| 摘要 |
PURPOSE:To obtain a prescribed output surely by driving a DC-DC converter after a prescribed electric charge is stored in a capacitor by a control means comprising a voltage supervising circuit and a control circuit. CONSTITUTION:When a line is idle, a constant current supply circuit 9 is activated by a drive signal 7a from a terminal controller, and constant current outputs 10, 10 are obtained from station feeding lines 8, 8. A voltage rises slowly by the effect of a large capacity capacitor 12 and an oscillator 13 starts gradually oscillation. An output of an operational amplifier 24 of a voltage supervising circuit 17 is at ''high'' at the initial state, a transistor 28 of a control circuit 18 is turned on, an output 19 of the control circuit is at ''low'' and no DC-DC converter drive circuit 15 is driven. When the capacitor 12 is charged sufficiently and a sufficient voltage is produced by a constant element 11, the DC-DC converter drive circuit 15 is operated conversely. |
