Common mode noise cancelation in power converters

Abstract

This disclosure describes a circuit, a method, and a system to mitigate common mode noise in a power converter. The converter may include a transformer that isolates input and output terminals with primary and secondary windings. The transformer may further include an auxiliary winding coupled in anti-parallel with a secondary winding. The auxiliary winding may inject a common mode current through a compensation capacitor and a Y-capacitor to cancel a common mode current induced at the secondary side to the primary side. The converter may include a coupler circuit that provides a varying impedance at different frequencies to facilitate the current injection and allocate voltages between the compensation capacitor and the Y-capacitor. A voltage clamping circuit may be employed to protect a coupler capacitor from overvoltage.