Abstract
The white LEDs will become the lighting source of new generation, and gradually substitute for traditional ones, such as incandescent lamp and fluorescent lamp, based on the character of highly effective, energy conservation, environmental protection, long life, easy to maintain and so on. It is necessary to design special driving control chip to drive white LEDs, for the brightness uniformity the portable application needs, and the white LEDs' characteristic of high forward voltage drop, high divergence of electricity parameter and easy be effected by temperature.
Based on LM3402 chip,this paper designs a circuit for illumination to drive high power white LEDs(more than 1W).The circuit uses inductance type DC/DC buck convertor to change voltage, and uses pulse width modulation(PWM)technique, for the purpose of wide input voltage, constant output current, in order to drive LEDs effectively, and also can realize the function of LED dimming.
Keywords:LED switch power supply DC-DC converter PWM LM3402