EMI Suppression of DC-DC Converters by Injecting Synthesized Pulse Signals

Using an active EMI filter to suppress EMI can greatly reduce the size of the filter. However, active EMI filters are generally based on feedback structures, which are very complex and not easy to implement. In this paper, a novel digital active EMI filter for suppressing conducted EMI in DC-DC converters is proposed. Firstly, a pulse signal is generated with the same period as EMI noise, and injected into the converter to suppress EMI noise. The proposed digital filter can avoid the influence of propagation delay and simplify the filter structure. Then, the specific operation steps are investigated to obtain the correct parameters of the injected pulse signals. The experimental results finally show that the proposed digital active EMI filter effectively suppresses the conducted EMI in the frequency band of 150kHz-30MHz.