Battery charging method and apparatus
First Claim
1. A battery charging circuit comprising a sense circuit that includes a time-averaging amplifier circuit to accurately sense a charging current of a battery under charge, said time-averaging amplifier circuit comprising a polarity-switched amplifier that periodically switches amplifier signal polarities to null amplifier offset errors from the sensed charging current.
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Accused Products
Abstract
A battery charging circuit senses charging current using a sense circuit that includes a time-averaging amplifier circuit that nulls amplifier offset errors from the sensed current signal. With such offset correction, the sense circuit provides accurate current sensing over a wide dynamic range of charging current and thus may be used for low and high charging currents, and accurate detection of trickle and end-of-charge currents. The substantial elimination of amplifier-offset errors from charging current sensing permits use of a single sense resistor over a wide range of charging currents. Such accurate current detection supports zero-current regulation of the battery, which allows the battery to remain connected to the charging circuit even after reaching its end-of-charge condition. The battery charging circuit further may include digital switchover circuitry, which reduces charging control discontinuities by allowing both current and voltage feedback loops to drive the same regulation control circuit.
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Citations
35 Claims
- 1. A battery charging circuit comprising a sense circuit that includes a time-averaging amplifier circuit to accurately sense a charging current of a battery under charge, said time-averaging amplifier circuit comprising a polarity-switched amplifier that periodically switches amplifier signal polarities to null amplifier offset errors from the sensed charging current.
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16. A battery charging circuit comprising:
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a sense circuit to generate a sense signal responsive to sensing a charging current associated with a battery under charge; and
a charging control circuit to control charging of the battery responsive to the sense signal;
said sense circuit including a time-averaging amplifier circuit to generate the sense signal and to substantially null amplifier offset errors from the sense signal. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
an amplifier to generate a first signal proportional to a differential voltage induced by the charging current; and
polarity-reversing input and output switches to selectively reverse input and output signal connections of the amplifier;
said polarity-reversing input and output switches responsive to a periodic polarity switching signal to alternate between reversed and non-reversed signal connections.
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26. The battery charging circuit of claim 25, wherein the time-averaging amplifier circuit further comprises a pass transistor that sources current into a program resistor responsive to the first signal to thereby generate the sense signal in proportion to the charging current.
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27. The battery charging circuit of claim 25, further comprising a switching clock to generate the polarity switching signal.
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28. A method of accurately sensing a charging current into a battery comprising:
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using an amplifier to generate a sense signal proportional to the charging current;
periodically reversing signal polarities of the amplifier to null amplifier offset errors from the sense signal and thereby improve sense signal accuracy. - View Dependent Claims (29, 30, 31, 32)
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33. A method of accurately sensing a charging current into a battery comprising:
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generating a sense signal proportional to the charging current using a time-averaging amplifier circuit that nulls offset errors in the sense signal;
controlling a charging circuit based on the sense signal to maintain the charging current at a desired magnitude if a charging voltage of the battery remains below a defined voltage threshold; and
controlling the charging circuit based on the charging voltage to maintain a constant charging voltage on the battery if the charging voltage equals the defined voltage threshold. - View Dependent Claims (34, 35)
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Specification