Two‐Stage Gate Control to Minimize Inrush Current in Piezoelectric Transformer Based Inductorless ZVS Converter

ABSTRACT A method to control the inrush current of inductorless converters based on piezoelectric transformers (PTs) with high input capacitance is presented. With no magnetic core, inductorless PT based converters are of particular interest in medical equipment intended for use in the vicinity of high magnetic fields. The proposed method involves applying a reduced gate voltage to the converter MOSFETs during start‐up to increase their on‐resistance and decrease dv/dt at the switching point. A higher gate voltage is applied once steady state PT conditions are established to provide efficient operation. The design of the proposed gate drive solution and detailed LTSpice simulation results are described for a 3.6 W, 20 V DC/810 Vpk AC inverter. Due to the lack of commercial PTs with characteristics suitable for ZVS, the design of an emulated PT circuit is described to enable validation by testing. Experimental results successfully validate simulation results for the proposed start‐up circuit.