BATTERY PACK AND METHOD OF CONTROLLING THE SAME

• US 20100176764A1
• Filed: 01/06/2010
• Published: 07/15/2010
• 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, Watanabe, Kiyohiko, Hogari, Masaki
• Granted Patent: US 8,803,481 B2
• Time in Patent Office: Days
• US Class Current: 320/118
• 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: H02J 7/00714 in response to battery charging or discharging current
• 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 for an electrically powered tool, the battery pack comprising:

one or a plurality of secondary batteries connected in series and/or in parallel;

a current detection resistor provided 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 provided 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 control FET and the discharge control FET on the basis of the detection result,

wherein 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 equal to or larger than the threshold value, determines that an overcurrent state is detected and turns off the charge control FET and the discharge control FET.

2. The battery pack according to claim 1,

wherein the controller has a timer which counts the time of the overcurrent state and has a delay time set with respect to the counted time, and

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 charge control FET and the discharge control FET are not turned off until the counted time reaches the delay time.

3. The battery pack according to claim 2,

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

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

4. The battery pack according to claim 1,

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

5. A battery pack for an electrically powered tool, the battery pack comprising:

one or a plurality of secondary batteries connected in series and/or in parallel;

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

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

wherein 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 equal to or larger than the threshold value, determines that an overcurrent state is detected and outputs the control signal.

6. The battery pack according to claim 5,

wherein the controller has a timer which counts the time of the overcurrent state and has a delay time set with respect to the counted time,

when the overcurrent state is detected, the controller activates the timer to start to count the time of the overcurrent state, and outputs no control signal until the counted time reaches the delay time.

7. The battery pack according to claim 6,

wherein, even though the time counted by the timer exceeds the delay time, when the charge/discharge current is equal to or larger than the threshold value, the controller outputs the control signal, and

before the time counted by the timer reaches the delay time, when the charge/discharge current becomes smaller than the threshold value, the controller ends time counting by the timer and outputs no control signal.

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

detecting a charge/discharge current flowing in one or a plurality of secondary batteries connected in series or in parallel by a current detection resistor provided in a current path through which the charge/discharge current flows; and

comparing the detected charge/discharge current with a threshold value which indicates an overcurrent detection current set in advance with respect to the charge/discharge current, and when the detected charge/discharge current is equal to or larger than the threshold value, determining that an overcurrent state is detected and turning off an N-channel charge control FET and an N-channel discharge control FET which are provided in the current path so as to control the charge/discharge current.

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

detecting a charge/discharge current flowing in one or a plurality of secondary batteries connected in series or in parallel by a current detection resistor provided in a current path through which the charge/discharge current flows; and

comparing the detected charge/discharge current with a threshold value which indicates an overcurrent detection current set in advance with respect to the charge/discharge current, and when the detected charge/discharge 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 charge control FET and a discharge control FET, which are provided outside so as to control the charge/discharge current.