Unitrode Corporation

Texas Instruments Corporation

Winthrop H McClure

Robert A Mammano

Larry J Wofford

Burt Lee Price

John A O'Connor

Roman Korsunsky

A battery protection circuit includes a moisture detection circuit, a temperature sensing circuit, and a high-temperature battery discharge circuit. The moisture detection circuit includes a pair of conductive traces closely spaced on a substrate such that a resistive path is formed between the traces when moisture forms on the substrate. The traces are connected between the positive battery terminal and a pull-down current source. When moisture forms on the substrate, pull-up current flows between the traces, and a resulting voltage change on one of the traces is detected by circuit element such as a logic inverter. The temperature sensing circuit includes a voltage reference circuit that generates a proportional-to-temperature voltage and temperature-independent voltage reference signals corresponding to various predetermined temperatures. A measuring circuit operates during a sampling interval to compare each temperature-dependent voltage to the proportional-to-temperature voltage and to store the result of each comparison until a subsequent temperature sampling interval. The measuring circuit includes multiplexing circuitry used to sequentially select each temperature-dependent voltage during a sampling interval. The high-temperature discharge circuit connects a discharge load across the battery when the voltage of the battery is above a high voltage threshold and the temperature of the battery is above the high temperature threshold. When no external charger is active, the discharge current flowing through this load works to reduce battery voltage. helping to prolong battery life.

Battery protector

A battery charger/monitor circuit for charging and/or monitoring a plurality of series-connected cells, including a voltage sensor for sensing the voltage across each of the cells to provide a high cell voltage signal proportional to the highest voltage across any of the cells and a low cell voltage signal proportional to the lowest voltage across any of the cells. The circuit is operable in a monitor mode or a charge mode. In the monitor mode, the cells are disconnected from a load if the low cell voltage signal decreases to a first predetermined level. The circuit includes a controller which provides a control signal in response to the high cell voltage signal, the low cell voltage signal and a current sense signal, for controlling the charging of the cells. In the charge mode, the cells receive a constant charge current until the high cell voltage signal reaches a second predetermined level, after which the voltage across the cell charged to the highest voltage is held substantially constant, causing the charge current to be reduced.

Voltage sensor for detecting cell voltages

A battery protector for providing overvoltage and undervoltage protection to one or more series-connected cells. The battery protector includes a voltage detection and comparison circuit, providing an overvoltage signal indicative of whether the voltage across any of the cells is greater than an overvoltage threshold level and an undervoltage signal indicative of whether the voltage across any of the cells is less than an undervoltage threshold level, and a switch connected in series with the current path between the cells and a charger and/or load. In one embodiment, the switch is a four-terminal FET and a bias control circuit is provided for selectively connecting the body region of the FET to ensure that current does not flow through the parasitic FET diodes. A second control circuit responsive to the overvoltage and undervoltage signals controls conduction of the switch, causing the switch to close if any of the following conditions occur: (1) the overvoltage and undervoltage signals do not indicate an overvoltage or undervoltage condition, respectively; (2) the overvoltage signal indicates an overvoltage condition, but the cells are attempting to discharge; or (3) the undervoltage signal indicates an undervoltage condition, but the charger is attempting to charge the cells.

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Londonderry, NH, United States of America

Winthrop H McClure