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
39 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)
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16. 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 (17, 18)
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19. 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. - View Dependent Claims (20, 21, 22)
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23. 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;
shuntinng 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. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30)
the detection means includes a transmitting element of an opto-coupler and a voltage dependent resistive element having a threshold voltage not greater than a maximum operating voltage of the rechargeable element;
the shunting means includes a receiving element of said opto-coupler; and
if, during a charging operation, a current flowing in the voltage dependent resistive element reaches a predetermined level that would cause overcharging of the rechargeable element ot occur, the transmitting element is activated and causes the receiving element to shunt the rechargeable element, which in turn activates the protection means to limit current flowing in the rechargeable element.
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25. The protection system of claim 24, wherein the protection means comprises a fuse and the voltage dependent resistive element comprises a zener diode.
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26. The protection system of claim 24, wherein the protection means comprises a positive temperature coefficient (PTC) device and the voltage dependent resistive element comprises a zener diode.
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27. The protection system of claim 23, wherein:
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the detection means includes overvoltage detection means for detecting an overvoltage condition;
the shunting means includes a power MOSFET transistor activatable by the overvoltage detection means; and
when the overvoltage detection means detects that the voltage of the rechargeable element reaches a predetermined level, during a charging operation, the overvoltage detection means activates the power MOSFET transistor to shunt the rechargeable element, thereby activating the protection means, which limits current flowing in the rechargeable element.
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28. The protection system of claim 23, wherein:
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the detection means includes overvoltage detection means for detecting an overvoltage condition;
the shunting means includes a thyristor, which can be activated by the overvoltage detection means;
the protection means includes a fuse connected between a charger and the rechargeable element; and
when the overvoltage detection means detects that the voltage of the rechargeable element reaches a predetermined level during a charging operation, the overvoltage detection means activates the thyristor to shunt the rechargeable element, thereby causing the fuse to blow to disconnect the charger from the rechargeable element.
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29. The protection system of claim 28, wherein the protection means further includes a second fuse connected between the thyristor and the rechargeable element.
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30. The protection system of claim 28, wherein each of the fuses has a predetermined delay upon shunting the rechargeable element before it blows.
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31. 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 comprising:
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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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32. A protection circuit for use with a charger and a chargeable element, comprising a shunt regulator having a first and second terminals for coupling in parallel across the chargeable element, the shunt regulator comprising:
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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 an voltage clamping element coupled to the operational amplifier output, the clamping element effectively clamping the activation gate voltage.
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33. 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 including a transistor switch having a thermally-compensated voltage characteristic.
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34. 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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35. 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 shung 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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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 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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37. 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 in 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 fo the temperature dependent resistor, and a seond 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 (38, 39)
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Specification