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How to correctly understand the LED driver?

Electricity has an important effect on human life. It is the basis of energy acquisition, transformation, and transmission, electronic information technology. The discovery of electricity can be said to be a revolution in human history, the kinetic energy generated by it is continuously released every day, and the human demand for electricity exaggerated that its role is no less than the human world’s oxygen, if there is no electricity, … Human civilization will continue to explore in the dark…

Power exists in every aspect of our lives. Such as lighting; power tools; power transportation; heating; science and technology research; network media; Social Communication; Military Aerospace; industrial and agricultural development…

I. Power


The so-called power supply is the constant output of the electrical energy source of electromotive force!

The law of energy transfer! All the kinetic energy, heat energy, and chemical energy can be converted into electrical energy!

In a circuit, a power supply is a device that provides electrical energy by converting other forms of energy into electrical energy; an electrical appliance is a device that consumes electrical energy by converting electrical energy into other forms of energy.

A power supply is a device, also called a power supply unit, that supplies power to all the components of a computer. The power of the power supply, current, and voltage stability will directly affect the performance and life of the computer.

Dry cells and so on are called power supplies. Through the transformer and rectifier, the AC to DC power devices is called rectifier power. An electronic device that provides a signal is called a signal source. The transistor amplifies the signal sent in front of it and sends the amplified signal to the circuit behind it. The transistor can also be seen as a signal source for the circuit behind it. A rectifying power source or signal source is sometimes called a power supply.

Power source category:

The ordinary power supply can be divided into many kinds: PC power supply, rectifier power supply, custom power supply, heating power supply, welding power supply/ARC power supply, electroplating power supply, switching power supply, inverter power supply, AC power supply, DC power supply, DC/DC power supply, communication power supply, module power supply, frequency conversion power supply, UPS Power Supply, EPS emergency power supply, purification power supply, network power supply, power operation power supply, adapter power supply, linear power supply, power controller/driver, power supply, other ordinary power supply, inverter power supply, parameter power supply, voltage regulation power supply, transformer power supply.

ENE TECH LED Solar Street Light

II. LED driver

1. What is a LED driver?

An LED driver converts a power supply into a specific voltage and current that drives the LED’s voltage converter. In general, an LED driver is a converter. Its function is to turn our common electricity or other power supply into the voltage and current suitable for use by LED. Through its conversion, the LED works and emits light.

In general: LED power supply input includes high-voltage power frequency AC (i. e. electricity), low-voltage DC, high-voltage DC, and low-voltage high-frequency AC (such as the output of electronic transformers). The output of the LED power supply is a mostly constant current source which can change the voltage with the change of LED voltage drop.

The core components of an LED power supply include a switch controller, inductor, MOSFET, feedback resistor, input filter, output filter, and so on. According to the requirements of different occasions, there should be an input over-voltage protection circuit, input under-voltage protection circuit, LED open-circuit protection, and over-current protection circuit.

LED drive function which we used before quartz lamp cup transformer, fluorescent lamp, energy-saving lamp, metal halide lamp ballast is no different. It’s all about keeping the light source stable. Therefore, it is often called led ballast, led transformer, etc., but led practitioners are generally called drive, one is to be able to distinguish from other converters, and the other is because the working principle of the three is different. And three to show our professionalism. So down the line, let’s say led drive.

2. LED driver characteristics

(1) High reliability

Especially like the LED street lamp drive power supply, installed at a high altitude, maintenance is not convenient, and the cost of maintenance is also large.

(2) High efficiency

LED is an energy-saving product, driving power supply to high efficiency. For the power installed in the lamp, junction cooling is very important. The efficiency of the power supply is high, its loss of power is small, in the lamps and lanterns heat is small, also reduced the temperature rise of lamps and lanterns. It is advantageous to delay the light decay of LED.

(3) High power factor

The power factor is the load requirement of the power grid. General 70 watts of electrical appliances, there are no mandatory indicators. Although the low power factor of a single electrical appliance has little influence on the power grid, the use of a large amount of lighting at night, the same kind of load is too concentrated, the power grid will produce more serious pollution. For the 30-40 Watt LED power supply, it is said that in the near future, there may be certain power factor requirements.

(4) The driving mode

Now there are two common: one is a constant voltage source for multiple constant current sources, each constant current source separately from each LED power supply. This way, the combination of flexible, all-the-way LED failure, does not affect the work of other LEDs, but the cost will be slightly higher. The other is direct constant current power supply LED series or parallel operation.

Its advantages are lower cost, and poor flexibility, but also to solve a certain LED failure, does not affect the operation of other LED problems. The two forms coexist over a period of time. Multi-channel constant current output power supply, in the cost and performance, will be better. Maybe it will be the mainstream direction in the future.

ene tech solar street light

(5) Surge protection

LED anti-surge ability is relatively poor, especially anti-reverse voltage ability. It is also important to strengthen protection in this area. Some LED lights are installed outdoors, such as LED street lights.

Due to the load of the grid and lightning induction, the grid system will invade a variety of surges, some surges will lead to LED damage. As for the frequent replacement of power supply and lamps, LED power supply to have a surge suppression intrusion, to protect the ability of LED is not damaged.

(6) Protection function

In addition to the conventional power protection function, it is best to increase the constant-current output LED temperature negative feedback to prevent LED temperature is too high; to comply with safety and electromagnetic compatibility requirements.

3. There are two main types of drivers:

(1) Constant current:

A. The output current of the constant current drive circuit is constant, but the output DC voltage changes in a certain range with the difference of the load resistance value. The lower the load resistance value is, the lower the output voltage is, and the greater the load resistance value is, the higher the output voltage.

B. The constant current circuit is not afraid of load to short-circuit, but the load is strictly prohibited to open the circuit.

C. Constant-current drives circuit to drive LED is more ideal but relatively expensive.

D. Should pay attention to the use of maximum withstand current and voltage value, which limits the number of LED use.

(2) Voltage regulator:

A. when the parameters of the circuit are determined, the output voltage is fixed, but the output current changes with the load;

B. The voltage regulator circuit is not afraid of open load, but the load is strictly prohibited from completely short-circuiting.

C. To drive the LED with a voltage regulator circuit, each series need to add a suitable resistance to make each series of LED display brightness average;

D.Brightness will be rectified by the voltage changes.

4. According to the LED street lamp driving power, the current power supply on the market is divided into two kinds: the whole constant current and the road-by-road constant current. These two kinds of working methods have their own advantages and disadvantages:

Comparison of advantages and disadvantages of whole constant current by path constant current

Integral constant current

A. the cost is relatively low.

B. Electromagnetic compatibility is easy to handle.

C. The LED light source board is easy to design and can be directly connected in parallel.

D. the overall efficiency can reach more than 90%

E. Wiring is easy, the light source plate only needs 2 wires on it.

Constant current by the way

A. It was expensive.

B. Electromagnetic compatibility is not easy to handle.

C.The overall efficiency is up to 85%

D. Wiring is easy, the light source plate only needs 2 wires on it.

From the above comparison can also be seen, that although the constant current path has more shortcomings, the cost is also relatively high. But it can really protect LEDs and extend the life of LEDs, so constant current is the trend of the future.

To achieve high stability of the constant-current source power supply, specifically:

4.1 High stability, high power factor.

4.2 A long life span of at least 5000 hours.

4.3 Higher overall efficiency.

4.4 Strong adaptability to the environment. Such as working environment temperature-20-60 degrees lightning 4KV and so on.

4.5 IP66 or higher.

In response to the above requirements solve the following problems.

A. To meet the high power factor and efficiency, LLC efficiency is relatively high, but not stable enough. Because it is on the transformer leakage resonance work. The efficiency of forwarding plus synchronous rectifier is also high, but at present, the technology of forwarding synchronous rectifiers is more complex.

The quasi-resonant plus synchronous rectification has lower efficiency than the above two, but it has good stability and the scheme is mature. Therefore, the choice of quasi-resonant plus synchronous rectifier.

B. Because the quasi-resonant plus synchronous rectifier scheme can not be without electrolytic capacitors. Therefore, in the design and selection of components larger margin, higher life of electrolytic capacitors. At the same time, in order to meet the requirements of the working environment, the use of components at least -20-105 degrees of temperature resistance.

C. In order to meet the requirements of electromagnetic compatibility and lightning stroke, it is necessary to add a lightning protection circuit and EMC filter circuit. Some high-frequency areas also do shielding processing.

D. The power supply is treated by filling glue to meet the requirement of IP protection grade.

5. The status of LED power

The led power supply is also a supporting product, the current market power quality is uneven, according to the existing information of the inquiry and project implementation encountered in the problem of bad light roughly analyzed the reasons for the current shortage of LED driver power:

A. the technical personnel of the company that produces LED lighting and related products does not know enough about the switching power supply. The power supply mode can work normally, but some critical evaluation and electromagnetic compatibility considerations are not enough, there must be hidden dangers.

B. most of the LED power production enterprises are from the ordinary switching power supply transformation to do LED power, LED characteristics and use of knowledge is not enough.

C.the current standard on LED is almost no, most of the reference switching power supply and electronic rectifier standards.

D. now most of the LED power supply is not uniform, so the amount of most is relatively small. The purchase quantity is small, the price is on the high side, moreover the component supplier also not quite cooperates.

E. LED power supply stability: wide voltage input, high temperature, low-temperature work, over-temperature, over-voltage protection, and other problems have not been solved one by one.

6. LED power needs to be solved

First of all, the overall life of the drive circuit, especially the key components such as capacitor at high-temperature life directly affects the life of the power supply;

Second, LED drivers should challenge higher conversion efficiency, especially when driving high-power LEDs, because all the power not output as light is dissipated as heat, and the power conversion efficiency is too low, affecting the LED energy-saving effect of the play;

Once again, in the application of small power (1 -5 w), the proportion of the cost of constant current drive power supply has been close to 1/3, has been close to the cost of the light source, to some extent affecting the marketing.

If you want to know more about the LED drivers, please don’t hesitate to get in touch with us.


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