Power conversion circuit having improved zero voltage switching

Abstract

A highly efficient and simple power conversion circuit ( ) having zero voltage switching (ZVS) includes a novel switch timing technique, such that the need for an leakage inductor connected in series with the primary circuit of the converter and rectifier diodes is eliminated. A switch timing circuit ( ) located in an output side circuit ( ) enables the use of the natural stored magnetic energy in the output side circuit ( ) to drive the critical switching transitions to accomplish soft switching for all of the switches ( ) in a full bridge forward converter ( ) for all transitions. This power conversion circuit ( ) includes a full bridge circuit ( ) having plurality of switching devices ( ) that intermittently couple the primary winding ( ) to the input of the power converter ( ). A transformer ( ) couples to receive power from the full bridge circuit ( ) into its primary winding ( ). The output side circuit ( ) includes the switching circuit ( ) coupled to provide stored magnetic energy to drive the switching transitions of the switching devices ( ) in the full bridge circuit ( ). The switching circuit ( ) closes at a predetermined time delay after the switching transitions in the full bridge circuit ( ) to accomplish zero voltage switching for the plurality of switches in the full bridge circuit ( ). A converter controller provides control signals to the full bridge and the switching circuits ( ).