PLL controller for achieving zero-voltage switching (ZVS) in inductorless half-bridge drive piezoelectric transformer resonant power supplies

Inductorless half-bridge, piezoelectric transformer (PT) resonant power supplies require careful control if zero voltage switching of the MOSFETs is to be achieved. Here we describe how a phase-locked loop may be used to achieve this by ensuring adequate deadtime exists between the two MOSFETs to allow the PT input voltage to fully charge to the DC link. Experimental results demonstrate the operation of the system.