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US 6,310,497 B1Granted
Power supply loss detector method and apparatus
AssigneeAgere Systems Guardian Corp.
InventorMark S. Strauss
Life of this patent
Estimating the term…
Abstract
A power loss detector for generating a signal indicating the need to switch from a main power supply to an auxiliary power supply responsive to detecting that the main power supply has dropped below a predetermined threshold.
Claims27
A detector circuit for detecting when a power source fails, said circuit comprising:
- a resistor divider network coupled between said power source and a fixed voltage, said resistor divider network having a node at which a voltage is induced that is a fraction of a voltage of said power source;
- a first transistor having a pair of current flow terminals coupled between said power source and an output terminal of said circuit, said first transistor further having a control terminal coupled to said node of said resistor divider network such that the first transistor is turned on and off as a function of said power source voltage and, when said first transistor is on, said power source tends to drive said output terminal to a first logic level through said first transistor;
- and
- a second transistor coupled to said output terminal so as to drive said output terminal to a second logic level, said second transistor configured relative to said first transistor such that, when both said first and said second transistors are on, said output terminal is driven to about said voltage level of said primary power source through said first transistor;
- whereby, when said power source voltage drops below a predetermined level, said first transistor turns off, allowing said output level to switch from said first logic level to said second logic level.
2 more elements
A method of generating a power source switching signal when a primary voltage source in a circuit has dropped below a predetermined voltage so that an auxiliary power source should be used to power said circuit, said method comprising the steps of:
- dividing a primary voltage generated by a primary voltage source to generate a fractional voltage thereof;
- providing said primary voltage to an output terminal through a first transistor, said first transistor being controlled to be turned on or off by said fractional voltage, wherein the ratio of said fractional voltage to said primary voltage is selected such that said first transistor is turned off when said voltage of said primary voltage source drops below a predetermined voltage;
- providing a second voltage to said output terminal through a second transistor, said second transistor being controlled to be turned on or off by an auxiliary power source;
- said second transistor configured relative to said first transistor such that, when both said first and said second transistors are on, said output terminal is driven to about said primary voltage through said first transistor;
- whereby, when said primary voltage drops below said predetermined level, said first transistor turns off, allowing said output terminal to be driven to about said second voltage through said second transistor, the voltage at said output terminal comprising said power source switching signal.
2 more elements
Dependencies are inferred from the claim text.