Patent ID: 8582326
Filing Date: 2013-11-12
Classification: H02M,Y02B

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 to one another; 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 so as to operate so that the first switch circuit and the second switch circuit complementarily repeat turn on and turn off with a time period in between, in which both of the first switch circuit and the second switch circuit are turned off; and the switching power supply apparatus includes a power converter circuit arranged so that an output voltage is output to a secondary side through a first rectification smoothing circuit arranged to rectify and smooth an alternating-current voltage output from the first secondary winding; the switching power supply apparatus further comprising: a first monitor signal generator arranged to detect a change of a voltage or current based on a change of an equivalent circuit of the power converter circuit, which occurs due to the turn off of one of the first and second switch circuits in an on-state, and to generate a monitor signal; and a digital control circuit arranged to control the first switching element and the second switching element; wherein the digital control circuit sets on-times of the first switching element and the second switching element with a timing based on a clock signal, using arithmetic processing; start timings of the on-times are determined with a timing based on the clock signal, at which the monitor signal is input as a trigger, and based on the trigger, a control signal provided to turn on one of the first switching element and the second switching element is generated; a stop timing of the on-time is determined with a timing based on the clock signal in accordance with the on-time set by the arithmetic processing, and based on the stop timing, a control signal provided to turn off the first switching element or the second switching element is generated; the first switch circuit or the second switch circuit is driven by a zero voltage switching operation in which, after voltages of both end portions of the first switch circuit or the second switch circuit have been decreased to 0 V or approximately 0 V, the one of the first and second switching elements is turned on; and the digital control circuit generates a first switching control signal or a second switching control signal while maintaining a constant switching period.