Patent ID: 10302678

Abstract:
A motor current measurement circuit (7) includes a sense resistor (8) located in a path through which, in use of the motor (1), at least a part of the current flowing into or out of the motor flows, a first amplifier which comprises a differential amplifier (9) which has a first input and second input which are respectively connected to the opposing ends of the sense resistor and has an output at which the amplifier (9) is arranged to produce, in use, an output signal representative of a voltage dropped across the resistor (8) and hence the current flowing through the resistor (8), and an analogue to digital converter (12) having an input which is connected to the output of the first amplifier (9) and an output. The converter (12) is arranged to provide at its output a digital signal representing the current flowing through the sense resistor (8), and the first amplifier (9) comprises a transconductance amplifier whereby the output signal comprises a current which is proportional to the input voltage across the two inputs.