Method and apparatus for sensing direct current of one polarity in a conductor and electronically commutated motor control responsive to sensed motor current

摘要

Apparatus and method for generating a sensing signal which is a function of a direct current flowing in a particular direction in a conductor. A core inductively coupled to the conductor is subject to negative magnetic saturation after a period of time as a result of a magnetic field generated by the direct current in the conductor. The aforesaid period of time is a function of the magnitude of the magnetic field generated by the direct current flowing in the conductor. An output winding around the core produces an output signal which is a function of the direct current in the conductor when the core is not saturated but which is not a function of the direct current in the conductor after the aforesaid period of time. A reset winding is periodically driven by a pulse to reset the magnetic orientation of the core to positive magnetic saturation before the aforesaid period of time elapses. As a result, the output signal produced between periodic resets has a magnitude which is a function of the direct current in the conductor and comprises the sensing signal. A motor voltage is applied to one or more winding stages of a motor in accordance with a regulating signal which is a function of the sensing signal. The winding stages are commutated in a preselected sequence to rotate a rotatable assembly of the motor.