In power conversion circuits used in power electronics, electromagnetic noise is generated by switching operations. The electromagnetic noise generated is either conducted noise that travels through the wiring or radiated noise that is radiated into the space with the wiring acting as an antenna. To suppress electromagnetic noise, it is effective to identify its source and clarify its propagation path. In the periodic steady-state operation of a power conversion circuit, the electromagnetic noise generated is also periodically repeated. The time and spatial distribution of noise currents on a power conversion circuit in a periodic steady state are measured with a magnetic field probe as time-domain data synchronized with switching operations, and a time-frequency analysis is performed to determine the frequency-specific occurrence and propagation of electromagnetic noise. We are developing a device to visualize the generation and propagation of electromagnetic noise at each frequency by time-frequency analysis. |