Utilizing a Micro-Fluxgate Magnetometer in Dual-Path Configuration for Fast Switch-Current Sensing

There has been a growing interest in hybrid current sensors since they can combine a DC/low-frequency detector with a high-frequency current transducer to cover an ultrawide range of frequencies. Hybrid current sensors are used in a variety of applications, such as power electronics, motor control, and medical technology. They are also used for safety monitoring and power quality measurements. As a result of their size/bulkiness, EMI immunity, intrusiveness (or the introduction of parasitic elements and losses), nonlinearity (due to magnetic core saturation or temperature drift), cost, accuracy, and others, many of these devices are not appropriate for measuring switching currents (particularly in wide bandgap switches). In order to overcome the problems mentioned above, the present work combines an on-chip fluxgate magnetometer and a Rogowski coil embedded on the same PCB. Both of these sensing elements have the ability to measure the current accurately and have low parasitic elements and losses. This combination results in a compact, inexpensive, and accurate current measurement system. As the low-pass-filtered fluxgate element measures current from DC to around 16 kHz, the embedded Rogowski coil is underutilized for sensing higher frequencies starting from 16 kHz to tens of MHz. Based on a set of power electronics converter experiments, their added output provides superior performance for capturing the switching current waveform of wide bandgap semiconductors.