Circuit for providing a signal proportional to the average current flowing through coils of a motor operated in both linear and PWM modes

摘要

A circuit for providing a signal proportional to the average current supplied to the coils of a motor operated in both linear and PWM modes includes a sense resistor across which a voltage representing the current flowing supplied to said coils is developed. The voltage is selectively applied to an output circuit which operates as a low pass filter circuit when drive current is supplied to the coils and as a voltage hold circuit when drive current is not supplied to the coils. The output circuit includes an amplifier connected to receive a voltage produced by the sense resistor when the motor is operated in the linear mode, and a capacitor and a resistor connected in parallel, the capacitor and resistor being connected between an input and an output of the amplifier to operate as a low pass filter circuit. A switch circuit operating in response to PWM signals disconnects the voltage developed across the sense resistor from the amplifier, and disconnects the resistor from the capacitor when drive current is not supplied to the coils to operate as a voltage hold circuit.