Seiko Instruments Inc

Jun Miyanoiri

Shinichi Idomukai

Takashi Kohata

Tomoyuki Nakaue

Teruyuki Iwashima

Provided is a power supply switching circuit with a smaller circuit scale. When a detector () detects that a voltage (V) as an input power supply voltage is higher than a detection voltage (VDET), a control circuit () operates with a voltage (V) output from a diode OR circuit (), supplies a voltage (V) as an input power supply voltage to a gate of a PMOS transistor (), supplies a voltage (V) to a gate of a PMOS transistor (), and supplies a ground voltage to a gate of a PMOS transistor (). Then, the PMOS transistors (and) are turned OFF and the PMOS transistor () is turned ON. In this case, the voltage Vof a first terminal (T) is output from a third terminal (T) as the voltage (V), which is an output power supply voltage.

Power supply switching circuit

Provided are a voltage application time period measuring circuit which does not require a battery, and a power supply apparatus including the voltage application time period measuring circuit. Each of a voltage application time period memory () and a set time period memory () is a nonvolatile memory, and hence it is unnecessary to provide a battery for holding information stored in each of the memories in the outside of the voltage application time period measuring circuit () and a power supply apparatus cost is reduced correspondingly.

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Chiba, Japan

Jun Miyanoiri