| 摘要 |
PURPOSE:To improve space factor by providing a primary relay for changing over the taps of a transformer having power ON/OFF taps, a secondary relay for turning power supply to a load ON/OFF, and a relay drive circuit for controlling the relays. CONSTITUTION:When a switch 7 is depressed to turn OFF power, a relay 11 is switched to break contact (b) and a primary power supply voltage is applied on the primary taps P1, P5 of a primary transformer 10 while at the same time a relay 12 is turned OFF to interrupt power supply to a load 5. At that time, only the load of backup power supply, i.e., the relays 11, 12 and a control circuit 6, is applied on the primary transformer which is thereby rendered substantially no-load. Consequently, a power supply reducing circuit can be constituted without requiring a backup transformer, resulting in cost reduction and improvement of space factor. |
