KR100206322B1 - Luminance control method and circuit for lcd projection tv - Google Patents

Abstract

In the brightness adjustment circuit of the TV receiver of the display device using an LCD, the signal portion and the retrace portion of the video signal are appropriately selected so that the brightness voltage is superimposed on the video signal during the retrace period, and the horizontal blanking period ( By changing the brightness signal applied during the retrace period, the pedestal level is changed so that the pedestal level of the signal is changed by using it as a reference level when clamping at the rear stage.

Description

Brightness Control Circuit of LCD Projection Television Receiver

1 is a circuit diagram according to an embodiment of the present invention.

2 is an operational waveform diagram of FIG.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brightness adjustment circuit of a liquid crystal projection television receiver. In particular, the horizontal blanking portion is suitably used as a pedestal level so that the brightness can be easily configured, and at the same time, it is unnecessary for a display element having a driver such as an LCD. A brightness adjustment circuit of a liquid crystal projection television receiver for removing the blanking portion.

In the liquid crystal projection receiver, a signal is applied to the negative (-) and positive (+) terminals differently using an operational amplifier (i.e., if the negative terminal is an image signal, the control voltage (brightness adjustment voltage) is applied to the positive terminal; On the other hand, the brightness has been adjusted by supplying them in opposite directions, while the blanking process by the horizontal synchronous signal has been clipped using a Zener diode, etc. However, unnecessary horizontal blacking is unnecessary in a display device such as a conventional LCD. There was a problem when this occurred.

Accordingly, an object of the present invention is to make the horizontal blanking part easy to adjust the brightness by appropriate use of the pedestal level, and at the same time serves to remove the unnecessary horizontal blanking part in the display device of the drive, such as the LCD, A circuit for easily converting a signal into an image signal waveform required for signal processing at a later stage is provided.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a circuit diagram according to the present invention, which is obtained by using the color signal demodulation and the primary color signals R, G, and B signals output from the matrix unit 100 as the luminance signal Y and the color signal C. The invention consists of the following circuits.

A color signal demodulation and matrix unit 100 for generating an RGB primary color signal from the luminance signal Y and the color signal C, and R, G, B primary color signals and brightness control signals of the color signal demodulation and matrix unit 100; A selector 200 for selecting (DC variable voltage) by a horizontal blanking control signal, and inputting a signal in a state where the horizontal blanking period is corrected to reproduce the desired signal by DC with a horizontal clamp pulse signal and then LCD characteristics. LCD interface 300 for generating a signal suitable for gamma correction and alternating current driving, and an LCD module 400 for displaying an image signal appropriately by a timing clock signal as a display device by the LCD module. And a multivibrator 500 for shaping the horizontal synchronization signal generated by the color signal demodulation and matrix unit 100 into a waveform of an appropriate horizontal blanking signal.

FIG. 2 is an operation timing diagram of FIG. 1, FIG. 2A is an output waveform of the color signal demodulation and matrix unit 100, where T1 is a blanking portion and T2 is a blanking period.

FIG. 2B is an output waveform of the selector 200, FIG. 2C is an example of horizontal blanking generated by the multivibrator 500, and FIG. 2 is an example of input of the clamp pulse stage CP.

Therefore, a specific embodiment of the present invention will be described in detail with reference to FIGS. 1 to 2, and the R, G, and B primary colors signals output from the color demodulation and matrix unit 100 as shown in FIG. The portion occupied by the horizontal blanking portion, as shown in Fig. 2c, is considerably large. In order to make such a signal as shown in FIG. 2B of FIG. 2B, a brightness adjustment DC voltage DC output from a microcomputer (not shown) is supplied to one input of the multiplexer selector 200. As for the image signal and the brightness voltage as described above, when the horizontal blanking signal of FIG. 2c of the switching control signal generated by the multivibrator 500 is low, the image signal is selected, and when the high level, the brightness signal is selected, the second signal The signal is generated as shown in FIG. 2B of FIG. In addition, the pedestal level 201 (reference level) of the signal of FIG. 2b changes according to the brightness voltage. When the brightness voltage increases, the pedestal level 201 also increases, and conversely, when the brightness voltage decreases, the pedestal level 201. ) Is also reduced. The pedestal level 201 acts as a reference level to process the image signal during the C-coupling and post-clamping process at the LCD interface 300 at the rear stage. As described above, the DC level of the entire signal is changed according to the change of the pedestal level 201, and the brightness of the screen is changed by the amount of change of the brightness voltage. On the other hand, the R, G, B primary color signals supplied to the LCD interface unit 300 gamma correction according to the LCD characteristics, inverts the signals at regular intervals, and then amplifies the signals to a desired size to supply the signals to the LCD module 400. Do it.

As described above, in the case of using a color demodulation IC developed for an existing CRT TV in a display device using an LCD and when a signal is coupled to a capacitor, brightness is adjusted. In the case of demodulating the B primary color signal, the blanking part is clamped at the rear end using an S / W element to change the horizontal blanking part of the output signal (H return period in case of CRT TV) to a constant DC voltage (variable). It is advantageous to use the pedestal level as a pedestal level (ie, black level) so that effects such as brightness adjustment are the same.

Claims (1)

In the brightness adjustment circuit of the TV receiver using the LCD, a color signal demodulation and matrix unit 100 for generating R, G, and B primary color signals from the color signal C and the luminance signal Y of the input image of the TV receiver. And a selection unit 200 for selectively selecting the R, G, and B primary color signals and the brightness control signal (DC variable voltage) of the color signal demodulation and matrix unit 100 by a horizontal blanking control signal, and the horizontal LCD interface unit 300 for generating a signal suitable for LCD characteristics, performing gamma correction and AC driving after regenerating DC with a desired signal by a horizontal clamp pulse signal as a signal having a blanking period corrected therein, and the LCD module LCD display module 400 that properly displays an image signal by a timing clock signal, and a horizontal synchronization signal generated by the color signal demodulation and matrix unit 100 by shaping a waveform into an appropriate horizontal blanking signal. And a brightness control circuit of the liquid crystal projection television receiver.