Comparing piezoelectric and coreless electromagnetic transformer approaches in IGBT driver

Abstract

Gate drive circuits for power MOSFET's and IGBT's often require electrical insulation. Different methods of electrical insulation can be used: bootstrap circuits, transformers and optic couplers. It has been proved that Piezoelectric transformer (PT) exhibit suitable characteristics, good integration capability and can be used for both power and signal transfer in low power applications. However, coreless planar electromagnetic transformer (CT) technology is an alternative solution that can also give satisfactory results. This paper compares the performances and the capabilities of integration of these two kinds of transformers (i.e. PT vs. CT). The study and comparisons are carried out in a two-gate driver, functioning in a half-bridge inverter. The two devices have the same structure, similar electric characteristics (operating at resonance frequency in both cases), identical electric values and the dimensions of the two transformers are quite the same. Additionally, some EMI aspects regarding the use of these transformers will be considered.