JP3523378B2 - Liquid crystal drive and electronic equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal drive device for driving a liquid crystal display panel, and more particularly to a technique effective when applied to an electronic device such as a mobile phone.

[0002]

2. Description of the Related Art A liquid crystal display panel (also referred to as a liquid crystal display), which is an example of a display, includes a plurality of common lines and segment lines arranged so as to intersect with the common lines. A liquid crystal cell is arranged at the intersection of the. A liquid crystal driving device for driving such a liquid crystal display panel is provided with a common liquid crystal driver for driving a common line and a segment liquid crystal driver for driving a segment line. The segment liquid crystal driver outputs drive information in units of lines. At this time, the common liquid crystal driver drives a plurality of common lines in a time division manner.

As an example of a document describing a liquid crystal display, "Electronic Communication Handbook (47th Edition), published by Ohmsha Co., Ltd. on August 20, 1983, is available.
Page 2).

[0004]

In a liquid crystal display panel applied to a mobile phone, in addition to character information such as a telephone number, graphic display, that is, icon display is performed in order to visually recognize an operation. Although the character information is displayed in a dot matrix, the icon does not need to be displayed in a dot matrix because its display position is predetermined. Normally, an icon can be displayed by forming one liquid crystal cell in a specific shape. The liquid crystal cell dedicated to displaying icons is larger than a liquid crystal cell for performing a dot matrix of characters and the like.

In such a liquid crystal display panel, the image quality of the common display is lower than that of the dot matrix display,
Also, the viewing angle tends to be narrowed. As a result of a study by the inventor of the present application, it was found that the driving time of each common line is constant regardless of the size of the liquid crystal cell, so that uniform image quality and uniform viewing angle cannot be obtained in the liquid crystal panel as a whole. It was

An object of the present invention is to provide a technique for obtaining a uniform image quality and a uniform viewing angle regardless of the size of the liquid crystal cell.

The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

[0008]

The outline of the representative one of the inventions disclosed in the present application will be briefly described as follows.

That is, setting means (12, 13) for setting the drive time of an arbitrary row in the liquid crystal display panel.
And a control means (14) for controlling the drive time of the corresponding row based on this setting, thereby forming the liquid crystal drive device.

The first register (12) for setting the icon display row in the liquid crystal display panel, the second register (13) for setting the duty ratio of the icon display row drive waveform, and the second register A liquid crystal drive device is formed including a control circuit (14) for controlling the duty ratio of the drive waveform of the designated row by the first register based on the output value.

Further, an electronic device such as a mobile phone is formed by including the liquid crystal driving device.

[0012]

According to the above means, the control means controls the drive time of the corresponding row based on the setting in the setting means. This ensures a driving time according to the size of the liquid crystal cell, and obtains a uniform image quality and a uniform viewing angle.

The control means controls the duty ratio of the drive waveform of the designated row by the first register based on the output value of the second register. This ensures a driving time according to the size of the liquid crystal cell, and obtains a uniform image quality and a uniform viewing angle.

[0014]

FIG. 2 shows a mobile phone which is an embodiment of the electronic apparatus according to the present invention.

The portable telephone shown in the same figure is connected to a microphone MP and a speaker SPK, a voice codec 50 for converting between a voice signal and an electric signal and between an analog signal and a digital signal, and time division. A channel codec (T for generating and checking codes for processing and error correction, assembling and analyzing transmitted and received frames, etc.
DMA control circuit) 60, modem 70 for modulating and demodulating transmitted / received signals, CPU (central processing unit) 213 for controlling the operation of each unit, keypad 218 including a numeric keypad, and displaying various information Liquid crystal display panel 217 and a liquid crystal drive device 21 for driving the liquid crystal display panel 217.
6 and. Further, although not shown, since it is a mobile phone, it has a built-in battery as a power source for operating each unit.

The audio codec 50 is a low-pass filter (LPF) 51 for removing unnecessary high frequency components from the audio signal from the microphone MP, and an A for converting an output signal of the low-pass filter 51 into a digital signal. A / D conversion circuit 53, a compression circuit 55 for compressing the output signal of the A / D conversion circuit 53 and sending it to the channel codec 60 in the subsequent stage, a decompression circuit 56 for decompressing the digital signal from the channel codec 60, A D / A (digital / analog) conversion circuit 54 for converting the output signal of the decompression circuit 56 into an analog signal.
A low-pass filter (LPF) 52 for removing unnecessary high-frequency components from the output signal of the A / A conversion circuit 54, and an output buffer 57 for driving the speaker SPK based on the output signal of the low-pass filter 52 are included. Consists of

Further, the modem 70 has a modulation waveform generating section 75 for generating a modulation waveform based on the output signal from the channel codec 60, and this modulation waveform generating section 7
D / A conversion circuit 73 for converting the output signal of No. 5 into an analog signal, and low pass filter 7 for removing unnecessary high frequency components from the output signal of this D / A conversion circuit 73.
1. A low-pass filter 72 for removing unnecessary high-frequency components from the output signal of the high-frequency unit 80, an A / D conversion circuit 74 for converting the output signal of the low-pass filter 72 into a digital signal, and this A / D And a demodulation circuit 76 for demodulating the output signal of the D conversion circuit 74.

The modem 70 is coupled with a high frequency section 80 including a power amplifier for transmission, a synthesizer for generating a carrier signal, an adder for synthesizing the carrier signal with a transmission / reception signal, and an antenna 81 for transmission / reception. The transmission and reception of a signal at a radio frequency is possible via the.

FIG. 3 shows the coupling relationship between the liquid crystal driving device 216 and the liquid crystal display panel 217.

As shown in FIG. 3, the liquid crystal display panel 2
Reference numeral 17 denotes common lines COM1 to COM9 and segment lines SEG1 to SEG10 arranged so as to intersect with them.
And liquid crystal cells are arranged at intersections of the common lines COM1 to COM9 and the segment lines SEG1 to SEG10. The liquid crystal cells connected to the common lines COM1 to COM9 are for displaying characters by a dot matrix, and the liquid crystal cells connected to the common line COM9 are for displaying icons. Characters are displayed in a dot matrix, whereas one icon is formed by one icon display liquid crystal cell, and thus the icon display liquid crystal cell has a larger shape than the character display liquid crystal cell.

The segment lines SEG1 to SEG10 and the common lines COM1 to COM9 are driven by the liquid crystal drive device 216 based on display data. At this time, the segment lines SEG1 to SEG10 are simultaneously driven, but the common lines COM1 to COM9 are sequentially driven in a time division manner.

FIG. 4 shows a timing example of time-divisional driving of the common lines COM1 to COM9.

According to the prior art, the driving time is made equal regardless of the character display liquid crystal cell (dot cell) by the dot matrix and the icon display liquid crystal cell, but in this embodiment, uniform image quality is obtained. In order to obtain a uniform viewing angle, the driving time is changed according to the size of the liquid crystal cell. That is, the common lines COM1 to COM8
The selection periods of the liquid crystal cells for character display corresponding to are equal to each other on the common lines COM1 to COM8, but the selection period of the liquid crystal cells for icon display corresponding to the common line COM9 is longer than the selection period of the dot cells. By prolonging the selection period of the icon display liquid crystal cell in this way, a uniform image quality and a uniform viewing angle are obtained for the entire liquid crystal display panel. This is for the following reason.

For example, as shown by waveforms a and b in FIG. 5, when the driving time of the liquid crystal cell for character display by the dot matrix and the liquid crystal cell for icon display are equal to each other, the liquid crystal cell for icon display displays characters. It is not possible to secure the same amount of charge as the charge secured within the lighting (blackening) time of the liquid crystal cell for use, and the image quality and the viewing angle are degraded. Therefore, in FIG. 5, as shown by the waveform c, when the icon selection period is 1.25 times that of the conventional case,
As the icon selection period becomes longer, a large amount of electric charge is secured in the icon display liquid crystal cell.
It is possible to avoid a narrow viewing angle.

By lengthening the selection period of the icon display liquid crystal cell in this way, a sufficient driving time can be obtained in the icon display liquid crystal cell, which is equivalent to the display in the character display liquid crystal cell by the dot matrix. Image quality,
And the viewing angle can be obtained.

FIG. 1 shows a structural example of the liquid crystal driving device 216.

The liquid crystal drive device 216 is not particularly limited.
Is a CPU interface 5 coupled to the CPU 213, a CPU address counter 6, a display address counter 8, a multiplexer 3, a display RAM 7, a character generator 9, a parallel / serial conversion circuit 10, a segment side shift register 22, a segment latch circuit 23,
Segment LCD driver 11, icon row designation register 12, duty ratio designation register 13, common control circuit 14, common counter 15, common side shift register 2
1. The common liquid crystal driver 16 is formed on one semiconductor substrate such as a single crystal silicon substrate by a known semiconductor integrated circuit manufacturing technique.

Various character codes for display are CPU21
3 through the CPU interface 5. At this time, the multiplexer 3 selectively supplies the output address of the CPU address counter 6 to the display RAM 7, so that the character code is written in the display RAM 7. Further, when the output address of the display address counter 8 is selectively supplied to the display RAM 7 by the multiplexer 3 and the information stored in the display RAM 7 is transmitted to the character generator 9, the corresponding font data is transmitted from the character generator 9 in a parallel / parallel manner. It is transmitted to the serial conversion circuit 10. The transmitted font data is converted into serial data by the parallel / serial conversion circuit 10. Then, the liquid crystal display panel 21 is buffered by the segment-side shift register 22 in the subsequent stage.
A data column corresponding to one row of 7 is formed and transmitted to the segment liquid crystal driver 11 via the segment latch circuit 23 in the subsequent stage. Segment LCD driver 1
1 drives the segment line of the liquid crystal display panel 217 based on the data transmitted via the segment latch circuit 23.

The icon row designating register 12 is a register for setting an icon row in the liquid crystal display panel 217, and the duty ratio register 13 is a common for driving the icon row designated by the icon row designating register 12. It is a register for setting the duty ratio of the output waveform. The setting of values in the icon row designation register 12 and the duty ratio designation register 13 is not particularly limited, but is set via the CPU interface 5 via the C interface.
It is designed to be performed by the PU 213. That is, the CPU 213 executes a predetermined program for register setting to set the icon row designation register 12 and the duty ratio designation register 13. This setting is not particularly limited, but is performed immediately after the power of the mobile phone is turned on.

The icon row designation register 12 has a bit configuration capable of designating an icon row. Although not particularly limited, in the present embodiment, the icon row designation register 12 may have a 4-bit configuration in order to be able to designate the icon row from the common lines COM1 to COM9. That is, 4
With the bit configuration, any of the common lines COM1 to COM9 can be designated as the icon row.

Further, the duty ratio designation register 13 is
Although not particularly limited, it has an 8-bit configuration. The 8-bit information “0000” is stored in the duty ratio designation register 13.
When "0000" is set, it is treated as a default in the common control circuit 14, and the selection period of the icon row designated by the icon row designation register 12 is the common corresponding to the liquid crystal cell for character display by the dot matrix. The duty ratio is set to 5/5 by default, although not particularly limited.
On the other hand, depending on the set value of the duty ratio designation register 13, the duty ratio increases by ⅕ unit. For example, in the duty ratio designation register 13, "00000
When "001" is set, the duty ratio of the common output waveform for driving the designated icon row is set to 6/5, and "0000" is set in the duty ratio designation register 13.
When "010" is set, the duty ratio of the common output waveform driving the designated icon row is set to 7/5, and "0000" is set in the duty ratio designation register 13.
When 011 "is set, the duty ratio of the common output waveform for driving the designated icon row is set to 8/5. Thus, according to the value set in the duty ratio designation register 13, The duty ratio of the common output waveform of the icon row can be controlled in 1/5 unit.

The common counter 15 has a common line COM1.
~ Counting operation for time-divisionally driving COM9 is performed.
The common control circuit 14 changes the duty ratio of the common output according to the icon row designation, that is, the duty ratio of the common line drive waveform, based on the output information from the icon row designation register 12 and the duty ratio designation register 13. . For example, as shown in FIG. 3, assuming that the common line COM9 corresponds to an icon row, the driving period of this common line COM9 is the other common lines COM1 to COM1.
The duty ratio of the drive waveform is changed so that it becomes longer than the drive period of COM8. In the subsequent stage of the common counter 15, the common side shift register 21 for buffering the count output, and the common lines COM1 to SO based on the output of the common side shift register 21.
A common liquid crystal driver 16 for driving M9 is provided.

FIG. 6 shows an example of the configuration of the common control circuit 14.

As shown in FIG. 6, the common control circuit 1
Although not particularly limited, 4 includes a coincidence detection circuit 14a and a common clock generation circuit 14b.

The coincidence detection circuit 14a outputs the output value of the icon row designation register 12 and the output value QC of the common counter 15.
When a match between N and N is detected, a match signal AGR is asserted. By asserting the match signal AGR, the drive timing of the icon row is specified.

The common clock generation circuit 14b is not particularly limited, but divides the reference clock CLK0 transmitted from the outside of the liquid crystal drive device 216 and divides the common clock CL.
Generate K. The generated common clock CLK is transmitted to the common counter 15. When the match detection signal AGR is asserted by the match detection circuit 14a, it means the drive timing of the icon row, and therefore the duty ratio of the common clock CLK is changed based on the setting information of the duty ratio designation register 13. To do. When the 8-bit information “00000000” is set in the duty ratio designation register 13, the duty ratio of the designated icon row drive waveform is set to 5/5 (default). In this case, the common clock CLK does not change. However, in the duty ratio designation register 13,
When a value other than the 8-bit information "00000000" is set, the generation of the common clock CLK is stopped in synchronization with the assert timing of the match detection signal AGR. The generation stop period of the common clock CLK is determined by the setting information of the duty ratio designation register 13, and the common clock CLK is generated again after the stop period has elapsed.

FIG. 7 shows the output value Q of the common counter 15.
CN, common clock CLK, and match detection signal AGR
Is shown. In this timing example, the icon line is the 9th line, and the duty ratio designation register 13
Shows the case where "00000111" is set. As described above, since the default duty ratio of the icon row drive waveform is set to 5/5, the designated duty ratio when "00000111" is set in the duty ratio designation register 13 is 12/5, which is a common value. In the clock generation circuit 14b, the generation of the common clock CLK is stopped only during the corresponding period. During this stop period, the output terminal of the common clock generation circuit 14b is in the high level state. The generation stop period of the common clock CLK is determined by counting the reference clock CLK0 according to the information held in the duty ratio designation register 13. When the counting of the reference clock CLK0 is completed according to the information held in the duty ratio designation register 13, the generation of the common clock CLK is started again.

FIGS. 8 to 10 show examples of combinations of icon rows and their driving times.

In the example shown in FIG. 8, the common line COM1
Is an icon row, and its driving time is 5/4 times that of other rows. In the example shown in FIG. 9, the common line COM3
Is an icon row, and its driving time is 11/4 times that of other rows. Depending on the specifications of the liquid crystal display panel 217, a plurality of icon rows may be considered. For example, in the example shown in FIG. 10, the common lines COM1, COM3
Is an icon row, and its driving time is 6/4 times that of other rows. Such icon row designation and drive time setting can be performed by setting the icon row designation register 12 and the duty ratio designation register 13. That is, the icon row and the size of the icon may be different depending on the specifications of the liquid crystal display panel 217 to be driven, but it is easy to do so by setting the icon row designation register 12 and the duty ratio designation register 13. Can correspond to.

According to the above embodiment, the following operational effects can be obtained.

(1) The duty ratio of the drive waveform of the designated row is controlled by the icon row designation register 12 based on the output value of the duty ratio designation register 13, thereby ensuring the driving time according to the size of the liquid crystal cell. Because it is done
A uniform image quality and a uniform viewing angle can be obtained regardless of the size of the liquid crystal cell. That is, even in a large liquid crystal cell, a sufficient driving time can be obtained by controlling the duty ratio, so that an image quality and a viewing angle equivalent to those of a liquid crystal cell for performing dot matrix display of characters and the like can be obtained. .

(2) On the liquid crystal display panel of a mobile phone, in addition to character information such as a telephone number, icons are displayed for visual recognition of the operation. Such a liquid crystal display panel is driven by a liquid crystal. By driving with the device 216, it is possible to obtain the same image quality and viewing angle in the dot matrix display and the icon display.

Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the embodiments and various modifications can be made without departing from the scope of the invention. Yes.

For example, in the above embodiment, the one having the icon row designation register 12 and the duty ratio designation register 13 which can be set by the CPU 213 has been described, but such an icon row designation register 12 and duty ratio designation register 13 are described. Instead of this, a programmable link such as a fuse circuit may be provided, and this programmable link may be used to set the icon row and the duty ratio.

In the above description, the case where the invention made by the present inventor is mainly applied to the mobile phone which is the field of application which is the background of the invention has been described, but the present invention is not limited to this, and home electric appliances and the like. It can be widely applied to various electronic devices.

The present invention can be applied under the condition that at least the liquid crystal display panel is to be driven.

[0047]

The effects obtained by the typical ones of the inventions disclosed in the present application will be briefly described as follows.

That is, based on the setting in the setting means,
Since the drive time of the corresponding row is controlled and the drive time corresponding to the size of the liquid crystal cell is secured, the liquid crystal display panel to be driven has a uniform image quality regardless of the size of the liquid crystal cell. A uniform viewing angle can be obtained.

Further, based on the output value of the second register,
Since the duty ratio of the drive waveform of the designated row is controlled by the first register and the drive time corresponding to the size of the liquid crystal cell is secured, uniform image quality can be obtained regardless of the size of the liquid crystal cell.
And a uniform viewing angle can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of a configuration example of a liquid crystal drive device included in a mobile phone which is an embodiment of an electronic apparatus according to the invention.

FIG. 2 is a block diagram of a configuration example of the mobile phone.

FIG. 3 shows a coupling relationship between a liquid crystal driving device and a liquid crystal display panel included in the mobile phone.

FIG. 4 is a timing diagram showing an example of time-divisional driving of common lines by a liquid crystal driving device included in the mobile phone.

FIG. 5 is a waveform diagram showing the relationship between the drive time of the icon display liquid crystal cell and the lighting of the liquid crystal.

FIG. 6 is a block diagram illustrating a configuration example of a main part of the liquid crystal drive device.

FIG. 7 is an operation timing chart regarding common control in the liquid crystal drive device.

FIG. 8 is a timing chart of an example of a combination of an icon row and its driving time.

FIG. 9 is a timing chart of an example of a combination of an icon row and its driving time.

FIG. 10 is a timing chart of an example of a combination of an icon row and its driving time.

[Explanation of symbols]

5 CPU interface 6 CPU address counter 7 Display RAM 8 Display address counter 9 character generator 10 Parallel / serial conversion circuit 11 segment LCD driver 12 Icon row designation register 13 Duty ratio specification register 14 Common control circuit 14a coincidence detection circuit 14b common clock generation circuit 15 common counter 16 Common LCD driver 21 Common side shift register 22 Segment side shift register 23 segment latch circuit 50 audio codecs 51, 52, 71, 72 Low-pass filter 53,74 A / D conversion circuit 54,73 D / A conversion circuit 55 Compression circuit 56 Decompression circuit 57 output buffer 60 channel codec 70 modem 75 Modulation waveform generator 76 Modulation circuit 80 High frequency part 81 antenna 213 CPU 216 LCD drive device 217 LCD panel 218 keypad

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-11894 (JP, A) JP-A-57-171392 (JP, A) JP-A-55-22733 (JP, A) Actual development Sho-55- 52181 (JP, U) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G02F 1/133 G09G 3/36

Claims (2)

(57) [Claims] 1. A dot matrix display liquid crystal driving device for driving a dot matrix display line, the liquid crystal display panel comprising an icon display line for icon display for, in the liquid crystal display panel A first register for setting the icon display row, a second register for setting the duty ratio of the icon display row drive waveform, and driving of the designated row by the first register based on the output value of the second register. A liquid crystal drive device comprising: a control circuit for controlling a duty ratio of a waveform. A liquid crystal display panel to 2. A column directions formed by arranging a plurality of liquid crystal cells, an electronic apparatus and a driving means for driving the liquid crystal panel, as the drive means, No placement claim 1 Symbol An electronic device comprising a liquid crystal drive device.