Every time I read new blog posts I come across the same error - they put current stabilizer where you need it Voltage regulator and vice versa. I’ll try to explain it in layman’s terms, without delving into the jungle of terms and formulas. It will be especially useful for those who bet driver for powerful LEDs and feeds with it many poor people. There is a separate paragraph for you at the end of the article.

First, let's understand the concepts:

VOLTAGE REGULATOR
Based on the name, it stabilizes voltage. If it is written that the stabilizer is 12V and 3A, then it means it stabilizes at a voltage of 12V! But 3A is the maximum current that the stabilizer can deliver. Maximum! And not “always delivers 3 amps.” That is, it can give out 3 milliamps, and 1 ampere, and two... As much as your circuit eats, it gives out as much. But no more than three. Actually this is the main thing.

Once upon a time they were like this and they connected TVs to them...

And now I will move on to describing the types of voltage stabilizers:

Linear stabilizers (the same KREN or LM7805/LM7809/LM7812, etc.)

Here it is - LM7812. Our Soviet analogue - KREN8B

The most common type. They cannot operate at a voltage lower than that indicated on its belly. That is, if the LM7812 stabilizes the voltage at 12 volts, then it needs to be supplied at least about one and a half volts more to the input. If it is less, it means that the output of the stabilizer will be less than 12 volts. He can't take the missing volts out of nowhere. That’s why it’s a bad idea to stabilize the voltage in a car with 12-volt Cranks. As soon as the input is less than 13.5 volts, it starts giving less than 12 volts at the output.

Another disadvantage of linear stabilizers- strong heating under such a good load. That is, in village language - everything above the same 12 volts turns into heat. And the higher the input voltage, the more heat. Up to the temperature of frying scrambled eggs. We loaded it a little more than a couple of small LEDs and that’s it - we got an excellent iron.

Switching stabilizers - much cooler, but also more expensive. Usually for the average buyer it already looks like some kind of scarf with details.

For example, this scarf is a pulse voltage stabilizer.

There are three types: step-down, step-up and omnivorous. The coolest ones are omnivores. They don't care if the input voltage is lower or higher than required. It automatically switches to the mode of increasing or decreasing the voltage and maintains the set output. And if it is written that the input can be from 1 to 30 volts and the output will be stable at 12, then so it will be.

But more expensive. But cooler. But more expensive...
If you don’t want an iron made from a linear stabilizer and a huge cooling radiator into the bargain, use a pulse one.
What is the conclusion about voltage stabilizers?
THE VOLTS HAVE BEEN SET HARD - but the current can float as desired(within certain limits of course)

CURRENT STABILIZER
When applied to LEDs, they are also called “LED driver”. Which will also be true.

Here, for example, is a ready-made driver. Although the driver itself is a small black eight-legged chip, the entire circuit is usually called a driver at once.

Sets the current. Stable! If it is written that the output is 350mA, then even if you crack it, it will be exactly like that. But the volts at its output can vary depending on the voltage required by the LEDs. That is, you do not regulate them, the driver will do everything for you based on the number of LEDs.
If it’s very simple, that’s the only way I can describe it. =)
And the conclusion?
SET THE CURRENT HARD - but the voltage can float.

Now - to the LEDs. After all, all the fuss is because of them.

The LED is powered by CURRENT. It does not have a VOLTAGE parameter. There is a parameter - voltage drop! That is how much is lost on it. If it is written on the LED 20mA 3.4V, then this means that it needs no more than 20 milliamps. And at the same time, 3.4 volts will be lost on it. It’s not that 3.4 volts are needed for power, but it’s simply “lost” on it!

That is, you can power it with at least 1000 volts, only if you supply it with no more than 20 mA. It will not burn out, will not overheat and will shine as it should, but after it there will be 3.4 volts less left. That's all science is. Limit the current to him - and he will be fed and will shine happily ever after.

Here we take the most common option for connecting LEDs(this is used in almost all tapes) - 3 LEDs and a resistor are connected in series. We power from 12 volts. We limit the current to the LEDs with a resistor so that they don’t burn out (I’m not writing about the calculation; there are plenty of calculators on the Internet). After the first LED, 12-3.4 = 8.6 volts remain………We have enough for now. On the second, another 3.4 volts will be lost, that is, 8.6-3.4 = 5.2 volts will remain. And there will be enough for the third LED too. And after the third there will be 5.2-3.4 = 1.8 volts. And if you want to put a fourth one, it won’t be enough. Now, if you power it not from 12V but from 15, then that’s enough. But we must take into account that the resistor will also need to be recalculated. Well, actually we came smoothly to...

The simplest current limiter is a resistor. They are often placed on the same tapes and modules. But there are disadvantages - the lower the voltage, the less current will be on the LED. And vice versa. Therefore, if the voltage in your network fluctuates like horses jumping over barriers at show jumping competitions (and this is usually the case in cars), then we first stabilize the voltage, and then limit the current with a resistor to the same 20 mA. That's all. We no longer care about power surges (the voltage stabilizer is working), and the LED is fed and shining for the joy of everyone.
That is - If we install a resistor in a car, then we need to stabilize the voltage.

It may not be possible to stabilize it if you calculate the resistor for the maximum possible voltage in the car network, you have a normal on-board network (and not a Chinese-Russian TAZ industry) and make a current reserve of at least 10%.
Well, besides, resistors can only be installed up to a certain current value. After a certain threshold, the resistors begin to heat up like hell and they have to be greatly increased in size (resistors 5W, 10W, 20W, etc.). We smoothly turn into a big iron.

There is another option- use something like LM317 as a limiter in current stabilizer mode.

LM317. Externally like LM7812. The body is the same, the meaning is somewhat different. But they also heat up, because this is also a linear regulator (remember I wrote about ROLL in the paragraph about voltage stabilizers?). And then they created...

Switching current stabilizer (or driver).

That's exactly what I'm talking about. In the picture we are talking about 1W LEDs, but with any other the picture is the same.
This is exactly what we see in Chinese modules and cornholes, which burn like matches after a week/month of operation. Because LEDs have a hellish spread, and the Chinese save more on drivers than anyone else. Why do branded modules and lamps from Osram, Philips, etc. not light up? Because they do a fairly powerful rejection of LEDs and of the entire wildest number of LEDs produced, 10-15% remain, which are almost identical in parameters and can be made into such a simple form, which is what many are trying to do - one powerful driver and many identical chains of LEDs without drivers. But in the conditions of “bought LEDs on the market and soldered them myself”, as a rule, it will not be good for them. Because even “non-Chinese” will have differences. You may be lucky and work for a long time, or maybe not.

Remember once and for all! I am begging you! =)
And it’s simple - to do it right and to do “look how I saved, and the rest are fools” - these are slightly different things. Even very different. Learn to do things not like the notorious Chinese, learn to do things beautifully and correctly. This was said a long time ago and not by me. I just tried to explain the common truths for the hundred-five-hundredth time. Sorry if I explained it crookedly =)

Here's a great illustration. Don't you think I wanted to save money and reduce the number of drivers by 3-4 times? But this is correct, which means it will work happily ever after.

And finally, for those for whom even such a presentation was too abstruse.
Remember the following and try to follow it (here a “chain” is one LED or several LEDs connected in SERIES):

1.—- EACH chain has its own current limiter (resistor or driver...)
2. - Low-power circuit up to 300mA? We put a resistor and that's enough.
3. — Is the voltage unstable? Install a VOLTAGE STABILIZER
4. — Is the current more than 300mA? We install a DRIVER (current stabilizer) on EACH chain without a voltage stabilizer.

This is how it will be right and most importantly - it will work for a long time and shine brightly! Well, I hope that all of the above will save many from mistakes and help save money and nerves.

Content:

In every electrical network, interference periodically occurs that negatively affects the standard parameters of current and. This problem is successfully solved with the help of various devices, among which current stabilizers are very popular and effective. They have various technical characteristics, which makes it possible to use them in conjunction with any household electrical appliances and equipment. Special requirements apply to measuring equipment that requires stable voltage.

General structure and principle of operation of current stabilizers

Knowledge of the basic principles of operation of current stabilizers contributes to the most effective use of these devices. Electrical networks are literally saturated with various interferences that negatively affect the operation of household appliances and electrical equipment. To overcome the negative effects, a simple voltage and current stabilizer circuit is used.

Each stabilizer has a main element - a transformer, which ensures the operation of the entire system. The simplest circuit includes a rectifier bridge connected to various types of capacitors and resistors. Their main parameters are individual capacitance and ultimate resistance.

The current stabilizer itself operates according to a very simple scheme. When current enters the transformer, its limiting frequency changes. At the input it will coincide with the frequency of the electrical network and will be 50 Hz. After all current conversions have been completed, the maximum output frequency will drop to 30 Hz. The conversion circuit involves high-voltage rectifiers, with the help of which the polarity of the voltage is determined. Capacitors are directly involved in stabilizing the current, and resistors reduce interference.

Diode current stabilizer

Many lamp designs contain diode stabilizers, better known as. Like all types of diodes, LEDs have a nonlinear current-voltage characteristic. That is, when the voltage on the LED changes, a disproportionate change in current occurs.

As the voltage increases, a very slow increase in current is initially observed, as a result, the LED does not glow. Then, when the voltage reaches a threshold value, light begins to be emitted and the current increases very quickly. A further increase in voltage leads to a catastrophic increase in current and LED burnout. The threshold voltage value is reflected in the technical characteristics of LED light sources.

High-power LEDs require the installation of a heat sink, since their operation is accompanied by the release of a large amount of heat. In addition, they require a fairly powerful current stabilizer. Correct operation of LEDs is also ensured by stabilizing devices. This is due to the strong spread of threshold voltage even for light sources of the same type. If two such LEDs are connected to the same voltage source, currents of different magnitudes will pass through them. The difference can be so significant that one of the LEDs will immediately burn out.

Thus, it is not recommended to turn on LED light sources without stabilizers. These devices set the current to a set value without taking into account the voltage applied to the circuit. The most modern devices include a two-terminal stabilizer for LEDs, used to create inexpensive solutions for controlling LEDs. It consists of a field-effect transistor, strapping parts and other radio elements.

Current stabilizer circuits for ROLL

This circuit works stably using elements such as KR142EN12 or LM317. They are adjustable voltage stabilizers that operate with current up to 1.5A and input voltage up to 40V. In normal thermal conditions, these devices are capable of dissipating power up to 10W. These chips have low self-consumption of approximately 8mA. This indicator remains unchanged even with a changing current passing through the ROLL and a changed input voltage.

The LM317 element is capable of maintaining a constant voltage across the main resistor, which is regulated within certain limits using a trimming resistor. The main resistor with a constant resistance ensures the stability of the current passing through it, so it is also known as a current-setting resistor.

The ROLL stabilizer is simple and can be used as an electronic load, battery charging and other applications.

Current stabilizer on two transistors

Due to their simple design, stabilizers with two transistors are very often used in electronic circuits. Their main disadvantage is considered to be not quite stable current in loads at varying voltages. If high current characteristics are not required, then this stabilizing device is quite suitable for solving many simple problems.

In addition to two transistors, the stabilizer circuit contains a current-setting resistor. When the current increases on one of the transistors (VT2), the voltage across the current-setting resistor increases. Under the influence of this voltage (0.5-0.6V), another transistor (VT1) begins to open. When this transistor opens, another transistor - VT2 begins to close. Accordingly, the amount of current flowing through it decreases.

A bipolar transistor is used as VT2, but if necessary, it is possible to create an adjustable current stabilizer using a MOSFET field-effect transistor used as a zener diode. Its selection is based on a voltage of 8-15 volts. This element is used when the power supply voltage is too high, under the influence of which the gate in the field-effect transistor can be broken. More powerful MOSFET zener diodes are designed for higher voltages - 20 volts or more. The opening of such zener diodes occurs at a minimum gate voltage of 2 volts. Accordingly, there is an increase in voltage, ensuring normal operation of the current stabilizer circuit.

Adjustable DC Regulator

Sometimes there is a need for current stabilizers with the ability to adjust over a wide range. Some circuits may use a current-setting resistor with reduced characteristics. In this case, it is necessary to use an error amplifier, which is based on an operational amplifier.

With the help of one current-setting resistor, the voltage in the other resistor is amplified. This condition is called enhanced error voltage. Using a reference amplifier, the parameters of the reference voltage and the error voltage are compared, after which the state of the field-effect transistor is adjusted.

This circuit requires separate power, which is supplied to a separate connector. The supply voltage must ensure normal operation of all components of the circuit and not exceed a level sufficient to cause breakdown of the field-effect transistor. Proper configuration of the circuit requires setting the variable resistor slider to the highest position. Using a trimming resistor, the maximum current value is set. Thus, the variable resistor allows the current to be adjusted from zero to the maximum value set during the setup process.

Powerful pulse current stabilizer

A wide range of supply currents and loads is not always the main requirement for stabilizers. In some cases, decisive importance is given to the high efficiency of the device. This problem is successfully solved by a pulse current stabilizer microcircuit, replacing compensation stabilizers. Devices of this type allow you to create high voltage across the load even in the presence of a low input voltage.

In addition, there is a booster. They are used together with loads whose supply voltage exceeds the input voltage of the stabilizing device. Two resistors used in the microcircuit are used as output voltage dividers, with the help of which the input and output voltage alternately decreases or increases.

Stabilizer on LM2576

Despite the wide selection of LED flashlights of various designs in stores, radio amateurs are developing their own versions of circuits for powering white super-bright LEDs. Basically, the task comes down to how to power an LED from just one battery or accumulator, and conduct practical research.

After a positive result is obtained, the circuit is disassembled, the parts are put into a box, the experiment is completed, and moral satisfaction sets in. Often research stops there, but sometimes the experience of assembling a specific unit on a breadboard turns into a real design, made according to all the rules of art. Below we consider several simple circuits developed by radio amateurs.

In some cases, it is very difficult to determine who is the author of the scheme, since the same scheme appears on different sites and in different articles. Often the authors of articles honestly write that this article was found on the Internet, but it is unknown who published this diagram for the first time. Many circuits are simply copied from the boards of the same Chinese flashlights.

Why are converters needed?

The thing is that the direct voltage drop is, as a rule, no less than 2.4...3.4V, so it is simply impossible to light an LED from one battery with a voltage of 1.5V, and even more so from a battery with a voltage of 1.2V. There are two ways out here. Either use a battery of three or more galvanic cells, or build at least the simplest one.

It is the converter that will allow you to power the flashlight with just one battery. This solution reduces the cost of power supplies, and in addition allows for fuller use: many converters are operational with a deep battery discharge of up to 0.7V! Using a converter also allows you to reduce the size of the flashlight.

The circuit is a blocking oscillator. This is one of the classic electronic circuits, so if assembled correctly and in good working order, it starts working immediately. The main thing in this circuit is to wind transformer Tr1 correctly and not to confuse the phasing of the windings.

As a core for the transformer, you can use a ferrite ring from an unusable board. It is enough to wind several turns of insulated wire and connect the windings, as shown in the figure below.

The transformer can be wound with winding wire such as PEV or PEL with a diameter of no more than 0.3 mm, which will allow you to place a slightly larger number of turns on the ring, at least 10...15, which will somewhat improve the operation of the circuit.

The windings should be wound into two wires, then connect the ends of the windings as shown in the figure. The beginning of the windings in the diagram is shown by a dot. You can use any low-power n-p-n transistor: KT315, KT503 and the like. Nowadays it is easier to find an imported transistor such as BC547.

If you don’t have an n-p-n transistor at hand, you can use, for example, KT361 or KT502. However, in this case you will have to change the polarity of the battery.

Resistor R1 is selected based on the best LED glow, although the circuit works even if it is simply replaced with a jumper. The above diagram is intended simply “for fun”, for conducting experiments. So after eight hours of continuous operation on one LED, the battery drops from 1.5V to 1.42V. We can say that it almost never discharges.

To study the load capacity of the circuit, you can try connecting several more LEDs in parallel. For example, with four LEDs the circuit continues to operate quite stably, with six LEDs the transistor begins to heat up, with eight LEDs the brightness drops noticeably and the transistor gets very hot. But the scheme still continues to work. But this is only for scientific research, since the transistor will not work for a long time in this mode.

If you plan to create a simple flashlight based on this circuit, you will have to add a couple more parts, which will ensure a brighter glow of the LED.

It is easy to see that in this circuit the LED is powered not by pulsating, but by direct current. Naturally, in this case the brightness of the glow will be slightly higher, and the level of pulsations of the emitted light will be much less. Any high-frequency diode, for example, KD521 (), will be suitable as a diode.

Converters with choke

Another simplest diagram is shown in the figure below. It is somewhat more complicated than the circuit in Figure 1, it contains 2 transistors, but instead of a transformer with two windings it only has inductor L1. Such a choke can be wound on a ring from the same energy-saving lamp, for which you will need to wind only 15 turns of winding wire with a diameter of 0.3...0.5 mm.

With the specified inductor setting on the LED, you can get a voltage of up to 3.8V (forward voltage drop across the 5730 LED is 3.4V), which is enough to power a 1W LED. Setting up the circuit involves selecting the capacitance of capacitor C1 in the range of ±50% of the maximum brightness of the LED. The circuit is operational when the supply voltage is reduced to 0.7V, which ensures maximum use of battery capacity.

If the considered circuit is supplemented with a rectifier on diode D1, a filter on capacitor C1, and a zener diode D2, you will get a low-power power supply that can be used to power op-amp circuits or other electronic components. In this case, the inductance of the inductor is selected within the range of 200...350 μH, diode D1 with a Schottky barrier, zener diode D2 is selected according to the voltage of the supplied circuit.

With a successful combination of circumstances, using such a converter you can obtain an output voltage of 7...12V. If you plan to use the converter to power only LEDs, zener diode D2 can be excluded from the circuit.

All the considered circuits are the simplest voltage sources: limiting the current through the LED is carried out in much the same way as is done in various key fobs or in lighters with LEDs.

The LED, through the power button, without any limiting resistor, is powered by 3...4 small disk batteries, the internal resistance of which limits the current through the LED to a safe level.

Current Feedback Circuits

But an LED is, after all, a current device. It is not for nothing that the documentation for LEDs indicates direct current. Therefore, true LED power circuits contain current feedback: once the current through the LED reaches a certain value, the output stage is disconnected from the power supply.

Voltage stabilizers work exactly the same way, only there is voltage feedback. Below is a circuit for powering LEDs with current feedback.

Upon closer examination, you can see that the basis of the circuit is the same blocking oscillator assembled on transistor VT2. Transistor VT1 is the control one in the feedback circuit. Feedback in this scheme works as follows.

LEDs are powered by voltage that accumulates across an electrolytic capacitor. The capacitor is charged through a diode with pulsed voltage from the collector of transistor VT2. The rectified voltage is used to power the LEDs.

The current through the LEDs passes along the following path: the positive plate of the capacitor, LEDs with limiting resistors, the current feedback resistor (sensor) Roc, the negative plate of the electrolytic capacitor.

In this case, a voltage drop Uoc=I*Roc is created across the feedback resistor, where I is the current through the LEDs. As the voltage increases (the generator, after all, works and charges the capacitor), the current through the LEDs increases, and, consequently, the voltage across the feedback resistor Roc increases.

When Uoc reaches 0.6V, transistor VT1 opens, closing the base-emitter junction of transistor VT2. Transistor VT2 closes, the blocking generator stops, and stops charging the electrolytic capacitor. Under the influence of a load, the capacitor is discharged, and the voltage across the capacitor drops.

Reducing the voltage on the capacitor leads to a decrease in the current through the LEDs, and, as a result, a decrease in the feedback voltage Uoc. Therefore, transistor VT1 closes and does not interfere with the operation of the blocking generator. The generator starts up and the whole cycle repeats again and again.

By changing the resistance of the feedback resistor, you can vary the current through the LEDs within a wide range. Such circuits are called pulse current stabilizers.

Integral current stabilizers

Currently, current stabilizers for LEDs are produced in an integrated version. Examples include specialized microcircuits ZXLD381, ZXSC300. The circuits shown below are taken from the DataSheet of these chips.

The figure shows the design of the ZXLD381 chip. It contains a PWM generator (Pulse Control), a current sensor (Rsense) and an output transistor. There are only two hanging parts. These are LED and inductor L1. A typical connection diagram is shown in the following figure. The microcircuit is produced in the SOT23 package. The generation frequency of 350KHz is set by internal capacitors; it cannot be changed. The device efficiency is 85%, starting under load is possible even with a supply voltage of 0.8V.

The forward voltage of the LED should be no more than 3.5V, as indicated in the bottom line under the figure. The current through the LED is controlled by changing the inductance of the inductor, as shown in the table on the right side of the figure. The middle column shows the peak current, the last column shows the average current through the LED. To reduce the level of ripple and increase the brightness of the glow, it is possible to use a rectifier with a filter.

Here we use an LED with a forward voltage of 3.5V, a high-frequency diode D1 with a Schottky barrier, and a capacitor C1 preferably with a low equivalent series resistance (low ESR). These requirements are necessary in order to increase the overall efficiency of the device, heating the diode and capacitor as little as possible. The output current is selected by selecting the inductance of the inductor depending on the power of the LED.

It differs from the ZXLD381 in that it does not have an internal output transistor and a current sensor resistor. This solution allows you to significantly increase the output current of the device, and therefore use a higher power LED.

An external resistor R1 is used as a current sensor, by changing the value of which you can set the required current depending on the type of LED. This resistor is calculated using the formulas given in the datasheet for the ZXSC300 chip. We will not present these formulas here; if necessary, it is easy to find a datasheet and look up the formulas from there. The output current is limited only by the parameters of the output transistor.

When you turn on all the described circuits for the first time, it is advisable to connect the battery through a 10 Ohm resistor. This will help avoid the death of the transistor if, for example, the transformer windings are incorrectly connected. If the LED lights up with this resistor, then the resistor can be removed and further adjustments can be made.

Boris Aladyshkin

All LEDs, regardless of form factor and electrical parameters, are powered by current. Correctly set current is a guarantee of long-term and stable operation of the lighting device. So why do manufacturers of LED products often install a voltage stabilizer instead of a current stabilizer? How does this affect the operation of LED lamps, strips, lanterns and spotlights? Let's try to figure it out.

Surge Protectors

Based on the name, these devices are designed to maintain the voltage in the load at a certain level. In this case, the magnitude of the output current depends on the load itself. In other words, as much load as required, it will take as much, but not more than the maximum possible value. Let's say the voltage stabilizer has the following output parameters: 12V and 1 A. That is, the output will always maintain 12V, and the current consumption can be in the range from zero to one ampere. There are two types of voltage stabilizers: linear and pulsed.

As a rule, the regulating element in the stabilizer circuit is a bipolar or field-effect transistor. If this transistor operates in active mode, then the stabilizer is called linear. If the control transistor operates in switching mode, then the stabilizer is called a pulse stabilizer.

The most common and inexpensive are linear voltage stabilizers, but they have a number of disadvantages:

• low efficiency;
• at high current loads require a heat sink;
• have a fairly high voltage drop.

To avoid such disadvantages, it is recommended to use pulse-type voltage stabilizers. They come in three types: step-up, step-down and universal. Switching stabilizers have high efficiency, do not require additional heat removal at high load currents, but have a higher cost.

Current stabilizers

The simplest current limiter is a resistor. It is often called the simplest stabilizer, which is incorrect, since the resistor is not capable of stabilizing the current when the voltage at its input fluctuates.

The use of a resistor in the LED power supply circuit is permissible only with a stabilized input voltage. Otherwise, all voltage surges are transferred to the load and negatively affect the operation of the LED. The efficiency of resistive current limiters is very low, since all the energy they consume is dissipated as heat.

The efficiency of designs based on ready-made integrated circuits (IM) of linear stabilizers is slightly higher. Circuits of linear stabilizers based on IM are distinguished by a minimal set of elements, absence of interference and simple setup.

To avoid overheating of the control element, the difference between the input and output voltages should be small but sufficient (3-5 volts). Otherwise, the chip body will be forced to dissipate unclaimed energy, thereby reducing efficiency.

Drivers for LEDs based on ready-made MI linear stabilizers are distinguished by their low cost and availability of elements for do-it-yourself assembly.

Current drivers with pulse width modulation (PWM) are considered to be the most effective. They are designed on the basis of specialized microcircuits with a feedback circuit and protection elements, which increases the reliability of the entire device several times. The presence of a pulse transformer in them leads to an increase in the cost of the circuit, but is justified by the high efficiency and service life. Current PWM stabilizers powered by a 12V source are easy to make with your own hands using a specialized microcircuit. For example, the PT4115 IC from PowTech, which is designed specifically for LED power supply circuits from 1 to 10 W.

LED Power Options

For LEDs, in addition to the rated current, there is another important parameter - forward voltage drop. The role of this parameter is also significant, which is why it is indicated in the first row of technical parameters of a semiconductor device.

In order for current to begin to flow through the p-n junction, some minimum forward voltage Umin.pr must be applied to it. The value of the minimum forward voltage is indicated in the documentation of the LED and is reflected in the graph of current-voltage characteristics (volt-ampere characteristics).

In the green section of the LED’s current-voltage characteristic it can be seen that only when Umin.pr. current Ipr begins to flow. A further slight increase in Upr leads to a sharp increase in Ipr. That is why even small voltage drops above Umax..pr. are detrimental to the LED crystal. At the moment of exceeding Umax.pr. the current reaches its peak and the crystal is destroyed. For each type of LED, there is a rated current and a corresponding voltage (nameplate data), at which the device must work out the declared service life.

Correct and incorrect inclusion

The biggest mistakes motorists make are when they try to save money on the LED lighting power supply. Often, car enthusiasts turn on LED devices directly from the battery, and then complain about various problems: blinking, loss of brightness and complete extinguishing of the crystal. All this happens due to the lack of an intermediate converter, which must compensate for voltage drops in the range from 10 to 14.5V. Another mistake car owners make is connecting only through a resistor designed for an average battery reading of 12V. A resistor is a linear element, which means that the current through it increases in proportion to the voltage. Connection through a resistor is allowed provided it is rated at 14.5V, but then you will have to come to terms with the incomplete light output of the LEDs at low and medium voltage values ​​in the on-board network. Therefore, the clear and correct way to connect LEDs in a car is to use a current stabilizer, preferably a pulse type.

In various lighting designs based on LEDs, voltage stabilizers are often used. Why is this happening? Firstly, they are much cheaper than high-quality current drivers. Secondly, in order to make a more or less reliable driver from a voltage stabilizer, it is enough to install a resistor at the output, correctly calculating its power and resistance. This circuit solution is often used in inexpensive LED lamps and lighting structures using LED strips.

Most LED strips are powered by a stable voltage of 12V. If we look at the design of the tape in more detail, we can see that it is divided into small sections. As a rule, each section consists of three SMD LEDs and one current-setting resistor. The voltage drop across one light-emitting element is on average 2.5-3.5 V, that is, a maximum of 10.5 V in total. The remainder is extinguished by a resistor, the value of which is selected by the manufacturer for the type of LEDs used. Therefore, connecting an LED through a combination of a voltage stabilizer and a resistor can be considered correct.

The output power of the stabilizer should be approximately 30% greater than the load power consumption.

If you use a simple power supply without stabilization (transformer, diode bridge and capacitor), then with a slight increase in the network voltage, its proportionally reduced part will be evenly distributed across all four elements of each section of the tape. As a result, the current and crystal temperature will increase and, as a result, the irreversible process of LED degradation will begin.

The most correct circuit design solution is to use a pulse-type current stabilizer. Today, this is the best option used by all leading manufacturers of LED products. The current driver with PWM controller practically does not heat up, is efficient and reliable.

So what should you give preference to: a cheap voltage stabilizer with a resistor or a more expensive current driver? The correct answer is hidden in the expression: “Any savings must be justified.” If you need to connect a dozen low-current LEDs or no more than one meter of strip, then choosing the first option cannot be called a mistake.

But if your goal is to power branded LEDs with a power of more than 1 W per crystal, then you cannot do without a high-quality current driver. Because the cost of such emitting diodes is much higher than the price of the driver.

Read also

To effectively overcome various interferences in the network, it is necessary to use simple current stabilizers. Modern manufacturers are engaged in the industrial production of such devices, due to which each model is distinguished by its functional and technical characteristics. In the household industry, there is no great demand for current stabilizers, but high-quality measuring equipment always needs a stable voltage.

Short description

Experienced craftsmen know very well that the simplest current limiters are presented in the form of ordinary resistors. Such units are often called stabilizers, which is not reality, since they are not able to remove all interference when the voltage fluctuates at their input. Using a resistor in the power circuit of a particular device is possible only if the entire input voltage is stabilized.

In another situation, even the smallest voltage surges are perceived as an increased load, which negatively affects the operation of the entire device. The operating efficiency of resistive current limiters is quite low, since the energy they consume is dissipated as heat.

A higher level of efficiency is achieved by those designs that are made on the basis of ready-made integrated circuits of linear stabilizers. The circuits of such devices are distinguished by a minimal set of elements, ease of configuration and lack of interference. To avoid unwanted overheating of the control element, the differences between the input and output voltages should be minimal. Otherwise, the microcircuit body will be forced to dissipate all unclaimed energy, which reduces the final efficiency indicator several times.

The most efficient circuits are those with pulse width modulation. Their production is based on the use of universal microcircuits, where there is a feedback circuit and special protective mechanisms, due to which the reliability of the entire device significantly increases. The use of a pulse transformer leads to retention of the circuit, which has a positive effect on the level of efficiency and service life. It is worth noting that craftsmen often make such stabilizers with their own hands, using special parts.

Functionality

Only a master who knows well the operating principle of a current stabilizer will be able to effectively use this device in various fields. The main difficulty is that electrical networks are saturated with various interferences that negatively affect the performance of equipment and devices. To effectively overcome sources of negative influence, specialists everywhere use voltage and current stabilizers.

Each such product contains an indispensable element - a transformer, which ensures stable and trouble-free operation of the entire system. Even the most elementary circuit is necessarily equipped with a universal rectifier bridge, which is connected to various resistors and capacitors. The main performance characteristics include the maximum level of resistance and individual capacity.

Qualified specialists note that a simple current stabilizer operates according to the most elementary circuit. The thing is that electric current flows to the main transformer, due to which its maximum frequency changes. At the input, it always coincides with this indicator in the electrical network, being within 50 hertz. Only after the current conversion has occurred will the limiting frequency be reduced to the optimal level.

It is worth noting that the traditional circuit contains powerful high-voltage rectifiers, which help determine the polarity of the voltage. But capacitors participate in high-quality current stabilization, resistors eliminate existing interference.

Making a simple converter for LEDs

Experienced craftsmen will agree that assembling a high-quality and durable stabilizer is not so difficult. The main feature is that a whole system of low-voltage capacitors of 20 volts can be installed on the block, and the pulse microcircuit can have an input of up to 35 V. The simplest DIY LED stabilizer is the LM317 version. You only need to correctly calculate the resistor for the LED used using a specialized online calculator.

An important fact remains that for the smooth operation of such a unit improvised food is great:

• Standard 19 volt unit from a laptop.
• At 24 V.
• A more powerful 32 volt unit from a conventional printer.
• Either 9 or 12 volts from some consumer electronics.

The main advantages of such a converter always include its accessibility, minimum number of elements, high degree of reliability, and availability in stores. It is very irrational to assemble a more complex circuit yourself. If the master does not have the necessary experience, then it is better to buy a pulse current stabilizer ready-made. It can always be improved if necessary.

The duration of LED operation without loss of brightness depends on the mode. The main advantage of the simplest stabilizers (drivers), such as the LM317 stabilizer chip, is that they are quite difficult to burn. The LM317 connection diagram requires only two parts: the microcircuit itself, which is included in the stabilization mode, and a resistor. The assembly process itself consists of several main stages:

1. You will need to buy a variable resistor with a resistance of 0.5 kOhm (it has three terminals and an adjustment knob). You can order it online or buy it at Radio Amateur.
2. The wires are soldered to the middle terminal, as well as to one of the extreme ones.
3. Using a multimeter turned on in resistance measurement mode, the resistance of the resistor is measured. It is necessary to achieve a maximum reading of 500 Ohms (so that the LED does not burn out when the resistor resistance is low).
4. After carefully checking the correct connections before connecting, the circuit is assembled.

For any device, a supply of 10 A can be achieved (set by low-resistance resistance). For these purposes, you can use the KT825 transistor or install an analogue with better technical characteristics and a cooling system. The maximum power of the LM317 is 1.5 amperes. If there is a need to increase the current, then a field-effect or conventional transistor can be added to the circuit.

Universal adjustable model

Many craftsmen are faced with the need to use a high-quality stabilizer that would allow network settings to be made over a wide range. Some modern circuits are distinguished by the fact that they provide for the presence of a current-setting resistor with reduced characteristics. Experts themselves note that such a device makes it possible to amplify the voltage in another resistor. This condition is commonly called enhanced error voltage.

The parameters of the reference and error voltages can be compared using a reference amplifier, thanks to which the master adjusts the state of the field-effect transistor. It is worth noting that such a circuit requires additional power, which must be supplied to a separate connector. The whole point is that the supply voltage must ensure the coordinated operation of absolutely all components of the circuit used. The permissible level should not be exceeded, as this can lead to premature equipment failure.

To configure the operation of an adjustable current stabilizer as correctly as possible, you must use a special slider. It is the trimming resistor that allows the master to set the maximum current value. Network setup is more flexible, since all parameters can be independently adjusted depending on the intensity of use.

Multifunctional device

Drivers for 220 V LEDs are of average complexity. Setting them up can take a lot of time, requiring setup experience. Such a driver can be extracted from LED lamps, spotlights and lamps with a faulty LED circuit. Most of them can also be modified by recognizing the converter controller model. The parameters are usually set by one or more resistors.

The datasheet indicates the resistance level required to obtain the desired current. If you install an adjustable resistor, the number of Amps will be adjustable (but without exceeding the specified power rating).

Until recently, the universal module XL4015 was very popular. According to its characteristics, it is suitable for connecting high power LEDs (up to 100 Watt). The standard version of its case is soldered to a board that acts as a radiator. To improve the cooling of the XL4015, the circuit must be modified to install a heatsink on the device box.

Many users simply place it on top, however, the efficiency of such an installation is quite low. It is advisable to place the cooling system at the bottom of the board, opposite the soldering joint of the microcircuit. For optimal quality, it can be unsoldered and installed on a full-fledged radiator using thermal paste. The wires will need to be extended. Additional cooling can also be installed for diodes, which will significantly increase the efficiency of the entire circuit.

Among the drivers, adjustable is considered the most universal. A variable resistor must be installed, which sets the number of amperes. These characteristics are usually specified in the following documents:

• In the accompanying documentation for the microcircuit.
• In datasheet.
• In the standard connection diagram.

Without additional cooling of the microcircuit, such devices can withstand 1-3 A (in accordance with the model of the pulse-width modulation controller). The main disadvantage of these drivers is excessive heating of the diode and inductor. Above 3 A, cooling of the powerful diode and controller will be required. The choke is replaced with a more suitable one or rewound with a thick wire.

An Essential DC Device

Even a novice master knows what this is the unit operates on the principle of double integration. In absolutely all models, converters are responsible for this process. Universal two-channel transistors are designed to increase existing dynamic characteristics. It is important to remember that to eliminate heat losses you need to use capacitors with a large capacity.

The straightening indicator can only be determined by accurately calculating the required value. As practice shows, if the DC output voltage is 12 amperes, then the limit value should be 5 V. The device will be able to stably maintain an operating frequency of 30 Hz. Regarding the threshold voltage, it all depends on the blocking of the signal that comes from the transformer. But the pulse front should not exceed 2 ISS.

Only high-quality current conversion makes it possible to ensure coordinated operation of the main transistors. In this circuit, only semiconductor diodes can be used. If the resistors are ballast, then this is fraught with large heat losses. That is why the dispersion coefficient increases significantly. The master can see that the amplitude of the oscillations has increased, but the inductive process has not occurred.

Modern scheme based on KREN

Such a device will work stably only with LM317 and KR142EN12 elements. This is due to the fact that they act as universal voltage stabilizers, coping well with currents up to 1.5 A and output voltages up to 40 volts. In classical thermal mode, these elements are capable of dissipating power up to 10 Watts. The microcircuits themselves are characterized by low self-consumption, since this figure is only 8 mA. The main thing is that this indicator remains unchanged even if the voltage fluctuates.

The LM317 microcircuit, which is capable of maintaining a constant voltage across the main resistor, deserves special attention. This unit with a constant resistance ensures maximum stability of the current passing through it, due to which it is often called a current-setting resistor. Modern stabilizers based on KREN differ from their analogues in their relative simplicity, due to which they are actively used as a charger for batteries and for electronic loads.