Simple drivers for high-power LEDs circuit. Drivers for LEDs: types, purpose, connection. Finding faulty LEDs

An integral part of any high-quality LED lamp or luminaire is the driver. In relation to lighting, the term “driver” should be understood as an electronic circuit that converts the input voltage into a stabilized current given value. The functionality of the driver is determined by the width of the input voltage range, the ability to adjust output parameters, susceptibility to changes in the supply network and efficiency.

The quality indicators of the lamp or lamp as a whole, service life and cost depend on the listed functions. All power supplies (PS) for LEDs are conventionally divided into linear and pulsed type converters. Linear power supplies may have a current or voltage stabilization unit. Radio amateurs often construct circuits of this type with their own hands using the LM317 microcircuit. Such a device is easy to assemble and has low cost. But, due to the very low efficiency and obvious limitations on the power of connected LEDs, the prospects for the development of linear converters are limited.

Switching drivers can have an efficiency of more than 90% and a high degree of protection against network interference. Their power consumption is tens of times less than the power supplied to the load. Thanks to this, they can be manufactured in a sealed case and are not afraid of overheating.

The first pulse stabilizers had a complex device without idle protection. Then they were modernized and, due to the rapid development of LED technologies, specialized chips with frequency and pulse width modulation appeared.

LED power supply circuit based on a capacitor divider

Unfortunately, in the design of cheap LED lamps for 220V from China neither linear nor pulse stabilizer. Motivated by the exceptionally low price of the finished product, the Chinese industry was able to simplify the power supply circuit as much as possible. It is not correct to call it a driver, since there is no stabilization here. From the figure it is clear that electrical diagram The lamp is designed to operate from a 220V network. The alternating voltage is reduced by the RC circuit and supplied to the diode bridge. Then the rectified voltage is partially smoothed by a capacitor and is supplied to the LEDs through a current-limiting resistor. This circuit does not have galvanic isolation, that is, all elements are constantly at high potential.

As a result, frequent drawdowns mains voltage causes the LED lamp to flicker. Conversely, an excessive network voltage causes an irreversible aging process of the capacitor with loss of capacity, and, sometimes, causes its rupture. It is worth noting that another, serious negative side of this scheme is accelerated process degradation of LEDs due to unstable supply current.

Driver circuit for CPC9909

Modern pulse drivers for LED lamps have a simple circuit, so you can easily make it even with your own hands. Today, to build drivers, a number of integrated circuits are produced, specifically designed to control high-power LEDs. To make things easier for amateurs electronic circuits, developers of integrated drivers for LEDs provide typical connection diagrams and calculations of wiring components in their documentation.

General information

The American company Ixys has launched the production of the CPC9909 chip, designed to control LED assemblies and high-brightness LEDs. The driver based on CPC9909 is small in size and does not require large investments. The CPC9909 IC is manufactured in a planar design with 8 pins (SOIC-8) and has a built-in voltage regulator.

Thanks to the presence of a stabilizer, the operating range of the input voltage is 12-550V from a DC source. The minimum voltage drop across LEDs is 10% of the supply voltage. Therefore, the CPC9909 is ideal for connecting high voltage LEDs. The IC works great in temperature range from -55 to +85°C, which means it is suitable for designing LED lamps and luminaires for outdoor lighting.

Pin assignment

It is worth noting that with the help of CPC9909 you can not only turn on and off a powerful LED, but also control its glow. To learn about all the capabilities of the IC, consider the purpose of its conclusions.

1. VIN Designed to supply power voltage.
2. CS. Designed to connect an external current sensor (resistor), with which the maximum LED current is set.
3. GND. General driver output.
4. GATE. Output of the microcircuit. Supplies a modulated signal to the gate of the power transistor.
5. P.W.M.D. Low frequency dimming input.
6. VDD. Output for supply voltage regulation. In most cases, it is connected via a capacitor to a common wire.
7. L.D. Designed to set analog dimming.
8. RT. Designed to connect a time setting resistor.

Scheme and its principle of operation

A typical connection of the CPC9909 powered from a 220V network is shown in the figure. The circuit is capable of driving one or more high-power or High Brightness LEDs. The circuit can be easily assembled with your own hands, even at home. The finished driver does not require adjustment, taking into account the correct selection of external elements and compliance with the rules for their installation.
The driver for a 220V LED lamp based on CPC9909 works using the pulse frequency modulation method. This means that the pause time is a constant value (time-off=const). The alternating voltage is rectified by a diode bridge and smoothed by a capacitive filter C1, C2. Then it goes to the VIN input of the microcircuit and starts the process of generating current pulses at the GATE output. The IC's output current drives power transistor Q1. At the moment the transistor is open (pulse time “time-on”), the load current flows through the circuit: “+ diode bridge” – LED – L – Q1 – R S – “-diode bridge”.
During this time, the inductor accumulates energy in order to transfer it to the load during a pause. When the transistor closes, the inductor energy provides load current in the circuit: L – D1 – LED – L.
The process is cyclical, resulting in a sawtooth current through the LED. The greatest and smallest value saw depends on the inductance of the inductor and the operating frequency.
The pulse frequency is determined by the value of the resistance RT. The amplitude of the pulses depends on the resistance of the resistor RS. The LED current is stabilized by comparing the internal reference voltage of the IC with the voltage drop across R S . A fuse and a thermistor protect the circuit from possible emergency conditions.

Calculation of external elements

Frequency setting resistor

The duration of the pause is set by an external resistor R T and determined using a simplified formula:

t pause =R T /66000+0.8 (µs).

In turn, the pause time is related to the duty cycle and frequency:

t pause =(1-D)/f (s), where D is the duty cycle, which is the ratio of the pulse time to the period.

Current sensor

The resistance rating R S specifies the amplitude value of the current through the LED and is calculated by the formula: R S =U CS /(I LED +0.5*I L pulse), where U CS is the calibrated reference voltage equal to 0.25V;

I LED – current through the LED;

I L pulse – the value of load current ripple, which should not exceed 30%, that is, 0.3*I LED.

After the transformation, the formula will take the form: R S =0.25/1.15*I LED (Ohm).

The power dissipated by the current sensor is determined by the formula: P S =R S *I LED *D (W).

A resistor with a power reserve of 1.5-2 times is accepted for installation.

Throttle

As is known, the inductor current cannot change abruptly, increasing during the pulse and decreasing during the pause. The radio amateur's task is to select a coil with an inductance that provides a compromise between the quality of the output signal and its dimensions. To do this, remember the ripple level, which should not exceed 30%. Then you will need an inductance with a nominal value:

L=(US LED *t pause)/ I L pulse, where U LED is the voltage drop across the LED(s), taken from the I-V characteristic curve.

Power filter

Two capacitors are installed in the power circuit: C1 – to smooth out the rectified voltage and C2 – to compensate for frequency interference. Since the CPC9909 operates over a wide input voltage range, there is no need for a large electrolytic C1 capacitance. 22 uF will be enough, but more is possible. The capacitance of metal film C2 for a circuit of this type is standard - 0.1 μF. Both capacitors must withstand a voltage of at least 400V.

However, the chip manufacturer insists on installing capacitors C1 and C2 with low equivalent series resistance (ESR) to avoid the negative impact of high-frequency noise that occurs when the driver switches.

Rectifier

The diode bridge is selected based on the maximum direct current and reverse voltage. For operation in a 220V network it reverse voltage must be at least 600V. The calculated value of the forward current directly depends on the load current and is defined as: I AC =(π*I LED)/2√2, A.

The resulting value must be multiplied by two to increase the reliability of the circuit.

Selecting remaining circuit elements

Capacitor C3 installed in the power supply circuit of the microcircuit should have a capacity of 0.1 µF with a low ESR value, similar to C1 and C2. The unused pins PWMD and LD are also connected to the common wire via C3.

Transistor Q1 and diode D1 operate in pulse mode. Therefore, the choice should be made taking into account their frequency properties. Only elements with a short recovery time will be able to contain Negative influence transient processes at the moment of switching at a frequency of about 100 kHz. The maximum current through Q1 and D1 is equal to the amplitude value of the LED current, taking into account the selected duty cycle: I Q1 = I D1 = D*I LED, A.

The voltage applied to Q1 and D1 is pulsed in nature, but no more than the rectified voltage taking into account the capacitive filter, that is, 280V. The choice of power elements Q1 and D1 should be made with a margin, multiplying the calculated data by two.

The fuse protects the circuit from an emergency short circuit and must withstand the maximum load current for a long time, including impulse noise.

I FUSE =5*I AC , A.

Installing an RTH thermistor is necessary to limit the driver inrush current when the filter capacitor is discharged. With its resistance, RTH must protect the diodes of the bridge rectifier from breakdown in the initial seconds of operation.

R TH =(√2*220)/5*I AC, Ohm.

Other options for enabling the CPC9909

Soft start and analogue dimming

If desired, the CPC9909 can provide a soft turn on of the LED as its brightness gradually increases. Soft start is realized using two fixed resistors connected to the LD pin, as shown in the figure. This decision allows you to extend the life of the LED.

Also, the LD pin allows you to implement the analog dimming function. To do this, the 2.2 kOhm resistor is replaced with a variable resistor 5.1 kOhm, thereby smoothly changing the potential at the LD pin.

Pulse dimming

You can control the glow of the LED by applying rectangular pulses to the PWMD (pulse width modulation dimming) pin. To do this, a microcontroller or a pulse generator is used with mandatory separation through an optocoupler.

In addition to the considered driver option for LED lamps, there are similar circuit solutions from other manufacturers: HV9910, HV9961, PT4115, NE555, RCD-24, etc. Each of them has its own strengths and weak spots, but in general, they successfully cope with the imposed load when assembling them with their own hands.

Read also

The simplest driver for powering LEDs, which anyone can make with their own hands, a driver diagram with a description of its manufacture.

LEDs, unlike others emitting light devices (lamps, fixtures) cannot be directly connected to the household network. Moreover, LEDs cannot be powered by a fixed voltage, which is indicated in the data sheet. The LED power supply must have elements that limit the current through the LED in accordance with its characteristics, or a ballast. This is why a diode is called a “current device”, and the use of traditional voltage converters is not applicable; a driver should be used to power the LEDs.

Quite often for connecting LEDs in a car, the same “ angel eyes"on COB rings, a driver is required, you can make it yourself and it will cost you mere pennies.

We have a 12 V car network, we calculate what kind of resistor we need using the example of a COB ring with a power of 5 W.

We can find out the current consumed by an electrical appliance by knowing its power and supply voltage.
The current consumption is equal to the power divided by the network voltage.
The COB ring consumes 5 watts.

The voltage in the car is 12 Volts.
We get 420 milliamps of current consumed by such a ring.
Further on any online calculator, like this one - ledcalc.ru/lm317

let's calculate:

• Design resistance.
• Nearest standard.
• Current with a standard resistor.
• Resistor power.

We enter the required current of 420 milliamps and get:

• Estimated resistance: 2.98 ohms
  Nearest standard: 3.30 ohms
  Current with standard resistor: 379 mA
  Resistor power: 0.582 W.

THIS CALCULATION WORKS WHEN YOU ARE EXACTLY SURE OF THE CHARACTERISTICS OF THE LED, IF NOT, THEN WE MEASURE THE CURRENT CONSUMPTION WITH A MULTIMETER!

By the way, the above calculation, where I took the diode specification from the Chinese, is incorrect, because when measuring, the actual current consumption turned out to be not 420 mA, but 300 mA. Therefore, we can immediately conclude that there is no smell of five watts :)

Its pinout.

The resistor, which was calculated above, and we connect the whole thing in current stabilizer mode.

As a result, we got a stabilized current at the output.

But this is for an ideal case. As for the case with a real car, where jumps up to 14 Volts happen with pennies, then calculate the resistor for the worst case with a margin.

The widespread use of LEDs has 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 light emitting diodes (LEDs) is a source of current to power them.

Purpose

Since LEDs are semiconductor elements, key characteristic, which determines the brightness of their glow is not voltage, but current. In order for them to be guaranteed to work for the stated 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 this case, its role is played by a resistor.

Application

Drivers are used both when powering the LED from a 220V network and from sources DC voltage 9-36 V. The former are used when lighting rooms with LED lamps and strips, the latter are more often found in cars, bicycle lights, portable lanterns, 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 produces 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 600 mA at the same voltage.

The driver maintains the specified current at its output. The voltage may change in this case.

Let's also connect a 40 Ohm resistor to the 300 mA driver.

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

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

Thus, an ideal driver is capable of delivering the rated current to the load regardless of 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 driver output voltage depends on several factors:

• LED voltage drop;
• number of LEDs;
• connection method.

The driver output current 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 consume, which can vary depending on the required brightness. The driver must provide them with this current.

Load power depends on:

• power of each LED;
• their quantities;
• colors.

IN general case power consumption can be calculated as

where Pled is the LED power,

N is the number of connected LEDs.

The maximum driver power should not be less.

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

where Pmax is the maximum driver power.

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 for the same current. For example, the red XP-E LED has a voltage drop of 1.9-2.4 V at 350 mA. Its average power consumption is thus about 750 mW.

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

How to choose a driver for LEDs. LED connection methods

Let's say there are 6 LEDs with a voltage drop of 2 V and a current of 300 mA. You can connect them different 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 too much current may 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 method of connecting the load.

Thus, it is more advisable to select a driver for LEDs already at the stage of purchasing the latter, having previously determined the connection diagram. If you first purchase the LEDs themselves, and then select a driver for them, this may not be an easy task, since the likelihood that you will find exactly the power source that can ensure the operation of exactly this number of LEDs connected according to a specific circuit 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 of application to low-power LEDs and strips.

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

They usually 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 pulse width to their repetition period (this value is called the duty cycle).

The diagram above shows the operating principle of a PWM driver: 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 output current I cp.

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

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

Chinese drivers

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

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 level of output ripple;
• fragility.

Life time

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

• instability of mains voltage;
• temperature changes;
• humidity level;
• driver load.

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

Also, the service life is affected by incomplete driver load. That is, if it is designed for 150 W, but 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 (chips) for LEDs

Many manufacturers produce specialized driver chips. Let's look at some of them.

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

Supertex HV9910 is a very common pulse driver chip. The output current does not exceed 10 mA and has no galvanic isolation.

A simple current driver on this chip is shown below.

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

Another microcircuit from this company is a power driver powerful LEDs LM3404HV - described in this video:

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

Maxim MAX16800 is a linear microcircuit 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. Typical scheme and structure are presented below.

Conclusion

LEDs are much more demanding on the power supply than other light sources. For example, current exceeding 20% ​​for fluorescent lamp will not entail a serious deterioration in performance, but for LEDs the service life will be reduced several times. Therefore, you should choose a driver for LEDs especially carefully.

Today, probably, not a single apartment or a private house can't do without LED lighting. And street lighting is gradually changing to economical and durable LED elements. But looking at today’s topic of conversation, the question arises – what does the driver have to do with it (that’s how “driver” is translated from English)? This is the first question that comes to the mind of a person ignorant of LED lighting. 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 driver for LEDs 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 are they?

The answer to the question of what is an LED driver is quite simple. This is a device that stabilizes the voltage and gives it the characteristics necessary 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 is compact in size and fits into the body of the light device. In essence, it can be called stabilizing starting device or frequency converter.

Where are stabilizing devices used for LED elements?

LED drivers for LEDs are used in various fields:

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

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

Operating principle of a 220V LED lamp driver circuit

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

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

Driver Features Worth Considering

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

1. Driver rated power– this parameter must exceed the total power consumed by the light diodes that will be in its circuit.
2. Output voltage– depends on the magnitude of the voltage drop across each of the light diodes.
3. 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 you can connect 16 red LEDs to a 12 V power supply, then the maximum number of green ones will be 9.

Division 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 in both cost and technical characteristics.

Linear converters are characterized by their 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 helps reduce the coefficient useful action(efficiency).

Pulse converters are based on the principle of pulse width modulation (PWM) and during their operation, the values ​​of output currents are 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 have one drawback. During their operation, it is possible to induce electromagnetic interference. Let's try to figure out what this threatens a person with simple example.

A person living in an apartment or house has a pacemaker. At the same time, in a small room there is a chandelier with many devices operating on pulsed ice drivers for. 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 located at a distance of less than a meter 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 you plan to place it hidden, it is better to choose a converter without a housing - the cost will be lower with the same technical characteristics.

Important! Drivers made in China usually do not meet the stated specifications. You shouldn’t skimp on purchasing a “made in” converter. It is better to give preference to a 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 serial connection you will need a 12 V and 300 mA driver. In this case, the glow will be even across all elements.

By connecting the emitters in parallel in a group of 3, we will be able to use a 6 V converter, but 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. Afterwards, the issue with the connection diagram is decided - will it be parallel or serial. The output voltage and rated power of the required converter will depend on this. That's all the work that needs to be done. Now, in an electrical 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 purchasing.

What is a dimmable LED driver?

Dimmable is a driver for an LED lamp that supports changing input current parameters and is capable of changing output current parameters depending on this. This is achieved by changing the glow intensity of LED emitters. An example would be a controller for an LED strip with remote control. If desired, it becomes possible to “dim” the lighting in the room and give your eyes a rest. This 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's special about them

Chinese friends are famous for their ability to counterfeit equipment so that it becomes impossible to use. The same can be said for drivers. When purchasing a Chinese device, be prepared for inflated declared characteristics, low quality and rapid failure of the converter. If you are going to build your first LED lamp, 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 causes of converter failure are:

1. Sudden power surges in the network.
2. Increased humidity if the device does not comply with the degree of protection.
3. Temperature changes.
4. Insufficient ventilation.
5. Increased dustiness.
6. Incorrect calculation of consumer power.

Any of these reasons can be prevented or corrected. This means that it is within the power of a home craftsman to extend the service life of the stabilizing device.

PT4115 LED driver circuit with dimmer

We will talk about a Chinese manufacturer, which is an exception to the rule. A microcircuit on the basis of which you can assemble a simple converter made by him. The PT4115 microprocessor has good characteristics and is gaining popularity in Russia.

Related article:

If LED lighting and conventional regulators are not suitable, then they are installed, which are slightly different structurally and technically. Today we’ll 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 can be assembled by a novice home craftsman without experience in working with radio electronics. An interesting feature of the microcircuit is an additional output (DIM) that allows the connection of a dimmer.

How to make a driver for LEDs with your own hands

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

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

Step-by-step instructions for making a DIY LED driver

Photo example	Action to be performed
	To work, we need a regular power supply for the phone. With its help, everything is done quickly and easily.
	After disassembling the charger in our hands, we already have an almost complete driver for three one-watt LEDs, but it needs a little modification.
	We solder a 5 kOhm limiting resistor, which is located near the output channel. It is he who does not give charger Apply too much voltage to the cell phone.
	Instead of a limiting resistor, we solder in a tuning resistor, setting it to the same 5 kOhm. Subsequently, we will add voltage to the required level.
	3 LEDs of 1 W each are soldered onto the output channel, connected in series, which gives us a total of 3 W.
	We find the input contacts and unsolder them from printed circuit board. We don't need them anymore...
	...and in their place we solder a power cord through which 220 V power will be supplied.
	If desired, you can put a 1 Ohm resistor in the gap and set all the indicators with an ammeter. In this case, the attenuation range of the LEDs will be wider.
	After complete assembly, we check the functionality. The output voltage is 5 V, the LEDs are not lit yet.
	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 shock not only of 220 V (from the power cord), but also a shock of about 450 V, which is quite unpleasant (tested on myself).

Very important! Before you check the LED driver for functionality and connect it to the power source, you should once again visually check the correctness assembled circuit. Defeat electric shock It is dangerous to life, and the 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 can be purchased at electrical stores or online resources. The second option is more affordable. In addition, many manufacturers offer free shipping. Let's consider some models with an input voltage of 220 Vs technical characteristics and cost as of December 2017.

Looking at the prices, we can say that making a current converter yourself is more suitable for those for whom this is just a hobby. You can purchase such a device quite inexpensively.

Summarize

When choosing a current converter for LED lamps, you should carefully calculate everything. Any error may lead to a reduction in the service life of the purchased device. Despite the low cost of the stabilizer, it is quite unpleasant to constantly throw money away. Only in this case will the driver serve its intended duration. And when self-production Follow electrical safety rules and be careful and attentive when assembling the circuit.

We hope that the information provided today was useful to our reader. Any questions you may have can be asked 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:

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

How to make a driver for LEDs

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

Required materials and tools

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

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

PCB development board for quick installation

Simple driver circuit for 1 W LED

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

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

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

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

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

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

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

Another one simple circuit drivers based on linear controlled voltage stabilizer LM317:

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

where I is the current strength in amperes.

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

This scheme is discussed more clearly in the following video:

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

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

Power driver circuit with PWM input

Below is a circuit for powering high-power LEDs:

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

Driver Features

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

Operating principle

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

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

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

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

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

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

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

Assembling and configuring the driver

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

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

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

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

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

List of elements:

Conclusion

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