Converting the LDC driver to an LED. LED lamp circuit: device of the simplest drivers. Step-by-step instructions for making a DIY LED driver

Due to low energy consumption, theoretical durability and lower prices, incandescent and energy-saving lamps are rapidly replacing them. But, despite the declared service life of up to 25 years, they often burn out without even serving the warranty period.

Unlike incandescent lamps, 90% of burnt-out LED lamps can be successfully repaired with your own hands, even without special training. The examples presented will help you repair failed LED lamps.

Before you undertake any repairs LED lamp you need to imagine its device. Regardless of the appearance and type of LEDs used, all LED lamps, including filament bulbs, are designed the same. If you remove the walls of the lamp housing, you can see the driver inside, which is a printed circuit board with radio elements installed on it.

Any LED lamp is designed and works as follows. The supply voltage from the contacts of the electric cartridge is supplied to the terminals of the base. Two wires are soldered to it, through which voltage is supplied to the driver input. From the driver, the DC supply voltage is supplied to the board on which the LEDs are soldered.

The driver is an electronic unit - a current generator that converts the supply voltage into the current required to light the LEDs.

Sometimes, to diffuse light or protect against human contact with unprotected conductors of a board with LEDs, it is covered with diffusing protective glass.

About filament lamps

In appearance, a filament lamp is similar to an incandescent lamp. The design of filament lamps differs from LED lamps in that they do not use a board with LEDs as light emitters, but a sealed glass flask filled with gas, in which one or more filament rods are placed. The driver is located in the base.

The filament rod is a glass or sapphire tube with a diameter of about 2 mm and a length of about 30 mm, on which 28 miniature LEDs coated in series with a phosphor are attached and connected. One filament consumes about 1 W of power. My operating experience shows that filament lamps are much more reliable than those made on the basis of SMD LEDs. I believe that over time they will replace all other artificial light sources.

Examples of LED lamp repairs

Attention, electrical circuits LED lamp drivers are galvanically connected to the mains phase and therefore extreme care should be taken. Touching an unprotected part of a person’s body to exposed parts of a circuit connected to an electrical network can cause serious damage to health, including cardiac arrest.

LED lamp repair
ASD LED-A60, 11 W on SM2082 chip

Currently, powerful LED light bulbs have appeared, the drivers of which are assembled on SM2082 type chips. One of them worked for less than a year and ended up being repaired. The light went out randomly and came on again. When you tapped it, it responded with light or extinguishing. It became obvious that the problem was poor contact.

To get to the electronic part of the lamp, you need to use a knife to pick up the diffuser glass at the point of contact with the body. Sometimes it is difficult to separate the glass, since when it is seated, silicone is applied to the fixing ring.

After removing the light-scattering glass, access to the LEDs and the SM2082 current generator microcircuit became available. In this lamp, one part of the driver was mounted on an aluminum LED printed circuit board, and the second on a separate one.

An external inspection did not reveal any defective soldering or broken tracks. I had to remove the board with LEDs. To do this, the silicone was first cut off and the board was pryed off by the edge with a screwdriver blade.

To get to the driver located in the lamp body, I had to unsolder it by heating two contacts with a soldering iron at the same time and moving it to the right.

On one side of the driver circuit board, only an electrolytic capacitor with a capacity of 6.8 μF for a voltage of 400 V was installed.

WITH reverse side The driver board was equipped with a diode bridge and two series-connected resistors with a nominal value of 510 kOhm.

In order to figure out which of the boards the contact was missing, we had to connect them, observing the polarity, using two wires. After tapping the boards with the handle of a screwdriver, it became obvious that the fault lies in the board with the capacitor or in the contacts of the wires coming from the base of the LED lamp.

Since the soldering did not raise any suspicions, I first checked the reliability of the contact in the central terminal of the base. It can be easily removed if you pry it over the edge with a knife blade. But the contact was reliable. Just in case, I tinned the wire with solder.

It is difficult to remove the screw part of the base, so I decided to use a soldering iron to solder the soldering wires coming from the base. When I touched one of the soldering joints, the wire became exposed. A “cold” solder was detected. Since there was no way to get to the wire to strip it, I had to lubricate it with FIM active flux and then solder it again.

After assembly, the LED lamp consistently emitted light, despite hitting it with the handle of a screwdriver. Checking the light flux for pulsations showed that they are significant with a frequency of 100 Hz. Such an LED lamp can only be installed in luminaires for general lighting.

Driver circuit diagram
LED lamp ASD LED-A60 on SM2082 chip

The electrical circuit of the ASD LED-A60 lamp, thanks to the use of a specialized SM2082 microcircuit in the driver to stabilize the current, turned out to be quite simple.

The driver circuit works as follows. The AC supply voltage is supplied through fuse F to the rectifier diode bridge assembled on the MB6S microassembly. Electrolytic capacitor C1 smoothes out ripples, and R1 serves to discharge it when the power is turned off.

From the positive terminal of the capacitor, the supply voltage is supplied directly to the LEDs connected in series. From the output of the last LED, the voltage is supplied to the input (pin 1) of the SM2082 microcircuit, the current in the microcircuit is stabilized and then from its output (pin 2) goes to the negative terminal of capacitor C1.

Resistor R2 sets the amount of current flowing through the HL LEDs. The amount of current is inversely proportional to its rating. If the value of the resistor is decreased, the current will increase; if the value is increased, the current will decrease. The SM2082 microcircuit allows you to adjust the current value with a resistor from 5 to 60 mA.

LED lamp repair
ASD LED-A60, 11 W, 220 V, E27

The repair included another ASD LED-A60 LED lamp, similar in appearance and with the same technical characteristics as the one repaired above.

When turned on, the lamp came on for a moment and then did not shine. This behavior of LED lamps is usually associated with a driver failure. So I immediately started disassembling the lamp.

The light-diffusing glass was removed with great difficulty, since along the entire line of contact with the body it was, despite the presence of a retainer, generously lubricated with silicone. To separate the glass, I had to look for a pliable place along the entire line of contact with the body using a knife, but still there was a crack in the body.

To gain access to the lamp driver, the next step was to remove the LED printed circuit board, which was pressed along the contour into the aluminum insert. Despite the fact that the board was aluminum and could be removed without fear of cracks, all attempts were unsuccessful. The board held tight.

It was also not possible to remove the board together with the aluminum insert, since it fit tightly to the case and was seated with the outer surface on silicone.

I decided to try removing the driver board from the base side. To do this, first, a knife was pryed out of the base and the central contact was removed. To remove the threaded part of the base, it was necessary to slightly bend its upper flange so that the core points would disengage from the base.

The driver became accessible and was freely extended to a certain position, but it was not possible to remove it completely, although the conductors from the LED board were sealed off.

The LED board had a hole in the center. I decided to try to remove the driver board by hitting its end through a metal rod threaded through this hole. The board moved a few centimeters and hit something. After further blows, the lamp body cracked along the ring and the board with the base of the base separated.

As it turned out, the board had an extension whose shoulders rested against the lamp body. It looks like the board was shaped this way to limit movement, although it would have been enough to fix it with a drop of silicone. Then the driver would be removed from either side of the lamp.

The 220 V voltage from the lamp base is supplied through a resistor - fuse FU to the MB6F rectifier bridge and is then smoothed out by an electrolytic capacitor. Next, the voltage is supplied to the SIC9553 chip, which stabilizes the current. Parallel connected resistors R20 and R80 between pins 1 and 8 MS set the amount of LED supply current.

The photo shows a typical electrical circuit diagram provided by the manufacturer of the SIC9553 chip in the Chinese datasheet.

This photo shows appearance LED lamp driver from the installation side of the output elements. Since space allowed, to reduce the pulsation coefficient of the light flux, the capacitor at the driver output was soldered to 6.8 μF instead of 4.7 μF.

If you have to remove the drivers from the body of this lamp model and cannot remove the LED board, you can use a jigsaw to cut the lamp body around the circumference just above the screw part of the base.

In the end, all my efforts to remove the driver turned out to be useful only for understanding the LED lamp structure. The driver turned out to be OK.

The flash of the LEDs at the moment of switching on was caused by a breakdown in the crystal of one of them as a result of a voltage surge when the driver was started, which misled me. It was necessary to ring the LEDs first.

An attempt to test the LEDs with a multimeter was unsuccessful. The LEDs did not light up. It turned out that two light-emitting crystals connected in series are installed in one case, and in order for the LED to start flowing current, it is necessary to apply a voltage of 8 V to it.

A multimeter or tester turned on in resistance measurement mode produces a voltage within 3-4 V. I had to check the LEDs using a power supply, supplying 12 V to each LED through a 1 kOhm current-limiting resistor.

There was no replacement LED available, so the pads were shorted with a drop of solder instead. This is safe for driver operation, and the power of the LED lamp will decrease by only 0.7 W, which is almost imperceptible.

After repairing the electrical part of the LED lamp, the cracked body was glued with quick-drying Moment super glue, the seams were smoothed by melting the plastic with a soldering iron and leveled with sandpaper.

Just for fun, I did some measurements and calculations. The current flowing through the LEDs was 58 mA, the voltage was 8 V. Therefore, the power supplied to one LED was 0.46 W. With 16 LEDs, the result is 7.36 W, instead of the declared 11 W. Perhaps the manufacturer has indicated the total power consumption of the lamp, taking into account losses in the driver.

The service life of the ASD LED-A60, 11 W, 220 V, E27 LED lamp declared by the manufacturer raises serious doubts in my mind. In the small volume of the plastic lamp body, with low thermal conductivity, significant power is released - 11 W. As a result, the LEDs and driver operate at the maximum permissible temperature, which leads to accelerated degradation of their crystals and, as a consequence, to a sharp reduction in their time between failures.

LED lamp repair
LED smd B35 827 ERA, 7 W on BP2831A chip

An acquaintance shared with me that he bought five light bulbs like in the photo below, and after a month they all stopped working. He managed to throw away three of them, and, at my request, brought two for repairs.

The light bulb worked, but instead of bright light it emitted a flickering weak light with a frequency of several times per second. I immediately assumed that the electrolytic capacitor had swollen; usually, if it fails, the lamp begins to emit light like a strobe.

The light-scattering glass came off easily, it was not glued. It was fixed by a slot on its rim and a protrusion in the lamp body.

The driver was secured using two solders to a printed circuit board with LEDs, as in one of the lamps described above.

A typical driver circuit on the BP2831A chip taken from the datasheet is shown in the photograph. The driver board was removed and all simple radio elements were checked; they all turned out to be in good order. I had to start checking the LEDs.

The LEDs in the lamp were installed of an unknown type with two crystals in the housing and inspection did not reveal any defects. By connecting the leads of each LED in series, I quickly identified the faulty one and replaced it with a drop of solder, as in the photo.

The light bulb worked for a week and was repaired again. Shorted the next LED. A week later I had to short-circuit another LED, and after the fourth I threw out the light bulb because I was tired of repairing it.

The reason for the failure of light bulbs of this design is obvious. LEDs overheat due to insufficient heat sink surface, and their service life is reduced to hundreds of hours.

Why is it permissible to short-circuit the terminals of burnt-out LEDs in LED lamps?

The LED lamp driver, unlike a constant voltage power supply, produces a stabilized current value at the output, not a voltage. Therefore, regardless of the load resistance within the specified limits, the current will always be constant and, therefore, the voltage drop across each of the LEDs will remain the same.

Therefore, as the number of series-connected LEDs in the circuit decreases, the voltage at the driver output will also decrease proportionally.

For example, if 50 LEDs are connected in series to the driver, and each of them drops a voltage of 3 V, then the voltage at the driver output is 150 V, and if you short-circuit 5 of them, the voltage will drop to 135 V, and the current will not change.

But the coefficient useful action(Efficiency) of a driver assembled according to this scheme will be low and power losses will be more than 50%. For example, for an LED light bulb MR-16-2835-F27 you will need a 6.1 kOhm resistor with a power of 4 watts. It turns out that the driver on the resistor will consume power exceeding the power consumption of the LEDs and it will be placed in a small case LED lamps, due to allocation more heat will be unacceptable.

But if there is no other way to repair an LED lamp and it is very necessary, then the resistor driver can be placed in a separate housing; anyway, the power consumption of such an LED lamp will be four times less than incandescent lamps. It should be noted that the more LEDs connected in series in a light bulb, the higher the efficiency will be. With 80 series-connected SMD3528 LEDs, you will need an 800 Ohm resistor with a power of only 0.5 W. The capacitance of capacitor C1 will need to be increased to 4.7 µF.

Finding faulty LEDs

After removing the protective glass, it becomes possible to check the LEDs without peeling off the printed circuit board. First of all, a careful inspection of each LED is carried out. If even the smallest black dot is detected, not to mention blackening of the entire surface of the LED, then it is definitely faulty.

When inspecting the appearance of the LEDs, you need to carefully examine the quality of the soldering of their terminals. One of the light bulbs being repaired turned out to have four LEDs that were poorly soldered.

The photo shows a light bulb that had very small black dots on its four LEDs. I immediately noted faulty LEDs crosses so that they are clearly visible.

Faulty LEDs may not have any changes in appearance. Therefore, it is necessary to check each LED with a multimeter or pointer tester turned on in resistance measurement mode.

There are LED lamps in which standard LEDs are installed in appearance, in the housing of which two crystals connected in series are mounted at once. For example, lamps of the ASD LED-A60 series. To test such LEDs, it is necessary to apply a voltage of more than 6 V to its terminals, and any multimeter produces no more than 4 V. Therefore, checking such LEDs can only be done by applying a voltage of more than 6 (recommended 9-12) V to them from the power source through a 1 kOhm resistor .

The LED is checked like a regular diode; in one direction the resistance should be equal to tens of megaohms, and if you swap the probes (this changes the polarity of the voltage supply to the LED), then it should be small, and the LED may glow dimly.

When checking and replacing LEDs, the lamp must be fixed. To do this, you can use a suitable sized round jar.

You can check the serviceability of the LED without an additional DC source. But this verification method is possible if the light bulb driver is working properly. To do this, it is necessary to apply supply voltage to the base of the LED light bulb and short-circuit the terminals of each LED in series with each other using a wire jumper or, for example, the jaws of metal tweezers.

If suddenly all the LEDs light up, it means that the shorted one is definitely faulty. This method is suitable if only one LED in the circuit is faulty. With this method of checking, it is necessary to take into account that if the driver does not provide galvanic isolation from the electrical network, as for example in the diagrams above, then touching the LED solders with your hand is unsafe.

If one or even several LEDs turn out to be faulty and there is nothing to replace them with, then you can simply short-circuit the contact pads to which the LEDs were soldered. The light bulb will work with the same success, only the luminous flux will decrease slightly.

Other malfunctions of LED lamps

If checking the LEDs showed their serviceability, then the reason for the light bulb’s inoperability lies in the driver or in the soldering areas of the current-carrying conductors.

For example, in this light bulb a cold solder connection was found on the conductor supplying power to the printed circuit board. The soot released due to poor soldering even settled on the conductive paths of the printed circuit board. The soot was easily removed by wiping with a rag soaked in alcohol. The wire was soldered, stripped, tinned and re-soldered into the board. I was lucky with the repair of this light bulb.

Of the ten failed bulbs, only one had a faulty driver and a broken diode bridge. The driver repair consisted of replacing the diode bridge with four IN4007 diodes, designed for reverse voltage 1000 V and current 1 A.

Soldering SMD LEDs

To replace a faulty LED, it must be desoldered without damaging the printed conductors. The LED from the donor board also needs to be desoldered for replacement without damage.

It is almost impossible to desolder SMD LEDs with a simple soldering iron without damaging their housing. But if you use a special tip for a soldering iron or put an attachment made of copper wire on a standard tip, then the problem can be easily solved.

LEDs have polarity and when replacing, you need to install it correctly on the printed circuit board. Typically, printed conductors follow the shape of the leads on the LED. Therefore, a mistake can only be made if you are inattentive. To seal an LED, it is enough to install it on a printed circuit board and heat its ends with the contact pads with a 10-15 W soldering iron.

If the LED burns out like carbon, and the printed circuit board underneath is charred, then before installing a new LED, you must clean this area of ​​the printed circuit board from burning, since it is a current conductor. When cleaning, you may find that the LED solder pads are burnt or peeled off.

In this case, the LED can be installed by soldering it to adjacent LEDs if the printed traces lead to them. To do this, you can take a piece of thin wire, bend it in half or three times, depending on the distance between the LEDs, tin it and solder it to them.

Repair of LED lamp series "LL-CORN" (corn lamp)
E27 4.6W 36x5050SMD

The design of the lamp, which is popularly called a corn lamp, shown in the photo below differs from the lamp described above, therefore the repair technology is different.

The design of LED SMD lamps of this type is very convenient for repair, since there is access to test the LEDs and replace them without disassembling the lamp body. True, I still disassembled the light bulb for fun in order to study its structure.

Checking the LEDs of an LED corn lamp is no different from the technology described above, but we must take into account that the SMD5050 LED housing contains three LEDs at once, usually connected in parallel (three dark points of the crystals are visible on the yellow circle), and during testing all three should glow.

A faulty LED can be replaced with a new one or short-circuited with a jumper. This will not affect the reliability of the lamp, only the luminous flux will decrease slightly, unnoticeably to the eye.

The driver for this lamp is assembled using the simplest scheme, without an isolating transformer, so touching the LED terminals when the lamp is on is unacceptable. Lamps of this design must not be installed in lamps that can be reached by children.

If all the LEDs are working, it means the driver is faulty, and the lamp will have to be disassembled to get to it.

To do this, you need to remove the rim from the side opposite the base. Using a small screwdriver or a knife blade, try in a circle to find the weak spot where the rim is glued the worst. If the rim gives way, then using the tool as a lever, the rim will easily come off around the entire perimeter.

The driver was assembled according to the electrical circuit, like the MR-16 lamp, only C1 had a capacity of 1 µF, and C2 - 4.7 µF. Due to the fact that the wires going from the driver to the lamp base were long, the driver was easily removed from the lamp body. After studying its circuit diagram, the driver was inserted back into the housing, and the bezel was glued into place with transparent Moment glue. The failed LED was replaced with a working one.

Repair of LED lamp "LL-CORN" (corn lamp)
E27 12W 80x5050SMD

When repairing a more powerful lamp, 12 W, there were no failed LEDs of the same design and in order to get to the drivers, we had to open the lamp using the technology described above.

This lamp gave me a surprise. The wires leading from the driver to the socket were short, and it was impossible to remove the driver from the lamp body for repair. I had to remove the base.

The lamp base was made of aluminum, cored around the circumference and held tightly. I had to drill out the mounting points with a 1.5 mm drill. After this, the base, pryed off with a knife, was easily removed.

But you can do without drilling the base if you use the edge of a knife to pry it around the circumference and slightly bend its upper edge. You should first put a mark on the base and body so that the base can be conveniently installed in place. To securely fasten the base after repairing the lamp, it will be enough to put it on the lamp body in such a way that the punched points on the base fall into the old places. Next, press these points with a sharp object.

Two wires were connected to the thread with a clamp, and the other two were pressed into the central contact of the base. I had to cut these wires.

As expected, there were two identical drivers, feeding 43 diodes each. They were covered with heat shrink tubing and taped together. In order for the driver to be placed back into the tube, I usually carefully cut it along the printed circuit board from the side where the parts are installed.

After repair, the driver is wrapped in a tube, which is fixed with a plastic tie or wrapped with several turns of thread.

In the electrical circuit of the driver of this lamp, protection elements are already installed, C1 for protection against pulse surges and R2, R3 for protection against current surges. When checking the elements, resistors R2 were immediately found to be open on both drivers. It appears that the LED lamp was supplied with a voltage that exceeded the permissible voltage. After replacing the resistors, I didn’t have a 10 ohm one at hand, so I set it to 5.1 ohms, and the lamp started working.

Repair of LED lamp series "LLB" LR-EW5N-5

The appearance of this type of light bulb inspires confidence. Aluminum body, high quality workmanship, beautiful design.

The design of the light bulb is such that disassembling it without the use of significant physical effort is impossible. Since the repair of any LED lamp begins with checking the serviceability of the LEDs, the first thing we had to do was remove the plastic protective glass.

The glass was fixed without glue on a groove made in the radiator with a collar inside it. To remove the glass, you need to use the end of a screwdriver, which will go between the fins of the radiator, to lean on the end of the radiator and, like a lever, lift the glass up.

Checking the LEDs with a tester showed that they are working properly, therefore, the driver is faulty and we need to get to it. The aluminum board was secured with four screws, which I unscrewed.

But contrary to expectations, behind the board there was a radiator plane, lubricated with heat-conducting paste. The board had to be returned to its place and the lamp continued to be disassembled from the base side.

Due to the fact that the plastic part to which the radiator was attached was held very tightly, I decided to go the proven route, remove the base and remove the driver through the opened hole for repair. I drilled out the core points, but the base was not removed. It turned out that it was still attached to the plastic due to the threaded connection.

I had to separate the plastic adapter from the radiator. It held up just like the protective glass. To do this, a cut was made with a hacksaw for metal at the junction of the plastic with the radiator and by turning a screwdriver with a wide blade, the parts were separated from each other.

After unsoldering the leads from the LED printed circuit board, the driver became available for repair. The driver circuit turned out to be more complex than previous light bulbs, with an isolation transformer and a microcircuit. One of electrolytic capacitors 400 V 4.7 µF was swollen. I had to replace it.

A check of all semiconductor elements revealed a faulty Schottky diode D4 (pictured below on the left). There was an SS110 Schottky diode on the board, which was replaced with an existing analog 10 BQ100 (100 V, 1 A). The forward resistance of Schottky diodes is two times less than that of ordinary diodes. The LED light came on. The second light bulb had the same problem.

Repair of LED lamp series "LLB" LR-EW5N-3

This LED lamp is very similar in appearance to the "LLB" LR-EW5N-5, but its design is slightly different.

If you look closely, you can see that at the junction between the aluminum radiator and the spherical glass, unlike the LR-EW5N-5, there is a ring in which the glass is secured. To remove the protective glass, use a small screwdriver to pry it at the junction with the ring.

Three nine super-bright crystal LEDs are installed on an aluminum printed circuit board. The board is screwed to the heatsink with three screws. Checking the LEDs showed their serviceability. Therefore, the driver needs to be repaired. Having experience in repairing a similar LED lamp "LLB" LR-EW5N-5, I did not unscrew the screws, but unsoldered the current-carrying wires coming from the driver and continued disassembling the lamp from the base side.

The plastic connecting ring between the base and the radiator was removed with great difficulty. At the same time, part of it broke off. As it turned out, it was screwed to the radiator with three self-tapping screws. The driver was easily removed from the lamp body.

The screws that fasten the plastic ring of the base are covered by the driver, and it is difficult to see them, but they are on the same axis with the thread to which the transition part of the radiator is screwed. Therefore, you can reach them with a thin Phillips screwdriver.

The driver turned out to be assembled according to a transformer circuit. Checking all elements except the microcircuit did not reveal any failures. Consequently, the microcircuit is faulty; I couldn’t even find a mention of its type on the Internet. The LED light bulb could not be repaired; it will be useful for spare parts. But I studied its structure.

Repair of LED lamp series "LL" GU10-3W

At first glance, it turned out to be impossible to disassemble a burnt-out GU10-3W LED light bulb with protective glass. An attempt to remove the glass resulted in its chipping. When great force was applied, the glass cracked.

By the way, in the lamp marking, the letter G means that the lamp has a pin base, the letter U means that the lamp belongs to the class of energy-saving light bulbs, and the number 10 means the distance between the pins in millimeters.

LED light bulbs with a GU10 base have special pins and are installed in a socket with a rotation. Thanks to the expanding pins, the LED lamp is pinched in the socket and held securely even when shaking.

In order to disassemble this LED light bulb, I had to drill a hole with a diameter of 2.5 mm in its aluminum case at the level of the surface of the printed circuit board. The drilling location must be chosen in such a way that the drill does not damage the LED when exiting. If you don’t have a drill at hand, you can make a hole with a thick awl.

Next, a small screwdriver is inserted into the hole and, acting like a lever, the glass is lifted. I removed the glass from two light bulbs without any problems. If checking the LEDs with a tester shows their serviceability, then the printed circuit board is removed.

After separating the board from the lamp body, it immediately became obvious that the current-limiting resistors had burned out in both one and the other lamp. The calculator determined their nominal value from the stripes, 160 Ohms. Since the resistors burned out in LED bulbs of different batches, it is obvious that their power, judging by the size of 0.25 W, does not correspond to the power released when the driver operates at the maximum ambient temperature.

The driver circuit board was well filled with silicone, and I did not disconnect it from the board with the LEDs. I cut off the leads of the burnt resistors at the base and soldered them to more powerful resistors that were on hand. In one lamp I soldered a 150 Ohm resistor with a power of 1 W, in the second two in parallel with 320 Ohms with a power of 0.5 W.

In order to prevent accidental contact of the resistor terminal, to which the mains voltage is connected, with the metal body of the lamp, it was insulated with a drop of hot-melt adhesive. It is waterproof and an excellent insulator. I often use it to seal, insulate and secure electrical wires and other parts.

Hot-melt adhesive is available in the form of rods with a diameter of 7, 12, 15 and 24 mm different colors, from transparent to black. It melts, depending on the brand, at a temperature of 80-150°, which allows it to be melted using an electric soldering iron. It is enough to cut off a piece of the rod, place it in in the right place and heat. Hot-melt glue will acquire the consistency of May honey. After cooling it becomes hard again. When reheated, it becomes liquid again.

After replacing the resistors, the functionality of both bulbs was restored. All that remains is to secure the printed circuit board and protective glass in the lamp body.

When repairing LED lamps, I used liquid nails “Mounting” to secure printed circuit boards and plastic parts. The glue is odorless, adheres well to the surfaces of any materials, remains plastic after drying, and has sufficient heat resistance.

It is enough to take a small amount of glue on the end of a screwdriver and apply it to the places where the parts come into contact. After 15 minutes the glue will already hold.

When gluing the printed circuit board, in order not to wait, holding the board in place, since the wires were pushing it out, I additionally fixed the board at several points using hot glue.

The LED lamp began to flash like a strobe light

I had to repair a couple of LED lamps with drivers assembled on a microcircuit, the malfunction of which was the light blinking at a frequency of about one hertz, like in a strobe light.

One instance of the LED lamp began to blink immediately after being turned on for the first few seconds and then the lamp began to shine normally. Over time, the duration of the lamp's blinking after switching on began to increase, and the lamp began to blink continuously. The second instance of the LED lamp suddenly began blinking continuously.

After disassembling the lamps, it turned out that the electrolytic capacitors installed immediately after the rectifier bridges in the drivers had failed. It was easy to determine the malfunction, since the capacitor housings were swollen. But even if the capacitor looks free of external defects in appearance, then the repair of an LED light bulb with a stroboscopic effect must still begin with its replacement.

After replacing the electrolytic capacitors with working ones, the stroboscopic effect disappeared and the lamps began to shine normally.

Online calculators for determining resistor values
by color marking

When repairing LED lamps, it becomes necessary to determine the resistor value. According to the standard, modern resistors are marked by applying colored rings to their bodies. 4 colored rings are applied to simple resistors, and 5 to high-precision resistors.

LEDs occupy the leading position among the most effective sources of artificial light today. This is largely due to the high-quality power sources for them. When working in conjunction with a properly selected driver, the LED will maintain stable light brightness for a long time, and the service life of the LED will be very, very long, measured in tens of thousands of hours.

Thus, a correctly selected driver for LEDs is the key to long and reliable operation of the light source. And in this article we will try to cover the topic of how to choose the right driver for an LED, what to look for, and what they generally are.

An LED driver is a stabilized constant voltage or constant current power supply. In general, initially, an LED driver is a , but today even constant voltage sources for LEDs are called LED drivers. That is, we can say that the main condition is stable DC power characteristics.

An electronic device (essentially a stabilized pulse converter) is selected for the required load, be it a set of individual LEDs assembled in a series chain, or a parallel set of such chains, or maybe a strip or even one powerful LED.

A stabilized constant voltage power supply is well suited for LED strips, or for powering a set of several high-power LEDs connected one at a time in parallel - that is, when the rated voltage of the LED load is precisely known, and it is only necessary to select a power supply for the rated voltage at the corresponding maximum power .

Usually this does not cause problems, for example: 10 LEDs at 12 volts, 10 watts each, will require a 100 watt 12 volt power supply, rated for a maximum current of 8.3 amperes. All that remains is to adjust the output voltage using the adjusting resistor on the side, and you’re done.

For more complex LED assemblies, especially when several LEDs are connected in series, you need not just a power supply with a stabilized output voltage, but a full-fledged LED driver - an electronic device with a stabilized output current. Here, current is the main parameter, and the supply voltage of the LED assembly can automatically vary within certain limits.

For an even glow of the LED assembly, it is necessary to ensure the rated current through all the crystals, however, the voltage drop across the crystals may differ for different LEDs (since the I-V characteristics of each of the LEDs in the assembly are slightly different), so the voltage will not be the same on each LED, but the current should be the same.

LED drivers are produced mainly for power supply from a 220 volt network or from a 12 volt vehicle on-board network. The driver output parameters are specified in the form of voltage range and rated current.

For example, a driver with an output of 40-50 volts, 600 mA will allow you to connect four 12-volt LEDs with a power of 5-7 watts in series. Each LED will drop approximately 12 volts, the current through the series chain will be exactly 600 mA, while the voltage of 48 volts falls within the operating range of the driver.

A driver for LEDs with stabilized current is a universal power supply for LED assemblies, and its efficiency is quite high and here's why.

The power of the LED assembly is an important criterion, but what determines this load power? If the current were not stabilized, then a significant part of the power would be dissipated on the equalizing resistors of the assembly, that is, the efficiency would be low. But with a current-stabilized driver, equalizing resistors are not needed, and the resulting efficiency of the light source will be very high.

Drivers from different manufacturers differ in output power, protection class and used element base. As a rule, it is based on current output stabilization and protection against short circuit and overload.

Powered by 220 volt AC or 12 volt DC. The simplest compact drivers with low-voltage power supply can be implemented on a single universal chip, but their reliability, due to simplification, is lower. Nevertheless, such solutions are popular in auto tuning.

When choosing a driver for LEDs, you should understand that the use of resistors does not protect against interference, nor does the use of simplified circuits with quenching capacitors. Any voltage surges pass through resistors and capacitors, and the nonlinear I-V characteristic of the LED will certainly be reflected in the form of a current surge through the crystal, and this is harmful for the semiconductor. Linear stabilizers are also not the best option in terms of immunity to interference, and the efficiency of such solutions is lower.

It is best if the exact number, power, and switching circuit of the LEDs are known in advance, and all LEDs in the assembly will be the same model and from the same batch. Then select the driver.

The range of input voltages, output voltages, and rated current must be indicated on the case. Based on these parameters, a driver is selected. Pay attention to the protection class of the housing.

For research tasks, for example, packageless LED drivers are suitable; such models are widely represented on the market today. If you need to place the product in a housing, the user can make the housing independently.

Andrey Povny

I have published several reviews of LEDs, it’s time to write what you can feed them.
There are three items of parts involved in the review (links and prices are present), but they are all needed for one purpose, to make a driver for an LED.

I immediately apologize for the title photo, it stubbornly tries to scale in its own way, I couldn’t fix it, a more correct one is on the seller’s page.

Everyone knows that LEDs are powered by current, preferably stabilized, so that the brightness does not change when the voltage changes. A driver, essentially a current stabilizer, serves this purpose.
You can limit the current with simple microcircuits like LM317 and current stabilizers specially designed for this (there is a review of one such part on Muska), but they usually emit quite a lot of heat, since they have low efficiency. But the advantage of LEDs is precisely their high efficiency.
More interesting are pulse stabilizers current, they are more complicated, but they have much greater efficiency, especially if the supply voltage is very different from the voltage on the LED.
Yes, many will say that it is easier to buy such a driver in China and not bother, I agree.
But it’s always more pleasant to do something with your own hands. Actually, that’s what I decided when ordering components for the driver.
Maybe I'm reinventing the wheel. But the review includes components that are useful for many other tasks, and perhaps many will find useful information about what they sell and what we actually get.

I'll start with the microcircuit itself. This is the PT4115, which is quite well known to LED enthusiasts. description -
The chip has a pin for brightness control. The input, as far as I understand, can be controlled by PWM or by changing the voltage. The input is quite high-impedance, since when this pin was touched, the LED began to flicker at a frequency of 100 Hz.

The cost of a lot of 10 pieces is $2.
After ordering the microcircuit, the seller wrote that the parcel would be without a track and asked if this would suit me, I decided that 2 dollars was not the money to worry too much about and gave the go-ahead.
After some time, I found an envelope in the mailbox.

Inside was a bag with the microcircuits I needed.

I checked one microcircuit, connecting it with a hinged mounting, wrote to the seller that everything was in order, confirmed receipt and began to wait for the rest of the parts.

After that came the chokes.
The cost of a lot of 20 pieces is $7.36.

They have already been delivered to my home (as well as the next order).
They were packed in a cardboard box, although such a measure seems unnecessary to me.
By the way, in our country such chokes are much more expensive, and I bought them not only for this.

The chokes themselves, inductance 68 µH, current 1.6 or 1.8 Amperes (not specified by the seller, therefore approximate), dimensions 12x12x7mm.

The inductance measurement showed a deviation within the error.

Similar to the first case, I confirmed the order and left a good review.

Well, at the end came Schottky diodes. Since this is a necessary item for household use, I ordered a hundred of them.
I wanted more, but didn't take the risk.

The price of a lot of 100 pieces is $5.26. They are also more expensive here.

The diodes are marked as SS34, in fact they are smaller, in terms of dimensions and characteristics they fully correspond to SS24 diodes.
I measured the voltage drop across the diode at a current of 1 Ampere and I was satisfied with it.

This is where some of the purchases on Aliexpress ended.
In principle, the review could have ended here, but it would have been wrong to buy parts and not try them out. Therefore, it was naturally decided to bring the matter to some logical conclusion.

When I was on our market, I simultaneously bought 1206 smd resistors with a resistance of 1 ohm for a current sensor.
At first I thought about buying low-resistance resistors right away, as in the datasheet for the microcircuit, but they are much more expensive and if you want to configure them for different currents, you have to buy several values, in general it’s inconvenient, and I sometimes use 1 Ohm resistors anyway.
in the end it turned out that 1 such resistor approximately corresponds to a current of 0.1 Ampere, two in parallel 0.2 Ampere, etc. SMD resistors and capacitors are conveniently soldered to each other so you can easily select the required current.
I had capacitors for the input power filter and trimmings of PCB, but nothing else is needed.

Well, in general, I began to reinvent my bicycle driver. I threw on a quick scarf in Sprint, the diagram was from the datasheet, so I didn’t have to come up with anything.
I picked up a piece of PCB to make 5 boards at once (I plan to convert 5 halogen lamps to LEDs).

Some photos of the process and a diagram

Transferred to textolite.

I etched it, drilled holes, cut it into separate scarves, tinned the paths and washed it of flux residues.

Assembled all the necessary components

The result was a board like this, it is larger in size than those sold by the Chinese, but it has a more powerful choke and two parallel diodes, correspondingly lower losses and greater reliability, and the dimensions were completely uncritical to me.

After this, I naturally wanted to check it out (where would I do without it).
I checked with these LEDs -

Along the way, it turned out that the microcircuit stabilizes the current normally, but still, with a one-and-a-half-fold increase in the input voltage, the output current changes, at least slightly.
But I am a little guilty that there may be a large error due to the pulsating current (the output current was measured in series with the LED).
It was possible, of course, to measure the current using a resistor and an oscilloscope, but I considered this unnecessary, since the transition from linear mode to current limiting, and the subsequent transition to stabilization mode in the mode with PWM stabilization, was clearly visible.

The shunt rating was 1/6 = 0.166 Ohm.

With such parameters at the input, the output current was 0.7 Amperes.

With such output current was 0.65 Ampere

Before the threshold voltage for switching to PWM stabilization mode, I received the maximum current -

With a gradual increase in the supply voltage, the input current first gradually increased, after switching to the stabilization mode and further increasing, it began to gradually fall, which indicates the operation of PWM stabilization.
By the way, with a very smooth increase in the supply voltage, a transition is noticeable; the brightness of the LED first gradually increases, after the transition it abruptly decreases by 10 percent, after which (with a further increase in the input voltage) it does not change anymore.
Apparently this is how the microcircuit processes the inclusion of PWM stabilization.
Heating at a current of 600 mA is practically not felt, there is nothing to measure without contact, and contact measurement will introduce a large error.
I tried to give the output 1 Ampere, the heating certainly increased, but not much. and only the microcircuit was heated. Overall I was pleased.

Ask why you didn’t buy something ready-made on Ali?
-The details will be useful in other crafts.
-I wanted to “stretch my hands” a little.
-The costs for all components turned out to be approximately $1 per board.
-I decided to test not the finished device, but the parts, since they are used not only in drivers.
-As a result, I received a device that is more reliable than what is offered in Chinese stores.

I really hope that this review will be useful.