KR200203123Y1 - Circuit of blooming prevent and image correction in a color television - Google Patents

Abstract

The present invention relates to a focal blur prevention and image quality correction circuit of a color television. In the related art, when the ABL operation does not immediately operate when the power is turned on, it prevents a certain degree of saturation with an arbitrary control voltage. Although the random control voltage at power-on is based on the contrast level of the actual displayed image, the video saturation and focus blur are controlled by clamping the excessive white peak signal below a certain level unconditionally regardless of the image condition. Rather, there was a problem that caused the image quality deterioration of the entire screen.

Therefore, in order to solve the above problems, the present invention constitutes a focal blur prevention and image quality correction circuit of a color television that detects APL detection of a color image display output device and transient characteristics above a predetermined level of a luminance signal. Even in the signal state caused by excessive input signal or other factors generated in the operating state, the output saturation of the R, G, B for the video input is suppressed to prevent the screen blurring phenomenon, and also to prevent the deterioration of the image quality of the entire screen on the bright screen. The APL voltage is detected according to the condition of the received video signal, the presence or absence of a caption signal or the white peak signal is determined, and the beam current of the ABCL and the limit of the white peak are controlled to improve the image quality of the image.

Description

Focus blur prevention and image quality correction circuit for color television

The present invention relates to a color television, and in particular, a red color of an image input after detecting an excessive characteristic of a certain level or more of a luminance signal even in a signal state caused by an excessive input signal or other factors generated in a normal operation state of a receiver. (R), green (G), and blue (B) suppress the saturation of the output signal to prevent the blurring phenomenon of the screen, and according to the condition of the received video signal After detecting voltage and judging the presence of closed caption signal or white peak signal, the image quality is corrected by controlling beam current and white peak limit of ABCL (Auto Brightness Contrast Limit). A focus blur prevention and image quality correction circuit of a color television to be described.

The conventional screen focal blur prevention circuit of the color television operates at the power-on of the color television to prevent excessive instantaneous contrast control voltage, thereby providing a blooming cancellation circuit which can prevent blooming.

According to this, in a color television for supplying a contrast control voltage from a microcomputer to a deflection / chromatic IC through a contrast control voltage supply line L, the contrast control voltage supply line L is coupled to the contrast control voltage supply line L. A zener diode (ZD) which is turned on when the voltage level exceeds its predetermined voltage level,

And a transistor (Q) coupled between the output of the zener diode (ZD) and the contrast control voltage supply line (L) to conduct when conducting the zener diode (ZD) to bypass the contrast control voltage to ground. A blooming removal circuit was provided.

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

In Fig. 1, as L is shown as a contrast control voltage supply line, the contrast control voltage is supplied from the microcomputer to the deflection / chromatic IC (not shown) through this contrast control voltage supply line L. In FIG.

During normal operation of the automatic beam limiter (ABL) (not shown), the contrast control front supply line L automatically maintains the constant control voltage at a constant level by the automatic beam limiter.

However, since the automatic beam limiter (ABL) at the time of power-on of the color television does not operate immediately due to its characteristics, the voltage from the B ⁺ line connected to the contrast control voltage supply line (L) is not supplied by the microcomputer. It will be supplied to the deflection / chromatic IC with superimposed on the contrast control voltage of.

However, in such a situation, the blooming cancellation circuit 10 is operated to prevent the excessive contrast control voltage, which is superimposed on the voltage of the B ⁺ line, from being supplied to the deflection / chromatic IC.

The configuration and operation of the blooming removal circuit 10 will be described later.

The blooming removal circuit 10 includes a zener diode (ZD) and an NPN type transistor (Q). The cathode of the zener diode (ZD) is coupled to the contrast control voltage supply line (L).

An anode of the zener diode ZD is connected to the base of the transistor Q.

On the other hand, the collector of the transistor Q is connected to the contrast control voltage supply line L. In this configuration, the zener voltage of the zener diode ZD is set slightly higher than the normal voltage level of the contrast control voltage supply line L (for example, a value of about 1V to 1.5V higher).

The operation of the conventional blooming cancellation circuit having the above-described configuration will be described.

First, in the state where the automatic beam limiter operates normally, the voltage of the contrast control voltage supply line L has a level lower than the preset voltage of the zener diode ZD, and thus the transistor Q of the transistor Q is connected through the zener diode ZD. No signal is applied to the base so that the transistor Q remains in a non-conducting state. Thus, the contrast control voltage supplied to the deflection / chromatic IC is not affected.

On the other hand, the automatic beam limiter ABL does not operate normally at the power-on of color television, so that the voltage of the contrast control voltage supply line L is excessive in the state where B ⁺ line voltage is superimposed. To exceed the zener voltage level of the zener diode ZD. Therefore, the transistor Q is switched from the non-conductive state to the conducting state according to a signal applied to the base of the transistor Q through the zener diode ZD.

As a result, an abnormally high transient voltage on the contrast control voltage supply line L is bypassed to ground through the collector-emitter path of the transistor Q in the conducting state and is not applied to the deflection / chromatic IC.

As described above, in the prior art, when the power-on automatic beam limiter of a color television is not operating normally, an abnormally high voltage generated on the contrast control voltage supply line L due to a certain factor is a blooming cancellation circuit. By using (10) to bypass the grounding, the saturation of the red (R), green (G), and blue (B) color signals was prevented to eliminate the blooming phenomenon.

That is, when the auto beam limiter (ABL) operation does not immediately operate when the power is turned on, it prevents the saturation to some extent with an arbitrary control voltage, which is an arbitrary contrast control voltage when the power of the color television image is turned on. As the reference is based on the contrast level of the actual displayed image, it controls the image saturation and focus blurring by clamping the excessive white peak signal to a certain level or lower regardless of the image condition. There was a problem causing.

Accordingly, the present invention has been made to solve such a problem, and constitutes a focal blur prevention and image quality correction circuit of color televisions that detect APL of a color image display output device and transient characteristics of a predetermined level or higher of a luminance signal. Focusing of the screen by suppressing the output saturation of red (R), green (G), and blue (B) for video input even in signal state due to excessive input signal or other factors generated in the normal operation state of the receiver The purpose of the present invention is to prevent a phenomenon and to prevent deterioration of image quality of the entire screen in a bright screen.

Another purpose is to detect the APL voltage according to the condition of the received video signal, determine whether there is a closed caption signal or a white peak signal, and then beam current of the ABCL (Auto Brightness Contrast Limit) beam. This is to improve the image quality of the image by controlling the limit of and white peak.

1 is a block diagram showing the configuration of a conventional focal blur prevention circuit.

Figure 2 is a block diagram showing the configuration of the focal blur prevention and image quality correction circuit of the present invention color television.

3 is a circuit diagram showing the configuration of the focal blur prevention and image quality correction circuit of the inventive color television.

Focus blur prevention and image quality correction circuit of the present invention color television for achieving the above object is as shown in Figs.

An APL detector (10) for detecting an average video level of the video signal;

An APL comparator 20 for comparing the height of the average image level detected by the APL detector 10 with a reference voltage Vref set to the APL voltage at the ABCL operation point and outputting a high or low level comparison signal; ;

A transient signal detection unit 30 for detecting an excessive image signal Tip component and a white peak signal that are greater than or equal to a reference peak value in the luminance signal Y input according to the condition of the image signal;

Image condition discrimination for determining an image condition that may cause focal blurring according to a high or low level comparison signal compared and output by the APL comparator 20 and a white peak signal detected by the transient signal detector 30. Section 40;

An ABL limit controller 50 for controlling the beam current of the ABL unit 100 flowing to the flyback transformer (FBT) according to the high or low level comparison signal outputted by the APL comparator 20;

According to the peak value of the luminance signal Y detected by the transient signal detection unit 30 and the level of the excessive white peak signal and the APL of the image, the output of the RGB output unit 200 is output to the CPT. A white peak limit controller 60 for limiting the red, green, and blue signals B to a constant maximum value to prevent focal blurring of the screen due to saturation of the R, G, and B output signals; Characterized in that consisting of.

Hereinafter, reference numerals R11 to R34 denote resistors, C11 to C15 denote capacitors, D11 to D16 diodes, Q11 to Q21 transistors, and ZD11 denotes zener diodes.

The operation of the focal blur prevention and image quality correction circuit of the inventive color television configured as described above will be described with reference to FIGS. 2 and 3.

First, when the APL detector 10 detects an average video level height of an image signal as a DC voltage and outputs the DC voltage to the APL comparator 20, the APL comparator 10 detects and inputs an average video level height DC. The voltage is compared with the reference voltage Vref set to the APL voltage at the ABCL operation point, and then a high or low level comparison signal is output to the image condition discriminator 40 and the ABL limit controller 50.

The ABL limit controller 50 controls the beam current of the ABL unit 100 flowing to the flyback transformer FBT according to the high or low level of the input comparison signal.

That is, in a bright image condition, the APL comparator 20 outputs a high level comparison signal to the ABL limit controller 50. Therefore, in the transistors Q11 and Q12 included in the ABL limit controller 50, The on-state operation is performed according to the high level comparison signal applied to the base to limit the beam current of the ABL unit 100 flowing to the flyback transformer FBT.

In addition, in a dark image condition, the APL comparator 20 outputs a low level comparison signal to the ABL limit controller 50. Therefore, in the transistors Q11 and Q12 included in the ABL limit controller 50, The off-state operation is performed according to the low level comparison signal applied to the base so that the beam current flows to the flyback transformer FBT only through the resistor R17 included in the ABL unit 100.

On the other hand, the transient signal detection unit 30 detects an excessive signal tip component of more than a reference peak value and a white peak signal of a predetermined level from the luminance signal (Y) input according to the condition of the image signal, and then the white peak limit controller Output to (60).

That is, when the luminance signal Y is input according to the condition of the image signal, the input luminance signal Y is a buffer function transistor Q16 and a resistor R19 (R20) included in the transient signal detector 30. Since only a voltage greater than the zener diode ZD11 is biased to the transistor Q17 after being biased by the transistor, the image signal tip portion of the image signal tip passes through the transistor Q17 (Q18) formed of a level shift. D12) and the capacitor C14 are detected as DC voltages.

At this time, when there is no white peak signal, the voltage between both ends of the capacitor C14 becomes zero (0). When the white peak signal is large and the voltage between both ends of the capacitor C14 increases, the white peak limit control unit 60 becomes high. As input to, the white peak remote control unit 60 outputs the CPT according to the peak value of the luminance signal Y detected by the transient signal detection unit 30 and the level of the excessive white peak signal and the APL low of the image. By limiting the red (R), green (G), and blue signals (B) of the RGB output unit 200 to a constant maximum value, focus blurring of the screen due to saturation of the R, G, and B output signals is prevented.

In other words, a transistor Q21 and a diode D13 and a differential amplifier Q19 and Q20 which are included in the white peak limit controller 60 and constitute a constant current source according to the magnitude of the voltage across the capacitor C14. As a result, the voltage level applied to the collector of the transistor Q19 is changed, so that the red (R), green (G), and blue signals (B) of the RGB output unit 200 output to the CPT are diodes (D14, D15). D16) is limited to a certain maximum value to prevent the screen from blurring due to the saturation of the R, G, and B output signals.

Here, the white peak limit controller 60 does not always operate, but operates only when a condition in which focus blur occurs, that is, when the APL of the image is low and there is an excessive white peak signal.

That is, the image condition discrimination unit 40 focuses on the high or low level comparison signal output by the APL comparator 20 and the predetermined level of the white peak signal detected by the transient signal detector 30. After determining an image condition in which blur can occur, the operation of the white peak limit control unit 60 is controlled.

In this case, the image condition determined by the image condition determining unit 40 is classified into a signal having a large APL or a small signal based on the ABCL operating point, and distinguishes the presence or absence of a white peak signal of a predetermined level or more.

Signal with large APL and white peak,

Signal with small APL and white peak,

Signal with large APL and no white peak,

Signal with small APL and no white peak.

Is distinguished by.

Therefore, based on the image condition, if it is a dark image condition, the ABL comparator 20 outputs a low level comparison signal to the image condition determiner 40, and the image condition determiner 40. In the transistor Q13 included therein, the low level comparison signal is inverted to a high level and then applied to one terminal of the end gate 300.

When the white peak signal of a predetermined level is detected by the transient signal detector 30, the detected white peak signal of the predetermined level is included in the diode D11 and the capacitor C12 included in the image condition discriminator 40. By inputting the high DC voltage to the other terminal of the end gate 300, the high output signal is applied to the base of the transistor Q14 in the end gate 300.

Thereafter, the transistors Q14 and Q15 included in the image condition determining unit 40 are turned on according to the high output signal to which the transistors Q14 and Q15 are applied, thereby providing voltages at both ends of the capacitor C14 included in the transient signal detection unit 30. Since the value is set to zero, the white peak limit control unit 60 outputs the red (R) of the RGB output unit 200 outputted as CPT with the voltage set by the resistors R32 and R33 configured therein. ), The green (G) and blue signals (B) are limited to prevent the screen from blurring due to the saturation of the R, G, and B output signals.

As described above, the present invention constitutes a focal blur prevention and image quality correction circuit of a color television that detects APL of a color image display output device and a transient characteristic of a predetermined level or higher of a luminance signal, and thus is generated in a normal operation state of the receiver. Even in the signal state caused by excessive input signal or other factors, it suppresses the output saturation of red (R), green (G), and blue (B) for video input, and prevents the screen blooming phenomenon and bright screen To prevent deterioration of the quality of the entire screen, detect the APL voltage according to the condition of the received video signal, determine the presence of the closed caption signal or the white peak signal, and control the beam current of the ABCL and the limit of the white peak to improve the image quality. There is an effect to improve.

Claims (1)

An APL detector for detecting an average video level of the video signal; An APL comparator for outputting a comparison signal by comparing the detected average image level with a reference voltage at a predetermined ABCL operation point; A transient signal detector for detecting an excessive video signal tip component and a white peak signal above a reference peak value from a luminance signal input according to a condition of the video signal; An image condition discrimination unit for discriminating an image condition in which focal blurring may occur according to a comparison signal compared and output by an APL comparison unit and a white peak signal detected by the transient signal detection unit; An ABL limit controller for controlling the beam current of the ABL unit flowing to the flyback transformer according to the comparison signal output by the APL comparison unit; The red (R), green (G), and blue signals (B) of the RGB output unit are output as CPT according to the peak value of the luminance signal detected by the transient signal detection unit, the excessive white peak signal level, and the APL low of the image. A white peak limit control unit configured to limit the maximum value to prevent focus blurring of the screen due to saturation of the R, G, and B output signals; Focus blur prevention and image quality correction circuit of the color television, characterized in that consisting of.