Planar electromagnetic integration technologies for integrated EMI filters

Planar electromagnetic integration technology has been the topic of research over the last few years. Its applications to the resonant and nonresonant switch mode power supplies (SMPS) have been reported in the past. However, this technology was mostly applied in the integration of power electromagnetic components, such as HF transformers, resonant/choke inductors and resonant/blocking capacitors, for SMPS circuits. Very little work has been done on the subject of filter integration. Since an EMI filter has different functions and has different requirements, accordingly special technologies are required. To bridge this gap, technologies to improve the high frequency performance of the integrated EMI filter are proposed, which include reducing the equivalent series inductance (ESL), reducing equivalent parallel capacitance (EPC) and increasing the high frequency noise damping factor. Based on these technologies, an improved integrated EMI filter structure is developed. The effectiveness of these technologies has been evaluated by finite element analysis (FEA) simulation results. Experimental results are also given.