LED is a feature-sensitive semiconductor device with negative temperature characteristics, so it needs to be in stable working state and protection in the application process, thus generating the concept of drive. LED devices require almost strict driving power. Unlike ordinary incandescent bulbs, LED can directly connect to 220V ac power supply.
LED constant current drive
LED is 2 ~ 3 v low voltage drive, have to design complex conversion circuit, different USES of LED lights, to be equipped with different power adapters.
In the international market, foreign customers have very high requirements on the efficiency conversion, effective power, constant current accuracy, power life and electromagnetic compatibility of LED drive power supply. The design of a good power supply must comprehensively consider these factors, because the role of power in the whole lamp is as important as the human heart.
When using LED as display or other lighting equipment or backlight, it needs to be driven by constant current. The main reasons are:
1. Avoid driving current exceeding the maximum rating, affecting its reliability.
2. Obtain the expected brightness requirements, and ensure the consistency of the brightness and chroma of each LED.
According to the power grid rules and the characteristics of LED drive power, the following points should be taken into account in the selection and design of LED drive power:
1. High reliability: especially the drive power of LED street lamp, which is installed in high altitude, difficult to maintain and expensive.
2. High efficiency: LED luminous efficiency decreases with the increase of temperature, so heat dissipation is very important. Especially the power is installed in the lamp
LED is an energy-saving product, with high driving power efficiency, low power consumption, and less heat in the lamp, which is conducive to reducing the temperature rise of the lamp. Delay LED light decay.
3. High power factor: power factor is the requirement of power grid for load. General 70 watts of electrical appliances, no mandatory indicators. Although the power is not large single electrical appliances with low power factor little impact on the grid, but at night we light, the same load is too concentrated, will produce more serious pollution to the grid. For 30 w ~40 w LED drive power supply, it is said that in the near future, there may be certain power factor requirements.
4. Constant current output power supply mode;
1) multi-channel constant current output, flexible combination, one LED fault, does not affect other LED work, slightly higher cost.
2) direct constant current power supply, LED series or parallel operation. Low cost, but poor flexibility, one LED failure, affect other LED operation.
These two forms coexist for a period of time. Multi-channel constant current output power supply mode, in terms of cost and performance will be better. Maybe it's going to be the mainstream.
5. Surge protection: LED anti-surge ability is relatively poor, especially anti-reverse voltage ability. Strengthening protection in this area is also important. Some LED lights are installed outdoors, such as LED street lamps. Due to the activation of power grid load and the induction of lightning strike, various surges will be invaded from the power grid system, and some surges will cause LED damage. Therefore, LED drive power should have the ability to suppress the invasion of surge and protect LED from being damaged.
6. Protection function: in addition to conventional protection function, it is better to add negative feedback of LED temperature in constant current output to prevent LED temperature from being too high.
7. Protection: lamp outside the installation type, power structure to waterproof, moistureproof, shell to be light resistant.
8. The life of the drive power should match the life of the LED.
9. To meet the requirements of safety and electromagnetic compatibility.