ZVS for PT Backlight Inverter Utilizing High-Order Current Harmonic

A zero-voltage-switching (ZVS) method utilizing high-order current harmonics for piezoelectric transformer (PT) backlight inverter is presented. In order to enhance the efficiency of PT backlight inverter, a large inductor is usually connected in series with PT for ZVS and filtering. Utilizing high-order current harmonics for ZVS can greatly reduce the required series inductance. The ZVS condition of the proposed approach is analyzed, and related experimental waveforms are shown. This method also minimizes the delay introduced into the inverter control loop, and makes the designs between ZVS and control loop independent. Measured power conversion efficiency of the tested PT backlight inverter is 85%.