JP6724312B2 - Liquid crystal display - Google Patents

Description

The present invention relates to a liquid crystal display device.

2. Description of the Related Art Conventionally, there is a liquid crystal display device that displays an image by controlling light transmission by applying a voltage to each pixel of a liquid crystal panel to change an alignment state. The liquid crystal is duty-driven to control the orientation state at a predetermined frequency (frame frequency), and the display image is updated on the display screen at the predetermined frequency.

If this frame frequency is low, it may be perceived that the display flickers or the display switching fluctuates. On the other hand, even if the frame frequency is too high, the power consumption only increases and the viewer of the display screen does not recognize the change. On the other hand, Patent Document 1 discloses a technique in which, when a display with a small number of display colors is performed on a color liquid crystal screen, the display is performed at a lower frame frequency than usual. In addition, Patent Document 2 discloses a technique for changing the frame frequency between the time of displaying a moving image and the time of displaying other than the moving image. Patent Document 3 discloses a technique for reducing the power consumption during standby by improving the contrast during operation by setting different frame frequencies on the display screen of a mobile phone during operation and during standby. There is.

JP, 2002-149118, A JP, 2010-187192, A Japanese Patent No. 5237979

However, when the display image is intermittently switched, such as when the display state is switched in a plurality of liquid crystal pixels all at once, the voltage rises depending on the waveform of the voltage applied to the liquid crystal pixels and the response speed of the liquid crystal to the applied voltage. The fall may vary. Such a state does not correspond to the switching of the display data and the mode, and there is a problem that it leads to flicker of the display image.

An object of the present invention is to provide a liquid crystal display device capable of more stable display when changing a display image while suppressing an increase in power consumption.

In order to achieve the above object, the present invention provides
Display means having a liquid crystal display screen,
Driving means for performing display at the frame frequency set on the liquid crystal display screen,
And drive dynamic control means,
Equipped with
The drive control means,
When switching the display content of the liquid crystal display screen from the first image to the second image,
After the time point at which the display of the second image starts from the first timing that is any timing in the period after the time point at which the display of the first image starts and before the time point at which the display of the first image ends To the second timing, which is any one of the timings from the time until the end of the display of the second image,
The liquid crystal display device is characterized in that the frame frequency in the switching period is raised more than that outside the switching period .

According to the present invention, in a liquid crystal display device, there is an effect that it is possible to more stably display when changing a display image while suppressing an increase in power consumption.

It is a block diagram which shows the function structure of the electronic timepiece of embodiment of this invention. It is a figure which shows the example of a change of the segment voltage output at the time of scroll display. It is a figure which shows the example of a change of the frame frequency at the time of blinking of a liquid crystal display. It is a flow chart which shows the control procedure of the display drive control processing in the electronic timepiece of this embodiment.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a block diagram showing a functional configuration of an electronic timepiece 1 which is an embodiment of a liquid crystal display device of the present invention.

The electronic timepiece 1 is a small electronic timepiece that digitally displays on a liquid crystal screen, for example, an electronic wristwatch, and includes a CPU 41 (Central Processing Unit), a ROM 42 (Read Only Memory), a RAM 43 (Random Access Memory), and an oscillator. A circuit 44, a frequency dividing circuit 45, a clock circuit 46, an operation receiving unit 47 (operation receiving unit), a display unit 48, a display driver 49, a power supply unit 50 and the like are provided.

The CPU 41 centrally controls the overall operation of the electronic timepiece 1. Further, the CPU 41 outputs a control signal to the display driver 49 to control the display state of the display unit 48.

The ROM 42 stores various programs and initial setting data for the electronic timepiece 1 to perform various operations. The programs stored in the ROM 42 include a program 42a for performing a control operation related to the display state. In cases other than the case where the display is paused in the power saving mode (sleep mode) or the like, the program 42a read from the ROM 42 is loaded into the RAM 43, is resident, and is continuously executed by the CPU 41. As the ROM 42, in addition to a mask ROM, a rewritable nonvolatile memory such as a flash memory may be partially used.

The RAM 43 is a volatile memory and provides the CPU 41 with a working memory space. The RAM 43 also stores various temporary data and setting data.

The oscillation circuit 44 oscillates a signal having a predetermined frequency, for example, 32 kHz, and outputs the signal (oscillation signal). The oscillation circuit 44 is not particularly limited, but includes, for example, a small-sized and low power consumption crystal oscillation circuit.

The frequency dividing circuit 45 divides this oscillation signal to generate and output a necessary frequency signal. The frequency dividing circuit 45 is capable of appropriately switching the frequency dividing ratio and outputting signals of different frequencies according to a command from the CPU 41. The frequency signal output from the frequency dividing circuit 45 includes the frequency signal used for the time counting operation of the time counting circuit 46.

The clock circuit 46 is, for example, a counter, and counts the current date and time by counting the number of pulse signals input from the frequency dividing circuit 45 and adding the count to the initially set date and time. The current date and time data stored in the clock circuit 46 can be corrected by a control command from the CPU 41. The clock circuit 46 may be configured to store the date and time counted by software by a rewritable storage means.

The operation receiving unit 47 includes a plurality of keys and push button switches, and when these keys and push button switches are operated, the operation contents are converted into electric signals and output to the CPU 41 as input signals.

The display unit 48 is a digital display unit having a liquid crystal screen 48a (liquid crystal display screen; LCD, display means) for performing liquid crystal display and a drive circuit 48b (drive means) thereof. The display unit 48 displays a current date and time, a menu relating to various functional operations, a status, and a selected function according to a control signal from the CPU 41. The LCD 48a is capable of displaying in accordance with the functional operation that can be executed by the electronic timepiece 1, and here, dots capable of simple scroll display or animation display of predetermined characters (for example, alphabets and katakana) and figures. A matrix type is used. The dot matrix method is not limited to a concrete method such as STN liquid crystal or TFT liquid crystal, but is duty-driven by a combination of a common voltage waveform and a segment voltage waveform applied to each pixel by the drive circuit 48b. It is a thing.

The display driver 49 receives a control signal (display image data corresponding to each pixel of the LCD) from the CPU 41 and outputs an operation signal to the drive circuit 48b of the display unit 48 at an appropriate timing. Further, in the electronic timepiece 1 according to the present embodiment, the display driver 49 can change the duty driving frequency (frame frequency) by the drive circuit 48b of the display unit 48 under the control of the CPU 41.
The CPU 41 and the display driver 49 constitute drive control means.

The power supply unit 50 supplies a predetermined operating voltage to the CPU 41, and also supplies each voltage necessary for the drive circuit 48b of the display unit 48 to drive the LCD 48a. For example, to drive the display unit 48 at 1/3B (bias), the power supply unit 50 uses the ground voltage (V0) and three types of drive voltages (V3, V2=V3×2/3, V1=V3). X 1/3) is supplied to the display unit 48.

Next, the display operation of the electronic timepiece 1 of this embodiment will be described.
In the display unit 48 of the electronic timepiece 1, as described above, the dot matrix type LCD 48a is duty-driven to switch ON/OFF state of each pixel (that is, light transmission/non-transmission). Further, in the lighting state, it may be possible to take a plurality of gradations of brightness (transmission state). Note that, here, in the case where a liquid crystal screen that allows light to pass through in a state where no voltage is applied to the pixel is used as a display state in general, a pixel to which a voltage is applied and does not allow light to pass is described as a lit state. To do.

Here, normally, duty driving is performed at a frequency near a lower limit frequency at which flicker is not generally recognized by the user of the electronic timepiece 1, for example, a frame frequency of 64 Hz. An increase in power consumption can be suppressed by not increasing the frame frequency more than necessary.

Further, in particular, when the liquid crystal screen 48a is small as in an electronic wristwatch, all the necessary characters are displayed by scrolling the characters to be displayed, for example, the city name indicating the current position. Further, in the setting of the alarm operation, the part selected as the setting target is displayed in blinking. The scroll speed is set to, for example, about 8 to 16 Hz, and the blinking operation is set to, for example, about 1 to several Hz.

When the scroll display or blinking operation is performed at such a speed, at the position where the pixel is switched on/off, in the frame cycle immediately after switching from the delay in the response of the liquid crystal, the presence/absence of lighting is completely detected in one duty driving. It may not switch. Further, the timing of switching the presence/absence of lighting according to different common voltage waveforms easily varies depending on the difference in the common voltage waveforms.

When many pixels are turned on or off at a frequency that can be perceived by humans (that is, less than about 30 Hz) repeatedly in a short time (that is, about 2 Hz or more) at the same time, it is easy to perceive such a variation in the presence or absence of lighting. .. Therefore, in the present embodiment, when the simultaneous display switching operation in such a frequency band is performed, the frame frequency for duty driving is increased only during a period before the predetermined period and after the predetermined period of the switching timing.

FIG. 2 is a diagram showing an example of changing the segment voltage output during scroll display.
A normal segment voltage waveform WP1 is shown in the upper stage, and a segment voltage waveform WP2 according to the present invention is shown in the lower stage.

Normally, the frame frequency is kept constant within a short time range, for example, within the same display mode, as shown by the segment voltage waveform WP1. On the other hand, in the electronic timepiece 1, as shown by the segment voltage waveform WP2, when there is a change in the image to be displayed by scrolling or the like (timing (t2)), a predetermined frame period is set for the timing. Before the time (first predetermined time) corresponding to the cycle, here, from the timing t1 which is the beginning two cycles before, after the time (second predetermined time) corresponding to the predetermined cycle in the normal frame cycle, here, The frame frequency is doubled (integer multiple) outside this period until timing t3 which is the beginning after two cycles. As described above, in the case of scroll display, the timing for moving the display position is determined in a predetermined cycle, so the frame frequency is temporarily increased in each cycle.

FIG. 3 is a diagram showing an example of changing the frame frequency when the liquid crystal display blinks.

When the blinking operation of the display is periodically performed on the liquid crystal screen 48a, the frame frequency is changed from a predetermined cycle (time) before to a predetermined cycle (time) after the lighting operation or the extinguishing operation is performed twice within the cycle. Is temporarily switched from 64 Hz to 128 Hz. Here, assuming that the lighting period and the extinguishing period have the same length, the frame frequency changing periods also occur at equal intervals. When the lighting period and the extinction period have different lengths, the interval from the frequency change period related to the lighting operation to the frequency change period related to the extinction operation, and the frequency change period related to the extinction operation to the frequency change period related to the lighting operation Will have different intervals.

Here, by setting the above-described predetermined period to be an integer, the synchronization timing (the timing at the beginning of each frame period) is the same in the period when the frame frequency is not raised and when the frame frequency is raised. It is desirable to keep the timing at the beginning of the clock signal. As a result, during the period in which the frame frequency is increased, the same image data is simply output twice in pairs to easily control the display content. That is, in the example of FIG. 2, the image data before moving by scrolling is output four times between the timing t1 and the timing t2, and the image data after moving by scrolling is output four times between the timing t2 and the timing t3. To be done. After timing t3, the image data after the movement by scrolling is output for each frame period.

Further, even when the display switching command is acquired only once by the user operation, the frame frequency can be increased only before and after the timing. In this case, since the display switching command can be input irregularly continuously, if the next display switching command is acquired before the timing of returning the frame frequency, the display is switched to the next display while increasing the frame frequency. Can be done. Examples of the one-time display switching command include switching of display modes and selection movement of menu screens.

FIG. 4 is a flowchart showing a control procedure by the CPU 41 of the display drive control processing in the electronic timepiece 1 of this embodiment.
The display drive control process is continuously performed during the period when the display unit 48 of the electronic timepiece 1 is displaying.

When the display drive control process is started, the CPU 41 acquires the display data after a predetermined frame (step S11). The CPU 41 determines whether the current display state is blinking display, scroll display, or display switching by a user operation (step S12). If it is determined to be neither (“NO” in step S12), the process of the CPU 41 proceeds to step S17.

When it is determined to be either (“YES” in step S12), the CPU 41 determines whether or not there is a difference between the acquired frame display data and the display data of the frame immediately before the acquired frame display data. Yes (step S13). When it is determined that there is a difference (“YES” in step S13), the CPU 41 sets the frame frequency to 128 Hz (step S14). At this time, the CPU 41 changes the clock frequency itself output from the frequency dividing circuit 45 to operate at a frequency according to the high-speed frame frequency only when necessary. Then, the processing of the CPU 41 moves to step S17.

When it is determined that there is no difference between the acquired frame display data and the immediately preceding frame display data (“NO” in step S13), the CPU 41 determines whether or not there is a difference for a predetermined number of frames in a row. Is determined (step S15). When it is determined that there is no difference in the predetermined number of frames in a row (“YES” in step S15), the CPU 41 sets the frame frequency to 64 Hz (step S16). Then, the processing of the CPU 41 moves to step S17.

When it is determined that the number of consecutive times when it is determined that there is no difference between the frame display data is not the predetermined number of frames (“NO” in step S15), the processing of the CPU 41 proceeds to step S17.

When the processing shifts to the processing of step S17 from the processing of any of steps S12 and S14 to S16, the CPU 41 outputs the frame display data acquired at the clock frequency corresponding to the set frame frequency to the display driver 49 (step). S17). Then, the processing of the CPU 41 returns to step S11.

As described above, the electronic timepiece 1 according to the present embodiment has the display unit 48 having the liquid crystal screen 48a, the drive circuit 48b for the display unit 48 for performing display at the frame frequency set on the liquid crystal screen 48a, and the liquid crystal screen 48a. During the switching period from the first predetermined time before the second predetermined time after the timing of switching the display content of the above, the CPU 41 and the display driver 49 as drive control means for increasing the frame frequency above the outside of the switching period are Prepare
In this way, the display operation is performed twice in a short time by increasing the frame frequency only at the time of switching the display content in which the flicker and the variation of the lighting timing are conspicuous, and the common voltage waveform is selected for each pixel. By reducing the width of the timing deviation, the display problem is suppressed, and the increase in power consumption depending on the frame frequency is not caused more than necessary. That is, it is possible to display more stably when changing the display image while suppressing an increase in power consumption.

Further, the CPU 41 and the display driver 49 as the drive control means are at least one of changing the display position related to the scroll display of the display image and switching between the lighting state and the extinguishing state related to the blinking operation of the display image. When performing, increase the frame frequency.
In this way, particularly when performing image display in which the positions of the lighted pixels change intermittently and simultaneously, by increasing the frame frequency in accordance with the timing, it is possible to more efficiently display the image compared to the increase in power consumption. Stability can be increased.

Further, the CPU 41 and the display driver 49 as drive control means are provided with an operation accepting unit 47 for accepting a user operation, and when switching to a predetermined display content according to the content of the user operation accepted by the operation accepting unit 47. Increase the frame frequency.
As described above, also regarding the switching of the display image in response to the user operation that is performed irregularly and intermittently, similarly, the frame frequency is increased only during the switching period, so that both the reduction in power consumption and the stable display are achieved. Can be done.

Further, the CPU 41 and the display driver 49 as the drive control means set the frame frequency in the switching period of the display image, here 128 Hz, to the frame frequency outside the switching period, which is an integral multiple of 64 Hz, that is, double here. .. This makes it possible to easily switch the display image data without complicating the interpolation processing between the display image data and the phase adjustment during duty driving.

The present invention is not limited to the above embodiment, and various modifications can be made.
For example, in the above-described embodiment, the image switching timing is detected by referring to the image data, but when the switching frequency (switching cycle) is set in advance, the image is actually displayed. Instead of referring to the data, the elapsed time after the switching of the frame frequency related to the first switching timing may be counted, and the frame frequency may be switched for a predetermined time every switching cycle.

Further, in the above embodiment, the frame frequency is changed between 64 Hz and 128 Hz, but it may be another frequency or another frequency ratio.

Further, in addition to the scroll display, the blinking operation, and the image switching performed once by the user operation described in the above embodiment, a reduction operation or a rotation operation of the display image, an operation of switching a plurality of kinds of display contents in a predetermined cycle, The present invention can be effectively applied to the case where the display of status information is periodically updated. Further, the frequency may be switched based on only the change in the image data to be displayed regardless of these target operations. In this case, if the displayed image always changes in a moving image, the frame frequency simply remains increased, but if the image does not change even in the moving image, or if the user manually pauses. In some cases, the frame frequency returns to the normal low frequency as well.

Further, although an electronic timepiece is described as an example in the above embodiment, the present invention can be applied to various liquid crystal display devices that perform display using a liquid crystal screen. For example, a liquid crystal display device having a digital display screen of various sensors, a display screen of statuses and menus of various home appliances, a display screen capable of displaying a plurality of still images such as an electronic signboard and a digital photo frame, and the like can be given.
In addition, the specific configurations, operation contents, procedures, and the like shown in the above embodiments can be appropriately changed without departing from the spirit of the present invention.

Although some embodiments of the present invention have been described, the scope of the present invention is not limited to the above-described embodiments, and includes the scope of the invention described in the claims and the equivalent scope thereof. ..
Hereinafter, the inventions described in the claims attached to the application of this application will be additionally described. The claim numbers listed in the appendices are as defined in the claims initially attached to the application for this application.

[Appendix]
<Claim 1>
Display means having a liquid crystal display screen,
Driving means for performing display at the frame frequency set on the liquid crystal display screen,
Drive control means for increasing the frame frequency above the outside of the switching period during the switching period from the first predetermined time before the second predetermined time after the timing of switching the display content of the liquid crystal display screen;
A liquid crystal display device comprising:
<Claim 2>
The drive control means changes the frame frequency when changing at least one of the display position related to the scroll display of the display image and the switching between the lighting state and the non-lighting state related to the blinking operation of the display image. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is raised.
<Claim 3>
Equipped with operation acceptance means for accepting user operations,
The liquid crystal display according to claim 1 or 2, wherein the drive control unit raises the frame frequency when switching to a predetermined display content according to the content of the user operation received by the operation receiving unit. apparatus.
<Claim 4>
The liquid crystal display device according to claim 1, wherein the drive control unit sets the frame frequency in the switching period to an integral multiple of the frame frequency outside the switching period.

1 Electronic clock 41 CPU
42 ROM
42a program 43 RAM
44 oscillator circuit 45 frequency divider circuit 46 clock circuit 47 operation receiving unit 48 display unit 48a liquid crystal screen 48b drive circuit 49 display driver 50 power supply unit

Claims (3)

Display means having a liquid crystal display screen,
Driving means for performing display at the frame frequency set on the liquid crystal display screen,
And drive dynamic control means,
Equipped with
The drive control means,
When switching the display content of the liquid crystal display screen from the first image to the second image,
After the time point at which the display of the second image starts from the first timing that is any timing in the period after the time point at which the display of the first image starts and before the time point at which the display of the first image ends To the second timing, which is any one of the timings from the time until the end of the display of the second image,
A liquid crystal display device , wherein the frame frequency in the switching period is increased more than that outside the switching period . The drive control means changes the frame frequency when changing at least one of the display position related to the scroll display of the display image and the switching between the lighting state and the non-lighting state related to the blinking operation of the display image. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is raised. Equipped with operation acceptance means for accepting user operations,
The liquid crystal according to claim 1 or 2 , wherein the drive control means raises the frame frequency when switching to a predetermined display content according to the content of the user operation received by the operation receiving means. Display device.

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