Conducted EMI Simulation for a DC-DC Converter: a DC Brush Motor System Considering Showering Arc at Mechanical Contacts

Abstract

This paper provides an overview of a circuit analysis model for a DC brush motor, taking into consideration showering arc events. A mechanical contacts model that reproduces showering arc behavior is developed by combining new variable resistors with the steady arc model. As a result, spike surge waveforms can now be simulated via circuit analysis. It is also become clear that spike surges with continuous showering arcs constitute the maximum condition of conducted EMI. The measured and simulated conducted EMI show good agreement within 9 dB up to 108 MHz, in accordance with the CISPR 25 standard. Moreover, it is now possible to quantitatively predict the amount of conducted EMI in a system comprising a step-down DC-DC converter and a DC brush motor, by considering a dominant magnetic coupling and parasitic impedances.