Optimal operation of coreless PCB transformer-isolated gate drive circuits with wide switching frequency range

Abstract

Gate drive circuits for power MOSFETs and IGBTs often require electrical isolation. Coreless printed-circuit-board (PCB) transformers have been shown to have desirable characteristics from a few hundreds of Hertz to a few Mega-Hertz and can be used for both power and signal transfer at low-power level. At low operating frequency, the magnetizing inductance has such low impedance that the driving power requirement could become excessive. This paper describes the use of coreless PCB transformer for isolated gate drive circuits over a wide frequency range. Based on a resonance concept, the optimal-operating condition that minimizes the power consumption of the gate drive circuits is developed and verified with experiments. Coreless PCB transformers do not require the manual winding procedure and thus simplifies the manufacturing process of transformer isolated gate drive circuits and low-power converters. Their sizes can be much smaller than those of typical core-based pulse transformers. The electrical isolation of PCB (typically from 15 kV to 40 kV) is much higher than that of an optocoupler (typically 2.5 kV).