A Novel T-Type Active EMI Filter Based on Sensing and Injection Multiplexing Configuration

In this letter, a novel T-type active EMI filter based on sensing and injection multiplexing configuration (T-AEF) is proposed. A three-capacitor T-type configuration is constructed to sense common-mode (CM) noise, inject CM noise and reduce differential-mode (DM) noise. Meanwhile, the sensed CM noise is amplified and tuned by a pure resistive based op-amp network. Distinguished feature of the proposed T-AEF is that the sensing and the injection part share the same three-capacitor branch and build separate RC T-type branch. Different from traditional AEF, it uses sensing and injection multiplexing configuration. This can attenuate both CM noise and DM noise simultaneously, which in turn, greatly reduce T-AEF components, cost, size and weight. Moreover, the whole circuit operates in a low voltage stress environment and can have good stability. A T-AEF prototype is built and tested in both 50 Ω standard environment and real ac–dc dc–dc noise environment. Experimental results show that the proposed T-AEF has good CM/DM attenuation effect in both ac side and dc side, and has small size and high stability.