Low-power self-oscillating fluxgate current sensor based on Mn-Zn ferrite cores

Abstract

A low-power open-loop self-oscillating fluxgate current sensor based on Mn-Zn soft ferrites is proposed in the paper. Differential realization of compensation amplifier, in class-D full-bridge configuration, provides full theoretical reduction of power consumption, which is impossible in the case of standard half-bridge realization. Together with data provided from the ferrite manufacturers, offered set of simple equations can qualitatively estimate quiescent and operating power consumption, and help in avoidance of design solutions that lead to unnecessary power losses. If a commercial or custom transformer core, made of conventional industrial Mn-Zn ferrite materials is used, all important parameters for sensor design, and follow-on exploitation, can be predicted in advance. Experimental examinations show that power consumption can be reduced to the level of open-loop Hall-effect based sensor, while many comparable advantages of flux-gate technology are maintained. We design sensor and tuned circuit parameters to measure currents in the range of [–20 A, 20 A] with an overcurrent capability of 50%. In temperature range of [–20 °C, 50 °C], maximum relative linearity error of 0.25% and offset drift of 0.05% is achieved.