System for determining and supplying stabilized voltage from a power supply to a data processor after a fluctuating period

Abstract

A data processor, which is capable of preventing from causing a harmful influence due to an operation of the other loads, even when the data processor is powered by a battery, which is commonly used by the other loads. A vehicle-mounted personal computer as the data processor is powered by a vehicle-mounted battery via a main power supply circuit. When a key switch is turned on, a start-up circuit in the main power supply circuit outputs a start-up signal after a predetermined time has passed, so that output voltage from the vehicle-mounted battery is stable. After that, the main power supply circuit supplies power to the personal computer. As a result, the personal computer starts up by using a stable voltage. When the key switch is turned off, the personal computer moves to a sleep mode. When the key switch is turned on again, the personal computer returns to a previous condition by performing a resume process. As a result, it is not necessary to read and start up an Operation System every time the key is turned on. When the main power supply circuit detects a falling of the output voltage from the vehicle-mounted battery, the main power supply circuit stops supplying the power after shutting down the personal computer.