JP2007300738A - Electronic equipment having secondary battery, and charge control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid a secondary battery, exposed to high temperature with a high voltage which becomes severe conditions for secondary batteries, through a simple construction, when the secondary battery is charged, and thereby reducing degradation in the service life of the secondary battery. <P>SOLUTION: A control circuit section 101 determines functions during operation and refers to a table, in which the functions in operation and charging voltages are brought into correspondence with each other, to determine the charging voltage. A power supply circuit 107 charges a lithium-ion battery 109 with the charging voltage, and accordingly the lithium-ion battery 109 is charged, while avoiding its being exposed to high temperature, at a high voltage. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electronic device having a secondary battery as a power source, such as a portable electronic device such as a mobile phone, a personal handyphone system (PHS), and a PDA with a communication function (personal digital assistant). The present invention relates to a charge control method for a secondary battery.

Conventionally, a secondary battery such as a lithium ion battery has been used as a power source in an electronic device such as a mobile phone, a PHS, and a PDA, and the secondary battery is well charged. Various charging methods have been developed to perform the above (for example, see Patent Documents 1 and 2).
As lithium ion batteries are repeatedly charged and used, the characteristics gradually deteriorate and the usable capacity decreases. The cause of this characteristic deterioration is the internal pressure of the battery, and the higher the pressure, the faster the characteristic deterioration. The internal pressure of the lithium ion rechargeable battery varies depending on the voltage and temperature. The higher the voltage and temperature, the higher the internal pressure and the accelerated characteristic deterioration.

  On the other hand, the central processing unit (CPU) mounted by the multifunctional and high performance of the portable information terminal represented by the mobile phone has also been improved in performance, and the main body generates heat when high load processing is continued. Is getting pretty expensive. As a result, when a user performs an operation such that high-load processing continues on a portable information terminal and the lithium-ion battery is charged at the same time, it is severe for a lithium-ion battery having a high voltage and high temperature. This is one of the factors that accelerate the deterioration of battery life.

  By the way, Patent Document 1 discloses an invention in which a charging operation is performed so that the mobile communication terminal does not generate excessive heat. However, the invention described in Patent Document 1 uses a dedicated temperature sensor for charge control, and controls the charge current based on the expected temperature after a predetermined time, the current consumption current, the function used, and the like. The charging operation is controlled in small increments. Therefore, there is a problem that the configuration becomes extremely complicated.

Moreover, in invention of patent document 1, it is an invention which is going to suppress heat_generation | fever and it charges while avoiding being exposed to high temperature in the high voltage state used as a severe condition for secondary batteries, such as a lithium ion battery. Therefore, it is not made from the viewpoint of reducing the deterioration of the life of the secondary battery.
Patent Document 2 also describes an invention in which a secondary battery of a portable telephone is charged by selecting either slow charge or quick charge, and was made from the above viewpoint. It is not a thing.

JP 2006-20446 A JP-T-2001-506109

  An object of the present invention is to reduce the lifetime deterioration of a secondary battery by charging while avoiding exposure to a high temperature in a high voltage state, which is a severe condition for the secondary battery, with a simple configuration. .

According to the present invention, there is provided a secondary battery, and a control unit that discriminates a function during operation and controls a charging voltage for the secondary battery to a voltage corresponding to the function during operation. An electronic device having the secondary battery is provided.
The control means discriminates the function during operation of the electronic device and controls the charging voltage for the secondary battery to a voltage corresponding to the function during operation.

Here, a storage unit that stores a voltage control table in which a function and a charging voltage are associated with each other is stored, and the control unit refers to the voltage control table and determines the charging voltage for the secondary battery as the operation. You may comprise so that it may control to the voltage according to an inside function.
Further, a temperature sensor may be provided, and the control unit may be configured to control a charging voltage for the secondary battery based on the function during operation and the temperature detected by the temperature sensor.

In addition, a predetermined function and a charging voltage are associated with each other, and a voltage control table storing a function other than the predetermined function and a function of determining a charging voltage based on a temperature detected by the temperature sensor is stored. Storage means, and when the predetermined function is operating, the control means controls the charging voltage so as to be a voltage associated with the voltage control table, and other than the predetermined function. When the function is in operation, the charging voltage may be controlled based on the temperature detected by the temperature sensor.
In addition, the temperature sensor includes a wireless circuit unit for wirelessly transmitting a signal to the outside, and the temperature sensor is used for correcting the power of a signal wirelessly transmitted from the wireless circuit unit to the outside. You may comprise so that it is.

In addition, the liquid crystal display device and a backlight for illuminating the liquid crystal display device, the control means is configured to control the charging voltage based on whether the backlight is lit. May be.
The control unit may be configured to control a charging voltage for the secondary battery by selecting one of the first voltage and the second voltage lower than the first voltage.
The secondary battery may be a lithium ion battery.

Further, according to the present invention, the function during operation of the electronic device is determined, the voltage control table in which the function is associated with the charge voltage is referred to, and the charge voltage for the secondary battery is changed to the function during operation. There is provided a charge control method for a secondary battery of an electronic device, characterized in that the voltage is controlled in accordance with the voltage.
A function during operation of the electronic device is determined, and a charging voltage for the secondary battery is controlled to a voltage corresponding to the function during operation by referring to a voltage control table in which the function and the charging voltage are associated with each other.

Here, when the predetermined function is in operation, the charging voltage is controlled to be a voltage associated with the voltage control table, and when other functions other than the predetermined function are in operation. The charging voltage may be controlled based on a temperature detected by a temperature correction temperature sensor used to correct the power of a signal wirelessly transmitted from the wireless circuit unit of the electronic device to the outside. .
Moreover, you may comprise so that the said charging voltage may be controlled based on whether the backlight for display apparatuses of the said electronic device is lighted.

According to the electronic apparatus having the secondary battery according to the present invention, the secondary battery can be charged with a simple configuration while avoiding exposure to high temperature in a high voltage state which is a severe condition for the secondary battery. It becomes possible to reduce the life deterioration of the.
In addition, according to the method for controlling charging of a secondary battery of an electronic device according to the present invention, charging is performed while avoiding exposure to a high temperature in a high voltage state, which is a severe condition for the secondary battery, by simple control. Therefore, it becomes possible to reduce the lifetime deterioration of the secondary battery.

FIG. 1 is a block diagram of an electronic apparatus having a secondary battery according to an embodiment of the present invention, which is a block diagram commonly used in first to third embodiments described later, and is an example of a mobile phone Is shown.
In FIG. 1, a control circuit unit 101 is composed of a central processing unit (CPU) and a memory (not shown) as storage means, and controls various devices mounted on the mobile phone. Implement various functions. A liquid crystal display (LCD) 102 displays various information (operation menu, phone book, time, etc.) as a mobile phone.

The operation unit 103 is a key switch group for operating the mobile phone, and an input from the operation unit 103 is processed by the control circuit unit 101 to perform an operation as a mobile phone terminal. The voice circuit unit 104 is controlled by the control circuit unit 101 to process voice, and a voice call as a mobile phone is performed using the microphone 105 and the speaker 106.
The power supply circuit unit 107 has a function of supplying power from the lithium ion battery 109 to each part of the mobile phone as necessary, and a function of charging the lithium ion battery 109 when an alternating current (AC) adapter 108 is connected. have. The power supply circuit unit 107 includes a high voltage charging mode in which charging is performed until the battery voltage recovers to a first predetermined voltage (for example, 4.4 V), and until the battery voltage recovers to a second predetermined voltage (for example, 4.2 V). Two types of charging modes, a low voltage charging mode for charging, are provided, and the two types of charging modes can be switched by control from the control circuit 101.

The lithium ion battery 109 is a lithium ion battery as a secondary battery generally used for a mobile phone or the like. The camera 110 is a digital camera composed of a C-MOS or a CCD, and is used for taking a digital photograph or a TV phone.
The wireless circuit unit 111 performs wireless communication as a mobile phone terminal with the mobile phone base station via the antenna 112.

The wireless circuit unit 111 has a temperature sensor 113 inside. The temperature sensor 113 is a temperature sensor for temperature correction that is used to correct the power of a signal that is wirelessly output from the wireless circuit unit 111. As will be described later, the temperature sensor 113 also serves as a temperature sensor for charge control. The backlight 114 is a light source for irradiating the LCD display device 102.
The temperature sensor 113 is also used when determining the charging voltage in the second embodiment to be described later. The backlight 114 is also used for determining the charging voltage in the third embodiment to be described later. Further, the control circuit unit 101 and the power supply circuit unit 107 constitute a control unit.

FIG. 2 lists the functions of the mobile phone having the secondary battery according to the embodiment of the present invention. From the CPU load in each function and the continuity of operation of the operation unit 103, FIG. It is the table which showed the result of estimating the heat generation condition, and is a table in which the cellular phone function, CPU processing load, continuity of operation, and the estimation result of the calorific value of the cellular phone are associated.
In FIG. 2, the functions of the mobile phone are roughly classified into a non-communication function and a communication function.
Non-communication functions include a mail creation function, a mail browsing function, a camera (still image and moving image) shooting function, a still image reproduction function, a moving image reproduction function, a game function, and a music reproduction function. Communication functions include a standby function, a voice call function, a TV (TV) telephone function, a mail transmission / reception function, and a data communication function.

  The processing load of the CPU (that is, the control circuit unit 101) when executing each function is divided into three types: large, medium, and small. Regarding the continuity of operation, the function that the operation is normally performed for a predetermined time or longer is expressed as “continuous”, and the operation that is normally not performed for the predetermined time or longer is “single”. It expresses. The heat generation amount estimation of the device (mobile phone) is performed by estimating the heat generation amount of the device (mobile phone) based on the CPU processing load and the continuity of operation for each function, and the estimated heat generation amount is equal to or greater than a predetermined amount. In this case, “large heat generation” is indicated, and when the estimated heat generation amount is less than the predetermined amount, “no heat generation” is indicated. By referring to the table of FIG. 2, it is possible to determine whether the amount of heat generation is large or no heat generation for each function of the mobile phone.

FIG. 3 is a voltage control table used in the first embodiment of the present invention.
The voltage control table of FIG. 3 is based on the estimated heat generation amount for each function of the mobile phone shown in FIG. Is a table that defines whether to use a low voltage charging mode (a mode in which charging is performed using a second voltage lower than the first voltage by a predetermined voltage). In the example of FIG. 3, a table in which each function of the mobile phone is associated with a charging voltage (the first voltage (high voltage) and the second voltage (constant voltage)) divided into a non-communication function and a communication function; It has become. The voltage control table is stored in advance in the memory in the control circuit unit 101.

  The control circuit unit 101 discriminates the function in operation, refers to the voltage control table in FIG. 3 in which the function in operation is associated with the charge voltage, and determines the charge voltage according to the function in operation. Then, the power supply circuit unit 107 is controlled to a high voltage charging mode in which the power supply circuit unit 107 is charged with the first voltage or a low voltage charging mode in which the power supply circuit unit 107 is charged with the second voltage lower than the first voltage by a predetermined voltage. The power supply circuit unit 107 charges the lithium ion battery 109 with the determined voltage (the first voltage or the second voltage).

In the first embodiment, in order to extend the life of the lithium ion battery 109, the heat generation temperature of the mobile phone is estimated from the operation status of the mobile phone without using a temperature sensor, and the operation status of the mobile phone is changed. The charging voltage is switched accordingly.
That is, the control circuit unit 101 determines a function in operation among a plurality of functions of the mobile phone, and controls the charging voltage for the lithium ion battery 109 according to the function. At this time, the control circuit unit 101 refers to the table of FIG. 3 in which the function and the charging voltage are stored in the memory in the control circuit unit 101 and refers to the charging voltage corresponding to the function in operation. Control to charge by.

  Accordingly, the lithium ion battery 109 can be determined by an appropriate charging voltage with a simple configuration in which the function in operation is discriminated and the charging voltage corresponding to the function in operation is selected with reference to the voltage control table of FIG. Can be charged. Further, by recognizing the heat generating operation, it is possible to charge the lithium ion battery in which the temperature is estimated in the operation state and the maximum charging voltage is controlled according to the temperature without newly adding a thermometer. Therefore, the lithium ion battery 109 can be prevented from being exposed to a high temperature in a high voltage state, which is a severe condition, and the life deterioration of the lithium ion battery 109 can be reduced. Further, the charging voltage is controlled by selecting one of a plurality of predetermined voltages (two voltages of the first voltage and the second voltage in the present embodiment) as the charging voltage. Therefore, the configuration is simple.

FIG. 4 is a voltage control table used in the second embodiment of the present invention, and is stored in the memory in the control circuit unit 101 in advance.
In the first embodiment, the function in operation is discriminated and a charging voltage corresponding to the function in operation is selected with reference to the voltage control table of FIG. In the second embodiment, the temperature sensor 113 in FIG. 1 is used and the voltage control table in FIG. 4 is used to determine the charging voltage and control the charging. It is configured.

As described above, the temperature sensor 113 is not a dedicated temperature sensor newly provided for measuring the temperature of the lithium ion battery 109, but is originally used for temperature correction of the transmission signal power of the wireless circuit unit 111 in the mobile phone. The temperature sensor is also used for charging voltage control.
Since the temperature sensor 113 is originally a temperature sensor for another use and is located away from the lithium ion battery 109, the temperature of the lithium ion battery 109 itself cannot be measured accurately. While using a table, the temperature sensor 113 is used supplementarily to determine the charging voltage.

In FIG. 4, the functions of the mobile phone are divided into a non-communication function and a communication function, as in the first embodiment.
Regarding the communication function (in the example of FIG. 4, the standby function, the voice call function, the videophone function, the mail transmission / reception function, and the data communication function), the temperature sensor 113 is originally a temperature sensor for the wireless circuit unit 111. Therefore, the heat generation of the wireless circuit unit 111 can be accurately measured. Therefore, by determining the output value of the temperature sensor 113 with an appropriate threshold value in the communication function activated state and determining whether the charging voltage is set to the high voltage mode or the low voltage mode, the battery 109 becomes hot. It is possible to determine whether the communication is for a long time or for a short time that the temperature of the battery 109 will not rise, and the charging voltage can be switched accurately.

Regarding the non-communication function, the control circuit unit 101 controls to perform charging with a high voltage that is the first voltage for a predetermined function (in the example of FIG. 4, no operation state, mail creation function, mail browsing function). To do.
For non-communication functions other than the predetermined function (in the example of FIG. 4, camera shooting function, still image playback function, video playback function, game function, music playback function), when the temperature detected by the temperature sensor 113 is equal to or higher than the predetermined temperature Is charged with a second voltage that is lower than the first voltage by the second voltage, and the control circuit unit 101 controls charging by the first voltage when the temperature detected by the temperature sensor 113 is lower than the predetermined temperature.

In this case, since the temperature sensor 113 is originally a temperature sensor for the wireless circuit unit 111, the temperature sensor 113 cannot accurately detect the heat generated by the device or the battery 109 itself. However, it is known that although it is far away, it is a temperature sensor that exists in the same device, and therefore outputs a higher temperature within a range of about 20 ° C. relative to the temperature of the battery 109.
When the charging voltage is switched to the low voltage mode when the battery 109 is 40 ° C. or higher, and the voltage determination threshold value by the temperature sensor 113 during the non-communication function is set to 40 ° C., the temperature of the battery 109 is 20 ° C. to 40 ° C. The charging voltage can be switched to the low voltage mode at a temperature lower than 40 ° C. which is originally desired to be switched.

In the second embodiment of the present invention, the temperature sensor 113 for temperature correction used for correcting the power of the signal output wirelessly from the wireless circuit unit 111 is provided, and the control circuit unit 101 is in operation. The charging voltage for the lithium ion battery 109 is controlled based on the function and the temperature detected by the temperature sensor 113.
4 has the memory for storing the voltage control table in FIG. 4 in which the function in operation and the charging voltage are associated with each other, and the control circuit unit 101 controls the voltage control when a predetermined function is in operation. The charging voltage is controlled so as to correspond to the table, and when the other functions are operating, the charging voltage is controlled based on the temperature detected by the temperature sensor.

  That is, a voltage control table that associates a predetermined function with a charging voltage and stores a function other than the predetermined function and that determines a charging voltage based on a temperature detected by the temperature sensor 113 is stored in the memory. And the control circuit unit 101 controls the charging voltage so as to be a voltage associated with the voltage control table when the predetermined function is in operation, and functions other than the predetermined function. Is operating, the charging voltage is controlled based on the temperature detected by the temperature sensor 113.

  Thus, compared with the case where the charging voltage is simply switched according to the function as in the first embodiment, the accuracy is not required, but the temperature sensor 113 is used as an auxiliary, so that it is not necessary at an obvious low temperature. The charging voltage is not switched to the low voltage mode. In addition, if the determination is made only with the temperature sensor 113, it is inevitable to switch to the low voltage mode at a temperature considerably lower than the target temperature. In general, the high voltage mode can be used in an operation state where the heat generation is considered to be obviously low.

  Therefore, the lithium ion battery 109 can be charged with an appropriate charging voltage with a simple configuration. Further, it is possible to charge the lithium ion battery in which the maximum charging voltage is controlled according to the function and temperature during operation, and it is possible to reduce the life deterioration of the lithium ion battery 109. In addition, since a dedicated temperature sensor is not used, the configuration is simple and the cost is reduced.

  FIG. 5 is a voltage control table used in the third embodiment of the present invention, and is stored in advance in the memory in the control circuit unit 101. The voltage control table in FIG. 5 includes the functions of the mobile phone, the processing load of the CPU constituting the control circuit unit 101, the lighting state of the backlight 114 in FIG. 1 (lights up during operation of the operation unit 103, operates the operation unit 103) During this period, the light is turned off and continuously lit), and the charging voltage for the lithium ion battery 109 (a predetermined first voltage (high voltage), a second voltage lower than the first voltage by a predetermined voltage) is associated.

In FIG. 1, the backlight 114 of the LCD display device 102 is turned on when the control circuit unit 101 detects the operation of the operation unit 103. In this way, the backlight 114 is turned on when the operation unit 103 is operated, thereby ensuring the visibility of the LCD display device 102. Basically, when the operation unit 103 has not been operated for a predetermined time or longer, the control circuit unit 101 determines that the operation unit 103 is not operated and turns off the backlight 114 to perform power saving control.
As shown in FIG. 5, for some functions, even when the operation of the operation unit 103 has not been performed for a predetermined time or longer, the control circuit unit 101 is operating the function while the function is in operation. Therefore, the backlight 114 is controlled so that the backlight 114 is continuously turned on.

  In the second embodiment, the temperature sensor 113 and the voltage control table in FIG. 4 are used to determine the charging voltage, and the lithium ion battery 109 is charged with the voltage. In the third embodiment, the operation state of the backlight 114 is used, and the charging voltage is determined using the voltage control table of FIG. 5 to control the charging.

  That is, in the third embodiment, the condition for the control circuit unit 101 to determine and control the charging voltage is simplified, and the charging voltage is determined based on the ON / OFF state of the backlight 114 of the LCD display device 102. It is configured to make a decision. When the control circuit unit 101 refers to the voltage control table of FIG. 5 and determines that the backlight 114 is not turned on, the control circuit unit 101 controls charging of the lithium ion battery 109 with the first voltage that is a predetermined high voltage. When it is determined that the backlight 114 is lit, the charging control of the lithium ion battery 109 is performed with a second voltage that is lower than the first voltage by a predetermined voltage.

  Thus, according to the third embodiment, the LCD display device 102 and the backlight 114 that illuminates the LCD display device are provided, and the control circuit unit 101 determines whether or not the backlight 114 is lit. Since the charging voltage of the lithium ion battery 114 is controlled based on the above, it is possible to charge the lithium ion battery 109 with an appropriate charging voltage with a simple configuration. In addition, since only the lighting state of the backlight 114 is detected and no dedicated sensor is used, the structure is simple and the cost is reduced.

In addition, according to the method for controlling charging of a secondary battery of an electronic device according to an embodiment of the present invention, it is possible to avoid exposure to high temperatures in a high voltage state that is a severe condition for the secondary battery with a simple configuration. By charging the battery while it is charged, it is possible to reduce the life deterioration of the secondary battery.
In the above embodiment, an example of a mobile phone is given as an electronic device having a secondary battery. However, the present invention is applicable to various electronic devices having a secondary battery as a power source, including portable electronic devices such as PHS and PDA. Is possible.
Moreover, although the lithium ion battery was used as a secondary battery, it is applicable to a secondary battery whose characteristics deteriorate due to pressure or heat.

  The present invention is applicable to portable electronic devices such as mobile phones, PHS, and PDAs, and electronic devices that use a secondary battery as a power source.

1 is a block diagram of a mobile phone according to an embodiment of the present invention. It is a table for demonstrating operation | movement of the mobile telephone which concerns on embodiment of this invention. It is a voltage control table used for the mobile phone according to the first embodiment of the present invention. It is a voltage control table used for the mobile phone according to the second embodiment of the present invention. It is the table for voltage control used for the mobile telephone which concerns on the 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 ... Control circuit part 102 which comprises control means ... Liquid crystal display device 103 ... Operation part 104 which comprises operation means ... Voice circuit part 105 ... Microphone 106 ... Speaker 107 ... Power supply circuit unit 108 constituting the control means ... AC adapter 109 ... secondary battery lithium ion battery 110 ... camera 111 ... radio circuit unit 112 ... antenna 113 ... temperature sensor 114 ... Backlight

Claims (11)

  A secondary battery comprising: a secondary battery; and a control unit that determines a function during operation and controls a charging voltage for the secondary battery to a voltage corresponding to the function during operation. Electronic equipment that has. Storage means for storing a voltage control table in which functions and charging voltages are associated with each other;
2. The secondary battery according to claim 1, wherein the control unit controls a charging voltage for the secondary battery to a voltage corresponding to the function during the operation with reference to the voltage control table. Electronics. Have a temperature sensor,
The electronic device having a secondary battery according to claim 1, wherein the control unit controls a charging voltage for the secondary battery based on the function in operation and the temperature detected by the temperature sensor. Storage means for storing a voltage control table that associates a predetermined function with a charging voltage and stores a function other than the predetermined function and determining a charging voltage based on a temperature detected by the temperature sensor Have
When the predetermined function is in operation, the control unit controls the charging voltage so as to be a voltage associated with the voltage control table, and a function other than the predetermined function is in operation. The electronic device having a secondary battery according to claim 3, wherein the charging voltage is controlled based on a temperature detected by the temperature sensor.   The temperature sensor is a temperature sensor for temperature correction used for correcting the power of a signal wirelessly transmitted from the wireless circuit unit to the outside. An electronic device having the secondary battery according to claim 3 or 4. A liquid crystal display device, and a backlight for illuminating the liquid crystal display device,
The electronic device having a secondary battery according to claim 1, wherein the control unit controls the charging voltage based on whether or not the backlight is lit.   The control unit controls a charging voltage for the secondary battery by selecting one of a first voltage and a second voltage lower than the first voltage. An electronic device comprising the secondary battery according to any one of the above.   The electronic device having a secondary battery according to any one of claims 1 to 7, wherein the secondary battery is a lithium ion battery.   It is possible to determine a function during operation of the electronic device, refer to a voltage control table in which the function and the charging voltage are associated, and control the charging voltage for the secondary battery to a voltage according to the function during the operation. A charge control method for a secondary battery of an electronic device.   When the predetermined function is in operation, the charging voltage is controlled to be a voltage associated with the voltage control table, and when other functions other than the predetermined function are in operation, the electronic 10. The charging voltage is controlled based on a temperature detected by a temperature sensor for temperature correction used for correcting power of a signal wirelessly transmitted to the outside from a radio circuit unit of the device. Charge control method for secondary battery of electronic device.   10. The method for controlling charging of a secondary battery of an electronic device according to claim 9, wherein the charging voltage is controlled based on whether or not a backlight for a display device of the electronic device is turned on.

Images