High power density asymmetrical full-bridge soft-switching inverter

This paper presents a Zero-Voltage-Switching (ZVS) technique eliminating the switching loss on a proposed single phase bi-directional full-bridge Buck inverter in which asymmetrical filter topology and control scheme are for each arm. Here Metal-Oxide-Field-Effect-Transistor(MOSFET) is chosen as the switching device, an L₁-C₁ filter is connected across the full-bridge, an L₂ filter is connected in series to load or grid. While the arm connecting with the C₁ is controlled by the polarity of 50Hz sinusoid reference command and the arm connecting with the L₁ is controlled by a Pulse-Width-Modulation(PWM) signal modulated by sinusoid, the L₁-C₁ then operates as an output filter of Buck, and the succeeding L₂ filter further attenuates ripple current flowing to load or grid. The ZVS technique sets the L₁ inductance such low that its current flows bi-directionally within a switching period, then the bidirectional current with sufficiently high peaks in turn charge and discharge the output capacitance C_oss of MOSFETs of the switching arm within floating time, defined as the duration when both MOSFETs of an arm are off, to let the MOSFETs D-S channels be turned on or off at the state that C_oss are fully discharged to zero voltage, so ZVS of MOSFET is achieved. Under the ZVS operation without frequency proportional switching loss, the switching frequency is possible to be raised to high to compact the sizes of passive components and heat sink of the inverter for achieving high power density. Simulation and experiment have been carried out to verify the ZVS operation.