| 摘要 |
PURPOSE:To prevent abnormal voltage across changeover contacts from occurring, by operating an electric discharge lamp changeover circuit earlier than a power stoppage detection circuit when an AC power source is cut off and by operating the power stoppage detection circuit earlier than the electric discharge lamp changeover circuit when the power supply is recovered from the AC power source. CONSTITUTION:Immediately after an AC power source is cut off, contacts 101 and 102 are changed over to (b) side with an electric discharge lamp changeover relay 1. On this occasion, no high frequency voltage is applied across contacts since an emergency lighting inverter operates after the changeover. Immediately after the AC power supply is recovered, the contacts 101 and 102 are changed over to (a) side with the electric discharge lamp changeover relay 1. On this occasion, no high frequency voltage is applied across the changed-over contacts since the electric discharge lamp contacts are changed over after a power stoppage detecting transistor 14 and a driving transistor 15 stopped at the same time. |
