Patent ID: 6570360
Filing Date: 2003-05-27
Classification: G11B,H02P

Abstract:
A method for driving a phase of an electrical spindle motor driving a data storage disc in a disc drive, the method comprising steps of:a) detecting a back electromotive force being generated by a coil of the phase by: a)(i) measuring a total voltage applied to the phase of the motor; a)(ii) measuring a resistive loss voltage dropped across the phase of the motor; and a)(iii) detecting the back electromotive force by finding a difference between the total voltage and the resistive loss voltage; b) amplifying the back electromotive force; and c) driving the phase with the amplified back electromotive force,wherein the disc drive includes a first difference amplifier circuit having unity gain with inputs connected across the coil of the motor, and wherein step a)(i) comprises a step of applying the total voltage across the inputs of the first difference amplifier circuit, wherein the disc drive includes a sense resistor connected in series with the coil and a second difference amplifier circuit with inputs connected to each side of the sense resistor, wherein a gain of the second difference amplifier circuit is equal to a resistance of the coil divided by a resistance of the sense resistor, and wherein step a)(ii) comprises a step of applying a sense resistor voltage drop across the inputs of the second difference amplifier circuit.