Switched-mode power supply for providing a stable output voltage

摘要

The present invention is a switched-mode power supply for providing a stable output voltage. An excitation winding, a vice-output winding and an active snubber circuit are connected to a primary side of a flyback-based transformer. A main-output winding is connected to a secondary side of the transformer. A primary-side PWM controller and a secondary-side PWM controller are respectively connected to the primary side and the secondary side of the transformer. By a time-shared-energy-transfer method, the main-output winding and the vice-output winding are controlled to sequentially extract demand electricity from the transformer during a same switching cycle. Additionally, by a time-shared-energy transformation, the output voltage on the secondary side of the transformer is stabilized to be provided between a stable minimal voltage and a preset higher voltage for satisfying a heavy-loading status and a light-loading status.

主权项

1. A switched-mode power supply for providing a stable output voltage, the switched-mode power supply comprising:
a transformer having:
a primary side having an excitation winding and a vice-output winding of Na turns, wherein a first terminal of the excitation winding is connected to an input power and an input capacitor, the vice-output winding is connected to a primary-side-phase-compensation circuit via a vice-output diode, and a cathode of the vice-output diode is connected to a power-saving capacitor that is grounded; anda secondary side having a main-output winding of Ns turns;a ratio of turns of the transformer meeting(Vs×NaNs) 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
the second diode, the energy-storing inductor and the third diode are sequentially connected in series and connected to the input power;the snubber capacitor has a first terminal connected to a node between the third diode and the energy-storing inductor, and a second terminal connected to a node between the primary-side switch and the excitation winding via the first diode;the snubber switch has a first terminal connected to a node between the snubber capacitor and the first diode, and a second terminal connected to the ground; 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.