Rogowski-Pair Sensor for High-Speed Switch Current Measurements without Reset Requirement

Amongst several existing non-invasive switch current measurement solutions, the PCB-embedded Rogowski coil has a few more advantages to be used for high-frequency, compact, and high-power designs, especially due to being air-cored. This is while, negligible low-frequency gain, as well as integrator circuit configuration, resulting in a droop for the Rogowski coil detector output. Increasing the nominal switching frequency to hundreds of kilohertz and above causes the droop issue to become much more complicated to tackle, such that, provisional solutions such as the addition of electronic reset would also be near impossible to implement, due to very small on-time. In this paper, a novel complementary PCB-embedded Rogowski-pair detector is proposed to remove the droop burden, while maintaining high-frequency performance. The main idea is to pair up identical coils and allocate one to detect the DC component of the measured switch-current, while the other coil measures a fully AC-coupled signal. Given the characteristics of the switch-current waveforms, an analog electronic circuit combines the two sensor outputs and compensates for the absence of the DC component measured by a normal Rogowski coil. A well-tuned Rogowski-pair was prototyped and tested to measure the switch current of a high-speed Silicon-Carbide (SiC) module.