Battery pack, battery protection processing apparatus and control method thereof

• US 7,579,811 B2
• Filed: 11/12/2004
• Issued: 08/25/2009
• Est. Priority Date: 11/14/2003
• Status: Active Grant

• Current Assignee: Maxim Japan Co., Ltd. (Analog Devices, Inc.), Sony Corporation (Sony Group Corp.)
• Original Assignee: Maxim Japan Co., Ltd. (Analog Devices, Inc.), Sony Corporation (Sony Group Corp.)
• Inventors: Koide, Toshihiro, Tsuchiya, Yukio, Nagashima, Osamu, Sato, Hideyuki, Nakamichi, Ryuji
• Primary Examiner(s): Ullah; Akm E
• Assistant Examiner(s): WILLIAMS, ARUN C
• Application Number:
  US10/987,927
• Publication Number:
  US 20050134230A1
• Time in Patent Office: 1,747 Days
• Field of Search: 320/132, 320/134, 320/136, 320/153, 320/159, 320/162, 320/163, 320/164, 324/427, 324/432, 324/433, 702/63, 361/93.1
• US Class Current: 320/134
• CPC Class Codes: H01M 10/4264 with capacitors
• CPC Class Codes: H01M 10/443 in response to temperature
• CPC Class Codes: H01M 10/448 End of discharge regulating measures
• CPC Class Codes: H01M 10/48 Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte constructional details of current conducting connections for detecting conditions inside cells or batteries, e.g. details of voltage sensing terminals, H01M50/569
• CPC Class Codes: H01M 10/482 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H01M 10/486 for measuring temperature
• CPC Class Codes: H02J 7/0031 using battery or load disconnect circuits H02J9/002 takes precedence
• CPC Class Codes: H02J 7/0036 using connection detecting circuits H02J7/0034 takes precedence
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

It is aimed at stably implementing a protection function of a secondary battery mainly under software control and providing a battery pack characterized by a reduced circuit installation area, parts costs, and power consumption. An AD converter outputs a voltage value between a positive electrode and a negative electrode of a secondary battery. Based on the voltage value, a microcontroller determines a state of the secondary battery out of overcharge, normal operation, and over-discharge states. According to the determined state, the microcontroller controls operations of a discharge current cutoff means and a charge current cutoff means via a FET driver. When it is determined that the secondary battery is placed in an overcurrent state based on the charge and discharge current size of the secondary battery, an overcurrent detection circuit enables the discharge current cutoff means to be a cutoff state in preference to control by the microcontroller.

Claims

1. A battery pack which uses a software control to implement a secondary battery protection function, the battery pack comprising:

discharge current cutoff means for selectively cutting off a discharge current in the secondary battery;

charge current cutoff means for selectively cutting off a charge current in the secondary battery;

voltage detection means for digitizing and outputting a voltage between a positive electrode and a negative electrode of the secondary battery;

protection process means for, based on at least an output voltage value from the voltage detection means, determining a state of the secondary battery out of overcharge, normal operation, and over-discharge states and, according to a determined state, controlling operations of the discharge current cutoff means and the charge current cutoff means,

wherein specified threshold values needed for a startup state are stored in an active software memory which is read immediately after the startup of the protection process means; and

overcurrent detection means for providing control to enable the discharge current cutoff means in preference to the protection process means when the secondary battery is determined to be in an overcurrent state based on a charge and discharge current size of the secondary battery.

2. The battery pack according to claim 1 further comprising:

charge detection means for detecting the presence or absence of a charge operation by a charger for the secondary battery, wherein, when the secondary battery is determined to be in the overcurrent state, the overcurrent detection means interrupts the protection process means; and

the protection process means determines the secondary battery to be in the overcurrent state when detecting an interrupt from the overcurrent detection means, and restores a state of the secondary battery to the normal operation state when an output voltage value from the voltage detection means is greater than the specified threshold value and the charge detection means detects execution of the charge operation.

3. The battery pack according to claim 2, wherein, when detecting an interrupt from the overcurrent detection means, the protection process means uses nonvolatile storage means to store log information indicating transition of the secondary battery to the overcurrent state and present configuration information needed for an operation of the protection process means.

4. The battery pack according to claim 1, wherein the protection process means stores present configuration information needed for an operation of the protection process means in nonvolatile storage means and then stops an operation when the secondary battery is placed in an over-discharge state and a voltage detected by the voltage detection means becomes smaller than a specified value much smaller than a threshold value for identifying transition to the over-discharge state.

5. The battery pack according to claim 1, wherein the overcurrent detection means determines the secondary battery to be in the overcurrent state when a charge and discharge current size of the secondary battery becomes greater than a specified threshold value for a specified time period.

6. The battery pack according to claim 1, wherein the overcurrent detection means determines whether or not the overcurrent state takes effect, using a voltage comparator which compares a reference voltage with voltages at both ends of a resistor serially connected to the secondary battery.

7. The battery cell according to claim 1 further comprising:

temperature detection means for digitizing a temperature of the secondary battery,

wherein the protection process means determines a state of the secondary battery based on a value resulting from correcting an output voltage from the voltage detection means according to an output value from the temperature detection means.

8. The battery pack according to claim 1 further comprising:

boost means for boosting at least a voltage between a positive electrode and a negative electrode of the secondary battery, wherein the power supply voltage is supplied to the protection process means via the boost means.

9. The battery pack according to claim 1, wherein, when the secondary battery comprises a plurality of serially connected secondary battery cells, the voltage detection means detects a voltage between a positive electrode and a negative electrode individually for each of the secondary battery cells;

and

the protection process means individually determines a state of each of the secondary battery cells out of overcharge, normal operation, and over-discharge states based on an output voltage value from the voltage detection means.

10. The battery pack according to claim 9, wherein, when at least one of the secondary battery cells is determined to be in the overcharge state, the protection process means provides control to enable the charge current cutoff means, and when at least one of the secondary battery cells is determined to be in the over-discharge state, provides control to enable the discharge current cutoff means.

11. The battery pack according to claim 1 further comprising:

current accumulation means for outputting a signal corresponding to an accumulated value for charge and discharge currents of secondary battery;

communication means for establishing communication with an external device powered by the secondary battery;

remaining capacity information calculation means for calculating remaining capacity information about a remaining capacity of the secondary battery based on at least an output voltage value from the voltage detection means and an output signal from the current accumulation means and transmitting remaining capacity information to the external device via the communication means; and

power supply determination means for determining the presence or absence of power supply from the secondary battery to the external device based on availability or unavailability of communication with the external device using the communication means at a specified time interval,

wherein, when the power supply determination means determines that the secondary battery supplies power to the external device, the remaining capacity information calculation means calculates the remaining capacity information and transmits a calculated value to the external device at the specified time interval, and the protection process means determines a state of the secondary battery at a time interval shorter than the specified time interval; and

when the power supply determination means determines that the secondary battery does not supply power to the external device, the remaining capacity information calculation means calculates the remaining capacity information and stores it in nonvolatile storage means, and the protection process means determines a state of the secondary battery at the specified time interval.

12. The battery pack according to claim 11, wherein the specified time interval is sufficiently longer than an instruction clock frequency of the protection process means and the remaining capacity information calculation means.

13. The battery pack according to claim 11 further comprising erratic operation avoidance means for detecting an erratic operation, if any, in operations of at least one of the protection process means and the remaining capacity information calculation means based on the presence or absence of operations thereof at the specified time interval and allowing the protection process means and the remaining capacity information calculation means to perform an initialization process.

14. The battery pack according to claim 11, wherein, when the power supply determination means determines power supply to the external device from the secondary battery, the specified time interval is set to be an even-numbered multiple of a cycle for determining a state of the secondary battery.

15. A battery protection processing apparatus which uses a software control to implement a secondary battery protection function, the apparatus comprising:

discharge current cutoff means for selectively cutting off a discharge current in the secondary battery;

charge current cutoff means for selectively cutting off a charge current in the secondary battery;

voltage detection means for digitizing and outputting a voltage between a positive electrode and a negative electrode of the secondary battery;

protection process means for, based on an output voltage value from the voltage detection means, determining a state of the secondary battery out of overcharge, normal operation, and over-discharge states and, according to a determined state, controlling operations of the discharge current cutoff means and the charge current cutoff means,

wherein specified threshold values needed for a startup state are stored in an active software memory which is read immediately after the startup of the protection process means; and

overcurrent detection means for providing control to enable the discharge current cutoff means in preference to the protection process means when the secondary battery is determined to be in an overcurrent state based on a charge and discharge current size of the secondary battery.

16. A control method of enabling a battery protection processing apparatus to use a software control to implement a secondary battery protection function comprising the steps of:

determining a state of the secondary battery out of overcharge, normal operation, and over-discharge states based on an inter-electrode voltage between a positive electrode and a negative electrode of the secondary battery,

wherein specified threshold values needed for a startup state are stored in an active software memory which is read immediately after the startup of the protection process means;

according to a determined state, performing a protection process to control operations of a discharge current cutoff circuit to selectively cut off a discharge current of the secondary battery and a charge current cutoff circuit to selectively cut off a charge current of the secondary battery; and

providing control to enable the discharge current cutoff circuit in preference to the protection process when the secondary battery is determined to be in an overcurrent state based on a charge and discharge current size of the secondary battery.

17. The control method of a battery protection processing apparatus according to claim 16 comprising the steps of:

further performing a remaining capacity calculation process of calculating remaining capacity information about a remaining capacity of the secondary battery based on at least the inter-electrode voltage between electrodes of the secondary battery and an accumulated value for charge and discharge currents of the secondary battery;

performing a remaining capacity information transmission process of transmitting the remaining capacity information calculated by the remaining capacity calculation process to an external device powered by the secondary battery;

determining the presence or absence of power supply from the secondary battery to the external device based on availability or unavailability of communication with the external device at a specified time interval;

(1) when it is determined that the secondary battery supplies power to the external device;

performing the remaining capacity information calculation process and the remaining capacity information transmission process using a calculated value thereof at the specified time interval;

determining a state of the secondary battery at a time interval shorter than the specified time interval;

performing the protection process based on a determination result; and

(2) when it is determined that the secondary battery does not supply power to the external device, performing the remaining capacity information calculation process at the specified time interval;

storing the calculated remaining capacity information in nonvolatile memory; and

determining a state of the secondary battery at the specified time interval, and performing the protection process based on a determination result.