Dynamic operating frequency control of a buck power converter having a variable voltage output

A switch controller for a power converter having a variable output voltage range comprising:

• a pulse width modulator having an output producing a pulsed signal for driving a power converter switch;
• a mode selector having an output indicative of an operating on-time state of the power converter connected to a multiplier;
• a period selector having an output indicative of a cycle time for the pulsed signal connected to the multiplier and to an input of the pulse width modulator;
• the multiplier having an output indicative of a switch on-time of the cycle time connected to another input of the pulse width modulator;
• a comparator having an output indicative of the operating on-time state relative to a minimum operating on-time and connected to an input of the period selector;
• and
• wherein the period selector outputs a nominal cycle time to the pulse width modulator when the operating on-time state is greater than the minimum operating on-time and wherein the period selector outputs an updated cycle time greater than the nominal cycle time when the operating on-time state is less than the minimum operating on-time such that the pulse width modulator outputs a pulsed signal with the updated cycle time and a duty cycle equal to a duty cycle of an immediately preceding pulsed signal.