Quadrilateral Current Mode Paralleling of Power MOSFETs for Zero-Voltage Switching

This article proposes a generic zero-voltage switching (ZVS) scheme for parallel power MOSFETs. Uncoupled or inversely coupled differential-mode commutation inductors are added to the midpoints (ac terminals) of parallel MOSFET half-bridges, and a time-delay-based control scheme is applied, generating a circulating current flowing through these commutation inductors. Thus, the inductor currents are reshaped as quadrilaterals, which enable all the parallel transistors to achieve ZVS. The mode of operation of the proposed paralleling technique is entitled quadrilateral current mode (QCM) due to the quadrilateral-shaped commutation inductor currents. The operating principle of the QCM-paralleling technique is detailed mathematically, yielding accurate closed-form analytical expressions for modulation parameters. Finally, simulations and experimental results of a QCM-enabled synchronous buck dc-dc converter are presented to validate the theoretical considerations.