A method for dimming operation of a lamp includes the steps of generating a trapezoidal wave signal in response to an input square wave low frequency dimming gating signal, and generating a driving signal that has a low frequency when the trapezoidal wave signal has a low level, that has a high frequency when the trapezoidal wave signal has a high level, that shifts gradually from the low frequency to the high frequency when the trapezoidal wave signal goes from the low level to the high level, and that shifts gradually from the high frequency to the low frequency when the trapezoidal wave signal goes from the high level to the low level. A module that performs the method is also disclosed.