| 摘要 |
PROBLEM TO BE SOLVED: To uniformly maintain charge by providing a switching circuit for selectively turning on/off two DC power supplies. SOLUTION: A zero crossing detector 26 is connected to a potential feedback calculation amplifier 28. Therefore, after a potential from one power source applied to a corona wire 14W is turned off based on a feedback signal from a calculation amplifier 28, the detector 26 determines a time for falling into 0, when that potential falls into 0 an output signal is fed from the detector 26 to a switching logic 20, and this logic 20 turns on another power supply switch. Consequently, power sources 12p and 12n can be prevented from being turned on simultaneously by the logic 20. Thus, since two dependent power sources are used, if assistance is required while cleaning a device, a corona can be maintained positively or negatively. |
