Patent ID: 7535276

Claim:
A PWM controller comprising: a first input configured to form a first signal; a second input configured to receive a second signal that varies responsively to a maximum peak value of a bulk voltage; an oscillator circuit having a first portion that forms an on-time of a clock signal formed by the oscillator circuit and having a second portion that forms an off-time of the clock signal; a first control circuit of the oscillator circuit configured to control the first portion and the second portion to form an operating frequency of the clock signal, the first control circuit configured to set a center frequency of the operating frequency responsively to the first signal formed on the first input and configured to vary the operating frequency around the center frequency a maximum and minimum amount that is a percent of the center frequency; and a second control circuit of the oscillator circuit configured to vary a maximum duty cycle of the clock signal responsively to the second signal from the second input.