High-Bandwidth Isolated Voltage Measurements With Very High Common Mode Rejection Ratio for WBG Power Converters

Galvanically isolated voltage measurements are becoming increasingly important for the characterization of converter systems with fast switching Wide-Bandgap (WBG) semiconductors. A very high Common Mode Rejection Ratio (CMRR) $\mathbf {>\,80\,}$ dB frequencies up to several tens MHz is required accurately measure, e.g., high-side gate-source or drain-source in a half-bridge, voltages on floating potentials as, found multi-level converters. all listed measurement scenarios changing reference potential, which acts as (CM) disturbance. This article derives minimum necessary CMRR at different constrain time-domain error below certain limit. Thereby, only switched and transition rate ( {\text{d}\mathit{v}/\text{d}\mathit{t}}$ ) CM disturbance be considered not actual frequency {\mathit{f}_\text{sw}}$ . Afterwards, galvanically system {>\,100}\,$ {100}\,$ an analog bandwidth {130\,}$ presented. Critical design aspects achieve this performance investigated. Compared commercially available probes, presented measurement system does require any additional equipment like oscilloscope perform visualize measurements, since data already digitized/sampled thus can transmitted directly host device (e.g., computer monitoring system) corresponding Graphical User Interface (GUI) software. Experimental verification frequency- confirms that par best probes.