Patent ID: 7173404

Claim:
An auto-switching converter with PWM and PFM selection, connected to a load through a power switch unit for supplying DC power to the load by controlling a switching action of the power switch unit, comprising: a starter outputting a starting-enabling signal; an auto PWM/PFM controller connected to the starter for receiving the starting-enabling signal and outputting a selection signal; a PWM controller connected to the auto PWM/PFM controller, the power switch unit and the load for receiving a feedback voltage signal, a load current signal and the selection signal, outputting an error signal to the auto PWM/PFM controller, and outputting a PWM control signal to the power switch unit for controlling the switching action of the power switch unit; and a PFM controller connected to the auto PWM/PFM controller, the power switch unit and the load for receiving the feedback voltage signal, the load current signal and the selection signal, outputting a current comparison signal to the auto PWM/PFM controller, and outputting a PFM control signal to the power switch unit for controlling the switching action of the power switch unit; wherein, the auto PWM/PFM controller comprises: a reference voltage generator outputting a reference voltage signal; a PWM comparator connected to the reference voltage generator, the starter and the PWM controller for receiving the reference voltage signal, the starting-enabling signal and the error signal, and outputting a PWM comparison signal; a PFM comparator connected to the reference voltage generator, the starter and the PWM controller for receiving the reference voltage signal, the starting-enabling signal and the error signal, and outputting a PFM comparison signal; a first flip-flop connected to the PWM comparator and the PFM comparator for outputting a reset signal; an AND circuit outputting an AND signal; and a second flip-flop connected to the first flip-flop and the AND circuit for receiving the reset signal and the AND signal, and outputting the selection signal.