The LED drive power supply is a power converter that converts the power supply into a specific voltage and current to drive the LED to emit light. Usually: the input of the LED drive power supply includes high-voltage power frequency AC (that is, mains power), low-voltage DC, high-voltage DC, low-voltage high-voltage Frequency AC (such as the output of an electronic transformer), etc.
The output of the LED drive power supply is mostly a constant current source that can change the voltage with the change of the LED forward voltage drop value.
According to the power consumption rules of the power grid and the characteristic requirements of the LED drive power supply, the following points should be considered when selecting and designing the LED drive power supply:
1. High reliability Especially like the driving power of LED street lamps, which are installed at high altitude and have a waterproof aluminum casing driving power. If the quality is good, it is not easy to break and reduces the number of maintenance.
2. High-efficiency LED is an energy-saving product, and the efficiency of the driving power supply must be high. It is especially important for the structure where the power supply is installed in the lamp. Because the luminous efficiency of LED decreases with the increase of LED temperature, the heat dissipation of LED is very important. The efficiency of the power supply is high, its power consumption is small, and the heat generated in the lamp is small, which also reduces the temperature rise of the lamp. It is beneficial to delay the light decay of LED.
3. High power factor Power factor is the requirement of the grid for the load. Generally, there is no mandatory index for electrical appliances below 70 watts. Although the low power factor of a single electrical appliance with low power has little impact on the power grid, but when everyone lights up at night, the similar loads are too concentrated, which will cause serious pollution to the power grid. For 30W~40W LED drive power, it is said that in the near future, there may be certain index requirements for power factor.
4. There are two common driving methods: one is a constant voltage source for multiple constant current sources, and each constant current source supplies power to each LED individually. In this way, the combination is flexible, and the failure of one LED will not affect the work of other LEDs, but the cost will be slightly higher. The other is direct constant current power supply, LEDs run in series or in parallel. Its advantage is that the cost is lower, but the flexibility is poor, and it is necessary to solve the problem that a certain LED failure will affect the operation of other LEDs. These two forms coexisted for a period of time. The multi-channel constant current output power supply method will be better in terms of cost and performance. Maybe it will be the mainstream direction in the future.
5. Surge protection The ability of LED to resist surge is relatively poor, especially the ability to resist reverse voltage. Strengthening protection in this area is also important. Some LED lights are installed outdoors, such as LED street lights. Due to the swaying 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 drive power supply must have the ability to suppress the intrusion of the surge and protect the LED from being damaged.
6. Protection function In addition to the conventional protection function of the power supply, it is better to add LED temperature negative feedback to the constant current output to prevent the LED temperature from being too high.
7. In terms of protection, the lamps are installed outside, the power supply structure should be waterproof and moisture-proof, and the shell should be light-resistant.
8. The life of the driving power supply should match the life of the LED.
9. It must meet the requirements of safety regulations and electromagnetic compatibility.
With the increasingly widespread application of LEDs, the performance of LED drive power will be more and more suitable for LED requirements.
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