Devices and methods for protection of rechargeable elements
First Claim
1. A protection circuit for use with a charger and a chargeable element, comprising:
- a shunt regulator having first and second terminals for coupling in parallel across the chargeable element, the shunt regulator having a threshold ON voltage; and
a first variable resistor thermally and electrically coupled to the shunt regulator, the first variable resistor having a first terminal for coupling to the charger in series and a second terminal for coupling to the chargeable element in series, wherein the first variable resistor limits current flowing through the shunt regulator during an overvoltage or overcurrent condition before the current reaches a level sufficient to cause the shunt regulator to fail.
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Accused Products
Abstract
A protection circuit for use with a charger and a chargeable element, such as a rechargeable lithium ion battery, comprises a shunt regulator having a threshold ON voltage coupled in parallel across the chargeable element, and a temperature-dependent resistor, e.g., a positive temperature coefficient device, coupled in series between the charger and the chargeable element. The temperature dependent resistor is thermally and electrically coupled to the shunt regulator, wherein the first variable resistor limits current flowing through the shunt regulator if the current reaches a predetermined level less than that which would cause failure of the regulator, due to ohmic heating of the regulator.
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Citations
44 Claims
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1. A protection circuit for use with a charger and a chargeable element, comprising:
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a shunt regulator having first and second terminals for coupling in parallel across the chargeable element, the shunt regulator having a threshold ON voltage; and
a first variable resistor thermally and electrically coupled to the shunt regulator, the first variable resistor having a first terminal for coupling to the charger in series and a second terminal for coupling to the chargeable element in series, wherein the first variable resistor limits current flowing through the shunt regulator during an overvoltage or overcurrent condition before the current reaches a level sufficient to cause the shunt regulator to fail. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. In combination, a protection circuit and a chargeable element, comprising:
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a voltage regulator coupled in parallel to the chargeable element, the voltage regulator having a threshold ON voltage; and
a variable resistor coupled in series to the chargeable element and electrically and thermally coupled to the voltage regulator, wherein the variable resistor limits current flowing through the voltage regulator during an overvoltage or overcurrent condition before the current reaches a level sufficient to cause the voltage regulator to fail. - View Dependent Claims (22, 23, 25, 26, 27, 29, 30, 31, 32, 33, 34, 35)
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24. A protection circuit for use with a chargeable element, comprising:
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a smart circuit;
a variable current-limiting element coupled in series to the smart circuit; and
a voltage regulator having first and second terminals for coupling to the chargeable element, the voltage regulator having a selected threshold ON voltage.
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28. A protection system for use with a chargeable element, comprising:
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detection means for detecting an overcharging condition of the rechargeable element;
shunting means, responsive to said detection means, for shunting the rechargeable element when the overcharging condition occurs; and
protection means, responsive to the shunting means, for limiting current flowing in the rechargeable element when the shunting means shunts the rechargeable element.
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36. A protection circuit for use with a charger and a chargeable element, comprising:
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a shunt regulator having first and second terminals for coupling in parallel across the chargeable element, the shunt regulator comprising a transistor switch having a threshold ON voltage, and control circuitry configured to activate the transistor switch if the voltage across the chargeable element reaches the threshold ON voltage, the control circuitry including first and second voltage detection circuits, the first voltage detection circuit being relatively low leakage and the second voltage detection circuit being relatively precise, wherein the first voltage detection circuit is configured to activate the second voltage detection circuit if the voltage across the chargeable element approaches the threshold ON voltage, and wherein the second voltage detection circuit is configured to activate the transistor switch if the voltage across the chargeable element reaches the threshold ON voltage.
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37. A protection circuit for use with a charger and a chargeable element, comprising:
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a shunt regulator having first and second terminals for coupling in parallel across the chargeable element, the shunt regulator comprising a transistor switch having a threshold ON voltage, and control circuitry configured to activate the transistor switch if the voltage across the chargeable element reaches the threshold ON voltage, the control circuitry including an operational amplifier having an output coupled to an activation gate of the transistor switch, and a voltage clamping element coupled to the operational amplifier output, the clamping element effectively clamping the activation gate voltage.
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38. A protection circuit for use with a charger and a chargeable element, comprising:
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a shunt regulator having first and second terminals for coupling in parallel across the chargeable element, the shunt regulator comprising a transistor switch having a thermally-compensated voltage characteristic.
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39. A protection circuit for use with a charger and a chargeable element, comprising:
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an overvoltage shunt regulator having first and second terminals for coupling in parallel across the chargeable element, the shunt regulator comprising a first transistor switch having a threshold ON voltage approximating a selected maximum operating voltage of the chargeable element; and
an undervoltage protection circuit having first and second terminals configured for coupling in series between the charger and the chargeable element, the undervoltage protection circuit comprising a second transistor switch having a threshold ON voltage approximating a selected minimum operating voltage of the chargeable element.
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40. A protection circuit for use with a charger and a chargeable element, comprising:
an overvoltage shunt regulator having first and second terminals for coupling in parallel across the chargeable element, the shunt regulator comprising a MOSFET switch having a threshold ON voltage approximating a selected maximum operating voltage of the chargeable element, and a relatively high resistance, reverse-current body diode.
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41. A protection circuit for use with a charger and a chargeable element, comprising:
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a shunt regulator having first and second terminals for coupling in parallel across the chargeable element, the shunt regulator having a threshold ON voltage;
a first positive temperature coefficient (PTC) device thermally and electrically coupled to the shunt regulator, the first PTC device having a first terminal for coupling to the charger in series and a second terminal for coupling to the chargeable element in series; and
a second PTC device coupled in series with the shunt regulator, wherein the first PTC device switches from a relatively low resistance to a relatively high resistance when heated to a first transition temperature, and wherein the second PTC device switches from a relatively low resistance to a relatively high resistance when heated to a second transition temperature higher than the first transition temperature.
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42. In combination, a protection circuit and a battery, the battery having a positive terminal and a negative terminal, the protection circuit comprising:
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a transistor switch coupled in series with the battery, such that, when the transistor switch is ON, the battery will discharge through a load;
a temperature-dependent resistor thermally coupled to the transistor switch, and having first and second terminals, the first terminal coupled to the positive battery terminal; and
a fixed resistor having a first terminal coupled to the second terminal of the temperature dependent resistor, and a second terminal coupled to the negative battery terminal, the respective temperature dependent resistor and fixed resistor thereby coupled in series with each other and in parallel with the battery, wherein the transistor switch has an activation gate coupled in a divider configuration to the second terminal of the temperature dependent resistor and first terminal of the fixed resistor. - View Dependent Claims (43, 44)
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Specification