JPH06266311A - Display device - Google Patents

Abstract

PURPOSE:To automate the adjustment of a display area so as to facilitate handling by detecting a display start position by using the video signal from a personal computer and controlling the phase of a start pulse generated in a panel control part. CONSTITUTION:The video signal from the personal computer 1 is inputted to the driving circuit 21 in the liquid crystal display device 20 and vertical synchronizing pulses VD and horizontal synchronizing pulses HD are inputted to a PLL part 22 which constitutes a phase control loop. The driving circuit 21 shapes the input video signal into a driving voltage waveform which can display an image on a liquid crystal display panel 23 and supplies the signal to an X driver 25. The PLL part 22 generates a timing signal synchronized with the VD pulses and HD pulses and supplies it to a display start position detector 50. The display start position detector 50 detects an optimum display start position automatically to generate time data, which are supplied to the panel control part 24. The panel control part 24 generates control pulse groups for the X driver 25 and a Y driver 26 and supplies them to the respective drivers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device for displaying image data output by a personal computer (hereinafter referred to as a personal computer) or the like.

[0002]

2. Description of the Related Art In recent years, due to the widespread use of personal computers, there is an increasing demand for display devices that display characters representing the calculation results of personal computers, graphics for drawing, and the like. As a display device,
Most of the so-called laptop type personal computers use a liquid crystal display device, which is an integrated type of personal computer and display device. However, the single unit that is used by connecting to the disc top type personal computer, which is the mainstream of personal computers, is a cathode ray tube (CR
The display device according to T) has advantages in terms of definition and cost, and is more prevalent than liquid crystal display devices.

However, since the liquid crystal system has many advantages such as better convergence and focus performance and smaller depth than the CRT system, the liquid crystal system can be used even in a disk top type personal computer if the definition is improved and the cost is reduced. It is likely to become mainstream.

FIG. 4 shows an example in which a liquid crystal display device is connected to a disc top type personal computer. In FIG. 4, 1
Is a disc top type personal computer (hereinafter simply referred to as a personal computer), and 20 is a liquid crystal display device.

An analog video signal, a vertical synchronizing pulse (VD pulse), and a horizontal synchronizing pulse (HD pulse) are supplied from the personal computer 1 to the liquid crystal display device 20. The video signal is
The VD pulse and the HD pulse introduced into the drive circuit 21 in the liquid crystal display device 20 are input to the PLL unit 22 which constitutes the phase control loop. The drive circuit 21 prepares an input video signal into a drive voltage waveform that can be displayed on the liquid crystal display panel 23 and supplies it to the X driver 25. PLL
The unit 22 generates a timing signal synchronized with the VD pulse and the HD pulse, and supplies this to the panel control unit 24. The panel control unit 24 creates a clock pulse for the X driver 25, a control pulse group based on the start pulse, a clock pulse for the Y driver 26, and a control pulse group based on the start pulse, and gives them to each driver.

The signals for one scanning line sent to the X driver 25 are sent all at once to the scanning lines of the liquid crystal panel 27 designated by the Y driver 26. As a result, the liquid crystal of the liquid crystal cell of the liquid crystal panel 23 is driven, and an image is displayed. The structure of the liquid crystal display panel 23 is shown in more detail in FIG.

The display unit 27 is provided with a signal line electrode group 31 consisting of several hundreds to several thousands lines and a scanning electrode group 32 of about 1,000 lines orthogonal to each other, and active points such as thin film transistors (TFTs) are provided at respective intersections. An element is provided, and a liquid crystal is driven by applying an electric potential corresponding to the luminance level to display an image. The X driver 25 includes a shift register 33 having stages corresponding to the number of pixels of the horizontal scanning line.
And a sample hold unit 34 that samples the input video signal (driving voltage) by the output of each stage of the shift register 33. When the start pulse and the clock pulse are given to the shift register 33, the shift 33 shifts the start pulse to each stage. The pulse during the shift is sequentially given to the sample hold unit 34. As a result, the input / output video signal is sampled and held in the sample hold unit 34 one after another. When the video signal for one scanning line is held by the sample hold unit 34, the scanning line is designated by the Y driver 26 (actually a shift register). Then, the samples of the sample hold unit 34 are simultaneously given to the respective elements of the scanning line through the signal electrodes, and the liquid crystal cells are driven. A vertical period start pulse is also applied to the Y driver 26, and this start pulse is shifted by a horizontal period clock and output as a scan line designating pulse. FIG. 5 shows the operation timing of the liquid crystal display panel.

FIG. 5 (A) (Aa) shows X in the horizontal period.
It is a video signal on the driver 25 side, and (Ab) is H
D pulse, (Ac) is a clock, and (Ad) is a start pulse. Further, (Ae) is a video signal on the Y driver 26 side in the vertical cycle, (Af) is a VD pulse, (Ag) is an HD pulse, and (Ah) is a start pulse. In the figure, the time when the start pulse rises is the display start position on the display panel.

[0009]

The start pulse described above is an important factor in determining the display start position of the display panel. In general, when the display device displays a general television image signal such as NTSC, the end of the screen is not visible in consideration of the variation of the display range of each display device caused by the influence of temperature change. The display area is set as shown in (Ba) of B). That is, the setting is called overscan, and the image information at the screen edge is discarded and the actual display area is displayed smaller than the original image area. However, a display signal from a personal computer is often a character, and when displaying an image on a display device, it is necessary to avoid a situation in which the character is missing and unreadable, unlike ordinary television broadcasting. Therefore, in a display device using a cathode ray tube (CRT), unlike a normal television image, a display called underscan is performed as shown in (Bb) of FIG. 5B. That is, the entire original video area is displayed smaller than the display area of the display device. However, in a liquid crystal display device, since pixels are wasted, a display called just scan is often performed as shown in (Bc) of FIG. 5B. For this reason, there is a problem in that there is no margin in the display area and the screen is likely to be chipped due to variations in equipment, temperature changes, and the like. In order to cope with this, the user manually changes the timing of the start pulse to adjust the screen display area of the liquid crystal display device.

Therefore, an object of the present invention is to provide a display device in which the display area is automatically adjusted when the display data of a personal computer is displayed on a liquid crystal display panel and the handling is easy.

[0011]

According to the present invention, there is provided a display start position detecting circuit for detecting a display start position by using a video signal from a personal computer and controlling a phase of a start pulse created by a panel control section. It is provided.

[0012]

By the above means, the optimum display start position can be obtained without performing manual operation, and the reliability of the product can be improved.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1A shows an embodiment of the present invention.
FIG. 1B is a timing chart shown for explaining the operation of the apparatus. Reference numeral 1 is a disk top type personal computer (hereinafter simply referred to as a personal computer), and 20 is a liquid crystal display device.

An analog video signal, a vertical synchronizing pulse (VD pulse), and a horizontal synchronizing pulse (HD pulse) are supplied from the personal computer 1 to the liquid crystal display device 20. The video signal is
The VD pulse and the HD pulse introduced into the drive circuit 21 in the liquid crystal display device 20 are input to the PLL unit 22 which constitutes the phase control loop. The drive circuit 21 prepares an input video signal into a drive voltage waveform that can be displayed on the liquid crystal display panel 23 and supplies it to the X driver 25. PLL
The unit 22 generates a timing signal synchronized with the VD pulse and the HD pulse, and supplies this to the display start position detector 50. The above-mentioned video signal is also introduced to the display start position detector 50.

As will be described later, the display start position detector 50 automatically detects the optimum display start position, creates time data, and supplies this to the panel control unit 24. The panel control unit 24 uses a clock pulse for the X driver 25,
A control pulse group based on the start pulse, a clock pulse for the Y driver 26, and a control pulse group based on the start pulse are created and given to each driver.

The signals for one scanning line sent to the X driver 25 are sent all at once to the scanning lines of the liquid crystal panel 27 designated by the Y driver 26. As a result, the liquid crystal of the liquid crystal cell of the liquid crystal panel 23 is driven, and an image is displayed.

The apparatus of this embodiment is constructed as described above. The difference from the device described in the conventional example is that the display start position detector 50 is provided, and this will be described in more detail. That is, the display start position detector 50 has a time t1 as shown in (B1) of FIG.
(That is, the time at which the luminance level of the input video signal becomes equal to or higher than the black level (0) for the first time from the rise of the HD pulse is measured and stored. Then, this time data is given to the panel control section 24. , The time tst until the start pulse (start pulse given to the X driver 25 in this example) rises is set based on the time data. In the example of the figure, until the luminance signal rises based on the HD pulse. The start timing for the start pulse for the X driver 25 is set by measuring the time t1 of the above. However, if a pulse having a timing based on the VD pulse is created in the same way, the start pulse for the Y driver 26 can be obtained. You can

Now, the timing of the start pulse is set as shown in (B1) of FIG. 1 (B), and the detection as shown in (B2) is made during a certain scanning period, and the detected time is longer than the stored time t1. It is assumed that a long time t2 has been detected. In this case, new time data is not stored, and the time data up to this point is used to execute at the timing of the start pulse. However, if the detection is as shown in (B3) and a time t3 shorter than the time t1 stored so far is detected,
The newly measured time data is stored again and this time data is given to the panel control unit 24. By this, (B
As in 3), the rise of the start pulse is corrected at an early time.

That is, the display start position detector 50 measures and stores the shortest time until the video signal becomes equal to or higher than the black level in each scanning period, and sets the display start position according to this time. . 2A shows a specific configuration example of the display start position detector 50, and FIG. 2B shows a timing chart for explaining the operation example.

The comparator 51 receives an input video signal (B input: FIG. 2).
(B)) is compared with the black level “0” (A input), and when the input video signal is equal to or higher than the black level (A <B), the high-level signal S1 is output. The counter 52 is cleared by the HD pulse given from the PLL unit 22,
The clock (FIG. 2B) input from the L unit 22 is counted. Then, when the previous signal S1 becomes high level,
The counting operation is stopped.

That is, the time from the HD pulse until the brightness level becomes 0 or more is measured. Counter 5
The n-bit output data of 2 (m in the illustrated example) is supplied to the A input of the comparator 53 and the memory 54. Comparator 53
The data stored in the memory 54 is fed back to the B input of ((m-1) in the example of FIG. 2B). The comparator 53 outputs a high-level output signal S2 when A <B, that is, when the measured time is shorter than the time stored so far. In the example shown in the figure, m <(m
Since it is −1), the signal S2 becomes high level at this time. Then, the memory 54 stores the counter 5 at this time.
2 output data (m) will be stored. Signal S2
When is not high level, the existing data will be maintained.

In rare cases, a video signal input from a personal computer may display a video that is offset to the right or to the bottom. In such a case, the system described above attempts to set the display start position to a position that is significantly delayed, but by appropriately selecting the set period of the start pulse described above, it is possible to always obtain an appropriate display state. it can. For example, as shown in FIG. 3 (A), the output video signal of the personal computer is "MEMORY TEST OK" to the left when the power is turned on.
Since a character such as "B" is often displayed, a proper display area can be set by performing the start pulse setting operation at this time.

The present invention is not limited to the above embodiment. In the above-mentioned embodiment, the display area is set by using the video data normally obtained from the personal computer. However, the present invention is not limited to this, and the reference image data for automatically setting the display area may be positively output from the personal computer. FIG. 3B shows an example thereof. A central processing unit (CPU) 3 is provided inside the disk top type personal computer 1, and digital data for video is output from the CPU 3 and temporarily stored in a video memory (hereinafter referred to as VRAM) 4. When a certain amount of data is accumulated in VRAM4,
Control signal group from the control unit 5 (vertical synchronization (VD) pulse,
Horizontal sync (HD) pulse, clock, address, etc. is V
The data is supplied to the RAM 4, and thereby, the data inside the VRAM 4 is constructed and read out as video data (having data such as a blanking signal before and after the picture data). This video data is input to the digital-analog (D / A) converter 6 and output as an analog video signal.

Here, the personal computer 1 has a hard disk,
Alternatively, the floppy disk 8 is loaded, but the reference signal is recorded on this recording medium. And
When the power is turned on or the user operates, the reference signal is C
It is output as a video signal through the PU 3, VRAM 4, and D / A converter 6 and input to the liquid crystal display device 20. The liquid crystal display device 20 has exactly the same configuration as the previous embodiment. Various types of reference signals can be used. For example, as shown in FIG. 3 (C), a signal for displaying a horizontal line on the display surface and a vertical line on the left end may be used. Then, the reference signal output period may be determined, and the start pulse timing setting operation described above may be performed only during this period. Further, as the signal for level detection described above,
You may use the color signal of a specific period.

[0026]

As described above, according to the present invention,
When the display data of the personal computer is displayed on the liquid crystal display panel, the adjustment of the display area can be automated and the handling can be facilitated.

[Brief description of drawings]

FIG. 1 is a configuration diagram and a waveform diagram showing an embodiment of the present invention and an operation example thereof.

2A and 2B are a configuration diagram and a waveform diagram showing a specific example of the display start position detector of FIG. 1 and an operation example thereof.

FIG. 3 is a diagram showing a display screen according to an operation example of the apparatus of the present invention and another embodiment of the present invention.

FIG. 4 is a configuration diagram showing a conventional personal computer, a liquid crystal display device, and a display panel unit.

5A and 5B are signal waveform diagrams and display examples shown for explaining the operation of the apparatus of FIG.

[Explanation of symbols]

1 ... Personal computer, 20 ... Liquid crystal display device, 21 ... Drive circuit,
22 ... PLL section, 23 ... Liquid crystal display panel, 24 ... Panel control section, 25 ... X driver, 26 ... Y driver, 27 ...
Display unit, 50 ... Display start position detector.

Claims (3)

[Claims] 1. A drive circuit to which an input video signal is supplied, and a phase to which a vertical synchronizing pulse and a horizontal synchronizing pulse of the input video signal are supplied to generate an internal vertical synchronizing pulse, an internal horizontal synchronizing pulse and a clock for internal synchronization. A synchronous loop circuit section, an X driver for sampling a video signal digitized by the driving circuit by the clock to a sample hold circuit, and one scanning line of the output of the X driver are supplied to the signal electrodes all at once, and Y In a display device including a display unit in which pixels at intersections of the scan electrodes and the signal electrodes designated by an output designation pulse of a driver are driven, the at least the internal horizontal synchronization pulse and the input video signal are input, The time after the synchronization pulse until the brightness level of the input video signal reaches a predetermined level is detected, and The display start position detecting means for obtaining the time data and the timing setting means for inputting the time data and determining the output timing of the start pulse for starting the signal acquisition of the X driver based on the time data value. A display device characterized by the above. 2. The display position detecting means includes means for detecting the time until the luminance level of the input video signal reaches a predetermined level after the input of the internal vertical synchronizing pulse, and obtaining the time data. 2. The display according to claim 1, wherein the timing setting means includes means for outputting a second start pulse that determines an output start timing of the output designating pulse of the Y driver based on the second time data. apparatus. 3. The display device according to claim 1, wherein the input video signal is a reference signal generated from a recording medium loaded in a personal computer.