A 20-MHz Wideband Current Sensor Utilizing a Frequency Band Optimized Tunnel Magnetoresistance Bridge Chip

The demand for innovative digital grid technologies necessitates the development of high-frequency (HF) current measurement techniques, extending into the tens of MHz range, to enhance power grid monitoring capabilities and monitor discharges in power equipment. However, monitoring of HF partial discharge current remains challenging for the current sensor because of the limitations imposed by the restricted bandwidth of the magnetoresistance chip and the back-end circuitry of the sensor. Therefore, a 20-MHz wideband current sensor is designed employing a tunnel magnetoresistance (TMR) bridge chip optimized for the frequency band. The factors that affect the bandwidth limitation of TMR current sensors are examined. On one hand, by enhancing the frequency response of the TMR chip, we successfully fabricated chips with a bandwidth exceeding 50 MHz, representing a significant improvement compared to commercially available chips limited to only a few megahertz. On the other hand, optimization strategies were implemented for expanding the bandwidth of printed circuit board (PCB) integrated TMR current sensors, resulting in a maximum achievable bandwidth of up to 20 MHz. The developed sensors were tested to measure the discharge current in a needle-plane electrode, thereby confirming their suitability for HF discharge current measurement.