EMI Coupling Mechanisms and Mitigation in a DC-DC converter 2019-01-0609
In the electrified vehicles, a DC-DC converter is used to convert high voltage DC from traction battery to low voltage DC to provide 12V loads inside the vehicle, including audio, navigation system, air conditioning, etc. It is important for a DC-DC converter to meet all the EMI standards in various frequency ranges for both conducted and radiated EMI. In order to meet the standards, EMI filters are generally designed and utilized at the converter HV side and LV side to help mitigate the noises at the terminals. However, the non-ideal parasitic parameters and magnetic coupling mechanisms may lead to the EMI filter performance degradation and cause excessive emissions.
In this paper, the EMI coupling mechanisms of a DC-DC converter in electrified vehicles are investigated for both conducted and radiated EMI. The noise sources and propagation paths are identified and quantified. The results show that the magnetic coupling between noise sources to some sensitive locations, including HV/LV terminals and CAN connector, can cause excessive emissions. The coupling between different components of the EMI filters may also lead to the degradation of the filter performances. Strategies are proposed to reduce the coupling, improve the filter performance and mitigate the emissions. The performances are verified in experiment.