Importance of switched-mode power supply IC model for conductive EMI noise simulation

This paper proposes a modeling method for switched-mode power supplies (SMPSs) mainly focusing on IC model for conductive noise simulation. In modern automobiles, the number of electronic control unit (ECU) are increasing in order to implement advanced features and introducing an all-electric or hybrid drive system draws a high current. Since this requires higher efficiency power systems, SMPSs are widely used. Although systems using SMPSs produce switching noise as a side effect, they have to be designed to work as expected and to satisfy EMC regulation, too. To achieve this goal, it is imperative to predict and control the amount of noise at an early stage in the design by using accurate simulation models to reproduce the system behavior. Doing so greatly contributes to reducing design cost. However, it is very difficult to build SMPS IC models for noise simulation. In this paper, induced conductive EMI noise was evaluated through Electro-Magnetic (EM) and SPICE co-simulation following CISPR25 regulations. The SMPS, PCB, load device, line impedance stabilization network (LISN), and cables were all modeled to reproduce the regulation test environment. This model was validated by measurement on the same conditions as simulation.