JPS59115680A - Ac driving method of liquid crystal television - Google Patents

Abstract

PURPOSE:To form stably a liquid crystal driving AC signal even with missing of signal and presence of noise in an external vertical synchronizing signal by providing a circuit inhibiting the input of the external vertical synchronizing signal to the 1st control terminal for a prescribed period in response to the internal state of a vertical synchronizing control signal forming circuit. CONSTITUTION:A signal 2 extracting the vertical synchronizing signal component only from a composite video signal through a synchronizing separation circuit and an integration circuit is subject to the change in radio wave, ability of a receiver or the like, because no PLL or the like is used in general, and mixture of noise and missing of synchronizing signal or the like are generated. In Figure, 3 is a counter taking a horizontal synchronizing signal of 1 as an input clock, an external clock is counted, the vertical synchronizing control signal of a frequency coincident with the frequency of the vertical synchronizing signal is outputted and a control terminal possible for external synchronism is provided, 4 is a circuit inhibiting the input for a prescribed period in response to the internal state of the counter 3, and its output is connected to an external synchronism terminal of the counter 3, F is a signal frequency-dividing the vertical synchronizing signal by 1/2 and is not subject to the noise component G of the A and the missing of signal H.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides liquid crystal display in LCD TVs. In general, when a liquid crystal is used as a display element, it is driven by AC to prevent deterioration.7 In addition, in the case of a liquid crystal TV, phenomena other than deterioration of the DC-driven Fi liquid crystal occur. Even if the display part (C1) is simply a liquid crystal placed between the electrodes, if the liquid crystal is placed on an integrated circuit like an active panel, 5i is connected in series to the liquid crystal.
During AC drive, sufficient driving pressure is applied to the liquid crystal due to the inverse ratio of the capacitance ratio between SiOs and the liquid crystal, but during DC drive, the DC resistance ratio of 5ins to the liquid crystal is applied to the liquid crystal. The driving voltage is applied and E! If the DC resistance of the ion is high enough, sufficient driving voltage will not be applied to the liquid crystal and the display will disappear.7This means that even if the D-crystal is severely degraded, the TV screen itself will be means that the llrll plane disappears. In this way, in the normal use of liquid crystals, even if instantaneous DC driving is used, the display can be maintained, but in the above case, instantaneous DC driving will have a negative effect on the TV image. In addition to the liquid crystal display device with the structure described above, it is conceivable that instantaneous direct drive may affect image quality in other display devices as well.

For this reason, in the case of P-crystalline TV equipment, a sufficiently stable current drive system is required.

In the case of an LCD TV, the frequency of transmission is about 30 Hz, and in the case of the NTSO system, it is an odd field.

The polarity is reversed in even τ9 field. At this traffic signal 1.

In order to eliminate the 1m1 period between both sides, it is sufficient to divide the 16 synchronization signals by 11i and then ->-divide the composite video signal that has been received and detected by the tuner.

However, this vertical synchronization signal ID, which is obtained by receiving Tv radio waves, is affected by the magnitude of the absolute value of the electric field strength, sudden changes in the electric field strength, noise, etc.

Due to the characteristics of the sheep user's synchronous detection ability, it is not perfect.In particular, LCD TVs should be used in a stationary state with a sufficient antenna erected. Since there is a high possibility that the obtained vertical synchronization signal may be mixed with noise or lack of character.For this reason, even if you simply generate a liquid crystal cross ff1t drive signal based on @direct synchronization belief, the original Due to the imperfection of Shinshichi, it was not possible to drive the liquid crystal with sufficient alternating current.

The uninvented model is a model that eliminates such drawbacks, and its purpose is based on the shape of the TV radio wave Qμ, the ability of the injured device, etc.

The objective is to provide a sufficient liquid crystal AC drive signal even if the external vertical rotation signal contains noise or signal dropout occurs.

Hereinafter, the present invention will be described in detail based on Examples.

FIG. 1 is a block diagram of the present invention, and FIG. 2 is a time chart.

1 is a Nf)I signal generation trace, which is configured by a PLL. B is the same clock as the horizontal 1Ij1 period signal, and the frequency is an integral multiple of the horizontal frequency. Generally, the horizontal synchronization signal is passed from the composite video signal to the south exit circuit.

The horizontal synchronizing signal is stabilized by the Nf)I signal generation circuit 1, which is constructed using a PLL.

2 is a signal obtained by extracting only the vertical synchronization signal component from the composite video signal through a synchronization pre-conditioning and integration circuit. This vertical synchronization signal generally does not use FLT, etc., so it is affected by changes in radio waves, receiver capabilities, etc., and noise contamination, synchronization signal omission, etc. occur.
7. Count the external clock using a counter that inputs the horizontal synchronization signal and outputs a vertical synchronization signal with a frequency that matches the frequency of the vertical synchronization signal.7. It has a control terminal that allows external synchronization. The output is connected to the external synchronization terminal of the counter 6, and the output is connected to the external synchronization terminal of the counter 6. 7-15
divides the same frequency as the vertical synchronization signal using a frequency divider.

In the tight cat of the second section 1, A is 2 in Fig. 1, which is the external vertical synchronization signal, Gld noise component, H is the signal dropout, 6B is 1 in Fig. 1, and the counter is 3. is the input clock of This signal corresponds to the internal state of the counter of 0IJ5. In this case, it becomes H at a portion other than the regular vertical synchronization signal, and controls 4 and prohibits the passage of the external vertical synchronization signal of 2.

D is the output that passed through 4 and the 30 counter is external vertical li1
Synchronize with period control beliefs. compared to the signal to.

Since the noise component G does not pass through, it disappears. Otsu 6 Vertical rotation control signal missing remains as 1, but the counter 5 is free-running at the same frequency as the vertical synchronization signal if there is no control ζ f1 - 1 The synchronization of the .3 counter is disturbed. With the output of the Eke3 counter.

3, the external vertical cycle signal omission I4 also occurred in January. F(d') A signal that sufficiently uses the vertical synchronization signal and is not affected by the noise component G of %A and the double signal H.

Specifically, in the case of the Id, M/NTso method, the horizontal synchronization signal id f)l = approximately 15,754K)lz, and the vertical synchronization signal fD = approximately 60Hz, so if 1 is NfH, then n-N-fH/ So that fD becomes &n 1M device,
The reset end beam or set terminal can be used as an external synchronization terminal, and the control signal of C can be easily created using a normal logic circuit.
Possible 64 transmission gate or AND
This can be easily realized with gates, etc.

In this way, it is easily realized, and even if there is a miscellaneous signal or a signal dropout in the external vertical synchronizing signal, the AC signal for driving the liquid crystal can be stably generated.

If this stable AC drive signal is used, instantaneous DC drive tends to occur, but stabilizes to one screen.

However, if the tuner is synchronized, and the composite video signal output is only a noise-like component, the horizontal synchronization signal,
It may be input to an external vertical synchronization signal.

Since a clock such as the free run frequency of the input terminal 1 [1f PLL shown in FIG.

Although t7j3.5 was explained as a separate block, it is also possible to incorporate it into the counter of 5's sufficient cylinder I''i,'l.
The present invention can also be applied to TV systems such as the PKOA system, the PKOA system, and the M system.

In addition, the wooden sword method can be used not only to create a stable LCD AC drive signal (but also when a stable output is required when noise components are mixed into the input signal or when there is a signal dropout).

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the present invention, and FIG. 2 is a time chart of the present invention.

Claims (1)

[Claims] Count the input clocks 2. Creating a vertical synchronization control signal having a first control terminal for outputting a vertical synchronization control signal with a frequency matching the frequency of an external vertical synchronization signal and synchronizing the external vertical synchronization signal and the vertical synchronization control signal. and a circuit for prohibiting input of an external vertical synchronization signal to the control terminal gl for a certain period of time corresponding to the internal condition of the vertical synchronization control signal generation port μ, and the vertical synchronization control signal generation circuit. A liquid crystal TV drive circuit characterized in that it is constructed by a circuit that generates an AC drive signal for a liquid crystal TV from an output or a frequency-divided output.