JP2659601B2 - Liquid crystal display - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a liquid crystal display device.

[Conventional technology]

In recent years, the demand for large-screen, thin liquid crystal display devices has increased in the field of information equipment, mainly computers.
The technology related to the control is becoming important.

Hereinafter, a conventional liquid crystal display device will be described with reference to FIG.

FIG. 3 is a configuration diagram of a conventional liquid crystal display device. In FIG. 3, 1 is a power supply for a liquid crystal display panel, 2 is a CPU, 3 is C
RT controller 4 is C generated from CRT controller 3
A sync signal converter that converts horizontal and vertical sync signals for RT displays to horizontal and vertical sync signals for LCD panels.
It is checked whether the horizontal and vertical synchronizing signals for CRT display generated from the CRT controller 3 are generated as set by the CPU 2, and if they are generated as set, a synchronizing signal determination circuit for generating a signal to the CPU 2, and 6 is a liquid crystal display Display panel, 7 is CPU2
A power supply control circuit for applying the voltage of the power supply 1 for the liquid crystal display panel to the liquid crystal display panel 6 under the control of.

The operation of the liquid crystal display device configured as described above will be described below.

In the initial state, the power supply control circuit 7 is in the off state, and the CRT controller 3 generates a horizontal / vertical synchronization signal whose cycle, high level period and low level period are undefined. Synchronous signal converter 4 is CRT controller 3
Since the horizontal and vertical synchronizing signals are always converted for the liquid crystal display panel 6, the horizontal and vertical synchronizing signals whose period, high level period and low level period are undefined are sent to the liquid crystal display panel 6.

Next, the CPU 2 controls the horizontal
Set an appropriate value in the vertical synchronization signal register. The CRT controller 3 generates a horizontal / vertical synchronization signal according to the set value from the CPU 2. The synchronization signal converter 4 converts a horizontal / vertical synchronization signal from the CRT controller 3 for the liquid crystal display panel 6.

Further, the synchronization signal determination circuit 5 checks the horizontal / vertical synchronization signals generated by the CRT controller 3, and generates a confirmation signal to the CPU 2 when the synchronization signals are generated in a preset cycle and a high level period and a low level period. .

When receiving the confirmation signal from the synchronization signal determination circuit 5, the CPU 2 generates a control signal to the power supply control circuit 7 and applies the voltage of the liquid crystal display panel power supply 1 to the liquid crystal display panel 6.

After the register setting is completed and the synchronizing signal to be set is generated, the liquid crystal display panel power supply 1 is applied before the register setting because the synchronizing signal may be fixed at a high level or a low level. In this case, when the power supply 1 for the liquid crystal display panel is applied, the DC voltage is continuously applied to the liquid crystal, and the liquid crystal may be kept twisted in one direction, thereby deteriorating the liquid crystal display panel 6.

[Problems to be solved by the invention]

However, in the above conventional configuration, the liquid crystal display panel 6
The drive voltage of the liquid crystal display panel 6 must be controlled by the CPU 2 in order not to deteriorate the
LCD panel 6 for the program written for CRT
It was necessary to add a drive voltage control program.

An object of the present invention is to provide a liquid crystal display device capable of preventing the deterioration of the liquid crystal display panel by automatically controlling the drive voltage of the liquid crystal display panel instead of controlling by the CPU.

[Means for Solving the Problems] A liquid crystal display device of the present invention includes a CPU for setting a CRT display synchronization signal, a CRT controller for generating a CRT display synchronization signal set by the CPU, and a CRT display synchronization signal. A synchronizing signal converter for converting a signal into a synchronizing signal for a liquid crystal display, a liquid crystal display panel for inputting a synchronizing signal for a liquid crystal display, a power supply for the liquid crystal display panel for driving the liquid crystal display panel, and a power supply for the liquid crystal display panel. A power supply control circuit that applies voltage to the LCD panel, and a CRT display synchronization signal generated by the CRT controller is detected, and when the cycle of the CRT display synchronization signal matches a preset value, the power supply control circuit is activated. And a period detecting circuit for causing the period to be detected.

[Action]

According to the configuration of the present invention, the control of the drive voltage of the liquid crystal display panel is automatically performed by providing the cycle detection circuit that activates the power supply control circuit when the cycle of the CRT display synchronization signal matches a preset value. This can eliminate the need for the CPU to control the driving voltage of the liquid crystal display panel.

〔Example〕

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

FIG. 1 is a configuration diagram of a liquid crystal display device according to an embodiment of the present invention. In FIG. 1, 1 is a power supply for a liquid crystal display panel,
2 is a CPU, 3 is a CRT controller, 4 is a synchronous signal converter,
6 is a liquid crystal display panel, 7 is a power supply control circuit, 8 is a cycle detection circuit, and 16 is a liquid crystal display device.

The operation of the liquid crystal display device configured as described above will be described below.

In the initial state, the power supply control circuit 7 is in the off state, and the CRT controller 3 generates a horizontal / vertical synchronization signal whose cycle, high level period and low level period are undefined. Synchronous signal converter 4 is CRT controller 3
Since the horizontal and vertical synchronizing signals are always converted for the liquid crystal display panel 6, the horizontal and vertical synchronizing signals whose period, high level period and low level period are undefined are sent to the liquid crystal display panel 6.

Next, the CPU 2 controls the horizontal
Set an appropriate value in the vertical synchronization signal register. The CRT controller 3 generates horizontal / vertical synchronization signals A and B according to the set values from the CPU 2. The synchronizing signal converter 4 converts the horizontal and vertical synchronizing signals A and B for the CRT display from the CRT controller 3 into the horizontal and vertical synchronizing signals for the liquid crystal display panel.

The cycle detecting circuit 8 checks the cycles of the horizontal and vertical synchronizing signals A and B generated by the CRT controller 3 and the high-level period and the low-level period. In order to apply a voltage to the liquid crystal display panel 6, a control signal C is sent to the power supply control circuit 7.

Hereinafter, the cycle detection circuit 8 in this embodiment will be described in detail with reference to the drawings.

FIG. 2 is a configuration diagram of the cycle detection circuit 8 in this embodiment. In FIG. 2, 9 is a horizontal high level detection counter, 10 is a horizontal low level detection counter, 11 is a vertical high level detection counter, 12 is a vertical low level detection counter, 13 is a horizontal synchronization signal detector, 14 Is a vertical synchronization signal detector, and 15 is a synchronization signal comparison / determination unit.

The operation of the cycle detection circuit 8 configured as described above will be described below.

For the horizontal synchronization signal A generated by the CRT controller 3, a high-level period is detected by a horizontal high-level detection counter 9, a low-level period is detected by a horizontal low-level detection counter 10, and a cycle is detected by a horizontal synchronization signal detector 13. Is detected.

For the vertical synchronization signal B generated by the CRT controller 3, a high-level period is detected by the vertical high-level detection counter 11, a low-level period is detected by the vertical low-level detection counter 12, and the cycle is detected by the vertical synchronization signal detector 14. Is detected.

The synchronization signal comparison / determination unit 15 compares the preset value with the detected period of the horizontal / vertical synchronization signals A and B and the high-level period and the low-level period. A signal C is generated, and the voltage of the power supply 1 for the liquid crystal display panel is applied to the liquid crystal display panel 6.

If the liquid crystal display panel power supply 1 is applied when the period of the synchronization signal and the high level period and the low level period are not determined, the liquid crystal display panel 6 may be deteriorated. By applying a voltage of the liquid crystal display panel power supply 1 after outputting a preset synchronization signal to the display panel 6,
The deterioration of the liquid crystal display panel 6 can be prevented.

〔The invention's effect〕

According to the liquid crystal display device of the present invention, a drive voltage control program for the liquid crystal display panel is added to a program conventionally used for CRTs by automatically controlling the drive voltage of the liquid crystal display panel instead of controlling by the CPU. It is possible to prevent the liquid crystal display panel from deteriorating without the necessity.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a liquid crystal display device according to an embodiment of the present invention,
FIG. 2 is a block diagram of the cycle detection circuit 8 in FIG.
FIG. 1 is a configuration diagram of a conventional liquid crystal display device. DESCRIPTION OF SYMBOLS 1 ... Power supply for liquid crystal display panel, 2 ... CPU, 3 ... CRT controller, 4 ... Synchronous signal converter, 6 ... Liquid crystal display panel, 7 ... Power supply control circuit, 8 ... Cycle detection circuit, 16 …
… Liquid crystal display device, A… horizontal sync signal for CRT display, B… vertical sync signal for CRT display, C… control signal

Claims (1)

(57) [Claims] 1. A CPU for setting a synchronizing signal for a CRT display
A CRT controller that generates the CRT display synchronization signal set by the CPU; a synchronization signal converter that converts the CRT display synchronization signal into a liquid crystal display synchronization signal; and a liquid crystal display synchronization signal. A power supply for driving the liquid crystal display panel; a power supply control circuit for applying a voltage of the power supply for the liquid crystal display panel to the liquid crystal display panel; A liquid crystal display device comprising: a period detection circuit that detects a CRT display synchronization signal, and activates the power supply control circuit when the period of the CRT display synchronization signal matches a preset value.