Patent ID: 8188696
Filing Date: 2012-05-29
Classification: H02P

Abstract:
1. A motor drive circuit comprising: an H-bridge circuit including two sets of a high-side transistor and a low-side transistor, connected in series between a power terminal and a ground terminal, the H-bridge circuit being connected to a motor to be driven; a voltage difference detection circuit configured to output a terminal voltage that corresponds to a voltage difference that occurs between both terminals of the motor; a calibration circuit configured to calibrate a voltage drop that occurs at the ON resistance of one transistor selected from among the high-side transistor and the low-side transistor arranged on a path via which driving current is applied to the motor, using a calibration value that corresponds to the ratio between the resistance component of the motor and the ON resistance of the transistor thus selected, and to output the result as a calibration voltage that corresponds to the voltage drop that occurs due to the resistance component of the motor; a back electromotive voltage detection circuit configured to output a voltage that corresponds to the difference between the terminal voltage and the calibration voltage, as a detection voltage which indicates the back electromotive voltage that occurs at the motor; and a control circuit configured to drive the H-bridge circuit by pulse modulation such that the rotational speed of the motor that corresponds to the detection voltage approaches a designated rotational speed.