JPH03226715A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To obtain the liquid crystal display device which does not cause its liquid crystal display panel to deteriorate even if the display control signal of a computer is ceased by providing a counter which counts a dot clock outputted from a display control system and a decision means which judges whether or not a horizontal synchronizing signal is outputted from a display control system. CONSTITUTION:This liquid crystal display device consists of the counter 15 which counts the dot clock from the CRT display control system of the computer and the circuit 16 which judges whether or not the computer outputs the horizontal synchronizing signal. Namely, the device is provided with the clock counter 15 which generates a dummy signal even if the signal of the synchronizing signal line from the CRT display control system 1 is ceased and the selector which switches the original synchronizing signal. Consequently, the liquid crystal display device which never causes the liquid crystal display panel 2 to deteriorate even if the horizontal synchronizing signal from the CRT display control system 1 is ceased is obtained.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a liquid crystal display device.

Conventional technology In recent years, in the field of information equipment centered on computers, there has been an increasing demand for display devices with larger screens and thinner LCD devices than CRT display devices. Technology related to control functions is becoming important.

Figure 2 is a block diagram of a control system for converting CRT display signals into liquid crystal display signals. In this figure, 1 is a combination CRT display control system, 2 is an LCD display panel, and 3 is a CR7 display. CR generated from control system 1
7 display data signal line, 4 is CR7 display data 3 to LCD
5 is an LCD display data signal line generated from the data conversion circuit 4; 6 is a CR
7 a dot clock signal line generated from the display control system 1; 7 a transfer lock conversion circuit that converts the dot clock signal line 6 into a transfer lock for LCD display data; 8 a transfer lock conversion circuit generated from the transfer lock conversion circuit 7; A lock signal line, 9 is a CRT horizontal synchronizing signal line generated from the CR7 display control system 1, 10 is a horizontal synchronizing signal conversion circuit that converts the CRT horizontal synchronizing signal 9 into a horizontal synchronizing signal for LCD, and 11 is a horizontal synchronizing signal converting circuit 10 12 is a CRT vertical sync signal line generated from the CR7 display control system 1, 13 is a CRT vertical sync signal 12
14 is an LC generated from the vertical synchronization signal conversion circuit 13.
D vertical synchronization signal line.

Next, the operation of this liquid crystal display device will be explained.

The display control signal for the CRT display generated from the CR7 display control system 1 is not compatible with the LCD display panel 2. For example, CRT display data is displayed at 1 on the display screen.
While it is serial data corresponding to pixels, LCD
The display data for 4 to 8 pixels must be transferred to the LCD display panel as 4 to 8 bit parallel data. For this purpose, the conventional liquid crystal display device has a data conversion circuit 4. Transfer lock conversion circuit 7. Horizontal synchronization signal conversion circuit 10. A control signal suitable for the LCD display panel is created by serial/parallel conversion of the CR7 display data from the CR7 display control system 1 of the computer using the vertical synchronization signal conversion circuit 13 and by shifting the timing of the synchronization signal. Ta. Therefore, when the signal from the CR7 display control system 1 stops, the LCD display control signal stops, and when a signal is generated, the LCD display control signal is generated again.

Problems to be Solved by the Invention However, in the conventional configuration described above, when the control signal from the CR7 display control system 1 stops in the initial state of the computer or at the time of reset, the control signal to the LCD display panel stops, and the LCD Not only does the display stop, but the vertical scanning of the LCD display panel also stops due to the stop of the horizontal synchronization signal, causing D to appear on unspecified lines on the display screen.
C voltage is applied. The DC voltage applied to this uncharacteristic line significantly deteriorates the characteristics of the liquid crystal panel.

The present invention solves the above-mentioned conventional problems, and aims to provide a liquid crystal display device that does not cause deterioration of the liquid crystal display panel even if the display control signal of a combination display stops.

Means for Solving the Problems In order to achieve this object, the liquid crystal display device of the present invention comprises:
It consists of a counter that counts dot clocks from the CRT display control system of the computer, and a circuit that determines whether or not a horizontal synchronizing signal is output from the computer.

Effect: With this configuration, it is possible to realize a liquid crystal display device that does not cause deterioration of the liquid crystal display panel even if the display control signal of the combination unit is stopped.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows a configuration diagram of a liquid crystal display device according to an embodiment of the present invention. In FIG. 1, reference numeral 15 is a clock counter that counts signals on the dot clock signal line 6 from the CRT display control system 1 and generates ripple carry;
1 is a horizontal synchronizing signal output determination circuit that checks the presence or absence of an output signal on the CRT horizontal synchronizing signal line 9 generated from the CR7 display control system 1, and generates a flag if it is not output;
Reference numeral 7 denotes a selector that switches between the carry and -outputs of the clock counter 15 and the output from the horizontal synchronization signal conversion circuit 10 according to a flag from the horizontal synchronization signal output determination circuit 16, and outputs the LCD horizontal synchronization signal to the signal line 11.

In addition, 1 is a CRT display control system, 2 is an LCD display panel, 3 is a CR7 display data signal line, 4 is a data conversion circuit, 5 is an LCD display data signal line, 6 is a dot clock signal line, and 7 is a transfer lock conversion. circuit, 8 is a transfer lock signal line, 9 is a CRT horizontal sync signal line, 10 is a horizontal sync signal conversion circuit, 11 is an LCD horizontal sync signal line, 12 is a CR
T vertical synchronization signal line, 13 is a vertical synchronization signal conversion circuit, 14
is an LCD vertical synchronizing signal line, and these lines are the same as those in the conventional example.

Next, the operation of the liquid crystal display device of the present invention will be explained.

When a valid display control signal is generated from the CR7 display control system 1, the appropriate control signal is converted to the LCD display panel as in the conventional example.

Next, assume that the signal from the CRT display control system 1 to the horizontal synchronizing signal line 9 is stopped due to, for example, a reset of the computer. Then, the horizontal synchronizing signal output determination circuit 16 determines that the signal on the horizontal synchronizing signal line 9 has stopped, and generates a flag. On the other hand, CRT display control system 1
The dot clock signal line 6 generated from the dot clock signal line 6 is usually the basic clock of the computer or the CRT display control system 1
Since the internal basic clock is used, the clock continues to be generated unless the power is turned off. clock counter 1
5 continues to count the signals on the dot clock signal line 6 and generate ripple carry unless the power is turned off. The selector 17 which has received the flag from the horizontal synchronization signal output determination circuit 16 switches the input from that of the horizontal synchronization signal conversion circuit 10 to the ripple carry from the clock counter ]-5, Generate a signal.

Effects of the Invention As described above, according to the present embodiment, even if the signal on the horizontal synchronization signal line 9 from the CRT display control system 1 stops, switching between the clock counter that generates a pseudo signal and the original synchronization signal can be performed. By providing a selector for CRT
It is possible to realize a liquid crystal display device in which the liquid crystal display panel 2 does not deteriorate even if the horizontal synchronization signal from the display control system 1 stops.

[Brief explanation of drawings]

FIG. 1 is a block diagram of main parts of an apparatus according to an embodiment of the present invention, and FIG. 2 is a block diagram of main parts of a conventional apparatus. 1... CRT display control system, 2...
・LCD display panel, 3...CRT display data signal line, 4...data conversion circuit, 5...
・LCD display data signal line, 6...Dock clock signal line, 7...Transfer lock conversion circuit, 8
...Transfer lock signal line, 9...CR
T horizontal synchronization signal line, 10...Horizontal synchronization signal conversion circuit, 11...LCD horizontal synchronization signal line, 12.
...CRT vertical synchronization signal line, 13 ... Vertical synchronization signal conversion circuit, ]4 ... LC'D vertical synchronization signal, 15 ... Clock counter, 16・・・
...Horizontal synchronization signal output determination circuit, 17...
selector.

Claims (1)

[Claims] In a liquid crystal display device that converts signals generated from a display control system into display signals that can be displayed on a liquid crystal display panel, there is provided a counter that counts dot clocks output from the display control system, and a horizontal dot clock output from the display control system. A liquid crystal display device comprising: determination means for determining whether or not a synchronization signal is output.