Battery pack

• US 8,193,774 B2
• Filed: 06/25/2008
• Issued: 06/05/2012
• Est. Priority Date: 06/25/2007
• Status: Active Grant

• Current Assignee: Mitsumi Electric Co., Ltd. (MinebeaMitsumi Inc.)
• Original Assignee: Mitsumi Electric Co., Ltd. (MinebeaMitsumi Inc.)
• Inventors: Takeda, Takashi
• Primary Examiner(s): Tso, Edward
• Assistant Examiner(s): OMAR, AHMED H
• Application Number:
  US12/602,201
• Publication Number:
  US 20100201327A1
• Time in Patent Office: 1,441 Days
• Field of Search: 320/150, 320/134
• US Class Current: 320/134
• CPC Class Codes: H01M 10/052 Li-accumulators
• CPC Class Codes: H01M 10/441 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H01M 10/443 in response to temperature
• CPC Class Codes: H01M 2200/105 NTC
• CPC Class Codes: H01M 50/574 Devices or arrangements for the interruption of current
• CPC Class Codes: H01M 50/581 in response to temperature
• CPC Class Codes: H02J 7/00302 Overcharge protection
• CPC Class Codes: H02J 7/00306 Overdischarge protection
• CPC Class Codes: H02J 7/0031 using battery or load disconnect circuits H02J9/002 takes precedence
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

In a battery pack including a protection circuit, a series circuit of a thermistor and a resistor is disposed in a vicinity of a secondary battery and connected in parallel with the secondary battery. A connection detecting circuit is disposed to detect connection of a charging device to the battery pack. A comparator is disposed to compare a voltage of a junction point of the thermistor and the resistor with a reference voltage corresponding to a predetermined temperature. A gate circuit is disposed to activate an output signal of the comparator only when the connection of the charging device is detected. The protection circuit is arranged so that, when a temperature of the secondary battery exceeds the predetermined temperature, a switch element is turned off in accordance with the output signal of the comparator activated.

Claims

1. A battery pack comprising:

a protection circuit disposed in the battery pack to detect an overcharge, an overdischarge, and an overcurrent of a secondary battery and turn off a switch element disposed on a wiring line between the secondary battery and a load or a charging device;

a series circuit of a thermistor and a resistor, which is disposed in the battery pack in a vicinity of the secondary battery and connected in parallel with the secondary battery;

a connection detecting circuit disposed in the battery pack to detect connection between the charging device and the battery pack via a first terminal;

a comparator disposed in the protection circuit to compare a voltage of a junction point of the thermistor and the resistor with a reference voltage corresponding to a predetermined temperature; and

a gate circuit disposed in the protection circuit to activate an output signal of the comparator only when the connection between the charging device and the battery pack is detected by the connection detecting circuit,

wherein, when a temperature of the secondary battery exceeds the predetermined temperature, the protection circuit turns off the switch element in accordance with the output signal of the comparator activated by the gate circuit, so that the secondary battery is disconnected from the changing device by the turned-off switching element on the wiring line.

2. The battery pack according to claim 1, wherein the connection detecting circuit includes a resistor which is connected to the first terminal to pull up or down a potential of the first terminal where the charging device is to be connected to the battery pack, and wherein the potential of the first terminal is pulled down by the charging device when the charging device is connected to the battery pack.

3. The battery pack according to claim 1, wherein the thermistor is an NTC thermistor having a negative temperature coefficient.