JP2006275549A - Information terminal and calculation method of battery power - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an information terminal capable of displaying a battery power in which effect of load variation is corrected. <P>SOLUTION: A ROM 34 stores a correspondence table between the battery power and the battery voltage, for a prescribed battery temperature and the magnitude of the load current. A voltage detection circuit 40 detects the battery voltage. A temperature detection circuit 42 detects the battery temperature. A CPU 10 acquires an operational mode of the information terminal, wherein the magnitude of the load current corresponding to the operational mode is calculated. An interpolation table is created by the interpolation in which the correspondence table stored in the ROM 34 is related to the battery temperature and the load current. In the created interpolation table, the battery power corresponding to the battery voltage detected by the voltage detection circuit 40 is acquired. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an information terminal having a function of detecting a remaining battery level and a battery remaining amount calculating method.

  An increasing number of small information terminals using batteries handle still images and moving images. An increasing number of such small information terminals are equipped with devices such as hard disk drives that have a large effect on load fluctuations. Depending on the driving state of such a device, the load on the battery is greatly fluctuating.

  In order to estimate how much the information terminal can be used, an accurate display of the remaining battery level is very important. As a method for detecting the remaining battery level, a method for measuring the charge / discharge current of the battery is disclosed (for example, see Patent Documents 1 and 2). Further, a method for measuring battery voltage is disclosed (for example, see Patent Documents 3 and 4).

Japanese Patent Laid-Open No. 5-66251 JP 7-260839 A JP-A-6-51876 Japanese Patent Laid-Open No. 11-55372

  However, the method for measuring the charge / discharge current requires a current measurement unit, a storage unit for storing the measured current data, and a CPU for calculating the remaining battery capacity from the data, which hinders downsizing and cost reduction. To do. Therefore, it is not suitable for a small information terminal.

  On the other hand, in the method of measuring the battery voltage, the external voltage changes due to the internal impedance when the load fluctuates as the characteristics of the battery. For this reason, an information terminal incorporating a device with a large load fluctuation cannot accurately detect the remaining battery level. For example, since the load becomes large when the information terminal is turned on, the remaining battery level is displayed low. After that, when the information terminal is stabilized, the load is reduced and the remaining battery level is increased.

  Therefore, in an information terminal incorporating a device with a large load fluctuation, the remaining battery level detected each time the battery voltage is measured changes, so the detected remaining battery level tends to be inaccurate. Since the display of the remaining battery level is inaccurate as described above, the remaining battery level cannot be properly confirmed, and the remaining battery level cannot be properly managed by charging or the like.

  Further, when the influence of load fluctuation is corrected by a method of measuring and correcting the current flowing through the load, it is necessary to further prepare components such as a current detection unit and a comparison voltage correction unit, resulting in an increase in cost. Furthermore, insertion of a current detection resistor in the power supply line causes a voltage drop and wasteful power consumption, resulting in a problem that the driving time by the battery is shortened.

  An object of the present invention is to provide an information terminal and a battery remaining amount calculation method capable of displaying the remaining battery level corrected for the influence of load fluctuations, in order to solve the above-described problems caused by the prior art.

  In order to solve the above-described problems, an information terminal according to the present invention includes a first storage unit that stores a correspondence table of a remaining battery level and a battery voltage with respect to a predetermined battery temperature and load current, and an information terminal A second storage means for storing a correspondence table representing a relationship between a plurality of operation modes representing an operation state and a load current corresponding to each operation mode; a voltage detection means for detecting a battery voltage; and a battery Temperature detection means for detecting temperature; acquisition means for acquiring an operation mode corresponding to the information terminal among the plurality of operation modes; and a magnitude of a load current corresponding to the operation mode acquired by the acquisition means. By interpolating the load calculation means calculated from the second storage means and the correspondence table stored in the first storage means in correspondence with the battery temperature and the load current. Interpolating means for creating an interval table, and remaining amount calculating means for obtaining a remaining battery level corresponding to the battery voltage detected by the voltage detecting means using the interpolation table created by the interpolating means. Features.

  The first storage means includes a plurality of correspondence tables corresponding to the size of the battery temperature, and the interpolation means uses the plurality of correspondence tables to determine the battery temperature detected by the temperature detection means. A corresponding interpolation table may be created.

  Further, the first storage means includes a plurality of correspondence tables for the magnitude of the load current, and the interpolation means uses the plurality of correspondence tables to perform interpolation corresponding to the load current calculated by the load calculation means. A table may be created.

  The first storage unit includes a correspondence table that represents a load current corresponding to each combination of operation modes, and the load calculation unit includes a plurality of operation modes acquired by the acquisition unit. If included, the load current may be calculated from the correspondence table.

  A battery remaining amount calculating method according to the present invention is a battery remaining amount calculating method for an information terminal that stores a correspondence table of a remaining battery amount and a battery voltage for a predetermined battery temperature and load current magnitude. An acquisition step for acquiring a voltage, a battery temperature and an operation mode of the information terminal, a load calculation step for calculating a magnitude of a load current corresponding to the operation mode, and the correspondence corresponding to the battery temperature and the load current An interpolation step of creating an interpolation table by interpolating the table, and a remaining amount calculation step of obtaining a remaining battery level corresponding to the battery voltage acquired by the acquisition step in the interpolation table created by the interpolation step. It is characterized by including.

  Exemplary embodiments of an information terminal and a battery remaining amount calculation method according to the present invention will be described below in detail with reference to the accompanying drawings.

  FIG. 1 is a block diagram for explaining an example of the configuration of the information terminal of this embodiment. As shown in FIG. 1, the information terminal includes a CPU 10, an LCD backlight 12, an HDD (hard disk drive) 14, and a display unit 18.

  The information terminal includes a battery 20, and power supplied from the battery 20 is supplied to the drive unit via the DC / DC converter 22. That is, power is supplied to the CPU 10, the LCD backlight 12, the hard disk drive 14, and the display unit 18. That is, the power is supplied as a voltage stabilized by the DC / DC converter 22 or transformed. The CPU 10 includes an AD converter 30, a RAM 32, and a ROM 34 inside.

  The information terminal also includes a voltage detection circuit 40. This voltage detection circuit detects the voltage between the battery 20 and the DC / DC converter 22, and supplies the detected value to the AD converter 30 of the CPU 10 as the battery voltage. The CPU 10 converts the detected value into digital data and imports it into the CPU 10.

  The battery 20 includes a temperature detection circuit 42. The temperature detection circuit 42 is composed of, for example, a thermistor, and an analog signal output from the temperature detection circuit 42 is input to the AD converter 30 and taken into the CPU 10 as digital data.

  The information terminal includes a USB I / F 50, an SDI / F 51, and a CFI / F 52. The USB I / F 50 is an interface that functions as a connection unit with an external device compatible with USB. The SDI / F 50 is an interface that functions as a connection unit with the SD card. The CFI / F 50 is an interface that functions as a connection unit with the CF card.

  FIG. 2 is an explanatory diagram for explaining the load current with respect to the operation mode of the information terminal. The magnitude | size of the load current which flows into an information terminal in each operation mode shown in FIG. 2 is shown by the mA unit.

  In the initial state of the operation mode A, the magnitude of the load current is 530 mA. This initial state is before the OS is started, and power is supplied to the LCD backlight 12. In addition, since the magnitude | size of load current changes with the brightness | luminances of the LCD backlight 12, according to the magnitude | size of a brightness | luminance, an operation mode can be divided finely and the magnitude | size of a load current can also be set for every divided operation mode. When reproducing a still image in the operation mode B, the magnitude of the load current is 530 mA. When reproducing the moving image in the operation mode C, the magnitude of the load current is 800 mA.

  During music playback (headphone output) in operation mode D, the magnitude of the load current is 580 mA. At the time of music playback (speaker output) in operation mode E, the magnitude of the load current is 680 mA. In the case of music playback, the load current changes depending on the playback volume. Therefore, the operation mode should be subdivided according to the playback volume value, and the load current should be set for each divided operation mode. You can also.

  At the time of data transfer (USB) in operation mode F, the magnitude of the load current is 1330 mA. At the time of operation mode G data transfer (SD card), the magnitude of the load current is 1110 mA. At the time of operation mode H data transfer (CF card), the magnitude of the load current is 1110 mA. At the time of slide show reproduction in operation mode I, the magnitude of the load current is 630 mA. At the time of direct printer printing (via USB) in the operation mode J, the magnitude of the load current is 1300 mA. When the LCD in the operation mode K is turned off, the load current is -100 mA.

  FIG. 3 is an explanatory diagram for explaining the load current when a plurality of operation modes are combined. As in FIG. 2, the magnitude of the load current flowing through the information terminal is shown in mA. For each of the operation modes A to K, the load current is given as described in FIG. 2, but when the operation modes A to K are combined, the load current value given to each operation mode is simply added. The load current value is different from the combined value. FIG. 3 shows the load current value when combined. That is, the load current is shown when two operation modes that can be combined among the operation modes B, D, E, F, G, H, and I are combined.

  By referring to FIG. 2 or FIG. 3 described above, the load current can be obtained from the operation mode of the information terminal. Therefore, even if the change in the load current is not constantly monitored, the load current value can be obtained by checking the operation mode whether the information terminal is playing back a still image or playing music through speaker output. Can be requested.

  4 to 6 are correspondence tables of battery voltage and remaining battery capacity for each load current with respect to each temperature. In this embodiment, the load current is obtained as described in FIG. 2 or FIG. Further, the battery voltage and the battery temperature can be obtained by measurement. The remaining battery level is obtained from the load current, battery voltage, and battery temperature. In each of FIGS. 4 to 6, data is not prepared for all battery temperatures and battery voltages, but interpolation is performed. Create the necessary data.

  FIG. 4 is a correspondence table of battery voltage and remaining battery level when the battery temperature is 5 degrees. FIG. 4 illustrates the relationship between the battery voltage and the remaining battery capacity for load currents of 500 mA, 1000 mA, and 1500 mA when the battery temperature is 5 degrees.

  FIG. 5 is a battery voltage-battery remaining amount correspondence table when the battery temperature is 25 degrees. FIG. 5 illustrates the relationship between the battery voltage and the remaining battery level for load currents of 500 mA, 1000 mA, and 1500 mA when the battery temperature is 25 degrees.

  FIG. 6 is a correspondence table of battery voltage and remaining battery level when the battery temperature is 45 degrees. FIG. 6 illustrates the relationship between the battery voltage and the remaining battery level for load currents of 500 mA, 1000 mA, and 1500 mA when the battery temperature is 45 degrees.

  A table corresponding to the battery temperature is created from the temperature-specific tables shown in FIGS. For example, if the temperature is 35 degrees, there is no corresponding data in FIGS. Therefore, interpolated data is created using data when the temperature shown in FIG. 5 is 25 degrees and data shown in FIG. 6 where the temperature is 45 degrees. As a result, a table adapted to the battery temperature can be produced.

  FIG. 7 is a correspondence table of battery voltage and remaining battery level when the battery temperature is 35 degrees. Since 35 degrees is between 25 degrees and 45 degrees, the correspondence at 35 degrees can be obtained by linearly interpolating the data in FIG. 5 and the data in FIG. In the example of 35 degrees, it is exactly halfway between 25 degrees and 45 degrees, so the table shown in FIG. 7 can be created by adding and dividing by 2.

  Next, the table is adapted to the load current. For example, a case where the operation mode is the moving image playback mode will be described as an example. In the case of the moving image reproduction mode, since it is the operation mode C, it can be seen that the load current is 800 mA with reference to FIG. However, in the stage of FIG. 7, correspondences are still prepared only for 500 mA, 1000 mA, and 1500 mA. 800 mA is between 500 mA and 1000 mA. Therefore, a correspondence relationship for 800 mA is created by linear interpolation from the correspondence relationship prepared for 500 mA and 1000 mA. By performing linear interpolation, it is possible to create a table in which the relationship between the battery voltage and the remaining battery level is associated one-to-one.

  FIG. 8 is a correspondence table of battery voltage and remaining battery capacity when the load current is 800 mA. The correspondence relationship of FIG. 8 is created by linear interpolation from the correspondence relationship prepared for 500 mA and 1000 mA in FIG. Thereby, the correspondence with respect to the battery voltage value in the case of 35 degrees and 800 mA is prepared. According to the table of FIG. 8, the battery remaining amount and the battery voltage value have a one-to-one correspondence. Therefore, the remaining battery level can be obtained by applying the measured value of the battery voltage. For example, when it is detected that the battery voltage is 3.85 V, it can be seen from FIG. 8 that the remaining battery level is 70%.

  FIG. 9 is a flowchart illustrating a process for calculating the remaining battery level in this embodiment. First, a battery voltage is acquired (step S901). The battery voltage is acquired as a digital value through the DC / DC converter 22 and the AD converter 30 by the voltage detection circuit 40 detecting the voltage of the battery 20.

  Next, the battery temperature is acquired (step S902). The battery temperature is acquired as a digital value through the DC / DC converter 22 and the AD converter 30 by the temperature detection circuit 42 detecting the temperature of the battery 20. Next, the operation mode of the information terminal is acquired (step S903). Since the operation mode of the information terminal is stored in the RAM 32, the operation mode of the information terminal is acquired by the CPU 10 reading from the RAM 32.

  Next, the load is calculated from the operation mode-load current table (step S904). With reference to the operation mode-load current table shown in FIG. 2 or FIG. 3, the load current corresponding to the operation mode is obtained. For example, in the moving image playback mode, the load current can be determined to be 800 mA.

  Next, a battery voltage-battery remaining amount conversion table corresponding to the battery temperature is created (step S905). That is, when the battery temperature is 35 degrees, for example, the battery voltage-battery remaining amount conversion table corresponding to the battery temperature shown in FIG. 7 is created from the battery voltage-battery remaining amount conversion tables prepared in advance shown in FIGS. To do.

  Next, a battery voltage-battery remaining amount conversion table corresponding to the load is created (step S906). That is, from the battery voltage-battery remaining amount conversion table corresponding to the battery temperature shown in FIG. 7, for example, when the load current is 800 mA, the battery voltage-battery remaining amount conversion table corresponding to the load current shown in FIG.

  Next, the remaining battery level is calculated (step S907). For example, as shown in FIG. 8, since the battery voltage-battery remaining amount conversion table corresponding to the load current is created, the remaining battery amount corresponding to the battery voltage acquired in step S901 is calculated. Then, the calculated remaining battery level is displayed on the display unit 18 (step S908), and the series of processes is terminated.

  As described above, according to this embodiment, the remaining battery level can be calculated with high accuracy without being affected by the load fluctuation. By accurately displaying the remaining battery level, the remaining battery level can be properly confirmed, and the remaining battery level such as charging can be properly managed. Further, according to this embodiment, it is not necessary to always monitor the load current that can be changed at any time. As a result, it is possible to effectively use CPU resources, and it is particularly useful for small embedded devices because it can achieve downsizing and power saving.

The block diagram explaining an example of a structure of the information terminal of this Example. Explanatory drawing explaining the load current with respect to the operation mode of an information terminal. Explanatory drawing explaining load current when combining a plurality of operation modes. The battery voltage-battery remaining amount correspondence table when the battery temperature is 5 degrees. The battery voltage-battery remaining amount correspondence table when the battery temperature is 25 degrees. The battery voltage-battery remaining amount correspondence table when the battery temperature is 45 degrees. The battery voltage-battery remaining amount correspondence table when the battery temperature is 35 degrees. The battery voltage-battery remaining correspondence table when the load current is 800 mA. The flowchart explaining the process which calculates the battery remaining charge of this Example.

Explanation of symbols

  10 CPU, 12 LCD backlight, 14 HDD, 18 display unit, 20 battery, 22 DC / DC converter, 30 AD converter, 32 RAM, 34 ROM, 40 voltage detection circuit, 42 temperature detection circuit, 50 USB I / F, 51 SDI / F, 52 CFI / F

Claims (5)

First storage means for storing a correspondence table of remaining battery capacity and battery voltage for a predetermined battery temperature and load current magnitude;
A second storage means for storing a correspondence table representing a relationship between a plurality of operation modes representing an operation state of the information terminal and a load current corresponding to each operation mode;
Voltage detection means for detecting the battery voltage;
Temperature detecting means for detecting the battery temperature;
An obtaining means for obtaining a corresponding operation mode of the information terminal among the plurality of operation modes;
Load calculating means for calculating from the second storage means the magnitude of the load current corresponding to the operation mode acquired by the acquiring means;
Interpolation means for creating an interpolation table by interpolating the correspondence table stored in the first storage means in correspondence with the battery temperature and the load current;
Using the interpolation table created by the interpolation means, a remaining amount calculation means for obtaining a remaining battery level corresponding to the battery voltage detected by the voltage detection means,
An information terminal comprising: The first storage means includes a plurality of correspondence tables corresponding to the size of the battery temperature,
The information terminal according to claim 1, wherein the interpolation unit creates an interpolation table corresponding to the battery temperature detected by the temperature detection unit, using the plurality of correspondence tables. The first storage means includes a plurality of correspondence tables for the magnitude of the load current,
The information terminal according to claim 1, wherein the interpolation unit creates an interpolation table corresponding to the load current calculated by the load calculation unit, using the plurality of correspondence tables. The first storage means includes a correspondence table representing a load current corresponding to each combination of operation modes,
The load calculation unit calculates the load current from the correspondence table when the operation mode acquired by the acquisition unit includes a plurality of operation modes. Information terminal described in 1. A battery remaining amount calculation method for an information terminal that stores a correspondence table of battery remaining amount and battery voltage for a predetermined battery temperature and load current magnitude,
An acquisition step of acquiring a battery voltage, a battery temperature, and an operation mode of the information terminal;
A load calculating step for calculating the magnitude of the load current corresponding to the operation mode;
An interpolation step for creating an interpolation table by interpolating the correspondence table in correspondence with the battery temperature and the load current;
In the interpolation table created by the interpolation step, a remaining amount calculation step for obtaining a remaining battery level corresponding to the battery voltage acquired by the acquisition step;
The battery remaining charge calculation method characterized by including.

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