The design of a high-precision, wide-range TMR-based current sensor

The flexible integration of DC grids in renewable energy systems offers advantages in terms of interaction between generation, grid, load, and storage, as well as reducing distribution losses. This makes it a key role in energy transition and carbon emission reduction. With the large-scale application of low-voltage DC grids in electric vehicle charging infrastructure, data centers, telecom base stations, residential or commercial areas, photovoltaic systems, and etc., the demand for DC energy meters with wide-range, high-precision, real-time measurement capabilities is rapidly increasing. Magnetic sensors based on tunneling magnetoresistance (TMR) have advantages such as high sensitivity, good linearity, low temperature drift, wide range, low power consumption, and compact size, making them highly promising for noncontact high-precision current detection. This paper conducts magnetic simulation analysis and proposes a current sensor structure that can accurately measure magnetic fields while effectively shielding external magnetic interference. Additionally, based on the output characteristics of TMR devices, a circuit design is implemented using a high-precision reference source to power the TMR and a fully differential amplifier for signal amplification. Test results show that the current sensor has low power consumption (<3mW) and, within a range of 0-360A, achieves a non-linearity of less than 0.2% through segmented calibration. It exceeds Class 0.2s accuracy according to the IEC61869-2 standard. This makes it suitable for applications where precise measurements are essential, even at low current values.