| 摘要 |
PURPOSE:To enable a capacity of a power-supply circuit to be small and especially a power-supply circuit at a sub power-supply side to be miniaturized by switching a main power-supply switch from OFF to ON with a control signal and at the same time starting a main power-supply device for a main electronic circuit and then immediately switching the powersupply circuit. CONSTITUTION:When a control signal VA is set to a high level H, a current consumption of a sub logic circuit 10 increases and a current Is becomes an operational current and then a switching transistor 9 is turned on when the voltage VA reaches 4.7V. Then, supply of power is switched to a voltage from an output side of a main power-supply switch 4 which is connected to an output line of a main power-supply circuit 3 from a sub power supply from a three- terminal IC7 and then a current iM becomes an operational current and a current iS nearly reaches 0. Then, when a control signal is turned from OFF to ON level, a voltage VB from the main power-supply circuit 3 begins to drop, a side of a sub-logic circuit 10 changes into a waiting state so that current is reduced greatly and current is supplied from the side of the main power-supply circuit 3. |
