A Transient Approach for Input Capacitance Characterization of Power Devices

A novel characterization method for the input capacitance of power MOSFETs is presented. As opposed to the conventional small signal method in which impedance of the capacitance in interest is selectively measured using small signal input, this method captures the charge transfer that goes in and out the gate terminal of the power MOSFET to find input capacitance. Through the experiments, the extracted values of the small signal and the switching capacitance are shown to be different, causing timing difference in the waveforms of circuit simulations. Comparison among simulations and measurement on a buck converter further show that the models using the switching capacitance better reproduce the measurement results.