Electronic device and control method thereof

Abstract

The present invention provides an electronic device and a control method thereof for accurately determining the state of a lithium-ion battery. The electronic device comprises: a lithium-ion battery; a deformation detection unit that detects the deformation of the lithium-ion battery; a full charge detection unit that detects when the lithium-ion battery is fully charged; a stability detection unit that detects a stable state after the full charge detection unit detects full charge; and a state determination unit that determines the state of the lithium-ion battery using the deformation detected by the deformation detection unit when the stability detection unit detects the stable state.

Description

Technical Field

[0001] The present invention relates to an electronic device and a control method thereof. Background Art

[0002] Lithium-ion batteries, known as secondary batteries, are widely used in electronic devices such as smartphones. However, they degrade due to repeated charging and discharging. In particular, repeated charging and discharging can cause internal pressure to rise due to the expansion of the internal laminate and the vaporization of the electrolyte caused by rising internal temperatures, causing the lithium-ion battery to swell. Unchecked aging of lithium-ion batteries can pose a risk of fire or explosion.

[0003] Therefore, a proposal has been made (see, for example, Patent Document 1) to provide a pressure sensor that detects pressure generated by the expansion of the lithium ion battery and to monitor whether the lithium ion battery is deformed based on an output signal from the pressure sensor.

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent No. 5881593 Summary of the Invention

[0006] However, as described in Patent Document 1, the deformation of lithium-ion batteries does not increase over time, but rather increases during charging and decreases during discharge. Therefore, if a lithium-ion battery is repeatedly charged and discharged, the deformation increases and decreases with each charge and discharge, and the overall deformation increases due to aging.

[0007] Therefore, the amount of deformation of the lithium-ion battery increases or decreases due to charge and discharge, so the error in the detection timing depending on the amount of deformation becomes large, and the state of the lithium-ion battery may not be accurately determined.

[0008] An object of the present invention is to accurately determine the state of a lithium-ion battery.

[0009] The disclosed technology is an electronic device comprising: a lithium-ion battery; a deformation detection unit that detects the deformation of the lithium-ion battery; a full charge detection unit that detects whether the lithium-ion battery is fully charged; a stability detection unit that detects a stable state after the full charge detection unit detects that the battery is fully charged; and a state determination unit that uses the deformation detected by the deformation detection unit when the stability detection unit detects that the battery is in a stable state to determine the state of the lithium-ion battery.

[0010] According to the present invention, the state of a lithium-ion battery can be accurately determined. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1This is a block diagram illustrating a schematic configuration of an electronic device according to the first embodiment.

[0012] Figure 2 This is a diagram illustrating a lithium-ion battery to which a strain detection unit is attached.

[0013] Figure 3 This is a flowchart illustrating the full charge detection operation.

[0014] Figure 4 This is a graph illustrating the charging characteristics of a lithium-ion battery.

[0015] Figure 5 This is a flowchart illustrating the stability detection operation.

[0016] Figure 6 This is a flowchart illustrating a series of operations for determining the state of a lithium-ion battery.

[0017] Figure 7 This is a graph illustrating the temporal change in the amount of deformation of a lithium-ion battery and the timing of strain detection.

[0018] Description of Reference Signs

[0019] 100: Electronic device, 200: Main body, 206: CPU, 208: Status determination unit, 209: Charging control unit, 300: Battery unit, 301: Lithium-ion battery, 302: Distortion detection unit (deformation detection unit), 303: Voltage detection unit, 304: Current detection unit, 305: Temperature detection unit, 306: Control unit, 309: Full charge detection unit, 310: Stability detection unit, 311: Deformation acquisition unit, 400: Charger. DETAILED DESCRIPTION

[0020] Hereinafter, the embodiment of the present invention will be described with reference to the accompanying drawings. In each of the drawings, the same components are denoted by the same reference numerals, and overlapping descriptions may be omitted.

[0021] In the embodiments described below, a smartphone is exemplified as an example of an electronic device to which the present invention is applied.

[0022] <First implementation>

[0023] An electronic device according to a first embodiment of the present invention will be described below.

[0024] [Schematic Structure of Electronic Equipment]

[0025] Figure 1 This is a diagram illustrating a schematic configuration of an electronic device 100 according to the first embodiment.

[0026] Figure 1In FIG. 1 , the electronic device 100 includes a main body 200 and a battery unit 300 as a battery module. The battery unit 300 is connected to a charger 400 .

[0027] The main body 200 includes a touch panel display 201 , operation buttons 202 , a communication unit 203 , a speaker 204 , a microphone 205 , a CPU (Central Processing Unit) 206 , a storage unit 207 , and a charging control unit 209 .

[0028] The touch panel display 201 includes a display portion 201a and a touch panel 201b. The touch panel 201b is stacked on the display portion 201a.

[0029] The display unit 201 a is a display device such as a liquid crystal display or an organic EL display.

[0030] The touch panel 201b detects contact of a user's finger or the like with its surface and the position of the contact, and transmits a detection signal to the CPU 206. The detection method of the touch panel 201b can be any of a capacitance method, a resistive film method, a surface acoustic wave method, an infrared method, a load detection method, or the like.

[0031] The operation button 202 is a power button, a volume button, or the like that receives operation input from the user.

[0032] The communication unit 203 is a wireless communication module that performs wireless communication, for example, and supports communication standards such as 2G, 3G, 4G, and 5G, as well as short-range wireless communication standards.

[0033] Speaker 204 outputs the audio signal sent from CPU 206 as audio. Speaker 204 outputs, for example, the sound of animations and music played by electronic device 100, the voice of the other party during a call, etc. Microphone 25 converts the input user's voice into an audio signal and sends it to CPU 206.

[0034] The CPU 206 is a main control unit that controls each unit of the main unit 200 and the battery unit 300. The CPU 206 refers to data stored in the storage unit 207 as needed and executes commands included in programs stored in the storage unit 207. The CPU 206 implements various functions based on the data and commands.

[0035] The storage unit 207 is configured to include a memory such as a RAM (Random Access Memory) and a flash memory, etc. The storage unit 207 stores various data such as setting data and detection data, and programs.

[0036] The charging control unit 209 connects the + terminal and the - terminal of the battery unit 300 and controls the charger 400 according to the voltage and current of the battery unit 300 to charge the lithium-ion battery 301 .

[0037] The battery unit 300 includes a lithium-ion battery 301 , a strain detector 302 as a deformation amount detector, a voltage detector 303 , a current detector 304 , a temperature detector 305 , a control unit 306 , and a storage unit 307 .

[0038] The lithium-ion battery 301 is a battery pack composed of multiple connected cells, or a secondary battery consisting of a single cell. The lithium-ion battery 301 supplies power to the various components within the battery unit 300 and the main unit 200. In other words, the main unit 200 acts as a load device for the lithium-ion battery 301.

[0039] The strain detector 302 is a sensor that detects the amount of deformation of the lithium-ion battery 301. For example, a strain gauge is used as the strain detector 302, which detects the distortion of the object being measured as a change in electrical resistance. For example, the change in resistance of the strain gauge is detected by converting it into a voltage using a Wheatstone bridge circuit.

[0040] The distortion detection unit 302 is bonded to the lithium ion battery 301 via an adhesive or the like. Figure 2 As shown, when the lithium-ion battery 301 is in a flat plate shape, the distortion detection unit 302 is adhered to the surface of the lithium-ion battery 301 .

[0041] In addition, the distortion detection unit 302 is not limited to a strain gauge, and may also be a pressure sensor.

[0042] return Figure 1 The voltage detection unit 303 detects the voltage between the terminals of the lithium-ion battery 301 and outputs the voltage detection value to the control unit 306.

[0043] The current detection unit 304 is provided, for example, on a charging path between the lithium-ion battery 301 and the charger 400 . The current detection unit 304 includes a detection resistor, detects charging current and discharging current, and outputs current detection values to the control unit 306 .

[0044] The control unit 306 controls each unit in the battery unit 300. The control unit 306 refers to data stored in the storage unit 307 as needed and executes commands included in the program stored in the storage unit 307. The control unit 306 realizes various functions based on the data and commands.

[0045] The temperature detection unit 305 is a temperature sensor that detects the temperature of the lithium-ion battery 301 or its surroundings, and outputs a temperature detection value to the control unit 306 .

[0046] The storage unit 307 is configured to include a memory such as a RAM and a flash memory. The storage unit 307 stores various data such as setting data and detection data, and programs.

[0047] [Functional structure of electronic equipment]

[0048] Next, functions implemented by the CPU 206 and the control unit 306 will be described.

[0049] The control unit 306 includes, for example, a full charge detection unit 309 , a stability detection unit 310 , and a deformation amount acquisition unit 311 .

[0050] During charging of the lithium-ion battery 301 , the full charge detection unit 309 detects that the lithium-ion battery 301 is fully charged based on the voltage detection value detected by the voltage detection unit 303 and the current detection value detected by the current detection unit 304 .

[0051] After the lithium-ion battery 301 is fully charged and charging is stopped, the output voltage is stabilized by continuing the no-load or slight-discharge load state (see Figure 4 The difference (V1-V2) between the output voltage after full charge (charge voltage V1) and the output voltage when thereafter no load or a slight discharge load state is continued (open-end voltage V2) and becomes approximately constant is called overvoltage.

[0052] After the lithium-ion battery 301 is fully charged, the stability detection unit 310 detects that the battery has reached a stable state (steady state) based on the voltage detection value detected by the voltage detection unit 303 and the current detection value detected by the current detection unit 304 .

[0053] The deformation amount acquisition unit 311 acquires the deformation amount of the lithium-ion battery 301 from the distortion detection unit 302. After the deformation amount acquisition unit 311 acquires the deformation amount, it records the acquired deformation amount (acquired data) in the storage unit 307. Upon receiving a request command for the deformation amount (acquired data) from the CPU 206, the control unit 306 transmits the deformation amount (acquired data) stored in the storage unit 307 to the CPU 206.

[0054] The CPU 206 includes, for example, a state determination unit 208 .

[0055] The state determination unit 208 determines the state of the lithium-ion battery 301 based on the amount of deformation of the lithium-ion battery 301 detected by the strain detection unit 302 when the stability detection unit 310 detects a stable state.

[0056] For example, when the stability detection unit 310 detects a stable state, the state determination unit 208 instructs the deformation amount acquisition unit 311 of the control unit 306 to receive the deformation amount acquisition data acquired by the deformation amount acquisition unit 311 and store it in the storage unit 207. Each time the lithium ion battery 301 is charged, the deformation amount acquisition data acquired in the stable state is stored in the storage unit 207.

[0057] For example, when the deformation amount of the lithium-ion battery 301 is equal to or greater than a predetermined threshold, the state determination unit 208 determines that the lithium-ion battery 301 has expanded by a certain amount or more and is in an abnormal state.

[0058] When determining that the lithium ion battery 301 is in an abnormal state, the state determination unit 208 notifies the user of a message or the like indicating that the lithium ion battery 301 is in an abnormal state using the display unit 201 a and the speaker 204 .

[0059] Furthermore, even during the initial stages of manufacturing the electronic device 100, the lithium-ion battery 301 will deform. Furthermore, the amount of deformation of the lithium-ion battery 301 varies from one battery to another and varies with installation. Therefore, the state determination unit 208 records the amount of deformation detected by the distortion detection unit 302 in the aforementioned stable state, such as during the inspection process during production of the electronic device 100 or before shipment, as an initial value in the storage unit 207, and determines the threshold used for state determination based on this initial value.

[0060] Furthermore, since the deformation amount is recorded as time series data associated with the deformation amount detection time in the storage unit 207 , the state determination unit 208 can perform abnormality determination based on the event change rate of the deformation amount in addition to determination based on the magnitude of the deformation amount.

[0061] Furthermore, in this embodiment, upon obtaining the deformation amount of the lithium-ion battery 301 from the strain detection unit 302, the deformation amount acquisition unit 311 records the obtained deformation amount (acquired data) in the storage unit 307. Upon receiving a request for the deformation amount (acquired data) from the CPU 206, the control unit 306 transmits the deformation amount (acquired data) stored in the storage unit 307 to the CPU 206. The control unit 306 obtains the deformation amount of the lithium-ion battery 301 detected by the strain detection unit 302 and can transmit the acquired deformation amount data to the state determination unit 208 of the CPU 206 without receiving an instruction from the CPU 206.

[0062] [Full charge detection action]

[0063] Next, the full charge detection operation of the full charge detection unit 309 will be described in more detail.

[0064] Figure 3 This is a flowchart illustrating the full charge detection operation. Figure 4 This is a graph illustrating the charging characteristics of the lithium-ion battery 301 .

[0065] If the charging operation of the charging control unit 209 is started, Figure 3 As shown, the full charge detection unit 309 obtains the voltage detection value detected by the voltage detection unit 303 (step S10 ), and obtains the current detection value detected by the current detection unit 304 (step S11 ).

[0066] The full charge detection unit 309 determines whether the acquired voltage detection value is greater than or equal to a predetermined threshold value Vth (step S12). If the voltage detection value is greater than or equal to the predetermined threshold value Vth (step S12: Yes), the full charge detection unit 309 determines whether the current detection value is less than or equal to a predetermined threshold value Ith (step S13).

[0067] If the current detection value is determined to be less than the threshold value Ith (step S13: Yes), the full charge detection unit 309 measures time (step S14) and determines whether a predetermined time has elapsed (step S15). If the predetermined time has not elapsed (step S15: No), the full charge detection unit 309 returns the process to step S10.

[0068] If the voltage detection value is not equal to or greater than the threshold value Vth (step S12: No) and the current detection value is not less than the threshold value Ith (step S13: No), the full charge detection unit 309 resets the measurement time (step S17) and returns the process to step S10.

[0069] When a fixed time has passed (step S15: Yes), that is, when the voltage is at the threshold value Vth and the current is less than Ith for a certain period of time, the full charge detection unit 309 determines that the battery is fully charged (step S16). Here, the fixed time is, for example, a time selected from the range of 10 seconds to 1 minute.

[0070] In addition, the detection order and determination order of steps S10 to S13 are not limited to this, and can be changed as appropriate.

[0071] [Stable detection action]

[0072] Next, the stability detection operation of the stability detection unit 310 will be described in more detail. Figure 5 This is a flowchart illustrating the stability detection operation.

[0073] When the full charge detection unit 309 detects full charge, the stability detection unit 310 starts operating, sets the count (timer count) of a timer (not shown) included in the control unit 306 to 0 (zero) (step S20), and proceeds to step S21.

[0074] In step S21, the timer count is incremented by 1, and the process proceeds to step S22.

[0075] In step S22, the voltage value measured by the voltage detection unit 303 is obtained, and the process proceeds to step S23. In step S23, the current value measured by the current detection unit 304 is obtained, the current integrated capacity value is calculated, and the process proceeds to step S24.

[0076] In step S24 , the temperature measured by the temperature detection unit 305 is acquired, and the process proceeds to step S25 .

[0077] In step S25, the stability detection unit 310 determines whether the timer count is greater than the threshold value. If it is determined that the timer count is not greater than the threshold value (negative determination), the process returns to step S21. On the other hand, if it is determined that the timer count is greater than the threshold value (yes determination), the stability detection unit 310 proceeds to step S26.

[0078] In step S26, stability detection unit 310 determines whether the current value measured by current detection unit 304 is less than the threshold value. If it determines that the measured current value is not less than the threshold value (negative determination), the process proceeds to step S32. In step S32, the voltage data acquired in step S22 is stored in storage unit 307 as the previously acquired voltage data, the current integrated capacity is reset, and the process returns to step S20. On the other hand, if stability detection unit 310 determines in step S26 that the measured current value is less than the threshold value (yes determination), the process proceeds to step S27.

[0079] In step S27, the stability detection unit 310 determines whether the voltage data obtained in step S22 is the first data after the start of the stability detection operation. If it is the first data (a positive determination), the process proceeds to step S32. On the other hand, if the stability detection unit 310 determines that it is not the first data (a negative determination), the process proceeds to step S28.

[0080] In step S28 , the stability detection unit 310 calculates and determines the threshold value of the voltage change rate based on the temperature measured in step S24 , and then proceeds to step S29 .

[0081] In step S29, the stability detection unit 310 calculates the voltage change rate based on the previously acquired voltage data and the currently acquired voltage data stored in the storage unit 307, and compares the calculated voltage change rate with the voltage change rate threshold value determined in step S28. If the stability detection unit 310 determines that the voltage change rate is not less than the threshold value (negative determination), the processing proceeds to step S32. On the other hand, if the stability detection unit 310 determines that the voltage change rate is less than the threshold value (yes determination), the processing proceeds to step S30.

[0082] In step S30, stability detection unit 310 determines whether the current integrated capacity value calculated in step S23 is less than the threshold value. If it is determined that the current integrated capacity value is not less than the threshold value (negative determination), the process proceeds to step S32. On the other hand, if it is determined that the current integrated capacity value is less than the threshold value (yes determination), stability detection unit 310 determines that the state is stable (step S31).

[0083] In addition, the detection order and determination order of steps S20 to S32 are not limited to this, and can be changed as appropriate.

[0084] Furthermore, a secondary battery remaining capacity meter disclosed in Japanese Patent Application Laid-Open No. 2011-169817 can be applied as the stability detection unit 310. The stable state can be detected based on the rate of change of the remaining capacity (charging rate).

[0085] [Lithium-ion battery status determination operation]

[0086] Next, a series of operations related to the state determination of the lithium-ion battery 301 will be described in more detail.

[0087] Figure 6 This is a flowchart illustrating a series of operations for determining the state of the lithium-ion battery 301 .

[0088] Figure 6 In the process, the CPU 206 determines whether the charging operation has been started by the charging control unit 209 (step S40). If the charging operation has been started (step S40: Yes), the full charge detection unit 309 performs a full charge detection operation (step S41).

[0089] If the full charge detection unit 309 detects full charge (step S41 : Yes), the stable state detection unit 310 performs a stable state detection operation (step S42 ).

[0090] If the stability detector 310 detects a stable state (step S42 : Yes), the state determination unit 208 obtains the deformation of the lithium ion battery 301 detected by the distortion detector 302 via the deformation acquisition unit 31 (step S43 ), and determines the state of the lithium ion battery 301 (step S44 ).

[0091] Then, CPU 206 determines whether a predetermined termination condition is satisfied (step S45 ). If the termination condition is satisfied (step S45 : YES), the operation is terminated. On the other hand, if the termination condition is not satisfied (step S45 : NO), CPU 206 returns the process to step S40 .

[0092] [Time change of deformation]

[0093] Figure 7 3 is a graph illustrating the temporal change in the amount of deformation of the lithium-ion battery 301 and the timing of strain detection.

[0094] The lithium-ion battery 301 shows a tendency in which the amount of deformation increases with charge and decreases with discharge because the internal laminate expands during charge.

[0095] Furthermore, the average deformation of the lithium-ion battery 301 tends to increase over time due to variations in temperature. This can be caused by, for example, aging during charge and discharge cycles, leaving the electronic device 100 at high temperatures, or dropping the electronic device 100.

[0096] As described above, the amount of deformation of the lithium-ion battery 301 increases as a whole due to aging while repeating the increase and decrease associated with charge and discharge.

[0097] In the electronic device 100 of this embodiment, the state is determined based on the deformation amount detected by the strain detection unit 302 in the stable state after full charge. Therefore, the influence of the increase or decrease in the deformation amount caused by charging and discharging can be suppressed, and the state of the lithium-ion battery 301 can be accurately determined.

[0098] In addition, it is also considered to perform deformation detection when the lithium-ion battery 301 is fully charged. However, during the period from full charging to the stable state, the temperature and battery voltage fluctuate, which becomes the main cause of deformation of the lithium-ion battery 301. Therefore, the accuracy of the state judgment is improved by using the deformation amount detected in the stable state.

[0099] Furthermore, in the state determination, since the threshold value is set based on the initial value, it is possible to suppress erroneous determinations due to individual differences in the lithium-ion batteries 301 and installation variations.

[0100] In addition, in the first embodiment, the distortion detection unit 302 performs distortion detection only in the stable state. However, regardless of whether the state is stable or not, the distortion detection unit 302 periodically detects the deformation amount and records it in the storage unit. The state determination unit 208 obtains the deformation amount detected in the stable state from the storage unit based on the stable state determination result.

[0101] Therefore, the electronic device according to the present invention determines the state of the lithium-ion battery 301 based on the result of determining the stable state of the fully charged lithium-ion battery 301 and the deformation amount of the lithium-ion battery 301 detected in the stable state.

[0102] Furthermore, the deformation amount used for state determination by the state determination unit 208 may not be acquired simultaneously with the time when the stable state is detected by the stability detection unit 310 , but may be detected after the stable state is detected and while the stable state continues to be obtained.

[0103] In addition, in the above embodiment, the control unit 306 is provided in the battery unit 300 , but the control unit 306 may also be provided in the main body unit 200 .

[0104] Furthermore, in the above embodiment, the CPU 206 and the control unit 306 are provided separately, but these may be constituted by a single arithmetic processing circuit.

[0105] In the above embodiment, the full charge detection unit 309 , the stability detection unit 310 , and the deformation amount acquisition unit 311 are provided in the control unit 306 , but they may be provided in the CPU 206 .

[0106] In addition, in the above embodiment, the state determination unit 208 notifies the abnormal state when determining that the lithium-ion battery 301 is in an abnormal state, but in addition to or instead of this, when it is determined to be an abnormal state, a command is given to the charging control unit 209 to change the charging method and charging conditions.

[0107] Furthermore, in the above-described embodiment, a smartphone is described as an example of an electronic device. However, the present invention is not limited to smartphones and can be applied to various electronic devices.

[0108] Although preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various modifications and substitutions can be added to the above embodiments without departing from the scope of the present invention.

Claims

1. An electronic device, characterized in that: The electronic device has: Secondary batteries; a deformation amount detecting unit configured to detect the deformation amount of the secondary battery; a full charge detection unit for detecting whether the secondary battery is fully charged; a stable state detecting unit for detecting a stable state after the full charge detecting unit detects full charge; as well as a state determination unit that determines the state of the secondary battery using the deformation amount detected by the deformation amount detection unit when the stability detection unit detects the stable state; When the voltage detection value reaches the predetermined voltage threshold and the current detection value is less than the predetermined current threshold for a certain period of time, the full charge detection unit determines that full charge has been achieved. The stability detection unit calculates the current integrated capacity based on the current detection value in the fully charged state. When the timer count is equal to or greater than a count threshold, the stability detection unit resets the current integrated capacity based on a current detection value that is not less than a stability detection current threshold or a voltage detection value determined to be an initial value after the start of the stability detection operation. The stability detection unit determines that the state is the stable state when the voltage change rate and the current integrated capacity after full charge are less than a predetermined voltage change rate threshold value and a predetermined current integrated capacity threshold value, respectively.

2. The electronic device according to claim 1, wherein When the magnitude of the deformation exceeds a predetermined deformation threshold, the state determination unit determines that the state is abnormal.

3. The electronic device according to claim 2, wherein: When the stable state is detected, the state determination unit records the deformation amount detected by the deformation amount detection unit as an initial value, and determines the deformation amount threshold value based on the initial value.

4. The electronic device according to claim 2, wherein: The state determination unit performs the state determination based on not only the magnitude of the deformation but also a time rate of change of the deformation.

5. The electronic device according to claim 1, wherein The deformation amount detecting unit is a strain gauge or a pressure sensor.

6. A method for controlling an electronic device comprising a secondary battery and a deformation detection unit for detecting deformation of the secondary battery, wherein: The method comprises the following steps: a full charge detection step of detecting whether the secondary battery is fully charged; After the full charge is detected, a stabilization detection step of detecting a stable state; and a state determination step of determining the state of the secondary battery using the deformation amount detected by the deformation amount detection unit when the stable state is detected; When the voltage detection value reaches the predetermined voltage threshold and the current detection value is less than the predetermined current threshold for a certain period of time, it is determined that full charge has been achieved. In the above-mentioned stable detection step, the current integrated capacity is calculated based on the current detection value in the fully charged state. In the stability detection step, when the timer counts to a count threshold or more, the current integrated capacity is reset based on a current detection value that is not less than the stability detection current threshold or a voltage detection value determined to be the first data after the start of the stability detection operation. When the voltage change rate and the current integrated capacity after full charge are less than a predetermined voltage change rate threshold value and a predetermined current integrated capacity threshold value, respectively, the stable state is determined.

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