| 摘要 |
PURPOSE:To detect abnormality, in the control of load, accurately with no delay by extracting such frequency component as corresponding to the frequency component of pulse width modulated signal from the AC component of detected current in an abnormality detecting circuit for a pulse width modulation driving circuit which controls the load through a driving circuit. CONSTITUTION:When abnormal state of load is caused by damage or the like of a transistor 3, detection signal of a current transformer 6 contains no or very small amount of frequency component similar to that of PWM pulse signal. Since the output signal from a detecting circuit 10 has a level lower than a threshold, an abnormality judging circuit 11 makes a judgement that an abnormality has occurred. Consequently, a signal is provided from the abnormality judging circuit 11 to a contact 12 in order to open the contact 12, whereby source voltage supply to a load 4 is interrupted. |
