Wideband ZVS half-bridge circuit for piezoelectric transformers with small inductance

A wideband zero-voltage-switching (ZVS) half-bridge circuit for piezoelectric transformers is introduced. The proposed circuit topology is the extension of the inductor-less half-bridge driver for the piezoelectric transformers. Two auxiliary shunt circuits are connected to the input terminal PT to ensure the ZVS condition in a wide bandwidth. Each auxiliary shunt circuit includes a diode, a switch and an inductor. The auxiliary inductor exhibits a small inductance and is not in the path of the major power flow, thus it can be implemented by the parasitic inductance of the connection wires or by PCB tracks. A 80kHz piezoelectric transformer was tested by the proposed circuit from 20 to 160 kHz to verify the ZVS condition.