Battery pack and method of controlling the same

• US 8,803,481 B2
• Filed: 01/06/2010
• Issued: 08/12/2014
• Est. Priority Date: 01/13/2009
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Tachikawa, Takashi, Hogari, Masaki, Watanabe, Kiyohiko
• Primary Examiner(s): Berhanu, Samuel
• Application Number:
  US12/683,214
• Publication Number:
  US 20100176764A1
• Time in Patent Office: 1,679 Days
• Field of Search: 320134-136
• US Class Current: 320/134
• CPC Class Codes: H01M 10/4207 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H02J 7/00304 Overcurrent protection
• CPC Class Codes: H02J 7/0031 using battery or load disconnect circuits H02J9/002 takes precedence
• CPC Class Codes: H02J 7/0063 with circuits adapted for supplying loads from the battery
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A battery pack for an electrically powered tool includes: one or plural secondary batteries connected in series and/or in parallel; a current detection resistor in a current path through which a charge/discharge current flows into each secondary battery; an N-channel charge control FET and an N-channel discharge control FET in the current path so as to control the charge/discharge current; and a controller detecting the charge/discharge current flowing in the current detection resistor and controlling the charge and discharge control FETs based on the detection result. A threshold value indicating an overcurrent detection current with respect to the charge/discharge current is set in advance, and the controller compares the charge/discharge current detected by the current detection resistor with the threshold value, and when the detected charge/discharge current is the threshold value or more, determines that an overcurrent state is detected and turns off the charge and discharge control FETs.

Claims

1. A battery pack comprising:

one or a plurality of secondary batteries;

a current detection resistor provided in a current path through which a current flows into each secondary battery;

a control FET provided in the current path so as to control the current; and

a controller detecting the current flowing in the current detection resistor and controlling the control FET on the basis of the detection result,

wherein

the controller compares the current detected by the current detection resistor with a threshold value indicating an overcurrent detection current with respect to the current, and when the detected current is equal to or larger than the threshold value, determines that an overcurrent state is detected,

the controller includes a timer which counts the time of the overcurrent state and has a delay time set with respect to the counted time such that when the overcurrent state is detected, the controller activates the timer to start to count the time of the overcurrent state, and performs control such that the control FET is not turned off until the counted time reaches the delay time,

even though the time counted by the timer exceeds the delay time, when the current is equal to or larger than the threshold value, the controller performs control such that the control FET is turned off,

before the time counted by the timer reaches the delay time, when the current becomes smaller than the threshold value, the controller ends time counting by the timer and performs control such that the control FET is not turned off, and

after the control FET is turned off, the controller measures a potential difference between each end of the current detection resistor and if the controller determines that there is no potential difference, the controller turns on the control FET.

2. The battery pack according to claim 1,

wherein the control FET includes a charge control FET and a discharge control FET are provided on a negative electrode side of each secondary battery.

3. The battery pack according to claim 1, wherein the current detection resistor is connected in series between the control FET and the secondary battery.

4. The battery pack according to claim 3, wherein each end of the current detection resistor is connected to the controller.

5. The battery pack according to claim 1, wherein the controller is configured to detect a potential difference resulting from both a discharge current and a charging current flowing through the current detection resistor.

6. A battery pack comprising:

one or a plurality of secondary batteries;

a current detection resistor provided in a current path through which a current flows into each secondary battery; and

a controller detecting the current flowing in the current detection resistor and outputting a control signal for a control FET, which is provided outside so as to control the current, on the basis of the detection result,

wherein a threshold value indicating an overcurrent detection current with respect to the current is set in advance,

the controller compares the current detected by the current detection resistor with the threshold value, and when the detected current is equal to or larger than the threshold value, determines that an overcurrent state is detected and outputs the control signal,

the controller includes a timer which counts the time of the overcurrent state and has a delay time set with respect to the counted time such that when the overcurrent state is detected, the controller activates the timer to start to count the time of the overcurrent state, and performs control such that the control FET is not turned off until the counted time reaches the delay time,

even though the time counted by the timer exceeds the delay time, when the current is equal to or larger than the threshold value, the controller performs control such that the control FET is turned off,

before the time counted by the timer reaches the delay time, when the current becomes smaller than the threshold value, the controller ends time counting by the timer and performs control such that the control FET is not turned off, and

after the control FET is turned off, the controller measures a potential difference between each end of the current detection resistor and if the controller determines that there is no potential difference, the controller turns on the control FET.

7. A method of controlling a battery pack, the method comprising:

detecting a current flowing in one or a plurality of secondary batteries by a current detection resistor provided in a current path through which the current flows;

comparing the detected current with a threshold value which indicates an overcurrent detection current set in advance with respect to the current, and when the detected current is equal to or larger than the threshold value, determining that an overcurrent state is detected and controlling a control FET which is provided in the current path so as to control the current;

counting the time of the overcurrent state with a timer that includes a delay time set with respect to the counted time;

performing control such that the control FET is not turned off until the counted time reaches the delay time when the overcurrent state is detected and activating the timer to start to count the time of the overcurrent state;

performing control such that the control FET is turned off, even though the time counted by the timer exceeds the delay time, when the current is equal to or larger than the threshold value;

ending counting by the timer and performing control such that the control FET is not turned off before the time counted by the timer reaches the delay time, when the current becomes smaller than the threshold value; and

after the control FET is turned off, measuring a potential difference between each end of the current detection resistor and if there is no potential difference, turning on the control FET.

8. A method of controlling a battery pack, the method

comprising:

detecting a current flowing in one or a plurality of secondary batteries by a current detection resistor provided in a current path through which the current flows; and

comparing the detected current with a threshold value which indicates an overcurrent detection current set in advance with respect to the current, and when the detected current is equal to or larger than the threshold value, determining that an overcurrent state is detected and outputting a control signal for turning off a control FET, which is provided outside so as to control the current;

counting the time of the overcurrent state with a timer that includes a delay time set with respect to the counted time;

performing control such that the control FET is not turned off until the counted time reaches the delay time when the overcurrent state is detected and activating the timer to start to count the time of the overcurrent state;

performing control such that the control FET is turned off, even though the time counted by the timer exceeds the delay time, when the current is equal to or larger than the threshold value;

ending counting by the timer and performing control such that the control FET is not turned off before the time counted by the timer reaches the delay time, when the current becomes smaller than the threshold value; and

after the control FET is turned off, measuring a potential difference between each end of the current detection resistor and if there is no potential difference, turning on the control FET.

9. A control integrated circuit configured to:

detect a current flowing in one or a plurality of secondary batteries by a current detection resistor provided in a current path through which the current flows; and

compare the detected current with a threshold value which indicates an overcurrent detection current set in advance with respect to the current, and when the detected current is equal to or larger than the threshold value, determining that an overcurrent state is detected and outputting a control signal for turning off a control FET, which is provided outside so as to control the current;

count the time of the overcurrent state with a timer that includes a delay time set with respect to the counted time;

perform control such that the control FET is not turned off until the counted time reaches the delay time when the overcurrent state is detected and activating the timer to start to count the time of the overcurrent state;

perform control such that the control FET is turned off, even though the time counted by the timer exceeds the delay time, when the current is equal to or larger than the threshold value;

end counting by the timer and performing control such that the control FET is not turned off before the time counted by the timer reaches the delay time, when the current becomes smaller than the threshold value; and

after the control FET is turned off, measure a potential difference across each end of the current detection resistor and if there is no potential difference, turning on the control FET.

10. A charging apparatus for a battery comprising:

a current detection resistor provided in a current path through which a current flows into one or a plurality of secondary batteries, the secondary batteries electrically connectable to the charging apparatus;

a controller detecting the current flowing in the current detection resistor and outputting a control signal for a control FET, which is provided so as to control the current, on the basis of

the detection result;

wherein the controller compares the current detected by the current detection resistor with a threshold value, and when the detected current is equal to or larger than the threshold value, determines that an overcurrent state is detected and turns off the control FET,

the controller includes a timer which counts the time of the overcurrent state and has a delay time set with respect to the counted time such that when the overcurrent state is detected, the controller activates the timer to start to count the time of the overcurrent state, and performs control such that the control FET is not turned off until the counted time reaches the delay time,

even though the time counted by the timer exceeds the delay time, when the current is equal to or larger than the threshold value, the controller performs control such that the control FET is turned off,

before the time counted by the timer reaches the delay time, when the current becomes smaller than the threshold value, the controller ends time counting by the timer and performs control such that the control FET is not turned off, and

after the control FET is turned off, the controller measures a potential difference across each end of the current detection resistor and if the controller determines that there is no potential difference, the controller determines that a normal current is flowing and that a state is released by turning on the control FET.

11. The charging apparatus according to claim 10, wherein the current detection resistor is connected in series between the control FET and the secondary battery.

12. The charging apparatus according to claim 11, wherein each end of the current detection resistor is connected to the controller.