Patent ID: 7525819
Filing Date: 2009-04-28
Classification: H02M,Y10S

Abstract:
1. A switching mode power supply including a primary coil of a transformer and a main switch, which generates an output voltage by switching the main switch, the switching mode power supply comprising: a bias voltage generator including an auxiliary coil of the transformer and a capacitor electrically coupled to a first terminal and a second terminal of the auxiliary coil of the transformer; an initial bias voltage generator, which charges the capacitor from the second terminal of the primary coil of the transformer during a start-up of the switching mode power supply, wherein a first terminal of the primary coil of the transformer is electrically coupled to a rectified DC voltage signal and a second terminal of the primary coil is electrically coupled to the main switch; and a pulse width modulator controller, which receives a first voltage of the capacitor through a first terminal and starts switching the main switch, wherein the pulse width modulator controller comprises: a time delay circuit, coupled to the initial bias voltage generator, which stops the charging of the capacitor at a second time, which is a delay time after a first time at which the first voltage is essentially equal to a reference voltage, and starts switching the main switch.