A Brief Discussion on LED Driver Power Supply

LED has the characteristics of low energy consumption, long life, low heat generation and environmental protection, and has been widely used in many fields, such as:

1 Lighting field Street lights, tunnel lights, LED grille lights, LED indoor lights, LED ceiling lights, etc.

2 Landscape lighting buildings, roads and bridges, square building facilities, lawn lights, curtain wall lights, etc.

3. Used as backlight for mobile phones, computers, etc.

4 Information plane Display Display board, dynamic billboard, simulation animation, sports stadium, industry and commerce, other industries, etc.

5. Indicator lights and reading lights inside the car, brake lights, tail lights, turn signals, side lights, etc. outside the car

6 Application in special fields: explosion-proof lamps, mining lamps in mining production, etc.

LED is a light-emitting tube with diode characteristics, which can only be powered in one direction. Usually, the brightness output of LED is proportional to the current passing through the LED, but white light LED will saturate under high current, and the luminous efficiency will be greatly reduced or even fail. Therefore, the current used by LED cannot exceed its specification rating. In addition, the brightness output of LED is inversely proportional to the temperature, so the power supply should be used to minimize heating and design a good heat dissipation system.

At present, LEDs are all driven by DC , so a power adapter, i.e., LED driver power supply, needs to be added between the mains and the LED. Its function is to convert the AC mains into DC power suitable for LEDs. According to the power usage rules of the power grid and the driving characteristics of LEDs, the following points should be considered when selecting and designing LED driver power supplies:

1. High reliability, especially for LED street lamps , the driving power supply is installed at high altitude, which is inconvenient to maintain and the maintenance cost is also high.

2. High efficiency LED is an energy-saving product, and the efficiency of the driving power supply must be high. This is especially important for the structure where the power supply is installed in the lamp. Because the luminous efficiency of LED decreases as the temperature of LED increases, the heat dissipation of LED is very important. The high efficiency of the power supply means that its power consumption is small, and the heat generated in the lamp is small, which reduces the temperature rise of the lamp. This is beneficial to delaying the light decay of LED.

3. High power factor Power factor is the load requirement of the power grid. Generally, there is no mandatory index for electrical appliances below 70 watts. Although a low power factor of a single electrical appliance with low power has little impact on the power grid, when everyone turns on lights at night, the same load is too concentrated, which will cause serious pollution to the power grid. For 30W~40W LED driver power supplies, it is said that in the near future, there may be certain index requirements for power factor.

4. There are two common driving modes: one is that a constant voltage source supplies multiple constant current sources, and each constant current source supplies power to each LED separately. This mode has flexible combination, and the failure of one LED does not affect the operation of other LEDs, but the cost will be slightly higher. The other is direct constant current power supply, and the LEDs are operated in series or parallel. Its advantage is that the cost is lower, but the flexibility is poor, and the problem of a certain LED failure not affecting the operation of other LEDs must be solved. These two forms coexist for a period of time. The multi-channel constant current output power supply mode will be better in terms of cost and performance. Perhaps it will be the mainstream direction in the future.

5. Surge protection LEDs have poor surge resistance, especially reverse voltage resistance. It is also important to strengthen this protection. Some LED lights are installed outdoors, such as LED street lights. Due to the start-up of the grid load and the induction of lightning strikes, various surges will invade from the grid system, and some surges will cause damage to the LED. Therefore, the LED driver power supply must have the ability to suppress the intrusion of surges and protect the LED from damage.

6. Protection function In addition to the conventional protection function of the power supply, it is best to add LED temperature negative feedback in the constant current output to prevent the LED temperature from being too high.

7 In terms of protection, the lamp is installed outside, the power supply structure should be waterproof and moisture-proof, and the outer shell should be sun-resistant.

8 The life of the driver power supply should be compatible with the life of the LED.

9. It must comply with safety regulations and electromagnetic compatibility requirements.

As LEDs are increasingly used, the performance of LED driver power supplies will become more and more suitable for LED requirements.