Drivers for LEDs: types, characteristics and device selection criteria

Guarantee of brightness, efficiency and durability of the LED-sources is proper nutrition, which can provide a special electronic device - drivers for LEDs. They convert the AC voltage into a 220V DC voltage setpoint. To understand what kind of function is performed by converters and what to look for when choosing them, will analyze the main types and characteristics of devices.

Purpose LED-driver for LEDs

The main driver for the LED function is to provide a constant current passing through the LED-unit. The value of the current flowing through the semiconductor crystal parameters must match the passport LED. This will ensure the stability of the crystal glow and help avoid premature degradation. Also at a given current the voltage drop will correspond to the value required for p-n junction. Learn the proper voltage LED power supply, you can use the current-voltage characteristic.

Upon illumination of residential and office premises LED lamps and luminaires use a driver that power is supplied from AC 220V. In the automotive lighting (lights, DRL and so on.), Bicycle lamps, lanterns portable power sources used in the direct voltage of 9 to 36V. Some LEDs can be connected to a low power without the driver, but then turn on the LED circuit to the network resistor 220 must be paid.

driver output voltage range indicated in the two end values, between which a stable operation is ensured. There are adapters at intervals of up to several tens 3B. To power the circuitry of the 3 series-connected white LEDs, each having a power of 1 W is required driver output values ​​U - 9-12V, I - 350 mA. The voltage drop for each crystal will be about 3.3 V, and a total of 9,9V that enters the driver range.

Key Features converters

Before you buy a driver for LEDs, should be familiar with the basic characteristics of devices. These include output voltage, rated current and power. The output voltage of the converter depends on the voltage drop across the LED-source, as well as the connection method and the number of LEDs in a circuit. The current depends on the power and brightness of emitting diodes. The driver must provide a current to the LEDs, which is necessary for them to support the desired brightness.

One important characteristic of the power driver is considered which gives a unit load. On the driver a choice of power affects the power of each LED-unit, the total number of color and light LEDs. power calculation algorithm is that the maximum capacity of the device must not be lower than the consumption of LEDs:

P = P (led) × n,

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

Besides prerequisite should be performed, which would be provided when the power supply in the range of 25-30%. Thus maximum power value should be not less than the value (1.3 x P).

It should also take into account the color characteristics of LEDs. After various color semiconductor chips have a different amount of voltage drop when current passes through them of equal strength. Since the voltage drop of the red LED at a current of 350 mA is 1,9-2,4V, while its mean power value is 0.75 watts. At the analogue green voltage drop amount in the range from 3.3 to 3,9V and at the same current capacity will amount to 1.25 watts. So the driver for the LED 12B may be connected 16 red sources or LED-9 green.

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

What are the drivers for the LED on the device type

Drivers for LEDs are classified according to the type of device on the linear and pulse. The structure and a typical driver circuit for LEDs linear type is a current generator transistor with p-channel. Such devices provide a smooth current stabilization provided an unstable voltage on the input channel. They are simple and cheap devices, but have low efficiency, emit a lot of heat during operation, and can not be used as drivers for high-power LEDs.

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

Due to the high conversion efficiency (up to 95%) and compact devices, they are widely used for portable LED designs. In addition, the effectiveness of the devices has a positive effect on the duration of the functioning of the self-powered devices. Converters pulse type are compact and feature an extensive range of input voltages. A disadvantage of these devices is the high level of electromagnetic interference.

Useful advice! Acquire LED-driver to the selecting LED sources previously defined with the circuit of LEDs 220.

Before you pick up a driver for LEDs, it is necessary to know the conditions of its operation and the location of the LED devices. Pulse-width-drivers, which are based on a single chip, have small dimensions and are powered by a self-contained low-voltage sources. The main use of these devices - car tuning and LED lights. However, because of the simplified electronic circuit quality such converters are somewhat lower.

Dimmable LED drivers

Modern LED drivers compatible with devices dimming glow of semiconductor devices. Using dimmable driver allows you to control the light level in the areas: reducing light intensity during the day to emphasize or hide individual items in the interior, Zoned space. This, in turn, enables not only efficient use of electricity, but also saves resources of the LED light source.

Dimmable drivers come in two types. Some are connected between the power supply and LED-sources. Such devices are controlled energy supplied from the power source to the LEDs. At the heart of such devices uses a PWM control in which power is supplied to a load in the form of pulses. Pulse duration determines the amount of energy from a minimum to a maximum value. Drivers of this type are used mostly for LED modules with a fixed voltage such as LED strip, tickers, etc.

Dimmable converters of the second type control directly the power supply. Their principle of operation consists in the PWM control, and the control amount of current flowing through the LEDs. Dimmable drivers of this type are used for devices with LED-stabilized current. It is worth noting that the management of the LEDs through PWM control observed affecting the vision effects.

Comparing these two methods of control, it should be noted that the regulation of the current through the LED-sources there is not only a change in brightness, but also change the color of the glow. Thus, the white LEDs with a smaller current radiate yellowish light, while increasing - glow blue. When controlling the LEDs through PWM control observed adversely affecting the vision effects and high levels of electromagnetic interference. In this connection, the PWM control is used infrequently in contrast to current control.

a driver circuit for LEDs

Many manufacturers produce for the LED driver chip, allowing sources to supply the undervoltage. All existing drivers are divided into simple, made on the basis of 1-3 transistors and more complex with the use of a chip pulse-width modulation.

The company ON Semiconductor offers as a basis for a wide range of driver ICs. They differ acceptable cost, excellent conversion efficiency, economy and low electromagnetic pulses. Manufacturer represented type UC3845 pulse driver with the amount of current output to 1A. In such a chip driver circuit can be implemented for 10W LED.

Electronic components HV9910 (Supertex) is a popular chip for drivers, thanks to the simple circuit resolution and low price. It has a built-in voltage regulator and outputs for controlling the brightness as well as for programming the output switching frequency. The output current is up to 0,01A. On this chip might embody a simple driver for LEDs.

On the basis of the chip UCC28810 (pr-in of Texas Instruments) can create a driver circuit for high-power LEDs. In such a LED-driver circuit may be generated output voltage value of 70-85V for LED modules consisting of 28 LED-source current of 3 A.

Useful advice! If you are planning to buy a high-brightness LEDs 10W, for structures of them, you can use a pulse driver chip UCC28810.

Clare offers a driver to provide a simple pulse-type chip-based CPC 9909. It includes a transducer controller arranged in a compact housing. Due to the built-in voltage regulator inverter permitted power voltage from 8-550V. CPC circuit 9909 allows the driver to operate under a wide variation of temperature conditions of -50 to 80 ° C.

How to choose a driver for LEDs

On the market a wide range of drivers for LEDs from different manufacturers. Many of them, especially in China, are low cost. However, to buy such a device is not always advantageous, since most of them do not correspond to the stated characteristics. In addition, such drivers are not accompanied by a guarantee, and in the case of marriage, they can not return or be replaced by quality.

So there is a possibility of acquisition driver, declared capacity is 50 W. However, the reality is that this characteristic is intermittent and so the power is only short-term. In reality, such a device will work as a LED-driver 30W or 40W maximum. It can also be that the stuffing will miss some of the components responsible for the sustainable operation of the driver. Also can be used low-quality components and with little life, which is in fact married.

When you buy should pay attention to the indication of the brand product. On quality products is bound to be specified by the manufacturer, who will provide a guarantee and will be ready to answer for their products. It should be noted that the term driver service from trusted manufacturers will be much greater. The following is the approximate time of the drivers depending on the manufacturer:

• driver from questionable manufacturers - no more than 20 thousand. hours;
• average quality devices - about 50 thousand. hours;
• converter from a proven manufacturer with quality ingredients - over 70 thousand. hours.

Useful advice!What quality will the LED driver - you choose. However, it should be noted, that is particularly important to acquire proprietary transducer, when it comes to applying it for the spotlights of the LEDs and high-power lamps.

Calculation of drivers for LEDs

To determine the output voltage of the LED drivers, it is necessary to calculate the power ratio (W) to the value of current (A). For example, the driver has the following characteristics: power 3 W and a current of 0.3 A. Calculated ratio is 10V. Thus, it is the maximum value of the inverter output voltage.

Related article:

If it is necessary to connect three LED-source current of each of which is 0.3 mA at a voltage of 3V. By connecting to the LED driver of the devices, the output voltage is equal to 3V and current of 0.3 A. Collecting successively with two LED-source, the output voltage will be 6V and a current of 0.3 A. Adding in a daisy chain third LED obtain 9B and 0.3 A. In parallel connection 0.3A equally distributed between the LEDs to 0.1 A. By connecting the LEDs to a device at 0.3 A at a current value of 0.7, it will get only 0.3 A.

This is the mechanism of functioning of the LED driver. They provide a number of current for which they are designed. Way to connect LED-instrument in this case is irrelevant. There is a driver model, involving any number of LEDs connected to them. But then there is a limitation on the power LED-sources: it should not exceed the power of the driver. Drivers are available, designed for a certain number of LEDs connected to them are allowed to connect a smaller number of LEDs. But such drivers have low efficiency, in contrast to devices designed for a specific number of LED-device.

It should be noted that the driver, designed for a fixed number of emitting diodes provides for protection from emergency situations. These converters are not working properly, if they are to connect a smaller number of LEDs: they will flicker or will not light up at all. Thus, if the voltage connected to the driver without a corresponding load, it will become unstable.

Where to buy Drivers for LEDs

Buy LED-driver can be in specialized points of sale of electronic components. In addition much more convenient to see the products and order the required product with a catalog of relevant sites. In addition, the online stores you can buy not only the converters and LED lighting devices and related products: Power supplies, Control, connectivity, electronic components for repair and assembly driver for LEDs with their hands.

Company sells a huge assortment of drivers for LEDs, specifications and prices which can be seen in the price. Typically the product prices are indicative and are specified when ordering the project manager. The product range includes inverters of different power and the degree of protection used for indoor and outdoor lighting, as well as for lighting and car tuning.

Choosing a driver should take into account the conditions of its use and power consumption of the LED structure. Therefore, it is necessary to acquire the driver before buying LEDs. So, before you buy a driver for LEDs 12 volts, it is necessary to take into account that it must have a power reserve of about 25-30%. This is in order to reduce the risk of damage or complete failure of the device during short circuit or differential voltage. drive cost depends on the number of devices purchased, method of payment and delivery terms.

The table lists the basic parameters and dimensions of stabilizing voltage of 12 volts for the LED indicating their approximate prices:

Modification LD DC / AC 12 V	Dimensions, mm (w / w / g)	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	5-7h1	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 their hands

Using ready-made chips radio amateurs can independently collect various drivers for power LEDs. To do this you must be able to read circuit diagrams and have the skills to work with a soldering iron. For example, consider several options for LED-driver with his own hands for the LEDs.

Driver circuit for LED 3W can be implemented on the basis of chip PT4115 Chinese production PowTech. The chip may be used for powering devices over LED-1W and includes control units, which have sufficient output power transistor. Driver based PT4115 is highly effective and has a minimum number of binding components.

Overview PT4115 and technical parameters of its components:

• function luminescence brightness control (dimming);
• input voltage - 6-30V;
• output current - 1.2 A;
• deflection current stabilization to 5%;
• protection from stress fractures;
• the availability of terminals for dimming;
• efficiency - 97%.

IC has the following conclusions:

• the output switch - SW;
• for the signal and supply circuit portion - GND;
• for dimming - DIM;
• input current detector - CSN;
• supply voltage - VIN;

driver circuit for LEDs with their hands on the basis of PT4115

driver circuits for LED-power devices scattering power of 3 W can be performed in two variants. The first assumes that the power supply voltage of 6 to 30V. In another scheme provides power from the AC power source voltage of 12 to 18V. In this case, the diode bridge circuit is entered, the output of which the capacitor is installed. It contributes to the smoothing of voltage fluctuations, its capacity is 1000 microfarads.

a capacitor (CIN) for the first and second circuits of particular importance: this component is intended to reduce the ripple and to compensate for the accumulated energy inductance coil when closing MOP-transistor. In the absence of capacitor entire energy of the inductance through the semiconductor diode DSHB (D) falls in output voltage (VIN) and cause chip breakdown relative power.

Useful advice! Be sure to take into account that the connection driver for LEDs in the absence of the input capacitor is not allowed.

Given the number and how many LEDs consume, calculated inductance (L). The LED driver circuit inductance should be selected whose value 68-220 uH. This is evidenced by the technical documentation data. It is possible to prevent a small increase in the value L, however it should be noted that while the efficiency will decrease the overall circuit.

Once the voltage is applied, the current value when it passes through the resistor RS (works as a current sensor) and L will be zero. Furthermore, CS comparator analyzes the potential levels that are up resistor, and after him - the result is a high concentration at the outlet. Current flowing to the load increases to a certain value, controlled by RS. The current increases depending on the value of inductance and the voltage value.

Assembling the components' drivers

RT 4115 chip binding components are selected taking into account the manufacturer's instructions. CIN should be used for low impedance capacitor (a capacitor with low ESR), since the use of other analogues negative impact on driver efficiency. If the device is energized from the unit with stabilized current at the input will need one capacitor of 4.7 microfarad. It is recommended to place next to the chip. If alternating current is required to enter the solid tantalum capacitor, whose capacitance is not less than 100 microfarads.

The switching circuit for the LEDs 3 W must install the coil 68 uH. It should be located as close as possible to the conclusion SW. You can make your own coil. This would require the ring from the computer and the winding wire of the failed (ELP-0.35). As the diode D can be used 103 FR diode. Its parameters are: capacitance 15 pF, the recovery time of 150 ns, a temperature of -65 to 150 ° C. He can cope with the current pulses of up to 30 A.

The minimum value of the resistor RS in the LED driver circuit is 0.082 ohms, current - 1,2 A. To calculate the resistor, it is necessary to use the current required for the LED. The formula for calculation:

RS = 0,1 / I,

where I - the nominal value of LED-current source.

RS value in the LED driver circuit is 0.13 ohms, respectively current - 780 mA. If such a resistor is not possible to find, it is possible to use multiple low-impedance components using the calculation formula for the resistance of the parallel and series connection.

The layout of the LED driver for 10 Watt own hands

Compile the driver for high power LEDs can be independently, using electronic cards from the failed fluorescent lamps. Most often in such lamps burn out bulb. The electronic card is working, that allows the use of its components for homemade power supplies, drivers, and other devices. To work may require transistors, capacitors, diodes, inductors (chokes).

Defective lamp must be carefully disassembled with a screwdriver. To make the driver for LED 10W, use fluorescent lamp, which is 20 watts. This is necessary in order to choke with a margin could support the load. For a more powerful lamp must either select the appropriate charge, either replace the choke himself on analogue with a large core. For LED-sources with less power, you can adjust the number of winding turns.

Next, over the primary winding turns necessary to make 20 turns of wire and by means of soldering to connect the winding with a diode rectifier bridge. This is followed by applying voltage of 220V and measure the output voltage of the rectifier. Its value was 9,7V. LED-source through the ammeter consumes 0.83 A. Face value of the LED, 900 mA, but to too low current consumption will increase its service life. Assembling of the diode bridge is carried out by surface mounting.

A new board and a diode bridge can be placed in the base of the old table lamp. Thus, the LED driver can be collected independently of the available radio components from the failed devices.

Due to the fact that LEDs are quite demanding on the power supply, you must select the correct driver for it. If the inverter is selected properly, you can be sure that the parameters of LED-sources does not deteriorate and the LEDs serve their term.