| 摘要 |
PURPOSE:To protect a motor against heating by providing a PWM signal generator which includes a comparator; a full-ON detecting circuit; a duty factor signal generating circuit; and a duty factor selecting circuit which receives a PWM signal, a full-ON detection signal and a duty factor signal to selectively produce a PWM signal. CONSTITUTION:A torque signal 4 fed from an adder 11 is compared with a triangular wave signal 5 in a comparator 81 to produce a PWM wave signal 6. In a duty factor signal generating circuit 83, a magnetic pole signal (a) is converted into a unilateral signal (b) at an absolute value circuit 83a thus producing a duty factor signal (c) from a comparator 83b. An AND gate 84b receives the PWM signal 6 from the comparator 81, an output from a full-ON detection circuit 82, and the duty factor signal (c) and produces a PWM signal (e) upon detection of full-ON state. By such arrangement, the motor can be protected against heating. |
