Patent ID: 6628252
Filing Date: 2003-09-30
Classification: H02M,H04B,H05B,Y10S

Abstract:
An LED drive circuit for driving LED for illuminating a display of a portable electronic device, comprising:a battery power source; a booster circuit including first switching means for switching a power from said battery power source at a predetermined frequency, a first capacitor charged by the switched power, a second switching means, said second switching means switching complementarily to said first switching means, for boosting a voltage of said first capacitor to a boost voltage substantially n/m times the voltage of said first capacitor where n and m are integers equal to or larger than 2 and n>m, and a second capacitor charged by the boost voltage; at least one LED connected to an output terminal of said booster circuit as a load; and a constant current circuit connected to said LED, for driving said LED with a constant current, said constant current circuit including a MOS transistor and means for generating the constant current by controlling said MOS transistor by comparing a predetermined reference voltage with a voltage according to a drive current of the LED.