Patent ID: 7388763
Filing Date: 2008-06-17
Classification: H02M

Abstract:
1. A switching power supply comprising: a switching element being connected to one end of a primary winding of a transformer, an input DC voltage being supplied to a secondary winding of the transformer via the primary winding; an output voltage detection circuit detecting a voltage obtained by rectifying and smoothing a voltage of the secondary winding of the transformer, and generating an error signal based on the detected voltage; a regulator generating a predetermined voltage; a capacitor being coupled to an output of the regulator and configured to stabilize an output voltage of the regulator; a photocoupler being connected to the capacitor in parallel, a feedback current signal corresponding to the error signal passing through the photocoupler; a feedback current detection circuit outputting electric current corresponding to the feedback current signal that passes through the photocoupler; a feedback voltage generation circuit generating a feedback voltage according to the current outputted from the feedback current detection circuit when the switching element is OFF, and holding the generated feedback voltage when the switching element is ON; and a control circuit controlling ON/OFF duty of the switching element according to the feedback voltage outputted from the feedback voltage generation circuit.