| 摘要 |
PURPOSE:To reduce power consumption and to prevent the temperature of a switching power supply in its waiting state from being increased by utilizing a ringer signal from a telephone line and controlling the starting current of the power supply by a photocoupling element. CONSTITUTION:When a network control part 15 receives a ringer signal from a telephone line LA, a light emitting element 3a in the photocoupling element 3 is emitted, the photodetecting element 3b of a photocoupling element 3 in a power supply part 16 is turned on, a starting current is supplied to a switching power supply control circuit 7 through a starting resistor 9 and the operation of the switching power supply is started. The above constitution make it possible to automatically start the switching power supply of this system and remarkably reduce power consumption in its waiting state, and the rise of the power supply temperature in the waiting state is suppressed, design for mounting the switching power supply on the device can easily be executed. |
