Several simple LED power circuits. LED flashlight with one battery. Radio engineering, electronics and DIY circuits LED flashlight on one transistor circuit

There are times in every person’s life when lighting is needed, but there is no electricity. This could be a simple power outage, or the need to repair the wiring in the house, or perhaps a forest hike or something similar.

And, of course, everyone knows that in this case, only an electric flashlight will help out - a compact and at the same time functional device. Now there are many different types of this product on the electrical engineering market. These include regular flashlights with incandescent lamps, and LED flashlights with rechargeable batteries. And there are a great many companies producing these devices - “Dick”, “Lux”, “Cosmos”, etc.

But not many people think about the principle of its operation. Meanwhile, knowing the structure and circuit of an electric flashlight, you can, if necessary, repair it or even assemble it with your own hands. Let's try to figure this out.

The simplest lanterns

Since flashlights are different, it makes sense to start with the simplest one - with a battery and an incandescent lamp, and also consider its possible malfunctions. The circuit diagram of such a device is elementary.

In fact, there is nothing in it except a battery, a power button and a light bulb. And therefore there are no special problems with it. Here are a few possible minor troubles that may result in the failure of such a flashlight:

Oxidation of any of the contacts. These could be the contacts of a switch, light bulb or battery. You just need to clean these circuit elements, and the device will work again.
Burning out of an incandescent lamp - everything is simple here; replacing the light element will solve this problem.
The batteries are completely discharged - replace the batteries with new ones (or charge them if they are rechargeable).
Lack of contact or broken wire. If the flashlight is no longer new, then it makes sense to change all the wires. This is not at all difficult to do.

LED flashlight

This type of flashlight has a more powerful luminous flux and at the same time consumes very little energy, which means that the batteries in it will last longer. It's all about the design of the light elements - LEDs do not have an incandescent filament, they do not consume energy on heating, which is why the efficiency of such devices is 80–85% higher. The role of additional equipment in the form of a converter involving a transistor, resistor and high-frequency transformer is also great.

If the flashlight has a built-in battery, then it also comes with a charger.

The circuit of such a flashlight consists of one or more LEDs, a voltage converter, a switch and a battery. In earlier flashlight models, the amount of power consumed by the LEDs had to match the amount produced by the source.

Now this problem has been solved using a voltage converter (also called a multiplier). Actually, this is the main part that contains the electrical circuit of the flashlight.

If you want to make such a device with your own hands, there will not be any special difficulties. Transistor, resistor and diodes are not a problem. The most difficult part will be winding a high-frequency transformer on a ferrite ring, which is called a blocking generator.

But this can also be dealt with by taking a similar ring from a faulty electronic ballast of an energy-saving lamp. Although, of course, if you don’t want to mess around or don’t have time, then you can find highly efficient converters on sale, such as 8115. With their help, using a transistor and a resistor, it became possible to produce an LED flashlight on a single battery.

The LED flashlight circuit itself is similar to the simplest device, and you shouldn’t dwell on it, because even a child can assemble it.

By the way, when using a voltage converter in the circuit on an old, simple flashlight, powered by a 4.5 volt square battery, which is no longer available for purchase, you can safely install a 1.5 volt battery, i.e. a regular “finger” or “little finger” one. battery. There will be no loss in luminous flux. The main task in this case is to have at least the slightest understanding of radio engineering, literally at the level of knowing what a transistor is, and also to be able to hold a soldering iron in your hands.

Refinement of Chinese lanterns

Sometimes it happens that a purchased flashlight with a battery (which appears to be of good quality) completely fails. And it is not necessarily the buyer’s fault for improper operation, although this also occurs. More often, this is a mistake when assembling a Chinese lantern in pursuit of quantity at the expense of quality.

Of course, in this case it will have to be remade, modernized somehow, because the money has been spent. Now you need to understand how to do this and whether it is possible to compete with the Chinese manufacturer and repair such a device yourself.

Considering the most common option, in which when the device is plugged in, the charging indicator lights up, but the flashlight does not charge and does not work, you can notice this.

A common mistake by the manufacturer is that the charge indicator (LED) is connected in parallel with the battery, which should never be allowed. At the same time, the buyer turns on the flashlight, and seeing that it is not lit, again supplies power to the charge. As a result, all LEDs burn out at once.

The fact is that not all manufacturers indicate that such devices cannot be charged with the LEDs turned on, since it will be impossible to repair them, all that remains is to replace them.

So, the modernization task is to connect the charge indicator in series with the battery.

As can be seen from the diagram, this problem is completely solvable.

But if the Chinese installed a 0118 resistor in their product, then the LEDs will have to be changed constantly, because the current supplied to them will be very high, and no matter what light elements are installed, they cannot withstand the load.

LED headlamp

In recent years, such a lighting device has become quite widespread. Indeed, it is very convenient when your hands are free, and the beam of light hits where the person is looking, this is precisely the main advantage of a headlamp. Previously, only miners could boast of this, and even then, to wear it, you needed a helmet, onto which the flashlight was, in fact, attached.

Nowadays, the mounting of such a device is convenient, you can wear it under any circumstances, and you don’t have a rather large and heavy battery hanging on your belt, which, moreover, must be charged once a day. The modern one is much smaller and lighter, and also has very low energy consumption.

So what is such a lantern? And the principle of its operation is no different from LED. The design options are the same - rechargeable or with removable batteries. The number of LEDs varies from 3 to 24 depending on the characteristics of the battery and converter.

In addition, such flashlights usually have 4 glow modes, not just one. These are weak, medium, strong and signal - when the LEDs blink at short intervals.

The modes of the LED headlamp are controlled by a microcontroller. Moreover, if it is available, even a strobe mode is possible. In addition, this does not harm LEDs at all, unlike incandescent lamps, since their service life does not depend on the number of on-off cycles due to the absence of an incandescent filament.

So which flashlight should you choose?

Of course, flashlights can be different in voltage consumption (from 1.5 to 12 V), and with different switches (touch or mechanical), with an audible warning about low battery. This may be the original or its analogues. And it’s not always possible to determine what kind of device is in front of your eyes. After all, until it fails and repairs begin, you cannot see what kind of microcircuit or transistor is in it. It’s probably better to choose the one you like and solve possible problems as they arise.

As a sample, let's take a rechargeable flashlight from the company "DiK", "Lux" or "Cosmos" (see photo). This pocket flashlight is small-sized, comfortable in the hand and has a fairly large reflector - 55.8 mm in diameter, the LED matrix of which has 5 white LEDs, which provides a good and large illumination spot.

In addition, the shape of the flashlight is familiar to everyone, and many from childhood, in a word - a brand. The charger is located inside the flashlight itself; you just need to remove the back cover and plug it into a power outlet. But nothing stands still and this flashlight design has also undergone changes, especially its internal filling. The latest model at the moment is DIK AN 0-005 (or DiK-5 EURO).

Earlier versions are DIK AN 0-002 and DIK AN 0-003, differing in that they contained disk batteries (3 pcs), Ni-Cd series D-025 and D-026, with a capacity of 250 mA/h, or model AN 0-003 - assembly of newer D-026D batteries with a higher capacity, 320 mAh and incandescent light bulbs of 3.5 or 2.5 V, with a current consumption of 150 and 260 mA, respectively. An LED, for comparison, consumes about 10 mA and even a matrix of 5 pieces is 50 mA.

Of course, with such characteristics, the flashlight could not shine for a long time; it lasted for a maximum of 1 hour, especially the first models.

What is it about the latest flashlight model DIK AN 0-005?

Well, firstly, there is an LED matrix of 5 LEDs, as opposed to 3 or an incandescent light bulb, which gives significantly more light with lower current consumption, and secondly, the flashlight costs only 1 1.2-inch modern Ni-MH battery -1.5 V and capacity from 1000 to 2700 mAh.

Some will ask, how can a 1.2 V AA battery “light up” the LEDs, because for them to shine brightly you need about 3.5 V? For this reason, in earlier models they placed 3 batteries in series and received 3.6 V.

But I don’t know who first came up with the idea, the Chinese or someone else, to make a voltage converter (multiplier) from 1.2 V to 3.5 V. The circuit is simple, in Chinese flashlights there are only 2 parts - a resistor and a similar radio component to a transistor marked - 8122 or 8116, or SS510, or SK5B. SS510 is a Schottky diode.

Such a flashlight shines well, brightly, and what is not unimportant - for a long time, and the charge-discharge cycles are not 150, as in previous models, but much more, which increases the service life several times. But!! In order for an LED flashlight to serve for a long time, you need to insert it into a 220 V outlet when it is turned off! If this rule is not followed, then when charging you can easily burn out the Schottky diode (SS510), and often the LEDs at the same time.

I once had to repair a DIK AN 0-005 flashlight. I don’t know exactly what caused it to fail, but I assume that they plugged it into an outlet and forgot it for several days, although according to the passport it should be charged for no more than 20 hours. In short, the battery failed, leaked, and 3 out of 5 LEDs burned out, plus the converter (diode) also stopped working.

I had a 2700 mAh AA battery, left over from an old camera, as well as LEDs, but finding the part - SS510 (Schottky diode) - turned out to be problematic. This LED flashlight is most likely of Chinese origin and such a part can probably only be bought there. And then I decided to make a voltage converter from the parts that I had, i.e. from domestic ones: transistor KT315 or KT815, high-voltage transformer and others (see diagram).

The circuit is not new, it has existed for a long time, I just used it in this flashlight. True, instead of 2 radio components, like the Chinese, I got 3, but they were free.

The electrical circuit, as you can see, is elementary; the most difficult thing is to wind the RF transformer on a ferrite ring. The ring can be used from an old switching power supply, from a computer, or from an energy-saving non-working light bulb (see photo).

The outer diameter of the ferrite ring is 10-15 mm, thickness is approximately 3-4 mm. It is necessary to wind 2 windings of 30 turns each with a wire of 0.2-0.3 mm, i.e. we first wind 30 turns, then make a tap from the middle and another 30. If you take a ferrite ring from the board of a fluorescent light bulb, it is better to use 2 pieces, folded them together. The circuit will also work on one ring, but the glow will be weaker.

I compared 2 flashlights for glow, the original (Chinese) and the one converted according to the above scheme - I saw almost no difference in brightness. By the way, the converter can be inserted not only into a rechargeable flashlight, but also into a regular one that runs on batteries, then it will be possible to power it with just 1 1.5 V battery.

The flashlight charger circuit has undergone almost no changes, with the exception of the ratings of some parts. Charging current is approximately 25 mA. When charging, the flashlight must be turned off! And do not press the switch while charging, since the charging voltage is more than 2 times higher than the battery voltage, and if it goes to the converter and is amplified, the LEDs will have to be partially or completely changed...

In principle, according to the above diagram, you can easily make an LED flashlight with your own hands, by mounting it, for example, in the body of some old, even the most ancient flashlight, or you can make the body yourself.

And in order not to change the structure of the switch of the old flashlight, which used a small 2.5-3.5 V incandescent light bulb, you need to break the already burnt out light bulb and solder 3-4 white LEDs to the base, instead of the glass bulb.

And also, for charging, install a connector under the power cord from an old printer or receiver. But, I want to draw your attention, if the flashlight body is metal, do not mount the charger there, but make it remote, i.e. separately. It is not at all difficult to remove the AA battery from the flashlight and insert it into the charger. And don’t forget to insulate everything well! Especially in places where there is a voltage of 220 V.

I think that after the conversion, the old flashlight will serve you for many more years...

Good day to all. I had a flashlight with a diode matrix of 16 LEDs lying around at home, and I wanted to remake it in the sense of improving the power circuit, especially since there was plenty to use. The matrix itself shines quite brightly, but still not as they say. I used a 1 W LED with a 60 degree collimator as a basis, and as an LED driver I took the circuit I have already given in .

Scheme number 1

As a power source I chose, of course, a SAMSUNG 18650 2600ma/h lithium battery.

For the battery discharge controller, I used a specialized controller, which is located in the battery of mobile phones - a microcircuit DW01-P with a field-effect transistor switch.

The task was to fit all this stuff in without altering the body of the flashlight, since there was very little free space, or rather none at all, except inside the threaded nut securing the original diode matrix in the body. I placed the whole thing on two printed circuit boards: on the first the battery discharge controller itself, on the second the light-emitting diode driver. The LED is soldered to an aluminum substrate and pressed against the flashlight body with the same threaded nut. Since the nut has direct thermal contact with the LED substrate and the flashlight body, which is also made of aluminum, we have an excellent heatsink.

Discuss the article LED FLASHLIGHT DIAGRAM

The availability and relatively low prices of ultra-bright light-emitting diodes (LEDs) allow them to be used in various amateur devices. Beginning radio amateurs who are using LEDs in their designs for the first time often wonder how to connect an LED to a battery? After reading this material, the reader will learn how to light an LED from almost any battery, what LED connection diagrams can be used in this or that case, how to calculate the circuit elements.

What batteries can the LED be connected to?

In principle, you can simply light the LED using any battery. Electronic circuits developed by radio amateurs and professionals make it possible to successfully cope with this task. Another thing is how long the circuit will operate continuously with a specific LED (LEDs) and a specific battery or batteries.

To estimate this time, you should know that one of the main characteristics of any battery, be it a chemical cell or a battery, is capacity. Battery capacity – C is expressed in ampere-hours. For example, the capacity of common AAA AA batteries, depending on the type and manufacturer, can range from 0.5 to 2.5 ampere-hours. In turn, light-emitting diodes are characterized by an operating current that can be tens and hundreds of milliamps. Thus, you can approximately calculate how long the battery will last using the formula:

T= (C*U baht)/(U work led *I work led)

In this formula, the numerator is the work that the battery can do, and the denominator is the power consumed by the light-emitting diode. The formula does not take into account the efficiency of the specific circuit and the fact that it is extremely problematic to fully use the entire battery capacity.

When designing battery-powered devices, they usually try to ensure that their current consumption does not exceed 10–30% of the battery capacity. Guided by this consideration and the above formula, you can estimate how many batteries of a given capacity are needed to power a particular LED.

How to connect from a AA 1.5V AA battery

Unfortunately, there is no easy way to power an LED from a single AA battery. The fact is that the operating voltage of light-emitting diodes usually exceeds 1.5 V. For this value lies in the range of 3.2 - 3.4V. Therefore, to power the LED from one battery, you will need to assemble a voltage converter. Below is a diagram of a simple voltage converter with two transistors that can be used to power 1 – 2 super-bright LEDs with an operating current of 20 milliamps.

This converter is a blocking oscillator assembled on transistor VT2, transformer T1 and resistor R1. The blocking generator produces voltage pulses that are several times higher than the voltage of the power source. Diode VD1 rectifies these pulses. Inductor L1, capacitors C2 and C3 are elements of the anti-aliasing filter.

Transistor VT1, resistor R2 and zener diode VD2 are elements of a voltage stabilizer. When the voltage across capacitor C2 exceeds 3.3 V, the zener diode opens and a voltage drop is created across resistor R2. At the same time, the first transistor will open and lock VT2, the blocking generator will stop working. This ensures stabilization of the converter output voltage at 3.3 V.

It is better to use Schottky diodes as VD1, which have a low voltage drop in the open state.

Transformer T1 can be wound on a ferrite ring of grade 2000NN. The diameter of the ring can be 7 – 15 mm. As a core, you can use rings from converters of energy-saving light bulbs, filter coils of computer power supplies, etc. The windings are made of enameled wire with a diameter of 0.3 mm, 25 turns each.

This scheme can be painlessly simplified by eliminating stabilization elements. In principle, the circuit can do without a choke and one of the capacitors C2 or C3. Even a novice radio amateur can assemble a simplified circuit with his own hands.

The circuit is also good because it will operate continuously until the power supply voltage drops to 0.8 V.

How to connect 3V batteries

You can connect a super-bright LED to a 3V battery without using any additional parts. Since the operating voltage of the LED is slightly higher than 3 V, the LED will not shine at full strength. Sometimes it can even be useful. For example, using an LED with a switch and a 3 V disk battery (popularly called a tablet), used in computer motherboards, you can make a small flashlight keychain. This miniature flashlight can be useful in different situations.

From such a battery - 3 Volt tablets you can power an LED

Using a pair of 1.5 V batteries and a purchased or homemade converter to power one or more LEDs, you can make a more serious design. The diagram of one of these converters (boosters) is shown in the figure.

The booster based on the LM3410 chip and several attachments has the following characteristics:

input voltage 2.7 – 5.5 V.
maximum output current up to 2.4 A.
number of connected LEDs from 1 to 5.
conversion frequency from 0.8 to 1.6 MHz.

The output current of the converter can be adjusted by changing the resistance of the measuring resistor R1. Despite the fact that from the technical documentation it follows that the microcircuit is designed to connect 5 LEDs, in fact you can connect 6 to it. This is due to the fact that the maximum output voltage of the chip is 24 V. The LM3410 also allows LEDs to glow (dimming) . The fourth pin of the chip (DIMM) is used for these purposes. Dimming can be done by changing the input current of this pin.

How to connect 9V Krona batteries

“Krona” has a relatively small capacity and is not very suitable for powering high-power LEDs. The maximum current of such a battery should not exceed 30 - 40 mA. Therefore, it is better to connect 3 light-emitting diodes connected in series with an operating current of 20 mA to it. They, as in the case of connecting to a 3 volt battery, will not shine at full power, but the battery will last longer.

Krona battery power supply circuit

It is difficult to cover in one material all the variety of ways to connect LEDs to batteries with different voltages and capacities. We tried to talk about the most reliable and simple designs. We hope that this material will be useful to both beginners and more experienced radio amateurs.

Principle of operation
The diagram below (" ") allows you to power a white or blue LED, requiring a supply voltage of 3 - 3.5 V, from one galvanic cell or battery NiCD,NiMH, even discharged to a voltage of 0.8 V under load.

For red and yellow LEDs, the supply voltage at a current of 20 mA is 1.8 - 2.4 V, and for blue, white and green - 3 - 3.5 V, so power the blue or white LED from a AA battery directly impossible.
The circuit represents a variant of the blocking oscillator and has been described from the city Swindon in the UK in the magazine " Everyday Practical Electronics" for November 1999. Below you can read this article:
(Click on the picture to view it in large scale)

The circuit is powered from the element LR6/AA/AAA voltage of 1.5 V - the circuit can operate continuously for a week on one battery before it discharges to 0.8 V!!! Note: AA or AAA (R6) - salt batteries, LR6 - alkaline (alkaline) batteries.

The above circuit works as a current-controlled generator. Whenever the transistor is turned off VT decaying magnetic field in a transformer winding T causes the appearance of a positive voltage pulse (up to 30 V) at the collector of the transistor. This voltage, together with the voltage of the power source (battery), is applied to the LED. Switching occurs at a very high frequency and low duty cycle. Reducing the resistance of the resistor R leads to an increase in current through the LED and, accordingly, increases the brightness of its glow.
first gives a resistance value of 10 kOhm (average current through the LED is 18 mA) and then indicates that decreasing the resistance to 2 kOhm leads to an increase in the average current to 30 mA. Also indicates that the efficiency depends on the transistor used VT- the best results are achieved by using a transistor with a low saturation voltage between the collector and emitter V CE (SAT). It indicates that for a transistor ZTX450 (V CE (SAT)= 0.25 V) efficiency is 73% when using ZTX650 (V CE (SAT) < 0,12 В) возрастает до 79 %, а при применении BC550 drops to 57%.

A similar design is mentioned in the article by M. Shustov “Low-voltage power supply of LEDs” in the magazine “Radiomir” No. 8 for 2003:

And here is the design of a Japanese amateur radio: http://elm-chan.org/works/led1/report_e.html

Modeling
To simulate such a device, you can use a freely distributed electrical circuit simulator . Here is the model of this generator:

With a supply voltage of 1.5 V and an inductance of each transformer winding of 200 μH, the power consumption from the battery is 197 mW, and 139 mW is allocated to the LED. The power loss was 58 mW, of which 55 mW in the transistor and 3 mW in the resistor. Thus, the efficiency was equal to 71%.

With a supply voltage of 1.5 V and a transistor BC547C (V CE (SAT)= 0.2 V), the dependence of the average LED current on the inductance of the transformer winding (with identical windings) is presented below:

If the winding inductance is less than 17 μH, the converter does not start.

The dependence of the average LED current on the supply voltage is given below:

Transformer
Also, instead of a self-wound transformer on a ferrite ring, you can use an industrial pulse transformer, for example,
M- small-sized, AND- impulse, T- transformer, IN- height with leads 55 mm.

MIT-4V is available in a brown or black housing.

This transformer has three windings (one primary and two secondary) with unity transformation ratio. The ohmic resistance of each winding is about 5 Ohms, the inductance is about 16 mH.
The windings contain 100 turns each, wound with PELSHO 0.1 wire on a ring K17.5x8x5 made of ferrite grade M2000NM1-B.
The designation of a ferrite ring is deciphered as follows: TO- ring; 17.5 - outer diameter of the ring, mm; 8 - inner diameter of the ring, mm; 5 - ring height, mm.
The grade of ferrite M2000NM-1B is expanded as follows: 2000 - initial magnetic permeability of ferrite; N- low frequency ferrite; M- manganese-zinc ferrite (up to 100 kHz).
The first terminal is marked with the number “1” on the transformer body, and the drawn arrow indicates the direction of reference for the remaining terminals. I used windings with pins 1-4 and 2-3.

You can also use a low-frequency matching transformer TOT:

This transformer is designed to operate at frequencies up to 10 kHz.
The designation "TOT" stands for: T- transformer; ABOUT- final; T- transistor.
The armor core of the TOT transformer is made of cold-rolled tape with high magnetic permeability and increased induction of technical saturation grade 50H.
The location of the terminals of TOT transformers resembles the pinout of vacuum tubes - there is a key and additional marking of the first terminal on the side surface of the transformer (red dot). In this case, the pins are counted clockwise from the installation side, and the first pin is located in the upper left corner.

Pinout of transformer types: A- TOT1 - TOT35; b- TOT36 - TOT189, TOL1 - TOL54; V- TOT202 - TOT219, TOL55 - TOL72

Germanium transistors
To reduce the battery threshold voltage at which the LED still glows, you can use germanium transistors, for example, the Soviet n-p-n transistor MP38A:

This transistor has a forward voltage drop across p-n transitions is about 200 mV.
To check, I assembled a prototype design using an MP38A transistor and an MIT-4V transformer:

A fairly discharged lithium battery CR2032 in this circuit it powers a chain of five LEDs. In this case, the battery voltage under load is about 1.5 volts.

Options for improving the scheme
1) You can add a capacitor connected in parallel with the resistor.

I assessed the effect of the capacitor on the efficiency of the converter by running a simulation in :

As can be seen from the graph, after a certain increase in efficiency, with a further increase in the capacitor capacitance, the efficiency of the converter begins to decrease.
2) You can also add a Schottky diode in series with the LED and connect capacitors in parallel with the LED.

3) To limit the upper limit of the load voltage, you can additionally connect a zener diode (Zener diode) in parallel with the LED.

pnp transistors
Along with on n-p-n transistors, transistors can also be used p-n-p structures. I assembled such a converter based on germanium pnp-transistor GT308V ( VT) and pulse transformer MIT-4V (coil L1- conclusions 2-3, L2- conclusions 5-6):

Resistor value R is selected experimentally (depending on the type of transistor) - it is advisable to use a 4.7 kOhm variable resistor and gradually reduce its resistance, achieving stable operation of the converter.

my converter on p-n-p transistor

I examined the operation of this converter using a digital oscilloscope. In this case, the converter was powered by a half-discharged nickel-cadmium battery, and two green LEDs connected through a germanium diode were used as a load.

load voltage

The peak voltage at the load exceeds 5 volts, which is enough to light two green LEDs even taking into account the voltage drop across the germanium diode.
The same shape of the load voltage curve is obtained when modeling the converter in the simulator :