Chemistry: electrical current producing apparatus – product – and – With control means responsive to battery condition sensing... – Temperature control
Reexamination Certificate
2001-05-23
2003-11-18
Gulakowski, Randy (Department: 1746)
Chemistry: electrical current producing apparatus, product, and
With control means responsive to battery condition sensing...
Temperature control
C429S061000, C320S154000, C320S160000, C320S162000
Reexamination Certificate
active
06649302
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to temperature sensing devices for use in secondary battery packs that include secondary batteries such as lithium ion batteries, and to the secondary battery packs incorporating such temperature sensing devices. More specifically, the present invention relates to an improved temperature sensing device for use in a secondary battery pack, which uses an NTC element (i.e., a negative temperature coefficient thermistor), and to the secondary battery pack incorporating such a temperature sensing device.
2. Description of the Related Art
Conventionally, secondary battery packs have been commonly used as power supplies for use in, for example, mobile communication apparatuses.
FIG. 6
is a block circuit diagram of a conventional secondary battery pack. Referring to
FIG. 6
, the conventional secondary battery pack includes a secondary battery
24
, a hot-side terminal
21
and a reference potential terminal
22
for recharging the secondary battery
24
, and a temperature sensing terminal
23
for sensing the temperature of the secondary battery
24
. The positive electrode of the secondary battery
24
is electrically connected to the hot-side terminal
21
and the negative electrode of the secondary battery
24
is electrically connected to the reference potential terminal
22
. The secondary battery pack also includes FETs
25
and
26
, and a controller IC
27
in order to control the operation of the secondary battery
24
.
The secondary battery pack further includes an NTC element
28
for sensing the temperature of the secondary battery
24
, which is connected between the temperature sensing terminal
23
and the reference potential terminal
22
. The NTC element
28
is disposed in proximity to the secondary battery
24
so as to allow for sensing of the temperature of the secondary battery
24
. The secondary battery
24
is recharged by a battery charger in accordance with an output from the temperature sensing terminal
23
, i.e., in accordance with the temperature of the secondary battery
24
.
With the ever decreasing size of electronic apparatuses which incorporate secondary battery packs, such as cellular phones, the secondary battery packs are also becoming smaller in size. Thus, in the secondary battery pack described above, the hot-side terminal
21
, the reference potential terminal
22
, and the temperature sensing terminal
23
are disposed in proximity to one another. As a result, for example, if the secondary battery pack is put into a clothes pocket when a metallic piece such as a hairpin happens to be in the clothes pocket, the hot-side terminal
21
and the temperature sensing terminal
23
are often short-circuited due to contact with the metallic piece. When such a short-circuit occurs, a terminal voltage of the secondary battery
24
is applied to the NTC element
28
. Thus, a short-circuit current flows into the NTC element
28
, which sometimes causes burnout of the NTC element
28
.
SUMMARY OF THE INVENTION
In order to overcome the problems described above, preferred embodiments of the present invention provide a temperature sensing device for use in a secondary battery pack, and the secondary battery pack incorporating the temperature sensing device, in which an NTC element incorporated therein is unsusceptible to short-circuiting and burnout, and reliability is thus greatly improved.
According to a preferred embodiment of the present invention, a temperature sensing device for sensing the temperature of a secondary battery in a secondary battery pack includes an NTC (negative temperature coefficient) element disposed at a predetermined position for sensing the temperature of the secondary battery, one end thereof being electrically connected to a temperature sensing terminal, and a current limiter element connected between the other end of the NTC element and a reference potential.
In the temperature sensing device, the current limiter element is preferably a PTC (positive temperature coefficient) element.
According to another preferred embodiment of the present invention, a secondary battery pack includes a secondary battery, a hot-side terminal and a reference potential terminal for recharging the secondary battery, a temperature sensing terminal for sensing the temperature of the secondary battery, an NTC element arranged to sense the temperature of the secondary battery, one end thereof being electrically connected to the temperature sensing terminal, and a current limiter element connected between the other end of the NTC element and the reference potential terminal.
In the secondary battery pack, the current limiter element is preferably a PTC element.
In the temperature sensing device and the secondary battery pack according to preferred embodiments of the present invention, because the current limiter element is connected between the NTC element and the reference potential, even if the temperature sensing terminal and the hot-side terminal of the secondary battery pack are short-circuited, the current limiter element prevents an overcurrent from continuously flowing into the NTC element, thereby preventing burnout of the NTC element.
Furthermore, when the PTC element is used as the current limiter element, when an application of voltage is stopped after the overcurrent is blocked by the PTC element, the resistance value of the NTC element returns to its initial value, allowing repeated protective operations in case of short circuits.
Other features, elements, characteristics and advantages of the present invention will become apparent from the following detailed description of preferred embodiments with reference to the attached drawings.
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patent: 5900717 (1999-05-01), Lee
patent: 6268714 (2001-07-01), Yang
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patent: 6524738 (2003-02-01), Lee et al.
patent: 7-226194 (1995-08-01), None
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Katsuki Takayo
Shimada Minoru
Gulakowski Randy
Keating & Bennett LLP
Murata Manufacturing Co. Ltd.
Scaltrito Donald V.
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