| 摘要 |
PROBLEM TO BE SOLVED: To prevent a circuit malfunction caused by undesired noises generated by electric discharge between relay contacts when turning on or off a hollow cathode lamp. SOLUTION: A switch circuit 11 for applying high voltage onto the hollow cathode lamp 17 is composed of a high voltage-proof FET 15 and a photocoupler 12 of an LED / photodiode array coupling type. The high voltage-proof FET 15 is available at a relatively low price because of having a N channel-type structure, and a control circuit 10 can be insulated from the FET 15 applied with the high voltage by the photocoupler 12, thereby increasing its safety. The electric discharge does not occur when the FET 15 is turned on and off, and of course, spike-like noises are not generated. COPYRIGHT: (C)2004,JPO |
