Electronic circuit with power drain control
First Claim
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1. A power switching circuit for selectively coupling an output terminal to a first or a second battery, the circuit comprising:
- a first input terminal for connection to the first battery;
a second input terminal for connection to the second battery;
an output terminal;
first switching means responsive to the voltage of the first battery for selectively switching the output terminal from the first to the second input terminal in response to the voltage of the first battery falling to a first predetermined level, said first switching means including a comparator coupled to compare the voltage of a primary one of said first or second batteries at the first input terminal with a first reference voltage;
second switching means controllable by said first switching means;
a second output terminal coupled to the first input terminal through said second switching means, said second switching means for isolating the second output terminal from the first battery in response to the voltage of the first battery falling to a second predetermined level.
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Abstract
A power switching circuit is described for supplying power to a radio pager which must be continuously powered from either a main or backup battery. The main battery voltage is monitored and at appropriate levels as its value falls, selected functions of the pager are eliminated and switch over to the backup battery is made to keep alive essential functions.
143 Citations
19 Claims
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1. A power switching circuit for selectively coupling an output terminal to a first or a second battery, the circuit comprising:
- a first input terminal for connection to the first battery;
a second input terminal for connection to the second battery;
an output terminal;
first switching means responsive to the voltage of the first battery for selectively switching the output terminal from the first to the second input terminal in response to the voltage of the first battery falling to a first predetermined level, said first switching means including a comparator coupled to compare the voltage of a primary one of said first or second batteries at the first input terminal with a first reference voltage;
second switching means controllable by said first switching means;
a second output terminal coupled to the first input terminal through said second switching means, said second switching means for isolating the second output terminal from the first battery in response to the voltage of the first battery falling to a second predetermined level. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
- a first input terminal for connection to the first battery;
- 15. An electronic circuit having a plurality of operating functions and including a power supply terminal connectible to a battery for supplying power to the electronic circuit and means responsive to the battery voltage at the power supply terminal for selecting predetermined ones of said operating functions in dependence upon the battery voltage level, said circuit including a microprocessor operable, under program control, at a plurality of bus frequencies, the bus frequency being selected in dependence upon the battery voltage level.
Specification