Powerful network drivers for LEDs. How to choose an LED driver. Designation on the diagram

The standard RT4115 LED driver circuit is shown in the figure below:

The supply voltage should be at least 1.5-2 volts higher than the total voltage across the LEDs. Accordingly, in the supply voltage range from 6 to 30 volts, from 1 to 7-8 LEDs can be connected to the driver.

Maximum supply voltage of the microcircuit 45 V, but operation in this mode is not guaranteed (better pay attention to a similar microcircuit).

The current through the LEDs has a triangular shape with a maximum deviation from the average value of ±15%. The average current through the LEDs is set by a resistor and calculated by the formula:

I LED = 0.1 / R

The minimum permissible value is R = 0.082 Ohm, which corresponds to a maximum current of 1.2 A.

The deviation of the current through the LED from the calculated one does not exceed 5%, provided that resistor R is installed with a maximum deviation from the nominal value of 1%.

So, to turn on the LED at constant brightness, we leave the DIM pin hanging in the air (it is pulled up to the 5V level inside the PT4115). In this case, the output current is determined solely by resistance R.

If we connect a capacitor between the DIM pin and ground, we get the effect of smooth lighting of the LEDs. The time it takes to reach maximum brightness will depend on the capacitor capacity; the larger it is, the longer the lamp will light up.

For reference: Each nanofarad of capacitance increases the turn-on time by 0.8 ms.

If you want to make a dimmable driver for LEDs with brightness adjustment from 0 to 100%, then you can resort to one of two methods:

First way assumes that a constant voltage in the range from 0 to 6V is supplied to the DIM input. In this case, brightness adjustment from 0 to 100% is carried out at a voltage at the DIM pin from 0.5 to 2.5 volts. Increasing the voltage above 2.5 V (and up to 6 V) does not affect the current through the LEDs (the brightness does not change). On the contrary, reducing the voltage to a level of 0.3V or lower leads to the circuit turning off and putting it into standby mode (the current consumption drops to 95 μA). Thus, you can effectively control the operation of the driver without removing the supply voltage.
Second way involves supplying a signal from a pulse-width converter with an output frequency of 100-20000 Hz, the brightness will be determined by the duty cycle (pulse duty cycle). For example, if high level will remain for 1/4 of the period, and the low level, respectively, for 3/4, then this will correspond to a brightness level of 25% of the maximum. You must understand that the driver operating frequency is determined by the inductance of the inductor and in no way depends on the dimming frequency.

The PT4115 LED driver circuit with constant voltage dimmer is shown in the figure below:

This circuit for adjusting the brightness of LEDs works great due to the fact that inside the chip the DIM pin is “pulled up” to the 5V bus through a 200 kOhm resistor. Therefore, when the potentiometer slider is in its lowest position, a voltage divider of 200 + 200 kOhm is formed and a potential of 5/2 = 2.5V is formed at the DIM pin, which corresponds to 100% brightness.

How the scheme works

At the first moment of time, when the input voltage is applied, the current through R and L is zero and the output switch built into the microcircuit is open. The current through the LEDs begins to gradually increase. The rate of current rise depends on the magnitude of the inductance and supply voltage. The in-circuit comparator compares the potentials before and after resistor R and, as soon as the difference is 115 mV, a low level appears at its output, which closes the output switch.

Thanks to the energy stored in the inductance, the current through the LEDs does not disappear instantly, but begins to gradually decrease. The voltage drop across the resistor R gradually decreases. As soon as it reaches a value of 85 mV, the comparator will again issue a signal to open the output switch. And the whole cycle repeats all over again.

If it is necessary to reduce the range of current ripples through the LEDs, it is possible to connect a capacitor in parallel with the LEDs. The larger its capacity, the more the triangular shape of the current through the LEDs will be smoothed out and the more similar it will become to a sinusoidal one. The capacitor does not affect the operating frequency or efficiency of the driver, but increases the time it takes for the specified current through the LED to settle.

Important assembly details

An important element of the circuit is capacitor C1. It not only smoothes out ripples, but also compensates for the energy accumulated in the inductor at the moment the output switch is closed. Without C1, the energy stored in the inductor will flow through the Schottky diode to the power bus and can cause a breakdown of the microcircuit. Therefore, if you turn on the driver without a capacitor shunting the power supply, the microcircuit is almost guaranteed to shut down. And the greater the inductance of the inductor, the greater the chance of burning the microcontroller.

The minimum capacitance of capacitor C1 is 4.7 µF (and when the circuit is powered with a pulsating voltage after the diode bridge - at least 100 µF).

The capacitor should be located as close to the chip as possible and have the lowest possible ESR value (i.e. tantalum capacitors are welcome).

It is also very important to take a responsible approach to choosing a diode. It must have a low forward voltage drop, a short time recovery during switching and stability of parameters when increasing temperatures p-n transition to prevent an increase in leakage current.

In principle, you can take a regular diode, but Schottky diodes are best suited to these requirements. For example, STPS2H100A in SMD version (forward voltage 0.65V, reverse - 100V, pulse current up to 75A, operating temperature up to 156°C) or FR103 in DO-41 housing (reverse voltage up to 200V, current up to 30A, temperature up to 150 °C). The common SS34s performed very well, which you can pull out of old boards or buy a whole pack for 90 rubles.

The inductance of the inductor depends on the output current (see table below). An incorrectly selected inductance value can lead to an increase in the power dissipated on the microcircuit and exceeding the operating temperature limits.

If it overheats above 160°C, the microcircuit will automatically turn off and remain in the off state until it cools down to 140°C, after which it will start automatically.

Despite the available tabular data, it is permissible to install a coil with an inductance deviation greater than the nominal value. In this case, the efficiency of the entire circuit changes, but it remains operational.

You can take a factory choke, or you can make it yourself from a ferrite ring from a burnt motherboard and PEL-0.35 wire.

If maximum autonomy of the device is important (portable lamps, lanterns), then, in order to increase the efficiency of the circuit, it makes sense to spend time carefully selecting the inductor. At low currents, the inductance must be larger to minimize current control errors resulting from the delay in switching the transistor.

The inductor should be located as close as possible to the SW pin, ideally connected directly to it.

And finally, the most precision element of the LED driver circuit is resistor R. As already mentioned, it minimum value equals 0.082 Ohm, which corresponds to a current of 1.2 A.

Unfortunately, it is not always possible to find a resistor of a suitable value, so it’s time to remember the formulas for calculating the equivalent resistance when resistors are connected in series and in parallel:

R last = R 1 +R 2 +…+R n;
R pairs = (R 1 xR 2) / (R 1 +R 2).

Combining various ways switching on, you can obtain the required resistance from several resistors at hand.

It is important to route the board so that the Schottky diode current does not flow along the path between R and VIN, as this can lead to errors in measuring the load current.

The low cost, high reliability and stability of driver characteristics on the RT4115 contribute to its widespread use in LED lamps. Almost every second 12-volt LED lamp with an MR16 base is assembled on PT4115 (or CL6808).

The resistance of the current-setting resistor (in Ohms) is calculated using exactly the same formula:

R = 0.1 / I LED[A]

A typical connection diagram looks like this:

As you can see, everything is very similar to the circuit of an LED lamp with a RT4515 driver. The description of the operation, signal levels, features of the elements used and the layout of the printed circuit board are exactly the same as those, so there is no point in repeating.

CL6807 sells for 12 rubles/pcs, you just need to be careful that they don’t slip soldered ones (I recommend taking them).

SN3350

SN3350 is another inexpensive chip for LED drivers (13 rubles/piece). It is almost a complete analogue of PT4115 with the only difference being that the supply voltage can range from 6 to 40 volts, and the maximum output current is limited to 750 milliamps (continuous current should not exceed 700 mA).

Like all the microcircuits described above, the SN3350 is a pulsed step-down converter with an output current stabilization function. As usual, the current in the load (and in our case, one or more LEDs act as the load) is set by the resistance of the resistor R:

R = 0.1 / I LED

To avoid exceeding the maximum output current, resistance R should not be lower than 0.15 Ohm.

The chip is available in two packages: SOT23-5 (maximum 350 mA) and SOT89-5 (700 mA).

As usual, by applying a constant voltage to the ADJ pin, we turn the circuit into a simple adjustable driver for LEDs.

A feature of this microcircuit is a slightly different adjustment range: from 25% (0.3V) to 100% (1.2V). When the potential at the ADJ pin drops to 0.2V, the microcircuit goes into sleep mode with a consumption of around 60 µA.

Typical connection diagram:

For other details, see the specifications for the microcircuit (pdf file).

ZXLD1350

Despite the fact that this microcircuit is another clone, some differences in technical characteristics do not allow their direct replacement with each other.

Here are the main differences:

the microcircuit starts at 4.8V, but reaches normal operation only with a supply voltage of 7 to 30 Volts (up to 40V can be supplied for half a second);
maximum load current - 350 mA;
resistance of the output switch in the open state is 1.5 - 2 Ohms;
By changing the potential at the ADJ pin from 0.3 to 2.5V, you can change the output current (LED brightness) in the range from 25 to 200%. At a voltage of 0.2V for at least 100 µs, the driver goes into sleep mode with low power consumption (about 15-20 µA);
if the adjustment is carried out by a PWM signal, then at a pulse repetition rate below 500 Hz, the range of brightness changes is 1-100%. If the frequency is above 10 kHz, then from 25% to 100%;

The maximum voltage that can be applied to the ADJ input is 6V. In this case, in the range from 2.5 to 6V, the driver produces the maximum current, which is set by the current-limiting resistor. The resistor resistance is calculated in exactly the same way as in all of the above microcircuits:

R = 0.1 / I LED

The minimum resistor resistance is 0.27 Ohm.

A typical connection diagram is no different from its counterparts:

Without capacitor C1 it is IMPOSSIBLE to supply power to the circuit!!! IN best case scenario the microcircuit will overheat and produce unstable characteristics. In the worst case, it will fail instantly.

More detailed characteristics ZXLD1350 can be found in the datasheet for this chip.

The cost of the microcircuit is unreasonably high (), despite the fact that the output current is quite small. In general, it’s very much for everyone. I wouldn't get involved.

QX5241

QX5241 is a Chinese analogue of MAX16819 (MAX16820), but in a more convenient package. Also available under the names KF5241, 5241B. It is marked "5241a" (see photo).

In one well-known store they are sold almost by weight (10 pieces for 90 rubles).

The driver operates on exactly the same principle as all those described above (continuous step-down converter), but does not contain an output switch, so operation requires the connection of an external field-effect transistor.

You can take any N-channel MOSFET with suitable drain current and drain-source voltage. For example, the following are suitable: SQ2310ES (up to 20V!!!), 40N06, IRF7413, IPD090N03L, IRF7201. In general, the lower the opening voltage, the better.

Here are some key features of the LED driver on the QX5241:

maximum output current - 2.5 A;
Efficiency up to 96%;
maximum dimming frequency - 5 kHz;
maximum operating frequency of the converter is 1 MHz;
accuracy of current stabilization through LEDs - 1%;
supply voltage - 5.5 - 36 Volts (works normally at 38!);
output current is calculated by the formula: R = 0.2 / I LED

Read the specification (in English) for more details.

The LED driver on the QX5241 contains few parts and is always assembled according to this scheme:

The 5241 chip comes only in the SOT23-6 package, so it’s best not to approach it with a soldering iron for soldering pans. After installation, the board should be thoroughly washed to remove flux; any unknown contamination can negatively affect the operation of the microcircuit.

The difference between the supply voltage and the total voltage drop across the diodes should be 4 volts (or more). If it is less, then some glitches in operation are observed (current instability and inductor whistling). So take it with reserve. Moreover, the greater the output current, the greater the voltage reserve. Although, perhaps I just came across a bad copy of the microcircuit.

If the input voltage is less than the total drop across the LEDs, then generation fails. In this case, the output field switch opens completely and the LEDs light up (of course, not at full power, since the voltage is not enough).

AL9910

Diodes Incorporated has created one very interesting LED driver IC: the AL9910. It is curious in that its operating voltage range allows it to be connected directly to a 220V network (via a simple diode rectifier).

Here are its main characteristics:

input voltage - up to 500V (up to 277V for alternating);
built-in voltage stabilizer for powering the microcircuit, which does not require a quenching resistor;
the ability to adjust brightness by changing the potential on the control leg from 0.045 to 0.25V;
built-in overheating protection (triggered at 150°C);
operating frequency (25-300 kHz) is set by an external resistor;
requires an external one to work field-effect transistor;
Available in eight-legged SO-8 and SO-8EP packages.

The driver assembled on the AL9910 chip does not have galvanic isolation from the network, so it should be used only where direct contact with the circuit elements is impossible.

To design LED lamps, power sources—drivers—are constantly required. With a large volume, it is quite possible to assemble the drivers yourself, but the cost of such drivers is not so low, and manufacturing and soldering double-sided printed circuit boards with SMD components is a rather labor-intensive process at home.

I decided to make do with a ready-made driver. What was needed was an inexpensive driver without a housing, preferably with the ability to adjust the current and dimming.

I redrawn the diagram and modified it a little

Characteristics without capacitors ~0.9V and 8.7% (light flux ripple)

The output capacitor is expected to reduce ripple by half ~0.4V and 4%

But a 10uF capacitor at the input reduces ripple by 9 times ~0.1V and 1%, although adding this capacitor significantly reduces PF (power factor)

Both capacitors bring the output ripple characteristics closer to the specifications ~ 0.05V and 0.6%

So, ripple was defeated with the help of two capacitors from the old power supply.

Improvement No. 2. Setting the driver output current

The main purpose of the drivers is to maintain a stable current to the LEDs. This driver consistently produces 600mA.

Sometimes you want to change the driver current. This is usually done by selecting a resistor or capacitor in the feedback circuit. How are these drivers doing? And why are three parallel low-resistance resistors R4, R5, R6 installed here?

Everything is correct. They can set the output current. Apparently, all drivers are of the same power, but for different currents and differ precisely in these resistors and the output transformer, which gives different voltages.

If we carefully remove the 1.9 Ohm resistor, we get an output current of 430 mA by removing both 300 mA resistors.

You can go the other way by soldering another resistor in parallel, but this driver produces voltage up to 35V and with a higher current we will get excess power, which can lead to driver failure. But 700mA is quite possible to squeeze out.

So, by selecting resistors R4, R5 and R6, you can reduce the driver output current (or increase it very slightly) without changing the number of LEDs in the chain.

Revision 3. Dimming

There are three pins on the driver board labeled DIMM, which suggests that this driver can control the power of the LEDs. The datasheet for the microcircuit speaks about the same thing, although it does not contain typical dimming circuits. From the datasheet you can glean information that by applying a voltage of -0.3 - 6V to leg 7 of the microcircuit, you can obtain smooth power control.

Connecting a variable resistor to the DIMM pins does not lead to anything, in addition, leg 7 of the driver chip is not connected to anything at all. So again improvements.

Solder a 100K resistor to leg 7 of the microcircuit

Now by applying a voltage of 0-5V between ground and resistor we get a current of 60-600mA

To reduce the minimum dimming current, you must also reduce the resistor. Unfortunately, nothing is written about this in the datasheet, so you will have to select all the components experimentally. I was personally satisfied with dimming from 60 to 600mA.

If you need to organize dimming without external power supply, then you can take the driver supply voltage ~15V (leg 2 of the microcircuit or resistor R7) and apply it according to the following circuit.

Well, finally, I feed PWM from D3 of the Arduino to the dimming input.

I’m writing a simple sketch that changes the PWM level from 0 to maximum and back:

#include

void setup() (
pinMode(3, OUTPUT);
Serial.begin(9600);
analogWrite(3,0);
}

void loop() (
for(int i=0; i< 255; i+=10){
analogWrite(3,i);
delay(500);
}
for(int i=255; i>=0; i-=10)(
analogWrite(3,i);
delay(500);
}
}

I get dimming using PWM.

PWM dimming increases output ripple by about 10-20% compared to DC control. The maximum ripple increases approximately twice when the driver current is set to half the maximum.

Checking the driver for short circuit

The current driver must respond correctly to a short circuit. But it’s better to check the Chinese. I don't like such things. Stick something under voltage. But art requires sacrifice. We short-circuit the driver output during operation:

The driver tolerates short circuits normally and restores its operation. There is short circuit protection.

Let's sum it up

Pros of the driver

Small dimensions
Low cost
Possibility of current adjustment
Dimmable

Minuses

High output ripple (eliminates by adding capacitors)
The dimming input needs to be soldered
Little normal documentation. Incomplete datasheet
During operation, another disadvantage was discovered - interference on the radio in the FM range. It can be treated by installing the driver in an aluminum case or a case covered with foil or aluminum tape.

The drivers are quite suitable for those who are comfortable with a soldering iron or for those who are not, but are willing to tolerate output ripples of 3-4%.

useful links

From the series - cats are liquid. Timofey - 5-6 liters)))

Using LEDs as lighting sources usually requires a specialized driver. But it happens that the necessary driver is not at hand, but you need to organize lighting, for example, in a car, or test the LED for brightness. In this case, you can do it yourself for LEDs.

How to make a driver for LEDs

The circuits below use the most common elements that can be purchased at any radio store. No special equipment is required during assembly; all necessary tools are widely available. Despite this, with a careful approach, the devices work for quite a long time and are not much inferior to commercial samples.

Required materials and tools

In order to assemble a homemade driver, you will need:

Soldering iron with a power of 25-40 W. You can use more power, but this increases the risk of overheating of the elements and their failure. It is best to use a soldering iron with a ceramic heater and a non-burning tip, because... a regular copper tip oxidizes quite quickly and has to be cleaned.
Flux for soldering (rosin, glycerin, FKET, etc.). It is advisable to use a neutral flux - unlike active fluxes (phosphoric and hydrochloric acids, zinc chloride, etc.), it does not oxidize the contacts over time and is less toxic. Regardless of the flux used, after assembling the device, it is better to wash it with alcohol. For active fluxes this procedure is mandatory, for neutral ones - to a lesser extent.
Solder. The most common is low-melting tin-lead solder POS-61. Lead-free solders are less harmful when inhaling fumes during soldering, but have a higher melting point with lower fluidity and a tendency to degrade the weld over time.
Small pliers for bending leads.
Wire cutters or side cutters for cutting long ends of leads and wires.
Installation wires are insulated. Stranded copper wires with a cross-section of 0.35 to 1 mm2 are best suited.
Multimeter for monitoring voltage at nodal points.
Electrical tape or heat shrink tubing.
A small prototype board made of fiberglass. A board measuring 60x40 mm will be sufficient.

PCB development board for quick installation

Simple driver circuit for 1 W LED

One of the simplest circuits for powering a powerful LED is shown in the figure below:

As you can see, in addition to the LED, it includes only 4 elements: 2 transistors and 2 resistors.

The powerful n-channel field-effect transistor VT2 acts here as a regulator of the current passing through the LED. Resistor R2 determines the maximum current passing through the LED and also acts as a current sensor for transistor VT1 in the feedback circuit.

The more current passes through VT2, the greater the voltage drops across R2, accordingly VT1 opens and lowers the voltage at the gate of VT2, thereby reducing the LED current. In this way, stabilization of the output current is achieved.

The circuit is powered from a constant voltage source of 9 - 12 V, a current of at least 500 mA. The input voltage should be at least 1-2 V greater than the voltage drop across the LED.

Resistor R2 should dissipate 1-2 W of power, depending on the required current and supply voltage. Transistor VT2 is n-channel, designed for a current of at least 500 mA: IRF530, IRFZ48, IRFZ44N. VT1 – any low-power bipolar npn: 2N3904, 2N5088, 2N2222, BC547, etc. R1 - power 0.125 - 0.25 W with a resistance of 100 kOhm.

Due to the small number of elements, assembly can be carried out by hanging installation:

Another simple driver circuit based on the LM317 linear controlled voltage regulator:

Here the input voltage can be up to 35 V. The resistor resistance can be calculated using the formula:

where I is the current strength in amperes.

In this circuit, the LM317 will dissipate significant power given the large difference between the supply voltage and the LED drop. Therefore, it will have to be placed on a small one. The resistor must also be rated for at least 2 W.

This scheme is discussed more clearly in the following video:

Here we show how to connect a powerful LED using batteries with a voltage of about 8 V. When the voltage drop across the LED is about 6 V, the difference is small, and the chip does not heat up much, so you can do without a heatsink.

Please note that if there is a large difference between the supply voltage and the drop across the LED, it is necessary to place the microcircuit on a heat sink.

Power driver circuit with PWM input

Below is a circuit for powering high-power LEDs:

The driver is built on a dual comparator LM393. The circuit itself is a buck-converter, that is, a pulse step-down voltage converter.

Driver Features

Supply voltage: 5 - 24 V, constant;
Output current: up to 1 A, adjustable;
Output power: up to 18 W;
Output short circuit protection;
The ability to control brightness using an external PWM signal (it will be interesting to read how).

Operating principle

Resistor R1 with diode D1 form a source of reference voltage of about 0.7 V, which is additionally regulated by variable resistor VR1. Resistors R10 and R11 serve as current sensors for the comparator. As soon as the voltage across them exceeds the reference one, the comparator will close, thus closing the pair of transistors Q1 and Q2, and they, in turn, will close the transistor Q3. However, inductor L1 at this moment tends to resume the flow of current, so the current will flow until the voltage at R10 and R11 becomes less than the reference voltage, and the comparator opens transistor Q3 again.

The pair of Q1 and Q2 acts as a buffer between the output of the comparator and the gate of Q3. This protects the circuit from false positives due to interference on the Q3 gate, and stabilizes its operation.

The second part of the comparator (IC1 2/2) is used for additional brightness control using PWM. To do this, the control signal is applied to the PWM input: when TTL logic levels (+5 and 0 V) are applied, the circuit will open and close Q3. The maximum signal frequency at the PWM input is about 2 KHz. This input can also be used to turn the device on and off using the remote control.

D3 is a Schottky diode rated for current up to 1 A. If you cannot find a Schottky diode, you can use a pulse diode, for example FR107, but the output power will then decrease slightly.

The maximum output current is adjusted by selecting R2 and turning on or off R11. This way you can get the following values:

350 mA (1 W LED): R2=10K, R11 disabled,
700 mA (3 W): R2=10K, R11 connected, nominal 1 Ohm,
1A (5W): R2=2.7K, R11 connected, nominal 1 Ohm.

Within narrower limits, adjustment is made using a variable resistor and a PWM signal.

Assembling and configuring the driver

The driver components are mounted on a breadboard. First, the LM393 chip is installed, then the smallest components: capacitors, resistors, diodes. Then transistors are installed, and lastly a variable resistor.

It is better to place elements on the board in such a way as to minimize the distance between the connected pins and use as few wires as jumpers as possible.

When connecting, it is important to observe the polarity of the diodes and the pinout of the transistors, which can be found in the technical description for these components. Diodes can also be used in resistance measurement mode: in the forward direction, the device will show a value of the order of 500-600 Ohms.

To power the circuit, you can use an external DC voltage source of 5-24 V or batteries. 6F22 (“crown”) and other batteries have too small a capacity, so their use is impractical when using high-power LEDs.

After assembly, you need to adjust the output current. To do this, LEDs are soldered to the output, and the VR1 engine is set to the lowest position according to the diagram (checked with a multimeter in the “testing” mode). Next, we apply the supply voltage to the input, and by rotating the VR1 knob we achieve the required brightness.

List of elements:

Conclusion

The first two of the considered circuits are very simple to manufacture, but they do not provide short circuit protection and have rather low efficiency. For long-term use, the third circuit on LM393 is recommended, since it does not have these disadvantages and has greater capabilities for adjusting the output power.

The article is devoted to the repair of LED spotlight drivers. I remind you that I recently already had an article on, I recommend you read it.

Article on LED driver circuits and their repair

Sasha, hello.

In particular, on the topic of lighting - diagrams of two modules from automotive LED spotlights with a voltage of 12V. At the same time, I want to ask you and the readers a few questions about the components of these modules.

I am not good at writing articles; I write about my experience in repairing some electronic devices (this is mainly power electronics) only on forums, answering questions from forum participants. There I also share diagrams that I copied from devices that I had to repair. I hope the LED driver diagrams I drew will help readers with repairs.

I paid attention to the circuits of these two LED drivers because they are simple, like a scooter, and very easy to repeat with your own hands. If there were no questions with the YF-053CREE-40W module driver, then there are several of them regarding the circuit topology of the second module of the TH-T0440C LED spotlight.

LED driver circuit for YF-053CREE-40W LED module

The appearance of this spotlight is shown at the beginning of the article, but this is what this lamp looks like from behind, the radiator is visible:

The LED modules of this spotlight look like this:

I have a lot of experience in copying circuits from real complex devices, so I copied the circuit of this driver easily, here it is:

YF-053 CREE LED spotlight driver, electrical circuit

Schematic diagram of LED driver TH-T0440C

What does this module look like (this is a car LED headlight):

Electrical diagram:

There is more incomprehensibility in this scheme than in the first one.

Firstly, due to the unusual switching circuit of the PWM controller, I was not able to identify this microcircuit. In some connections it is similar to the AL9110, but then it is not clear how it works without connecting its pins Vin (1), Vcc (Vdd) (6) and LD (7) to the circuit?

The question also arises about connecting MOSFET Q2 and its entire wiring. After all, it has an N-channel, but is connected in reverse polarity. With such a connection, only its antiparallel diode works, and the transistor itself and its entire “retinue” are completely useless. It was enough to replace it with a powerful Schottky diode, or a “accordion” of smaller ones.

What's new in the VK group? SamElectric.ru ?

Subscribe and read the article further:

LEDs for LED drivers

I couldn't decide on LEDs. They are the same in both modules, although their manufacturers are different. There are no inscriptions on the LEDs (with reverse side- Same). I searched from different sellers under the line “Ultra-bright LEDs for LED spotlights and LED chandeliers.” They sell a bunch of different LEDs there, but all of them are either without lenses or with lenses at 60º, 90º and 120º.

I have never met one similar in appearance to mine.

Actually, both modules have the same malfunction - partial or complete degradation of the LED crystals. I think the reason is the maximum current from the drivers, set by the manufacturers (Chinese) for marketing purposes. Like, look how bright our chandeliers are. And the fact that they shine for at most 10 hours does not bother them.

If there are complaints from buyers, they can always answer that the spotlights are out of order due to shaking, because such “chandeliers” are mainly bought by the owners of jeeps, and they drive not only on the highway.

If I can find LEDs, I will reduce the driver current until the brightness of the LEDs noticeably decreases.

It is better to look for LEDs on AliExpress, there big choice. But this is roulette, depending on your luck.

Datasheets (technical information) for some high-power LEDs will be at the end of the article.

I think the main thing for long-term operation of LEDs is not to chase brightness, but to set the optimal operating current.

See you later, Sergey.

P.S. I’ve been a fan of electronics since 1970, when I assembled my first detector receiver during a physics lesson.

More driver circuits

Below I will post some information on diagrams and repairs from me (author of the SamElectric.ru blog)

LED floodlight Navigator, discussed in the article (the link was already given at the beginning of the article).

The circuit is standard, the output current varies due to the ratings of the piping elements and the power of the transformer:

LED Driver MT7930 Typical. Typical electrical circuit diagram for an LED spotlight

The circuit is taken from the datasheet for this chip, here it is:

/ Description, typical connection circuit and microcircuit parameters for drivers of LED modules and matrices., pdf, 661.17 kB, downloaded: 1684 times./

The datasheet describes in detail what needs to be changed and how to get the desired output current of the driver.

Here is a more detailed driver diagram, closer to reality:

Do you see the formula to the left of the diagram? It shows what the output current depends on. First of all, from the resistor Rs, which is located at the source of the transistor and consists of three parallel resistors. These resistors, and at the same time the transistor, burn out.

Having the diagram, you can begin repairing the driver.

But even without a diagram, we can immediately say that first of all we need to pay attention to:

input circuits,
diode bridge,
electrolytes,
power transistor,
soldering

I myself have repaired just such drivers several times. Sometimes the only thing that helped was a complete replacement of the microcircuit, transistor and almost the entire wiring. This is very labor-intensive and economically unjustified. As a rule – it’s much easier and cheaper – I bought and installed a new Led Driver, or refused repairs altogether.

Download and buy

Here are the datasheets (technical information) for some high-power LEDs:

/ Technical information on high-power LEDs for headlights and spotlights, pdf, 689.35 kB, downloaded: 727 times./

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Special thanks to those who have circuits of real LED drivers for the collection. I will publish them in this article.

The guarantee of brightness, efficiency and durability of LED sources is proper nutrition, which can be provided by special electronic devices - drivers for LEDs. They convert AC voltage in a 220V network into voltage direct current set value. An analysis of the main types and characteristics of devices will help you understand what function converters perform and what to look for when choosing them.

The main function of an LED driver is to provide a stabilized current passing through the LED device. The value of the current flowing through the semiconductor crystal must correspond to the nameplate parameters of the LED. This will ensure the stability of the crystal's glow and help avoid its premature degradation. In addition, at a given current, the voltage drop will correspond to the value required for the p-n junction. You can find out the appropriate supply voltage for the LED using the current-voltage characteristic.

When lighting residential and office premises LED lamps and lamps, drivers are used, the power of which is supplied from a 220V AC network. Automotive lighting (headlights, DRLs, etc.), bicycle headlights, and portable flashlights use DC power supplies in the range from 9 to 36V. Some low-power LEDs can be connected without a driver, but then a resistor must be included in the circuit for connecting the LED to a 220-volt network.

The driver output voltage is indicated in the range of two final values, between which stable operation is ensured. There are adapters with an interval from 3V to several tens. To power a circuit of 3 series-connected white LEDs, each of which has a power of 1 W, you will need a driver with output values U - 9-12V, I - 350 mA. The voltage drop for each crystal will be about 3.3V, for a total of 9.9V, which will be within the driver range.

Main characteristics of converters

Before you buy a driver for LEDs, you should familiarize yourself with the basic characteristics of the devices. These include output voltage, rated current and power. The output voltage of the converter depends on the voltage drop across the LED source, as well as on the connection method and the number of LEDs in the circuit. The current depends on the power and brightness of the emitting diodes. The driver must provide the LEDs with the current they need to maintain the required brightness.

One of important characteristics The driver is the power that the device produces in the form of a load. The choice of driver power is influenced by the power of each LED device, total and the color of the LEDs. The algorithm for calculating power is that the maximum power of the device should not be lower than the consumption of all LEDs:

P = P(led) × n,

where P(led) is the power of a single LED source, and n is the number of LEDs.

In addition, it must be fulfilled required condition, which would provide a power reserve of 25-30%. So the value maximum power must be no less than the value (1.3 x P).

You should also take into account the color characteristics of the LEDs. After all, semiconductor crystals of different colors have different voltage drops when a current of the same strength passes through them. So the voltage drop of a red LED at a current of 350 mA is 1.9-2.4 V, then the average value of its power will be 0.75 W. For the green analogue, the voltage drop is in the range from 3.3 to 3.9V and at the same current the power will be 1.25 W. This means that 16 red LED sources or 9 green ones can be connected to the driver for 12V LEDs.

Helpful advice! When choosing a driver for LEDs, experts advise not to neglect the maximum power value of the device.

What are the types of drivers for LEDs by device type?

Drivers for LEDs are classified by device type into linear and pulsed. The structure and typical driver circuit for linear-type LEDs is a current generator on a transistor with a p-channel. Such devices provide smooth current stabilization under the condition of unstable voltage on the input channel. They are simple and cheap devices, but they are low efficient, generate a lot of heat during operation and cannot be used as drivers for high-power LEDs.

Pulse devices create a series of high-frequency pulses in the output channel. Their operation is based on the PWM (pulse width modulation) principle, when average value The output current is determined by the duty cycle, i.e. the ratio of the pulse duration to the number of its repetitions. The change in the average output current occurs due to the fact that the pulse frequency remains unchanged, and the duty cycle varies from 10-80%.

Due to the high conversion efficiency (up to 95%) and compactness of the devices, they are widely used for portable LED designs. In addition, the efficiency of the devices has a positive effect on the duration of operation of autonomous power devices. Pulse type converters are compact in size and have a wide range of input voltages. The disadvantage of these devices is the high level of electromagnetic interference.

Helpful advice! You should purchase an LED driver at the stage of selecting LED sources, having previously decided on a circuit of LEDs from 220 volts.

Before choosing a driver for LEDs, you need to know the conditions of its operation and the location of the LED devices. Pulse-width drivers, which are based on a single microcircuit, are miniature in size and are designed to be powered from autonomous low-voltage sources. The main application of these devices is car tuning and LED lights. However, due to the use of a simplified electronic circuit the quality of such converters is somewhat lower.

Dimmable LED Drivers

Modern drivers for LEDs are compatible with dimming devices for semiconductor devices. The use of dimmable drivers allows you to control the level of illumination in rooms: reduce the intensity of the glow in daytime, emphasize or hide individual elements in the interior, zone the space. This, in turn, makes it possible not only to rationally use electricity, but also to save the resource of the LED light source.

Dimmable drivers come in two types. Some are connected between the power supply and LED sources. Such devices control the energy supplied from the power supply to the LEDs. Such devices are based on PWM control, in which energy is supplied to the load in the form of pulses. The duration of the pulses determines the amount of energy from the minimum to the maximum value. Drivers of this type are mainly used for fixed voltage LED modules such as LED strips, creeping lines, etc.

The driver is controlled using PWM or

Dimmable converters of the second type control directly the power source. The principle of their operation is both PWM regulation and control of the amount of current flowing through the LEDs. Dimmable drivers of this type are used for LED devices with stabilized current. It is worth noting that when controlling LEDs using PWM control, effects that negatively affect vision are observed.

Comparing these two control methods, it is worth noting that when regulating the current through LED sources, not only a change in the brightness of the glow is observed, but also a change in the color of the glow. Thus, white LEDs emit yellowish light at lower currents, and glow blue when increased. When controlling LEDs using PWM control, effects that negatively affect vision and a high level of electromagnetic interference are observed. In this regard, PWM control is used quite rarely, unlike current regulation.

LED Driver Circuits

Many manufacturers produce driver chips for LEDs that allow the sources to be powered from a reduced voltage. All existing drivers are divided into simple ones, made on the basis of 1-3 transistors, and more complex ones using special microcircuits with pulse width modulation.

ON Semiconductor offers a wide selection of ICs as the basis for drivers. They are characterized by reasonable cost, excellent conversion efficiency, cost-effectiveness and low level electromagnetic pulses. The manufacturer presents a pulse-type driver UC3845 with an output current of up to 1A. On such a chip you can implement a driver circuit for a 10W LED.

Electronic components HV9910 (Supertex) is a popular driver IC due to its simple circuit resolution and low price. It has a built-in voltage regulator and outputs for brightness control, as well as an output for programming the switching frequency. The output current value is up to 0.01A. On this chip it is possible to implement a simple driver for LEDs.

Based on the UCC28810 chip (produced by Texas Instruments) you can create a driver circuit for high-power LEDs. In such an LED driver circuit, an output voltage of 70-85V can be created for LED modules consisting of 28 LED sources with a current of 3 A.

Helpful advice! If you are planning to buy ultra-bright 10 W LEDs, you can use a switching driver based on the UCC28810 chip for designs made from them.

Clare offers a simple pulse-type driver based on the CPC 9909 chip. It includes a converter controller housed in a compact housing. Due to the built-in voltage stabilizer, the converter can be powered from a voltage of 8-550V. The CPC 9909 chip allows the driver to operate in conditions of wide variation temperature conditions from -50 to 80°C.

How to choose a driver for LEDs

There is a wide range of LED drivers on the market from different manufacturers. Many of them, especially made in China, have a low price. However, buying such devices is not always profitable, since most of them do not meet the declared characteristics. In addition, such drivers are not accompanied by a warranty, and if they are found to be defective, they cannot be returned or replaced with quality ones.

Thus, there is a possibility of purchasing a driver whose declared power is 50 W. However, in reality it turns out that this characteristic is not permanent and such power is only short-term. In reality, such a device will work as a 30W or maximum 40W LED driver. It may also turn out that the filling will be missing some components responsible for the stable functioning of the driver. In addition, components of low quality and with a short service life may be used, which is essentially a defect.

When purchasing, you should pay attention to the product brand. A quality product will definitely indicate the manufacturer, who will provide a guarantee and will be ready to be responsible for their products. It should be noted that the service life of drivers from trusted manufacturers will be much longer. Below is the approximate operating time of the drivers depending on the manufacturer:

driver from dubious manufacturers - no more than 20 thousand hours;
devices of average quality - about 50 thousand hours;
converter from a trusted manufacturer using high-quality components - over 70 thousand hours.

Helpful advice! The quality of the LED driver is up to you to decide. However, it should be noted that it is especially important to purchase a proprietary converter if we're talking about about its use for LED spotlights and powerful lamps.

Calculation of drivers for LEDs

To determine the output voltage of the LED driver, it is necessary to calculate the ratio of power (W) to current (A). For example, the driver has the following characteristics: power 3W and current 0.3A. Design ratio is 10V. Thus, this will be the maximum output voltage of this converter.

Related article:

Types. Connection diagrams for LED sources. Resistance calculation for LEDs. Checking the LED with a multimeter. DIY LED designs.

If you need to connect 3 LED sources, the current of each of them is 0.3 mA at a supply voltage of 3V. Connecting one of the devices to the LED driver, the output voltage will be equal to 3V and the current will be 0.3 A. By collecting two LED sources in series, the output voltage will be equal to 6V and the current will be 0.3 A. By adding a third LED to the serial chain, we will get 9V and 0.3 A. With a parallel connection, 0.3 A will be equally distributed between the 0.1 A LEDs. Connecting the LEDs to a 0.3 A device with a current value of 0.7, they will receive only 0.3 A.

This is the algorithm for the functioning of LED drivers. They produce the amount of current for which they are designed. The method of connecting LED devices in this case does not matter. There are driver models that require any number of LEDs connected to them. But then there is a limitation on the power of LED sources: it should not exceed the power of the driver itself. Drivers are available that are designed for a certain number of connected LEDs. A smaller number of LEDs can be connected to them. But such drivers have low efficiency, unlike devices designed for a specific number of LED devices.

It should be noted that drivers designed for a fixed number of emitting diodes are provided with protection against emergency situations. Such converters do not work correctly if fewer LEDs are connected to them: they will flicker or not light up at all. Thus, if you connect voltage to the driver without an appropriate load, it will work unstable.

Where to buy drivers for LEDs

You can buy LED-drivers at specialized points selling radio components. In addition, it is much more convenient to familiarize yourself with the products and order the necessary product using the catalogs of the relevant sites. In addition, in online stores you can purchase not only converters, but also LED lighting devices and related products: control devices, connection tools, electronic components for repairing and assembling a driver for LEDs with your own hands.

Selling companies offer a huge range of drivers for LEDs, specifications and the prices of which can be seen in the price lists. As a rule, product prices are indicative and are specified when ordering from the project manager. The range includes converters of various powers and degrees of protection, used for external and internal lighting, as well as for illumination and tuning of cars.

When choosing a driver, you should take into account the conditions of its use and the power consumption of the LED design. Therefore, it is necessary to purchase a driver before purchasing LEDs. So, before you buy a driver for 12 volt LEDs, you need to take into account that it should have a power reserve of about 25-30%. This is necessary in order to reduce the risk of damage or complete failure of the device due to a short circuit or voltage surges in the network. The cost of the converter depends on the number of devices purchased, form of payment and delivery time.

The table shows the main parameters and dimensions of 12 volt voltage stabilizers for LEDs, indicating their estimated price:

Modification LD DC/AC 12 V	Dimensions, mm (h/w/d)	Output current, A	Power, W	price, rub.
1x1W 3-4VDC 0.3A MR11	8/25/12	0,3	1x1	73
3x1W 9-12VDC 0.3A MR11	8/25/12	0,3	3x1	114
3x1W 9-12VDC 0.3A MR16	12/28/18	0,3	3x1	35
5-7x1W 15-24VDC 0.3A	12/14/14	0,3	5-7x1	80
10W 21-40V 0.3A AR111	21/30	0,3	10	338
12W 21-40V 0.3A AR11	18/30/22	0,3	12	321
3x2W 9-12VDC 0.4A MR16	12/28/18	0,4	3x2	18
3x2W 9-12VDC 0.45A	12/14/14	0,45	3x2	54

Making drivers for LEDs with your own hands

Using ready-made microcircuits, radio amateurs can independently assemble drivers for LEDs of various powers. To do this you need to be able to read electrical circuits and have skills in working with a soldering iron. For example, you can consider several options for DIY LED drivers for LEDs.

The driver circuit for a 3W LED can be implemented based on the PT4115 chip made in China by PowTech. The microcircuit can be used to power LED devices over 1W and includes control units that have enough output powerful transistor. The PT4115 based driver has high efficiency and has minimal amount strapping components.

Overview of PT4115 and technical parameters of its components:

light brightness control function (dimming);
input voltage – 6-30V;
output current value – 1.2 A;
current stabilization deviation up to 5%;
protection against load breaks;
presence of outputs for dimming;
efficiency – up to 97%.

The microcircuit has the following conclusions:

for output switch – SW;
for the signal and supply sections of the circuit – GND;
for brightness control – DIM;
input current sensor – CSN;
supply voltage – VIN;

DIY LED driver circuit based on PT4115

Driver circuits for powering LED devices with a dissipating power of 3 W can be designed in two versions. The first assumes the presence of a power source with a voltage from 6 to 30V. Another circuit provides power from an AC source with a voltage of 12 to 18V. In this case, a diode bridge is introduced into the circuit, at the output of which a capacitor is installed. It helps smooth out voltage fluctuations; its capacity is 1000 μF.

For the first and second schemes special meaning has a capacitor (CIN): this component is designed to reduce ripple and compensate for the energy stored in the inductor when the MOP transistor turns off. In the absence of a capacitor, all the inductive energy through semiconductor diode The DSB (D) will get to the supply voltage output (VIN) and cause a breakdown of the microcircuit relative to the power supply.

Helpful advice! It should be taken into account that connecting a driver for LEDs in the absence of an input capacitor is not permitted.

Taking into account the number and how much LEDs consume, the inductance (L) is calculated. In the LED driver circuit, you should select an inductance whose value is 68-220 μH. This is evidenced by data from technical documentation. It is possible to admit slight increase values of L, however, it should be taken into account that then the efficiency of the circuit as a whole will decrease.

As soon as voltage is applied, the magnitude of the current passing through the resistor RS (works as a current sensor) and L will be zero. Next, the CS comparator analyzes the potential levels located before and after the resistor - as a result, a high concentration appears at the output. The current going to the load increases to a certain value controlled by RS. The current increases depending on the inductance value and the voltage value.

Assembling Driver Components

The wiring components of the RT 4115 microcircuit are selected taking into account the manufacturer’s instructions. For CIN, a low impedance capacitor (low ESR capacitor) should be used, since the use of other analogues will negatively affect the driver efficiency. If the device is powered from a unit with a stabilized current, one capacitor with a capacity of 4.7 μF or more will be needed at the input. It is recommended to place it next to the microcircuit. If the current is alternating, you will need to introduce a solid tantalum capacitor with a capacitance of at least 100 μF.

In the connection circuit for 3 W LEDs, it is necessary to install a 68 μH inductor. It should be located as close to the SW terminal as possible. You can make the coil yourself. To do this, you will need a ring from a failed computer and a winding wire (PEL-0.35). As diode D, you can use the FR 103 diode. Its parameters: capacitance 15 pF, recovery time 150 ns, temperature from -65 to 150 ° C. It can handle current pulses up to 30A.

The minimum value of the RS resistor in an LED driver circuit is 0.082 ohms, the current is 1.2 A. To calculate the resistor, you need to use the value of the current required by the LED. Below is the formula for calculation:

RS = 0.1/I,

where I is the rated current of the LED source.

The RS value in the LED driver circuit is 0.13 Ohm, respectively, the current value is 780 mA. If such a resistor cannot be found, several low-resistance components can be used, using the resistance formula for parallel and series connection in the calculation.

DIY driver layout for a 10 Watt LED

Build driver for powerful LED you can do it yourself, using electronic boards from failed fluorescent lamps. Most often, the lamps in such lamps burn out. Electronic board remains working, which allows you to use its components for homemade power supplies, drivers and other devices. Transistors, capacitors, diodes, and inductors (chokes) may be needed for operation.

The faulty lamp must be carefully disassembled using a screwdriver. To make a driver for a 10 W LED, you should use fluorescent lamp, the power of which is 20 W. This is necessary so that the throttle can withstand the load with a reserve. For more powerful lamp you should either select the appropriate board, or replace the inductor itself with an analogue one with a larger core. For LED sources with less power you can adjust the number of turns of the winding.

Next, you need to make 20 turns of wire over the primary turns of the winding and use a soldering iron to connect this winding to the rectifier diode bridge. After this, apply voltage from the 220V network and measure the output voltage on the rectifier. Its value was 9.7V. The LED source consumes 0.83 A through the ammeter. The rating of this LED is 900 mA, however, the reduced current consumption will increase its resource. The diode bridge is assembled by hanging installation.

The new board and diode bridge can be placed in a stand from an old table lamp. Thus, the LED driver can be assembled independently from available radio components from failed devices.

Due to the fact that LEDs are quite demanding on power supplies, it is necessary to select the right driver for them. If the converter is chosen correctly, you can be sure that the parameters of LED sources will not deteriorate and the LEDs will last their intended life.