Motorola Corporation

Seng P Xiong

Martin Hague Ramsden

Marc B Riley

A battery charging circuit having two levels of safety protection is provided. The circuit is said to have 'two levels' of safety because if any one component fails (either as a short circuit or as an open circuit) the remainder of the charging circuit ensures that a rechargeable battery coupled to the circuit will not be overcharged. The circuit includes both hardware and firmware protection components, with a microprocessor providing the firmware protection. Overvoltage protection, voltage regulation and current regulation are provided, along with a microprocessor capable of sensing a plurality of voltages across the circuit. The overvoltage protection, voltage regulator and current regulator each include safety actuation points. In parallel, the microprocessor may isolate a rechargeable battery from the cell if voltage and current minimums and maximums are exceeded. The microprocessor further is able to isolate the battery from the circuit if the power dissipation in the voltage regulator, the current regulator or the overall charging circuit is exceeded, provided the microprocessor has decremented current to a minimum level.

Charging circuit with two levels of safety

A circuit and method for charging a rechargeable cell is provided. The circuit includes a voltage regulator coupled serially between a power source and a rechargeable cell. The circuit further comprises a controller capable of both monitoring the power dissipation across the voltage regulator and altering the current flowing through the voltage regulator. When the power dissipation in the voltage regulator exceeds a predetermined threshold, the controller increases the current. Where the power source is a linear transformer, this increase of current will cause the transformer to become loaded. The loading causes the transformer output voltage to fall, thereby reducing the power dissipation in the voltage regulator below the predetermined threshold. If, however, the power dissipation does not fall below the predetermined threshold within a predetermined time following the increase of current, the controller will then reduce the current to a level low enough to cause the power dissipation in the voltage regulator to fall below the predetermined threshold. The circuit and method provide a way to rapidly charge batteries while ensuring that the voltage regulator is not subject to thermal compromise.

Charge boost battery charging and protection circuit

A charging circuit for regulating current to a plurality of batteries is provided. The regulation is performed by a single control signal that is optionally scaled by resistor dividers. Switches coupled to the resistor dividers allow a microprocessor to actuate a particular resistor divider, thereby scaling the current flowing through a corresponding battery. As such, a single control signal, like a pulse width modulated signal, may be used to cause different currents to flow to different batteries, thereby leaving other output pins of the microprocessor open for other functions.

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Dacula, GA, United States of America

Seng P Xiong