Attenuation of Fundamental Component of Differential Mode Noise Using Active EMI Filter

This paper introduces a boost converter in conjunction with a synchronized switch mode Active EMI Filter (AEF), which reduces energy storage requirements compared to a passive EMI filter. The proposed AEF operating at a frequency of 30 MHz effectively mitigates additional EMI into the system as its operational frequency lies beyond the typical range of conducted EMI. The AEF is realized using a synchronous buck converter with a series resonant tank and the current configuration is designed to counteract the fundamental ripple component of the boost converter. Duty-controlled switching is implemented in the proposed AEF using high-speed analog circuits to generate pulse width modulated (PWM) signals for the filter. The proposed methodology controls the magnitude of AEF current to a desired value using a modulating signal $(\hat m)$ in an open loop to reduce the complexity of the circuit. The AEF is employed in a (6-12)V-to-24V boost converter switching at 150 kHz and has been found to attenuate the fundamental ripple component by 23dB based on the experimental results.