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.
The content of the article:
- Purpose and scope
- The principle of operation of the power supply
- Distinctive characteristics of the converter
Current converter selection rules
- Power of light diodes
- Maximum power of the device
- LED connection diagram
Types of drivers by device type
- Electronic view of the device
- Capacitor Based Power Supply
- Dimmable Current Transmitters
- With or without a hull?
- Classic driver scheme
- Conclusions and useful video on the topic
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.
The diode belongs to semiconductor elements and has only one p – n junction. For this reason, the main characteristic that determines the degree of brightness of their glow is not the voltage, but the current
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.
In order for high-power LEDs to work out the time specified in the characteristics, a stabilizing device is required - the driver. The electronic mechanism case always shows its output voltage.
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.
Despite the connection of two resistors to the power supply, the second output will produce a constant voltage, since under ideal conditions it does not obey the load
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).
The driver, unlike the voltage source, maintains the current parameters at the output, however the voltage power may change
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;
Modern models of converters are manufactured on the basis of microcircuits and apply the technology of pulse-width conversions (PWM).
During the operation of the power supply unit, the pulse-width modulation method is implemented to regulate the output voltage, while the output maintains a similar kind of current as that at the input
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 output voltage must be greater than or identical to the total amount of energy expended in each electrical circuit unit.
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:
PH = PLED * N,
- PLED - 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:
Pmax ≥ (1,2..1,3) * PH,
where Pmax - 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.
The driver for the LED lamp should produce the amount of current that is necessary to ensure maximum brightness. When selecting the device, the buyer must remember that the power must be greater than all LEDs use
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.
The disadvantage of the alternate arrangement of diodes is the need for a power supply with high voltage, if there are a lot of crystals in the circuit
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.
The disadvantage of parallel placement of consumers is the difference in brightness of the glow of each chain. Such a negative phenomenon occurs due to the variation of the parameters of the diodes due to differences between the current passing through each line.
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.
The method of sequential arrangement of two diodes can not be applied with the replacement of the number of crystals in the group - 3 or more. Such restrictions are due to the fact that too much current can pass through one element, and this creates the probability of failure of the entire circuit.
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.
The newest drivers are mainly installed on light bulbs with an E27 socket. An exception to the rule is Gauss GU5.3 products. They are equipped with a transformerless converter. However, the degree of pulsation in them reaches several hundred Hz.
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.
Those who have common concepts in such wiring diagrams can independently select the output parameters of the electronic converter, changing the value of the resistors
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.
Due to the uncontrolled filling of the market with cheap and low-quality goods, users can “feel” 100% pulsation in the lamps. Even without going into their device, it can be argued that the smoothing element is removed from the circuit.
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.
The scheme of the standard inclusion CPC9909 with a power of 220 V. According to the schematic instructions, it is possible to control one or several powerful consumers.
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.
The power supply of all the presented devices can be from the 12 V or 220 V. Despite the fact that unpackaged models win in price, they are significantly behind in terms of safety and reliability of the mechanism
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 220 V converter circuit is presented as a switching power supply. When assembling, it is necessary to follow all electrical safety rules, since there are no limits for current recovery.
The scheme of such a mechanism is composed of three main cascade areas:
- Voltage separator on capacitance.
- 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.
The nominal value of the resistor may be in the range of 100 kΩ-1 MΩ, with a power of 0.5-1 W. The capacitor must be electrolytic, and its effective peak voltage value is 400-500 V
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 straightening process in this area is performed according to the Gretz scheme. The diode bridge is selected, starting from the rated current and reverse voltage. The last value should not be less than 600 V
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.
Since the power supply of the LEDs should not exceed 12 V, for the circuit it is necessary to use a stabilizing element. For this, a capacitive filter is introduced. For example, you can use the model L7812
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.