Scientific-atlanta, Inc.

Cisco Technology, Inc.

John D Anderson

Michael Patrick Duggan

Michael P Duggan

A threshold detection circuit includes, in one embodiment, a comparator having a first input connection for receiving a backup voltage from a backup power source, a second input connection for receiving a primary voltage from a primary power source, and an output connection for providing an output voltage; a first resistor and a first capacitor that are coupled in series between the first input connection and the output connection; and a second resistor that is coupled between the first input connection and the output connection, and that is coupled in parallel to the series of first resistor and the first capacitor.

Threshold detection in back-up power supply systems

A back-up power supply system includes, in one embodiment, a threshold detector circuit; a first switching circuit for enabling access to a back-up power source, the first switching circuit comprising at least a first transistor; and an inverting switch coupled between the first switching circuit and the threshold detector circuit, the inverting switch comprising an input and an output, the inverting switch configured to receive a signal at the input, invert the signal, and provide the inverted signal from the output to the first switching circuit, the inverting switch further comprising a delay circuit, the delay circuit configured to provide a substantially-immediate high-output during an off-to-on transition at the output of the inverting switch and a switching delay during an on-to-off transition at the output of the inverting switch, the inverting switch comprising a first resistive branch in parallel to a second branch comprising the delay circuit, the first resistive branch and the second branch connected to respective gates of the first and a second transistor, wherein the threshold detector circuit is configured to cause the first switching circuit to enable access to the back-up power source responsive to a voltage provided by a primary power source dropping below a predetermined threshold.

Back-up power supply systems

Systems and methods for switching to a back-up power supply are provided. One such system includes a threshold detector circuit; a first switching circuit for enabling access to a first power source, the first switching circuit comprising at least a first transistor; and a second switching circuit for enabling access to a second power source, the second switching circuit comprising at least a second transistor; wherein the threshold detector is configured to cause the second switching circuit to enable access to the second power supply responsive to a voltage provided by the first power supply dropping below a predetermined threshold.

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Lawrenceville, GA, United States of America

John D Anderson