| 摘要 |
PROBLEM TO BE SOLVED: To provide a drive circuit which is inexpensive and little in vibration and noise by detecting the timing of two-phase excitation and three-phase excitation from the drive pulses of external input, and changing the duty of a PWM circuit so as to let a total current flow a little at two-phase excitation and much at three-phase excitation. SOLUTION: A timing logic circuit 2 detects the timing of the two-phase excitation and three-phase excitation of a three-phase excitation winding 5 from the input of a drive pulse generating circuit 1, and outputs a signal, and an electronic switch 12 operates with the output signal of the timing logic circuit 2 and the reference voltage of a reference voltage generating circuit 11d. A PWM circuit 7 varies the total current with the output signal of the electronic switch 12 and the signal of the current detector 6 for detecting the total sum of a drive current, and a current application control means 7a within the PWM circuit 7 changes the pulse width so as to let the total current flow a little at two-phase excitation and much at three-phase excitation. Then, a base drive circuit 3 drives an inverter circuit 4 with the output signal of the PWM circuit 7. |
