Charge control circuit for a battery charger
First Claim
1. A charge control circuit for a battery charger to selectively provide first and second control signals, the first control signal actuating the battery charger to operate at a first charge rate and the second control signal actuating it to operate at a second charge rate, said charge control circuit comprising;
- sensor means for sensing temperature of the battery being charged and providing an output indicative thereof;
a pair of sample-and-hold circuits each periodically operating to measure a value of the output of said sensor means and to hold the last measured value;
said sample-and-hold circuits operating alternately with respect to time so that one circuit is in a sampling operation while the other is in a holding operation;
a differential amplifier which subtracts the output of one of the sample-and-hold circuits from the output of the other circuit so as to obtain the difference between the instantaneous value being measured by the one circuit and the last value measured by the other circuit whereby differentiating the output of the sensor means with respect to time and providing uninterruptedly an instantaneous time derivative thereof indicative of a corresponding gradient of the battery temperature being sensed; and
judging means for comparing the time derivative with a predetermined threshold in order provide said first control signal when the time derivative is below the threshold and provide said second control signal when the time derivative exceeds the threshold.
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Accused Products
Abstract
A charge control circuit for a battery charger has a sensor circuit for sensing the temperature of a battery being charged and providing an output indicative thereof. A differentiator circuit converts the output of the sensor circuit into an instantaneous time derivative of thereof which is indicative of a corresponding temperature gradient of the battery. When the time derivative is determined by a judging circuit to be below a predetermined threshold indicative of the battery reaching its full charge state, the judging circuit responds to provide a first control signal, causing the battery charger to charge the battery at a high rate. Once the time derivative exceeds the threshold, the judging circuit provides a second control signal, causing the charger to terminate the high rate charge and change to a trickle charge or zero rate charge.
57 Citations
5 Claims
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1. A charge control circuit for a battery charger to selectively provide first and second control signals, the first control signal actuating the battery charger to operate at a first charge rate and the second control signal actuating it to operate at a second charge rate, said charge control circuit comprising;
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sensor means for sensing temperature of the battery being charged and providing an output indicative thereof; a pair of sample-and-hold circuits each periodically operating to measure a value of the output of said sensor means and to hold the last measured value; said sample-and-hold circuits operating alternately with respect to time so that one circuit is in a sampling operation while the other is in a holding operation; a differential amplifier which subtracts the output of one of the sample-and-hold circuits from the output of the other circuit so as to obtain the difference between the instantaneous value being measured by the one circuit and the last value measured by the other circuit whereby differentiating the output of the sensor means with respect to time and providing uninterruptedly an instantaneous time derivative thereof indicative of a corresponding gradient of the battery temperature being sensed; and judging means for comparing the time derivative with a predetermined threshold in order provide said first control signal when the time derivative is below the threshold and provide said second control signal when the time derivative exceeds the threshold. - View Dependent Claims (2, 3, 4, 5)
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Specification