Patent ID: 9197136
Filing Date: 2015-11-24
Classification: H02M,Y02B

Abstract:
1. A switched-mode power supply for providing a stable output voltage, the switched-mode power supply comprising: a transformer having: wherein Vs is a voltage of the main-output winding, and Va is a voltage of the vice-output winding; a primary-side switch connected between the excitation winding of the transformer and a ground in series; an active snubber circuit having a first diode, a second diode, a third diode, a snubber capacitor, an energy-storing inductor and a snubber switch, wherein a primary-side pulse width modulation (PWM) controller connected to the snubber switch and the primary-side switch to respectively provide a first driving signal and a second driving signal to the snubber switch and the primary-side switch; a secondary-side switch connected between the main-output winding and an output terminal; a secondary-side-phase-compensation circuit receiving an output voltage from the output terminal and a setting command from outside, and comparing the output voltage with the setting command; a secondary-side PWM controller receiving a comparison result from the secondary-side-phase-compensation circuit and providing a secondary-side-switch-driving signal to control the secondary-side switch; and a synchronization circuit connected to the main-output winding to detect a voltage variation from the main-output winding and providing a synchronization signal to the secondary-side PWM controller according to the voltage variation.