Power supply switching circuit for a compact portable telephone

Details Power supply switching circuit for a compact portable telephone Power supply switching circuit for a compact portable telephone

1992-07-07

1994-08-02

Kuntz, Curtis

Telephonic communications

Having light wave or ultrasonic link for speech or paging...

Including fiber optic link within telephone network

455343, H04M 1100

Patent

active

053352637

ABSTRACT:
In order to reduce volume and weight of a power supply of a compact portable telephone set and thus reduce volume and weight of the compact portable telephone set itself, a P-channel power MOSFET is used as a power switching element, and a negative voltage, for example, -11 volts is applied across a source and a gate from a DC/DC converter to turn on the P-channel power MOSFET so that power is supplied from a battery 2 which serves as one power supply. When the gate and the source of the power MOSFET are maintained at the same potential, the power MOSFET is turned off and power is supplied from another power supply.

REFERENCES:
patent: 4511761 (1985-04-01), Yamazaki et al.
patent: 4647722 (1987-03-01), Nishida et al.
patent: 4852147 (1989-07-01), Suzuki et al.
patent: 5170491 (1992-12-01), Murata
Schilling, et al, "Electronic Circuits, Discrete and Integrated", 1979, pp. 139-145, 161, 162, 166, and 167.
"Battery Switching Circuit for Dual-Battery Systems," IBM Technical Disclosure Bulletin, vol. 31, No. 12, May, 1989.
"Power Supply Isolator for RAM Back-Up Battery," IBM Technical Disclosure Bulletin, vol. 26, No. 6, Nov. 1983.

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