Digital Active Common Mode EMI Suppression Technique for Switching Converters

Based on analyses of common mode (CM) EMI suppression methods for switching converters, a digital active CM EMI suppression technique is present. A push-pull active compensating circuit produces a compensating current with anti-phase relationship to the CM noise current of the converter. Whether driving signals transmission delay of compensating circuit and main bridge are the same or not will impact the effect of CM current suppression. In order to resolve the problem, a fine-tuning system with close-loop control based on simulated annealing algorithm (SAA) is proposed. An experimental bench of single-phase half-bridge converter, which consists of digital active EMI suppression system based on TMS320F2812, is constructed. Experimental results show that the CM EMI can be attenuated by 10-15 dB up to 10 MHz and it proved the compensating circuit and suppression method based on SAA are valid. It can improve EMC performance of power electronic converters effectively.