KR100455199B1 - Peaking circuit for television set - Google Patents

Abstract

The present invention relates to a technique for improving the sharpness of the image quality by differentially applying the peaking gain to the high / low level of the luminance signal in the digital TV. This invention comprises a resonator (31) for separating and detecting peaking components from an input luminance signal; An amplifier (32) for amplifying the picking signal input from the resonator (31) to a predetermined level; A clipper (33) for receiving the output signal of the amplifier (32) to clip the gain of the high level picking signal to be reduced and the gain of the low level picking signal to be relatively high; This is achieved by a synthesizer 34 which combines the output signal of the clipper 33 with the original luminance signal and outputs the picked luminance signal.

Description

Peaking circuit of TV receiver {PEAKING CIRCUIT FOR TELEVISION SET}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal processing technique for improving the sharpness of image quality in a digital TV, and more particularly, to a peaking circuit of a television receiver, which is capable of differentially applying a peaking gain to a high / low level of a luminance signal.

1 is a peaking circuit diagram according to the prior art, as shown in FIG. ) Is connected to the non-inverting input terminal of the operational amplifier (OA) through the resistor (R3), and the capacitor (C), coil (L), and resistor (R2) are connected in series between its inverting input terminal and the ground terminal. The output signal of the operational amplifier (OA) ) Is connected to the non-inverting input terminal through the resistor (R1), and will be described with reference to Figure 2 attached to the operation thereof as follows.

Gain of Non-Inverting Operational Amplifier (OA) Feedback impedance Termination Impedance of Input and Reverse Input Terminals Of Is determined. That is, the gain of the operational amplifier (OA) Is expressed by the following [Equation 1], the resonant frequency Is represented by [Equation 2].

Resonant frequency Becomes the peaking frequency soon. Gain of Peaking Component at Resonance Frequency of Equation 1 Is expressed by Equation 3 below.

As a result, the original luminance signal to have maximum gain near the peaking frequency Luminance signal in the form of peaking component applied to Is output.

In order to improve the peaking effect of the low level signal, the peaking gain must be increased along with the high level signal. To this end, if the peaking gain is continuously increased, a high frequency oscillation ("Oh") phenomenon as shown in FIG. 2B may appear on the screen. This means that the ringing component becomes larger due to an increase in the Q value of the resonant circuit, so that damping at an appropriate level is necessary. In this case, the bandwidth of the peaking frequency is increased and the gain component of most high frequencies is considerably higher, which increases the possibility of oscillation of the OA.

In addition, if the peaking gain is continuously increased as described above, the high-frequency signal around the high-level transient region is modulated by the overshoot or undershoot, so that the high-frequency signal is limited due to the limitation of the CALTI driving amplifier or the CIFity characteristics when the actual display is performed. The likelihood of saturation (Sw: White Saturation), (Sb: Black Saturation) is increased by the white or black signal as shown in FIG. 2B.

As described above, in the peaking circuit of the conventional television receiver, if the peaking gain is continuously increased to improve the peaking effect of the low level signal, a high frequency oscillation phenomenon occurs, and the high frequency signal around the high level transient region is modulated by the overshoot or undershoot. There was a problem that the high frequency signal is saturated by the white or black signal.

Accordingly, an object of the present invention is to provide a peaking circuit of a television receiver capable of sufficiently peaking to a low level signal by solving the high frequency signal oscillation noise and the saturation of the high frequency signal around the transient region of the high level signal when the peaking gain is continuously increased. In providing.

1 is a picking circuit diagram of a television receiver according to the prior art;

2A is a waveform diagram of an input luminance signal in FIG. 1;

Fig. 2B is a waveform diagram showing an abnormal phenomenon when the peaking gain is excessively set.

3 is a block diagram of a picking circuit of a television receiver according to the present invention;

(A)-(e) is a waveform diagram of each part of FIG.

Figure 5 is a detailed circuit diagram showing an embodiment of the picking circuit according to the present invention.

6A-6D are waveform diagrams of respective parts of FIG. 5.

*** Description of the symbols for the main parts of the drawings ***

31 resonator 32 amplifier

33: Clipper 34: Synthesizer

Fig. 3 is a block diagram of a picking circuit of a television receiver according to the present invention, and as shown therein, a resonator 31 for separately detecting a picking component from an input luminance signal; An amplifier (32) for amplifying the picking signal input from the resonator (31) to a predetermined level; A clipper (33) for receiving the output signal of the amplifier (32) to clip the gain of the high level picking signal to be reduced and the gain of the low level picking signal to be relatively high; A synthesizer 34 which synthesizes an output signal of the clipper 33 to the original luminance signal and outputs a picked luminance signal, with reference to FIGS. 4 to 6 attached to the operation of the present invention configured as described above. It will be described in detail as follows.

Input luminance signal ) Is provided on the one hand as an input of the synthesizer 34 at the output stage and on the other hand as an input of the resonator 31, which is a luminance signal ( ) Substantially includes the original peaking component as shown in Figure 4 (b) in the original luminance component as shown in Figure 4 (a). However, in the present invention, the peaking component is separated from the input terminal and then processed appropriately, and then the output component is synthesized with the luminance component.

To this end, the resonator 31 determines the peaking frequency and bandwidth of the peaking signal to be peaked, and includes the pure peaking signal as shown in FIG. ) Is separated and detected, which is input to the amplifier 32 of the next stage and amplified to a predetermined level as shown in FIG.

The amplifier 32 is a feedback amplifier whose phase characteristics can minimize frequency correlation, and the oscillation of the amplifier 32 (A: Gain, This occurs when the phase angle characteristic of the feedback coefficient does not satisfy the phase margin or gain margin. Thus, with A By designing an amplifier with a low frequency response, the high-frequency oscillation can be minimized by increasing the gain.

Output signal of the amplifier 32 as shown in FIG. ) Is input to the clipper 33 and clipped as shown in FIG. 4 (d). The clipper 33 is used to reduce the gain of the high level peaking signal and to relatively increase the gain of the low level peaking signal. To this end, the low-level and high-level peaking components are amplified by a uniform gain, and then a signal of a predetermined level or more is clipped to the clipper 33, thereby preventing the high-frequency signal near the transient region of the high-level signal from being saturated.

The original input luminance signal ( ) Is synthesized with the output signal of the clipper 33 by the synthesizer 34, and the luminance signal (P) is picked up therefrom as shown in FIG. ) Is output.

On the other hand, Figure 5 is a detailed circuit diagram showing an embodiment of the picking circuit of the present invention, the operation thereof will be described as follows.

The resonator 51 is composed of an RLC resonant circuit, and its resonant frequency Is expressed by Equation 4 below.

In addition, the resonance frequency The selectivity Q and bandwidth B, which are directly related to the bandwidth of, are expressed by Equations 5 and 6, respectively.

Experimental result, the resonant frequency Is 16 MHz, the Q value that minimizes the ringing component is 0.67 and the bandwidth B is found to be 24 MHz.

The picking signal extracted from the resonator 51 is input to the amplifier 52 of the next stage and amplified by about 18 times. Assuming that the bandwidth of the operational gain of the operational amplifier OA1 is sufficiently wider than the frequency of interest, Is expressed by Equation 7 below.

For your reference, Since is not a function of frequency, the phase angle variation with increasing gain can be ignored.

Among the amplified picking signals, a high level picking signal ( ) Is clipped at the clipper 53. Here, the clipping of the picking signal on the positive side is determined by the ratio of R8 / R9, and the clipping of the picking signal on the negative side is determined by the ratio of R11 / R10.

The original luminance signal O and the clipped peaking signal C are buffered through the first buffer BUF1 and the second buffer BUF2, respectively, and then input to the synthesizer 54. FIG. 6B shows the output signal of the operational amplifier OA1 in the amplifier 52, and FIG. 6C shows the signal clipped by the clipper 53. When the low / high level picking signals of the two signals are compared, the clipping effect is shown. You can check.

Original luminance signal ( ) And the picked signal ( ) Is synthesized as shown in [Equation 10] after the level is adjusted as shown in [Equation 8] and [Equation 9].

The synthesized signal is output as shown in FIG. 6D after the level is adjusted as shown in Equation 11 as needed. The low level peaking signal is sufficiently amplified and the high level peaking signal is clipped in luminance. You can see that it is superimposed on the signal.

As described in detail above, the present invention solves the saturation problem of the high frequency signal oscillation noise and the high frequency signal around the transient region of the high level signal when the peaking gain is continuously increased, and applies the peaking to the low level signal, thereby providing digital TV or LCD projection. The sharpness of image quality is improved in TVs.

Claims (2)

A resonator for separately detecting a peaking component from an input luminance signal; An amplifier for amplifying the peaking signal to a predetermined level and minimizing high frequency oscillation due to an increase in gain; A clipper for clipping such that the high level gain is reduced and the low level gain is relatively high in the amplified peaking signal component; And a synthesizer for synthesizing the clipped signal with the input luminance signal and outputting the picked luminance signal. 2. The picking circuit of a television receiver according to claim 1, further comprising a first buffer and a second buffer for buffering and amplifying an input luminance signal and an output signal of the clipper, respectively, and transferring them to the clipper.