Patent ID: 8077488
Filing Date: 2011-12-13
Classification: H02M,Y02B

Abstract:
1. A switching-type power-supply unit comprising: a transformer comprising a primary winding, a secondary winding and a control winding; a switch which switches supply of a primary current from a dotted terminal to a non-dotted terminal through the primary winding; a rectifying circuit which allows a secondary current to flow from a dotted terminal to a non-dotted terminal through the secondary winding; a monitoring signal generation circuit comprising a monitoring diode and a resistor, the monitoring diode disposed between GND and a dotted terminal of the control winding, the resistor disposed between GND and a non-dotted terminal of the control winding, the monitoring signal generation circuit generating a monitoring signal at a terminal of the diode connected to the dotted terminal of the control winding; and a control unit comprising a zero-point detector and a controller, the zero-point detector monitoring the monitoring signal and supplying a detection signal to the controller, the controller determining on-timing of the switch based on the detection signal supplied from the zero-point detector.