JP2004304940A - Battery pack, electronic apparatus, battery remaining capacity prediction system, and semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the power consumption of a battery pack when the battery pack is not in use, and to precisely predict a battery remaining capacity when the battery pack is in use. <P>SOLUTION: When power is not fed to the other electronic apparatus, power supply to an internal circuit of the battery pack is shut off by a power-feed shut-off circuit, and when the power supply is started to an electronic apparatus from the battery pack, the battery remaining capacity is precisely predicted by a battery voltage equivalent to an unloaded voltage such as the non-supply of the power to the electronic apparatus, so that the battery voltage of the battery pack before the start of the power supply to the electronic apparatus is measured by a voltage measuring circuit. When the power is not fed to the other electronic apparatus, the power supply to the internal circuit of the battery pack is also shut off. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a battery pack, an electronic device, a battery remaining amount prediction system, and a semiconductor device, and more particularly to prediction of a battery remaining amount in a battery pack.
[0002]
[Prior art]
A portable electronic device such as a notebook computer is equipped with a battery as a power supply for the device. However, due to the cost required for operating the device and the current capacity capable of instantaneously discharging, a lithium ion secondary battery is generally used. (Li + secondary battery) and the like. Many devices also have a built-in charging circuit so that a secondary battery built into the device can be easily charged simply by connecting an AC adapter or the like to the device. Generally, a portable electronic device uses a built-in secondary battery as a device power supply. However, in a case of operation on a desk or the like, an operation is performed by receiving power supply from an external power supply such as an AC adapter. Some operations.
[0003]
Among the secondary batteries, for example, a lithium ion secondary battery and a nickel hydride battery (NiMH battery) are vulnerable to overdischarge unlike a nickel cadmium battery (Nicad battery), and the user has accidentally overdischarged the battery. In such a case, irreparable damage such as a decrease in capacity and deterioration of the battery function is caused.
[0004]
Therefore, in order to prevent the battery function from deteriorating due to user's erroneous operation, an overdischarge prevention circuit that detects that the battery voltage has fallen below a predetermined voltage and shuts off output to the outside is built into the battery pack together with the battery. It is supposed to.
When using a battery pack with a built-in over-discharge prevention circuit in the device, the device monitors the output voltage from the battery pack, and data destruction etc. does not occur before the over-discharge prevention circuit of the battery pack operates The internal control of the device must be performed as described above.
[0005]
Especially in information processing equipment such as notebook computers, if power is not supplied from the battery pack during operation, all data being processed will be lost. It is necessary to save data to a non-volatile recording medium. For the purpose of preventing such accidents, some recent devices such as notebook personal computers have a remaining capacity display function for notifying the user of the remaining capacity of the battery pack.
[0006]
Here, the method of estimating the remaining amount of the battery pack includes: (1) a method of integrating the amount of current flowing out of the battery pack and subtracting the amount of current flowing out from the rated current capacity of the battery pack to predict the remaining amount. And (2) a method of estimating the remaining amount from the voltage of the battery pack. Therefore, the battery pack has a current measuring circuit and a current integrating circuit used for remaining amount prediction, a voltage measuring circuit, and the like inside.
[0007]
In the method based on current integration, a resistor having a small resistance value is inserted in series into a battery circuit, and the current flowing through the circuit is measured using a voltage drop (potential difference between both ends of the resistor) generated by the current flowing through the resistor. Integrate. This includes a coulomb counter method for measuring the amount of current (coulomb amount) by integrating the flowing current, and a sampling method for measuring and integrating the current at fixed time intervals.
[0008]
FIG. 11 is a diagram showing a configuration of a conventional battery pack having a remaining amount management function.
11, a battery pack (battery) 50 includes three battery cells PW1, PW2, PW3, a protection circuit 51, a switch circuit 52 including transistors (FETs: field effect transistors) T1 and T2, a remaining amount management microcomputer 53, and an EEPROM 54. , And a resistor R1. An electronic device 60 such as a personal computer to which the battery pack 50 is attached has a power supply microcomputer 61, a load 62, and a charger 63.
[0009]
When the battery pack 50 is mounted on the electronic device 60, a detachment detection signal SIG from the power supply microcomputer 61 is input to the protection circuit 51 in the battery pack 50, for example, as disclosed in Patent Document 1.
At this time, when power is supplied from the battery cells PW1 to PW3 to the load 62, the protection circuit 51 turns on the transistor T1 (a state in which the switch circuit 52 is closed). When charging PW3, the transistor T2 is turned on (the switch circuit 52 is closed). The protection circuit 51 monitors the voltages of the battery cells PW1 to PW3. When the voltage drops below a predetermined voltage, the protection circuit 51 turns off the transistor T1 to open the switch circuit 52 to prevent overdischarge.
[0010]
On the other hand, when the battery pack 50 is removed from the electronic device 60 and the detachment detection signal SIG from the power supply microcomputer 61 is not supplied to the protection circuit 51, the protection circuit 51 turns off the transistors T1 and T2.
[0011]
Further, the protection circuit 51 measures the amount of current flowing out of the battery based on the potential difference between both ends of the resistor R1, and notifies the remaining amount management microcomputer 53 of the measurement. The remaining amount management microcomputer 53 integrates the current amount and the time notified from the protection circuit 51 as a current integration circuit, and calculates the remaining amount of the battery based on the integration result and the amount of current charged in the battery pack 50. Predict. The power supply microcomputer 61 is connected by a communication interface so as to be able to exchange data DT with the remaining amount management microcomputer 53, and displays a remaining amount based on the battery remaining amount predicted by the remaining amount management microcomputer 53. Controls and controls the charger.
The EEPROM 54 stores information on the battery pack 50, and stores, for example, information such as the rated capacity of the battery cells, the number of times of charge / discharge, and the number of years of use.
[0012]
Patent Document 2 discloses an electronic device that outputs the remaining capacity of a secondary battery when a battery pack containing a secondary battery is mounted on the electronic device.
[0013]
[Patent Document 1]
JP-A-2000-32682
[Patent Document 2]
JP-A-8-278837
[0014]
[Problems to be solved by the invention]
However, the above-described conventional battery remaining amount prediction method has the following problems.
In the method of estimating the remaining amount by integrating the current flowing out of the battery pack, a state where the battery pack is not actually used to integrate the current (for example, when the electronic device is stopped, or when the battery pack is In this case, it is necessary to constantly monitor the amount of current, perform current integration, and store the value. Therefore, the current integrating circuit must always be operating, and power consumption by the current integrating circuit itself always occurs.
[0015]
Here, as described above, a lithium-ion secondary battery deteriorates its battery function when it is overdischarged. Therefore, it is required that the lithium-ion secondary battery always has a remaining amount equal to or more than a certain amount. For example, even when the battery pack is not used, such as when the battery pack is in stock for a long period of time, a circuit for predicting the remaining amount, such as a current integrating circuit, consumes battery power. Charging is required.
[0016]
Also, the method of predicting the remaining amount by current integration is based on the theory that the coulomb amount is preserved, but in practice, when charging and discharging of the battery are repeated, the battery can be discharged with an increase in the number of times of charging and discharging. Since the amount of current decreases, the predicted remaining amount may differ from the actual remaining amount.
[0017]
In the method of estimating the remaining amount from the voltage of the battery pack, the relative remaining amount can be obtained correctly by measuring the open-circuit voltage of the battery as a voltage, as described later. It is impossible to measure the open-circuit voltage under the load condition.
[0018]
In general, the amount of current and voltage flowing out of the battery are measured in a loaded state, and the open voltage is calculated by taking into account the internal impedance of the battery to predict the remaining amount. However, since the internal impedance of the battery changes over time depending on the number of times the battery is used (the number of times of charging and discharging) and the use conditions, the estimated remaining amount may be incorrect due to the influence of the change.
[0019]
The present invention has been made in view of such circumstances, and it is possible to prevent power consumption in a battery pack when the battery pack is not used, and to reduce a remaining battery level when using the battery pack. It is intended to be able to predict accurately.
[0020]
[Means for Solving the Problems]
The present invention provides a power supply cutoff circuit that cuts off power supply to an internal circuit of a battery pack when power is not supplied to another electronic device, and a power supply cutoff circuit that starts supplying power to the electronic device from the battery pack. And a voltage measuring circuit for measuring a battery voltage in the battery pack before starting power supply.
[0021]
According to the present invention, the battery voltage in the battery pack is measured by the voltage measurement circuit before the power supply to the electronic device is started, that is, in a state where the power is not supplied to the electronic device. The voltage can be measured, and the remaining battery capacity of the battery pack can be accurately predicted. Furthermore, since the remaining battery level of the battery pack is predicted from the battery voltage corresponding to the no-load condition, when the battery pack is not used, the power supply cutoff circuit can also cut off the power supply to the internal circuit of the battery pack. become able to.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0023]
First, the discharge characteristics of a secondary battery will be described using a lithium ion secondary battery as an example.
FIG. 1A is a diagram showing the discharge characteristics of a lithium ion secondary battery at different charge / discharge times, where the horizontal axis represents the elapsed time from the start of discharge (discharge time) [min], and the vertical axis represents the battery voltage. [V]. The load is the same regardless of the number of times of charging and discharging.
[0024]
As time elapses from the start of discharge, the battery voltage decreases from the voltage at full charge (4.2 V) to the final discharge voltage (3.0 V). In addition, the actual time that can be actually used (elapsed time until reaching the final discharge voltage) changes depending on the number of times of charging and discharging, and the actual time decreases as the number of times of charging and discharging increases.
[0025]
FIG. 1B shows the relationship between the remaining battery level (%) and the battery voltage obtained by normalizing the discharge time based on the discharge characteristics at each charge / discharge count shown in FIG. In FIG. 1B, the horizontal axis represents the remaining battery capacity, and the vertical axis represents the battery voltage. As shown in FIG. 1 (B), the relative remaining amount of the battery with respect to the battery voltage is always constant even when the load is constant, even if the number of times of charging and discharging increases and the actual time that can be used actually changes. It is the same regardless of the number of times.
[0026]
FIG. 2A is a diagram showing the discharge characteristics of the lithium-ion secondary battery when the load is changed. The horizontal axis represents the elapsed time from the start of discharge (discharge time) [min], and the vertical axis represents the battery. Voltage [V]. The battery voltage decreases from the voltage at the time of full charge to the final discharge voltage as time elapses from the start of discharge. Also, as the load increases, the battery voltage becomes the final discharge voltage in a shorter time.
[0027]
FIG. 2B shows the relationship between the remaining battery level (%) and the battery voltage obtained by normalizing the discharge time based on the discharge characteristics at each load shown in FIG. 2A. In FIG. 2B, the horizontal axis represents the remaining battery capacity, and the vertical axis represents the battery voltage.
[0028]
When the load is constant as shown in FIG. 1B, the remaining battery level relative to the battery voltage is always the same regardless of the number of times of charging and discharging. As shown in FIG. 2B, the remaining battery level relative to the battery voltage differs depending on the load and does not always match. This is because the current flowing varies depending on the load, and the voltage drop due to the internal impedance of the battery varies.
[0029]
FIG. 3 is a diagram in which the relationship between the remaining battery level (%) and the battery voltage at the time of load change shown in FIG. 2B is corrected for the voltage drop due to the internal impedance of the battery. As is clear from FIG. 3, if the influence of the voltage drop due to the internal impedance of the battery is removed, the relative remaining amount of the battery relative to the battery voltage is always the same regardless of the size of the load.
[0030]
FIG. 4A is a diagram showing, as a discharge characteristic, a change in the battery capacity when the battery is left in a high temperature environment in a fully charged state. The horizontal axis is the discharge time [min], and the vertical axis is the battery voltage [V]. The battery voltage decreases from the voltage at full charge to the final discharge voltage as the discharge time increases. Further, the discharge time until reaching the final discharge voltage differs depending on the leaving time.
[0031]
4A shows the relationship between the remaining battery level (%) and the battery voltage obtained by normalizing the discharge time based on the discharge characteristics of the battery whose capacity has been degraded when left in a high temperature environment in a fully charged state. Is shown in FIG. In FIG. 4B, the horizontal axis represents the remaining battery capacity, and the vertical axis represents the battery voltage. As shown in FIG. 4B, the relative remaining amount of the battery is the same even when it is in a new state and after it has been deteriorated by being left at a full charge and high temperature.
[0032]
As can be understood from the above description, according to FIGS. 1 to 4, in order to predict the remaining amount of the battery from the voltage of the battery, the battery voltage at no load, that is, the correct remaining battery amount is obtained if the open voltage is obtained. It can be seen that it can be obtained. In other words, even if the battery is left alone for a long period of time, it can be understood that the battery remaining amount can be immediately and accurately predicted if the open circuit voltage, which is the voltage at no load, is correctly measured.
[0033]
Therefore, according to the present invention, when the battery pack is left alone, the power supply to all the circuits in the battery pack is shut off, and when the battery pack is used, before the power supply to the outside is started, The remaining battery level is estimated by measuring the battery voltage corresponding to no load.
[0034]
(1st Embodiment)
FIG. 5 is a diagram for explaining the first embodiment of the present invention.
5, a battery pack (battery) 10 includes three battery cells PW1, PW2, and PW3 connected in series, a protection circuit 11, a switch circuit 12, a microcomputer 13, an EEPROM (Electrically Erasable and Programmable ROM) 18, and a resistor. R1.
[0035]
The protection circuit 11 controls opening and closing of the switch circuit 12 according to the voltages of the battery cells PW1 to PW3, instructions from the microcomputer 13, and the like. Further, the protection circuit 11 measures the amount of current flowing out of the battery based on the potential difference between both ends of the resistor R <b> 1 and notifies the microcomputer 13.
[0036]
The switch circuit 12 is provided between the battery cells PW1 to PW3 and a power supply terminal (not shown) for connecting to an electronic device (device) 30 such as a personal computer, which will be described later, and includes two transistors (FETs: field effect transistors) T1. , T2.
[0037]
The microcomputer 13 controls each circuit and exchanges data, and has a voltage measurement circuit 14, an AD converter 15, a storage circuit 16, and a communication interface 17. The voltage measurement circuit 14 measures the voltages of the battery cells PW1 to PW3. The voltage measurement circuit 14 may be configured to cause the protection circuit 11 to measure the voltages of the battery cells PW1 to PW3 and receive the measurement result, or to provide the voltage in the protection circuit 11 instead of the microcomputer 13. May be.
[0038]
The AD converter 15 converts the measured value of the voltage obtained as analog information by the voltage measuring circuit 14 into digital information. The storage circuit 16 stores and holds the voltage value of the digital information converted by the AD converter 15. The communication interface 17 is for transmitting and receiving the attachment / detachment detection signal SIG and the data DT to / from the electronic device 30.
The EEPROM 18 stores information on the battery pack 10 (for example, information on the number of times of charge / discharge and the number of years of use).
[0039]
The electronic device 30 includes a power supply microcomputer 31, a load 32, and a charger 33. The power supply microcomputer 31 has a remaining amount predicting circuit 34, exchanges data with the microcomputer 13, displays a remaining amount, and controls the charger 33. The power supply microcomputer 31 outputs a detachment detection signal SIG for indicating whether or not the battery pack 10 is mounted on the electronic device 30.
[0040]
The remaining amount prediction circuit 34 is a circuit that predicts the remaining amount of the battery based on the data DT supplied from the microcomputer 13. The load 32 is a load that consumes power supplied from the battery pack 10, and the charger 33 is for charging the battery cells PW <b> 1 to PW <b> 3 according to an instruction from the power supply microcomputer 31.
[0041]
Next, the operation will be described.
First, when the battery pack 10 shown in FIG. 5 is not attached to the electronic device 30, that is, when the battery pack 10 is left alone, all the circuits (the protection circuit 11, the microcomputer 13 , Etc.), and is turned off.
[0042]
Next, the operation of the battery pack 10 when the battery pack 10 is mounted on the electronic device 30 will be described with reference to FIG.
In step S11, the battery pack 10 is attached to the electronic device 30 by the detachment detection signal SIG output from the power supply microcomputer 31 of the electronic device 30 and supplied to the battery pack 10 via the attachment detection terminal (not shown). When detected by the battery pack 10, in step S12, only the circuits related to the voltage measurement (the voltage measurement circuit 14, the AD converter 15, and the storage circuit 16) are turned on to start the operation. Therefore, at this time, the switch circuit 12 is in an open state (off state), and power is not supplied from the battery pack 10 to the electronic device 30.
[0043]
Next, in step S13, the voltage measurement circuit 14 measures the battery voltages of the battery cells PW1 to PW3 in a state where the battery pack 10 is not supplying power to the electronic device 30. Further, the voltage measurement circuit 14 stores the measurement result in the storage circuit 16 via the AD converter 15.
[0044]
In step S14, voltage measurement circuit 14 measures the total battery voltage of battery cells PW1 to PW3, and stores the measurement result in storage circuit 16 via AD converter 15. In these steps S13 and S14, the current flowing in the battery pack 10 is very small and the voltage drop due to the internal impedance of the battery is so small that it can be neglected. Become.
[0045]
Next, in step S15, it is determined based on the measurement results in steps S13 and S14 whether or not the battery is overdischarged. As a result, if the battery is overdischarged, the process ends. On the other hand, if the result of determination is that the battery is not in an overdischarged state, the microcomputer 13 notifies the protection circuit 11 that the battery pack 10 is mounted on the electronic device 30 in step S16, and the protection circuit 11 The switch circuit 12 (transistor T1) is turned on to start supplying power to the electronic device 30, and the process ends. Here, since the time for measuring the battery cells PW1 to PW3 in the battery pack 10 is very short, it is negligible in view of the entire battery removal time, and does not cause any inconvenience.
[0046]
The operation of the electronic device 30 when the battery pack 10 is mounted on the electronic device 30 will be described with reference to FIG.
In step S11, when the electronic device 30 determines that the battery pack 10 is mounted and power is being supplied, in step S22, the power supply microcomputer 31 determines whether there is no power stored in the storage circuit 16 in the microcomputer 13. Read the battery voltage data corresponding to the load. Then, in step S23, the remaining amount prediction circuit 34 predicts the remaining battery amount based on the read battery voltage data, for example, from the relationship between the battery voltage and the remaining battery amount shown in FIGS.
[0047]
Next, in step S24, the remaining amount prediction circuit 34 measures the battery voltage and the discharge current of the battery cells PW1 to PW3 in a state where the battery pack 10 supplies power to the electronic device 30. Note that the measurement in step S24 may be performed by the battery pack 10, and the measurement result may be notified to the power supply microcomputer 31.
[0048]
In step S25, the remaining amount prediction circuit 34 calculates the internal impedance of the battery based on the battery voltage read in step S22 and the battery voltage and discharge current measured in step S24. The internal impedance is obtained by (battery voltage read in step S22−battery voltage measured in step S24) / (discharge current measured in step S24). Then, in step S26, the value of the predicted internal impedance obtained in step S25 is supplied to and stored in the battery pack 10, and the process ends.
[0049]
As described above, the deterioration and the like of the battery cells PW1 to PW3 in the battery pack 10 can be determined by calculating the internal impedance of the battery and comparing it with the previously calculated and stored internal impedance of the battery. As a result, when the battery cells PW1 to PW3 are significantly deteriorated, a warning or the like may be issued to the user to urge the replacement of the battery pack 10 or the like.
[0050]
Thereafter, using the latest internal impedance of the battery, an open-circuit voltage is obtained by calculation from the battery voltage and the discharge current at the time of load, and the battery remaining amount is predicted.
[0051]
The operation of the battery pack 10 when the battery pack 10 is removed from the electronic device 30 will be described with reference to FIG.
In step S31, when the battery pack 10 detects that the battery pack 10 has been removed from the electronic device 30, in step S32, based on the instruction from the microcomputer 13, the protection circuit 11 The switch circuit 12 (transistors T1, T2) is turned off to shut off power supply to the outside.
[0052]
In steps S32 and S33, the voltage measurement circuit 14 measures each battery voltage of the battery cells PW1 to PW3 and the total battery voltage, and stores the measurement result in the storage circuit 16 via the AD converter 15. As a result, it is possible to calculate how much the remaining battery power has decreased during the next mounting.
Next, in step S35, the power supply of the circuit group related to the voltage measurement is cut off, and the power supply of all the circuits in the battery pack 10 is cut off, and the process ends.
[0053]
As described above, according to the first embodiment, by measuring the battery voltage in the battery pack 10 in a state where power is not supplied to the electronic device 30, a battery voltage equivalent to a no-load condition is obtained. The remaining battery level of the battery pack 10 is predicted from the battery voltage. That is, unlike the method based on the current integration, the remaining battery level is predicted from the battery voltage, so that when the battery pack 10 is not attached to the electronic device 30 and is left alone, the battery pack 10 Power supply to each circuit can be cut off to prevent power consumption. In addition, the battery voltage of the battery pack 10 that is not supplying power to the electronic device 30 and corresponding to a no-load condition is measured to predict the remaining battery level of the battery pack 10, so that the remaining battery level can be accurately predicted. .
[0054]
In the first embodiment described above, a circuit group related to voltage measurement such as the voltage measurement circuit 14 is provided in the battery pack 10 and the remaining amount prediction circuit 34 is provided in the electronic device 30. Both the circuit group related to the measurement and the remaining amount prediction circuit 34 may be provided in the electronic device 30.
[0055]
(Second embodiment)
Next, a second embodiment of the present invention will be described.
In the above-described first embodiment, the power supply microcomputer 31 included in the electronic device 30 is provided with the remaining amount prediction circuit 34, and the electronic device 30 predicts the remaining amount of the battery. In the second embodiment described below, a remaining capacity prediction circuit is provided in a microcomputer of a battery pack, and the remaining capacity of the battery is predicted by the battery pack.
[0056]
FIG. 9 is a diagram for explaining the second embodiment of the present invention. In FIG. 9, blocks and the like having the same functions as the blocks and the like shown in FIG. 5 are denoted by the same reference numerals, and redundant description will be omitted. In addition, blocks and the like that are not the same as the blocks and the like illustrated in FIG. 5 but have corresponding functions are denoted by the same reference numerals.
[0057]
9, the microcomputer 13 'includes a voltage measurement circuit 14, an AD converter 15, a storage circuit 16, a communication interface 17, a control circuit 19, and a remaining amount prediction circuit 20. Therefore, the power supply microcomputer 31 'does not include the remaining amount prediction circuit.
[0058]
The control circuit 19 controls each circuit in the microcomputer 13 ', and controls, for example, a process related to a remaining battery amount prediction shown in FIG. The remaining amount prediction circuit 20 is the same as the remaining amount prediction circuit 34 shown in FIG. The remaining amount predicting circuit 20 predicts the remaining battery amount based on the battery voltage stored in the storage circuit 20 in a state where power is not supplied to the electronic device 30, and at normal times, based on the discharging current. Predict the amount.
[0059]
Next, the operation will be described.
FIG. 10 is a flowchart illustrating the operation of the battery pack 10 according to the second embodiment.
[0060]
In step S41, when it is detected that the battery pack 10 is attached to the electronic device 30 in the same manner as in step S11 of FIG. 6, in step S42, a circuit group (voltage measurement circuit 14, The power is supplied to the AD converter 15, the storage circuit 16, the control circuit 19, and the remaining amount prediction circuit 20) to start the operation. At this time, the switch circuit 12 is in an open state, and power is not supplied from the battery pack 10 to the electronic device 30.
[0061]
In step S43, voltage measurement circuit 14 measures the battery voltage of battery cells PW1 to PW3 in a state where battery pack 10 is not supplying power to electronic device 30, and stores the measurement result via AD converter 15. It is stored in the circuit 16. In step S44, remaining amount prediction circuit 20 predicts a relative remaining amount of battery based on the battery voltage stored in storage circuit 16. Here, the relative remaining battery level is the remaining battery level based on the voltage.
[0062]
In step S45, the remaining amount prediction circuit 20 calculates a difference between the relative remaining amount of the battery obtained in step S44 and the relative remaining amount of the battery when the battery pack 10 was previously removed. Further, in step S46, the remaining amount prediction circuit 20 corrects the absolute remaining battery amount derived from the relative remaining battery amount obtained in step S44, based on the calculation result in step S45. Here, the absolute remaining battery level is the remaining battery level based on the current.
[0063]
Next, in step S47, if the battery pack 10 is not in the overdischarge state, the microcomputer 13 'notifies the protection circuit 11 that the battery pack 10 is mounted on the electronic device 30, and the protection circuit 11 The switch circuit 12 (transistor T1) is turned on to start supplying power to the electronic device 30. Then, in step S48, a remaining amount prediction process by current integration or the like based on the discharge current is started, and the process ends.
[0064]
When it is detected in step S49 that the battery pack 10 has been removed from the electronic device 30 in the same manner as in step S31 of FIG. 8, in step S50, the protection circuit 11 is determined based on an instruction from the microcomputer 13 '. Turns off the switch circuit 12 (transistors T1 and T2) for preventing overdischarge, and cuts off power supply to the outside.
[0065]
Subsequently, in steps S51 and S52, the relative battery remaining amount is predicted in the same manner as in steps S43 and S44 described above. The absolute battery remaining amount calculated by battery integration or the like in step S53 and the relative battery remaining amount obtained in step S52 are stored in the storage circuit 16 (or the EEPROM 18). Further, in step S54, the battery voltage measured in step S51 is also stored in the storage circuit 16 (or the EEPROM 18). As a result, it is possible to calculate how much the remaining battery power has decreased during the next mounting.
[0066]
Next, in step S55, the power supply of the voltage measurement circuit 14 and the remaining amount prediction circuit 20 is cut off, and the power supply of all the circuits in the battery pack 10 is cut off, and the process ends.
[0067]
As described above, according to the second embodiment, the same effects as those of the above-described first embodiment can be obtained, and the remaining amount can be predicted using only the battery pack 10. The interface with the electronic device 30 can be simplified. In addition, since the remaining amount prediction is performed only by the battery pack 10, the control of the battery pack 10 and the electronic device 30 can be performed independently of each other, which is easy.
[0068]
In the first and second embodiments, the battery pack 10 has three battery cells PW1 to PW3 as an example, but the number of battery cells is arbitrary. Further, the switch circuit 12 is an example, and any circuit may be used as long as current can flow in both directions and ON / OFF control can be performed. Further, the EEPROM 18 may have the function of the storage circuit 16 without providing the storage circuit 16. Further, the EEPROM 18 is not limited to this, and may be any nonvolatile memory in which data can be rewritten.
[0069]
In the first and second embodiments, the voltage measurement circuit 14 measures only the battery voltage and stores it in the storage circuit 16, but also measures the discharge current and the battery temperature in addition to the battery voltage. The information may be stored in the storage circuit 16.
[0070]
Further, each of the embodiments described above is merely an example of a concrete example for carrying out the present invention, and the technical scope of the present invention should not be interpreted in a limited manner. That is, the present invention can be implemented in various forms without departing from the technical idea or the main features.
Various aspects of the present invention are shown below as supplementary notes.
[0071]
(Supplementary Note 1) a power supply cutoff circuit that cuts off power supply to an internal circuit of the battery pack when power is not supplied to another electronic device;
A battery measuring circuit for measuring a battery voltage of the battery pack before starting power supply to the electronic device when starting power supply to the electronic device from the battery pack.
(Supplementary Note 2) The battery pack according to Supplementary Note 1, wherein the battery pack has an arbitrary number of battery cells, and measures a battery voltage of each of the battery cells as a battery voltage in the battery pack.
(Supplementary Note 3) The storage device further includes a storage circuit that holds a measurement result of the voltage measurement circuit,
Before starting the power supply, supplying power to a circuit group related to the measurement of the battery voltage, measuring a battery voltage in the battery pack, storing the battery voltage in the storage circuit, and then supplying power to the electronic device. 3. The battery pack according to claim 1, wherein
(Supplementary Note 4) The battery pack further includes a current measurement circuit that measures a current flowing out of the battery pack,
4. The battery pack according to claim 3, wherein a battery voltage and a current of the battery pack after starting power supply to the electronic device are measured and stored in the storage circuit.
(Supplementary Note 5) A switch circuit capable of controlling whether to supply power to the electronic device,
2. The battery pack according to claim 1, wherein the switch circuit is controlled in accordance with a measurement result of a battery voltage in the battery pack before starting the power supply.
(Supplementary Note 6) a power supply cutoff circuit that cuts off power supply to an internal circuit of the battery pack when power is not supplied to another electronic device;
When starting power supply to the electronic device from the battery pack, a voltage measurement circuit that measures a battery voltage in the battery pack before starting power supply to the electronic device,
And a remaining amount predicting circuit for predicting a remaining amount of the battery of the battery pack based on a measurement result of the voltage measuring circuit.
(Supplementary note 7) The supplementary note 6, wherein the remaining amount prediction circuit predicts the remaining battery amount of the battery pack based on the correspondence between the battery voltage and the remaining battery amount held in advance. Battery level prediction system.
(Supplementary Note 8) When starting the power supply to the electronic device from the battery pack that shuts off the power supply to the internal circuit when the power supply to the other electronic device is not performed, it is measured before the power supply to the electronic device is started. An electronic device comprising a remaining amount prediction circuit for predicting the remaining amount of the battery of the battery pack based on the battery voltage of the battery pack.
(Supplementary Note 9) The electronic device according to Supplementary Note 8, wherein the remaining amount prediction circuit predicts the remaining battery amount of the battery pack based on the correspondence between the battery voltage and the remaining battery amount acquired in advance. .
(Supplementary Note 10) A voltage measurement circuit for measuring a battery voltage in the battery pack;
A storage circuit for holding a measurement result in the voltage measurement circuit,
A control circuit for causing the voltage measurement circuit to measure the battery voltage before starting power supply to the electronic device from the battery pack.
(Supplementary Note 11) A voltage measurement circuit for measuring a battery voltage in the battery pack,
When starting the power supply to the electronic device having the voltage measurement circuit, after measuring the battery voltage in the battery pack before starting the power supply to the circuit in the electronic device by the voltage measurement circuit, An electronic device characterized by supplying power to a circuit.
(Supplementary Note 12) A voltage measurement circuit that measures a battery voltage in a battery pack having a remaining amount prediction function,
A storage circuit for holding a measurement result in the voltage measurement circuit,
The voltage measurement circuit measures a battery voltage after the battery pack is removed from the electronic device and a battery voltage before the battery pack is mounted on the electronic device and power supply to the electronic device is started. Battery remaining amount prediction system.
(Supplementary Note 13) The power supply to a circuit included in the battery pack is interrupted during a period from when the battery pack is removed from the electronic device to when the battery pack is attached to the electronic device, according to Supplementary Note 12. Battery level prediction system.
(Supplementary note 14) The supplementary note, wherein the remaining battery capacity of the battery pack obtained by a different method is corrected using the remaining battery capacity of the battery pack predicted based on the battery voltage measured by the voltage measurement circuit. The battery remaining amount prediction system according to claim 12.
[0072]
【The invention's effect】
As described above, according to the present invention, when power is not supplied to another electronic device, power supply to the internal circuit of the battery pack is cut off by the power supply cutoff circuit, and power is supplied from the battery pack to the electronic device. Is started, the battery voltage in the battery pack before starting the power supply to the electronic device is measured by the voltage measurement circuit. As a result, the remaining battery level can be accurately predicted based on the battery voltage corresponding to the no-load state when power is not supplied to the electronic device, and unlike the method based on current integration, the power is supplied to other electronic devices. When the power is not supplied, the power supply to the internal circuit of the battery pack can be cut off. Therefore, power consumption in the battery pack can be prevented when the battery pack is not used, and the remaining battery level can be accurately predicted when the battery pack is used.
[Brief description of the drawings]
FIG. 1 is a diagram showing discharge characteristics of lithium ion secondary batteries having different charge / discharge times.
FIG. 2 is a diagram showing discharge characteristics of a lithium ion secondary battery when a load changes.
FIG. 3 is a diagram showing discharge characteristics of a lithium ion secondary battery when a load changes.
FIG. 4 is a diagram showing a change in battery capacity when left in a high temperature environment in a fully charged state as a discharge characteristic of a lithium ion secondary battery.
FIG. 5 is a diagram for explaining the first embodiment of the present invention.
FIG. 6 is a flowchart showing an operation on the battery pack side when a battery is mounted in the first embodiment.
FIG. 7 is a flowchart illustrating an operation on the electronic device side when the battery is mounted in the first embodiment.
FIG. 8 is a flowchart showing an operation at the time of removing a battery in the first embodiment.
FIG. 9 is a diagram for explaining a second embodiment of the present invention.
FIG. 10 is a flowchart showing an operation in the second embodiment.
FIG. 11 is a diagram showing a configuration of a conventional battery pack.
[Explanation of symbols]
10 Battery pack
11 Protection circuit
12 Switch circuit
13, 13 'microcomputer
14 Voltage measurement circuit
15 AD converter
16 Memory circuit
17 Communication interface
18 EEPROM
19 Control circuit
20, 34 Remaining amount prediction circuit
30 Electronic equipment
31, 31 'power supply microcomputer
PW1, PW2, PW3 Battery cells
R1 Resistance for current measurement

Claims (10)

A power supply cutoff circuit that cuts off power supply to an internal circuit of the battery pack when not supplying power to other electronic devices;
A battery measuring circuit for measuring a battery voltage of the battery pack before starting power supply to the electronic device when starting power supply to the electronic device from the battery pack. The battery pack according to claim 1, wherein the battery pack has an arbitrary number of battery cells, and measures a battery voltage of each of the battery cells as a battery voltage in the battery pack. Further comprising a storage circuit for holding a measurement result in the voltage measurement circuit,
Before starting the power supply, supplying power to a circuit group related to the measurement of the battery voltage, measuring a battery voltage in the battery pack, storing the battery voltage in the storage circuit, and then supplying power to the electronic device. The battery pack according to claim 1, wherein: A current measuring circuit for measuring a current flowing out of the battery pack,
4. The battery pack according to claim 3, wherein a battery voltage and a current of the battery pack after starting power supply to the electronic device are measured and stored in the storage circuit. 5. A switch circuit capable of controlling whether to supply power to the electronic device,
2. The battery pack according to claim 1, wherein the switch circuit is controlled according to a measurement result of a battery voltage in the battery pack before starting the power supply. 3. A power supply cutoff circuit that cuts off power supply to an internal circuit of the battery pack when not supplying power to other electronic devices;
When starting power supply to the electronic device from the battery pack, a voltage measurement circuit that measures a battery voltage in the battery pack before starting power supply to the electronic device,
And a remaining amount predicting circuit for predicting a remaining amount of the battery of the battery pack based on a measurement result of the voltage measuring circuit. When starting the power supply to the electronic device from the battery pack that shuts off the power supply to the internal circuit when not supplying the power to the other electronic devices, the battery pack measured before starting the power supply to the electronic device. An electronic apparatus, comprising: a remaining amount predicting circuit for predicting a remaining amount of a battery of the battery pack based on a battery voltage. A voltage measurement circuit for measuring a battery voltage in the battery pack;
A storage circuit for holding a measurement result in the voltage measurement circuit,
A control circuit for causing the voltage measurement circuit to measure the battery voltage before starting power supply to the electronic device from the battery pack. A voltage measurement circuit for measuring a battery voltage in the battery pack,
When starting the power supply to the electronic device having the voltage measurement circuit, after measuring the battery voltage in the battery pack before starting the power supply to the circuit in the electronic device by the voltage measurement circuit, An electronic device characterized by supplying power to a circuit. A voltage measuring circuit for measuring a battery voltage in a battery pack having a remaining amount predicting function,
A storage circuit for holding a measurement result in the voltage measurement circuit,
The voltage measurement circuit measures a battery voltage after the battery pack is removed from the electronic device and a battery voltage before the battery pack is mounted on the electronic device and power supply to the electronic device is started. Battery remaining amount prediction system.

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