Study on Mitigating the Capacitive Noise Coupling Paths in Phase Shifted Full Bridge Converters

The design of automotive power electronics to fulfill the requirements of electromagnetic compatibility (EMC) is increasingly challenging. This especially applies to compact high-voltage applications in electric powertrains. The phase shifted full bridge (PSFB) is commonly used as the main DC/DC converter in electric vehicles. Unfortunately, the compact size gives rise to several undesirable effects, including parasitic capacitances. These noise coupling paths enhance the propagation of electromagnetic interference (EMI), and therefore they should be minimized. To investigate how much the parasitic capacitances affect the conducted emissions, a circuit model of a 1.5kW PSFB DC/DC converter was created. With the simulation-based findings presented in this paper, developers can have a deeper understanding on the extent to which parasitic capacitances contribute to EMI in a PSFB power supply. A theoretical explanation and measurement results are provided at the end of the paper to support the conclusions of the simulation experiments.