Y sbl ip20 driver 60w wiring diagram. Repair of LED led lamps, device, wiring diagrams

There are many different types of LED power supplies on the market today. This article is intended to make it easier for you to choose the source you need.

First of all, let's look at the difference between a standard power supply and an LED driver. First you need to decide - what is a power supply? In the general case, this is a power supply of any type, which is a separate functional unit. Usually it has certain input and output parameters, and it doesn’t matter what kind of devices it is intended to power. The driver for powering the LEDs provides a stable output current. In other words, this is also a power supply. The driver is just a marketing designation - to avoid confusion. Before the advent of LEDs, current sources - and they are the driver - were not widely used. But then a super-bright LED appeared - and the development of current sources went by leaps and bounds. And not to be confused - they are called drivers. So let's agree on some terms. The power supply is a source of voltage (constant voltage), the Driver is a source of current (constant current). The load is what we connect to the power supply or driver.

power unit

Most electrical appliances and electronic components require a voltage source to operate. They are the usual electrical network, which is present in any apartment in the form of a socket. Everyone knows the phrase "220 volts". As you can see - not a word about the current. This means that if the device is designed to operate from a 220 V network, then it does not matter to you how much current it consumes. If only there were 220 - and he will take the current himself - as much as he needs. For example, a conventional electric kettle with a power of 2 kW (2,000 W), connected to a 220 V network, consumes the following current: 2,000 / 220 = 9 amperes. Quite a lot, given that most conventional electrical power strips are rated at 10 amps. This is the reason for the frequent operation of the protection (machine) when the kettles are plugged into the outlet through an extension cord, into which many devices are already inserted - a computer, for example. And it's good if the protection works, otherwise the extension cord may simply melt. And so - any device designed to be plugged into an outlet - knowing what its power is, you can calculate the current consumed.
But most household devices, such as a TV, DVD player, computer, need to lower the mains voltage from 220 V to the level they need - for example, 12 volts. The power supply is just the device that deals with such a decrease.
There are many ways to lower the voltage of the network. The most common power supplies are transformer and switching.

Power supply based on transformer

Such a power supply is based on a large, iron, buzzing contraption. :) Well, current transformers buzz less. The main advantage is the simplicity and relative safety of such blocks. They contain a minimum of details, but at the same time they have good characteristics. The main disadvantage is efficiency and dimensions. The more powerful the power supply, the heavier it is. Part of the energy is spent on "humming" and heating :) In addition, part of the energy is lost in the transformer itself. In other words - simple, reliable, but has a lot of weight and consumes a lot - efficiency at the level of 50-70%. It has an important integral plus - galvanic isolation from the network. This means that if a malfunction occurs or you accidentally get into the secondary power circuit with your hand, you will not be shocked :) Another definite plus is that the power supply can be connected to the network without load - this will not harm it.
But let's see what happens if overload the power supply.
Available: transformer power supply with an output voltage of 12 volts and a power of 10 watts. Connect a 12 volt 5 watt light bulb to it. The light bulb will glow at all its 5 watts and consume current 5 / 12 \u003d 0.42 A.

Connect the second bulb in series to the first, like this:

Both bulbs will glow, but very dimly. When connected in series, the current in the circuit will remain the same - 0.42 A, but the voltage will be distributed between two bulbs, that is, each will receive 6 volts. It is clear that they will glow barely. Yes, and each will consume approximately 2.5 watts.
Now let's change the conditions - connect the bulbs in parallel:

As a result, the voltage on each lamp will be the same - 12 volts, but the current they will take is 0.42 A each. That is, the current in the circuit will double. Considering that we have a unit with a power of 10 W - it won’t seem enough to him - when connected in parallel, the load power, that is, the light bulbs, is summed up. If we also connect a third one, then the power supply will start to heat up wildly and eventually burn out, possibly taking your apartment with it. And all this because he does not know how to limit the current. Therefore, it is very important to correctly calculate the load on the power supply. Of course, more complex units contain overload protection and automatically turn off. But you should not count on this - protection, sometimes, also does not work.

Impulse power block

The simplest and brightest representative is Chinese power supply for halogen lamps 12 V. Contains few parts, light, small. The dimensions of the 150 W block are 100x50x50 mm, the weight is 100 grams. The same transformer power supply would weigh three kilograms, or even more. The power supply for halogen lamps also has a transformer, but it is small because it operates at an increased frequency. It should be noted that the efficiency of such a unit is also not up to par - about 70-80%, while it produces decent interference in the electrical network. There are many more blocks based on a similar principle - for laptops, printers, etc. So, the main advantage is small dimensions and low weight. Galvanic isolation is also present. The disadvantage is the same as that of its transformer counterpart. It can burn out from overload :) So if you decide to make 12 V halogen lighting at home, calculate the allowable load on each transformer.
It is desirable to create from 20 to 30% of the stock. That is, if you have a 150 W transformer, it’s better not to hang more than 100 W loads on it. And keep a close eye on the Ravshans if they make repairs for you. They should not be trusted to calculate power. It is also worth noting that the impulse blocks do not like switching on without load. That is why it is not recommended to leave cell phone chargers in the outlet after charging is complete. However, everyone does this, so most of the current impulse blocks contain protection against turning on without load.

These two simple members of the power supply family share a common task - providing the right voltage level to power the devices that are connected to them. As mentioned above, the devices themselves decide how much current they need.

Driver

In general driver is a current source for LEDs. For him, there is usually no "output voltage" parameter. Only output current and power. However, you already know how to determine the allowable output voltage - we divide the power in watts by the current in amperes.
In practice, this means the following. Suppose the driver parameters are as follows: current - 300 milliamps, power - 3 watts. Divide 3 by 0.3 - we get 10 volts. This is the maximum output voltage that the driver can provide. Suppose we have three LEDs, each rated at 300 mA, and the voltage across the diode should be about 3 volts. If we connect one diode to our driver, then the voltage at its output will be 3 volts, and the current will be 300 mA. Connect the second diode successively(see the example with lamps above) with the first - the output will be 6 volts 300 mA, connect the third - 9 volts 300 mA. If we connect the LEDs in parallel, then these 300 mA will be distributed between them approximately equally, that is, approximately 100 mA each. If we connect three-watt LEDs with a working current of 700 mA to a 300 mA driver, they will receive only 300 mA.
I hope the principle is clear. A working driver under no circumstances will give out more current than it is designed for - no matter how you connect the diodes. It should be noted that there are drivers that are designed for any number of LEDs, so long as their total power does not exceed the power of the driver, and there are those that are designed for a certain number - 6 diodes, for example. However, they allow some spread to a smaller side - you can connect five diodes or even four. efficiency universal drivers worse than their counterparts, designed for a fixed number of diodes due to some features of the operation of pulse circuits. Also, drivers with a fixed number of diodes usually contain protection against abnormal situations. If the driver is designed for 5 diodes, and you connected three, it is quite possible that the protection will work and the diodes will either not turn on or will blink, signaling an emergency mode. It should be noted that most drivers do not tolerate the connection to the supply voltage without load - in this they are very different from a conventional voltage source.

So, we have determined the difference between the power supply and the driver. Now let's look at the main types of LED drivers, starting with the simplest.

Resistor

This is the simplest LED driver. It looks like a barrel with two leads. The resistor can limit the current in the circuit by selecting the desired resistance. How to do this is described in detail in the article "Connecting LEDs in a car"
The disadvantage is low efficiency, lack of galvanic isolation. There is no way to reliably power an LED from a 220 V network through a resistor, although many household switches use a similar circuit.

capacitor circuit.

Similar to a resistor circuit. The disadvantages are the same. It is possible to make a capacitor circuit of sufficient reliability, but the cost and complexity of the circuit will greatly increase.

Chip LM317

This is the next member of the protozoan family drivers for LEDs. Details are in the aforementioned article about LEDs in cars. The disadvantage is low efficiency, a primary power source is required. The advantage is reliability, simplicity of the circuit.

Driver on chip type HV9910

This type of driver has gained considerable popularity due to the simplicity of the circuit, the low cost of components and small dimensions.
Advantage - versatility, accessibility. The disadvantage is that it requires skill and care during assembly. There is no galvanic isolation from the 220 V network. High impulse noise in the network. Low power factor.

Driver with low voltage input

This category includes drivers designed to be connected to a primary voltage source - a power supply or a battery. For example, these are drivers for LED lights or lamps designed to replace 12 V halogen ones. The advantage is small size and weight, high efficiency, reliability, and operational safety. The disadvantage is that a primary voltage source is required.

network driver

Completely ready to use and contain all the necessary elements to power the LEDs. The advantage is high efficiency, reliability, galvanic isolation, operational safety. The disadvantage is the high cost, difficult to obtain. They can be both in the case and without the case. The latter are usually used as part of lamps or other light sources.

Application of drivers in practice

Most people planning to use LEDs are making a common mistake. Buy yourself first LED, then under them is selected driver. This can be considered a mistake because at present there are not so many places where you can purchase a sufficient assortment of drivers. As a result, having the coveted LEDs in your hands, you are racking your brains - how to choose a driver from the available one. So you bought 10 LEDs - and there are only 9 drivers. And you have to rack your brains - what to do with this extra LED. Maybe it was easier to count on 9 at once. Therefore, driver selection should occur simultaneously with the selection of LEDs. Next, you need to take into account the features of the LEDs, namely the voltage drop across them. For example, a red 1 W LED has an operating current of 300 mA and a voltage drop of 1.8-2 V. The power consumed by it will be 0.3 x 2 \u003d 0.6 W. But a blue or white LED has a voltage drop of 3-3.4 V at the same current, that is, a power of 1 W. Therefore, a driver with a current of 300 mA and a power of 10 W will "pull" 10 white or 15 red LEDs. The difference is significant. A typical diagram for connecting 1 W LEDs to a driver with an output current of 300 mA looks like this:

For standard 1W LEDs, the negative terminal is larger than the positive one, so it is easy to distinguish it.

What if only 700mA drivers are available? Then you have to use even number of LEDs including two of them in parallel.

I want to note that many mistakenly assume that the operating current of 1 W of LEDs is 350 mA. It's not, 350mA is the MAXIMUM operating current. This means that when working for a long time it is necessary to use power supply with a current of 300-330 mA. The same is true for parallel connection - the current per LED should not exceed the specified figure of 300-330 mA. It does not mean at all that operating at increased current will cause the LED to fail. But with insufficient heat dissipation, each extra milliamp can reduce the service life. In addition, the higher the current, the lower the efficiency of the LED, which means that its heating is stronger.

When it comes to connecting an LED strip or modules designed for 12 or 24 volts, you need to take into account that the power supplies offered for them limit the voltage, not the current, that is, they are not drivers in the accepted terminology. This means, firstly, that you need to carefully monitor the load power connected to a particular power supply. Secondly, if the unit is not stable enough, the output voltage spike can kill your tape. It makes life a little easier that resistors are installed in the tapes and modules (clusters), which allow you to limit the current to a certain extent. I must say, the LED strip consumes a relatively large current. For example, smd 5050 tape, which has 60 LEDs per meter, consumes about 1.2 A per meter. That is, to power 5 meters, you need a power supply with a current of at least 7-8 amperes. At the same time, the tape itself will consume 6 amperes, and one or two amperes must be left in reserve so as not to overload the unit. And 8 amps is almost 100 watts. These blocks are not cheap.
Drivers are more optimal for connecting a tape, but finding such specific drivers is problematic.

Summing up, we can say that the choice of a driver for LEDs should be given no less, if not more attention than LEDs. Carelessness when choosing is fraught with failure of LEDs, drivers, excessive consumption and other delights :)

Yuri Ruban, Rubikon LLC, 2010 .

Today, probably, not a single apartment or private house can do without LED lighting. And street lighting is gradually changing to economical and durable LED-elements. But looking at today's topic of conversation, one asks - what does the driver have to do with it (from the English “driver” is translated that way)? This is the first question that comes to the mind of a person who is ignorant of the LED lighting device. In fact, without such a device, light diodes do not work with a voltage of 220 V. Today we will figure out what function the LED driver performs, how to connect this device and whether it is possible to make it yourself.

Read in the article:

Why do we need drivers for LEDs and what is it

The answer to the question, what is an LED driver, is quite simple. This is a device that stabilizes the voltage and gives it the characteristics that are needed for the operation of LED elements. To make it clearer, let's draw an analogy with the ballast of a fluorescent lamp, which also cannot work without additional equipment. The only difference is that the driver has a compact size and fits in the body of the light fixture. In fact, it can be called a stabilizing starting device or a frequency converter.

Where are stabilizing devices for LED elements used?

LED drivers for LEDs are used in various fields:

street lights;
household lighting lamps;
LED strips and various lighting;
office lamps with the form of fluorescent lamps.

Even car daytime running lights require the installation of such a device, but everything is much simpler here, you can get by with one resistor. And although the driver for an LED strip (for example) differs in characteristics from a light bulb voltage regulator, they perform the same function.

Working Principle of 220V LED Lamp Driver Circuit

The principle of operation of the device is to maintain a given current at the output voltage (regardless of its value). This is the difference from the stabilizing power supply, which is responsible for the voltage.

Considering the circuit, we see that the current, passing through the resistances, stabilizes, and the capacitor gives it the desired frequency. Then the rectifying diode bridge comes into play. We get a stabilized direct current on the LEDs, which is again limited by resistors.

Noteworthy Driver Features

The characteristics of the converters required in a particular case are determined based on the parameters of the LED consumers. The main ones are:

Driver Rated Power- this parameter must exceed the total power consumed by the light diodes that will be in its circuit.
Output voltage- depends on the magnitude of the voltage drop on each of the light diodes.
Rated current, which depends on the brightness of the glow and the power consumption of the element.

It is important to know! The voltage drop across an LED depends on its color. For example, if 16 red LEDs can be connected to a 12 V power supply, then the maximum number of green LEDs will be 9.

Separation of LED drivers by device type

Converters can be divided into two types - linear and pulse. Both types are applicable to light diodes, but the differences between them are noticeable both in cost and in technical characteristics.

Linear converters are characterized by simple design and low cost. But such drivers have a significant drawback - the ability to connect only low-power light elements. Part of the energy is spent on heat generation, which contributes to a decrease in the coefficient of performance (COP).

Pulse converters are based on the principle of pulse-width modulation (PWM) and during their operation, the magnitude of the output currents is determined by such a parameter as the duty cycle. This means that there is no change in the pulse frequency, but the duty cycle can vary by values from 10 to 80%. Such drivers allow you to extend the life of light diodes, but they have one drawback. During their operation, it is possible to induce electromagnetic interference. Let's try to figure out what it threatens a person with a simple example.

A person living in an apartment or house has a pacemaker installed. At the same time, a chandelier was installed in a small room with many devices operating on impulse ice drivers for. In this case, the pacemaker may begin to malfunction. Of course, this is exaggerated and to create such strong interference, you need a lot of lamps that are less than a meter away from the pacemaker, but there is still a risk.

How to choose a driver for an LED: some nuances

Before purchasing a converter, calculate the power consumed by the LEDs. The rated power of the device must exceed this figure by 25 ÷ 30%. Also, the stabilizer must match the output voltage.

If hidden placement is planned, it is better to choose a converter without a case - the cost will be lower with the same technical characteristics.

Important! Drivers made in China usually do not meet the declared characteristics. Don't skimp on purchasing a "made in" converter. It is better to give preference to the Russian manufacturer.

How to connect LED elements to the converter: methods and diagrams

LEDs are connected to the driver in two ways - in series or in parallel. For example, let's take 6 LED emitters with a voltage drop of 2 V. When connected in series, you need a driver for 12 V and 300 mA. In this case, the glow will be even for all elements.

By connecting the emitters in parallel in a group of 3, we get the opportunity to use a 6 V converter, but already at 600 mA. The problem is that due to the uneven voltage drop, one line will glow brighter than the other.

We calculate the characteristics of the converter for LEDs

For an accurate calculation, we first determine the power consumption of the LEDs. After the issue is resolved with the connection diagram - will it be parallel or serial. The output voltage and rated power of the required converter will depend on this. This is all the work that needs to be done. Now, in an electrical engineering store or on an online resource, we select a driver according to the calculated indicators.

Good to know! When purchasing a converter, ask the seller for a certificate of conformity for the product. If it is missing, it is better to refrain from buying.

What is a dimmable LED driver

Dimmable is a driver for an LED lamp that supports changing the input current parameters and is able to change the output depending on this. This is achieved by changing the intensity of the glow of LED emitters. An example would be a remote controlled LED strip controller. If desired, it becomes possible to "dim" the lighting in the room, to give rest to the eyes. It is also appropriate if a child is sleeping in the room.

Dimming is performed from the remote control, or from a standard mechanical stepless switch.

Chinese converters - what is special about them

Chinese friends are famous for their ability to fake equipment so that it becomes impossible to use. The same can be said for drivers. When purchasing a Chinese device, be prepared for overstated specifications, low quality and a quick failure of the converter. If you are going to build the first LED-lamp in your life, practice and gain skills in radio electronics, such products are indispensable due to their low cost and ease of execution.

What affects the service life of converters

The reasons for the failure of the converter are:

Sudden power surges in the network.
High humidity if the device does not meet the degree of protection.
Temperature fluctuations.
Insufficient ventilation.
Increased dustiness.
Incorrect calculation of consumer power.

Any of these causes can be prevented or corrected. This means that it is in the power of the home master to extend the life of the stabilizing device.

PT4115 LED driver circuit with dimmer

We are talking about a Chinese manufacturer, which is an exception to the rule. A microcircuit, on the basis of which it is possible to assemble the simplest converter just by its production. The PT4115 microprocessor has good performance and is gaining popularity in Russia.

Related article:

If the lighting is LED and conventional regulators are not suitable, then they are installed, which are slightly different structurally and technically. Today we will figure out what they are, how to choose and even make such a device yourself.

The figure shows the simplest PT4115 driver circuit for LEDs, which a novice home master without experience with radio electronics can assemble. Interesting in the chip is an additional output (DIM) that allows you to connect a dimmer (dimmer).

How to make a DIY LED driver

Any novice master can assemble an LED lamp driver circuit. But this will require accuracy and patience. From the first time, the stabilizing device may not work. To make it clearer to the reader how the work is done, we offer several simple schemes.

As you can see, there is nothing complicated in driver circuits for LEDs from a 220 V network. Let's try to consider step by step all the stages of work.

DIY step-by-step instructions for making a driver for LEDs

Photo example	Action to take
	To work, we need a regular power supply for the phone. It makes everything quick and easy.
	After disassembling the charger in our hands, we already have an almost complete driver for three one-watt LEDs, but it needs to be slightly modified.
	We solder a 5 kOhm limiting resistor, which is located near the output channel. It is he who prevents the charger from applying too much voltage to the cell phone.
	Instead of a limiting resistor, we solder a tuning resistor by setting the same 5 kOhm on it. Subsequently, add voltage to the required.
	3 LEDs of 1 W each are soldered to the output channel, connected in series, which will give us a total of 3 W.
	We find the input contacts and unsolder from the printed circuit board. We no longer need them...
	... and in their place we solder the power cord, through which 220 V will be supplied.
	If desired, you can put a 1 Ohm resistor in the gap, set all indicators with an ammeter. In this case, the attenuation range of the LEDs will be wider.
	After complete assembly, we check the performance. The output voltage is 5 V, the LEDs are not yet lit.
	By turning the knob on the resistor, we see how the LED elements begin to “flare up”.

Be careful. From such a converter, you can get a discharge not only of 220 V (from the power cord), but also a shock of about 450 V, which is rather unpleasant (tested on yourself).

Very important! Before you check the LED driver for performance and connect it to a power source, you should once again visually check the correctness of the assembled circuit. Electric shock is life threatening and flash from a short circuit can cause damage to the eyes.

Current converters for light diodes: where to buy and what is the cost

Such devices are purchased in electrical stores or on the Internet resources. The second option is more cost effective. In addition, many manufacturers offer free shipping. Consider some models with an input voltage of 220 V with specifications and prices as of December 2017.

Model	Protection class, IP	Output voltage, V	Power, W	Cost, rub.
DFT-I-40- LD64	20	60-130	45	400
ZF-AC LD49	40	40-70	54	450
XS0812-12W PS12	20	24-44	12	200
PS100 (open)	20	30-36	100	1100
PF4050A PS50	65	27-36	50	500
PF100W LD100	65	23-36	100	1000

Looking at the prices, we can say that the independent manufacture of a current converter is more suitable for those for whom it is only a hobby. You can buy such a device quite inexpensively.

Summarize

When choosing a current converter for LED lamps, you should carefully calculate everything. Any error can lead to a decrease in the service life of the purchased device. Despite the low cost of the stabilizer, it is rather unpleasant to constantly throw money away. Only in this case the driver will serve its due period. And when making it yourself, follow the rules of electrical safety and be careful and attentive when assembling the circuit.

We hope that the information provided today was useful to our reader. You can ask any questions in the discussion - we will definitely answer them. Write, ask, share your experience with other readers.

And finally, a short video on today's topic:

Reverse engineering

Recently, a friend asked me to help with a problem. He is developing LED lamps, trading them along the way. He has accumulated a number of lamps that are not working properly. Outwardly, this is expressed as follows - when turned on, the lamp flashes for a short time (less than a second), goes out for a second and repeats endlessly. He gave me three such lamps for research, I solved the problem, the malfunction turned out to be very interesting (just like Hercule Poirot) and I want to talk about the troubleshooting path.

The LED lamp looks like this:

Fig 1. Appearance of the disassembled LED lamp

The developer applied an interesting solution - the heat from the working LEDs is taken by a heat pipe and transferred to a classic aluminum radiator. According to the author, this solution provides the correct thermal conditions for the LEDs, minimizing thermal degradation and ensuring the longest possible life of the diodes. Along the way, the service life of the diode power driver increases, since the driver board is removed from the thermal circuit and the temperature of the board does not exceed 50 degrees Celsius.

Such a decision - to separate the functional zones of light emission, heat removal and supply current generation - made it possible to obtain high performance characteristics of the lamp in terms of reliability, durability and maintainability.
The minus of such lamps, oddly enough, directly follows from its pluses - manufacturers do not need a durable lamp :). Everyone remembers the story of the conspiracy of incandescent lamp manufacturers on a maximum service life of 1000 hours?

Well, I can not help but note the characteristic appearance of the product. My "state control" (wife) did not allow me to put these lamps in a chandelier where they are visible.

Let's get back to driver issues.

This is what the driver board looks like:

Fig 2. External view of the LED driver board from the surface mounting side

And from the reverse side:

Fig 3. External view of the LED driver board from the side of power parts

Studying it under a microscope made it possible to determine the type of control microcircuit - this is MT7930. This is a flyback converter control chip (Fly Back), hung with various protections, like a Christmas tree with toys.

The MT7930 has built-in protections:

From excess current of the key element
lowering the supply voltage
increasing the supply voltage
short circuit in the load and load break.
from exceeding the temperature of the crystal

Declaring protection against a short circuit in the load for a current source is more of a marketing nature :)

It was not possible to obtain a circuit diagram for just such a driver, however, a search on the network turned up several very similar circuits. The closest one is shown in the figure:

Fig 4. LED Driver MT7930. Schematic diagram

An analysis of this circuit and a thoughtful reading of the manual for the microcircuit led me to the conclusion that the source of the flashing problem is the operation of the protection after the start. Those. the initial start-up procedure passes (the flashing of the lamp is what it is), but then the converter turns off due to some of the protections, the power capacitors are discharged and the cycle starts anew.

Attention! There are life-threatening voltages in the circuit! Do not repeat without proper understanding of what you are doing!

To study signals with an oscilloscope, it is necessary to decouple the circuit from the network so that there is no galvanic contact. For this I used an isolating transformer. Two TN36 transformers, still of Soviet production, dated 1975, were found in stocks on the balcony. Well, these are timeless devices, massive, completely covered in green varnish. Connected according to the scheme 220 - 24 - 24 -220. Those. first lowered the voltage to 24 volts (4 secondary windings of 6.3 volts each), and then increased it. The presence of several primary windings with taps gave me the opportunity to play with different supply voltages - from 110 volts to 238 volts. Such a solution is, of course, somewhat redundant, but quite suitable for one-time measurements.

Fig 5. Photo of an isolation transformer

From the description of the start in the manual, it follows that when power is applied, the capacitor C8 begins to charge through resistors R1 and R2 with a total resistance of about 600 kΩ. Two resistors are used out of safety requirements, so that in the event of a breakdown of one, the current through this circuit does not exceed a safe value.

So, the power supply capacitor is slowly charging (this time is about 300-400 ms) and when the voltage on it reaches the level of 18.5 volts, the converter start procedure starts. The microcircuit begins to generate a sequence of pulses to the key field-effect transistor, which leads to the appearance of voltage on the Na winding. This voltage is used in two ways - to form feedback pulses to control the output current (circuit R5 R6 C5) and to form the operating power supply voltage of the microcircuit (circuit D2 R9). At the same time, a current appears in the output circuit, which leads to the ignition of the lamp.

Why does protection work and by what parameter?

First guess

Overvoltage protection operation?

To test this assumption, I unsoldered and checked the resistors in the divider circuit (R5 10k and R6 39k). You can’t check them without soldering them, because they are paralleled through the transformer winding. The elements turned out to be serviceable, but at some point the circuit worked!

I checked the waveforms and voltages of the signals at all points of the converter with an oscilloscope and was surprised to see that all of them are completely passport. No deviations from the norm ...

I let the circuit work for an hour - everything is OK.

What if you let it cool down? After 20 minutes in the off state does not work.

Very good, apparently the matter is in the heating of some element?

But what? And what parameters of the element can float away?

At this point, I concluded that there is some kind of temperature-sensitive element on the converter board. Heating this element completely normalizes the operation of the circuit.
What is this element?

Second guess

Suspicion fell on the transformer. The problem was conceived as follows - the transformer, due to manufacturing inaccuracies (say, a winding is unwound for a couple of turns), operates in the saturation region and, due to a sharp drop in inductance and a sharp increase in current, the current protection of the field key is triggered. This is a resistor R4 R8 R19 in the drain circuit, the signal from which is fed to pin 8 (CS, apparently Current Sense) of the microcircuit and is used for the current OS circuit and, if the setting of 2.4 volts is exceeded, turns off the generation to protect the field effect transistor and transformer from damage. On the board under study, there are two resistors R15 R16 in parallel with an equivalent resistance of 2.3 ohms.

But as far as I know, the parameters of the transformer deteriorate when heated, i.e. the behavior of the system should be different - turning it on, working for 5-10 minutes and turning it off. The transformer on the board is very massive and its thermal constant is by no means less than a few minutes.
Maybe, of course, there is a short-circuited coil in it, which disappears when heated?

Soldering the transformer to a guaranteed serviceable one was impossible at that moment (the guaranteed working board had not yet been brought), so I left this option for later, when there are no versions at all :). Plus, the intuitive feeling is not it. I trust my engineering intuition.

At this point, I tested the hypothesis that the current protection was triggered by reducing the OS current resistor by half by soldering the same parallel to it - this did not affect the blinking of the lamp.

This means that everything is fine with the current of the field-effect transistor and there is no current overshoot. This was clearly seen in the waveform on the oscilloscope screen. The peak of the sawtooth signal was 1.8 volts and clearly did not reach the value of 2.4 volts, at which the microcircuit turns off the generation.

The circuit also turned out to be insensitive to a change in load - neither connecting a second head in parallel, nor switching a warm head to a cold one and back did not change anything.

Third assumption

I investigated the supply voltage of the microcircuit. During normal operation, all voltages were absolutely normal. In flashing mode, too, as far as one could judge from the waveforms on the oscilloscope screen.

As before, the system blinked in a cold state and began to work normally when the transformer legs were heated with a soldering iron. Warm up for 15 seconds - and everything starts up normally.

Heating the chip with a soldering iron did nothing.

And the short heating time was very embarrassing ... what can change there in 15 seconds?

At some point, he sat down and methodically, logically cut off everything that was guaranteed to work. If the lamp lights up, then the starting circuits are working.
Once the board is heated, it is possible to start the system and it works for hours, which means that the power systems are working.
Cools down and stops working - something depends on the temperature ...
Crack on the board in the feedback circuit? Cools down and contracts, the contact is broken, heats up, expands and the contact is restored?
I climbed a cold board with a tester - there are no breaks.

What else can interfere with the transition from the start-up mode to the operating mode?!!!

Out of complete hopelessness, I intuitively soldered a 10 microfarad 35 volt electrolytic capacitor in parallel to power the microcircuit.

And then happiness came. Earned!

Replacing the 10 microfarad capacitor with a 22 microfarad one completely solved the problem.

Here it is, the culprit of the problem:

Figure 6. Capacitor with wrong capacitance

Now the mechanism of failure has become clear. The circuit has two microcircuit power circuits. The first, starting one, slowly charges the capacitor C8 when 220 volts are applied through a 600 kΩ resistor. After it is charged, the microcircuit begins to generate pulses for the field worker, starting the power part of the circuit. This leads to the generation of power for the microcircuit in operating mode on a separate winding, which is supplied to the capacitor through a diode with a resistor. The signal from this winding is also used to stabilize the output current.

While the system has not entered the operating mode, the microcircuit is powered by the stored energy in the capacitor. And it was missing a little - literally a couple of percent.
The voltage drop turned out to be enough for the microcircuit protection system to work on reduced power and turn off everything. And the cycle began anew.

It was not possible to catch this supply voltage drop with an oscilloscope - too rough estimate. It seemed to me that everything was fine.

Warming up the board increased the capacitance of the capacitor by the missing percentage - and there was already enough energy for a normal start.

It is clear why only some of the drivers failed with fully functional elements. A bizarre combination of the following factors came into play:

Small capacitance power supply. The tolerance on the capacitance of electrolytic capacitors (-20% + 80%) played a positive role, i.e. capacities with a nominal value of 10 microfarads in 80% of cases have a real capacity of about 18 microfarads. Over time, the capacity decreases due to the drying of the electrolyte.
Positive temperature dependence of the capacitance of electrolytic capacitors on temperature. An increased temperature at the place of output control - literally a couple of degrees is enough and the capacity is enough for a normal start. If we assume that at the place of exit control it was not 20 degrees, but 25-27, then this turned out to be enough for almost 100% passing of the exit control.

The manufacturer of drivers saved, of course, by using capacitances of a lower rating compared to the reference design from the manual (22 microfarads are indicated there), but fresh capacitances at elevated temperatures and taking into account the spread of + 80% allowed a batch of drivers to be handed over to the customer. The customer received seemingly working drivers, which eventually began to fail for some unknown reason. It would be interesting to know - did the manufacturer's engineers take into account the behavior of electrolytic capacitors with increasing temperature and the natural spread, or did it happen by accident?

The widespread use of LEDs led to the mass production of power supplies for them. Such blocks are called drivers. Their main feature is that they are able to stably maintain a given current at the output. In other words, a driver for LEDs is a current source for powering them.

Purpose

Since the LED is a semiconductor element, the key characteristic that determines the brightness of their glow is not voltage, but current. In order for them to be guaranteed to work for the declared number of hours, a driver is needed - it stabilizes the current flowing through the LED circuit. It is possible to use low-power light-emitting diodes without a driver, in which case a resistor plays its role.

Application

Drivers are used both when powering an LED from a 220V network, and from sources of constant voltage 9-36 V. The former are used when lighting rooms with LED lamps and ribbons, the latter are more common in cars, bicycle headlights, portable lamps, etc.

Principle of operation

As already mentioned, the driver is a current source. Its differences from a voltage source are illustrated below.

The voltage source creates a certain voltage at its output, ideally independent of the load.

For example, if you connect a 40 ohm resistor to a 12 V source, a current of 300 mA will flow through it.

If you connect two resistors in parallel, the total current will be already 600 mA at the same voltage.

The driver maintains a given current at its output. The voltage may change.

We also connect a 40 ohm resistor to the 300 mA driver.

The driver will create a 12V drop across the resistor.

If you connect two resistors in parallel, the current will still be 300 mA, and the voltage will drop to 6 V:

Thus, the ideal driver is able to provide the load with the rated current regardless of the voltage drop. That is, an LED with a voltage drop of 2 V and a current of 300 mA will burn as brightly as an LED with a voltage of 3 V and a current of 300 mA.

Main characteristics

When selecting, you need to take into account three main parameters: output voltage, current and power consumed by the load.

The output voltage of the driver depends on several factors:

voltage drop across the LED;
number of LEDs;
connection method.

The current at the output of the driver is determined by the characteristics of the LEDs and depends on the following parameters:

LED power;
brightness.

The power of LEDs affects the current they draw, which can vary depending on the required brightness. The driver must provide them with this current.

The load power depends on:

power of each LED;
their quantity;
colors.

In general, the power consumption can be calculated as

where Pled is the power of the LED,

N is the number of connected LEDs.

The maximum power of the driver should not be less.

It is worth considering that for stable operation of the driver and to prevent its failure, a power margin of at least 20-30% should be provided. That is, the following relation must hold:

where Pmax is the maximum power of the driver.

In addition to the power and number of LEDs, the load power also depends on their color. LEDs of different colors have different voltage drops at the same current. For example, the XP-E red LED has a voltage drop of 1.9-2.4V at 350mA. The average power consumed by it in this way is about 750 mW.

The green XP-E has a 3.3-3.9V drop at the same current and will average about 1.25W. That is, a driver designed for 10 watts can power either 12-13 red LEDs or 7-8 green ones.

How to choose a driver for LEDs. Ways to connect LED

Let's say there are 6 LEDs with a voltage drop of 2V and a current of 300mA. You can connect them in various ways, and in each case you will need a driver with certain parameters:

It is unacceptable to connect 3 or more LEDs in parallel in this way, since in this case too much current can flow through them, as a result of which they will quickly fail.

Please note that in all cases the driver power is 3.6 W and does not depend on the way the load is connected.

Thus, it is more expedient to choose a driver for LEDs already at the stage of purchasing the latter, having previously determined the connection scheme. If you first purchase the LEDs themselves, and then select a driver for them, this can be a difficult task, since the likelihood that you will find exactly the power source that can provide the operation of this particular number of LEDs, included in a particular scheme, is small.

Kinds

In general, LED drivers can be divided into two categories: linear and switching.

The linear output is a current generator. It provides stabilization of the output current with an unstable input voltage; moreover, the adjustment occurs smoothly, without creating high-frequency electromagnetic interference. They are simple and cheap, but their low efficiency (less than 80%) limits their scope to low-power LEDs and strips.

Pulse are devices that create a series of high-frequency current pulses at the output.

Typically, they operate on the principle of pulse-width modulation (PWM), that is, the average value of the output current is determined by the ratio of the width of the pulses to their period (this value is called the duty cycle).

The diagram above shows how a PWM driver works: the pulse frequency remains constant, but the duty cycle varies from 10% to 80%. This leads to a change in the average value of the current I cp at the output.

Such drivers are widely used due to their compactness and high efficiency (about 95%). The main disadvantage is the higher level of electromagnetic interference compared to linear ones.

220V LED driver

For inclusion in the 220 V network, both linear and pulsed ones are produced. There are drivers with galvanic isolation from the network and without it. The main advantages of the former are high efficiency, reliability and safety.

Without galvanic isolation, they are usually cheaper, but less reliable and require care when connecting, since there is a possibility of electric shock.

Chinese drivers

The demand for LED drivers contributes to their mass production in China. These devices are pulsed current sources, usually 350-700 mA, often without a case.

Chinese driver for 3w led

Their main advantages are low price and the presence of galvanic isolation. The disadvantages are the following:

low reliability due to the use of cheap circuit solutions;
lack of protection against overheating and fluctuations in the network;
high level of radio interference;
high output ripple;
fragility.

Life time

Typically, the life of the driver is less than that of the optical part - manufacturers give a guarantee of 30,000 hours of operation. This is due to factors such as:

instability of mains voltage;
temperature fluctuations;
humidity level;
driver load.

The weakest link in the LED driver is the smoothing capacitors, which tend to evaporate the electrolyte, especially in conditions of high humidity and unstable supply voltage. As a result, the level of ripple at the output of the driver increases, which negatively affects the operation of the LEDs.

Also, the incomplete loading of the driver affects the service life. That is, if it is designed for 150 W, and operates at a load of 70 W, half of its power returns to the network, causing it to overload. This causes frequent power failures. We recommend reading about.

Driver circuits (microcircuits) for LEDs

Many manufacturers produce specialized driver ICs. Let's consider some of them.

ON Semiconductor UC3845 is a switching driver with output current up to 1A. The driver circuit for the 10w LED on this chip is shown below.

Supertex HV9910 is a very common switching driver IC. The output current does not exceed 10 mA, has no galvanic isolation.

A simple current driver on this chip is shown below.

Texas Instruments UCC28810. Network impulse driver, has the ability to organize galvanic isolation. Output current up to 750 mA.

Another chip from this company, a driver for powering high-power LEDs LM3404HV, is described in this video:

The device works on the principle of a Buck Converter resonant converter, that is, the function of maintaining the required current is partially assigned to the resonant circuit in the form of a coil L1 and a Schottky diode D1 (a typical diagram is shown below). It is also possible to set the switching frequency by selecting the resistor R ON .

The Maxim MAX16800 is a linear chip that operates at low voltages, so you can build a 12 volt driver on it. The output current is up to 350 mA, so it can be used as a power driver for a powerful LED, flashlight, etc. There is a possibility of dimming. A typical scheme and structure are presented below.

Conclusion

LEDs are much more power hungry than other light sources. For example, exceeding the current by 20% for a fluorescent lamp will not lead to a serious deterioration in performance, while for LEDs, the service life will be reduced several times. Therefore, you should be especially careful when choosing a driver for LEDs.

The guarantee of the brightness of the glow, the efficiency and durability of LED sources is the correct power supply, which can be provided by special electronic devices - drivers for LEDs. They convert the AC voltage in the 220V network into the DC voltage of the set value. To understand what function the converters perform and what to look for when choosing them, an analysis of the main types and characteristics of devices will help.

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

When lighting residential and office premises with LED lamps and fixtures, drivers are used, which are powered by 220V AC. In automotive lighting (headlights, DRL, etc.), bicycle headlights, portable lamps, DC power supplies are used in the range from 9 to 36V. Some low-power LEDs can be connected without a driver, but then a resistor must be added to the 220-volt network for connecting the LED.

The driver output voltage is indicated in the range of two final values, between which stable operation is ensured. There are adapters with an interval from 3V to several tens. To power a circuit of 3 series-connected white LEDs, each of which has a power of 1 W, you need a driver with output values \u200b\u200bof U - 9-12V, I - 350 mA. The voltage drop for each die will be about 3.3V, for a total of 9.9V, which is within the range of the driver.

Main characteristics of converters

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

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

P = P(led) × n,

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

In addition, a mandatory condition must be met, under which a power reserve of 25-30% would be provided. Thus, the value of the maximum power must not be less than the value (1.3 x P).

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

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

What are the drivers for LEDs by device type

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

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

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

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

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

Dimmable LED Drivers

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

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

The driver is controlled using or PWM

Dimmable converters of the second type control the power supply directly. The principle of their operation is both in PWM regulation and in controlling the amount of current flowing through the LEDs. Dimmable drivers of this type are used for constant current LED fixtures. It is worth noting that when controlling LEDs using PWM control, negative effects on vision are observed.

Comparing these two control methods, it is worth noting that when adjusting the current through LED sources, not only a change in the brightness of the glow is observed, but also a change in the color of the glow. So, white LEDs emit a yellowish light at a lower current, and glow blue at an increase. When driving LEDs with PWM control, there are negative effects on vision and a high level of electromagnetic interference. In this regard, PWM control is used quite rarely, in contrast to current regulation.

LED driver circuits

Many manufacturers produce driver ICs for LEDs that allow you to power sources from low voltage. All existing drivers are divided into simple ones based on 1-3 transistors and more complex ones using special microcircuits with pulse-width modulation.

ON Semiconductor offers a wide range of ICs as the basis for drivers. They feature reasonable cost, excellent conversion efficiency, economy and low EMI. The manufacturer presents a UC3845 pulse type driver with an output current of up to 1A. On such a chip, you can implement a driver circuit for a 10W LED.

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

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

Helpful advice! If you are planning to buy superbright 10W LEDs, you can use a switching driver on the UCC28810 chip for designs of them.

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

How to choose a driver for LEDs

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

So there is a possibility of acquiring a driver whose declared power is 50 W. However, in reality it turns out that this characteristic is of a non-permanent nature and such power is only short-term. In reality, such a device will work as a 30W LED driver or a maximum of 40W. It may also turn out that the filling will lack some of the components responsible for the stable operation of the driver. In addition, components of low quality and with a short service life can be used, which is essentially a marriage.

When buying, pay attention to the indication of the brand of the product. On a quality product, the manufacturer will be indicated, which will provide a guarantee and will be ready to be responsible for their products. It should be noted that the service life of drivers from trusted manufacturers will be much longer. The following is the estimated runtime of the drivers, depending on the manufacturer:

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

Helpful advice! What quality the LED driver will be - you choose. However, it should be noted that it is especially important to purchase a branded converter when it comes to using it for LED spotlights and high-power luminaires.

Calculation of drivers for LEDs

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

Related article:

Types. Connection diagrams for LED sources. Calculation of resistance for LEDs. Checking the LED with a multimeter. Do-it-yourself LED designs.

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

This is the algorithm for the functioning of LED drivers. They deliver as much current as they are designed for. The method of connecting LED-devices in this case does not play a role. There are driver models that involve any number of LEDs connected to them. But then there is a limitation on the power of LED sources: it should not exceed the power of the driver itself. Drivers are available designed for a certain number of connected LEDs. They are allowed to connect a smaller number of LEDs. But such drivers have low efficiency, unlike devices designed for a specific number of LED devices.

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

Where to buy LED drivers

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

Implementing companies present a huge range of drivers for LEDs, the technical characteristics and prices of which can be seen in the price lists. As a rule, product prices are indicative and are specified when ordering from the project manager. The range includes converters of various power and degree of protection, used for outdoor and indoor lighting, as well as for lighting and car tuning.

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

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

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

Making drivers for LEDs with your own hands

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

The driver circuit for the 3W LED can be implemented based on the Chinese PowTech PT4115 chip. The microcircuit can be used to power LED devices above 1W and includes control units that have a sufficiently powerful transistor at the output. The PT4115 based driver is highly efficient and has a minimum of piping components.

Overview of PT4115 and technical parameters of its components:

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

The microcircuit has the following conclusions:

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

Do-it-yourself LED driver circuit based on PT4115

Driver circuits for powering LED devices with a dissipating power of 3 W can be made in two versions. The first assumes the presence of a power supply with a voltage of 6 to 30V. In another circuit, power is provided from an alternating current source with a voltage of 12 to 18V. In this case, a diode bridge is introduced into the circuit, at the output of which a capacitor is installed. It helps smooth out voltage fluctuations, its capacitance is 1000 microfarads.

For the first and second circuits, the capacitor (CIN) is of particular importance: this component is designed to reduce ripple and compensate for the energy stored in the inductor when the MOP transistor is turned off. In the absence of a capacitor, all the energy of the inductance through the semiconductor diode DSHB (D) will go to the supply voltage output (VIN) and cause a breakdown of the microcircuit relative to the power supply.

Helpful advice! It must be taken into account that the connection of the driver for LEDs in the absence of an input capacitor is not allowed.

Given the number and how much the LEDs consume, the inductance (L) is calculated. In the LED driver circuit, an inductance should be selected, the value of which is 68-220 μH. This is evidenced by the technical documentation. A slight increase in the value of L can be allowed, but it should be taken into account that then the efficiency of the circuit as a whole will decrease.

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

Assembling Driver Components

The piping components of the RT 4115 chip are selected according to the manufacturer's instructions. For CIN, a low impedance capacitor (low ESR capacitor) should be used, as the use of other analogues will adversely affect the efficiency of the driver. If the device is powered from a stabilized current unit, one capacitor with a capacity of 4.7 uF or more will be needed at the input. It is recommended to place it next to the chip. If the current is alternating, you will need to introduce a solid-state tantalum capacitor with a capacitance of at least 100 microfarads.

In the switching circuit for 3 W LEDs, it is necessary to install an inductor of 68 μH. It should be located as close as possible to the SW terminal. You can make your own coil. This will require a ring from a failed computer and a winding wire (PEL-0.35). Diode FR 103 can be used as diode D. Its parameters are: capacitance 15 pF, recovery time 150 ns, temperature from -65 to 150°C. It can handle surge currents up to 30A.

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

RS = 0.1 / I,

where I is the rated current of the LED source.

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

DIY driver layout for 10 watt LED

You can assemble a driver for a powerful LED yourself, using electronic boards from failed fluorescent lamps. Most often in such lamps the lamps burn out. The electronic board remains working, which allows you to use its components for homemade power supplies, drivers and other devices. To work, you may need transistors, capacitors, diodes, inductors (chokes).

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

Next, over the primary turns of the winding, it is necessary to make 20 turns of wire and use a soldering iron to connect this winding to the rectifier diode bridge. After that, you should apply voltage from the 220V network and measure the output voltage at the rectifier. Its value was 9.7V. The LED source consumes 0.83 A through the ammeter. The rating of this LED is 900 mA, however, in order to underestimate the current consumption, it will increase its resource. The assembly of the diode bridge is carried out by surface mounting.

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

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