Patent ID: 8218340

Claim:
A synchronous rectification type switching power supply apparatus, comprising: a voltage converting transformer; a first switching element for making a current flow through a primary side coil of the transformer; a first control circuit for performing on-off control of the first switching element; a second switching element for performing rectification of a secondary side coil of the transformer; and a second control circuit for performing on-off control of the second switching element, wherein the second control circuit is adapted to ensure a minimum on-period of a signal for turning on and off the second switching element, wherein the first control circuit includes a PWM pulse generating circuit for generating a PWM control pulse to perform the on-off control of the first switching element based on a feedback voltage from a secondary side circuit of the transformer; a burst mode control circuit for turning off a control signal of the first switching element based on the feedback voltage at a time of a light load; and a pulse width ensuring circuit for ensuring a pulse width of the control signal for performing the on-off control of the first switching element so as not to become equal to or less than an original width of the PWM pulse when entering a burst mode and when exiting the burst mode.