A 770 kS/s Duty-Cycled Integrated-Fluxgate Magnetometer for Contactless Current Sensing

Electric vehicle battery chargers, solar-panel inverters, industrial power monitoring, and many other high voltage applications rely on magnetic sensors for contactless current sensing over shunt-based sensors due to inherent galvanic isolation [1–4]. Within magnetometers, integrated fluxgate (IFG) sensors provide nT resolution versus $\mu T$ accuracy of Hall sensors [1–4]. To linearize IFG response, magnetic fields are balanced out in the core using large compensation currents at high fields, making them power hungry $(\gt100$ mW for 2mT) [1,2]. Previous IFG sensors were designed for continuous operation at high sampling rates, but with long initial convergence time $(200 \mu s)$, preventing them from being duty cycled efficiently to reduce average power consumption at lower BW [2,5]. High power is prohibitive for many low-BW and coreless applications [6,7] that use an array of IFG sensors to achieve stray field rejection in order to save area, cost, and installation effort.