| 摘要 |
PROBLEM TO BE SOLVED: To provide a current limiting structure during control of a motor by a DC chopper circuit which can control the motor current by a pulse signal of the same frequency as in a normal operation even when a trouble occurs. SOLUTION: An operational amplifier 8 and external resistors R1 , R2 , R3 constitute a hysteresis comparator II. The hysteresis comparator II generates a pulse signal P2 which changes its state each time the motor current I detected by a current detector 6 when a CPU 7 has a trouble passes an upper limit value and a lower limit value of the hysteresis comparator II. The pulse signal P2 and a pulse signal P1 which is an output signal of the CPU 7 which has a 100% duty when the CPU 7 has a trouble are logic-operated by an AND circuit 9 and an operation result is output as a pulse signal P3 . By this method, the conduction state of an IGBT 5 can be controlled by the pulse signal P3 which has the same waveform as the pulse signal P2 . |
