Accuracy analysis of shunt current sensing by means of delta-sigma modulation in electric drives

This paper considers the accuracy of the shunt current measurement by means of delta-sigma modulation in electric drives. The shunt current sensing becomes more popular with the appearance of the galvanically isolated delta-sigma modulator ICs and microcontrollers with embedded demodulators. This solution is much cheaper than closed-loop Hall-effect sensor, and it is already implemented in some commercial electric drives. In this paper the accuracy of delta-sigma bitstream demodulation is considered. The dependences between oversampling ratio, digital filter type, input signal value and the maximum error were obtained from the model.