| 摘要 |
PURPOSE:To detect motor current accurately by synchronizing with PWM switching timing of voltages detected through two current detection resistors and switching the detected voltages according to the direction of the rotation of a motor. CONSTITUTION:Current detection signals VRCS1, VRCS2 appear in first and second current detection resistors 18, 19 respectively. Then they are subjected to impedance conversion and fed to an analog switch 7. The analog switch 7 outputs one of the signals VRCS1, VRCS2 being in high impedance state according to the rotary direction of the motor 20 and the state of a PWM signal. The output signal is fed to a hold circuit 6 the output therefrom is modified to the value of the signal VRCS1 or VRCS2 when any one of them is inputted, while previous value is kept when a high impedance state signal is inputted. By such an arrangement, motor current signals VRCS1, VRCS2 can be detected stably. |
