Patent ID: 7012383

Claim:
A digital-dimming control method for dimming operation of a lamp, comprising the steps of: (A) generating a trapezoidal wave voltage signal in response to an input square wave low frequency dimming gating signal; (B) generating a trapezoidal wave current signal that corresponds to the trapezoidal wave voltage signal and that varies between first and second current levels; and (C) generating a driving signal that controls activation and deactivation of the lamp, the driving signal having a first frequency when the trapezoidal wave current signal has the first current level and having a second frequency when the trapezoidal wave current signal has the second current level, the driving signal shifting gradually from the first frequency to the second frequency when the trapezoidal wave current signal goes from the first current level to the second current level and shifting gradually from the second frequency to the first frequency when the trapezoidal wave current signal goes from the second current level to the first current level.