According to the power consumption characteristics of the power grid, the requirements of LED characteristics and related LED products, three general principles should be followed when considering the selection of LED drive power:

 

 

 

1. According to the characteristics of LED current and voltage, it is ideal to make the drive. It can avoid the current change caused by the change of LED forward voltage, and the constant current makes the brightness of the LED stable.

 

 

 

2. In addition, the LED luminous flux is inversely proportional to the temperature, so in use, the constant current heating of the power supply should be minimized and a well-designed heat dissipation system should be minimized. Thereby reducing the operating temperature of the LED.

 

 

 

3. In order to ensure the overall life of the LED, the temperature of the LED must be controlled within a certain range.

 

 

The following are ten considerations for selecting LED drive power:

 

 

 

1. High reliability: LED products mainly have LED chips

 

And power supply, cooling shell, control circuit and other components. The quality of the LED power supply directly affects the quality of the product. In particular, LED street light products are difficult to install and expensive because they are installed at high altitudes.

 

 

 

2. High efficiency: LED is an energy-saving product, and the drive power must also meet the requirements of energy saving. Especially the structure in which the power supply is installed in the luminaire is particularly important. Because the luminous efficiency of the LED decreases as the temperature of the LED increases. The efficiency of the power supply is high, its power consumption is small, the heat generation in the lamp is small, and the temperature rise of the lamp is reduced. It can delay the light decay of LED.

 

 

 

3. Constant current driving method: In order to match the VI characteristics of the LED, the LED power supply must use the constant current driving method.

 

 

 

4, surge protection: LED anti-shock ability is relatively poor, so we must strengthen protection in this regard. Especially some products installed outdoors due to the start-up and thunder of the grid load. Therefore, the LED drive power must have the ability to suppress the intrusion of the surge and protect the LED from damage.

 

 

 

5. Temperature protection function: In addition to the conventional protection function of the power supply, it is best to add negative feedback of the LED chip temperature to the constant current output to prevent the LED chip PN section temperature from becoming too high.

 

 

 

6. LED power supply life: Do the best to match the life of the LED chip with the life of the drive power.

 

 

 

7. Working environment: Due to the difference in the environment of each place, the environment of the workplace where the LED lamp is located should be considered, such as temperature, humidity, and installation location. Considering the working mode of the power supply, if no soft-start circuit is added, the output will have a voltage spike immediately after power-on. In order to better protect the LED, a soft-start circuit is needed. This is a key factor in driving power stability.

 

 

 

8. Power factor of LED driving power supply: The power factor varies greatly when the same product is used in a large area, which is also a key point for energy-saving products.

 

 

 

9. It is best to use an electrolytic capacitor design for the LED driving power supply: Under normal use conditions, electrolytic capacitors are the shortest-lived components on the circuit board. Generally, the service life is about 5000 hours at the rated temperature. Probably only 2000 hours. At present, the entire social environment is pursuing the principle of reducing product manufacturing costs in principle. Therefore, when no relatively high price is obtained, there is little chance of selecting good materials. The life of the LED can reach 30,000-50,000 hours when the heat dissipation condition is better. In order to match the driving source with the life of the light source, a non-electrolytic capacitor for the driving source is a better choice. We have selected the design of non-electrolytic capacitor drive source in underground explosion-proof LED roadway lights, which works well.

 

 

 

10. Set current limit: When driving multiple LED dies, the drive source should pay attention to the series-parallel relationship between each channel. In addition to the constant current, set a current limit to prevent accidents.

 

 

 

                                                                                                                                                                            (Article source 21ic China Electronics Network)