CN111028803B

CN111028803B - Demux driving method

Info

Publication number: CN111028803B
Application number: CN201911308589.0A
Authority: CN
Inventors: 谢建峰; 熊克
Original assignee: Fujian Huajiacai Co Ltd
Current assignee: Fujian Huajiacai Co Ltd
Priority date: 2019-12-18
Filing date: 2019-12-18
Publication date: 2023-09-05
Anticipated expiration: 2039-12-18
Also published as: CN111028803A

Abstract

In the enabling time domain of a Demux subpixel driving signal, the Demux voltage signal is adjusted from an on-state high voltage to a second voltage value, wherein the second voltage value is lower than a normal low voltage, so that a thin film transistor corresponding to the Demux subpixel is turned off in the enabling time domain, and the Demux voltage signal is increased from the lower than the normal low voltage to the normal low voltage. Compared with the prior art, the technical scheme pulls the low voltage of the demux_R/demux_G/demux_B waveform lower, improves the waveform tailing phenomenon of demux_R/demux_G/demux_B, and then raises the lower voltage to the normal low voltage, so as to avoid the occurrence of tailing color mixing. Better display effect is achieved.

Description

Demux driving method

Technical Field

The invention relates to the field of Demux driving, in particular to a Demux driving method design.

Background

For the Demux liquid crystal display, due to some defects of the liquid crystal display, color mixing phenomenon can occur when displaying pictures, and the display effect of the liquid crystal display is affected. This patent avoids this by a special timing design.

In a Demux lcd, since the lcd itself has RC Loading, the waveforms of demux_r/demux_g/demux_b have a tail (refer to the example of fig. 1), and the tail causes the TFT of the next Demux to be turned on when the TFT of the previous Demux has not been completely turned off. Due to the special structure of Demux (see example of fig. 2), when the TFT of the second Demux is turned on, the Source Line controlled by the TFT of the second Demux receives the second data, but at the same time the second transmitted data is also passed to the Source Line controlled by the TFT of the first Demux (at circle 1), which also causes problems at circle 2. Therefore, the color mixing phenomenon of the panel occurs (for example, only red pixels are displayed, but green pixels or blue pixels are also lightened due to waveform trailing), so that the display effect of the liquid crystal display is affected.

Disclosure of Invention

Therefore, it is desirable to provide a new Demux special timing to avoid color mixing problems.

In order to achieve the above objective, the present inventors provide a Demux driving method, in an enabling time domain of Demux subpixel driving signals, performing the following steps, adjusting a Demux voltage signal from an on-state high voltage to a second voltage value, where the second voltage value is lower than a normal low voltage, so that a thin film transistor corresponding to the Demux subpixel is turned off in the enabling time domain, and increasing the Demux voltage signal from the low voltage lower than the normal low voltage to the normal low voltage.

Further, in the enabling time domain of the Demux subpixel driving signal, the method further includes the step of raising the Demux voltage signal from the normal low voltage to a first voltage value, wherein the first voltage value is higher than the on-state high voltage, and the step of lowering the Demux voltage signal from the first voltage value to the on-state high voltage.

Specifically, the action time of the first voltage value is equal to the action time of the on-state high voltage.

Compared with the prior art, the technical scheme pulls the low voltage of the demux_R/demux_G/demux_B waveform lower, improves the waveform tailing phenomenon of demux_R/demux_G/demux_B, and then raises the lower voltage to the normal low voltage, so as to avoid the occurrence of tailing color mixing. Better display effect is achieved.

Drawings

FIG. 1 is a schematic illustration of tailing according to an embodiment;

FIG. 2 is a schematic diagram of a Demux architecture according to an embodiment;

FIG. 3 is a schematic diagram of a Demux timing diagram according to an embodiment;

fig. 4 is a graph of voltage versus time for a specific embodiment.

Detailed Description

In order to describe the technical content, constructional features, achieved objects and effects of the technical solution in detail, the following description is made in connection with the specific embodiments in conjunction with the accompanying drawings.

Please refer to fig. 1, which is a schematic diagram of tailing phenomenon. For the Demux lcd, due to the characteristics of the Demux structure, as shown in fig. 2, it is assumed that the purple-spot picture is now displayed (R subpixel and B subpixel are both bright, G subpixel is not bright, and other pictures such as green picture): looking at the data transmission relation on S1, demux_R is turned on first, S1 transmits + -5V voltage (to make R sub-pixel bright) to D1, demux_G is turned on again, S1 transmits 0V voltage (to make G sub-pixel not bright) to D5, and finally demux_B is turned on, S1 transmits + -5V voltage to D3. This makes the waveform of demux_ R, demux _ G, demux _b trailing possible in the embodiment shown in fig. 1.

For S1, since the waveform of Demux is trailing, D1 is originally transmitted with + -5V, when the TFT of demux_R is not completely turned off, demux_G is turned on, S1 transmits 0V voltage to demux_R, demux_R is transmitted to D1 again, and the voltage level of D1 is not enough to + -5V, so that the brightness of subpixel R is reduced. However, demux_g also has a tailing phenomenon, and at this time, the voltage on D5 is 0V, so that the G sub-pixel is not bright, and when demux_g is not yet completely turned off, demux_b is turned on, S1 sends up ±5v voltage to D3, and at the same time, this voltage is also transmitted to D5, so that the G pixel that should not be bright is also bright, thereby causing a color mixing phenomenon. The principle of color mixing for S2 is the same as that for S1 and is not described here.

Referring to FIG. 1 again, the black circle (1) indicates that the TFT switch of demux_R/demux_G/demux_B is not turned off, and the low voltage of demux_R/demux_G/demux_B is VGL1, i.e., normal low voltage, typically about-10V. (2) When demux_R is not completely turned off, demux_G is turned on to transfer G data to demux_R, causing the data on demux_R to be incorrectly displayed; demux_g has not been completely turned off and demux_b is turned on to transfer B data to demux_g, causing the data on demux_g to be incorrectly displayed. (3) The sub-pixel data of B has a wrap gate, and the next data R will not affect the data of B.

FIG. 3 is a timing diagram of the design of the present scheme, wherein the low voltage of demux_R/demux_G/demux_B is first reduced to VGL2 (i.e. the second voltage value), and then the low voltage of demux_R/demux_G/demux_B is raised to VGL1 (which may be referred to as normal low voltage, on-chip low voltage, low level, etc. as with the normal Demux low voltage). According to the principle of fig. 4 (details below), when the low voltage of demux_r/demux_g/demux_b is designed to be a second more negative voltage value, the Demux can be turned off more quickly by using the Demux waveform with more negative V2 at the same time, so that the tailing phenomenon is obviously reduced, and thus, the falling edge of demux_r/demux_g/demux_b is ensured not to generate the tailing delay phenomenon, and other data are not charged to the in-plane Source Line (such as D1/D2) controlled by the current Demux TFT when the falling edge of demux_r/demux_g/demux_b is not completely turned off yet. Thus, the display effect of the Demux liquid crystal display screen can be optimized. Because of the power consumption problem, when the minimum value of the falling edge of demux_r/demux_g/demux_b reaches V2, the TFT of demux_r/demux_g/demux_b is completely turned off, and then the minimum value of the falling edge of demux_r/demux_g/demux_b is raised to VGL1 (the minimum negative value of common Demux), so that the design saves power consumption and has the best display effect of Demux.

In summary, we provide a Demux driving method, in the enabling time domain of Demux subpixel driving signals, performing the following steps to adjust the Demux voltage signal from the on-state high voltage to the second voltage value, wherein the second voltage value is lower than the normal low voltage, so that the thin film transistor corresponding to the Demux subpixel is turned off in the enabling time domain, and the Demux voltage signal is increased from the lower voltage than the normal low voltage to the normal low voltage. The Demux subpixel driving signal is the driving signal of demux_r, demux_g, or demux_b subpixel, and is meant to be de-interleaved, which is a common function of processing on a display panel. The second voltage value is designed to be lower than the normal low voltage, so that the thin film transistor corresponding to the Demux subpixel is turned off in the enable time domain, and as to whether the Demux voltage signal needs to be raised from the lower voltage to the normal low voltage after the TFT is turned off, the Demux voltage signal is raised even if the TFT is not completely turned off, but because the lowering has been accelerated by the previous pull-down, the Demux voltage signal is raised from the lower voltage to the normal low voltage in advance, and the TFT can be turned off in the enable time domain of the current subpixel, which is a preferable embodiment.

In order to better solve the display problem of the display screen, besides solving the Demux waveform tailing phenomenon, the problems of Demux energy consumption and charging rate can be further solved. In the embodiment shown in FIG. 3, the High voltage of demux_R/demux_G/demux_B is raised to the first voltage value V0 (V0 > V1, V1 is the on-state High voltage on Demux, which can make Demux operate normally, typically 15V), the first voltage value of demux_R/demux_G/demux_B is increased to increase the on-current Ion of demux_R/demux_G/demux_B TFT, so that the charge rate of demux_R/demux_G/demux_B is increased, and the power consumption problem is considered, and the scheme only keeps the High voltage of demux_R/demux_G/demux_B for half the time that demux_R/demux_G/demux_B is turned on, and then decreases to V1 (the normal Demux High voltage, the on-state High voltage, so that the charge rate of demux_G/demux_B is increased, and the power consumption of demux_G/demux_B is saved. In the enabling time domain of the Demux subpixel driving signal, the method further comprises the step of raising the Demux voltage signal from a normal low voltage to a first voltage, wherein the first voltage is higher than the on-state high voltage, and the step of lowering the Demux voltage signal from the first voltage to the on-state high voltage. In a preferred embodiment, the first voltage value is applied for a time equal to the on-state high voltage.

Also for better assistance, a voltage versus time graph is shown in the embodiment shown in fig. 4. According to the charge-discharge formula of RC circuit, V (t) =V2- (V2-V1) exp (-t/RC) =V2 (1-exp (-t/RC)) +V1exp (-t/RC) to obtain the voltage-time curve relationship of FIG. 4, V1 represents the initial voltage before the voltage will change, and V2 is the last voltage input, and reference is made to FIG. 4 for schematic diagram.

It should be noted that, although the foregoing embodiments have been described herein, the scope of the present invention is not limited thereby. Therefore, based on the innovative concepts of the present invention, alterations and modifications to the embodiments described herein, or equivalent structures or equivalent flow transformations made by the present description and drawings, apply the above technical solution, directly or indirectly, to other relevant technical fields, all of which are included in the scope of the invention.

Claims

1. The Demux driving method is characterized by comprising the steps of firstly lifting a Demux voltage signal from a normal low voltage to a first voltage value, wherein the first voltage value is higher than an on-state high voltage, reducing the Demux voltage signal from the first voltage value to the on-state high voltage, and then regulating the Demux voltage signal from the on-state high voltage to a second voltage value, wherein the second voltage value is lower than the normal low voltage, so that a thin film transistor corresponding to the Demux subpixel is turned off in an enabling time domain, the Demux voltage signal is lifted from the normal low voltage to the normal low voltage, and the action time of the first voltage value is equal to the action time of the on-state high voltage.