PCB Rogowski Coil With DC Sensing for Double Pulse Test Applications

Accurately measuring the switching current behavior of wide bandgap devices requires a current sensor with a wide bandwidth covering dc to high frequency ranges. However, traditional Rogowski coils (RCs) for current sensing either lack the dc measurement capability or the inclusion of dc sensor largely increases the insertion inductance. This article presents a concept of combining a shielded RC with a dc sensor to improve the dc measurement capability without interfering with the power loop area of a double pulse test (DPT) circuit. The RC and dc sensor are positioned at different locations to capture the high-frequency and low-frequency components, respectively. An analog circuit combines the output of both sensors to recreate the signal. Frequency domain analysis of the prototype confirms the improved dc measurement of the probe. This article also presents the results of a DPT of a half-bridge SiC power module to demonstrate the enhanced dc measurement of the shielded RC, without any parasitic interference in the power loop area.