| 摘要 |
PURPOSE:To enable a power unit which is shared by systems of different input voltages to properly output a detecting signal when the input voltage of each system becomes lower than a prescribed value. CONSTITUTION:The system of an input voltage is discriminated by comparing the detected value of the input voltage of a power source circuit 1 provided with a power transformer T11 with a prescribed set voltage by means of an input voltage comparator circuit 6 and, at the same time, the detected value of the voltage across the winding N3 of the transformer T11 with a prescribed set voltage by means of a winding voltage comparator circuit 2 and the discriminated information is held by a flip flop 4. Then the level of the input voltage to the circuit 6 is made to correspond to the system of the input voltage by controlling a transistor Tr51 with the output of the flip flop 4 and, when the input voltage from the circuit 6 becomes lower than a prescribed value, its detecting signal is outputted. |
