Lucent Technologies Inc.

Eugene Aranovich

Edwin A Muth

A reset device is disclosed which may be used in electrical devices such as portable telephones. The reset device includes a source, such as a rechargeable battery, which provides an input voltage and a threshold voltage. The reset device also has a comparator with a first input which receives the input voltage and a second input which receives the threshold voltage. A voltage changing device varies the threshold voltage in response to the output level of the comparator and a rate of increase of the input voltage. The voltage changing device includes a capacitor which delays an increase of the threshold voltage when the input voltage increases. Further, the voltage changing device includes a positive feedback resistor for increasing the threshold voltage when the output level increases. Thus, the positive feedback resistor allows switching the threshold voltage from a first threshold level to a second threshold level when the output level switches from a low level to a high level. The reset device further includes a regulator which regulates the input voltage to provide the threshold voltage. In addition, a switch is connected to an output of the comparator for providing a reset signal to a load. Illustratively, a controller receives the reset signal and resets the load, e.g., the portable phone. In response to the reset signal, the controller switches the portable phone between a dormant mode and an active mode. In addition, the controller allows trickle charging of the rechargeable battery in the dormant mode and rapid charging in the active mode.

Reset device

A charging circuit for charging a battery is disclosed. The charging circuit includes a power transistor having a charging terminal for connection to a charger, and a battery terminal for connection to the battery. Further, the charging circuit includes a shunt transistor connected between the battery and a control terminal of the power transistor. The shunt transistor prevents saturation of the power transistor when the charging source is disconnected from the charging terminal and the battery is in a charged state. This prevents leakage of current from the battery through the power transistor. The charging circuit further includes a diode connected between the charging terminal and a shunt control input of the shunt transistor. The diode, along with a voltage divider which divides the charging voltage, maintains the shunt transistor in a non-conductive state when the charger is connected to the charging terminal. When the charger is connected to the charging terminal, a controller turns on the power transistor through a control transistor.

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Middletown, NJ, United States of America

Eugene Aranovich