Let's consider ways to connect medium-power ice diodes to the most popular ratings of 5V, 12 volts, 220V. Then they can be used in the manufacture of color and music devices, signal level indicators, smooth switching on and off. I’ve been planning to make a smooth artificial dawn for a long time in order to maintain my daily routine. In addition, dawn emulation allows you to wake up much better and easier.
Drivers with power supply from 5V to 30V
If you have a suitable power source from any household appliance, then it is better to use a low-voltage driver to turn it on. They can be up or down. A booster will make even 1.5V 5V so that the LED circuit works. A step-down from 10V-30V will make a lower one, for example 15V.
They are sold in a large variety by the Chinese; the low-voltage driver differs in two regulators from a simple Volt stabilizer.
The actual power of such a stabilizer will be lower than what the Chinese indicated. In the module parameters, they write the characteristics of the microcircuit and not the entire structure. If there is a large radiator, then such a module will handle 70% - 80% of what was promised. If there is no radiator, then 25% - 35%.
Particularly popular are models based on LM2596, which are already quite outdated due to low efficiency. They also get very hot, so without a cooling system they do not hold more than 1 Ampere.
XL4015, XL4005 are more efficient, the efficiency is much higher. Without a cooling radiator, they can withstand up to 2.5A. There are very miniature models based on MP1584 measuring 22mm by 17mm.
Turn on 1 diode
The most commonly used are 12 volts, 220 volts and 5V. This is how low-power LED lighting of 220V wall switches is made. Factory standard switches most often have a neon lamp installed.
Parallel connection
When connecting in parallel, it is advisable to use a separate resistor for each series circuit of diodes in order to obtain maximum reliability. Another option is to put one powerful resistor on several LEDs. But if one LED fails, the current on the remaining ones will increase. By whole it will be higher than the nominal or specified value, which will significantly reduce the resource and increase heating.
The rationality of using each method is calculated based on the requirements for the product.
Serial connection
Serial connection when powered from 220V is used in filament diodes and LED strips at 220 volts. In a long chain of 60-70 LEDs, each one drops 3V, which allows it to be connected directly to high voltage. Additionally, only a current rectifier is used to obtain plus and minus.
This connection is used in any lighting technology:
- LED lamps for home;
- led lamps;
- New Year's garlands for 220V;
- LED strips 220.
Lamps for the home usually use up to 20 LEDs connected in series; the voltage across them is about 60V. The maximum quantity is used in Chinese corn light bulbs, from 30 to 120 LED pieces. Corns do not have a protective flask, so the electrical contacts on which up to 180V are completely open.
Be careful if you see a long series string, and they are not always grounded. My neighbor grabbed the corn with his bare hands and then recited fascinating poems from bad words.
RGB LED connection
Low-power three-color RGB LEDs consist of three independent crystals located in one housing. If 3 crystals (red, green, blue) are turned on simultaneously, we get white light.
Each color is controlled independently of the others using an RGB controller. The control unit has ready-made programs and manual modes.
Turning on COB diodes
The connection diagrams are the same as for single-chip and three-color LEDs SMD5050, SMD 5630, SMD 5730. The only difference is that instead of 1 diode, a series circuit of several crystals is included.
Powerful LED matrices contain many crystals connected in series and in parallel. Therefore, power is required from 9 to 40 volts, depending on the power.
Connecting SMD5050 for 3 crystals
The SMD5050 differs from conventional diodes in that it consists of 3 white light crystals, and therefore has 6 legs. That is, it is equal to three SMD2835 made on the same crystals.
When connected in parallel using one resistor, reliability will be lower. If one of the crystals fails, the current through the remaining 2 increases. This leads to accelerated burnout of the remaining ones.
By using a separate resistance for each crystal, the above disadvantage is eliminated. But at the same time, the number of resistors used increases by 3 times and the LED connection circuit becomes more complex. Therefore, it is not used in LED strips and lamps.
LED strip 12V SMD5630
A clear example of connecting an LED to 12 volts is an LED strip. It consists of sections of 3 diodes and 1 resistor connected in series. Therefore, it can only be cut in the indicated places between these sections.
LED strip RGB 12V SMD5050
RGB tape uses three colors, each is controlled separately, and a resistor is installed for each color. You can cut only at the indicated location, so that each section has 3 SMD5050 and can be connected to 12 volts.
LEDs for their power supply require the use of devices that will stabilize the current passing through them. In the case of indicator and other low-power LEDs, you can get by with resistors. Their simple calculation can be further simplified by using the LED Calculator.
To use high-power LEDs, you cannot do without using current-stabilizing devices - drivers. The right drivers have a very high efficiency - up to 90-95%. In addition, they provide stable current even when the power supply voltage changes. And this may be relevant if the LED is powered, for example, by batteries. The simplest current limiters - resistors - cannot provide this by their nature.
You can learn a little about the theory of linear and pulsed current stabilizers in the article “Drivers for LEDs”.
Of course, you can buy a ready-made driver. But it’s much more interesting to make it yourself. This will require basic skills in reading electrical diagrams and using a soldering iron. Let's look at a few simple homemade driver circuits for high-power LEDs.
Simple driver. Assembled on a breadboard, powers the mighty Cree MT-G2
A very simple linear driver circuit for an LED. Q1 – N-channel field-effect transistor of sufficient power. Suitable, for example, IRFZ48 or IRF530. Q2 is a bipolar NPN transistor. I used 2N3004, you can use any similar one. Resistor R2 is a 0.5-2W resistor that will determine the driver current. Resistance R2 2.2Ohm provides a current of 200-300mA. The input voltage should not be very high - it is advisable not to exceed 12-15V. The driver is linear, so the driver efficiency will be determined by the ratio V LED / V IN, where V LED is the voltage drop across the LED, and V IN is the input voltage. The greater the difference between the input voltage and the drop across the LED and the greater the driver current, the more the transistor Q1 and resistor R2 will heat up. However, V IN should be greater than V LED by at least 1-2V.
For tests, I assembled the circuit on a breadboard and powered it with a powerful CREE MT-G2 LED. The power supply voltage is 9V, the voltage drop across the LED is 6V. The driver worked immediately. And even with such a small current (240mA), the mosfet dissipates 0.24 * 3 = 0.72 W of heat, which is not small at all.
The circuit is very simple and can even be mounted in a finished device.
The circuit of the next homemade driver is also extremely simple. It involves the use of a step-down voltage converter chip LM317. This microcircuit can be used as a current stabilizer.
An even simpler driver on the LM317 chip
The input voltage can be up to 37V, it must be at least 3V higher than the voltage drop across the LED. The resistance of resistor R1 is calculated by the formula R1 = 1.2 / I, where I is the required current. The current should not exceed 1.5A. But at this current, resistor R1 should be able to dissipate 1.5 * 1.5 * 0.8 = 1.8 W of heat. The LM317 chip will also get very hot and will not be possible without a heatsink. The driver is also linear, so in order for the efficiency to be maximum, the difference between V IN and V LED should be as small as possible. Since the circuit is very simple, it can also be assembled by hanging installation.
On the same breadboard, a circuit was assembled with two one-watt resistors with a resistance of 2.2 Ohms. The current strength turned out to be less than the calculated one, since the contacts in the breadboard are not ideal and add resistance.
The next driver is a pulse buck driver. It is assembled on the QX5241 chip.
The circuit is also simple, but consists of a slightly larger number of parts and here you can’t do without making a printed circuit board. In addition, the QX5241 chip itself is made in a fairly small SOT23-6 package and requires attention when soldering.
The input voltage should not exceed 36V, the maximum stabilization current is 3A. The input capacitor C1 can be anything - electrolytic, ceramic or tantalum. Its capacity is up to 100 µF, the maximum operating voltage is no less than 2 times greater than the input. Capacitor C2 is ceramic. Capacitor C3 is ceramic, capacity 10 μF, voltage - no less than 2 times greater than the input. Resistor R1 must have a power of at least 1W. Its resistance is calculated by the formula R1 = 0.2 / I, where I is the required driver current. Resistor R2 - any resistance 20-100 kOhm. The Schottky diode D1 must withstand the reverse voltage with a reserve - at least 2 times the value of the input. And it must be designed for a current not less than the required driver current. One of the most important elements of the circuit is field-effect transistor Q1. This should be an N-channel field device with the minimum possible resistance in the open state; of course, it should withstand the input voltage and the required current strength with a reserve. A good option is field-effect transistors SI4178, IRF7201, etc. Inductor L1 should have an inductance of 20-40 μH and a maximum operating current not less than the required driver current.
The number of parts of this driver is very small, all of them are compact in size. The result may be a fairly miniature and, at the same time, powerful driver. This is a pulse driver, its efficiency is significantly higher than that of linear drivers. However, it is recommended to select an input voltage that is only 2-3V higher than the voltage drop across the LEDs. The driver is also interesting because output 2 (DIM) of the QX5241 chip can be used for dimming - regulating the driver current and, accordingly, the brightness of the LED. To do this, pulses (PWM) with a frequency of up to 20 KHz must be supplied to this output. Any suitable microcontroller can handle this. The result may be a driver with several operating modes.
(13 ratings, average 4.58 out of 5)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 start repairing an LED lamp, you need to understand its structure. 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, the electrical circuits of LED lamp drivers are galvanically connected to the phase of the electrical network and therefore care should be taken. Touching exposed parts of a circuit connected to an electrical outlet may result in electric shock.
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.
On the reverse side of the driver board, a diode bridge and two series-connected resistors with a nominal value of 510 kOhm were installed.
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.
Once assembled, the LED lamp consistently emitted light despite being hit 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-scattering 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 the appearance of the 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 together with quick-drying “Moment” superglue, the seams were smoothed by melting the plastic with a soldering iron and smoothed 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 and 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 efficiency of the driver assembled according to this scheme will be low and the power loss 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 resistor driver will consume power that exceeds the power consumption of LEDs and placing it in a small LED lamp housing will be unacceptable due to the release of more heat.
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 marked the faulty LEDs with crosses so that they were 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 a reverse voltage of 1000 V and a current of 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 is different 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 it must be taken into account that the SMD5050 LED housing contains three LEDs at once, usually connected in parallel (three dark dots 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 of this lamp is assembled according to the simplest circuit, 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 the 400 V 4.7 µF electrolytic capacitors was swollen. I had to replace it.
A check of all semiconductor elements revealed a faulty Schottky diode D4 (pictured below 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 crystal super-bright 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 in 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 a piece of the rod, place it in the right place and heat it. 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.
I am publishing the third article today. 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.
Subscribe! It will be interesting.
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 (on the reverse side either). 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 is a large selection there. 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 switching circuit and microcircuit parameters for drivers of LED modules and matrices., pdf, 661.17 kB, downloaded: 1882 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: 852 times./
/ Technical information on high-power LEDs for headlights and spotlights, pdf, 1.82 MB, downloaded: 1083 times./
Special thanks to those who have circuits of real LED drivers for the collection. I will publish them in this article.
Author's note: “There is a fairly large amount of information on the Internet about the power supply of LED products, but when I was preparing material for this article, I found a large amount of absurd information on sites from the top search engine results. In this case, there is either a complete absence or incorrect perception of basic theoretical information and concepts.”
LEDs are the most efficient of all common light sources today. Behind the efficiency there are also problems, for example, a high requirement for the stability of the current that powers them, poor tolerance of complex thermal operating conditions (at elevated temperatures). Hence the task of solving these problems. Let's see how the concepts of power supply and driver differ. First, let's delve into the theory.
Current source and voltage source
power unit is a generalized name for a part of an electronic device or other electrical equipment that supplies and regulates electricity to power this equipment. It can be located both inside the device and outside, in a separate housing.
Driver- a generalized name for a specialized source, switch or power regulator for specific electrical equipment.
There are two main types of power supplies:
Voltage source.
Current source.
Let's look at their differences.
Voltage source- this is a power source whose output voltage does not change when the output current changes.
An ideal voltage source has zero internal resistance, but the output current can be infinitely large. In reality, the situation is different.
Any voltage source has internal resistance. In this regard, the voltage may deviate slightly from the nominal when connecting a powerful load (powerful - low resistance, high current consumption), and the output current is determined by its internal structure.
For a real voltage source, the emergency mode of operation is the short circuit mode. In this mode, the current increases sharply; it is limited only by the internal resistance of the power source. If the power supply does not have short circuit protection, it will fail
Current source- this is a power source whose current remains set regardless of the resistance of the connected load.
Since the purpose of a current source is to maintain a given current level. The emergency operating mode for it is idle mode.
To explain the reason in simple words, the situation is as follows: let’s say you connected a load with a resistance of 1 Ohm to a current source with a rated 1 Ampere, then the voltage at its output will be set to 1 Volt. A power of 1 W will be released.
If you increase the load resistance, say, to 10 Ohms, then the current will still be 1A, and the voltage will already be set at 10V. This means that 10W of power will be released. Conversely, if you reduce the resistance to 0.1 Ohm, the current will still be 1A, and the voltage will be 0.1V.
Idling is a state when nothing is connected to the terminals of the power source. Then we can say that at idle the load resistance is very large (infinite). The voltage will increase until a current of 1A flows. In practice, an example of such a situation is the ignition coil of a car.
The voltage on the electrodes of the spark plug, when the power circuit of the primary winding of the coil opens, increases until its value reaches the breakdown voltage of the spark gap, after which current flows through the resulting spark and the energy accumulated in the coil is dissipated.
A short circuit condition for a current source is not an emergency operation mode. During a short circuit, the load resistance of the power source tends to zero, i.e. it is infinitely small. Then the voltage at the output of the current source will be appropriate for the flow of a given current, and the released power will be negligible.
Let's move on to practice
If we talk about modern nomenclature or names that are given to power supplies more by marketers than by engineers, then power supply it is commonly called a voltage source.
These include:
Charger for a mobile phone (in them, the conversion of values until the required charging current and voltage is achieved is carried out by converters installed on the board of the device being charged.
Power supply for laptop.
Power supply for LED strip.
The driver is the current source. Its main use in everyday life is to power individual and both of them with ordinary high power from 0.5 W.
LED Power
At the beginning of the article it was mentioned that LEDs have very high power requirements. The fact is that the LED is powered by current. It's connected with . Look at her.
The picture shows the current-voltage characteristics of diodes of different colors:
This branch shape (close to a parabola) is due to the characteristics of semiconductors and the impurities that are introduced into them, as well as the features of the pn junction. The current, when the voltage applied to the diode is less than the threshold, almost does not increase, or rather its increase is negligible. When the voltage at the diode terminals reaches a threshold level, the current through the diode begins to increase sharply.
If the current through a resistor grows linearly and depends on its resistance and applied voltage, then the increase in current through a diode does not obey this law. And with an increase in voltage by 1%, the current can increase by 100% or more.
Plus to this: for metals, the resistance increases as its temperature increases, but for semiconductors, on the contrary, the resistance drops, and the current begins to increase.
To find out the reasons for this in more detail, you need to delve into the course “Physical Foundations of Electronics” and learn about the types of charge carriers, the band gap and other interesting things, but we will not do this, we briefly considered these issues.
In technical specifications, the threshold voltage is designated as the voltage drop in forward bias; for white LEDs it is usually about 3 volts.
At first glance, it may seem that at the stage of design and production of the lamp it is enough to set a stable voltage at the output of the power supply and everything will be fine. They do this on LED strips, but they are powered from stabilized power supplies, and besides, the power of the LEDs used in strips is often * small, tenths and hundredths of a watt.
If such an LED is powered by a driver with a stable output current, then when the LED heats up, the current through it will not increase, but will remain unchanged, and the voltage at its terminals will therefore decrease slightly.
And if from the power supply (voltage source), after heating the current will increase, which will make the heating even stronger.
There is one more factor - the characteristics of all LEDs (as well as other elements) are always different.
Driver selection: characteristics, connection
To choose the right driver, you need to familiarize yourself with its technical characteristics, the main ones are:
Rated output current;
Maximum power;
Minimum power. Not always indicated. The fact is that some drivers will not start if a load less than a certain power is connected to them.
Often in stores, instead of power, they indicate:
Rated output current;
Output voltage range in the form of (min.)V...(max.)V, for example 3-15V.
The number of connected LEDs depends on the voltage range, written in the form (min)...(max), for example 1-3 LEDs.
Since the current through all elements is the same when connected in series, therefore the LEDs are connected to the driver in series.
It is not advisable (or rather impossible) to connect LEDs in parallel to the driver, because the voltage drops on the LEDs may differ slightly and one will be overloaded, and the other, on the contrary, will operate in a mode below the nominal one.
It is not recommended to connect more LEDs than specified by the driver design. The fact is that any power source has a certain maximum permissible power, which cannot be exceeded. And for each LED connected to a source of stabilized current, the voltage at its outputs will increase by approximately 3V (if the LED is white), and the power will be equal to the product of current and voltage, as usual.
Based on this, we will draw conclusions: in order to buy the right driver for LEDs, you need to determine the current that the LEDs consume and the voltage that drops across them, and select the driver according to the parameters.
For example, this driver supports connecting up to 12 powerful 1W LEDs with a current consumption of 0.4A.
This one produces a current of 1.5A and a voltage from 20 to 39V, which means you can connect to it, for example, a 1.5A LED, 32-36V and a power of 50W.
Conclusion
A driver is one type of power supply designed to provide LEDs with a given current. In principle, it doesn’t matter what this power source is called. Power supplies are called power supplies for 12 or 24 Volt LED strips; they can supply any current below the maximum. Knowing the correct names, you are unlikely to make a mistake when purchasing a product in stores, and you will not have to change it.
