Realisation of the zero-voltage switching condition for asymmetrical half-bridge DC/DC forward converters

An analytical analysis for the zero-voltage switching (ZVS) asymmetrical half-bridge (AHB) PWM DC/DC forward converter is presented to gain insight sufficient to understand as well as design the system. It is concluded that the ZVS condition of the converter can definitely not be calculated by simply regarding the stored energy in leakage inductance. The derived closed-form relationships can also be used to guarantee required minimum dead time and boundary conditions. As a result, the converter design can be optimised for ZVS in all desired operation ranges. An off-line 250 W prototype is constructed for verifying the effectiveness of the proposed analytical derivations.