JPH05199482A - Liquid crystal driving system - Google Patents

Abstract

PURPOSE:To improve the contrasts for display of a TV image which is horizontally long and has a wide aspect ratio by applying the same potential as a signal electrode to the prescribed number of scanning electrodes of both upper and lower ends. CONSTITUTION:A control circuit 4 inputs the horizontal and vertical synchronizing signals from a receiving circuit 1 and produces various types of control signals and liquid crystal driving voltage, i.e., the signals EC and CFK and the voltage V1, V3 and VDD to supply them to a signal electrode driving circuit 5. At the same time, the signals EC and CKF and the driving electrode V2, V4 and GND are supplied to a scanning electrode driving circuit 6. The circuit 5 outputs a signal electrode driving signal in accordance with the video data given from an A/D converter 5 and drives the signal electrode of a liquid crystal display panel 7. The circuit 6 shifts the scanning electrode data sent from the circuit 4 synchronously with the shift lock of the scanning electrode. Then the scanning electrode of the panel 7 is driven in response to the shifted data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal driving system of a liquid crystal display device for displaying a television image of a wide aspect ratio having a long horizontal direction.

[0002]

2. Description of the Related Art FIG. 7 shows drive waveforms of a liquid crystal drive system in which contrast is improved by using a memory of a conventional liquid crystal display device. This drive waveform is a 120 Hz drive waveform of a vertically divided simple matrix LCD (liquid crystal display panel) having 240 scanning lines and n signal lines. Generally, one screen of the LCD is composed of one frame consisting of an odd field and an even field, but they are regarded as the same signal for simplification.
Thus, 240 of the scanning lines corresponding to 265.5 lines in one field period are used as the display period, and the vertical blanking period VL is set to the idle period. The liquid crystal drive voltage is V1, V3, VDD (= V as shown in FIG.
2) is supplied to the signal electrodes, and V2, V4, and GND are supplied to the scan electrodes. The liquid crystal drive voltages V1, V2, V
3, V4, GND and VDD are set with V1 and GND centered on V2 and VDD on the positive side and V3 and V4 on the negative side with a certain voltage difference. FIG. 9 shows a scanning method. Scanning electrodes are plotted on the vertical axis and time is plotted on the horizontal axis, and real image data (raw image data not passing through the memory) R and memory image data M are alternately scanned. In the vertical blanking period VL, as shown in FIG. 7, the voltage of the scan electrode becomes V2 which is the non-selection level, and the signal electrode becomes the voltage level of VDD. This VDD is V2 of the scan electrode as shown in FIG.
And the same potential as. That is, the scan electrode and the signal electrode have the same potential during the vertical blanking period VL, and no voltage is applied to the liquid crystal. That is, it is possible to prevent an increase in the effective value of the voltage applied to the liquid crystal during the vertical blanking period VL, and increase the effective value ratio of ON / OFF to improve the contrast.

Next, FIG. 10 shows a wide aspect of the second generation EDTV system. That is, the original image with the aspect ratio of 16: 9 shown in FIG. 10A is masked at the top and bottom from the conventional screen with the aspect ratio of 4: 3 shown in FIG. 10B to widen the aspect ratio of 16: 9. A letterbox method for displaying a screen and a 16: 9 aspect ratio by separately transmitting the horizontal portion on a screen having an aspect ratio of 4: 3 as shown in FIG.
A side panel method is considered in which a wide screen with an aspect ratio of. Among them, the letterbox wide screen shown in FIG. 10B has the screen size shown in FIG. That is, the wide screen is compressed to 360 lines and placed on the main panel while keeping the aspect ratio of 16: 9, and the upper and lower 60 lines are black, and the high frequency auxiliary information is multiplexed. To be done. When this signal is received by the current NTSC receiver,
As shown in (b), it is displayed on a wide screen having an aspect ratio of 16: 9. Therefore, the display on the LCD by the driving method as shown in FIG. 7 is also possible.

[0004]

However, in the case of a wide screen having an aspect ratio of 16: 9, the display range may be narrowed, and an image with better contrast is desired. That is, the upper and lower hatched portions shown in FIG. 10B indicate "black", and the drive duty of the liquid crystal is the same as when the entire screen with an aspect ratio of 4: 3 is displayed. Therefore, a part of the driving margin is taken in a portion without a display image, which causes a problem of poor efficiency.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a liquid crystal driving system capable of improving the contrast when displaying a television image having a wide aspect ratio that is long in the horizontal direction.

[0006]

In order to solve the above-mentioned problems, the present invention has a structure in which scanning electrodes and signal electrodes are arranged in a matrix to display a television image having a predetermined aspect ratio, and is more horizontal than this aspect ratio. In a liquid crystal driving method of a liquid crystal display device that displays a television image with a long aspect ratio, when displaying a television image with a long horizontal aspect ratio, a predetermined number of scans of the upper end and the lower end of the scan electrode are performed. The same potential as the signal electrode is applied to the electrodes.

[0007]

According to the above means, when a television image having a long horizontal aspect ratio is displayed, the same potential as that of the signal electrode is applied to a predetermined number of scan electrodes at the upper end and the lower end of the scan electrode, so that the vertical It is possible to prevent an increase in the effective value of the voltage applied to the liquid crystal during the blanking period and before and after the blanking period, and to increase the effective value ratio of ON / OFF to improve the contrast.

[0008]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a schematic configuration diagram of an embodiment of the present invention. That is, the receiving circuit 1 receives the television signal from the antenna 2, extracts the video signal Sv, the horizontal synchronizing signal φH, and the vertical synchronizing signal φV, and outputs the video signal Sv to the A / D conversion circuit 3.
The horizontal synchronizing signal φH and the vertical synchronizing signal φV are supplied to the control circuit 4, respectively. The control circuit 4 receives a zero bias control signal EC, an inversion signal CKF, various other control signals (the description is omitted), liquid crystal driving voltages V1, V2, V3, V from the input horizontal synchronizing signal φH and vertical synchronizing signal φV.
4, GND, VDD = V2, zero bias control signal EC, inverted signal CKF, liquid crystal drive voltage V
1, V3, VDD are supplied to the signal electrode drive circuit 5, and the zero bias control signal EC, the inversion signal CKF, and the liquid crystal drive voltages V2, V4, GND are supplied to the scan electrode drive circuit 6, respectively. The inversion signal CKF is a signal that is inverted in synchronization with the scan electrode shift clock to select the scan electrode drive voltage of GND or V4. Further, the zero bias control signal EC is set according to the number of thinning lines of the scanning line, and is always at the "1" signal level, but the "0" signal level is set at every preset horizontal cycle. Becomes The liquid crystal drive voltages V1, V2, V3, V
4, GND, VDD are V1, VDD centered on V1,
GND is set to the positive side and V3 and V4 are set to the negative side with a constant voltage difference. The A / D conversion circuit 3 converts the video signal sent from the reception circuit 1 into, for example, 4-bit digital data, and supplies it to the signal electrode drive circuit 5. The signal electrode drive circuit 5 outputs a signal electrode drive signal in accordance with the video data sent from the A / D conversion circuit 3 to drive the signal electrodes of the liquid crystal display panel 7 for display. On the other hand, the scan electrode drive circuit 6 includes a shift register for generating a scan signal, shifts the scan electrode data sent from the control circuit 4 in synchronization with the scan electrode shift clock, and shifts the inside of this shift register. The scan electrodes of the liquid crystal display panel 7 are sequentially driven according to the data to be shifted.

Thus, the signal electrode drive circuit 5 is constructed as shown in FIG. This FIG. 3 shows the signal electrode drive circuit 5
2 shows the main part of one of the signal electrode driving systems. The liquid crystal drive voltages V1, V3 and VDD are supplied from the control circuit 4 to the signal electrode drive circuit 5, the liquid crystal drive voltage V1 is output to the output line 21 via the gate circuit G1, and the liquid crystal drive voltage VDD is supplied to the gate circuit. It is output to the output line 21 via G2 and to the output line 22 via the gate circuit G3. Also, the liquid crystal drive voltage V
3 is output to the output line 22 via the gate circuit G4. Then, the zero bias applied from the control circuit 4
The control signal EC is level-shifted by the level shifter 23, and then supplied to the gate circuits G1 and G4 as a gate signal and further supplied via the inverter 24 to the gate circuits G2 and G3 as a gate signal.
Then, the voltage taken out from the output line 21 is sent to the multiplexer (not shown) as the liquid crystal drive voltage V1 'and the voltage taken out from the output line 22 is sent to the multiplexer (not shown). The output voltage of this multiplexer is the video data from the A / D conversion circuit 3 and the inverted signal C.
It is selected according to KF and sent to the liquid crystal display panel 7 as a signal electrode drive signal. Then, in the vertical blanking period and the periods of 30H (horizontal scanning period) before and after that period,
The zero bias control signal EC becomes low level, the output of the inverter 24 becomes high level, and the gate circuit G
2 and G3 are turned on, the gate circuits G1 and G4 are turned off, and both the output lines 21 and 22 output the voltage VDD. The voltage VDD is a voltage level when “the potential of the signal electrode = the potential of the scan electrode” which gives zero bias. In addition, except during the vertical blanking period and the period of 30H before and after the blanking period, that is, during normal operation, zero bias
The control signal EC becomes high level, the output of the inverter 24 becomes low level, the gate circuits G2 and G3 are turned off, the gate circuits G1 and G4 are turned on, and the voltage V3 is output from the output line 21 and the voltage V3 is output from the output line 22. To be done. Therefore, the signal electrode drive circuit 5 outputs the voltage of V1 or V3 as the signal electrode drive voltage according to the image data sent from the A / D conversion circuit 3.

On the other hand, the scan electrode drive circuit 6 has a main part as shown in FIG. The liquid crystal drive voltages V2, V4, and GND are applied to the scan electrode drive circuit 6 from the control circuit 4. GND is input to the signal line 33 via the P-type MOS transistor 31 and the gate circuit G11, and V4 is an N-type MOS. Transistor 32 and the gate circuit G11
To the signal line 33, and V2 is directly input to the signal line 34. The signal line 33
A gate circuit G12 connects between and. The signal line 33 is connected to the gate circuits G13a and 13b.
……… through scanning signal output terminals OUT1 and O respectively
UT2 ......... is connected. Further, the signal line 34 is connected to the scanning signal output terminals OUT1, OUT2, ... Through the gate circuits G14a, 14b.
Then, the inverted signal CKF is input to the gates of the MOS transistors 31 and 32 via the level shifter 35.
The zero-bias control signal EC sent from the control circuit 4 is level-shifted by the level shifter 36 and then input to the gate of the gate circuit G11.
Further, in the scan electrode driving circuit 6, scan signals IN1, IN2 ... Are produced by an internal shift register in accordance with the timing signal sent from the control circuit 4. The scanning signals IN1, IN2 ... Are level-shifted by the level shifters 38a, 38b .. It is input to the gates of the gate circuits G14a, G14b ....

FIG. 2 shows the drive waveforms of FIG. This drive waveform is a 120 Hz drive waveform of a vertically divided simple matrix LCD having 240 scanning lines and n signal lines. LCD in general
Although one screen is composed of one frame consisting of an odd field and an even field, they are regarded as the same signal for simplification. Thus, within one field period, 26
Of the scanning lines corresponding to 5.5 lines, the display period is 24
The vertical blanking period VL + 60H is a rest period by using zero lines. The liquid crystal drive voltages V1, V2, V3, V4
GND and VDD are V1 and GN with V2 and VDD at the center.
D is set to the positive side and V3 and V4 are set to the negative side with a constant voltage difference. In the quiescent period of the vertical blanking period VL + 60H, the voltage of the scan electrodes X1 to X240 becomes V2 which is a non-selection level, and the signal electrodes Y1 to Yn are V.
The voltage level becomes DD. This VDD (Y) has the same potential as V2 of the scan electrodes X1 to X240. In other words, during the rest period of the vertical blanking period VL + 60H, the scan electrode X1
To X240 and the signal electrodes Y1 to Yn have the same potential, and no voltage is applied to the liquid crystal. That is, it is possible to prevent an increase in the effective value of the voltage applied to the liquid crystal during the quiescent period of the vertical blanking period VL + 60H, and increase the effective value ratio of ON / OFF to improve the contrast.

That is, in the letterbox system of the second generation EDTV, 60 lines at the top and bottom, that is, 30 lines at the interlaced scanning are not displayed on the screen. Therefore, when this is received, the scan electrodes X1 to X240 and the signal electrodes Y1 to Yn are set to the same potential in the vertical blanking period VL and 30H before and after the blanking period VL, so that the liquid crystal of The effective value ratio of ON / OFF can be increased, and the contrast can be improved.

FIG. 5 is a schematic configuration diagram of another embodiment of the present invention, which shows a liquid crystal driving system of a liquid crystal display device at the time of receiving an HDTV broadcast. That is, the HDTV broadcast is the current NTSC /
MUSE / NTSC to receive with TV broadcast receiver
Converter 50 is required.

FIG. 6 shows a MUSE / NTSC converter 50.
It is a block diagram showing an example. That is, the input MU
The SE signal is supplied to the A / D conversion circuit 53 via the low-pass filter (LPE) 51 and the clamp circuit 52.
The A / D conversion circuit 53 A / D-converts the input MUSE signal with a sampling frequency of 16.2 MHz and 8-bit precision, and supplies it to the non-linear de-emphasis circuit 54. Since the MUSE signal is subjected to non-linear emphasis on the transmission side to improve the S / N, the non-linear de-emphasis circuit 54 performs non-linear processing and then de-emphasis by a 7-tap digital filter to convert the time axis. Supply to the circuit 55. The time axis conversion circuit 55 has a 16 Kbyte memory corresponding to about 525 lines of about 50 lines, and using this as a buffer, the portion corresponding to the aspect ratio 4: 3 from the input MUSE signal with the aspect ratio 16: 9. Only the vertical axis of the Y vertical filter 5 is extracted.
6, RY vertical filter 57, BY vertical filter 58
Is supplied to each. Y vertical filter 56 is MUSE
By halving the vertical pass band composed of a digital filter with 3 taps in the vertical direction with respect to the signal, and thinning out one of the 1125 scanning lines to reproduce the signal of 525 scanning lines, Y The number of scanning lines of the signal is converted.
The RY vertical filter 57 and the BY vertical filter 58
Are respectively composed of two taps and three taps in the vertical direction. The MUSE signal transmits color signals line-sequentially. Therefore, in the RY signal, (1/2, 1/2), B-
For the Y signal, a vertical filter is constructed using different tap coefficients of (1/4, 1/2, 1/4), and the RY signal,
The number of scanning lines of the BY signal is converted from 1125 to 525. The Y signal, the RY signal, and the BY signal filtered by the Y vertical filter 56, the RY vertical filter 57, and the BY vertical filter 58 are blanked in the unnecessary signal period, and then are respectively corresponding D The A / A conversion circuits 59, 60, 61 perform D / A conversion, and the matrix circuit 65 passes the low-pass filters (LPF) 62, 63, 64 to produce the respective video signals R, G, B. In FIG. 6, reference numeral 66 denotes a 1125 system first PLL circuit (P
LL1) and 67 are second PLL circuits (PLLs) of the 525 system.
2) and 68 are first control signal generating circuits, and 69 is a second control signal generating circuit.

That is, the MUSE / NTSC converter 50
The video signals R, G, B output from the A / D conversion circuit 3
Is supplied to. The horizontal synchronizing signal φH and the vertical synchronizing signal φV are supplied to the control circuit 4. The control circuit 4 uses the input horizontal synchronizing signal φH and vertical synchronizing signal φV for zero bias
Control signal EC, inverted signal CKF, other various control signals (explanation omitted), liquid crystal drive voltages V1, V2, V
3, V4, GND, VDD = V2 are generated, the zero bias control signal EC, the inversion signal CKF, and the liquid crystal drive voltages V1, V3, VDD are supplied to the signal electrode drive circuit 5, and the zero bias control signal EC, inversion. Signal C
KF and liquid crystal drive voltages V2, V4 and GND are supplied to the scan electrode drive circuit 6, respectively. The A / D conversion circuit 3 is M
The video signals R, G, B sent from the USE / NTSC converter 50 are converted into 4-bit digital data, for example, and supplied to the signal electrode drive circuit 5. The signal electrode drive circuit 5 outputs a signal electrode drive signal in accordance with the video data sent from the A / D conversion circuit 3 to drive the signal electrodes of the liquid crystal display panel 7 for display. On the other hand, the scan electrode drive circuit 6 includes a shift register for generating a scan signal, shifts the scan electrode data sent from the control circuit 4 in synchronization with the scan electrode shift clock, and shifts the inside of this shift register. The scan electrodes of the liquid crystal display panel 7 are sequentially driven according to the data to be shifted.

Thus, when a wide mode HDTV broadcast is received by the current NTSC / TV broadcast, the aspect ratio of the wide mode HDTV broadcast reception screen is 16: 9 and N.
Due to the difference in the aspect ratio 4: 3 of the TSC / TV broadcast reception screen, 60 lines at the top and bottom, that is, 30 lines at the time of interlaced scanning are not displayed on the screen. Therefore, when this is received, the scan electrodes X1 to X240 and the signal electrodes Y1 to Yn are set to the same potential in the vertical blanking period VL and 30H before and after the blanking period VL, so that the liquid crystal of The effective value ratio of ON / OFF can be increased, and the contrast can be improved.

[0018]

As described above, according to the present invention, when displaying a television image having a long horizontal aspect ratio,
By applying the same potential as the signal electrodes to a predetermined number of scan electrodes at the upper and lower ends of the scan electrodes, an increase in the effective value of the voltage applied to the liquid crystal during the vertical blanking period and before and after it is prevented. Therefore, it is possible to improve the contrast by increasing the effective value ratio of ON / OFF.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a waveform diagram showing an example of the drive waveforms in FIG.

3 is a circuit diagram showing an example of a signal electrode drive circuit of FIG.

4 is a circuit diagram showing an example of a scan electrode driving circuit of FIG.

FIG. 5 is a block diagram showing another embodiment of the present invention.

6 is a block diagram showing an example of the MUSE / NTSC converter of FIG.

FIG. 7 is a waveform diagram showing an example of drive waveforms of a conventional liquid crystal drive system.

FIG. 8 is an explanatory diagram showing a voltage relationship between a signal electrode applied voltage and a scan electrode applied voltage.

FIG. 9 is an explanatory diagram showing a conventional liquid crystal driving type scanning method.

FIG. 10 is an explanatory diagram showing a wide aspect aspect of the liquid crystal display device.

FIG. 11 is an explanatory diagram showing a letterbox wide screen.

[Explanation of symbols]

1 ... Receiving circuit, 2 ... Antenna, 3 ... A / D conversion circuit, 4
Control circuit, 5 signal electrode drive circuit, 6 scan electrode drive circuit, 7 liquid crystal display panel.

Claims (1)

[Claims] 1. A liquid crystal display device in which scanning electrodes and signal electrodes are arranged in a matrix form to display a television image having a predetermined aspect ratio and a television image having an aspect ratio longer in the horizontal direction than this aspect ratio. In the liquid crystal driving method, when displaying a television image with a long horizontal aspect ratio, a means for applying the same potential as the signal electrode to a predetermined number of scan electrodes at the upper end and the lower end of the scan electrode is provided. A liquid crystal driving method characterized by being equipped.