LED lamp driver selection rules: views, purpose + connection

LED lamps have become widespread, and as a result, active production of secondary power sources has begun. The LED lamp driver is capable of stably maintaining the set current values ​​at the device output, stabilizing the voltage passing through the diode chain.

We will tell all about the types and principles of operation of a current conversion device for the operation of a diode bulb. The article proposed by us provides guidelines for choosing a driver and gives useful recommendations. Independent household electricians we will find proven in practice wiring diagrams.

Purpose and scope

Diode crystals consist of two semiconductors - the anode (plus) and the cathode (minus), which are responsible for the transformation of electrical signals. One area has P-type conductivity, the second - N. When a power source is connected, current flows through these elements.

Due to this polarity, the electrons from the P-type zone rush into the N-type zone, and vice versa, the charges from point N will rush towards R. However, each section of the area has its own borders, called Pn transitions. In these areas, the particles meet and mutually absorb or recombine.

During the P – N junctions, the voltage is reduced by a certain number of volts, always the same for each circuit element. Given these values, the driver stabilizes the input current and forms a constant value at the output.

What is the required power and what values ​​of losses during the P-N passage are indicated in the passport of the LED device. Therefore, when Choosing a diode bulb It is necessary to consider the parameters of the power supply, the range of which should be sufficient to compensate for the lost energy.

Power supplies with voltages from 10 to 36 V are used to equip lighting devices.

The technique can be of various types:

• headlights of cars, bicycles, motorcycles, etc .;
• small portable or street lights;
• LED lineribbons ceiling light bulbs and modules.

However for low power LEDs, and also in the case of using constant voltage, the drivers are allowed not to use. Instead of them, a resistor is introduced into the circuit, also powered by 220 V.

The principle of operation of the power supply

Let us see what the differences between the voltage source and the power supply are. As an example, consider the scheme shown below.

By connecting to a 12 V power supply a 40 Ohm resistor, a current of 300 mA will flow through it (Figure A). With parallel connection to the circuit of the second resistor, the current value will be - 600 mA (B). However, the voltage will be unchanged.

Now we will look at how the values ​​change if resistors are connected to the power supply in the circuit. Similarly, we introduce a 40 ohm resistor with a driver of 300 mA. The latter creates a voltage of 12 V on it (scheme B).

If the circuit is composed of two resistors, then the current value is unchanged, and the voltage will be 6 V (H).

Making conclusions, we can say that a quality converter supplies the load with a rated current even when the voltage drops. Accordingly, diode crystals of 2 V or 3 V and a current of 300 mA will burn equally brightly with reduced voltage.

Distinctive characteristics of the converter

One of the most important indicators is the transmitted power under load. The device can not be overloaded and try to get the maximum possible results.

Incorrect use contributes to the rapid failure of not only the viewing mechanism, but also LED chips.

The main factors affecting the work include:

• constituent elements used in the assembly process;
• degree of protection (IP);
• minimum and maximum values ​​of the input and output;
• manufacturer.

Modern models of converters are manufactured on the basis of microcircuits and apply the technology of pulse-width conversions (PWM).

Such devices have a high degree of protection against short circuits, network overloads, and also have an increased efficiency.

Current converter selection rules

To purchase a LED lamp converter, you should study the key instrument characteristics. It is necessary to rely on the output voltage, rated current and output power.

Power of light diodes

Let us first analyze the output voltage, which is subject to several factors:

• the value of the voltage loss on the P – N junctions of the crystals;
• the number of light diodes in the chain;
• connection diagram.

The parameters of the rated current can be determined by the characteristic features of the consumer, namely the power of the LED elements and the degree of their brightness.

This indicator will affect the current consumed by the crystals, the range of which varies based on the required brightness. The task of the converter is to provide these elements with the supply of the required amount of energy.

The power of the device depends on the strength of each LED element, their color and quantity.

For the calculation of energy consumption using the following formula:

P_H = P_LED * N,

Where

• P_LED - electric load created by one diode,
• N is the number of crystals in the chain.

These figures should not be less than the power of the driver. Now it is necessary to determine the required nominal value.

Maximum power of the device

It is necessary to take into account the fact that in order to ensure stable operation of the converter, its nominal values ​​should exceed the received value P by 20-30%_H.

Thus, the formula takes the form:

P_max ≥ (1,2..1,3) * P_H,

where P_max - rated power supply unit.

In addition to the power and number of consumers on the board, the load force is also subject to the color factors of the consumer. At the same current, depending on the shade, they have different indicators of voltage drop.

Take for example, the LEDs of the American company Cree from the XP-E line in red.

Their characteristics are as follows:

• voltage drop of 1.9-2.4 V;
• current 350 mA;
• average power consumption of 750 mW.

An analogue of green color with the same current will have completely different indicators: losses at P – N junctions 3.3–3.9 V, and power 1.25 W.

Accordingly, we can draw conclusions: a driver designed for 10 W is used to power twelve red crystals or eight green ones.

LED connection diagram

Driver selection should be made after determining the LED consumer connection scheme. If you first purchase light diodes, and then pick up a converter for them, this process will be accompanied by a lot of difficulties.

To find a device that provides the work of just such a number of consumers with a given connection scheme, you will have to spend a lot of time.

Let's give an example with six consumers. The voltage losses they have are 3 V, the consumed current is 300 mA. To connect them you can use one of the methods, and in each case the required parameters of the power supply will be different.

In our case, with a serial connection, a 18 V block with a current of 300 mA is required. The main advantage of this method is that the same force passes through the entire line, respectively, all the diodes are lit with identical brightness.

If parallel placement is used, it is enough to use a 9 V converter, however, the current consumption values ​​will be doubled in comparison with the previous method.

If a sequential method with the formation of pairs of two LEDs is used, a driver with the same indicators as in the previous case is used. In this case, the brightness of the illumination will be already uniform.

However, even here there were no negative nuances: when energizing the group, due to the spread of characteristics, one of LEDs can open faster than the second, respectively, and through it the current doubly exceeding the nominal value.

Many species LED light for home lighting designed for such short-term leaps, but this method refers to the less popular.

Types of drivers by device type

Devices that convert 220 V power to the required indicators for LEDs are conventionally divided into three categories: electronic; based on capacitors; dimmable.

The market of lighting accessories is represented by a wide variety of driver models, mainly from the Chinese manufacturer. And despite the low price range, from these devices, you can choose quite a decent option. However, it is worth paying attention to the warranty card, t. not all products are of acceptable quality.

Electronic view of the device

Ideally, the electronic converter should be equipped with a transistor. Its role is to carry out the unloading of the adjusting chip. To eliminate or maximize ripple smoothing, a capacitor is mounted at the output.

This type of device belongs to an expensive category, but it is capable of stabilizing current up to 750 mA, which the ballast mechanisms are incapable of.

Pulsing is not the only flaw in converters. The second can be called electromagnetic interference of the high-frequency (HF) range. So, if other electrical devices, for example, a radio, are connected to a socket connected to a lamp, you can expect interference with the reception of digital FM frequencies, television, a router, etc.

In an optional device of a high-quality instrument, there should be two capacitors: one is electrolytic for smoothing pulsations, the other is ceramic, for lowering the HF. However, this combination can be met infrequently, especially if we talk about Chinese products.

Due to the high efficiency (up to 95%), such mechanisms are suitable for high-power devices used in various spheres, for example, for car tuning, in street lighting devices, and also household LED sources.

Capacitor Based Power Supply

Now turn to not so popular devices - based on capacitors. Almost all the schemes of low-cost LED lamps, where these types of drivers are used, have similar characteristics.

However, due to modifications by the manufacturer, they undergo changes, for example, the removal of any element of the chain. Especially often this detail is one of the capacitors - smoothing.

There are only two advantages of such mechanisms: they are available for self-assembly, and their efficiency is equal to one hundred percent, since the losses will be only at pn junctions and resistances.

The same number of negative sides: low electrical safety and a high degree of pulsation. The second disadvantage is about 100 Hz and is formed as a result of rectification of alternating voltage. The GOST registers the allowable ripple rate of 10-20%, depending on the purpose of the room where the lighting device is installed.

The only way to smooth this drawback is to select a capacitor with the correct rating. Nevertheless, one should not count on the complete elimination of the problem - such a solution can only smooth out the intensity of the bursts.

Dimmable Current Transmitters

Drivers dimmers for dimmable LED bulbs allow you to change the incoming and outgoing current indicators, while reducing or increasing the brightness of the light emitted by the diodes.

There are two connection methods:

• the first involves a smooth start;
• the second is pulsed.

Consider the principle of operation of dimmable drivers based on the CPC9909 chip used as a regulating device for LED circuits, including those with high brightness.

With a soft start, the microcircuit with a driver ensures the gradual inclusion of diodes with increasing brightness. For this process, two resistors are used, connected to the LD terminal, designed to perform the smooth dimming task. This is how an important task is realized - the extension of the life of the LED elements.

The same output provides analog regulation - a 2.2 kΩ resistor is changed to a more powerful alternating analog - 5.1 kΩ. Thus, a gradual change in output potential is achieved.

The use of the second method implies the application of rectangular pulses to the low-frequency output of the PWMD. In this case, either a microcontroller or a pulse generator is used, which are necessarily separated by an optocoupler.

With or without a hull?

Drivers are issued in the case or without. The first option is the most common and more expensive. Such devices are protected from moisture and dust particles.

Adaptations of the second type are applied when carrying out the hidden installation and, respectively, differ in cheapness.

Each of them differs permissible temperature during operation - it is also necessary to pay attention to the selection.

Classic driver scheme

For self-assembly of the LED power supply, let's deal with the simplest device of the pulse type, which does not have galvanic isolation. The main advantage of this kind of circuit is simple connection and reliable operation.

The scheme of such a mechanism is composed of three main cascade areas:

1. Voltage separator on capacitance.
2. Rectifier.
3. Surge Protectors.

The first section - the opposition exerted by the alternating current on the capacitor C1 with a resistor. The latter is required solely for self-charging of the inert element. It does not affect the operation of the circuit.

When the resulting half-wave voltage passes through the capacitor, the current flows until the plates are fully charged. The smaller the capacity of the mechanism, the less time will be spent on its full charge.

For example, a device with a volume of 0.3-0.4 microfarad charges during a 1/10 half-wave period, i.e. only a tenth of the passing voltage will pass through this section.

The second stage is an electrical device that converts (rectifying) alternating current into a pulsating one. This process is called full-wave. Since one part of the half-wave was smoothed by a capacitor, at the output of this section the direct current will be equal to 20-25 V.

The third stage is based on a smoothing stabilizing filter - an electrolytic capacitor. The choice of its capacitive parameters depends on the load force.

Since the assembled circuit reproduces its work at once, it is impossible to touch bare wires, since the current flow reaches tens of amperes - the lines are pre-insulated.

Conclusions and useful video on the topic

All the difficulties that a radio amateur may encounter, picking up a converter for high-power LED lamps, are described in detail in the video:

Key features of self-connection of the converter device in the electrical circuit:

Step-by-step briefing describing the process of assembling an LED driver with improvised tools by hand:

Despite the tens of thousands of hours of uninterrupted operation of LED lamps declared by the manufacturer, there are many factors that significantly reduce these figures.

Drivers are designed to smooth out all current bounces in the electrical system. Their choice or self-assembly should be approached responsibly after the miscalculation of all the necessary parameters.

Tell us how to pick up the driver for the LED light bulb. Share your arguments and ways to stabilize the voltage supply to a diode lighting device. Leave comments in the block below, ask questions, post pictures on the topic of the article.