we connect a circuit of diode VD`1, capacitors C`4-C`5 and inductor L1 connected between them to obtain a filtered DC voltage at the “patient” output. In this case, the polystyrene capacitor placed directly behind the diode accounts for the main share of absorption of conversion products after rectification. It is assumed that the electrolytic capacitor, “hidden” behind the inductance of the inductor, will perform only its direct functions, preventing voltage “dip” at the peak power of the device connected to the ET. But it is also recommended to install a non-electrolytic capacitor in parallel with it.

After adding the input circuit, changes occurred in the operation of the electronic transformer: the amplitude of the output pulses (up to the diode VD`1) increased slightly due to the increase in the voltage at the input of the device due to the addition of C`3, and modulation with a frequency of 50 Hz was practically absent. This is at the load calculated for the electric vehicle. However, this is not enough. "Tashibra" does not want to start without significant load current.

Installing load resistors at the output of the converter to create any minimum current value capable of starting the converter only reduces the overall efficiency of the device. Starting at a load current of about 100 mA is carried out at a very low frequency, which will be quite difficult to filter if the power supply is intended for joint use with UMZCH and other audio equipment with low current consumption in the no-signal mode, for example. The amplitude of the pulses is also less than at full load.

The change in frequency in different power modes is quite strong: from a couple to several tens of kilohertz. This circumstance imposes significant restrictions on the use of "Tashibra" in this (for now) form when working with many devices.

But let's continue. There have been proposals to connect an additional transformer to the ET output, as shown, for example, in Fig. 2.

It was assumed that the primary winding of the additional transformer is capable of creating a current sufficient for the normal operation of the basic ET circuit. The offer, however, is tempting only because without disassembling the electric transformer, using an additional transformer you can create a set of necessary (to your liking) voltages. In fact, the no-load current of the additional transformer is not enough to start the electric vehicle. Attempts to increase the current (such as a 6.3VX0.3A light bulb connected to an additional winding), capable of ensuring NORMAL operation of the ET, only resulted in the converter starting up and the light bulb lighting up.

But perhaps someone will be interested in this result, because... connecting an additional transformer is also true in many other cases to solve many problems. So, for example, an additional transformer can be used in conjunction with an old (but working) computer power supply, capable of providing significant output power, but having a limited (but stabilized) set of voltages.

One could continue to search for the truth in the shamanism around "Tashibra", however, I considered this topic exhausted for myself, because to achieve the desired result (stable start-up and return to operating mode in the absence of load, and, therefore, high efficiency; a slight change in frequency when the power supply is operating from minimum to maximum power and stable start-up at maximum load) it is much more effective to get inside the Tashibra "and make all the necessary changes in the circuit of the ET itself in the manner shown in Figure 4. Moreover, I collected about fifty similar circuits back in the era of Spectrum computers (precisely for these computers). Various UMZCHs, powered by similar power supplies, are still working somewhere. PSUs made according to this scheme showed their best performance, working while being assembled from a wide variety of components and in various options.

Are we redoing it? Certainly!

Moreover, it is not at all difficult.

We solder the transformer. We warm it up for ease of disassembly in order to rewind the secondary winding to obtain the desired output parameters as shown in this photo or using any other technologies.

In this case, the transformer is soldered only in order to inquire about its winding data (by the way: W-shaped magnetic core with a round core, standard dimensions for computer power supplies with 90 turns of the primary winding, wound in 3 layers with a wire with a diameter of 0.65 mm and 7 turns secondary winding with a wire folded five times with a diameter of approximately 1.1 mm; all this without the slightest interlayer and interwinding insulation - just varnish) and make room for another transformer.

For experiments, it was easier for me to use ring magnetic cores. They take up less space on the board, which makes it possible (if necessary) to use additional components in the volume of the case. In this case, a pair of ferrite rings with outer and inner diameters and heights of 32x20x6mm, respectively, folded in half (without gluing) - N2000-NM1 - was used. 90 turns of the primary (wire diameter - 0.65 mm) and 2X12 (1.2 mm) turns of the secondary with the necessary inter-winding insulation.

The communication winding contains 1 turn of mounting wire with a diameter of 0.35 mm. All windings are wound in the order corresponding to the numbering of the windings. Insulation of the magnetic circuit itself is mandatory. In this case, the magnetic circuit is wrapped in two layers of electrical tape, by the way, securely fixing the folded rings.

Before installing the transformer on the ET board, we unsolder the current winding of the commutating transformer and use it as a jumper, soldering it there, but without passing the transformer rings through the window.

We install the wound transformer Tr2 on the board, soldering the leads in accordance with the diagram in Fig. 4. and pass the winding wire III into the window of the commutating transformer ring. Using the rigidity of the wire, we form a semblance of a geometrically closed circle and the feedback loop is ready. We solder a fairly powerful resistor (>1W) with a resistance of 3-10 Ohms into the gap in the mounting wire that forms windings III of both (switching and power) transformers.

In the diagram in Fig. 4, standard ET diodes are not used. They should be removed, as should resistor R1, in order to increase the efficiency of the unit as a whole. But you can neglect a few percent of the efficiency and leave the listed parts on the board. At least at the time of the experiments with ET, these parts remained on the board. The resistors installed in the base circuits of the transistors should be left - they perform the functions of limiting the base current when starting the converter, facilitating its operation on a capacitive load.

Transistors should certainly be installed on radiators through insulating heat-conducting gaskets (borrowed, for example, from a faulty computer power supply), thereby preventing their accidental instant heating and ensuring some personal safety in case of touching the radiator while the device is operating.

By the way, the electrical cardboard used in ET to insulate transistors and the board from the case is not thermally conductive. Therefore, when “packing” the finished power supply circuit into a standard case, exactly these gaskets should be installed between the transistors and the case. Only in this case will at least some heat removal be ensured. When using a converter with powers over 100W, an additional radiator must be installed on the device body. But this is for the future.

In the meantime, having finished installing the circuit, let’s perform one more safety point by connecting its input in series through an incandescent lamp with a power of 150-200 W. The lamp, in the event of an emergency (short circuit, for example), will limit the current through the structure to a safe value and, in the worst case, create additional illumination of the work space.

In the best case, with some observation, the lamp can be used as an indicator, for example, of through current. Thus, a weak (or slightly more intense) glow of the lamp filament with an unloaded or lightly loaded converter will indicate the presence of a through current. The temperature of the key elements can serve as confirmation - heating in through-current mode will be quite fast. When a working converter is operating, the glow of a 200-watt lamp filament, visible against the background of daylight, will appear only at the threshold of 20-35 W.

First start

So, everything is ready for the first launch of the converted "Tashibra" circuit. To begin with, we turn it on - without load, but do not forget about the pre-connected voltmeter to the output of the converter and an oscilloscope. With correctly phased feedback windings, the converter should start without problems.

If the start-up does not occur, then we pass the wire passed through the window of the commutating transformer (having previously unsoldered it from resistor R5) on the other side, giving it, again, the appearance of a completed turn. Solder the wire to R5. Apply power to the converter again. Did not help? Look for errors in installation: short circuit, “missing connections”, erroneously set values.

When a working converter is started with the specified winding data, the display of an oscilloscope connected to the secondary winding of transformer Tr2 (in my case, half of the winding) will display a time-invariant sequence of clear rectangular pulses. The conversion frequency is selected by resistor R5 and in my case, with R5 = 5.1 Ohm, the frequency of the unloaded converter was 18 kHz.

With a load of 20 Ohms - 20.5 kHz. With a load of 12 Ohms - 22.3 kHz. The load was connected directly to the instrument-controlled transformer winding with an effective voltage value of 17.5 V. The calculated voltage value was slightly different (20 V), but it turned out that instead of the nominal 5.1 Ohm, the resistance installed on the board R1 = 51 Ohm. Be attentive to such surprises from your Chinese comrades.

However, I considered it possible to continue the experiments without replacing this resistor, despite its significant but tolerable heating. When the power delivered by the converter to the load was about 25 W, the power dissipated by this resistor did not exceed 0.4 W.

As for the potential power of the power supply, at a frequency of 20 kHz the installed transformer will be able to deliver no more than 60-65 W to the load.

Let's try to increase the frequency. When a resistor (R5) with a resistance of 8.2 Ohms is turned on, the frequency of the converter without load increases to 38.5 kHz, with a load of 12 Ohms - 41.8 kHz.

At this conversion frequency, with the existing power transformer you can safely service a load with a power of up to 120 W. You can experiment further with resistances in the PIC circuit, achieving the required frequency value, keeping in mind, however, that too high a resistance R5 can lead to generation failures and unstable startup of the converter . When changing the parameters of the PIC converter, you should control the current passing through the converter keys.

You can also experiment with the PIC windings of both transformers at your own peril and risk. In this case, you should first calculate the number of turns of the commutating transformer using the formulas posted on the page //interlavka.narod.ru/stats/Blokpit02.htm, for example, or using one of Mr. Moskatov’s programs posted on the page of his website // www.moskatov.narod.ru/Design_tools_pulse_transformers.html.

Improvement of Tasсhibra - a capacitor in the PIC instead of a resistor!

You can avoid heating resistor R5 by replacing it... with a capacitor. In this case, the PIC circuit certainly acquires some resonant properties, but no deterioration in the operation of the power supply is manifested. Moreover, a capacitor installed instead of a resistor heats up significantly less than the replaced resistor. Thus, the frequency with a 220nF capacitor installed increased to 86.5 kHz (without load) and amounted to 88.1 kHz when operating with a load. The startup and operation of the converter remained as stable as in the case of using a resistor in the PIC circuit. Note that the potential power of the power supply at such a frequency increases to 220 W (minimum). Transformer power: values are approximate, with certain assumptions, but not exaggerated.

Unfortunately, I did not have the opportunity to test a power supply with a large load current, but I believe that the description of the experiments performed is enough to draw the attention of many to such simple power converter circuits, worthy of use in a wide variety of designs .

I apologize in advance for possible inaccuracies, omissions and errors. I'll correct myself in answering your questions.

Konstantin (riswel)

Russia, Kaliningrad

Since childhood - music and electrical/radio equipment. I re-soldered a lot of different circuits for different reasons and just for fun, both my own and others’.

Over 18 years of work at North-West Telecom, he has made many different stands for testing various equipment being repaired. He designed several digital pulse duration meters, different in functionality and elemental base.

More than 30 improvement proposals for the modernization of units of various specialized equipment, incl. - power supply. For a long time now I have been increasingly involved in power automation and electronics.

Why am I here? Yes, because everyone here is the same as me. There is a lot of interest here for me, since I am not strong in audio technology, but I would like to have more experience in this area.

datagor.ru

Electronic transformers. Device and operation. Peculiarities

Let's consider the main advantages, advantages and disadvantages of electronic transformers. Let's consider the scheme of their work. Electronic transformers appeared on the market quite recently, but managed to gain wide popularity not only in amateur radio circles.

Recently, articles based on electronic transformers have often been seen on the Internet: homemade power supplies, chargers and much more. In fact, electronic transformers are a simple network switching power supply. This is the cheapest power supply. A phone charger costs more. The electronic transformer operates from a 220 volt network.

Device and principle of operation

Scheme of work

The generator in this circuit is a diode thyristor or dinistor. The 220 V mains voltage is rectified by a diode rectifier. There is a limiting resistor at the power input. It simultaneously serves as a fuse and protection against surges in mains voltage when turned on. The operating frequency of the dinistor can be determined from the ratings of the R-C chain.

In this way, the operating frequency of the generator of the entire circuit can be increased or decreased. The operating frequency in electronic transformers is from 15 to 35 kHz, it can be adjusted.

The feedback transformer is wound on a small core ring. It contains three windings. The feedback winding consists of one turn. Two independent windings of master circuits. These are the basic windings of transistors of three turns.

These are equal windings. Limiting resistors are designed to prevent false triggering of transistors and at the same time limit the current. Transistors are used of high-voltage type, bipolar. MGE 13001-13009 transistors are often used. It depends on the power of the electronic transformer.

t of half-bridge capacitors also depends on a lot, in particular the power of the transformer. They are used with a voltage of 400 V. The power also depends on the overall dimensions of the core of the main pulse transformer. It has two independent windings: mains and secondary. Secondary winding with a rated voltage of 12 volts. It is wound based on the required output power.

The primary or network winding consists of 85 turns of wire with a diameter of 0.5-0.6 mm. Low-power rectifier diodes with a reverse voltage of 1 kV and a current of 1 ampere are used. This is the cheapest rectifier diode you can find in the 1N4007 series.

The diagram shows in detail the capacitor that sets the frequency of the dinistor circuits. A resistor at the input protects against voltage surges. Dinistor series DB3, its domestic analogue KN102. There is also a limiting resistor at the input. When the voltage on the frequency-setting capacitor reaches the maximum level, breakdown of the dinistor occurs. A dinistor is a semiconductor spark gap that operates at a certain breakdown voltage. Then it sends a pulse to the base of one of the transistors. The generation of the circuit begins.

Transistors operate in antiphase. An alternating voltage is generated on the primary winding of the transformer at a given dinistor operating frequency. On the secondary winding we get the required voltage. In this case, all transformers are designed for 12 volts.

Model of a transformer from the Chinese manufacturer Taschibra

It is designed to power 12 volt halogen lamps.

With a stable load, such as halogen lamps, such electronic transformers can operate indefinitely. During operation, the circuit overheats, but does not fail.

Operating principle

A voltage of 220 volts is supplied and rectified by the VDS1 diode bridge. Through resistors R2 and R3, capacitor C3 begins to charge. The charge continues until the DB3 dinistor breaks through.

The opening voltage of this dinistor is 32 volts. After it opens, voltage is supplied to the base of the lower transistor. The transistor opens, causing self-oscillation of these two transistors VT1 and VT2. How do these self-oscillations work?

Current begins to flow through C6, transformer T3, base control transformer JDT, transistor VT1. When passing through the JDT it causes VT1 to close and VT2 to open. After this, the current flows through VT2, through the base transformer, T3, C7. Transistors constantly open and close each other, working in antiphase. At the midpoint, rectangular pulses appear.

The conversion frequency depends on the inductance of the feedback winding, the capacitance of the transistor bases, the inductance of transformer T3 and capacitances C6, C7. Therefore, it is very difficult to control the conversion frequency. The frequency also depends on the load. To force the opening of transistors, 100-volt accelerating capacitors are used.

To reliably close the dinistor VD3 after generation occurs, rectangular pulses are applied to the cathode of the diode VD1, and it reliably closes the dinistor.

In addition, there are devices that are used for lighting, power powerful halogen lamps for two years, and work faithfully.

Power supply based on an electronic transformer

The mains voltage is supplied to the diode rectifier through a limiting resistor. The diode rectifier itself consists of 4 low-power rectifiers with a reverse voltage of 1 kV and a current of 1 ampere. The same rectifier is located on the transformer block. After the rectifier, the DC voltage is smoothed by an electrolytic capacitor. The charging time of capacitor C2 depends on resistor R2. At maximum charge, the dinistor is triggered, causing a breakdown. An alternating voltage is generated at the primary winding of the transformer at the operating frequency of the dinistor.

The main advantage of this circuit is the presence of galvanic isolation from a 220 volt network. The main disadvantage is the low output current. The circuit is designed to power small loads.

Transformer model DM-150T06A

Current consumption 0.63 ampere, frequency 50-60 hertz, operating frequency 30 kilohertz. Such electronic transformers are designed to power more powerful halogen lamps.

Advantages and Benefits

If you use the devices for their intended purpose, then there is a good function. The transformer does not turn on without an input load. If you simply plugged in a transformer, it is not active. You need to connect a powerful load to the output for work to begin. This feature saves energy. For radio amateurs who convert transformers into a regulated power supply, this is a disadvantage.

It is possible to implement an auto-on system and a short circuit protection system. Despite its shortcomings, an electronic transformer will always be the cheapest type of half-bridge power supply.

You can find higher quality inexpensive power supplies with a separate oscillator on sale, but they are all implemented on the basis of half-bridge circuits using self-clocking half-bridge drivers, such as the IR2153 and the like. Such electronic transformers work much better, are more stable, have short circuit protection, and have a surge filter at the input. But the old Taschibra remains indispensable.

Disadvantages of electronic transformers

They have a number of disadvantages, despite the fact that they are made according to good designs. This is the lack of any protection in cheap models. We have a simple electronic transformer circuit, but it works. This is exactly the scheme implemented in our example.

There is no line filter at the power input. At the output after the inductor there should be at least a smoothing electrolytic capacitor of several microfarads. But he is also missing. Therefore, at the output of the diode bridge we can observe an impure voltage, that is, all network and other noise is transmitted to the circuit. At the output we get a minimum amount of interference, since galvanic isolation is implemented.

The operating frequency of the dinistor is extremely unstable and depends on the output load. If without an output load the frequency is 30 kHz, then with a load there can be a fairly large drop to 20 kHz, depending on the specific load of the transformer.

Another disadvantage is that the output of these electronic transformers is variable frequency and current. To use it as a power supply, you need to rectify the current. You need to straighten it with pulse diodes. Conventional diodes are not suitable here due to the increased operating frequency. Since such power supplies do not implement any protection, if you just short-circuit the output wires, the unit will not just fail, but explode.

At the same time, during a short circuit, the current in the transformer increases to a maximum, so the output switches (power transistors) will simply burst. The diode bridge also fails, since they are designed for an operating current of 1 ampere, and in the event of a short circuit, the operating current increases sharply. The limiting resistors of the transistors, the transistors themselves, the diode rectifier, and the fuse, which should protect the circuit but does not, also fail.

Several other components may fail. If you have such an electronic transformer unit, and it accidentally fails for some reason, then it is not advisable to repair it, since it is not profitable. Just one transistor costs $1. And a ready-made power supply can also be bought for $1, completely new.

Power of electronic transformers

Today you can find different models of transformers on sale, ranging from 25 watts to several hundred watts. A 60 watt transformer looks like this.

The manufacturer is Chinese, producing electronic transformers with a power of 50 to 80 watts. Input voltage from 180 to 240 volts, network frequency 50-60 hertz, operating temperature 40-50 degrees, output 12 volts.

Electronic transformer circuit for 12V halogen lamps. How does an electronic transformer work?

The operation of the transformer is based on converting current from a 220 V network. The devices are divided by the number of phases, as well as the overload indicator. Modifications of single-phase and two-phase types are available on the market. The current overload parameter ranges from 3 to 10 A. If necessary, you can make an electronic transformer with your own hands. However, to do this, it is first important to familiarize yourself with the structure of the model.

Model diagram

The electronic transformer circuit for 12V halogen lamps involves the use of a pass-through relay. The winding itself is used with a filter. To increase the clock frequency, there are capacitors in the circuit. They are available in open and closed types. For single-phase modifications, rectifiers are used. These elements are necessary to increase current conductivity.

On average, the sensitivity of the models is 10 mV. With the help of expanders, problems with network congestion are solved. If we consider a two-phase modification, then it uses a thyristor. The specified element is usually installed with resistors. Their capacity is on average 15 pF. The level of current conduction in this case depends on the relay load.

How to do it yourself?

You can easily make an electronic transformer with your own hands. For this it is important to use a wired relay. It is advisable to select an expander for it of the pulse type. To increase the sensitivity parameter of the device, capacitors are used. Many experts recommend installing resistors with insulators.

To solve problems with voltage surges, filters are soldered. If we consider a homemade single-phase model, then it is more appropriate to select a modulator for 20 W. The output impedance in the transformer circuit should be 55 Ohms. The output contacts are soldered directly to connect the device.

Devices with capacitor resistor

The electronic transformer circuit for 12V halogen lamps involves the use of a wired relay. In this case, resistors are installed behind the plate. As a rule, modulators are used of the open type. Also, the electronic transformer circuit for 12V halogen lamps includes rectifiers that are matched with filters.

To solve switching problems, amplifiers are needed. The average output resistance is 45 ohms. Current conductivity, as a rule, does not exceed 10 microns. If we consider a single-phase modification, then it has a trigger. Some specialists use triggers to increase conductivity. However, in this case, heat losses increase significantly.

Transformers with regulator

The 220-12 V transformer with a regulator is quite simple. The relay in this case is usually used as a wired type. The regulator itself is installed with a modulator. To solve problems with reverse polarity there is a kenotron. It can be used with or without a cover.

The trigger in this case is connected through conductors. These elements can only work with pulse expanders. On average, the conductivity parameter of transformers of this type does not exceed 12 microns. It is also important to note that the negative resistance value depends on the sensitivity of the modulator. As a rule, it does not exceed 45 Ohms.

Using wire stabilizers

A 220-12 V transformer with a wire stabilizer is very rare. For normal operation of the device, a high-quality relay is necessary. The negative resistance indicator is on average 50 ohms. The stabilizer in this case is fixed on the modulator. This element is primarily intended to lower the clock frequency.

The heat losses from the transformer are insignificant. However, it is important to note that there is a lot of pressure on the trigger. Some experts recommend using capacitive filters in this situation. They are sold with or without a guide.

Models with diode bridge

A transformer (12 Volt) of this type is made on the basis of selective triggers. The threshold resistance of the models is on average 35 Ohms. To solve problems with frequency reduction, transceivers are installed. Direct diode bridges are used with different conductivities. If we consider single-phase modifications, then in this case the resistors are selected for two plates. The conductivity indicator does not exceed 8 microns.

Tetrodes in transformers can significantly increase the sensitivity of the relay. Modifications with amplifiers are very rare. The main problem with this type of transformers is negative polarity. It occurs due to an increase in the temperature of the relay. To remedy the situation, many experts recommend using triggers with conductors.

Model Taschibra

The electronic transformer circuit for 12V halogen lamps includes a trigger with two plates. The model's relay is of the wired type. To solve problems with reduced frequency, expanders are used. In total, the model has three capacitors. Therefore, network congestion problems rarely occur. On average, the output resistance parameter is kept at 50 Ohms. According to experts, the output voltage at the transformer should not exceed 30 W. On average, the sensitivity of the modulator is 5.5 microns. However, in this case it is important to take into account the load on the expander.

Device RET251C

The specified electronic transformer for lamps is produced with an output adapter. The model has a dipole type expander. There are a total of three capacitors installed in the device. A resistor is used to solve problems with negative polarity. The model's capacitors rarely overheat. The modulator is directly connected through a resistor. In total, the model has two thyristors. First of all, they are responsible for the output voltage parameter. Thyristors are also designed to ensure stable operation of the expander.

Transformer GET 03

The transformer (12 Volt) of this series is very popular. In total, the model has two resistors. They are located next to the modulator. If we talk about indicators, it is important to note that the modification frequency is 55 Hz. The device is connected via an output adapter.

The expander is matched with an insulator. To solve problems with negative polarity, two capacitors are used. There is no regulator in the presented modification. The conductivity index of the transformer is 4.5 microns. The output voltage fluctuates around 12 V.

Device ELTR-70

The specified 12V electronic transformer includes two pass-through thyristors. A distinctive feature of the modification is the high clock frequency. Thus, the current conversion process will be carried out without voltage surges. The model's expander is used without lining.

There is a trigger to reduce sensitivity. It is installed as a standard selective type. The negative resistance indicator is 40 ohms. For a single-phase modification this is considered normal. It is also important to note that the devices are connected via an output adapter.

Model ELTR-60

This transformer features high voltage stability. The model refers to single-phase devices. It uses a capacitor with high conductivity. Problems with negative polarity are solved by using an expander. It is installed behind the modulator. There is no regulator in the presented transformer. In total, the model uses two resistors. Their capacitance is 4.5 pF. According to experts, overheating of elements is observed very rarely. The output voltage to the relay is strictly 12 V.

Transformers TRA110

These transformers operate from a pass-through relay. The model’s expanders are used in different capacities. The average output impedance of the transformer is 40 ohms. The model belongs to two-phase modifications. Its threshold frequency is 55 Hz. In this case, dipole type resistors are used. In total, the model has two capacitors. To stabilize the frequency during operation of the device, a modulator operates. The conductors of the model are soldered with high conductivity.

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Electronic transformer conversion | all-he

An electronic transformer is a network switching power supply, which is designed to power 12 Volt halogen lamps. Read more about this device in the article “Electronic transformer (introduction)”.

The device has a fairly simple circuit. A simple push-pull self-oscillator, which is made using a half-bridge circuit, the operating frequency is about 30 kHz, but this indicator strongly depends on the output load.

The circuit of such a power supply is very unstable, it does not have any protection against short circuits at the output of the transformer, perhaps precisely because of this, the circuit has not yet found widespread use in amateur radio circles. Although recently there has been a promotion of this topic on various forums. People offer various options for modifying such transformers. Today I will try to combine all these improvements in one article and offer options not only for improvements, but also for strengthening the ET.

We won’t go into the basics of how the circuit works, but let’s get down to business right away. We will try to refine and increase the power of the Chinese Taschibra electric device by 105 watts.

To begin with, I want to explain why I decided to take on the powering and alteration of such transformers. The fact is that recently a neighbor asked me to make him a custom-made charger for a car battery that would be compact and lightweight. I didn’t want to assemble it, but later I came across interesting articles that discussed remaking an electronic transformer. This gave me the idea - why not try it?

Thus, several ETs from 50 to 150 Watts were purchased, but experiments with conversion were not always completed successfully; of all, only the 105 Watt ET survived. The disadvantage of such a block is that its transformer is not ring-shaped, and therefore it is inconvenient to unwind or rewind the turns. But there was no other choice and this particular block had to be remade.

As we know, these units do not turn on without load; this is not always an advantage. I plan to get a reliable device that can be freely used for any purpose without fear that the power supply may burn out or fail during a short circuit.

Improvement No. 1

The essence of the idea is to add short-circuit protection and also eliminate the above-mentioned drawback (activation of a circuit without an output load or with a low-power load).

Looking at the unit itself, we can see the simplest UPS circuit; I would say that the circuit has not been fully developed by the manufacturer. As we know, if you short-circuit the secondary winding of a transformer, the circuit will fail in less than a second. The current in the circuit increases sharply, the switches instantly fail, and sometimes even the basic limiters. Thus, repairing the circuit will cost more than the cost (the price of such an ET is about $2.5).

The feedback transformer consists of three separate windings. Two of these windings power the base switch circuits.

First, remove the communication winding on the OS transformer and install a jumper. This winding is connected in series with the primary winding of the pulse transformer. Then we wind only 2 turns on the power transformer and one turn on the ring (OS transformer). For winding, you can use a wire with a diameter of 0.4-0.8 mm.

Next, you need to select a resistor for the OS, in my case it is 6.2 ohms, but a resistor can be selected with a resistance of 3-12 ohms, the higher the resistance of this resistor, the lower the short-circuit protection current. In my case, the resistor is a wirewound one, which I do not recommend doing. We select the power of this resistor to be 3-5 watts (you can use from 1 to 10 watts).

During a short circuit on the output winding of a pulse transformer, the current in the secondary winding drops (in standard ET circuits, during a short circuit, the current increases, disabling the switches). This leads to a decrease in the current on the OS winding. Thus, generation stops and the keys themselves are locked.

The only drawback of this solution is that in the event of a long-term short circuit at the output, the circuit fails because the switches heat up quite strongly. Do not expose the output winding to a short circuit lasting more than 5-8 seconds.

The circuit will now start without load; in a word, we have a full-fledged UPS with short-circuit protection.

Improvement No. 2

Now we will try to smooth out the mains voltage from the rectifier to some extent. For this we will use chokes and a smoothing capacitor. In my case, a ready-made inductor with two independent windings was used. This inductor was removed from the UPS of the DVD player, although homemade inductors can also be used.

After the bridge, an electrolyte with a capacity of 200 μF should be connected with a voltage of at least 400 Volts. The capacitor capacity is selected based on the power of the power supply 1 μF per 1 watt of power. But as you remember, our power supply is designed for 105 Watts, why is the capacitor used at 200 μF? You will understand this very soon.

Improvement No. 3

Now about the main thing - increasing the power of the electronic transformer and is it real? In fact, there is only one reliable way to power it up without much modification.

For powering up, it is convenient to use an ET with a ring transformer, since it will be necessary to rewind the secondary winding; it is for this reason that we will replace our transformer.

The network winding is stretched across the entire ring and contains 90 turns of wire 0.5-0.65 mm. The winding is wound on two folded ferrite rings, which were removed from an ET with a power of 150 watts. The secondary winding is wound based on needs, in our case it is designed for 12 Volts.

It is planned to increase the power to 200 watts. That is why an electrolyte with a reserve, which was mentioned above, was needed.

We replace the half-bridge capacitors with 0.5 μF; in the standard circuit they have a capacity of 0.22 μF. We replace the bipolar switches MJE13007 with MJE13009. The power winding of the transformer contains 8 turns, the winding was done with 5 cores of 0.7 mm wire, thus, we have a wire in the primary with a total cross-section of 3.5 mm.

Go ahead. Before and after the chokes we place film capacitors with a capacity of 0.22-0.47 μF with a voltage of at least 400 Volts (I used exactly those capacitors that were on the ET board and which had to be replaced to increase the power).

Next, replace the diode rectifier. In standard circuits, conventional rectifier diodes of the 1N4007 series are used. The current of the diodes is 1 Ampere, our circuit consumes a lot of current, so the diodes should be replaced with more powerful ones in order to avoid unpleasant results after the first turn on of the circuit. You can use literally any rectifier diodes with a current of 1.5-2 Amps, a reverse voltage of at least 400 Volts.

All components except the generator board are mounted on a breadboard. The keys were secured to the heat sink through insulating gaskets.

We continue our modification of the electronic transformer, adding a rectifier and a filter to the circuit. The chokes are wound on rings of powdered iron (removed from the computer power supply) and consist of 5-8 turns. It is convenient to wind it using 5 strands of wire with a diameter of 0.4-0.6 mm each.

We select a smoothing capacitor with a voltage of 25-35 Volts; one powerful Schottky diode (diode assemblies from a computer power supply) is used as a rectifier. You can use any fast diodes with a current of 15-20 Amps.

all-he.ru

ELECTRONIC TRANSFORMER DIAGRAM FOR HALOGEN LAMPS

Currently, pulsed electronic transformers, due to their small size and weight, low price and wide range, are widely used in mass equipment. Thanks to mass production, electronic transformers are several times cheaper than conventional inductive transformers on iron of similar power. Although electronic transformers from different companies may have different designs, the circuit is practically the same.

Let's take for example a standard electronic transformer labeled 12V 50W, which is used to power a table lamp. The schematic diagram will be like this:

The electronic transformer circuit works as follows. The mains voltage is rectified using a rectifier bridge to a half-sinusoidal voltage with double the frequency. Element D6 of type DB3 in the documentation is called “TRIGGER DIODE”, - this is a bidirectional dinistor in which the polarity of the inclusion does not matter and it is used here to start the transformer converter. The dinistor is triggered during each cycle, starting the generation of a half-bridge. The opening of the dinistor can be adjusted. This can be done use, for example, for the function of adjusting the brightness of a connected lamp.The generation frequency depends on the size and magnetic conductivity of the feedback transformer core and the parameters of the transistors, usually in the range of 30-50 kHz.

Currently, the production of more advanced transformers with the IR2161 chip has begun, which provides both simplicity of design of the electronic transformer and a reduction in the number of components used, as well as high performance. The use of this microcircuit significantly increases the manufacturability and reliability of the electronic transformer for powering halogen lamps. The schematic diagram is shown in the figure.

Features of the electronic transformer on IR2161: Intelligent half-bridge driver; Load short circuit protection with automatic restart; Overcurrent protection with automatic restart; Frequency sweep to reduce electromagnetic interference; 150 µA micropower startup; Can be used with phase dimmers with leading and trailing edge control; Output voltage offset compensation increases durability lamps; Soft start, eliminating current overloads of lamps.

Input resistor R1 (0.25 watt) is a kind of fuse. Transistors of type MJE13003 are pressed to the body through an insulating gasket with a metal plate. Even when operating at full load, the transistors heat up slightly. After the mains voltage rectifier, there is no capacitor to smooth out the ripples, so the output voltage of the electronic transformer when operating on a load is a 40 kHz rectangular oscillation, modulated by 50 Hz mains voltage ripples. Transformer T1 (feedback transformer) - on a ferrite ring, the windings connected to the bases of the transistors contain a couple of turns, the winding connected to the connection point of the emitter and collector of the power transistors - one turn of single-core insulated wire. Transistors MJE13003, MJE13005, MJE13007 are usually used in ET. Output transformer on a ferrite W-shaped core.

To use an electronic transformer in a switching power supply, you need to connect a rectifier bridge on high-frequency diodes to the output (regular KD202, D245 will not work) and a capacitor to smooth out ripples. At the output of the electronic transformer, a diode bridge is installed using KD213, KD212 or KD2999 diodes. In short, we need diodes with a low voltage drop in the forward direction, capable of operating well at frequencies of the order of tens of kilohertz.

The electronic transformer converter does not work normally without a load, so it must be used where the load is constant in current and consumes sufficient current to reliably start the ET converter. When operating the circuit, it must be taken into account that electronic transformers are sources of electromagnetic interference, therefore an LC filter must be installed to prevent interference from penetrating the network and the load.

Personally, I used an electronic transformer to make a switching power supply for a tube amplifier. It also seems possible to power them with powerful Class A ULFs or LED strips, which are specifically designed for sources with a voltage of 12V and a high output current. Naturally, such a tape is connected not directly, but through a current-limiting resistor or by correcting the output power of an electronic transformer.

Electronic Transformers Forum

Discuss the article ELECTRONIC TRANSFORMER DIAGRAM FOR HALOGEN LAMPS

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Electronic transformers for 12 V halogen lamps

Power supply

Home Radio amateur Power supply

The article describes the so-called electronic transformers, which are essentially pulsed step-down converters for powering halogen lamps rated at 12 V. Two versions of the transformers are proposed - on discrete elements and using a specialized microcircuit.

Halogen lamps are, in fact, a more advanced modification of a conventional incandescent lamp. The fundamental difference is the addition of vapors of halogen compounds to the lamp bulb, which block the active evaporation of metal from the surface of the filament during lamp operation. This allows the filament to be heated to higher temperatures, which gives higher light output and a more uniform emission spectrum. In addition, the lamp life is increased. These and other features make the halogen lamp very attractive for home lighting, and not only. A wide range of halogen lamps of various wattages for voltages of 230 and 12 V are commercially produced. Lamps with a supply voltage of 12 V have better technical characteristics and a longer service life compared to 230 V lamps, not to mention electrical safety. To power such lamps from a 230 V network, it is necessary to reduce the voltage. You can, of course, use a regular network step-down transformer, but this is expensive and impractical. The optimal solution is to use a 230 V/12 V step-down converter, often called an electronic transformer or halogen converter in such cases. Two versions of such devices will be discussed in this article, both are designed for a load power of 20...105 W.

One of the simplest and most common circuit solutions for step-down electronic transformers is a half-bridge converter with positive current feedback, the circuit of which is shown in Fig. 1. When the device is connected to the network, capacitors C3 and C4 are quickly charged to the amplitude voltage of the network, forming half the voltage at the connection point. Circuit R5C2VS1 generates a trigger pulse. As soon as the voltage on capacitor C2 reaches the opening threshold of dinistor VS1 (24.32 V), it will open and a forward bias voltage will be applied to the base of transistor VT2. This transistor will open and current will flow through the circuit: the common point of capacitors C3 and C4, the primary winding of transformer T2, winding III of transformer T1, the collector-emitter section of transistor VT2, the negative terminal of the diode bridge VD1. A voltage will appear on winding II of transformer T1 that maintains transistor VT2 in the open state, while reverse voltage from winding I will be applied to the base of transistor VT1 (windings I and II are switched out of phase). The current flowing through winding III of transformer T1 will quickly introduce it into a saturation state. As a result, the voltage on windings I and II T1 will tend to zero. Transistor VT2 will begin to close. When it closes almost completely, the transformer will begin to come out of saturation.

Rice. 1. Circuit of a half-bridge converter with positive current feedback

Closing transistor VT2 and leaving transformer T1 from saturation will lead to a change in the direction of the EMF and an increase in voltage on windings I and II. Now a forward voltage will be applied to the base of transistor VT1, and a reverse voltage will be applied to the base of VT2. Transistor VT1 will begin to open. Current will flow through the circuit: positive terminal of the diode bridge VD1, collector-emitter section VT1, winding III T1, primary winding of transformer T2, common point of capacitors C3 and C4. Then the process is repeated, and a second half-wave of voltage is formed in the load. After startup, diode VD4 maintains capacitor C2 in a discharged state. Since the converter does not use a smoothing oxide capacitor (it is not necessary when working with an incandescent lamp; on the contrary, its presence worsens the power factor of the device), then at the end of the half-cycle of the rectified mains voltage, generation will stop. With the arrival of the next half cycle, the generator will start again. As a result of the operation of the electronic transformer, oscillations with a frequency of 30...35 kHz (Fig. 2), which are close in shape to sinusoidal, are formed at its output, followed by bursts with a frequency of 100 Hz (Fig. 3).

Rice. 2. Oscillations close in shape to sinusoidal with a frequency of 30...35 kHz

Rice. 3. Oscillations with a frequency of 100 Hz

An important feature of such a converter is that it will not start without load, since in this case the current through winding III T1 will be too small, and the transformer will not enter saturation, the self-generation process will fail. This feature makes idle protection unnecessary. A device with those shown in Fig. 1 nominal starts stably at a load power of 20 W.

In Fig. Figure 4 shows a diagram of an improved electronic transformer, to which a noise suppression filter and a load short circuit protection unit have been added. The protection unit is assembled on transistor VT3, diode VD6, zener diode VD7, capacitor C8 and resistors R7-R12. A sharp increase in load current will lead to an increase in the voltage on windings I and II of transformer T1 from 3...5 V in nominal mode to 9...10 V in short circuit mode. As a result, a bias voltage of 0.6 V will appear at the base of transistor VT3. The transistor will open and bypass the start circuit capacitor C6. As a result, the generator will not start with the next half-cycle of the rectified voltage. Capacitor C8 provides a protection shutdown delay of about 0.5 s.

Rice. 4. Scheme of an improved electronic transformer

The second version of the electronic step-down transformer is shown in Fig. 5. It is easier to repeat, since it does not have one transformer, but it is more functional. This is also a half-bridge converter, but controlled by a specialized IR2161S microcircuit. The microcircuit has all the necessary protective functions built in: against low and high mains voltage, against idle mode and short circuit in the load, and against overheating. The IR2161S also has a soft start function, which consists of a smooth increase in the output voltage when turned on from 0 to 11.8 V within 1 s. This eliminates a sudden surge of current through the cold filament of the lamp, which significantly, sometimes several times, increases its service life.

Rice. 5. Second version of the electronic step-down transformer

At the first moment, as well as with the arrival of each subsequent half-cycle of the rectified voltage, the microcircuit is powered through the diode VD3 from the parametric stabilizer on the zener diode VD2. If the power is supplied directly from a 230 V network without using a phase power regulator (dimmer), then the R1-R3C5 circuit is not needed. After entering the operating mode, the microcircuit is additionally powered from the output of the half-bridge through the d2VD4VD5 circuit. Immediately after startup, the frequency of the internal clock generator of the microcircuit is about 125 kHz, which is significantly higher than the frequency of the output circuit S13S14T1, as a result, the voltage on the secondary winding of transformer T1 will be low. The internal oscillator of the microcircuit is controlled by voltage, its frequency is inversely proportional to the voltage on capacitor C8. Immediately after switching on, this capacitor begins to charge from the internal current source of the microcircuit. In proportion to the increase in voltage across it, the frequency of the microcircuit generator will decrease. When the voltage on the capacitor reaches 5 V (approximately 1 s after switching on), the frequency will decrease to an operating value of about 35 kHz, and the voltage at the output of the transformer will reach the nominal value of 11.8 V. This is how a soft start is implemented, after its completion the DA1 chip goes into operating mode in which pin 3 of DA1 can be used to control output power. If you connect a variable resistor with a resistance of 100 kOhm in parallel with capacitor C8, you can, by changing the voltage at pin 3 of DA1, control the output voltage and adjust the brightness of the lamp. When the voltage at pin 3 of the DA1 chip changes from 0 to 5 V, the generation frequency will change from 60 to 30 kHz (60 kHz at 0 V is the minimum output voltage and 30 kHz at 5 V is the maximum).

The CS input (pin 4) of the DA1 chip is the input of the internal error signal amplifier and is used to control the load current and voltage at the half-bridge output. In the event of a sharp increase in load current, for example, during a short circuit, the voltage drop across the current sensor - resistors R12 and R13, and therefore at pin 4 of DA1 will exceed 0.56 V, the internal comparator will switch and stop the clock generator. In the event of a load break, the voltage at the output of the half-bridge may exceed the maximum permissible voltage of transistors VT1 and VT2. To avoid this, a resistive-capacitive divider C10R9 is connected to the CS input via diode VD7. When the voltage threshold across resistor R9 is exceeded, generation also stops. The operating modes of the IR2161S chip are discussed in more detail in.

You can calculate the number of turns of the output transformer windings for both options, for example, using a simple calculation method; you can select the appropriate magnetic core based on overall power using the catalog.

According to, the number of turns of the primary winding is equal to

NI = (Uc max t0 max) / (2 S Bmax),

where Uc max is the maximum network voltage, V; t0 max - maximum time of the open state of transistors, μs; S - cross-sectional area of the magnetic circuit, mm2; Bmax - maximum induction, T.

Number of turns of the secondary winding

where k is the transformation coefficient, in our case we can take k = 10.

A drawing of the printed circuit board of the first version of the electronic transformer (see Fig. 4) is shown in Fig. 6, arrangement of elements - in Fig. 7. The appearance of the assembled board is shown in Fig. 8. covers. The electronic transformer is assembled on a board made of fiberglass foil on one side with a thickness of 1.5 mm. All surface-mount elements are installed on the side of the printed conductors, and lead-out elements are installed on the opposite side of the board. Most of the parts (transistors VT1, VT2, transformer T1, dinistor VS1, capacitors C1-C5, C9, C10) are suitable from mass-produced cheap electronic ballasts for T8 type fluorescent lamps, for example, Tridonic PC4x18 T8, Fintar 236/418, Cimex CSVT 418P, Komtex EFBL236/418, TDM Electric EB-T8-236/418, etc., since they have similar circuitry and element base. Capacitors C9 and C10 are polypropylene metal film, designed for high pulse current and alternating voltage of at least 400 V. Diode VD4 - any fast-acting diode with an acceptable reverse voltage in Fig. 11 of at least 150 V.

Rice. 6. Printed circuit board drawing of the first version of the electronic transformer

Rice. 7. Arrangement of elements on the board

Rice. 8. Appearance of the assembled board

Transformer T1 is wound on a ring magnetic core with a magnetic permeability of 2300 ± 15%, its outer diameter is 10.2 mm, its inner diameter is 5.6 mm, and its thickness is 5.3 mm. Winding III (5-6) contains one turn, windings I (1-2) and II (3-4) contain three turns of wire with a diameter of 0.3 mm. The inductance of windings 1-2 and 3-4 should be 10...15 μH. The output transformer T2 is wound on a magnetic core EV25/13/13 (Epcos) without a non-magnetic gap, material N27. Its primary winding contains 76 turns of 5x0.2 mm wire. The secondary winding contains eight turns of Litz wire 100x0.08 mm. The inductance of the primary winding is 12 ±10% mH. The noise suppression filter choke L1 is wound on a magnetic core E19/8/5, material N30, each winding contains 130 turns of wire with a diameter of 0.25 mm. You can use a standard two-winding inductor with an inductance of 30...40 mH that is suitable in size. It is advisable to use X-class capacitors C1, C2.

The printed circuit board drawing of the second version of the electronic transformer (see Fig. 5) is shown in Fig. 9, arrangement of elements - in Fig. 10. The board is also made of fiberglass foil on one side, surface-mount elements are located on the side of the printed conductors, and lead-out elements are on the opposite side. The appearance of the finished device is shown in Fig. 11 and fig. 12. Output transformer T1 is wound on a ring magnetic core R29.5 (Epcos), material N87. The primary winding contains 81 turns of wire with a diameter of 0.6 mm, the secondary winding contains 8 turns of wire 3x1 mm. The inductance of the primary winding is 18 ± 10% mH, the secondary winding is 200 ± 10% μH. Transformer T1 was designed for a maximum power of up to 150 W; to connect such a load, transistors VT1 and VT2 must be installed on a heat sink - an aluminum plate with an area of 16...18 mm2, a thickness of 1.5...2 mm. In this case, however, a corresponding modification of the printed circuit board will be required. Also, the output transformer can be used from the first version of the device (you will need to add holes on the board for a different pin arrangement). Transistors STD10NM60N (VT1, VT2) can be replaced with IRF740AS or similar. Zener diode VD2 must have a power of at least 1 W, stabilization voltage - 15.6...18 V. Capacitor C12 - preferably a ceramic disk with a rated direct voltage of 1000 V. Capacitors C13, C14 - metal film polypropylene, designed for high pulsed current and alternating current voltage is at least 400 V. Each of the resistive circuits R4-R7, R14-R17, R18-R21 can be replaced with one output resistor of the appropriate resistance and power, but this will require changing the printed circuit board.

Rice. 9. Printed circuit board drawing of the second version of the electronic transformer

Rice. 10. Arrangement of elements on the board

Rice. 11. Appearance of the finished device

Rice. 12. Appearance of the assembled board

Literature

1. IR2161 (S) & (PbF). Halogen converter control IC. - URL: http://www.irf.com/product-info/datasheets/data/ir2161.pdf (04/24/15).

2. Peter Green. 100VA dimmable electronic converter for low voltage lighting. - URL: http:// www.irf.com/technical-info/refdesigns/irplhalo1e.pdf (04/24/15).

3. Ferrites and Accessories. - URL: http:// en.tdk.eu/tdk-en/1 80386/tech-library/epcos-publications/ferrites (04/24/15).

Date of publication: 10/30/2015

Readers' opinions

Veselin / 08.11.2017 - 22:18 Which electronic transformers are on the market with it 2161 or similar
Eduard / 12/26/2016 - 13:07 Hello, is it possible to install a 180W instead of a 160W transformer? Thank you.
Mikhail / 12/21/2016 - 22:44 I remade these http://ali.pub/7w6tj
Yuri / 08/05/2016 - 17:57 Hello! Is it possible to find out the frequency of the alternating voltage at the output of the transformer for halogen lamps? Thank you.

You can leave your comment, opinion or question on the above material:

www.radioradar.net

Today, electromechanics rarely repair electronic transformers. In most cases, I myself don’t really bother with working on resuscitating such devices, simply because, usually, buying a new electronic transformer is much cheaper than repairing an old one. However, in the opposite situation, why not work hard to save money. In addition, not everyone has the opportunity to get to a specialized store to find a replacement there, or go to a workshop. For this reason, any radio amateur needs to be able to and know how to check and repair pulse (electronic) transformers at home, what ambiguous issues may arise and how to resolve them.

Due to the fact that not everyone has an extensive amount of knowledge on the topic, I will try to present all available information as accessible as possible.

A little about transformers

Fig.1: Transformer.

Before proceeding to the main part, I will give a short reminder about what an electronic transformer is and what it is intended for. A transformer is used to convert one variable voltage to another (for example, 220 volts to 12 volts). This property of an electronic transformer is very widely used in radio electronics. There are single-phase (current flows through two wires - phase and “0”) and three-phase (current flows through four wires - three phases and “0”) transformers. The main significant point when using an electronic transformer is that as the voltage decreases, the current in the transformer increases.

A transformer has at least one primary and one secondary winding. The supply voltage is connected to the primary winding, a load is connected to the secondary winding, or the output voltage is removed. In step-down transformers, the primary winding wire always has a smaller cross-section than the secondary wire. This allows you to increase the number of turns of the primary winding and, as a result, its resistance. That is, when checked with a multimeter, the primary winding shows a resistance many times greater than the secondary. If for some reason the diameter of the secondary winding wire is small, then, according to the Joule-Lance law, the secondary winding will overheat and burn the entire transformer. A transformer malfunction may consist of a break or short circuit (short circuit) of the windings. If there is a break, the multimeter shows one on the resistance.

How to test electronic transformers?

In fact, to figure out the cause of the breakdown, you don’t need to have a huge amount of knowledge; it’s enough to have a multimeter on hand (standard Chinese, as in Figure 2) and know what numbers each component (capacitor, diode, etc.) should produce at the output. d.).

Figure 2: Multimeter.

The multimeter can measure DC, AC voltage and resistance. It can also work in dialing mode. It is advisable that the multimeter probe be wrapped with tape (as in Figure No. 2), this will protect it from breaks.

In order to correctly test the various elements of the transformer, I recommend desoldering them (many try to do without this) and examining them separately, since otherwise the readings may be inaccurate.

Diodes

We must not forget that diodes only ring in one direction. To do this, set the multimeter to continuity mode, the red probe is applied to the plus, the black probe to the minus. If everything is normal, the device makes a characteristic sound. When the probes are applied to opposite poles, nothing should happen at all, and if this is not the case, then a breakdown of the diode can be diagnosed.

Transistors

When checking transistors, they also need to be unsoldered and the base-emitter, base-collector junctions must be wired, identifying their permeability in one direction and the other. Typically, the role of a collector in a transistor is performed by the rear iron part.

Winding

We must not forget to check the winding, both primary and secondary. If you have problems determining where the primary winding is and where the secondary winding is, then remember that the primary winding gives more resistance.

Capacitors (radiators)

The capacitance of a capacitor is measured in farads (picofarads, microfarads). To study it, a multimeter is also used, on which the resistance is set to 2000 kOhm. The positive probe is applied to the minus of the capacitor, the negative to the plus. Increasing numbers should appear on the screen up to almost two thousand, which are replaced by one, which stands for infinite resistance. This may indicate the health of the capacitor, but only in relation to its ability to accumulate charge.

One more point: if during the dialing process there is confusion about where the “input” is located and where the “output” of the transformer is located, then you just need to turn the board over and on the back side at one end of the board you will see a small marking “SEC” (second), which indicates the output, and on the other “PRI” (first) the input.

And also, do not forget that electronic transformers cannot be started without loading! It is very important.

Electronic transformer repair

Example 1

The opportunity to practice repairing a transformer presented itself not so long ago, when they brought me an electronic transformer from a ceiling chandelier (voltage - 12 volts). The chandelier is designed for 9 bulbs, each 20 watts (180 watts in total). On the packaging of the transformer it also said: 180 watts. But the mark on the board said: 160 watts. The country of origin is, of course, China. A similar electronic transformer costs no more than $3, and this is actually quite a bit when compared with the cost of the other components of the device in which it was used.

In the electronic transformer I received, a pair of switches on bipolar transistors burned out (model: 13009).

The operating circuit is a standard push-pull, in place of the output transistor is a TOP inverter, whose secondary winding consists of 6 turns, and the alternating current is immediately redirected to the output, that is, to the lamps.

Such power supplies have a very significant drawback: there is no protection against short circuit at the output. Even with a short-circuit of the output winding, you can expect a very impressive explosion of the circuit. Therefore, it is highly not recommended to take risks in this way and short-circuit the secondary winding. In general, it is for this reason that radio amateurs do not really like to mess with electronic transformers of this type. However, some, on the contrary, try to modify them on their own, which, in my opinion, is quite good.

But let's get back to the point: since there was a darkening of the board right under the keys, there was no doubt that they failed precisely because of overheating. Moreover, the radiators do not actively cool the case box filled with many parts, and they are also covered with cardboard. Although, judging by the initial data, there was also an overload of 20 watts.

Due to the fact that the load exceeds the capabilities of the power supply, reaching the rated power is almost equivalent to failure. Moreover, ideally, with a view to long-term operation, the power of the power supply should be not less, but twice as much as necessary. This is what Chinese electronics is like. It was not possible to reduce the load level by removing several light bulbs. Therefore, the only suitable option, in my opinion, to correct the situation was to increase the heat sinks.

To confirm (or refute) my version, I launched the board directly on the table and applied the load using two halogen pair lamps. When everything was connected, I dripped a little paraffin onto the radiators. The calculation was as follows: if the paraffin melts and evaporates, then we can guarantee that the electronic transformer (fortunately, if only it is itself) will burn out in less than half an hour of operation due to overheating. After 5 minutes of operation, the wax did not melt, it turned out that the main problem is related precisely to poor ventilation, and not to a malfunction of the radiator. The most elegant solution to the problem is to simply fit another larger housing under the electronic transformer, which will provide sufficient ventilation. But I preferred to connect a heat sink in the form of an aluminum strip. Actually, this turned out to be quite enough to correct the situation.

Example 2

As another example of repairing an electronic transformer, I would like to talk about repairing a device that reduces the voltage from 220 to 12 Volts. It was used for 12 Volt halogen lamps (power - 50 Watt).

The copy in question stopped working without any special effects. Before I got it into my hands, several craftsmen refused to work with it: some could not find a solution to the problem, others, as mentioned above, decided that it was not economically feasible.

To clear my conscience, I checked all the elements and traces on the board and found no breaks anywhere.

Then I decided to check the capacitors. The diagnostics with a multimeter seemed to be successful, however, taking into account the fact that the charge accumulated for as long as 10 seconds (this is a lot for capacitors of this type), a suspicion arose that the problem was in it. I replaced the capacitor with a new one.

A small digression is needed here: on the body of the electronic transformer in question there was a designation: 35-105 VA. These readings indicate at what load the device can be turned on. It is impossible to turn it on without a load at all (or, in human terms, without a lamp), as mentioned earlier. Therefore, I connected a 50-watt lamp to the electronic transformer (that is, a value that fits between the lower and upper limits of the permissible load).

Rice. 4: 50W halogen lamp (package).

After connection, no changes occurred in the performance of the transformer. Then I completely examined the design again and realized that during the first check I did not pay attention to the thermal fuse (in this case, model L33, limited to 130C). If in the continuity mode this element gives one, then we can talk about its malfunction and an open circuit. Initially, the thermal fuse was not tested for the reason that it is attached tightly to the transistor using heat shrink. That is, to fully check the element, you will have to get rid of the heat shrinkage, and this is very labor-intensive.

Fig. 5: Thermal fuse attached by heat shrink to the transistor (the white element pointed to by the handle).

However, to analyze the operation of the circuit without this element, it is enough to short-circuit its “legs” on the reverse side. Which is what I did. The electronic transformer immediately started working, and the earlier replacement of the capacitor turned out to be not superfluous, since the capacity of the previously installed element did not meet the declared one. The reason was probably that it was simply worn out.

As a result, I replaced the thermal fuse, and at this point the repair of the electronic transformer could be considered complete.

Write comments, additions to the article, maybe I missed something. Take a look at, I will be glad if you find anything else useful on mine.

After rummaging around on the Internet and reading more than one article and discussion on the forum, I stopped and started disassembling the power supply. I must admit, the Chinese manufacturer Taschibra released an extremely high-quality product, the circuit diagram of which I borrowed from the site stoom.ru. The circuit is presented for a 105 W model, but believe me, differences in power do not change the structure of the circuit, but only its elements depending on the output power:

The circuit after the modification will look like this:

Now in more detail about the improvements:

After the rectifier bridge, we turn on the capacitor to smooth out the ripples of the rectified voltage. The capacitance is selected at the rate of 1 µF per 1 W. Thus, for a power of 150 W, I must install a 150 uF capacitor for an operating voltage of at least 400V. Since the size of the capacitor does not allow it to be placed inside the metal case of the Taschibra, I take it out through the wires.
When connected to the network, an inrush of current occurs due to the added capacitor, so you need to connect an NTC thermistor or a 4.7 Ohm 5W resistor to the break in one of the network wires. This will limit the starting current. My circuit already had such a resistor, but after that I additionally installed MF72-5D9, which I removed from an unnecessary computer power supply.

Not shown in the diagram, but from a Computer power supply you can use a filter assembled on capacitors and coils; in some power supplies it is assembled on a separate small board soldered to the mains power socket.

If a different output voltage is required, the secondary winding of the power transformer will have to be rewinded. The diameter of the wire (harness of wires) is selected based on the load current: d=0.6*root(Inom). My unit used a transformer wound with wire with a cross-section of 0.7 mm²; I personally did not count the number of turns, since I did not rewind the winding. I unsoldered the transformer from the board, unwound the twisted wires of the secondary winding of the transformer, there were 10 ends in total on each side:

I connected the ends of the resulting three windings together in series into 3 parallel wires, since the cross-section of the wire is the same 0.7 mm2 as the wire in the transformer winding. Unfortunately, the resulting 2 jumpers are not visible in the photo.

Simple mathematics, a 150 W winding was wound with a 0.7 mm2 wire, which we managed to split into 10 separate ends, ringing the ends, divided into 3 windings each with 3+3+4 cores, turn them on in series, in theory you should get 12+12+12= 36 Volt.

Let's calculate the current I=P/U=150/36=4.17A
Minimum winding cross-section 3*0.7mm² =2.1mm²
Let's check whether the winding can withstand this current d=0.6*root(Inom)=0.6*root(4.17A)=1.22mm²< 2.1мм²

It turns out that the winding in our transformer is suitable with a large margin. Let me run a little ahead of the voltage that the AC power supply supplied at 32 Volts.
Continuing the redesign of the Taschibra power supply:
Since the switching power supply has current feedback, the output voltage varies depending on the load. When there is no load, the transformer does not start, which is very convenient if used for its intended purpose, but our goal is a constant voltage power supply. To do this, we change the current feedback circuit to voltage feedback.

We remove the current feedback winding and replace it with a jumper on the board. This can be clearly seen in the photo above. Then we pass a flexible stranded wire (I used a wire from a computer power supply) through a power transformer in 2 turns, then we pass the wire through a feedback transformer and make one turn so that the ends do not unwind, additionally pull it through PVC as shown in the photo above. The ends of the wire passed through the power transformer and the feedback transformer are connected through a 3.4 Ohm 10 W resistor. Unfortunately, I did not find a resistor with the required value and installed 4.7 Ohm 10 W. This resistor sets the conversion frequency (approximately 30 kHz). As the load current increases, the frequency becomes higher.

If the converter does not start, you need to change the winding direction, it is easier to change it on a small feedback transformer.

As I searched for my solution to the conversion, a lot of information has accumulated on Taschibra switching power supplies, I propose to discuss them here.
Differences between similar modifications from other sites:

Current-limiting resistor 6.8 Ohm MLT-1 (it’s strange that the 1 W resistor did not heat up or the author missed this point)
Current limiting resistor 5-10 W on the radiator, in my case 10 W without heating.
Eliminate filter capacitor and high side inrush current limiter

Taschibra power supplies have been tested for:

Laboratory Power Supplies
Power amplifier for computer speakers (2*8 W)
Tape recorders
Lighting
Electric tools

To power DC consumers, it is necessary to have a diode bridge and a filter capacitor at the output of the power transformer; the diodes used for this bridge must be high-frequency and correspond to the power ratings of the Taschibra power supply. I advise you to use diodes from a computer power supply or similar ones.

We won’t go into the basics of how the circuit works, but let’s get down to business right away.
We will try to refine and increase the power of the Chinese Taschibra electric vehicle by 105 watts.

Improvement No. 1

The essence of the idea is to add short-circuit protection and also eliminate the above-mentioned drawback (activation of a circuit without an output load or with a low-power load).

The feedback transformer consists of three separate windings. Two of these windings power the base switch circuits.

First, remove the communication winding on the OS transformer and install a jumper. This winding is connected in series with the primary winding of the pulse transformer.
Then we wind only 2 turns on the power transformer and one turn on the ring (OS transformer). For winding, you can use a wire with a diameter of 0.4-0.8 mm.

Next, you need to select a resistor for the OS, in my case it is 6.2 ohms, but a resistor can be selected with a resistance of 3-12 ohms, the higher the resistance of this resistor, the lower the short-circuit protection current. In my case, the resistor is a wirewound one, which I do not recommend doing. We select the power of this resistor to be 3-5 watts (you can use from 1 to 10 watts).

The circuit will now start without load; in a word, we have a full-fledged UPS with short-circuit protection.

Improvement No. 2

Improvement No. 3

Now about the main thing - increasing the power of the electronic transformer and is it real? In fact, there is only one reliable way to power it up without much modification.

For powering up, it is convenient to use an ET with a ring transformer, since it will be necessary to rewind the secondary winding; it is for this reason that we will replace our transformer.

It is planned to increase the power to 200 watts. That is why an electrolyte with a reserve, which was mentioned above, was needed.

We replace the half-bridge capacitors with 0.5 μF; in the standard circuit they have a capacity of 0.22 μF. Bipolar keys MJE13007 are replaced with MJE13009.
The power winding of the transformer contains 8 turns, the winding was done with 5 strands of 0.7 mm wire, so we have a wire in the primary with a total cross-section of 3.5 mm.

All components except the generator board are mounted on a breadboard. The keys were secured to the heat sink through insulating gaskets.

We continue our modification of the electronic transformer, adding a rectifier and filter to the circuit.
The chokes are wound on rings made of powdered iron (removed from a computer power supply unit) and consist of 5-8 turns. It is convenient to wind it using 5 strands of wire with a diameter of 0.4-0.6 mm each.

Voltage regulator

Protection

List of radioelements

Experiments with the electronic transformer Taschibra (Tashibra, Tashibra). Electronic transformers circuits

Experiments with electronic transformer Taschibra (Tashibra, Tashibra)

ET scheme Taschibra (Tashibra, Tashibra)

Are we redoing it? Certainly!

First start

Improvement of Tasсhibra - a capacitor in the PIC instead of a resistor!

Electronic transformers. Device and operation. Peculiarities

Device and principle of operation

Scheme of work

Model of a transformer from the Chinese manufacturer Taschibra

With a stable load, such as halogen lamps, such electronic transformers can operate indefinitely. During operation, the circuit overheats, but does not fail.

Operating principle

Power supply based on an electronic transformer

Transformer model DM-150T06A

Advantages and Benefits

Disadvantages of electronic transformers

Power of electronic transformers

Electronic transformer circuit for 12V halogen lamps. How does an electronic transformer work?

Model diagram

How to do it yourself?

Devices with capacitor resistor

Transformers with regulator

Using wire stabilizers

Models with diode bridge

Model Taschibra

Device RET251C

Transformer GET 03

Device ELTR-70

Model ELTR-60

Transformers TRA110

Electronic transformer conversion | all-he

ELECTRONIC TRANSFORMER DIAGRAM FOR HALOGEN LAMPS

Electronic transformers for 12 V halogen lamps

A little about transformers

How to test electronic transformers?

Diodes

Transistors

Winding

Capacitors (radiators)

Electronic transformer repair

Example 1

Example 2

Read also