MULTI-OUTPUT SWITCHING POWER SUPPLY DEVICE

摘要

A multi-output switching power supply device includes: a first switching element Q1 and a second switching element Q2 connected in series; a first series resonance circuit connected to Q1 or Q2 in parallel and having a first current resonance capacitor and a primary winding of the transformer connected in series; a first rectifying smoothing circuit for rectifying/smoothing voltage generated in a secondary winding of the transformer; a second series resonance circuit connected to the secondary winding in parallel and having a second current resonance capacitor and a second resonance reactor connected in series; a second rectifying smoothing circuit for rectifying/smoothing the voltage of the second series resonance circuit; and a control circuit for deciding the ON period of Q1 according to the voltage obtained at one of the first and the second rectifying smoothing circuit and deciding the ON period of Q2 according to the voltage obtained at other of the first and the second rectifying smoothing circuit, thereby alternately turning ON/OFF Q1 and Q2.