Overcharge protection device and methods for lithium based rechargeable batteries
First Claim
1. A batter protection circuit comprising:
- a voltage regulator for connection in shunt across terminals of a rechargeable battery to prevent charging of the rechargeable battery over a predetermined voltage; and
a thermal element connected in series with the voltage regulator element and for connection to a supply of charging current, the thermal element being thermally coupled to the voltage regulator;
wherein the thermal element is responsive to heat coupled to it from the voltage regulator caused by dissipation of energy within the voltage regulator so as to open and disconnect the rechargeable battery from charging current when a voltage across the voltage regulator element exceeds a predetermined threshold.
2 Assignments
0 Petitions
Accused Products
Abstract
A protection circuit (100) and protection device (300) for protecting a rechargeable (lithium-based) battery cell or cells from overcharging. A voltage regulator element (110, 310) is connected in parallel with the battery cell or cells (5) and is thermally coupled to a thermal element (120, 322, 326) connected in series with the charging current supply. The voltage regulator element (110, 310) prevents overcharging of the battery (5) by shunting current away from the battery when a predetermined voltage across the battery is exceeded. Moreover, the thermal element (120, 322, 326) prevents failure of the voltage regulator element (110, 310) by open circuiting the current path when the heat dissipated by the voltage regulator element (110, 310), thermally coupled to the thermal element (120, 322, 326) causes the thermal element to enter a high resistance state. Additional protection may be provided by fuse bonds (332, 334) connecting the combination of the shunt voltage regulator 310 and the thermal elements (322, 326) to the charging current supply and to the battery (5).
116 Citations
23 Claims
-
1. A batter protection circuit comprising:
-
a voltage regulator for connection in shunt across terminals of a rechargeable battery to prevent charging of the rechargeable battery over a predetermined voltage; and
a thermal element connected in series with the voltage regulator element and for connection to a supply of charging current, the thermal element being thermally coupled to the voltage regulator;
wherein the thermal element is responsive to heat coupled to it from the voltage regulator caused by dissipation of energy within the voltage regulator so as to open and disconnect the rechargeable battery from charging current when a voltage across the voltage regulator element exceeds a predetermined threshold. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
-
-
13. A power hybrid protection device having an input terminal for connection to a supply of charging current and an output terminal for connection to a terminal of a rechargeable battery cell or cells to be protected, the protection device comprising:
-
a first thermal resistor connected in series with the input terminal; and
a shunt voltage regulator connected between the first thermal resistor and ground;
wherein the shunt voltage regulator is thermally coupled to the first thermal resistor and prevents charging of the battery over a predetermined voltage by causing the first thermal resistor to enter a high impedance state when the voltage across the output terminals exceeds a predetermined voltage. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22)
-
-
23. A method for protecting a rechargeable battery from overcharging comprising:
-
placing a voltage regulating element in parallel with the rechargeable battery to shunt current away from the rechargeable battery when voltage across the rechargeable battery exceeds a predetermined threshold; and
thermally coupling a temperature sensitive resistive element to the voltage regulating element and connecting the resistive element in series with a charging current supply so that the temperature sensitive resistive element enters a high impedance state effectively open circuiting a charging current path to the rechargeable battery in response to heat dissipation of the voltage regulating element caused by overcharging of the rechargeable battery.
-
Specification