A Customized Integrated Circuit for Active EMI Filter With High Reliability and Scalability

This article proposes an active electromagnetic interference (EMI) filter (AEF) realized by a customized integrated circuit (IC) to reduce conducted emission noises. A fully transformer-isolated feedforward current-sense current-compensation structure is selected as a base topology of the AEF. To achieve the high reliability of the proposed AEF by using low-voltage IC devices, the injection transformer is added to protect IC devices from high-voltage hazards. The operation of the proposed AEF is theoretically demonstrated, and practical design guidelines for the IC part and nearby components are developed. The designed IC was fabricated by a 0.18 mu m bipolar-CMOS-DMOS process. The fabricated IC is implemented in a compact printed circuit board for application to a three-phase inverter motor system. The performance, stability, and surge immunity of the AEF are experimentally demonstrated. A designed 1stage AEF achieves better noise-attenuation performance than 2stage passive EMI filters (PEFs) over 6 dB at 150 kHz without critical resonance peak at the high-frequency range. Weak points of the conventional PEFs in both low and high frequencies are effectively improved by using the proposed 1stage AEF. In addition, the surge immunity of the designed IC within the AEF is validated under numerous 5 kV surge tests.