Critical design criterion for inductorless H-bridge driven piezoelectric-transformer-based power supplies

A methodology for predicting the ability of a piezoelectric transformer for achieving zero-voltage switching (ZVS) is presented. A describing function method is employed to obtain the PT equivalent circuit model operating under ZVS operation. This methodology is encapsulated within a critical criterion which, if fulfilled, guarantees efficient ZVS operation over a wide load range. The model provides a quantitative measure of a PT’s ability to achieve ZVS using a H-bridge inductorless configuration. With the capacitance ratio profile provided by the analytical model, the limitations of the inductorless H-bridge driven PT-based inverters are indicated and guidelines for designing both PT and inverter control circuit are demonstrated.