Coupled circuit and electromagnetic modeling of an LLC converter for EMI prediction

As a result of the trend towards higher electrification within the automotive world, there are increasing demands on the efficiency, power density and Electromagnetic Compatibility (EMC) of power electronic converters in such applications. The LLC resonant converter topology is commonly used due to its high efficiency, although its high-frequency operation generates significant Electromagnetic Interference (EMI). This thesis proposes a coupled circuit-electromagnetic method for predicting the conducted EMI of an automotive LLC converter. Initially, the design of an LLC resonant converter tailored to automotive applications was performed. Then, an EM model of the converter’s Printed Circuit Board (PCB) was developed using simulation techniques based on integral equations. The extracted EM model, which includes parasitic parameters and coupling paths, was then integrated into the equivalent circuit simulation. This combined model simulates both the converter’s electrical behavior and the distributed electromagnetic effects responsible for conducted emissions. The numerical procedure can be used for a better understanding and prediction of conducted emissions, thus reducing the need for iterative and costly redesigns.