JPH03259217A - Display quality improving circuit for liquid crystal display - Google Patents

Abstract

PURPOSE:To improve a defect in display quality due to the distortion of a driving waveform by using the output of an exclusive OR gate as a liquid crystal AC signal, repeating AC generation at intervals of plural common lines, and inverting the polarity of each frame signal alternately. CONSTITUTION:A segment driver latch signal LP is inverted by an inverter INV1 to activate the clock input terminal CK of a 1/N frequency dividing circuit 3. Further, the carry output terminal CY is inverted by an inverter INV2 and connected to a load terminal -LD to form a frequency dividing circuit which has an optional frequency division ratio. The output signal T2 of a flip- flop circuit is inputted to one terminal of an exclusive OR gate 6 and inverted and uninverted repeatedly with the liquid crystal AC signal DF connected to the other terminal to obtain an improved liquid crystal AC signal M. Further, the liquid crystal AC signal M is inverted in polarity at intervals of plural common lines and at intervals of a frame in one frame. Consequently, the defect in display quality such as a ghost is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a display quality improvement circuit for a liquid crystal display that improves display quality defects such as contrast defects that occur in a display device using a liquid crystal display.

[Summary of the invention]

In a display device using liquid crystal as a display element, as the display capacity increases, high-duty driving becomes necessary. As a result, the drive waveform is distorted by the resistance of the transparent electrode of the display panel and the capacitance of the liquid crystal layer, and the correct execution voltage is no longer applied, resulting in non-uniform contrast and poor display quality.

In order to overcome the above-mentioned drawbacks, the present invention inverts the driving waveform (liquid crystal alternating current signal) applied between the liquid crystal layers at a frequency division ratio suitable for the display panel each time the latch signal of the segment driver is divided. , and a display quality improvement circuit that alternately inverts the polarity for each frame signal.

[Conventional technology]

Conventionally, the resolution of display quality defects caused by high-duty driving, such as uneven contrast and ghosting, has been achieved by reducing the resistance component of the transparent electrode of the display panel, reducing the resistance component of the segment electrodes and common electrode, or by reducing the bias power supply. The conventional technique is to suppress the distortion of the drive waveform applied between the liquid crystal layers by minimizing the resistance component inserted in series with the liquid crystal layer, such as by lowering the impedance of the liquid crystal layer.

[Problem to be solved by the invention]

However, in recent years, when the display density of display panels is high and high-duty driving is required, it is difficult to resolve display quality defects such as contrast unevenness and ghosting using the conventional methods described above, due to the cost of materials. It has reached its limit in terms of uploading, etc.

Therefore, the present invention aims to improve display quality by devising drive waveforms in order to solve these conventional drawbacks.

(Means for Solving Problem 1) In order to solve the above problem, the liquid crystal alternating current signal applied between the liquid crystal layers of the display panel is divided by the latch signal of the segment driver at a frequency division ratio suitable for the display panel. The alternating current is inverted every cycle, and the polarity is alternately inverted for each frame signal to improve display quality defects caused by distortion of the drive waveform.

[Effect]

As described above, by changing the drive waveform to a waveform that matches the display panel, display quality defects such as non-uniform contrast and ghosting can be improved.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows an embodiment of a display quality improvement circuit for a liquid crystal display that improves a liquid crystal alternating current signal applied between liquid crystal layers. The segment driver latch signal LP from the controller (not shown in the embodiment of the display quality improvement circuit for a liquid crystal display in FIG. 1) is inverted by the inverter INV1 and activates the clock input terminal CK of the 1/N frequency divider circuit 3. Make it.

The 1/N frequency dividing circuit 3 is constituted by, for example, a 74HC161 (synchronous counter with 4-bit precent). By inverting the carry output terminal CY with an inverter INV2 and connecting it to the load terminal LD, a frequency dividing circuit having an arbitrary frequency division ratio can be formed.

The frequency division ratio N can be set by turning on/off the switches s1 to s4 of the 1/N setting circuit 4. Now, assume that the switches 51 to S4 of the 1/N setting circuit 4 are set as follows.

S, = OFF (logic “1”) S, = ON (logic “0”) Ss = 0FF S4 = OFF When carry output signal T+ occurs, 1/N frequency divider circuit 3
The preset data 7 of the present input terminals A-D of
It is preset in synchronization with the fall of the segment driver latch signal LP.

Since the recent data 7 is set by the 1/N frequency divider circuit 4, it becomes DH (hexadecimal).The 1/N frequency divider circuit 3 performs the recent operation when the carry output signal T1 becomes "0" level. The count is increased in synchronization with the fall of the segment driver latch signal LP, and the precent data 7 changes from DH to EH-FH, and the carry output signal TI is generated again. That is, the carry output signal T
1 will be generated every three pulses of the segment driver latch signal LP.

That is, the frequency division ratio of the 1/N frequency divider circuit 3 is 3.

EP and ET of the 1/N frequency divider circuit 3 are enabled by setting them to the "1" level at the clock enable terminal.

The CLR terminal is a clear terminal and becomes active at "1" level.

The carry output signal TI triggers the clock terminal CL of the 751179717071 circuit 5.

The T-type flip-flop circuit 5 is composed of a D-type flip-flop, and operates as a T-type flip-flop by feeding back the output signal to the D terminal.

Therefore, the output Q(7
The output signal Tz) of the 24179717071 circuit is
The frequency of the carry output signal T is divided by %, resulting in a waveform with a duty ratio of 1:1.

The output signal T2 of the T-type flip-flop circuit is input to one terminal of the exclusive OR gate 6, and is repeatedly inverted and non-inverted by the liquid crystal alternating current signal DF before improvement connected to the other terminal. It becomes the liquid crystal alternating current signal M.

The liquid crystal alternating current signal DF before the improvement has a duty-1:1 waveform that changes every frame period.

FIG. 2 shows a timing chart of each of the signals described above.

(4) in FIG. 2 is a timing chart showing the liquid crystal alternating current signal DF before improvement, and the FLM signal in the figure is a frame signal that determines the frame period.

0 in FIG. 2 is a tying chart showing the improved liquid crystal alternating current signal M.

As mentioned above, with the conventional liquid crystal alternating current signal that is inverted every frame, it is difficult to improve display quality defects such as contrast unevenness and ghosting caused by drive waveform distortion caused by high-duty driving of the display panel. If the polarity is reversed for each common line within a frame and for each frame,
The effects of drive waveform distortion can be significantly improved. The improvement circuit is also very simple, and by changing the frequency division ratio of the 1/N setting circuit 4 according to the characteristics of the display panel, the optimum display quality can be achieved.

〔Effect of the invention〕

As described above, the present invention has the advantage that it is possible to improve display quality defects such as non-uniform contrast and ghosting with a simple circuit, and that the display quality can be matched to the optimum display quality for each display panel.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a display quality improvement circuit for a liquid crystal display according to the present invention, FIG. 2 (4) is a time chart of a liquid crystal alternating current signal according to the prior art, and FIG. 2 0 is a liquid crystal alternating current according to the present invention. The time charts of the switching signals are shown. INVI...First inverter INV2...Second inverter 3...1/N frequency dividing circuit 4...1/N setting circuit 5...T tie differential ref 1f 0f 1 circuit 6...・More than exclusive OR gate

Claims (1)

[Claims] In a display device using a liquid crystal display, a 1/N frequency divider circuit divides the latch signal of a segment driver at an arbitrary frequency division ratio, and a 1/N frequency divider circuit sets the frequency division ratio of the 1/N frequency divider circuit.
an N setting circuit, a T-type flip-flop circuit for making the carry output signal of the 1/N frequency divider circuit have a duty ratio of 1:1, and an output signal of the T-type flip-flop circuit to match the frame period. The circuit comprises an exclusive OR gate that repeats inversion with a signal with a duty ratio of 1 to 1, the output of the exclusive OR gate is used as a liquid crystal alternating current signal, and alternating current is repeated for each of a plurality of common lines, A display quality improvement circuit for a liquid crystal display, characterized in that the display quality of the liquid crystal is improved by reversing the polarity for each frame period.