| 摘要 |
PURPOSE:To prevent breakdown of a switching element by performing pulse width control of an inverter circuit based on the detection value of motor currents flowing in the switching element of the inverter circuit so as to quicken motor current limiting operation and limiting the currents of the element itself by means of the load currents flowing in the switching element of a chopper circuit. CONSTITUTION:The motor currents IM to a brushless motor 70 are converted into voltage V2 by the resistance 65 inside an inverter circuit 60, and are compared with the set value VY in a comparator 96 for current limitation. When the motor currents IM are excessive, the pulse width of the chopper signal PC2 from a pulse width modulation circuit 100 is narrowed, and the on-time of the inverter circuit 60 is shortened so as to throttle the motor currents IM. The load currents IL flowing in a chopper circuit 20 are converted into voltage V1 by a detection circuit 31, and those are monitored by a current limiting circuit 35. When the load currents IL are detected as excessive by the comparison with the set value VX, the pulse width of the chopper signal PC1 from a pulse width modulation circuit 50 is narrowed by the signal phix: at a level of L, and the on-times of transistors 22 and 24 are shortened. so as to throttle load currents IL. |
