Patent ID: 7859860
Filing Date: 2010-12-28
Classification: H02M,Y02B

Abstract:
1. A switching power source device for generating a predetermined output voltage and supplying power to a load, comprising: a series resonant circuit including a current resonant inductor and a current resonant capacitor, an input direct voltage being applied to said series resonant circuit; a plurality of main switches for switching a current path of the series resonant circuit by alternately turning on and off; a transformer for inducing a secondary current from the series resonant circuit to a secondary side by on-off controlling the main switches on a primary side; a plurality of synchronous rectification switch elements for rectifying the secondary current of the transformer, each of the synchronous rectification switch elements having internal diodes connected in parallel and being turned on and off in response to the plurality of main switches; a maximum on width control circuit for ordering a start of a maximum on width to the synchronous rectification switch element in synchronization with a timing of turning on the main switches, and, after a predetermined time, ordering a completion of the maximum on width; and a synchronous control circuit for controlling an on period of the synchronous rectification switch element so as to turn on the synchronous rectification switch element in synchronization with a timing in which the maximum on width control circuit orders the start of the maximum on width, or a timing of a conduction of the internal diode detected as an inter-terminal voltage signal of the synchronous rectification switch element, whichever is later, and turn off the synchronous rectification switch element in synchronization with a timing in which the main switches are turned off, or a timing in which the maximum on width control circuit orders the completion of the maximum on width, whichever is earlier.