US5602460A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Overcharge current protection circuit and battery pack using same
Assignee: Google Technology Holdings LLC
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Filing: 1995-04-28
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Granted: 1997-02-11
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Expires: 2015-04-28
Abstract
Abstract A battery pack (62) comprises cells (74), and is charged by a charger (64) providing a current level. The charger (64) is a typical nickel-cadmium battery charger providing a first charge current level in excess of an optimum charge current level. The battery pack (62) further comprises a thermal sensing element (76) and an overcurrent charge protection circuit having an overcurrent switch (78), current sense circuit (80), comparator circuit (82), and temperature signal switch (84). If the current level through the cells (74) exceeds the optimum charge current level, the current sense circuit (80) provides a signal to comparator circuit (82) which actuates the temperature signal switch (84), simulating a hot battery pack. The charger (64) then switches to a second charge current level which does not exceed the optimum charge current level. If the charger (64) does not change current levels, a switch delay (86), after a brief period, accumulates enough voltage to actuate a driver switch (88) which opens the overcurrent switch (78), disconnecting the cells (74) from the charger (64).
Inventors
- 👤 Jose M. Fernandez
- 👤 Vernon Meadows
- 👤 Erika D. Mack
- 👤 Iilonga P. Thandiwe
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 01:15
CPC Classifications
H; H02; H02J; H02J7/00; H02J7/60; H02J7/663; H02J7/61; H02J7/64
Claims Analysis
Total Claims: 28
Claim 1
Independent Claim
155 words
A battery pack for use with a charger having a charge current level and providing a first charge current level in excess of an optimum charge current level and switchable to a second charge current level not exceeding said optimum charge current level upon indication of said battery pack reaching an undesirable temperature, said battery pack having a positive and a negative charging terminal, said battery pack comprising: at least one battery cell through which charge current flows; a temperature sensing element for sensing the temperature of said at least one battery cell and providing a signal to said charger indicating said temperature; temperature signal switch means coupled parallel with said temperature sensing element for simulating an undesirable battery temperature to said charger when actuated; and temperature signal switch control means for sensing said charge current level and actuating said temperature signal switch means when said charge current level exceeds an optimum charge current level.
Claim 2
Dependent Claim
155 words
A battery pack for use with a charger having a charge current level and providing a first charge current level in excess of an optimum charge current level and switchable to a second charge current level not exceeding said optimum charge current level upon indication of said battery pack reaching an undesirable temperature, said battery pack having a positive and a negative charging terminal, said battery pack comprising: at least one battery cell through which charge current flows; a temperature sensing element for sensing the temperature of said at least one battery cell and providing a signal to said charger indicating said temperature; temperature signal switch means coupled parallel with said temperature sensing element for simulating an undesirable battery temperature to said charger when actuated; and temperature signal switch control means for sensing said charge current level and actuating said temperature signal switch means when said charge current level exceeds an optimum charge current level.
Claim 3
Dependent Claim
61 words
A battery pack as in claim 1, further comprising an overcurrent switch coupled in series with said at least one battery cell for disconnecting said at least one battery cell from said charger in response to said charger continuing to provide a charge current level in excess of said optimum charge current level after said temperature signal switch means is actuated.
Claim 4
Dependent Claim
29 words
A battery pack as in claim 2, wherein said overcurrent switch is responsive to a driver switch coupled to said temperature signal switch control means through a switch delay.
Claim 5
Dependent Claim
14 words
A battery pack as in claim 3 wherein said overcurrent switch comprises a MOSFET.
Claim 6
Dependent Claim
19 words
A battery pack as in claim 3 wherein said switch delay comprises a series resistor and a shunt capacitor.
Claim 7
Dependent Claim
32 words
A battery pack as in claim 3 wherein said driver switch comprises a MOSFET and a pull up resistor coupled in series between said positive charging terminal and said negative charging terminal.
Claim 8
Dependent Claim
91 words
A battery pack as in claim 1, wherein said temperature signal switch control means comprises: a current sense circuit for providing a signal proportional to said charge current level through said at least one battery cell as an output signal; and a comparator circuit for comparing said signal provided by said current sense circuit with a reference voltage, said comparator circuit having an output coupled to said temperature signal switch means and providing an actuating signal if said signal provided by said current sense circuit is greater than said reference voltage.
Claim 9
Dependent Claim
71 words
A battery pack as in claim 7 wherein said current sense circuit comprises: a current sense resistor connected in series with said at least one battery cell for producing a low level voltage signal proportional to said charge current level through said at least one battery cell; and an amplifier for amplifying said low level voltage signal by a preselected gain factor thereby providing an amplified signal to said comparator circuit.
Claim 10
Dependent Claim
18 words
A battery pack as in claim 8 wherein said amplifier is an op-amp connected in a non-inverting configuration.
Claim 11
Dependent Claim
53 words
A battery pack as in claim 7 wherein said comparator circuit comprises: a comparator having an inverting input, non-inverting input, and a comparator output, said non-inverting input receiving said output signal of said current sense circuit; and a voltage reference connected between said inverting input of said comparator and said negative charging terminal.
Claim 12
Dependent Claim
16 words
A battery pack as in claim 1 wherein said temperature sensing element is a NTC thermistor.
Claim 13
Dependent Claim
16 words
A battery pack as in claim 1 wherein said temperature signal switch means comprises a MOSFET.
Claim 14
Dependent Claim
25 words
A battery pack as in claim 12 wherein said temperature signal switch means further comprises a current limiting resistor coupled in series with said MOSFET.
Claim 15
Dependent Claim
156 words
An overcharge current protection circuit for a battery pack having at least one battery cell for use with a charger having a charge current level and providing a first charge current level in excess of an optimum charge current level and switchable to a second charge current level not exceeding said optimum charge current level upon indication of said battery pack reaching an undesirable temperature, said battery pack having a positive and a negative charging terminal, said circuit comprising: a temperature sensing element for sensing the temperature of said at least one battery cell and providing a signal to said charger indicating said temperature; temperature signal switch means coupled parallel with said temperature sensing element for simulating an undesirable battery temperature to said charger when actuated; and temperature signal switch control means for sensing said charge current level and actuating said temperature signal switch means when said charge current level exceeds an optimum charge current level.
Claim 16
Dependent Claim
156 words
An overcharge current protection circuit for a battery pack having at least one battery cell for use with a charger having a charge current level and providing a first charge current level in excess of an optimum charge current level and switchable to a second charge current level not exceeding said optimum charge current level upon indication of said battery pack reaching an undesirable temperature, said battery pack having a positive and a negative charging terminal, said circuit comprising: a temperature sensing element for sensing the temperature of said at least one battery cell and providing a signal to said charger indicating said temperature; temperature signal switch means coupled parallel with said temperature sensing element for simulating an undesirable battery temperature to said charger when actuated; and temperature signal switch control means for sensing said charge current level and actuating said temperature signal switch means when said charge current level exceeds an optimum charge current level.
Claim 17
Dependent Claim
61 words
A battery pack as in claim 14, further comprising an overcurrent switch coupled in series with said at least one battery cell for disconnecting said at least one battery cell from said charger in response to said charger continuing to provide a charge current level in excess of said optimum charge current level after said temperature signal switch means is actuated.
Claim 18
Dependent Claim
29 words
A battery pack as in claim 15, wherein said overcurrent switch is responsive to a driver switch coupled to said temperature signal switch control means through a switch delay.
Claim 19
Dependent Claim
14 words
A battery pack as in claim 16 wherein said overcurrent switch comprises a MOSFET.
Claim 20
Dependent Claim
19 words
A battery pack as in claim 16 wherein said switch delay comprises a series resistor and a shunt capacitor.
Claim 21
Dependent Claim
32 words
A battery pack as in claim 16 wherein said driver switch comprises a MOSFET and a pull up resistor coupled in series between said positive charging terminal and said negative charging terminal.
Claim 22
Dependent Claim
91 words
A battery pack as in claim 14, wherein said temperature signal switch control means comprises: a current sense circuit for providing a signal proportional to said charge current level through said at least one battery cell as an output signal; and a comparator circuit for comparing said signal provided by said current sense circuit with a reference voltage, said comparator circuit having an output coupled to said temperature signal switch means and providing an actuating signal if said signal provided by said current sense circuit is greater than said reference voltage.
Claim 23
Dependent Claim
71 words
A battery pack as in claim 20 wherein said current sense circuit comprises: a current sense resistor connected in series with said at least one battery cell for producing a low level voltage signal proportional to said charge current level through said at least one battery cell; and an amplifier for amplifying said low level voltage signal by a preselected gain factor thereby providing an amplified signal to said comparator circuit.
Claim 24
Dependent Claim
18 words
A battery pack as in claim 21 wherein said amplifier is an op-amp connected in a non-inverting configuration.
Claim 25
Dependent Claim
53 words
A battery pack as in claim 20 wherein said comparator circuit comprises: a comparator having an inverting input, non-inverting input, and a comparator output, said non-inverting input receiving said output signal of said current sense circuit; and a voltage reference connected between said inverting input of said comparator and said negative charging terminal.
Claim 26
Dependent Claim
16 words
A battery pack as in claim 14 wherein said temperature sensing element is a NTC thermistor.
Claim 27
Dependent Claim
16 words
A battery pack as in claim 14 wherein said temperature signal switch means comprises a MOSFET.
Claim 28
Dependent Claim
25 words
A battery pack as in claim 25 wherein said temperature signal switch means further comprises a current limiting resistor coupled in series with said MOSFET.
References Cited (Backward Citations)
US5518832A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2000-02-11 | 2000-08-12 | 2001-02-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2004-02-11 | 2004-08-12 | 2005-02-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2008-02-11 | 2008-08-12 | 2009-02-11 | $7700.00 | Window Closed / Lapsed |