JP2005215332A - Display device and display control method, and program for making computer execute the display control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display device which can save power for reflection type display screen, as required, and increase the amount of display data, within the limited range of power. <P>SOLUTION: This display device is provided with a voltage monitor 105 for detecting the power which can be supplied by a battery 103 for supplying power to the display as a voltage, and a CPU 109 and a display control 107 for changing the display mode of the image in a display panel 101 and reducing the image display power consumed on a display panel 101, when the detected power becomes lower than the predetermined voltage. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a display device that displays an image on a screen, a display control method, and a program for causing a computer to execute the method, and more particularly, a display device such as a portable electronic information terminal equipped with a battery, a display control method, and the like The present invention relates to a program for causing a computer to execute the method.

  Generally, a portable electronic information terminal stores power in a built-in battery (battery) and operates by consuming this power. For this reason, there is a technique for reducing the power consumed by the display screen of the electronic information terminal and extending the operation time when the remaining battery power is low in an environment where the battery cannot be immediately charged.

  As a technique for reducing the power consumption of the display screen, for example, when the remaining amount of power in a word processor or the like becomes a predetermined value or less, the brightness of the backlight of the display screen is reduced. According to such a technique, it is possible to extend the time during which the display device can operate by reducing the power consumed by the backlight. For this reason, for example, when the user cannot browse the document to the end due to insufficient battery power when browsing the document, the backlight brightness is reduced to extend the display time of the document, that is, the limited power range Can increase the amount of data that can be displayed and allows the user to browse the document to the end.

In addition, according to this conventional technology, since the user who is working can immediately recognize a decrease in the brightness of the backlight, it is not necessary to display an indicator or the like on the display screen in order to show the user the remaining power, and the display screen is more effective. (For example, Patent Document 1).
JP-A-6-83396

  However, the above-described conventional technology has a drawback that it cannot be used for anything other than a display screen using a backlight (transmission type screen). Particularly in recent years, electronic paper that displays drawings and characters (both are referred to as images) using a technique for controlling charged particles by an externally applied voltage, such as electrophoresis, has been displayed on a portable electronic information terminal. It is attracting attention as. For this reason, it is required to save power consumption for display screens (reflection type screens) other than the display screen using the backlight according to the remaining power.

  The present invention has been made in view of the above points, and can reduce the power consumption of a reflective display screen as necessary, and increase the amount of data that can be displayed within a limited power range. An object is to provide a display device, a display control method, and a program for causing a computer to execute the method.

In order to solve the above problems, the display device of the present invention provides:
A display device having a display screen for displaying an image, the power supply means for supplying power to the display device, the remaining power detection means for detecting the amount of power that the power supply means can supply to the display device, and the power remaining Display form changing means for changing the display form of the image on the display screen to reduce the power required to display the image when the power detected by the amount detecting means is equal to or lower than a predetermined set power. It is characterized by that.

  According to the display device of the present invention described above, the remaining power detection unit detects the amount of power that the power supply unit can supply to the display device. When the detected power becomes equal to or lower than a predetermined set voltage, the display form changing means can change the display form of the image on the display screen to reduce the power required for displaying the image. For this reason, when the electric power which can be supplied by the power supply unit becomes equal to or less than a predetermined amount, the amount of power required for automatically displaying an image can be reduced.

  In addition, by changing the display form of the image on the display screen when reducing the amount of power, the user operating the display device is informed of the lack of power without providing a separate display such as an indicator indicating the remaining power. Can do. Therefore, the display screen can be effectively used without hiding the image that should be displayed by the indicator or the like or limiting the display area of the image.

  In the present invention, the display screen controls the charged particles to display an image, and the display mode changing unit reduces the voltage applied to the charged particles to reduce the image on the display screen. The contrast is lowered.

  According to such an invention, when a display screen that controls charged particles is used, the power consumption of the display device can be reduced by reducing the contrast of the displayed image.

  In the present invention, the display screen controls the charged particles to display an image, and the display mode changing unit reduces the voltage applied to the charged particles and extends the voltage application time. The rewriting speed of the display screen is reduced.

  According to such an invention, when a display screen that controls charged particles is used, the power consumption of the display device can be reduced by reducing the rewriting speed of the displayed image.

  Further, in the present invention, when the image on which the display screen is displayed is continuously displayed without consuming power, the display form changing means is configured to display at least a character among the images displayed on the display screen. The display is reduced in size.

  According to such an invention, when the image on which the display screen is displayed continues to be displayed without consuming power (memory type display body), the amount of images that can be displayed at one time on the display screen is increased. The power consumption of the display device can be reduced by reducing the number of times of image rewriting.

  Further, the present invention is characterized in that the display form changing means reduces the display area of the image on the display screen.

  According to such an invention, in a display screen where the display area needs to be refreshed in order to display an image, the area to be refreshed can be reduced and the power consumption of the display device can be reduced.

  Further, the present invention is characterized in that a plurality of the set powers are set step by step, and the display form changing means changes the display form of the image on the display screen according to the stage of the set power.

  According to such an invention, the display form of the image is changed stepwise according to the remaining power level, so that the user can know the remaining power level sensuously. In addition, it is possible to set the image display form in consideration of the relationship between the necessity of increasing the amount of data that can be displayed and the visibility of the image on the display device.

  The display control method of the present invention is a display control method for a display device comprising a display screen for displaying an image and a power supply means, and detects the amount of power that the power supply means can supply to the display device. Reducing the power supplied to the display screen by changing the display form of the image on the display screen when the power remaining in the remaining power detection step and the power detected in the remaining power detection step are below a predetermined voltage And a display form changing step to be performed.

  According to the display control method of the present invention described above, the power supply means detects the amount of power that can be supplied to the display device in the remaining power detection step. Then, when the detected power becomes equal to or lower than a predetermined set power, the display form of the image on the display screen can be changed in the display form changing step to reduce the power required for displaying the image. For this reason, when the electric power which can be supplied by the power supply unit becomes equal to or less than a predetermined amount, the amount of power required for automatically displaying an image can be reduced.

  In addition, by changing the display form of the image on the display screen when reducing the amount of power, the user operating the display device is informed of the lack of power without providing a separate display such as an indicator indicating the remaining power. Can do. Therefore, the display screen can be effectively used without hiding the image that should be displayed by the indicator or the like or limiting the display area of the image.

The program of the present invention is
A program for causing a computer to execute a display control method for a display device including a display screen for displaying an image and a power supply unit, wherein the power supply unit detects an amount of power that can be supplied to the display device. A display that reduces the power supplied to the display screen by changing the display form of the image on the display screen when the power detected in the amount detection step and the remaining power detection step is less than or equal to a predetermined voltage And a form changing step.

  According to the above-described program of the present invention, the power supply means detects the amount of power that can be supplied to the display device in the remaining power detection step. When the detected power becomes equal to or lower than a predetermined set power, the display mode of the image on the display screen can be changed in the display mode changing step to reduce the power required for displaying the image. For this reason, when the electric power which can be supplied by the power supply unit becomes equal to or less than a predetermined amount, the amount of power required for automatically displaying an image can be reduced.

  In addition, by changing the display form of the image on the display screen when reducing the amount of power, the user operating the display device is informed of the lack of power without providing a separate display such as an indicator indicating the remaining power. Can do. Therefore, the display screen can be effectively used without hiding the image that should be displayed by the indicator or the like or limiting the display area of the image.

  Embodiments 1 to 3 of a display device, a display control method, and a program for causing a computer to execute the method of the present invention will be described below with reference to the drawings. In addition, in this embodiment, the example which comprised the display apparatus as an electronic book terminal for browsing an electronic book is shown.

  FIG. 1 is a block diagram for explaining the configuration of the display device of the present invention, and is a diagram common to the first to third embodiments.

  The illustrated display device includes a display panel 101 for displaying an image, a battery 103 that supplies power to the display device, and a remaining power detection that detects the amount of power that the battery 103 can supply to the display device. A voltage monitoring unit 105 that functions as a means, and a display form changing means that changes the image display form on the display panel 101 when the detected power is equal to or lower than a predetermined power, and reduces the power required to display the image. A functioning display control unit 107 and a CPU 109 are provided.

  Of the above-described configurations, the display panel 101 is not a configuration that emits light using a backlight, but a reflective type that reflects external light. Further, the voltage monitoring unit 105 includes a voltage monitoring power source 106 which is a dedicated power supply device. The display device according to this embodiment includes a reflective display panel 101, and is always used under a certain degree of illumination. Therefore, the voltage monitoring power source 106 can be configured not to receive power supply from the outside like a solar cell.

  Further, the CPU 109 is configured to control the entire display device. For control by the CPU 109, the display device stores an input unit 115 for a user to operate using the display device as an electronic book terminal, and a program and data for displaying electronic book data on the display panel 101 based on the operation. A ROM 117, a RAM 119 in which displayed electronic book data is expanded, and an oscillation circuit 113 that supplies a clock signal necessary for the overall operation are provided. In addition, the CPU 109 includes a PLL (Phase Locked Loop) 111 that compares the clock signal input from the oscillation circuit with a reference signal to obtain a signal having no phase shift.

  The configuration described above operates as follows. That is, the CPU 109 downloads electronic book data (hereinafter referred to as book data) through a network line (not shown) or reads out from the ROM 117 in accordance with a user instruction input from the input unit 115. The CPU 109 expands the book data in the RAM 119 and displays the expanded data on the display panel 101.

  Further, the voltage monitoring unit 105 monitors the remaining power level of the battery that consumes power by the above operation as a voltage, and periodically notifies the CPU 109 of the remaining power level as a voltage. The CPU 109 compares the notified voltage with a preset power (set voltage) as a voltage. When the notified voltage becomes equal to or lower than the set voltage, the display control unit 107 is controlled to change the image display form on the display panel 101. This change is made so as to reduce the power required to display an image on the display panel 101. In the present embodiment, a plurality of set voltages are set step by step, and the image display form on the display panel 101 is changed according to the set voltage step.

  Hereinafter, the configuration and operation of each of Embodiments 1 to 3 will be described.

(Embodiment 1)
The display device according to the first embodiment is a display panel in which the display panel 101 controls charged particles to display an image. In particular, in the first embodiment, electrophoresis is used. The display control unit 107 according to the first embodiment reduces the voltage applied to the charged particles of the display panel 101, thereby reducing the rewriting speed of the display panel and reducing the power consumption of the display panel 101.

  That is, a display panel of an electrophoretic type or the like that displays an image by controlling charged particles has a characteristic of continuing to display an image once displayed without consuming power, and is also called a memory display. Yes. When rewriting an image, the memory-type display body needs to perform an operation (white reset) to make the screen white once by applying a voltage to the charged particles and moving the image every time the image is rewritten. For this reason, a voltage for image display and a voltage for white reset are alternately applied to the charged particles of the electrophoretic panel. In the first embodiment, when the voltage indicating the remaining amount of power of the battery 103 is lower than the set voltage, the voltage applied for image display (image display voltage) is set lower than the voltage normally applied for image display. Such power is reduced.

  FIG. 2 is a diagram showing an image (low voltage image) obtained when the image display voltage is lowered compared with an image (standard image) displayed when power saving is not necessary. Indicates a standard image, and (b) indicates a low voltage image. In the example shown in FIG. 2, the application time of the image display voltage and the voltage applied for the white reset are the same regardless of the level of the image display voltage.

  When the image display voltage is lowered, the moving amount of the charged particles from the white reset to the image display is lowered. Therefore, as shown in FIG. 2, the contrast of the low voltage image (the black-and-white ratio between the image (characters in the example of FIG. 2) and the background) is lower than that of the standard image. Therefore, the image display voltage of the first embodiment is determined according to the allowable range related to contrast and the necessity of increasing the amount of data by saving power on the display panel 101.

  FIG. 3 is a diagram for explaining the effects obtained in the first embodiment described above. The vertical axis indicates the voltage notified from the voltage monitoring unit 105 to the CPU 109, and the horizontal axis indicates the number of times the display panel 101 is rewritten ( In the memory display, the number of rewrites is a measure of the amount of data to be displayed). In the drawing, an operation mode for controlling the display panel 101 with a standard image display voltage is referred to as a standard mode in the first embodiment, and an operation mode for controlling the display panel 101 with a lower image display voltage is referred to as a power saving mode. Note that the voltage corresponding to the remaining amount of power that is determined to be impossible to rewrite the display panel 101 when the display device is operated in the standard mode is shown as “battery exhaust voltage” in the figure.

  Further, in the power saving mode, the power saving mode 1, the power saving mode 2, and the power saving mode 3 are provided, the image display voltage in the power saving mode 2 is lower than that in the power saving mode 1, and the image display voltage in the power saving mode 3 is displayed in the power saving mode 2. Set lower than the voltage.

  The set voltage is determined in multiple stages as V1, V2, V3 (V1> V2> V3), and when the voltage notified to the CPU 109 reaches the set voltage V1, the display panel 101 is controlled in the power saving mode 1 (power saving mode 1). region). When the notified voltage reaches the set voltage V2, the display panel 101 is controlled in the power saving mode 2 (power saving mode 2 region), and when the notified voltage reaches the set voltage V3, the display panel 101 is controlled in the power saving mode 3. (Power saving mode 3 area).

  According to FIG. 3, it can be seen that by using the power saving mode, the number of rewrites that can be performed before reaching the battery exhaust voltage is increased as compared with the case of using the standard mode. Therefore, the display device according to the first embodiment can reduce power consumption according to the remaining battery level, increase the number of possible rewrites within a limited power range, and display even on a reflective display screen. It can be said that the amount of data can be increased. Note that the configuration of the first embodiment is effective when the remaining amount of power of the battery 103 is greater than or equal to the amount corresponding to the battery exhaust voltage.

  In addition, the display device according to the first embodiment can set the setting voltage in multiple stages based on the remaining battery power, the request for increasing the number of rewrites, and the allowable range of the contrast of the image. For this reason, the contrast of the image and the number of rewrites can be set more flexibly according to the state of the display device. In the configuration described above, the setting voltage and the image display voltage are made to correspond one-to-one in advance, and the contrast is automatically set. However, the present invention is not limited to such an embodiment, and the user may set the contrast via the input unit 115 and determine the image display voltage. According to such a configuration, an image can be displayed with higher contrast when the number of rewrites is relatively small for browsing all electronic books. On the other hand, when it is desired to prioritize the increase in the number of rewrites over the decrease in visibility due to a decrease in contrast, a larger amount of book data can be viewed with a low contrast by setting the image display voltage lower.

  FIG. 4 is a flowchart for explaining a display control method performed by the display device according to the first embodiment. In the display device according to the first embodiment, the CPU 109 acquires the remaining power of the battery 103 as a voltage from the voltage monitoring unit 105 (step S401). Then, the CPU 109 determines whether or not the acquired voltage is equal to or higher than the set voltage V1 (step S402). As a result of the determination, when the acquired voltage has a value equal to or higher than the set voltage V1 (step S402: Yes), the CPU 109 applies a standard mode, that is, a standard image display voltage to the charged particles via the display control unit 107. The display panel 101 is controlled (step S405).

  If it is determined in step S402 that the acquired voltage is not equal to or higher than V1 (step S402: No), it is further determined whether or not the acquired voltage is equal to or higher than the set voltage V2 (step S403). As a result, if the voltage is equal to or higher than the set voltage V2 (step S403: Yes), an image display voltage that is one step lower than the image display voltage in the power saving mode 1, that is, the standard mode is applied to the charged particles. Control (step S406).

  On the other hand, when it is determined in step S403 that the acquired voltage is not equal to or higher than V2 (step S403: No), it is determined whether or not the acquired voltage is equal to or higher than the set voltage V3 (step S404). As a result, when the voltage is equal to or higher than the set voltage V3 (step S404: Yes), an image display voltage that is one step lower than the image display voltage in the power saving mode 2, that is, the power saving mode 1, is applied to the charged particles. Is controlled (step S407). Furthermore, when the acquired voltage does not have a value equal to or higher than V3 (step S404: No), the CPU 109 determines whether or not the acquired voltage has a value equal to or higher than the battery dead voltage shown in FIG. 3 (S408). .

  As a result of the determination in step S408, if the acquired voltage is equal to or higher than the battery exhaustion voltage (S408: Yes), the charged particle is set to an image display voltage that is one step lower than the image display voltage in the power saving mode 3, that is, the power saving mode 2. To control the display panel 101 (step S409). On the other hand, when it is determined that the acquired voltage is less than the battery exhaustion voltage (S408: No), a message is displayed that warns that the display device will not accept (execute) rewriting anymore (battery exhaustion). (S410). And the process which concerns on the change of the display form according to power remaining amount is complete | finished.

  Next, another configuration of the first embodiment described above will be described. This configuration reduces the rewriting speed of the display panel 101 while lowering the image display voltage and extending the time for applying the image display voltage to the charged particles as compared with the standard time as in the configuration described above. It is. As a result, the display panel 101 can alleviate the decrease in contrast although the rewriting speed decreases, and can obtain the same image quality as that in the operation in the standard mode. For this reason, the image display voltage and the voltage application time are determined in accordance with the allowable range related to contrast and the allowable range related to a decrease in the rewriting speed and the necessity of saving the display panel 101 and increasing the number of times of rewriting.

  FIG. 5 is a diagram for explaining the effect of increasing the number of rewrites obtained when the voltage application time is extended from the standard time while reducing the image display voltage. In the graph shown in FIG. 5, the vertical axis indicates the voltage notified from the voltage monitoring unit 105 to the CPU 109, and the horizontal axis indicates the number of rewrites of the display panel 101. In addition, when the display device is operated in the standard mode, the voltage corresponding to the remaining amount of power, which is determined to be no longer possible to rewrite the display panel 101, is displayed when the display device is operated in the battery low voltage VE1 and in the power saving mode. The voltage corresponding to the remaining power level at which it is determined that the panel 101 cannot be rewritten any more is shown in FIG.

  In the example shown in FIG. 5, the display device operates in the standard mode until the voltage notified to the CPU 109 reaches the battery exhaust voltage during the operation in the standard mode. Then, after the remaining power of the battery 103 is further reduced, the number of rewrites is increased by operating in the power saving mode in which the voltage application time is extended from the standard time while the image display voltage is lowered.

  Further, even when the voltage application time is extended from the standard time, the set voltage is determined in multiple stages as V1, V2, and V3 (V1> V2> V3), and the voltage notified to the CPU 109 becomes the set voltage V1. When it reaches, the display panel 101 is controlled in the power saving mode 1 (power saving mode 1 area). When the notified voltage reaches the set voltage V2, the display panel 101 is controlled in the power saving mode 2 (power saving mode 2 region), and when the notified voltage reaches the set voltage V3, the display panel 101 is controlled in the power saving mode 3. (Power saving mode 3 area).

  According to the configuration of the first embodiment, the power consumption of the reflective display screen can be reduced according to the remaining battery level as in the configuration described above, and can be rewritten within a limited power range. You can increase the number of times. Furthermore, the other configuration of the first embodiment is also effective when the remaining power of the battery 103 is equal to or less than the amount corresponding to the battery exhaust voltage.

  In the above-described configuration, the set voltage, the image display voltage, and the voltage application time are associated with each other in a one-to-one correspondence, and the contrast and the rewrite time are automatically set. However, the present invention is not limited to such an embodiment, and the user may set visibility such as contrast via the input unit 115 to determine the image display voltage and the rewriting time. According to such a configuration, when the number of times of rewriting is relatively small for browsing an electronic book, a higher quality image is displayed, and the number of times of rewriting is reduced due to a decrease in visibility due to a decrease in contrast and rewriting time. If the user wants to prioritize the e-book, he / she can browse the e-book for a longer time with low image quality.

  Further, although the first embodiment has described the configuration using electrophoresis for the display panel, the present invention is not limited to such a configuration, and it is also applicable to a memory display that requires rewriting. Of course it is possible.

(Embodiment 2)
Next, Embodiment 2 of the present invention will be described. The display device according to the second embodiment saves power of the display device by reducing at least characters in the image displayed on the display panel 101, and increases the number of rewrites with respect to the remaining power of the battery 103. is there. In the second embodiment, for example, a display body that continuously displays an electrophoretic display image without consuming power, that is, a memory display body, is used for the display panel 101. The book data is suitable for the case where characters are not laid out as a page, for example, in the HTML format.

  FIG. 6 is a diagram showing an image (reduced image) obtained by reducing a character displayed as an image in comparison with a standard image, where (a) shows a standard image and (b) shows a reduced image. Show. As illustrated, in the second embodiment, the standard image and the reduced image are displayed in the same display areas R1 and R2. Such a configuration of the second embodiment can display more data of the electronic book as characters on the display panel 101 at a time. For this reason, there is an effect of reducing the number of times of rewriting of an image for browsing the entire electronic book and increasing the amount of book data that can be displayed within a limited range of remaining power. Such an effect is particularly effective when a memory-type display body that does not consume power is used for the display panel 101 when images are continuously displayed as in the second embodiment described above.

  Also in the second embodiment, the reduction ratio of the standard image may be determined in multiple stages together with the set voltage, and the reduction ratio may be determined according to the set voltage. Further, the correspondence between the set voltage and the reduction magnification is not limited to that set in the display device in advance, and the user may determine the reduction magnification while checking the image on the display panel 101.

(Embodiment 3)
Next, Embodiment 3 of the present invention will be described. The CPU 109 and the display control unit 107 reduce the display area of the image on the display panel 101, thereby saving power of the display device and increasing the number of rewrites for the remaining power of the battery 103. In the third embodiment, the display panel 101 is not a storage-type display body, but a display panel that constantly refreshes the screen during image display.

  FIG. 7 is a diagram for explaining a state in which the display area of the image is reduced. FIG. 7A shows a state in which the image is displayed on the display panel 101 when the display device is operated without power saving. Show. Further, (b) shows a state in which an image is displayed on the display panel 101 when the display device is operated with power saving. The image shown in FIG. 7A is displayed in the display area R 1 (standard area) of the display panel 101. On the other hand, in (b), the image is displayed in a region R4 (reduced region) obtained by further subtracting the region R3 from the display region R1. In FIG. 7, the region R3 is shown in black, but this range may be displayed as white.

  The power consumption of a display that constantly refreshes an image is mainly determined by the product of the display area of the screen and the display time. For this reason, as in the third embodiment, the display area can be reduced, and the reduced area is not subjected to refresh, thereby reducing the power consumed by the display panel, and thus the power consumption of the display device can be reduced. The reduction ratio of the display area is determined by a reduction in visibility caused by the reduction of the display screen and a request for power saving. However, in the configuration of the third embodiment, the amount of book data that can be displayed at a time is reduced, and thus the display time until the book data is browsed may be increased. Therefore, it is necessary to further consider the relationship between the display area to be refreshed and the display time in the conditions for the operation of the third embodiment.

  Even in the third embodiment, the book data is suitable when characters are not laid out as pages. Assuming that the book data is always displayed in a constant page layout, when configured as in the third embodiment, scrolling the page is necessary to view the entire page, which may increase power consumption. It is.

  Furthermore, even in the third embodiment, the set voltage may be provided in multiple stages, and the size of the display area may be set in multiple stages according to each set voltage. At this time, the correspondence between the set voltage and the size of the display area of the image is not limited to that set in the display device in advance, and the user determines the range of the reduced area while checking the image on the display panel 101. It may be.

  Further, the present invention can be used by appropriately combining the first to third embodiments described above. For example, FIG. 8 is a diagram illustrating a display state of the display panel 101 when the second embodiment and the third embodiment are combined. FIG. 8A shows a state in which a standard image is displayed in the standard area R1, and FIG. 8B shows a state in which a reduced image is displayed in the reduced area R4. According to such an example, it is possible to prevent a reduction in the amount of book data that can be displayed at a time in the third embodiment. For this reason, the power consumption of the display panel can be further effectively reduced, and the display time of the book data can be further extended.

  Furthermore, Embodiments 1 to 3 of the present invention can be used in combination with other general power saving techniques. Other techniques that can be combined include, for example, a technique for reducing the power consumption of the display device by setting the operation magnification of the PLL 111 to a low magnification. FIG. 9 is a diagram showing the clock frequency of the PLL 111. FIG. 9A shows the frequency of the clock generated during standard operation, and FIG. 9B shows the frequency of the clock generated when saving power. ing.

  Since electric circuits have stray capacitance, it is generally known that power loss increases as the operating frequency increases. For this reason, when the clock frequency is lowered, the operation speed is also lowered, but the power consumption can be reduced.

  FIG. 10 shows the usable time when the display device is operated at the clock frequency shown in FIG. 9A and the usable time when the display device is operated at the clock frequency shown in FIG. It is the figure shown in comparison. The vertical axis represents the voltage of the battery 103, and the horizontal axis represents the time during which the display device can be used. As shown in the figure, the usage time of the display device can be extended by lowering the clock frequency.

  Even in such a method, the set voltage may be set in multiple stages and the clock frequency may be set in multiple stages according to each set voltage. Then, as the set voltage is lowered, the clock frequency can be lowered to adjust the delay of the operation time and the increase of the use time.

  As described above, the present invention changes the image display form on the display panel 101 to display an image when the amount of power that the battery 103 can supply to the display device becomes equal to or less than a predetermined set power. Such electric power can be reduced. For this reason, when the power that can be supplied by the battery 103 falls below a predetermined amount, the amount of power required for image display is automatically reduced to increase the number of image rewrites, or the display time is extended, A larger amount of book data can be displayed while the remaining power is limited.

  Further, the present invention changes the display form of the image on the display screen when reducing the amount of power. For this reason, it is possible to notify the user of power shortage without providing a separate display such as an indicator indicating the remaining power. Therefore, the display panel can be used effectively without hiding the image that should be displayed by the indicator or limiting the display area of the image.

It is a block diagram which shows a structure common to Embodiment 1 thru | or Embodiment 3 among this invention. It is a figure for demonstrating Embodiment 1 of this invention. It is a figure for demonstrating the effect acquired by the structure of Embodiment 1 of this invention. It is a flowchart for demonstrating the display control method performed with the display apparatus of Embodiment 1 of this invention. It is a figure for demonstrating the effect acquired by the other structure of Embodiment 1 of this invention. It is a figure for demonstrating Embodiment 2 of this invention. It is a figure for demonstrating Embodiment 3 of this invention. It is a figure which shows the display state of the display panel at the time of combining Embodiment 2 and Embodiment 3 of this invention. It is a figure which shows the clock frequency of PLL. It is a figure which shows the result of having compared the usable time of a display apparatus with a different clock frequency.

Explanation of symbols

  101 is a display panel, 103 is a battery, 105 is a voltage monitoring unit, 106 is a voltage monitoring power supply, 107 is a display control unit, 109 is a CPU, 111 is a PLL, 113 is an oscillation circuit, 115 is an input unit, 117 is a ROM, 119 is RAM

Claims (8)

A display device having a display screen for displaying an image,
Power supply means for supplying power to the display device;
A remaining power detection means for detecting the amount of power that the power supply means can supply to the display device;
A display form changing means for changing the display form of the image on the display screen to reduce the power required to display the image when the power detected by the remaining power detection means is less than or equal to a predetermined set power; ,
A display device comprising:   The display screen controls the charged particles to display an image, and the display form changing unit reduces the image contrast on the display screen by reducing a voltage applied to the charged particles. The display device according to claim 1.   The display screen controls the charged particles to display an image, and the display mode changing means reduces the voltage applied to the charged particles and extends the voltage application time to rewrite the display screen. The display device according to claim 1, wherein speed is reduced.   The display screen continues to display the displayed image without consuming power, and the display form changing means displays at least a character of the image displayed on the display screen in a reduced size. The display device according to claim 1, wherein the display device is a display device.   The display device according to claim 1, wherein the display form changing unit reduces a display area of an image on the display screen.   6. The display voltage changing unit according to claim 1, wherein a plurality of the set voltages are set step by step, and the display form changing unit changes a display form of an image on the display screen according to the stage of the set voltage. The display device according to one. A display control method for a display device comprising a display screen for displaying an image and a power supply means,
A remaining power detection step for detecting the amount of power that the power supply means can supply to the display device;
A display mode changing step of reducing the power supplied to the display screen by changing the display mode of the image on the display screen when the power detected in the remaining power detection step is equal to or lower than a predetermined power;
A display control method comprising: A program for causing a computer to execute a display control method of a display device including a display screen for displaying an image and a power supply unit,
A remaining power detection step for detecting the amount of power that the power supply means can supply to the display device; and
A display mode changing step for reducing the power supplied to the display screen by changing the display mode of the image on the display screen when the power detected in the remaining power detection step is equal to or lower than a predetermined power;
The program characterized by including.

Images