| 摘要 |
PURPOSE:To make possible the extremely high reliability detection of abnormal current by interposing a current detecting means between a high-voltage power source and an electrostatic recording drive circuit and driving a relay by the output having sampled the output thereof. CONSTITUTION:When a recording drive circuit 2 is normal, the output of a photo coupler 4 by the current of a high-voltage power source 1 is waveform-shaped by a waveform shaping circuit 16 and becomes the waveform similar to the timing pulse signal S8 and therefore the JKFF9 clocking the synchronizing singal S5 does not operate. When the switching transistor of the circuit 2 is broken down, the current of the power source 1 keeps flowing at all times and therefore the output of the photo coupler continues to operate. Because of this, the FF9 is set by the first signal S5 and thereafter it repeats inverting at every signal S5. This output is inputted to a counter 10. The counter 10 is so arranged as to cut off the power source 1 by resetting a relay 11 when the FF9 inverts a certain number of times. Thereby, the abnormal current detection of extremely high reliability may be accomplished. |
