Patent ID: 9548662
Date: 2017-01-17
CPC Classifications: H02M

Claim:
1. A switching power-supply circuit comprising: a transformer including a primary winding, a first secondary winding, and a second secondary winding; a first switching element connected in series to the primary winding; a first rectifying/smoothing circuit arranged to generate a first output voltage by rectifying and smoothing an output of the first secondary winding; a second rectifying/smoothing circuit arranged to generate a second output voltage by rectifying and smoothing an output of the second secondary winding; a first feedback circuit arranged to generate a feedback signal according to the first output voltage; and a switching control circuit arranged to control the first switching element based on the feedback signal and to stabilize the first output voltage; wherein a rectifier circuit in the second rectifying/smoothing circuit includes a rectifier switch element and a drive control circuit arranged to determine when an input voltage is greater than the second output voltage and the second output voltage is less than a predetermined voltage by comparing the second output voltage to a reference voltage, and cause the rectifier element to be conductively connected when the input voltage is greater than the second output voltage and the second output voltage is less than the predetermined voltage; the rectifier switch element operates by using a winding voltage occurring in one of the primary winding, the first secondary winding, and the second secondary winding of the transformer; and the rectifier circuit in the second rectifying/smoothing circuit is arranged to stabilize the second output voltage so as to achieve and maintain accuracy of the second output voltage, by controlling a number of pulses per unit time in a pulse current flowing through the rectifier circuit itself.