LED because of the numerous advantages of environmental protection, long life, high photoelectric efficiency and rapidly developed in recent years application in various fields, LED driver power became the attention hot spot, in theory, the service life of the LED in the 100000 hours, but in the process of practical application, due to improper design of drive power supply and drive mode selection, the LED is easily damaged.
Design of LED drive power supply, it is necessary to know the LED current, voltage characteristic, because the manufacturer of LED and LED specifications different, there are differences between the current and voltage characteristic. Now in white LED typical specifications, for example, according to the current, voltage of the LED change law of general application forward voltage is about 3.0 3.6 V, the typical value voltage of 3.3 V, current to 20 ma, when added to the LED on both ends of the forward voltage is greater than 3.6 V, the increase of the forward voltage is very small, LED the forward current growth is likely to be exponentially, the LED luminous body temperature rise too fast, so as to accelerate the LED light attenuation, shortening the service life of the LED, serious when even burning LED. According to the voltage and current of the LED change characteristics, design of the drive power put forward strict requirements.
Many current manufacturers of LED lighting products, such as guardrail, lamp cup, projection lamp), the resistance and capacitance step-down, then add a zener diode voltage stability, supply power to the LED such flaws greatly drive LED the way, the first is low efficiency, on the step-down resistance consume a large amount of electricity, electricity consumed may even more than the LED, and cannot provide high current driving, because the current, the greater the consumption on the step-down resistance the greater the power, so a lot of products LED can’t used in parallel, series method are adopted to decrease the current.