초록 ▼

The present invention discloses a forward-flyback converter with active-clamp circuit. The secondary side of the proposed converter is of center-tapped configuration to integrate a forward circuit and a flyback circuit. The flyback sub-circuit operating continuous conduction mode is employed to dire

The present invention discloses a forward-flyback converter with active-clamp circuit. The secondary side of the proposed converter is of center-tapped configuration to integrate a forward circuit and a flyback circuit. The flyback sub-circuit operating continuous conduction mode is employed to directly transfer the reset energy of the transformer to the output load. The forward sub-circuit operating discontinuous conduction mode can correspondingly adjust the duty ratio with the output load change. Under the heavy load condition, the mechanism of active-clamp flyback sub-circuit can provide sufficient resonant current to facilitate the parasitic capacitance of the switches to be discharged to zero. Under the light load condition, the time interval in which the resonant current turns from negative into positive is prolonged to ensure zero voltage switching function. Meanwhile, the flyback sub-circuit wherein the rectifier diode is reverse biased is inactive in order to further reduce the power losses.

대표청구항 ▼

What is claimed is: 1. A forward-flyback DC/DC converter, comprising:an isolated transformer having a primary winding, a first secondary winding and a second secondary winding, wherein the two secondary windings are connected in series to form a center-tapped configuration and their common node is g

What is claimed is: 1. A forward-flyback DC/DC converter, comprising:an isolated transformer having a primary winding, a first secondary winding and a second secondary winding, wherein the two secondary windings are connected in series to form a center-tapped configuration and their common node is grounded;a main switch;an output capacitor having a positive terminal and a negative terminal;an output load;a forward sub-circuit having an output and comprising:an output inductor operating in discontinuous conduction mode;the first secondary winding transmitting input energy to the output inductor, the output capacitor and the output load via the transformer when the main switch is turned on;a first diode forwardly transmitting a secondary side current to the output when the main switch is turned on; anda second diode providing flywheeling function to transmit energy stored in the output inductor to the output when the main switch is turned off;a flyback sub-circuit operating in continuous conduction mode and comprising:the second secondary winding providing magnetic reset of the transformer when the main switch is turned off; anda third diode having an anode connected to the second secondary winding in series and a cathode connected to the positive terminal of the output capacitor to directly transmit magnetic reset energy of the transformer to the output; andan active-clamp circuit clamping voltage spike of the main switch and engaging in magnetic reset of the transformer when the main switch is turned off.