| 摘要 |
<P>PROBLEM TO BE SOLVED: To detect a counter electromotive voltage favorably. <P>SOLUTION: A motor drive circuit 100 includes an H bridge circuit 10, a potential difference detecting circuit 20, a calibration circuit 30, a counter electromotive detection circuit 40, a control circuit 50 and a calibration value acquiring circuit 60. The H bridge circuit 10 is connected to a DC motor 1. The calibration circuit 30 outputs a calibration voltage Vc according to a resistance component Rm. The potential difference detecting circuit 20 outputs a voltage-across-ends Vh according to a potential difference of both ends of the DC motor 1. The counter electromotive detection circuit 40 outputs a voltage according to a difference between the voltage-across-ends Vh and the calibration voltage Vc as a detected voltage Ve showing a counter electromotive voltage Eg. The control circuit 50 drives the H bridge circuit 10 by a pulse-duration modulation. The calibration circuit 30 calibrates a voltage drop generated in an on-resistance of a low-side transistor by using a calibration value according to a ratio of the resistance component Rm and the on-resistance of the low-side transistor and regards the calibrated voltage as the calibration voltage Vc according to the resistance component Rm. <P>COPYRIGHT: (C)2010,JPO&INPIT |
