Patent ID: 6909617
Filing Date: 2005-06-21
Classification: H02M,Y02B

Abstract:
1. Apparatus for converting a first DC input voltage to a second DC output voltage, said apparatus comprising: a power transformer having primary and secondary windings, wherein an input alternating current is provided to said primary winding and an output alternating voltage is induced in said secondary winding; first and second pairs of electronic switches connected in a bridge circuit and coupled to said power transformer, wherein said first and second pairs of switches are conductive in counter phases to accommodate a high output voltage and are conductive in the same phase to accommodate a low output voltage or a no load condition; a first resonant inductor for recharging the switches' stray and internal capacitance during turn-on and turn-off, wherein said first resonant inductor is connected to an end of said primary winding and to said switches and is responsive to a current in said primary winding for storing energy when a high current is applied to said power transformer primary winding to allow for 0 voltage switching of the switches for a high output voltage load; and a second inductor and first and second capacitors connected to the DC input voltage and a center tap of said primary winding and responsive to voltage changes at said center tap, wherein said voltage changes produce current in said second inductor, and said second inductor stores energy when a low or 0 output voltage load is applied to said power transformer for recharging the switches' stray and internal capacitance during turn-on and turn-off of said switches to allow for 0 voltage switching of said switches for a low or 0 output voltage or no current condition.