Driving `high side´ power MOSFETs and IGBTs at high voltage using ASICs

The authors have presented an outline design of a gate drive for a `high side´ MOSFET switching at high voltage. Galvanic isolation and switching have been achieved using a pulse transformer with only two components on the secondary (gate) side. The additional complexity of the circuitry on the primary side has been integrated into an ASIC. The logic sequence was designed to provide integrity of the signal at the gate of the power device using refresh pulses synchronised to the power device switching. This technique also reflects a low impedance path to the gate-source capacitance minimising the effect of dv/dt transients. This approach was found to offer a cost effective solution for a brushless DC motor drive upto about 400 V, 10 A. Work is continuing to fully characterise the drive circuit in order to further reduce the number of components external to the ASIC. It is also intended to apply this technique to induction motor drives using IGBTs