Referring to FIG. 3, which is a circuit diagram of a second embodiment according to the present invention for use with the implementing example shown in FIG. 1A or 1B, in the permanent-magnet synchronous motor driving and resistance control system 100a of the instant embodiment, constituent components are generally similar to those of the first embodiment, so that, for consistency purpose, identical elements are designated with the same reference numerals. In the instant embodiment, the processing unit 61 of the control device 6 is internally built up with a PWM control circuit 611 that controls the motor driving circuit 62, and an A/D converter 612 that receives the feedback signal from the feedback circuit 66. The feedback circuit 66 may comprise one of a current feedback circuit, a voltage feedback circuit, a Hall component, and a temperature component. The processing unit 61 of the control device 6 may further be built therein with a quadrature encoder pulse circuit 613, which is connected, via an optically coupled isolator 614, to the angle detection unit 65 to detect an angle of a rotating spindle of the permanent-magnet synchronous motor 3.
