Patent ID: 8625311
Filing Date: 2014-01-07
Classification: H02M

Abstract:
1. A switching power supply apparatus comprising: a direct-current power-supply input unit to which a direct-current input voltage is input; a transformer defined by one magnetic component and including at least a first primary winding and a first secondary winding that are magnetically coupled; an inductor connected in series to the first primary winding; a first switch circuit including a parallel circuit including a first switching element, a first capacitor, and a first diode; a second switch circuit including a parallel circuit including a second switching element, a second capacitor, and a second diode; a third capacitor; a first series circuit connected to both end portions of the direct-current power-supply input unit and in which the first primary winding and the first switch circuit are connected in series; and a second series circuit connected to both end portions of the first switch circuit or both end portions of the first primary winding and in which the second switch circuit and the third capacitor are connected in series; wherein the first switch circuit and the second switch circuit are arranged to operate so that the first switch circuit and the second switch circuit complementarily repeat turning on and turning off with a time period in between, for which both of the first switch circuit and the second switch circuit are turned off; and the switching power supply apparatus further includes: a gate signal of the first switch circuit and a gate signal of the second switch circuit are generated based on outputs of the first comparator and the second comparator; the first threshold value is set to an electrical potential equal or substantially equal to the low level of the monitor signal; the switching control circuit is arranged to set a dead time in which both of the first switching element and the second switching element are turned off for a time period that is suitable for a load added to the output voltage; and the switching control circuit is arranged to control an on-time of the first and second switching elements so as to maintain a constant switching period in order to obtain a desired output voltage.