Analysis of the ultra-fast switching dynamics in a hybrid MOSFET/Driver

The turn-on dynamics of a power MOSFET during ultra-fast, ~ns, switching are discussed in this paper. The testing was performed using a custom hybrid MOSFET/driver module, which was fabricated by directly assembling die-form components, power MOSFET and drivers, on a printed circuit board. By using die-form components, the hybrid approach substantially reduces parasitic inductance, which facilitates ultra-fast switching. The measured turn on time of the hybrid module with a resistive load is 1.2 ns with an applied voltage of 1000 V and drain current of 33 A. Detailed analysis of the switching waveforms reveals that switching behavior must be interpreted differently in the ultra-fast regime. For example, the gate threshold voltage to turn on the device is observed to increase as the switching time decreases. Further analysis and simulation of MOSFET switching behavior shows that the minimum turn on time scales with the product of the drain-source on resistance and drain-source capacitance, R_DS(on)C_OSS. This information will be useful in power MOSFET selection and gate driver design for ultra-fast switching applications.