Protection circuit for a battery cell
First Claim
1. A cell protection circuit, comprising:
- a transistor coupled to said cell; and
a current bypass device coupled to said transistor and said cell;
wherein said transistor limits the current that can flow through said cell when the voltage across said cell falls to a predetermined minimum level.
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Accused Products
Abstract
A protection circuit couples to and protects a battery cell. The protection circuit generally limits the current that can flow through cell when the voltage across the cell falls to a predetermined minimum threshold, such as might occur if the cell is passivated, fails in service, or is reaching the end of its useful life. The protection circuit preferably includes a transistor, which couples in series with the cell and limits the current therethrough. By limiting the current through the cell when its voltage reaches a minimum threshold, the voltage on the cell will not fall below the minimum safe level. A bypass means (e.g., a diode) also is included to conduct current around the cell when its current has been limited by the transistor.
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Citations
41 Claims
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1. A cell protection circuit, comprising:
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a transistor coupled to said cell; and
a current bypass device coupled to said transistor and said cell;
wherein said transistor limits the current that can flow through said cell when the voltage across said cell falls to a predetermined minimum level. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A protection circuit for a cell, comprising:
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a means for limiting current through said cell when the voltage across said cell reaches a predetermined threshold; and
a means for conducting current around said cell when the voltage across said cell reaches the predetermined threshold. - View Dependent Claims (17)
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18. A method of protecting a cell, comprising:
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(a) limiting the current said cell when the voltage across said cell falls to a minimum predetermined level; and
(b) when limiting the current, permitting current to conduct through a bypass device coupled in parallel with said cell. - View Dependent Claims (19)
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20. The method of protecting a cell further including providing a time delay to the voltage across said transistor.
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21. A battery, comprising:
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a plurality of cells connected in series; and
a separate protection unit coupled to each cell, each protection unit protecting its associated cell and comprising;
a transistor coupled to said associated cell; and
a current bypass device coupled to said transistor and said associated cell;
wherein said transistor limits the current that can flow through said associated cell when the voltage across said associated cell falls to a predetermined minimum level. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35)
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36. A battery cell protection circuit, comprising:
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a current limiter capable of being coupled to a battery cell; and
a bypass device coupled in parallel with the current limiter and cell;
wherein the current limiter functions to limit current to the cell when the cell voltage reaches a predetermined threshold. - View Dependent Claims (37, 38, 39, 40, 41)
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Specification