Patent ID: 7474086

Claim:
A frequency-on-the-fly control circuit for a DC/DC PWM converter having a power stage to be operated with a switching frequency to produce an output voltage and an output current, the control circuit comprising: an error amplifier for monitoring the output voltage to produce a first signal; a frequency-determining circuit for providing a second signal whose frequency changes with the output current, the frequency-determining circuit receiving a current signal indicative of the output current and generating the second signal responsive thereto; a ramp generator in response to the second signal for generating a first ramp signal whose frequency changes with the output current; a combiner for shifting the first ramp signal by a current-sensing signal representative of a channel current produced by the power stage, to produce a second ramp signal; and a comparator for comparing the first signal with the second ramp signal to produce a modulation signal whose frequency changes with the output current to operate the power stage with the switching frequency; wherein the switching frequency decreases when the output current increases and increases when the output current decreases.