Effects of Internal Feedback and Gate-Drive Signal on the Turn-Off Loss of MOSFET ZVS

The effects of internal feedback through device parasitic capacitances and inductances associated with the gate-drive signal on the turn-off loss of a MOSFET operating as a zero-voltage switch in a class-D resonant inverter were studied. Expressions relating the parameters of Miller feedback and gate-drive circuit to Miller voltage were formulated. Impeding turn-off and return on of the conduction channel were found to be responsible for higher turn-off loss. Switching trajectories, energy transferred into the MOSFET in each switching cycle, as well as turn-off loss for different gate-drive signals, were calculated using data obtained from computer simulations. The results were compared with those calculated from experimental data. The voltage-dependent parasitic capacitances of the MOSFET were estimated from the experimental data and used for the calculation of channel current.