JP3436212B2 - Liquid crystal display - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a first display mode in which a received image having the same resolution as that of a liquid crystal display panel is displayed on the liquid crystal panel at the same size, and a received image having a lower resolution than that of the liquid crystal display panel is displayed on the liquid crystal display panel. Selecting means for selecting a second display mode for enlarged display on the screen, and an external clamp signal and an internal clamp for specifying a clamp period for a clamp circuit for clamping a black level of an analog video signal input from the outside. The present invention relates to a liquid crystal display device including a selecting unit that selects one of the signals as an output to the clamp circuit.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram showing an example of a circuit configuration of a conventional liquid crystal display device. In the conventional technique, the selectors 207 and 208 are configured to display the same-size display control signal generation circuit 2 according to the CNTSEL signal input from the outside.
04 or the enlarged display control signal generation circuit 205 selects the output of the control signal, and the selector 211 is input from the internal clamp signal generation circuit 210 according to the CPSEL signal input from the outside. One of the internal clamp signal and the external clamp signal input from the outside is selected as the output signal to the clamp circuit 208.

[0003]

As described above, in the above-mentioned prior art, while the simplification of the interface of the liquid crystal display device is being promoted, either one of the two display modes is selected or the external clamp is used. In order to select either the signal or the internal clamp signal as the input of the clamp circuit, a select signal (CN
It was necessary to input the TSEL signal and the CPSEL signal).

However, since it is necessary to input the selector signal from the outside, it is necessary to change the circuit on the signal source side such as a personal computer, and the interface between the signal source and the liquid crystal display device becomes complicated. There was a problem.

The present invention has been made in view of the above-mentioned problems. The first display mode in which a received image having the same resolution as that of the liquid crystal display panel is displayed on the liquid crystal display panel at the same size, and the liquid crystal display panel is used. A liquid crystal display that does not require input of a select signal (CNTSEL signal) from the outside when selecting one of the second display modes in which a received image having a low resolution is enlarged and displayed as a display mode on the liquid crystal display panel. The purpose is to provide a device.

Further, according to the present invention, for a clamp circuit that clamps a black level of an analog video signal input from the outside, one of an external clamp signal and an internal clamp signal that specifies a clamp period is sent to the clamp circuit. When selecting as output, select signal from outside (CP
It is an object of the present invention to provide a liquid crystal display device that does not require the input of SEL signals).

[0007]

In order to achieve such an object, the present invention has the following features. According to the first aspect of the present invention, the first display mode in which the received image having the same resolution as that of the liquid crystal display panel is displayed on the liquid crystal display panel at the same size, and the received image having a lower resolution than that of the liquid crystal display panel is serially strobed from the outside. Display mode selection for selecting one of the second display modes of the enlarged display on the liquid crystal display panel by determining the enlargement ratio according to the input signal including the signal as the display mode on the liquid crystal display panel
Means and the black level of the analog video signal received from the outside.
Clamping means for clamping the
The black level of the analog video signal at a fixed timing.
Internal clamp signal to specify that to clamp
Internal clamp signal generating means for generating
Timing and clamping for signal and clamping means
External clamp signal for externally specifying the ring
Select one of these signals as the output signal to the clamping means.
Liquid crystal display device having clamp signal selecting means for selecting
At this time, the change of the level of the serial strobe signal input from the outside is detected, and the display mode is based on the detection result.
Serial strobe signal detection means for outputting a selection signal to the mode selection means , and an external clamp signal input from the outside
Level change is detected, and the class is detected based on the detection result.
External clamp signal that outputs a selection signal to the pump signal selection means
And a display mode selecting means based on the selection signal input from the serial strobe signal detecting means, the display mode being one of the first display mode and the second display mode. Is selected as the display mode on the liquid crystal display panel and the clamp signal is selected.
The means is a selection input from the external clamp signal detection means.
An internal clamp signal and an external clamp signal based on the signal.
Output signal to the clamp means.
It is characterized in that it is selected as an issue .

According to a second aspect of the present invention, in the liquid crystal display device according to the first aspect, the serial strobe signal detecting means sets the second display mode to the display mode on the liquid crystal display panel when the serial strobe signal is detected. Is output to the display mode selection means .

According to a third aspect of the present invention, in the liquid crystal display device according to the first or second aspect, the serial strobe signal detecting means sets the first display mode when the serial strobe signal is not detected for a predetermined period. Select the display mode selection signal for the display mode on the liquid crystal display panel.
It is characterized by outputting to the means .

[0010] The invention of claim 4, wherein, in the liquid crystal display device according to claim 1, wherein the external clamping signal detecting means, when detecting a change in the level of the external clamp signal, the output of the external clamping signal to the clamping means A selection signal to be a signal is output to the clamp signal selection means .

According to a fifth aspect of the present invention, in the liquid crystal display device according to the first or second aspect , when the external clamp signal detecting means does not detect a change in the level of the external clamp signal for a predetermined period, the internal clamp signal is detected. The present invention is characterized in that a selection signal that outputs the signal to the clamp means is output to the clamp signal selection means .

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an example of a circuit configuration of a liquid crystal display device according to an embodiment of the present invention. The liquid crystal display device shown here receives, for example, a vertical synchronizing signal, a horizontal synchronizing signal, a dot clock signal, and a video signal output from a personal computer, and displays a video on the liquid crystal display panel based on these signals.

In FIG. 1, reference numeral 101 denotes an active matrix type liquid crystal display panel in which a 3-terminal switching element is added to each pixel, which is a 3-terminal switching element T.
A gate driver 102 and a source driver 103 are connected to the gate electrode and the source electrode of the FT, respectively.

Reference numeral 104 denotes a gate driver 1 for displaying at the same size.
02 and the source driver 103 is a unity-scale display control signal generation circuit for generating a control signal. A predetermined control signal is output for displaying at the same size. Reference numeral 105 denotes an enlarged display control signal generation circuit that generates control signals for the gate driver 102 and the source driver 103 during enlarged display. These circuits are circuits that generate control signals to the gate driver 102 and the source driver 103 at timings corresponding to the enlargement ratio instructed by the externally input serial data signal, serial clock signal, and serial strobe signal. .

The serial data signal, the serial clock signal, and the serial strobe signal are so-called three-wire serial communication means. After the data transfer is completed, the serial strobe signal is from high level to low level or from low level to high level. Changes to.

The control signal to the gate driver 102 generated by the equal-magnification display control signal generation circuit 104 and the magnified display control signal generation circuit 105 is input to the gate driver 102 through the selector 106, and the source driver 103.
The control signal to the source driver 103 is input to the source driver 103 via the selector 107. The selectors 106 and 107 select outputs according to the select signal from the serial strobe signal detection circuit 112.

Reference numeral 108 denotes a clamp circuit, which is a clamp circuit for raising the black level of the received analog video signal to a predetermined DC voltage level. Reference numeral 110 denotes an internal clamp signal generation circuit that generates an internal clamp signal that specifies a clamp period to the clamp circuit 108 at a fixed timing.

The external clamp signal is applied to the clamp circuit 108.
The internal clamp signal and the external clamp signal input from the outside of the liquid crystal display device are externally input signals for designating the clamp period, and are input to the clamp circuit 108 via the selector 111. The selector 111 selects the output of the internal clamp signal or the external clamp signal according to the select signal from the external clamp signal detection circuit 113.

Reference numeral 109 denotes a liquid crystal AC conversion circuit, which converts the video signal output from the clamp circuit 108 into an AC signal having a predetermined frequency (for example, 50 Hz or 60 Hz) and outputs the AC signal to the source driver 103.

Next, an operation example of the liquid crystal display device according to the embodiment of the present invention will be described. The serial strobe signal detection circuit 112 receives the serial strobe signal, generates a select signal based on this, and outputs the generated select signal to the selectors 106 and 107.

This serial strobe signal detection circuit 11
In 2, when a level change is detected in the input serial strobe signal, a level (for example, low level) indicating the second display mode (enlarged display mode) is output as a select signal, and the input serial strobe signal is predetermined. If no level change can be detected during the period of, the level (for example, high level) indicating the first display mode (equal magnification display mode) is output as the select signal.

The external clamp signal detection circuit 113 receives the external clamp signal, generates a select signal based on this, and outputs the generated select signal to the selector 111. When the external clamp signal detection circuit 113 detects a level change in the input external clamp signal, it outputs a level (for example, low level) for selecting the external clamp signal as a select signal to detect the level change of the external clamp signal. If it cannot be detected within the specified period,
A level (for example, high level) for selecting the internal clamp signal is output as a select signal.

[0024]

As is apparent from the above description, according to the present invention, the first display mode in which the received image having the same resolution as that of the liquid crystal display panel is displayed on the liquid crystal display panel at the same size, and the liquid crystal display panel When selecting one of the second display modes for enlarging and displaying the received image with a lower resolution as the display mode on the liquid crystal display panel, it is not necessary to input a select signal (CNTSEL signal) from the outside, and the personal The interface between the signal source and the liquid crystal display device can be simplified without changing the circuit on the signal source side such as a computer.

Further, since it is not necessary to switch the mode selection signal during the functional inspection in the manufacturing process of the liquid crystal display device, the inspection time can be shortened.

According to the present invention, the clamp circuit that clamps the black level of the analog video signal input from the outside is clamped by either the external clamp signal or the internal clamp signal that specifies the clamp period. It is possible to simplify the interface between the signal source and the liquid crystal display device without changing the circuit on the signal source side such as a personal computer, when selecting as an output to the device, it is not necessary to input a select signal from the outside. it can.

Further, since it is not necessary to switch the selection signal of the clamp means at the time of the function inspection in the manufacturing process of the liquid crystal display device, the inspection time can be shortened.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing a circuit configuration example of a conventional liquid crystal display device.

[Explanation of symbols]

101 LCD panel 102 gate driver 103 Source driver 104 1x display control signal generation circuit 105 Enlargement display control signal generation circuit 106, 107, 111 selectors 108 Clamp circuit 109 Liquid crystal alternating circuit 110 Internal clamp signal generation circuit 112 Serial strobe detection circuit 113 External clamp signal detection circuit

─────────────────────────────────────────────────── --- Continuation of the front page (56) Reference JP-A-8-254969 (JP, A) JP-A-11-202834 (JP, A) JP-A-6-282246 (JP, A) JP-A-10- 333630 (JP, A) JP 9-204160 (JP, A) JP 10-187104 (JP, A) JP 11-202837 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G09G 3/36 G02F 1/133 505 G09G 3/20 660

Claims (5)

(57) [Claims] 1. A first display mode in which a received image having the same resolution as that of the liquid crystal display panel is displayed on the liquid crystal display panel at a normal size,
And, one of the display of the second display mode to enlarge the low received video resolution than the liquid crystal display panel to determine the magnification by an input signal comprising a serial strobe signal from the outside on the liquid crystal display panel Mode is selected as a display mode on the liquid crystal display panel.
The display mode selection means and the black level of the analog video signal received from the outside
Clamp means to be clamped and fixed to the clamp means
The black level of the analog video signal is
Generate an internal clamp signal to specify that
Internal clamp signal generating means and the internal clamp signal
And a tie that clamps against the clamping means
The external clamp signal to specify the
One of the signals is used as the output signal to the clamp means.
And a clamp signal selecting means for selecting
In Display device detects a change in the level of the serial strobe signal inputted from the outside, the display mode based on the detection result
Serial strobe signal detecting means for outputting a selection signal to the signal selecting means , and a level change of the external clamp signal inputted from the outside.
And the clamp signal is detected based on the detection result.
External clamp signal detector that outputs the selection signal to the selection means
The display mode selection means has one of the first display mode and the second display mode based on a selection signal input from the serial strobe signal detection means . as well as select the display mode as the display mode in the liquid crystal display panel, the class
Is the external clamp signal detection means.
Based on the selection signal input from the
Signal or one of the external clamp signals
Is selected as an output signal to the clamp means . 2. The serial strobe signal detection means, when detecting the serial strobe signal, sends a selection signal for setting the second display mode to a display mode on the liquid crystal display panel to the display mode selection means. The liquid crystal display device according to claim 1, wherein the liquid crystal display device outputs. Wherein the serial strobe signal detecting means, when said not a serial strobe signal detecting a predetermined period, a selection signal for the first display mode to the display mode in the liquid crystal display panel, wherein Display mode
3. Outputting to a mode selecting means.
The described liquid crystal display device. 4. The external clamp signal detection means, when detecting a change in the level of the external clamp signal, outputs the selection signal that uses the external clamp signal as an output signal to the clamp means, to the clamp signal selection means. the liquid crystal display device according to claim 1, characterized in that the output <br/> force. 5. The external clamp signal detection means, when a change in the level of the external clamp signal is not detected for a predetermined period, a selection signal that uses the internal clamp signal as an output signal to the clamp means, The clamp signal
Claim 1 or 2 and outputs the No. selection means
The described liquid crystal display device.