JP2000163022A - Color liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To automatically switch driving between three-phase driving corresponding to a sequential sampling system and single-phase driving corresponding to a simultaneous sampling system adaptively to the kind of an input video signal by providing a discriminating circuit which outputs a three-phase driving request or single-phase driving request, a sampling clock switching circuit, etc. SOLUTION: The sampling clock switching circuit 12 has its switching operation controlled with the output of the discriminating circuit 13 which discriminates the kind of the input video signal. The discriminating circuit 13 discriminates whether the video signal is a video signal matching the sequential sampling system or a video signal matching the simultaneous sampling system and outputs the three-phase driving request or single-phase driving request. The sampling clock switching circuit 12 supplies a driver with a three- phase sampling lock to a driver 3 individually corresponding to video signals of the primary colors of R, G, and B at the three-phase driving request and supplies the driver with the sampling clock of a 1st phase of the three-phase sampling clock corresponding to the video signals of the primary colors in common.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color system in which three-phase driving corresponding to a sequential sampling system and single-phase driving corresponding to a simultaneous sampling system can be automatically switched and selected according to the type of an input video signal. The present invention relates to a liquid crystal display device.

[0002]

2. Description of the Related Art A conventional color liquid crystal display device 1 shown in FIG.
A liquid crystal panel 2 in which R (red), G (green), and B (blue) pixels corresponding to the three primary colors are arranged in a matrix;
It is composed of a driver 3 which samples the B video signals at a predetermined timing and supplies them to the liquid crystal panel 2, and a controller 4 which controls the driver 3. The driver 3 sequentially samples and holds RGB input video signals in accordance with a sampling clock generated by the controller 4 and supplies a hold output to the liquid crystal panel 2. The controller 4 includes a PLL (phase locked loop) circuit 41 for generating a basic clock CL, and a three-phase clock generating circuit for generating three-phase sampling clocks CL1, CL2, and CL3 from the first to third phases from the basic clock CL. 42. The PLL circuit 41 has a well-known circuit configuration in which a phase comparator 411, a low-pass filter circuit 412, a VCO (voltage controlled oscillator) 413, and a frequency divider 414 are connected in a loop. By the correction, a stable basic clock CL can be generated.

[0003] The frequency of the basic clock CL is determined according to the number of pixels of the liquid crystal panel 2 and the horizontal scanning cycle. In this example, the liquid crystal panel 2 having 320 pixels arranged in each of RGB colors is used. A video signal of 15.734 kHz is displayed. Therefore, PLL
The phase comparator 411 in the circuit 41 has a frequency of 15.734 kHz.
Is compared with the output of the VCO 413, that is, the signal obtained by dividing the basic clock CL by 1220 by the frequency divider 414. The phase comparison error obtained by the phase comparator 411 is converted into a DC voltage by the low-pass filter circuit 412 and then applied to the VCO 413. The VCO 413 oscillates at a frequency corresponding to the applied voltage. Thus, the oscillation frequency of the VCO 413 is corrected in a direction in which the phase comparison error converges to zero, and a stable 19.2 MHz basic clock CL by a closed loop is generated.

The three-phase clock generation circuit 42 has a 19.2M
Frequency divider 42 divides the base clock CL of 3 Hz to 6.4 MHz and generates a first phase sampling clock CL1.
1, a phase delay unit 422 for delaying the phase of the first phase sampling clock CL1 by 120 degrees to generate a second phase sampling clock CL2, and a first phase sampling clock C1.
And a delay unit 423 for generating a third phase sampling clock CL3 by delaying L1 by 240 degrees.
Phase to third phase sampling clocks CL1,
CL2 and CL3 are supplied to the driver 3.

The driver 3 is provided with a counter 31 and a sample-and-hold circuit 32 corresponding to video signals of each color of RGB. Each counter 31 has an output terminal for the number of pixels. Each counter 31 has a sampling pulse SHP having a pulse width of one clock from the rising edge of each sampling clock CL1, CL2, CL3.
n is supplied from one output terminal. That is, the sampling pulses SHP1 and SHP for sampling the R signal are output from the first phase sampling clock CL1.
4,... SHP 318 are generated. Also, from the second phase sampling clock CL2, sampling pulses SHP2, SHP5 for sampling the G signal.
.. SHP319 are generated, and sampling pulses SHP3, SHP6,... SHP for sampling the B signal are generated from the third phase sampling clock CL3.
320 is generated.

The sample-and-hold circuit 32 includes an analog switch 3 that is closed by a sampling pulse SHPn.
21, a capacitor 322 for holding the voltage level of the input video signal when the analog switch 321 is closed, and an operational amplifier 323 as an output buffer for applying the terminal voltage of the capacitor 322 to the liquid crystal panel 2. The sample and hold circuits 32 exist for the number of horizontal pixels of the liquid crystal panel 2 (960 in this case), and the phases of the three-phase sampling clocks CL1, CL2, and CL3 are 12
Since it is shifted by 0 degrees, the sampling of the video signals of each color of RGB is sequentially performed with a certain time difference. That is, in the case of this example, the RGB video signals sequentially sampled by the three-phase driving are displayed on the liquid crystal panel 2.

[0007]

In the above-mentioned conventional color liquid crystal display device 1, the sampling method of the video signal of each color of RGB is fixed to the sequential sampling method, and cannot be changed to a sampling method other than the sequential sampling method. It has been. In general, a sequential sampling method of sampling a video signal of each color of RGB with a time difference and sampling in order is suitable for displaying a moving image because of good mixing of colors, and is often used for reproducing a television signal. However, in the case where a signal close to a still image signal including character information and the like, for example, a navigation signal for superimposing and displaying character information on map information is displayed on the liquid crystal panel 2, color blur occurs on a vertical line in the sequential sampling method. There's a problem. Such a problem can be solved by adopting a simultaneous sampling method in which sampling of video signals of RGB colors is simultaneously performed without providing a time difference, but the sampling method of the conventional color liquid crystal display device 1 is fixed to a sequential sampling method. Therefore, there is a problem that a video including character information or the like cannot be clearly displayed.

The present invention has solved the above-mentioned problem, and automatically selects and switches between three-phase driving corresponding to the sequential sampling method and single-phase driving corresponding to the simultaneous sampling method according to the type of the input video signal. It is intended to be able to do so.

[0009]

In order to achieve the above object, the present invention provides a liquid crystal panel for displaying a color image and a video signal which is separated into three colors according to an externally supplied sampling clock. Hold and
A driver for supplying and driving the color liquid crystal panel;
A three-phase clock generating circuit for generating a three-phase sampling clock, and identifying whether the video signal is a video signal conforming to a sequential sampling scheme or a video signal conforming to a simultaneous sampling scheme, and performing three-phase driving in accordance with the identification result. An identification circuit that outputs a request or a single-phase drive request, and is provided between the three-phase clock generation circuit and the driver, and operates in response to each of the requests; Are supplied to the driver in such a manner as to individually correspond to the three-color video signals, and when a single-phase drive request is made, a specific single-phase sampling clock among the three-phase sampling clocks is commonly associated with the three-color video signals. And a sampling clock switching circuit for supplying the sampling clock to the driver.

The sampling clock switching circuit includes three clock supply lines for respectively supplying three-phase sampling clocks of a first phase, a second phase, and a third phase;
A switching contact provided on the first-phase clock supply line, a switching contact provided on each of the second-phase and third-phase clock supply lines, and a common contact provided on each of the second-phase and third-phase clock supply lines; In response to the request, a pair of two-phase and three-phase sampling clocks are supplied to the driver at the time of a three-phase drive request, and the first phase sampling clock is supplied to the driver at the time of a single-phase drive request. And a changeover switch.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a block diagram showing an embodiment of a color liquid crystal display device according to the present invention.
FIG. 3 is a signal waveform diagram of each section of the circuit shown in FIG. 1 when a television signal is input, and FIG.
3 is a signal waveform diagram of each section of the circuit shown in FIG.

In the color liquid crystal display device 11 shown in FIG. 1, a sampling clock switching circuit 12 is provided between the controller 4 and the driver 3, and the sampling clock switching circuit 12 is connected to an identification circuit 13 for identifying the type of an input video signal. The switching is controlled by the output. The identification circuit 13 identifies whether the video signal is a video signal conforming to the sequential sampling scheme or a video signal conforming to the simultaneous sampling scheme, and outputs a three-phase drive request or a single-phase drive request. The sampling clock switching circuit 12 supplies the three-phase sampling clock to the driver 3 in a manner corresponding to each of the RGB three-color video signals when the three-phase driving is requested, and supplies the first phase of the three-phase sampling clock when the single-phase driving is requested. The sampling clock is supplied to the driver 3 in common with the video signals of the three colors.

The sampling clock switching circuit 12 shown in the present embodiment includes three clock supply lines 121 for respectively supplying three-phase sampling clocks CL1, CL2 and CL3 of a first phase, a second phase and a third phase. , 122,12
3, each of the second and third phase clock supply lines 12
2 and 123 are provided with changeover switches S2 and S3, respectively. One changeover switch S2 is
Switching contacts S2a and S2b provided on the first-phase clock supply line 121 and the second-phase clock supply line 122;
Common contact S2 provided on second phase clock supply line 122
and supplies a second-phase sampling clock CL2 to the driver 3 when a three-phase drive is requested, and supplies a first-phase sampling clock CL1 to the driver 3 when a single-phase drive is requested. The other changeover switch S3 is provided with a changeover contact S3 provided on the first phase clock supply line 121 and the third phase clock supply line 123.
a, S3b and a common contact S3c provided on the third-phase clock supply line 123. The three-phase sampling clock CL3 is supplied to the driver 3 when a three-phase drive is required, and the first phase sampling clock CL3 is supplied when a single-phase drive is required. It functions to supply the phase sampling clock CL1 to the driver 3.

Here, when displaying a television signal, an identification signal 13 supplied from the outside with an identification signal indicating that the input video signal is a television signal, a three-phase drive request and a sampling clock switching circuit 12 To the changeover switches S2 and S3. As a result, one of the changeover switches S2 takes a state of connecting the changeover contact S2b and the common contact S2c in the second phase clock supply line 122, and the second phase sampling clock CL2.
2 is supplied to the driver 3. The other changeover switch S3 connects the changeover contact S3b and the common contact S3c in the third-phase clock supply line 123 to connect the third-phase sampling clock CL3 to the driver 3.
To supply. As a result, the driver 3 includes in FIG.
As shown in (C), three-phase sampling clocks CL1, CL2 and CL3 of the first to third phases are sequentially supplied. Three-phase sampling clocks CL1, CL2,
The driver 3 receiving the supply of CL3 is shown in FIG.
As shown in (L), each counter 31 outputs three-phase sampling pulses SHP1 and SHP1 for video signals of each color of RGB.
SHP4 ... and SHP2, SHP5 ... and SHP
3, the SHP 6 can be generated, and the RGB video signals held by the sample and hold circuit 32 can be supplied to the liquid crystal panel 2.

On the other hand, when displaying a navigation signal, an identification signal indicating that the input video signal is a navigation signal is transmitted from an externally supplied identification bribery 13.
Supplies a single-phase drive request to the changeover switches S2 and S3 in the sampling clock switching circuit 12.
As a result, the one changeover switch S2 is in a state of connecting the changeover contact S2a in the first phase clock supply line 121 and the common contact S2c in the second phase clock supply line 122, as shown in FIG. As shown in (1), the first-phase sampling clock CL1 is supplied to the driver 3.
The other switch S3 also connects the switching contact S3a in the first phase clock supply line 121 and the common contact S3c in the third phase clock supply line 123, as shown in FIG. 3C. As shown, the first-phase sampling clock CL1 is supplied to the driver 3. As a result, the driver 3 supplies the first phase sampling clock C
Only L1 is supplied. As a result, the driver 3 that has received the supply of the first-phase single-phase sampling clock CL1 sets the counters 31 to R, as shown in FIGS.
In-phase sampling pulses SHP1, SHP2, and SHP3 are generated for video signals of each color of GB, and then in-phase sampling pulses SHP4, SHP5, and SHP6 are generated. Hereinafter, in-phase sampling pulses are similarly generated, and finally, in-phase sampling pulses SHP3
18, SHP 319 and SHP 320 are generated. Thus, the navigation video signals of each of the RGB colors held by the sample and hold circuit 32 are supplied to the liquid crystal panel 2.

As described above, the color liquid crystal display device 11
According to the method, when displaying a television signal, by performing three-phase driving with a three-phase sampling clock, a time difference is provided between the sampling of the video signals of each color of RGB and sequential sampling is performed in order, thereby displaying a moving image with good color mixture. On the other hand, when displaying a signal close to a still image signal including character information, for example, a navigation signal for superimposing character information on map information is displayed, a single-phase driving by a single-phase sampling clock is used to display each of RGB colors. The simultaneous sampling is performed simultaneously without any time difference in the sampling of the video signal, and the video including character information can be displayed clearly without causing color blur etc. on the white vertical line, and the input video signal can be displayed. Good liquid crystal display is possible by automatically selecting three-phase drive or single-phase drive according to the type.

The sampling clock switching circuit 12 has a configuration in which only a pair of switches S2 and S3 are provided on each of the second and third phase clock supply lines.
It can be freely adapted to both phase drive and single phase drive,
Both television signals and navigation signals can be displayed with high quality with good color reproducibility.

[0018]

As described above, according to the present invention,
An identification circuit for identifying whether the video signal is a video signal conforming to the sequential sampling method or a video signal conforming to the simultaneous sampling method outputs a three-phase drive request or a single-phase drive request according to the identification result, and generates a three-phase clock. A sampling clock switching circuit disposed between the circuit and the driver operates in response to each of the requests, and at the time of a three-phase drive request, the three-phase sampling clock is individually associated with each of the three color video signals. When a single-phase drive request is made, a specific single-phase sampling clock among the three-phase sampling clocks is supplied to the driver in common with the three-color video signal. In the case of displaying, a time difference is provided between the sampling of the video signals of each color of RGB by the three-phase driving by the three-phase sampling clock. Performed sequentially sampled sampled turn, you can make color mixing good movie display, while also signal close to a still image signal including text information or the like,
For example, when displaying a navigation signal that superimposes text information on map information, a single-phase drive by a single-phase sampling clock performs simultaneous sampling in which sampling of video signals of each color of RGB is simultaneously performed without a time difference, and white The image including character information can be clearly displayed without causing color blur etc. on the vertical line, and the three-phase drive and the single-phase drive are automatically selected according to the type of the input video signal. An excellent effect such as a liquid crystal display is provided.

The sampling clock switching circuit includes three clock supply lines for respectively supplying three-phase sampling clocks of a first phase, a second phase, and a third phase;
Switching contacts provided on the phase clock supply line, the second phase and the third phase clock supply lines, and the second and third phase clock supply lines.
A common contact provided on each phase clock supply line is provided and switched in response to each request, and when a three-phase drive request is made, a second-phase and a third-phase sampling clock is supplied to the driver, and a single-phase drive is provided. When a request is made, a pair of changeover switches for supplying the first phase sampling clock to the driver are provided, so that only a pair of changeover switches is provided on each of the second and third phase clock supply lines, so that the three phase The present invention can be freely adapted to both driving and single-phase driving, and has excellent effects such as high-quality display of both television signals and navigation signals with good color reproducibility.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a color liquid crystal display device according to the present invention.

FIG. 2 is a signal waveform diagram of each section of the circuit shown in FIG. 1 when a television signal is input.

FIG. 3 is a signal waveform diagram of each section of the circuit shown in FIG. 1 when a navigation signal is input.

FIG. 4 is a block diagram showing an example of a conventional color liquid crystal display device.

[Explanation of symbols]

 Reference Signs List 2 liquid crystal panel 3 driver 4 controller 11 color liquid crystal display device 12 sampling clock switching circuit 121, 122, 123 clock supply line 13 identification circuit 41 PLL circuit 42 three-phase clock generation circuit S2, S3 switch S2a, S2b, S3a, S3b switch Contact S2c, S3c Common contact

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H093 NA22 NA64 NC16 NC23 ND12 ND24 ND34 ND60 5C006 AA01 AA02 AA22 AF23 AF51 AF53 AF61 AF85 BB11 BC16 BF07 BF14 BF21 BF22 BF23 BF31 FA04 FA06 FA07 FA21 FA56 5C080 A03 DD03 EE30 FF09 GG08 JJ02 JJ04 KK23

Claims (2)

[Claims] 1. A liquid crystal panel for displaying a color image and a video signal separated into three colors according to a sampling clock given from the outside, are sampled and held, respectively.
A driver for supplying and driving the color liquid crystal panel;
A three-phase clock generating circuit for generating a three-phase sampling clock, and identifying whether the video signal is a video signal conforming to a sequential sampling scheme or a video signal conforming to a simultaneous sampling scheme, and performing three-phase driving in accordance with the identification result. An identification circuit that outputs a request or a single-phase drive request, and is provided between the three-phase clock generation circuit and the driver, and operates in response to each of the requests; Are supplied to the driver in such a manner as to individually correspond to the three-color video signals, and when a single-phase drive request is made, a specific single-phase sampling clock among the three-phase sampling clocks is commonly associated with the three-color video signals. A color liquid crystal display device comprising: a sampling clock switching circuit for supplying the sampling clock to the driver. 2. A sampling clock switching circuit comprising: three clock supply lines for respectively supplying three-phase sampling clocks of a first phase, a second phase, and a third phase;
Switching contacts provided on the phase clock supply line, the second phase and the third phase clock supply lines, and the second and third phase clock supply lines.
A common contact provided on each phase clock supply line is provided and switched in response to each request, and when a three-phase drive request is made, a second-phase and a third-phase sampling clock is supplied to the driver, and a single-phase drive is provided. 2. The color liquid crystal display device according to claim 1, further comprising a pair of changeover switches for supplying said first phase sampling clock to said driver when required.