Power supply circuit
AssigneeRohm Co., Ltd.
InventorToshimasa Tanaka
Life of this patent
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Abstract
A power supply circuit is provided with a first battery, a second battery, an output terminal, and a voltage dividing circuit for dividing a voltage from the first battery. An output voltage of the dividing circuit is compared with a voltage of the second power source by a comparing circuit. A first P-channel-type MOSFET is connected between the first battery and the output terminal. A second P-channel-type MOSFET is connected between the second battery and the output terminal. Depending on an output from the comparing circuit, one of the MOSFET is turned on, and the other is turned off.
Claims8
A power supply circuit, comprising:
- a first power source;
- a second power source;
- an output terminal;
- voltage dividing means, connected to said first power source, for dividing a voltage of said first power source;
- comparing means, connected to said second power source and an output of said voltage dividing means, for comparing the output of said voltage dividing means with said second power source;
- and
- selecting means, connected to an output of said comparing means, for selecting either said first power source or said second power source depending on the output of said comparing means and for supplying a selected voltage to the output terminal.
A power supply circuit, comprising:
- a first power source;
- a switch connected between said first power source and a main circuit for turning the power on and off;
- a second power source;
- and
- a power source switching circuit, having a first input terminal connected to the output of said switch, a second input terminal connected to said second power source, and an output terminal connected to a memory, said power source switching circuit includes a voltage dividing means, connected to said first and second input terminals, for dividing a voltage at said first terminal,
- wherein said power source switching circuit supplies to the memory alternatively either a voltage at said first input terminal or a voltage at said second input terminal depending on whether a voltage obtained by dividing the voltage at the first input terminal is higher or lower than that at the second input terminal.
Dependencies are inferred from the claim text.