Low Capacitive Design of Planar Transformers in High Voltage Isolated Power Supply for Gate Drivers

Abstract:
High voltage (HV) isolation in auxiliary power supplies (APS) has been most commonly achieved with the help of transformers. It has been mandated by standards to have sufficient clearance and creepage for such HV designs, which often increases the APS volume. For low power HV applications, for example, in isolated gate driver units, replacing toroidal cores with planar transformers can help reduce both the volume and material costs of the APS. However, with compactness the resulting high parasitic capacitance from the transformer primary to secondary can cause high common mode noise, and therefore should be mitigated. In this work, such designs meant for low power transformers are investigated, evaluated and compared.