Due to many advantages such as no toxic substances, environmental protection, long life and high photoelectric efficiency, LEDs have been rapidly developed in various industries in recent years. Theoretically, the service life of LEDs is about 100,000 hours, but in actual applications, some LED lighting factory Lamp designers have insufficient knowledge of LED drive power or improper selection, resulting in a greatly shortened LED lamp product life.
Due to the particularity of LED processing and manufacturing, there are large individual differences in the current and voltage characteristics of LEDs produced by different manufacturers or even the same manufacturer in the same batch of products. Now take the typical specifications of high-power 1W white light LED as an example, and give a brief description according to the change law of LED current and voltage. Generally, the forward voltage of 1W white light application is about 3.0-3.6V. In order to ensure the life of 1W LED, general LED manufacturers recommend The lighting factory uses a current of 350mA to drive. When the forward current passing through the two ends of the LED reaches 350mA, a small increase in the forward voltage across the LED will cause the forward current of the LED to rise sharply and cause the temperature of the LED to increase. Straight-line rise, thereby accelerating the LED light decay, shortening the life of the LED, and even burning the LED in severe cases. Due to the particularity of the voltage and current changes of the LED, strict requirements are placed on the power supply for driving the LED.
LED drive power is the key to LED lamps, it is like a person’s heart, to manufacture high-quality LED lamps for lighting must give up the constant voltage drive LED.
At present, LED lamp products produced by many manufacturers (such as guardrails, lamp cups, projection lamps, garden lamps, etc.) adopt resistance and capacitance step-down, and then add a Zener diode to stabilize the voltage and supply power to the LED. This is the way to drive the LED. There are great defects, first of all, the efficiency is low, and a large amount of power is consumed on the drop-down resistor, which may even exceed the power consumed by the LED, and it cannot provide high-current drive, because the larger the current, the more power consumed on the drop-down resistor. The bigger the LED is, the more difficult it is to ensure that the current through the LED does not exceed its normal operating requirements. When designing products, the voltage at both ends of the LED will be reduced for power supply and drive, which is at the cost of sacrificing the brightness of the LED. The brightness of the LED is not stable when the LED is driven by the resistance and capacitance step-down method. When the power supply voltage is low, the brightness of the LED becomes darker, and when the power supply voltage is high, the brightness of the LED becomes brighter. Of course, the biggest advantage of driving LEDs with resistance and capacitance step-down is low cost.
