Investigating the CM Noise Generated by Different Configurations of Multiple Forward Converters

Switched-mode power supplies (SMPSs) are utilized with fast-switching wide band-gap devices that operate at switching frequencies in the hundreds of kHz range and very short switching time. As a result of the wide spectrum, electromagnetic interference (EMI) is a critical issue for SMPS. The size and weight of power line filters can decrease as the frequency increases. Higher frequency, on the other hand, increases the generated EMI noise, so the size and cost of the required EMI filters are difficult to assess due to conflicting requirements for high power density applications. Conversely, as parasitic effects become more dominant in the high frequency range, increasing switching frequency may result in higher levels of high frequency EMI noise. Connecting multiple converters in the input and output ports have demonstrated their effectiveness in reducing EMI, such as interleaving, which connects in parallel for both ports. However, other configurations based on series and parallel at the two ports have not been addressed. This paper will address three different configurations for connecting two forward converters in comparison with single forward converter. Based on the simulation of three configurations, this paper shows that the CM noise is highly influenced by the input node parasitics.