Transformer based DC current sensor for digitally controlled power supplies

Twenty years ago, R. Severns presented a transformer based circuit which is able to measure DC currents. However, this circuit did not experience a break-through in the industry or even academic world because it requires too many components and is unable to measure small currents. This paper enhances this circuit so that it becomes feasible to measure currents down to zero. The circuit complexity is no longer an obstacle because in digital controlled power supplies the DSP provides the required auxiliary functionalities. The feasibility of the proposed circuit has been proven by hardware experiment.