Design of auxiliary power supply for high voltage power electronics devices

High voltage and wide input range auxiliary power supply (APS) is widely used in high voltage power electronics devices. Due to a wide range of high input voltage, low power and significant parasitic effects, high voltage converter systems are more challenging to design. This paper proposes a solution to the design of APS which is based on flyback topology with a specially designed transformer. Because of the high input voltage, design of the transformer is a challenge. On the one hand, a proper transformer ratio is designed to decrease the requirement of the MOSFET. On the other hand, as the consideration of creepage effect in the windings of the transformer, a method of winding high input voltage and small volume transformer is proposed. In addition, the leakage inductance in the transformer is large, which will cause voltage spikes on the MOSFET and oscillations between the leakage inductance and the intrinsic capacitance of the MOSFET. The resistor in the RCD snubber should be small enough to absorb most of the energy stored in the leakage inductance. Simulation and experiment results are given to verify the correctness of the design.