Patent ID: 8437153

Claim:
A series resonant converter capable of reducing peak voltage generated at power switches and peak current generated on secondary side when being turned on from off immediately, the series resonant converter comprising: a transformer having a primary side provided with a primary winding and a secondary side provided with two secondary windings; two primary-side power switches connected to the primary side and comprising a first power switch and a second power switch, wherein the first power switch and the second power switch are connected in series; an input voltage filter capacitor connected across a DC input voltage and connected in parallel to the series-connected first and second power switches; a resonant control chip having two control pins connected respectively to a gate of the first power switch and a gate of the second power switch; a resonant capacitor having an anode connected to an end of the primary winding and a cathode connected to a source of the second power switch, wherein high voltage accumulated at the resonant capacitor is discharged to zero instantly while the series resonant converter is turned off; a resonant inductor having an end connected to another end of the primary winding and another end connected to a line between the first power switch and the second power switch; at least a bypass resistor connected in parallel to the resonant capacitor and connected to a ground end, wherein the bypass resistor is used to rapidly release the high voltage accumulated at the resonant capacitor to the ground end while the series resonant converter is turned off; an output voltage filter capacitor having an end connected to a line between the two secondary windings; and two secondary rectifying elements each having an end connected to an end of each of the two secondary windings and another end connected to another end of the output voltage filter capacitor, so as for the output voltage filter capacitor to provide a DC output voltage.