Design of effective surge protection circuits for an active EMI filter

An effective design method of surge protection circuits for an active EMI filter (AEF) is proposed. The overcurrent and overvoltage at the voltage-sense voltage-compensate type AEF due to a surge is analyzed, and protection circuits using the transient voltage suppression (TVS) diodes are designed. Effects of protection circuits are validated by a 2kV surge test. Performances of the AEF for the noise attenuation are also measured by a vector network analyzer (VNA), and the AEF performances after employing the protection circuits are compared.