JP2009237029A - Drive device and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the power consumption in a drive part of a display device which is configured to continue to display an image without drive of a display element, while reducing the time required to display the image. <P>SOLUTION: A voltage step-up circuit 17 continuously steps up the voltage over a period from end of the drive of a display element 19 for displaying an image by a drive part 18 to start of the drive for displaying the next image. Accordingly, the input voltage of the drive part 18 is raised to the step-up voltage immediately upon ON of a switch 20 on and after the second image display, so that no rising period of the step-up circuit 17 is caused. The switch 20 is OFF while the step-up circuit 17 continuously steps up the voltage, thereby the power consumption related to this step-up is minimized. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a display device using a display element having memory properties.

A display device employing a display element having a memory property such as an electrophoretic element has been developed. In this type of display device, when an image is displayed by applying a driving voltage to the display element, the image can be continuously displayed as it is without using the driving voltage, so that power saving can be achieved. . A technique for displaying an image on a display device using an electrophoretic element is disclosed in Patent Document 1, for example.
JP 2007-256732 A

FIG. 6 is a diagram illustrating an example of a hardware configuration of the display device 100 using the electrophoretic element. The step-up circuit 17 is called a step-up switching regulator and is composed of components such as a coil, a capacitor, and a switch. The booster circuit 17 starts an operation of boosting the power supply voltage of the power supply unit 16 under the control of a CPU (Central Processing Unit) 11 and applies the boosted voltage as an input voltage of the drive unit 18. The potential Vr of the boosted voltage and the potential Vd of the input voltage to the driving unit 18 are equal to the potential at the point A shown in FIG. The display body 19 is an electrophoretic display means, and after displaying an image, the display body 19 can continue to display an image even when a drive voltage is not applied. The driving unit 18 drives each display element by applying a driving voltage to each electrophoretic element (display element) of the display body 19 and displays an image corresponding to the driving voltage. The drive unit 18 drives the display element of the display body 19 using the input voltage applied when the boosted voltage potential Vr rises to the predetermined potential VT.

  FIG. 7 is a time chart showing the operation of each part of the device and the state transition when the display device 100 displays an image. 6A shows the operation of the key 15, FIG. 6B shows the operation of the booster circuit 17, and FIG. 6C shows the potential Vr of the boosted voltage applied by the booster circuit 17 (FIG. 6). (D) represents the operation of the drive unit 18. FIG. In FIGS. 4A, 4B, and 4D, when the key 15 is operated by the user, when the booster circuit 17 is boosted, and when the drive unit 18 operates the display element of the display body 19. The driving periods are each in an on state (ON), and the other periods are in an off state (OFF).

  First, at time t = 0, as shown in FIG. 5A, when the user operates the key 15 to instruct the display of the first image, the CPU 11 switches the switch (not shown) in the booster circuit 17. Is turned on, and the booster circuit 17 starts boosting the power supply voltage as shown in FIG. As a result, as shown in FIG. 5C, the potential V of the boosted voltage gradually increases during the period from time t = 0 to t = T1, and rises to the predetermined potential VT at time t = T1. Hereinafter, the period during which the boosted voltage rises is referred to as “rise period”.

At time t = T1, the driving unit 18 starts driving the display element of the display body 19. At this time, the CPU 11 outputs the image data to the drive unit 18, and in the drive period from time T1 to time T2 shown in FIG. 4D, the drive unit 18 sets a plurality of potential differences depending on the drive voltage according to the image data. An image is displayed by applying to the display element. As shown in FIGS. 4B and 4D, at time t = T2, the CPU 11 ends the driving by causing the driving unit 18 to end the driving period, and causes the boosting circuit 17 to stop the boosting. In the period from time t = T2 to t = T3, the voltage is not boosted by the booster circuit 17, so the potential V of the boosted voltage decreases with time. At this time, the display body 19 continues to display the displayed image as it is, although the drive voltage is not applied by the drive unit 18. When the key 15 is operated at time t = T3 to instruct to display the second image, the CPU 11 rises from time t = T3 to t = T4 in the same manner as described above. A period is set, and an image is displayed on the display body 19 from time t = T4 to t = T5 as a driving period. In this configuration, the period from time t = 0 to t = T2 required for the display device 100 to display the first image and from time t = T3 required to display the second image. The period up to t = T5 is almost the same length.

As shown in FIG. 5C, even when the rising period starts from time t = 0 and the booster circuit 17 starts boosting, the boosted voltage does not immediately rise to the predetermined potential VT, and the boosted voltage gradually increases. The time T1 is required as a rise time. This time T1 is, for example, about 0.3 to 0.6 seconds, and it takes a certain amount of time for the booster circuit 17 to perform a stable boost such as the drive period. The reason why a considerable rise time is required in this way is because it takes time until energy is stored in the coils and capacitors used in the booster circuit 17. Therefore, the user has to wait for the rising period and the driving period until an image is displayed on the display 19 after instructing the display of the image. Even when the user instructs display of the next image at time t = T3, it is necessary to wait for almost the same period as the rising period and the driving period.
Therefore, the present invention reduces power consumption in the drive unit of the display device while reducing the time required to display the image in a display device that continues to display an image without driving the display element. With the goal.

  In order to achieve the above-described object, according to the present invention, a boosting unit that boosts the voltage of a power supply and an image corresponding to the driving voltage are displayed when a driving voltage is applied, and the driving is performed after the image is displayed. Driving means for driving a display element group that continues to display the image even when no voltage is applied, one end connected to the boosting means and the other end connected to the driving means, the boosting means and the driving means The switch is turned on from the OFF state while continuing the boosting by the boosting means, and the switch that is in the ON state in which the boosting means and the driving means are not conducted, In order to cause the driving means to drive the display element group with the boosted voltage in a state, and to turn the switch from an on state to an off state after the driving is completed, To provide a drive device, characterized in that it comprises a control means for switching the state. In a display device including such a drive device, power consumption in the drive unit of the display device can be reduced while shortening the time required to display an image.

  The present invention also provides a storage means for storing image data and an image corresponding to the drive voltage when a drive voltage is applied, and the image is displayed even if the drive voltage is not applied after the image is displayed. A display device comprising: a display body having a display element group that continues to display a display element; and a drive device having the above-described configuration that drives the display element group of the display body in accordance with image data stored in the storage means. I will provide a. According to this, in a display device that continues to display an image without driving the display element, it is possible to reduce the power consumption in the drive unit of the display device while reducing the time required to display the image. it can.

Next, the best mode for carrying out the present invention will be described with reference to the drawings.
(A) Configuration of Embodiment FIG. 1 is a block diagram illustrating a configuration of a display device 10. In the figure, solid arrows indicate the flow of various control signals.
As shown in the figure, the display device 10 includes a CPU 11, a ROM (Read Only Memory) 12, a RAM (Random Access Memory) 13, an I / O 14, a key 15, a power supply unit 16, and a booster circuit 17. And a drive unit 18, a display body 19, a switch 20, and a storage unit 21. The CPU 11, the booster circuit 17, the drive unit 18, and the switch 20 function as a drive device that drives the display body 19 to display an image.

  CPU11 controls each part of the display apparatus 10 by reading the control program memorize | stored in ROM12 or the memory | storage part 21 to RAM13, and running it. The CPU 11 controls the power supply unit 16 to supply power to each unit in the apparatus, or generates bitmap-format image data on the RAM 13 based on the image file or the document file stored in the storage unit 21. The drive unit 18 is controlled to display an image corresponding to the image data on the display body 19. Further, when displaying an image on the display body 19, the CPU 11 performs control such as boosting the booster circuit 17 or switching the switch 20 off or on. The RAM 13 becomes a work area for the CPU 11 when the CPU 11 executes the program. The I / O 14 monitors the operation state of the key 15, and when the user operates the key 15, supplies a signal corresponding to the operation to the CPU 11. The key 15 is an operation unit that receives an operation by the user, and includes, for example, an operation device such as a plurality of operation keys, a joystick, and a touch pen.

  The power supply unit 16 includes a battery and a power control circuit, and supplies power necessary for the operation of the display device 10 to each unit in the device under the control of the CPU 11. The battery of the power supply unit 16 is a rechargeable secondary battery such as a nickel metal hydride battery or a lithium ion battery. The booster circuit 17 is a switching regulator composed of components such as a coil, a capacitor, and a switch, and functions as a booster that boosts the voltage of the power supply unit 16. The switch 20 has one end connected to the booster circuit 17 and the other end connected to the drive unit 18 to turn on the booster circuit 17 and the drive unit 18 or to connect the booster circuit 17 and the drive unit 18. It will be in any of the off states that are not allowed. When a MOS transistor (field effect transistor) is used as the switch 20, the drain is connected to one end of the booster circuit 17, the source is connected to the drive unit 18, and the gate is applied to the gate under the control of the CPU 11. The on / off state of the switch 20 is switched by the voltage. When the switch 20 is turned on, the drive unit 18 and the display body 19 are electrically connected to the booster circuit 17, so that a voltage corresponding to the boosted voltage is applied as the input voltage of the drive unit 18. At this time, the potential Vr of the boosted voltage and the potential Vd of the input voltage of the drive unit 18 are substantially the same.

  The display body 19 is an electrophoretic element type display means, and includes a plurality of display elements (display element group) and various electrodes. Each display element included in the display 19 displays an image corresponding to the drive voltage when a drive voltage is applied, and continues to display the image after the image is displayed even if the drive voltage is not applied. Can do. This is called display memory. The display 19 displays an image corresponding to the image data in its own display area by driving each display element by the driving unit 18. The configuration of the display body 19 will be described in detail later.

When the boosted voltage boosted by the booster circuit 17 is applied as an input voltage via the switch 20, the drive unit 18 drives each display element of the display body 19 using the boosted voltage, and the image data read from the RAM 13 is used. The image corresponding to is displayed. That is, when the drive voltage is applied, the drive unit 18 displays an image corresponding to the drive voltage, and after displaying the image, drives the display element group that continues to display the image even if the drive voltage is not applied. Functions as a driving means. The storage unit 21 is a nonvolatile storage unit such as an EEPROM (Electrically Erasable and Programmable Read Only Memory) or a flash memory, and stores various files related to image display such as a document file and an image file.

  FIG. 2 is a diagram schematically showing the structure of the display body 19. As shown in the figure, the display body 19 includes a first substrate 191, a plurality of electrophoretic elements P, a binder 192, and a second substrate 193. The first substrate 191 is a planar substrate made of glass or resin, and a plurality of pixel electrodes PE are arranged on the upper surface side in the drawing. The second substrate 193 opposed to the first substrate 191 is a planar substrate made of transparent glass or resin, and a common electrode CE is provided on the lower back side in the drawing. Between the plurality of pixel electrodes PE and the common electrode CE, a large number of electrophoretic elements as display elements P are fixed by a binder 192 in a state where they are arranged. The display element P is microencapsulated, and the black pigment particles BG charged positively (+) and the white pigment particles WG charged negatively (−) are encapsulated therein. When an image is displayed on the display body 19, a driving voltage is applied between the pixel electrodes PE and the common electrode CE by the driving unit 18, and the color particles in the display element P are moved according to this potential difference. When displaying a black image on the display element P, the drive unit 18 applies a drive voltage such that the potential of the pixel electrode PE below the drive unit 18 is higher than the potential of the common electrode CE. Thereby, only the black pigment particles BG are moved to the surface of the display body 19, and a black image is displayed. On the other hand, when displaying a white image on the display element P, the drive unit 18 applies a drive voltage such that the potential of the pixel electrode PE below the drive unit 18 is lower than the potential of the common electrode CE. Thereby, only the white pigment particle WG is moved to the surface of the display body 19, and a white image is displayed.

(B) Operation FIG. 3 is a time chart showing the operation of each part of the device and the state transition when the display device 10 displays an image on the display body 19. 2A shows the operation of the key 15, FIG. 2B shows the operation of the booster circuit 17, FIG. 2C shows the driving state of the switch 20, and FIG. 2 represents the potential Vd of the input voltage of the unit 18 (that is, the potential at the point A in FIG. 1), FIG. 3E represents the operation of the drive unit 18, and FIG. The voltage potential Vr (the potential at the point B in FIG. 1) is represented. In these figures, when the key 15 is operated by the user, the period during which the booster circuit 17 boosts the voltage and the period during which the drive unit 18 drives the display element of the display body 19 are turned on (ON). The other periods are in the off state (OFF). Prior to time t = 0 shown in the time chart, a power switch (not shown) of the display device 10 is turned on by the user, and the display device 10 starts operating. At this time, the booster circuit 17 is turned off and not boosted, the boosted voltage potential Vr is “0 V”, the input voltage potential Vd of the drive unit 18 is also “0 V”, and it is not driven. To do. Further, the switch 20 is in an OFF state, and the booster circuit 17 is not electrically connected to the drive unit 18 and the display body 19.

  At time t = 0, when the user operates the key 15 to instruct the display of the first image as shown in FIG. 9A, the CPU 11 increases the voltage as shown in FIG. A control signal for starting boosting of the power supply voltage is output to the circuit 17. In response to this, the booster circuit 17 switches from the off state to the on state, and starts boosting the power supply voltage of the power supply unit 16. At this time t = 0, as shown in FIG. 3C, the CPU 11 outputs a control signal for controlling the switch 20 to apply a gate voltage for switching the switch 20 from the off state to the on state. To do. That is, the CPU 11 turns on the switch 20 when boosting by the booster circuit 17 is started. As a result, the switch 20 is turned on in which the booster circuit 17 and the drive unit 18 are brought into conduction.

The period from time t = 0 to t = T1 is a rising period. During this period, as shown in FIG. 5F, the potential Vr of the boosted voltage applied to the point B by the booster circuit 17 gradually increases with time. In addition, since the switch 20 is in the ON state during this rising period, the potential Vd of the input voltage applied to the drive unit 18 also rises according to the boosted voltage, as shown in FIG. However, during this period, the boosted voltage does not reach the predetermined potential VT, and the drive unit 18 does not drive the display body 19.

  At time t = T1, the rising period ends, and as shown in FIGS. 4D and 4F, the potential Vr of the boosted voltage and the potential Vd of the input voltage of the driving unit 18 reach the predetermined potential VT. Subsequently, a period from time t = T1 to t = T2 is a driving period. In this drive period, first, the CPU 11 reads a file used for image display from the storage unit 21 and generates image data on the RAM 13. Then, the CPU 11 outputs this image data to the drive unit 18. The driving unit 18 drives the display element of the display body 19 by applying a driving voltage between the plurality of pixel electrodes PE and the common electrode CE of the display body 19 according to the image data. During this drive period, as shown in FIGS. 6D and 6F, the booster circuit 17 applies the input voltage of the predetermined potential VT to the drive unit 18, and as shown in FIG. 18 drives each display element of the display body 19 with the drive voltage using this input voltage.

Then, as shown in FIG. 5E, at time t = T2, the driving of the display element for displaying an image on the display body 19 by the driving unit 18 is finished, and the driving period is finished here. At this time, the CPU 11 switches the switch 20 from the on state to the off state, as shown in FIG. On the other hand, the CPU 11 causes the booster circuit 17 to continue boosting without stopping the boosting. When the switch 20 is turned off, the booster circuit 17, the drive unit 18 and the display body 19 are not connected to each other. Therefore, as shown in FIG. The voltage potential Vd decreases with time from time t = T3 to t = T4 after the driving period. On the other hand, since the boosting by the booster circuit 17 is continued, the potential Vr of the boosted voltage is maintained at VT as it is during this period.
The above is the description of the operation of the display device 10 when the booster circuit 17 starts boosting when the display device 10 displays the first image, that is, when the switch 20 is turned on.

  Next, an operation when the display device 10 displays the second image on the display body 19 will be described. As shown in FIG. 3B, since the CPU 11 does not stop the boosting by the booster circuit 17 at the time T2 when the driving period ends when the first image is displayed, until the time T3 when the key 15 is operated. The boosting by the booster circuit 17 is continued. As shown in FIG. 11A, when the user operates the key 15 at time t = T3 to instruct the display of the second image, as shown in FIG. Then, a control signal is output to the switch 20 to switch it from the off state to the on state. As a result, the switch 20 is turned on, and the booster circuit 17, the drive unit 18, and the display body 19 are conducted.

Due to this conduction, the boosted voltage boosted by the booster circuit 17 is applied to the drive unit 18 as an input voltage at time t = T3. At this time t = T3, since the booster circuit 17 has already boosted the power supply voltage to the predetermined potential VT, as soon as the switch 20 is turned on, the potential Vd of the input voltage of the drive unit 18 is also set to a potential corresponding thereto. Become. Therefore, the potential Vd of the input voltage of the drive unit 18 immediately reaches the potential VT equivalent to the potential Vr of the boosted voltage. Accordingly, the input voltage Vd reaches the predetermined potential VT in the period (T4a-T3) shorter than the rising period (T4-T3) in the display device 100.
As shown in FIG. 5F, when the switch 20 is turned on, the load on the display device 10 is increased by an amount corresponding to the drive unit 18 and the display body 19, so that the potential Vr of the boosted voltage is temporarily changed. Although it has decreased from the predetermined potential VT, the potential Vr promptly returns to the predetermined potential VT.

Then, at time t = T4a, when the potential Vd of the input voltage of the drive unit 18 reaches the predetermined potential VT, the drive unit 18 uses this input voltage to drive up to time T5a in the drive period as described above. Each display element is driven in order to display an image on the display 19. That is, the CPU 11 switches the switch 20 from the off state to the on state while continuing the boosting by the boosting circuit 17 and causes the drive unit 18 to drive the display element group with the boosted voltage, and after the driving ends. It functions as control means for switching the state of the switch 20 so as to change the switch 20 from the on state to the off state.

  In this way, at the time of the second image display, the user is instructed to display an image, and the CPU 11 turns on the switch 20 to make the drive unit 18 and the display body 19 and the booster circuit 17 conductive. When in the state, the booster circuit 17 has already boosted the power supply voltage to the predetermined potential VT. Thus, unlike the display device 100, when the switch 20 is turned on, the drive unit 18 starts driving after an instruction to display an image without requiring a rising period when boosting is also started. The same effect can be obtained when the display device 10 displays the third and subsequent images following the above two images for the same reason that the effect of shortening the period until the image can be obtained. be able to.

According to the embodiment described above, after the driving of the display body 19 for displaying an image by the driving unit 18 is completed, the driving for displaying the next image is started. Since the booster circuit 17 is continuously boosting, a rise period until the booster circuit 17 rises to the predetermined potential VT does not occur during this boosting. Therefore, when the second and subsequent images are displayed, as soon as the switch 20 is turned on, the input voltage of the drive unit 18 rises to the boosted voltage, and the drive unit 18 can immediately display an image. it can. Therefore, even when the display device 10 is used to switch pages one after another and display an image, the user is not caused to wait.
Also, in the period other than the rising period and the driving period, the booster circuit 17 continuously boosts the voltage, but since the switch 20 is in the off state during this period, the switch 20 is always in the on state. Compared to the case, the power consumption by the drive unit 18 is extremely small.

(C) Modification The above embodiment may be modified as follows. Specifically, the following modifications are mentioned, for example. These modifications can be appropriately combined with each other.
(C-1) Modification 1
In the embodiment described above, the booster circuit 17 continuously boosts the voltage even during the period in which the drive unit 18 is not driven, such as the period from time t = T2 to t = T3. On the other hand, a period in which the voltage is not boosted may be provided in a period after the driving period. This aspect will be described below.

  For example, the display device 10 may display an image according to image data including a plurality of pages of images such as an electronic book. In such image data, a page number is assigned to each of a plurality of images (pages) as a display order, and the display device 10 stores the page number and image data of each page in association with each other in the storage unit 21. The images are displayed in the display order according to the page number. Each time the user operates the key 15 to switch pages, the CPU 11 switches the page to display an image, and eventually displays the image of the last page, that is, the image with the last display order. When the user finishes reading the image on the last page, the book is read. When the user finishes reading the book, it can be said that the frequency of using the display device 10 as it is or turning off the power is relatively high.

Therefore, in the present modification, when the display device 10 displays an image according to image data including a plurality of images, the drive unit 18 drives for displaying the image of the last page (the image with the display order at the end). When the operation is finished, the CPU 11 turns off the switch 20 and the booster circuit 1
7 is also stopped. In other words, in the present modification, when the image to which the last display order is assigned is displayed by driving the drive unit 18 among the plurality of images to which the display order is assigned, the CPU 11 performs boosting by the booster circuit 17. It functions as a control means for stopping. When another image is displayed after boosting is stopped as described above, the CPU 11 performs the same control as that for displaying the first image.
Further, in this aspect, the last display order may be assigned to an intermediate page instead of assigning the last display order to the image of the last page in the image data. For example, when the user specifies in advance which page of the images of a plurality of pages is to be browsed, the CPU 11 may assign the display order at the end to the image. This is because it is designated by the user that the image is viewed last. If the document is composed of a plurality of chapters, the user is likely to browse in chapter units. Therefore, the last display order may be assigned to the image of the last page of each chapter. In short, the last display order may be assigned to the image that the user will view last. The display order at the end may be assigned by being specified by the user, or may be assigned at the manufacturing stage in the case of a commercially available book or the like.
As described above, since the display device appropriately stops the boosting of the booster circuit 17, the power consumption in the booster circuit 17 is reduced, so that the power saving effect of the display device 10 as a whole can be further enhanced. .

(C-2) Modification 2
Further, the CPU 11 may stop the boosting of the booster circuit 17 unless there is an instruction to display an image until a predetermined period has elapsed after the driving by the driving unit 18 is completed. When the display element is not driven for a long period of time, for example, the amount of information such as characters included in the image displayed on the display body 19 is large, and the user can view it. It can be considered that it takes time or the user has left the display device 10 left unattended. For this reason, if there is no instruction to display an image for a predetermined period with respect to the display device 10, it can be assumed that there is no instruction to display an image for the time being. At this time, if the CPU 11 causes the booster circuit 17 to stop boosting, the power saving effect can be further enhanced. In this aspect, the CPU 11 includes a timer as a time measuring means, and starts time measurement using the timer from the end time of the driving period. If it is not instructed to display another image until the predetermined period set by the design stage or the user has elapsed, the CPU 11 stops the boosting of the booster circuit 17. That is, the CPU 11 of the present modification continues the boosting by the booster circuit 17 until the predetermined period elapses after the driving by the drive unit 18 ends, and when the predetermined period elapses without an instruction to display an image, the booster circuit It functions as a control means for stopping the boosting by 17.

FIG. 4 is a time chart showing an example of operations of the booster circuit 17 and the drive unit 18. Here, the predetermined period from the end of the driving period to the stop of boosting is Δth.
As shown in the figure, when the driving period D1 ends at time t = T21, the CPU 11 keeps boosting in the booster circuit 17 while counting by the timer. Then, at time T21 + Δt1 when the predetermined period Δth has not elapsed since time t = T21, when the user gives an instruction to display an image (that is, Δt1 <Δth), the CPU 11 starts driving the drive unit 18 again. In this case, as in the embodiment, the CPU 11 causes the booster circuit 17 to continue boosting during the drive periods D1 and D2. Subsequently, if the user has not instructed to display an image by the end of the driving period D2 at time t = T22 and the elapse of a predetermined period Δth from that time, the CPU 11 performs the boost circuit at time t = T22 + Δth. 17 stops the boosting. Also in this aspect, the CPU 11 turns on the switch 20 when the drive unit 18 drives the display element group, and turns off the switch 20 when the drive unit 18 does not drive the display element group.

(C-3) Modification 3
Further, the CPU 11 may stop the boosting every time a predetermined period elapses after the boosting circuit 17 starts the boosting. As this predetermined period, for example, a period in which driving of the driving unit 18 for displaying an image and browsing of the image by the user can be performed a plurality of times is appropriate. There is a certain limit in the period during which the user continues to browse a plurality of images one after another using the display device 10, and for example, the user often forgets to turn off the display device 10. Therefore, the display device 10 stops driving the drive unit 18 and stops boosting the booster circuit 17 every time a predetermined period elapses after the booster circuit 17 starts boosting. In this way, for example, even when the user forgets to turn off the display device 10, the power consumption can be reduced. In this embodiment, the CPU 11 includes a timer as a time measuring means, and starts time measurement using the timer from the time when the boosting circuit 17 starts boosting. Then, every time a predetermined period set by the design stage or the user elapses, the boosting of the booster circuit 17 is stopped. That is, the CPU 11 of this modification example continues the boosting by the boosting circuit 17 until the predetermined period elapses after the boosting by the boosting circuit 17 is started, and stops the boosting by the boosting circuit 17 when the predetermined period elapses. It functions as a control means.

FIG. 5 is a time chart showing an example of operations of the booster circuit 17 and the drive unit 18. Here, TA is the predetermined period from the start of boosting to the stop thereof.
As shown in the figure, the CPU 11 starts boosting of the boosting circuit 17 and driving by the driving unit 18 at time t = T31, and measures the time by a timer, and performs the boosting circuit 17 and the driving unit similarly to the embodiment. 18 is controlled. Then, at time t = T31 + TA when a predetermined period TA has elapsed from time t = T31, when the CPU 11 confirms that the drive unit 18 is not being driven, the booster circuit 17 stops boosting. At this time, the reason why the CPU 11 confirms that the drive unit 18 is not driven is that it does not hinder the drive of the drive unit 18 related to image display. When the driving unit 18 is driven, the display device 10 is actively used by the user, and it is not appropriate to stop the boosting here, so the CPU 11 continues the boosting. It is only necessary to start timing again.
In the example of FIG. 5, when the predetermined period TA has elapsed, the drive unit 18 is not driven, and thus the CPU 11 causes the booster circuit 17 to stop boosting. Then, at time T32 when the next image display is instructed, the CPU 11 causes the booster circuit 17 to start boosting and starts counting by the timer again. Also in this aspect, as in the embodiment, the CPU 11 turns on the switch 20 when the drive unit 18 drives the display element group, and turns off the switch 20 when the drive unit 18 does not drive the display element group. . Note that the operation of the CPU 11 confirming that the drive unit 18 is not driven when the predetermined period TA has elapsed is not essential, and the booster circuit 17 may be allowed to stop boosting whenever the predetermined period TA has elapsed. .

(C-4) Modification 4
In the configurations of Modifications 2 and 3, the CPU 11 may determine the length of the predetermined period according to the type of image to be displayed. For example, if the number of characters included in one image is large, the period during which the user keeps displaying the page becomes long. On the other hand, if there is a lot of visual information such as an illustration, the page is relatively short. Can be switched. Therefore, the CPU 11 determines the type of image to be displayed on the display body 19 and determines the length of the predetermined period according to the determined type of image. Hereinafter, this configuration will be specifically described.

First, the case where it applies to the structure of the modification 2 is demonstrated.
In this configuration, the display device 10 stores the image type and the period in the storage unit 21 in association with each other in a table format. In this table, for example, “novel”, “comic”, and “illustration” are described as image types, and for each period from the end of the driving period to the stop of boosting (predetermined period) ) Are associated with periods “tp”, “tq”, and “tr”, respectively. At this time, the number of characters in each image is "Novel"
>“Comic”> “illustration”, and the time required for the user to view it is also considered to be in the same order, so the periods “tp”, “tq”, “tr” The magnitude relationship of tp>tq> tr.
The various files stored in the storage unit 21 include type information representing the type of the image. The type information may be set in advance at the manufacturing stage in the case of a commercially available electronic book, or may be configured by the user.

  When the CPU 11 displays an image, when the file is read from the storage unit 21, the type of the image is determined according to the type information associated therewith. That is, the CPU 11 functions as a determination unit that determines the type of image. The CPU 11 generates image data based on the read file and outputs the image data to the drive unit 18. On the other hand, the CPU 11 reads the table from the storage unit 21. In this table, the period associated with the determined image type Specify the length of. For example, when the CPU 11 determines that the image type is “novel”, the time “tp” is specified as the length of the period. Then, the CPU 11 starts measuring the period after the boosting of the booster circuit 17 is stopped by a timer provided therein. The CPU 11 continues the boosting by the booster circuit 17 until the time tp elapses, and stops the boosting by the booster circuit 17 when the time tp elapses without an instruction to display an image. That is, the CPU 11 determines the type of image displayed by driving the driving unit 18, and sets the period stored in the storage unit 21 in association with the determined type as the predetermined period until the predetermined period elapses. Functions as a control means for continuing the boosting by the boosting circuit 17.

Next, the case where it applies to the structure of the modification 3 is demonstrated.
Also in this configuration, the display device 10 stores the image type and the period in the storage unit 21 in association with each other in a table format. However, in this table, a period is set such that the drive unit 18 is driven and the user's image is viewed a plurality of times. When displaying an image, the CPU 11 specifies the type of the image and specifies the length of the predetermined period according to the contents of the table. Then, the CPU 11 starts boosting by the booster circuit 17 and starts timing by a timer. The CPU 11 continues the boosting by the boosting circuit 17 until the specified period elapses after starting the boosting, and stops the boosting by the boosting circuit 17 when the predetermined period elapses.
According to this modification, the display device determines a period until the boosting by the booster circuit 17 is stopped according to the type of the image. Therefore, when the period required for the user to browse the image is predicted to be long. If it is predicted that the period until the boost stop will be lengthened and the period required for browsing is predicted to be short, the period until the boost stop can be shortened. As a result, the power consumption of the entire display device can be further reduced while shortening the period required to display the image by continuing the boosting of the booster circuit 17 outside the driving period.

(C-5) Modification 5
In the above-described embodiment, the display body 19 is an electrophoretic element type display body, but may be a display body using a display element other than this. In short, any display body including a display element group that displays an image corresponding to the driving voltage and continues to display the image even when the driving voltage is not applied after the image is displayed may be used.
Further, the booster circuit 17 is not limited to a booster switching regulator, and may be a booster such as a charge pump type. If the booster circuit requires a rising period and is performed only during the period in which the driving unit drives the display element, the same effect as described above can be obtained in that the rising period is shortened.
In the embodiment described above, the display device 10 is a thin and highly portable display device. However, the display device 10 only needs to be able to display an image as described in the embodiment, and may be a PDA (Personal Digital Assistant), a personal computer, It may be a display device such as a mobile phone.

It is a block diagram which shows the structure of a display apparatus. It is the figure which showed the structure of the display body typically. It is a time chart which shows the mode of operation | movement of each part of an apparatus, and a state transition when a display apparatus displays an image on a display body. 10 is a time chart showing how the booster circuit and the drive unit operate in Modification 2. 10 is a time chart showing the operation of a booster circuit and a drive unit in Modification 3. It is the figure which showed an example of the hardware constitutions of the conventional display apparatus. It is a time chart which shows the operation | movement of each part of an apparatus, and the mode of the state transition, when the conventional display apparatus displays an image on a display body.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Display apparatus, 11 ... CPU, 12 ... ROM, 13 ... RAM, 14 ... I / O, 15 ... Key, 16 ... Power supply part, 17 ... Booster circuit, 18 ... Drive part, 19 ... Display body, 191 ... 1st 1 board | substrate, 192 ... binder, 193 ... 2nd board | substrate, 20 ... switch, 21 ... memory | storage part.

Claims (6)

Boosting means for boosting the voltage of the power supply;
When a drive voltage is applied, an image corresponding to the drive voltage is displayed, and after the image is displayed, a drive unit that drives a display element group that continues to display the image even when the drive voltage is not applied;
One end is connected to the boosting means and the other end is connected to the driving means, and the boosting means and the driving means are electrically connected to each other, or the boosting means and the driving means are not electrically connected to each other. A switch that is in either state,
While the boosting by the boosting unit is continued, the switch is turned on from the OFF state, and the driving unit is driven by the boosted voltage, and the switch is turned on after the driving is finished. And a control unit that switches a state of the switch so as to change from the on state to the off state. The control unit stops boosting by the boosting unit when an image to which the last display order is allocated is displayed by driving the driving unit among a plurality of images to which the display order is allocated. The drive device according to claim 1. The control means continues the boosting by the boosting means until the predetermined period elapses after the driving by the driving means ends, and when the predetermined period elapses without an instruction to display an image, the boosting by the boosting means The driving device according to claim 1, wherein the driving device is stopped. The control means continues the boosting by the boosting means until the predetermined period elapses after starting the boosting by the boosting means, and stops the boosting by the boosting means when the predetermined period elapses. The drive device according to claim 1 or 2. The control means includes
Storage means for storing the image type and the period in association with each other;
Determination means for determining the type of image,
The type of image displayed by driving the driving unit is determined by the determining unit, and the period stored in the storage unit in association with the determined type is the predetermined period until the predetermined period elapses. The driving device according to claim 3 or 4, wherein the boosting by the boosting means is continued. Storage means for storing image data;
When a drive voltage is applied, an image corresponding to the drive voltage is displayed, and after displaying the image, a display body having a display element group that continues to display the image even when the drive voltage is not applied;
A display device comprising: the drive device according to claim 1, wherein the display device group of the display body is driven in accordance with image data stored in the storage unit.

Images