US 7,068,012 B1Granted

Atmospheric explosive battery protection circuit having a robust protection system

AssigneeMotorola, Inc.

InventorsMichael D. Geren, Jennifer K. Collier, John E. Herrmann

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Abstract

A battery protection circuit is provided that includes current monitoring circuit. The current monitoring circuit senses current flowing from a rechargeable cell. When the current exceeds a maximum value, the current monitoring circuit actuates, whereby opening a transistor. The transistor has a resistor coupled in parallel. When the transistor opens, current is forced through the resistor coupled in parallel with the transistor, thereby limiting the current to a maximum value. When the voltage across the resistor exceeds a predetermined threshold, an overcurrent condition is simulated in the lithium ion protection IC. The overcurrent condition causes a disconnect switch to open, thereby disconnecting the cell(s) from the external terminals. The circuit additionally includes three current blocking elements coupled between charging terminals and the cells to ensure that fault conditions occurring within the charger do not adversely affect the performance of either the cells or a host electronic device.

Claims17

Dependent claims

A battery protection circuit, comprising:

a. at least one rechargeable cell;
b. a lithium ion protection IC coupled to the at least one rechargeable cell, the lithium ion protection IC comprising a voltage monitoring circuit and a current monitoring circuit;
c. at least one disconnect element coupled serially with the at least one rechargeable cell;
d. a current monitoring circuit;
e. a circuit for simulating an overcurrent condition within the lithium ion protection IC when the current monitoring circuit determines that the current flowing from the at least one rechargeable cell exceeds a predetermined current threshold;
f. a transistor coupled serially with the at least one rechargeable cell;
g. a resistor having an impedance less than 100 Ohms coupled in parallel with the transistor, wherein when the current flowing from the at least one rechargeable cell exceeds the predetermined current threshold, the current monitoring circuit causes the transistor to enter a high-impedance state;
h. a pair of current blocking elements coupled serially between a charger terminal and the at least one rechargeable cell, wherein the pair of current blocking elements are in a conducting state when the battery protection circuit is coupled to a charger, further wherein the pair of current blocking elements is in a non-conducting state when the battery protection circuit is not coupled to the charger;
and
i. at least a third current blocking element coupled serially between the charge terminal and the at least one rechargeable cell.

7 more elements

A battery protection circuit having an current monitoring circuit, wherein the current monitoring circuit determines when a current exceeds a predetermined threshold, comprising:

a. at least one rechargeable cell;
b. at least one lithium ion protection IC coupled to the at least one rechargeable cell;
c. at least one switch coupled serially with the at least one rechargeable cell;
d. at least one circuit for simulating an overcurrent condition within the lithium ion protection IC when the current monitoring circuit determines that the current exceeds the predetermined threshold;
e. a transistor coupled serially with the at least one rechargeable cell;
and
f. a resistor having an impedance less than 100 Ohms coupled in parallel with the transistor, wherein when the current exceeds a predetermined current threshold, the current monitoring circuit causes the transistor to enter a high-impedance state;
g. a resistor having an impedance less than 100 Ohms coupled in parallel with the transistor, wherein when the current flowing from the at least one rechargeable cell exceeds the predetermined current threshold, the current monitoring circuit causes the transistor to enter a high-impedance state;
h. a pair of current blocking elements coupled serially between a charger terminal and the at least one rechargeable cell, wherein the pair of current blocking elements are in a conducting state when the battery protection circuit is coupled to a charger, further wherein the pair of current blocking elements is in a non-conducting state when the battery protection circuit is not coupled to the charger;
and
i. at least a third current blocking element coupled serially between the charge terminal and the at least one rechargeable cell.

8 more elements

Dependencies are inferred from the claim text.