KR200370958Y1 - Adaptive white peak limit circuit - Google Patents

Abstract

The adaptive back peak compression circuit is for suppressing blooming and improving focus when the gain of the CRT driver is increased to increase the white gradation of the image signal. The circuit of the present invention includes a pulse detector for detecting a minute pulse signal such as a white character in a video signal caught by a CRT driver, an amplifier for amplifying the detected pulse signal to a predetermined size, and limiting the amplified pulse signal to a predetermined level And a limiter for greatly controlling the amplitude of the back peak portion, a signal feedback portion for feeding back the amplitude adjusted pulse signal to the CRT driving portion, and an amplitude compression portion for compressing only the amplitude of the back peak portion of the feedback input pulse signal. Therefore, the present invention provides the effect of suppressing blooming and improving focus by compressing peaks of only small pulse signals such as white characters without damaging white gradation and bright feeling of an image signal, thereby improving overall image quality.

Description

Adaptive white peak limit circuit

The present invention relates to an adaptive back peak compression circuit that can suppress a blooming phenomenon by compressing a white peak of a video signal corresponding to a narrow white character.

In general, the video signal is displayed as 140 IRE from the sync tip to the back peak, and the video signal 100 IRE, the synchronous signal 40 IRE, and the burst signal 40 IRE as a reference for the color signal based on the pedestal level of the synchronous. Consists of. The video signal is composed of a luminance signal Y and a chroma signal C. The luminance signal is related to the brightness of the screen, the amplitude of the chroma signal and the intensity of the color and the phase to the color, respectively.

Meanwhile, the CRT driving unit provided inside the television receiver receives a video signal processed as a color signal of red (R), green (G), and blue (B) configured as described above, and forms an image on the CRT based on this. Do this. The CRT driving unit also increases the gain of the R, G, and B signals, thereby increasing the whiteness of the image formed on the CRT and making it whiter.

However, in the image formed on the CRT, white narrow characters may appear together in the form of subtitles. In this case, the fine back peak corresponding to the character is included in the video signal, and when the gain is increased in the CRT driving unit, the back peak portion is also increased and saturated, so that the outline of the character appearing on the CRT is not clearly seen. There was a problem of blooming.

Therefore, the object of the present invention is to adaptively compress only the fine back peak portion included in the video signal in order to solve the above-mentioned point, suppressing the blooming without compromising the brightness, and thus reducing the focus of the white characters. To provide an adaptive back-peak compression circuit to improve the

1 is a block diagram showing an adaptive back peak compression circuit according to a preferred embodiment of the present invention,

FIG. 2 is a waveform diagram illustrating the operation of the circuit of FIG. 1. FIG.

<Description of the symbols for the main parts of the drawings>

11: CRT drive unit 12: CRT

13 pulse detection unit 14 amplification unit

15: signal return unit 16: limiter

17: amplitude compression unit

In order to achieve the above object, the adaptive back peak compression circuit of the present invention is a television receiver having a CRT driving unit for driving control of a CRT based on red (R), green (G), and blue (B) signals. A pulse detector for detecting a back level pulse signal of the R, G, and B signals, an amplifier for amplifying the detected pulse signal to a predetermined size, and limiting the amplified pulse signal to a predetermined level to obtain a back peak portion. A limiter for greatly adjusting the amplitude, a signal feedback unit for returning the amplitude-adjusted pulse signal to the CRT driver, and an amplitude compression unit for compressing only the amplitude of the back peak portion of the feedback input pulse signal to lower the gain of the CRT driver; Include.

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

1 shows a schematic diagram of an adaptive back peak compression circuit according to the present invention. The circuit shown in FIG. 1 includes a CRT driver 11 for driving the CRT 12 based on R, G, and B signals. In the present embodiment, only the R signal is illustrated, and the CRT driver 11 includes a transistor Q ₁ configured to receive the R signal as a base input and drive the CRT 12. The circuit of FIG. 1 also includes a pulse detector 13 for detecting fine pulse signals corresponding to white characters, and an amplifier 14 for amplifying the detected pulse signals to a predetermined size. The pulse detector 13 includes a transistor Q ₃ connected to the emitter of the transistor Q ₁ provided in the CRT driver 11 and a coil connected between the collector and the ground of the transistor Q ₃ . L). The amplifier 14 is composed of a transistor Q ₄ having a base connected between the collector of the transistor Q ₃ and the coil L provided in the pulse detector 13. On the other hand, the circuit of Figure 1 limits the amplified pulse signal to a predetermined level to limit the amplitude of the back peak portion 16, the signal feedback for feeding back the amplitude-adjusted pulse signal to the CRT drive unit 12 side (feedback) And an amplitude compression unit 17 for compressing only the amplitude of the back peak portion of the feedback signal. Signal feedback unit 15 base amplification section 14, a transistor (Q _4), the collector and connected to the transistor (Q ₅₎ and the base is connected to the other between the collector and ground of the transistor (Q ₅₎ of the provided in the It consists of a transistor (Q _6). The limiter 16 includes a transistor Q ₇ connected to the emitter of the transistor Q _{5 in} which the emitter is provided in the signal return unit 15 and a voltage divider R ₁ connected to the base of the transistor Q ₇ . , R ₂ ). The amplitude compression unit 17 has a base connected to the emitter of the transistor Q ₆ provided in the signal return unit 15, and the emitter connected to the base of the transistor Q ₃ provided in the pulse detection unit 13. And a transistor Q ₂ . An operation of the adaptive back peak compression circuit of FIG. 1 having such a configuration will be described in detail with reference to FIG. 2.

During TV ON driving, the CRT driving unit 11 which receives the R, G, and B signals and drives the CRT 12 based on the received R, G, and B signals has a narrow back peak generated in the R signal as shown in FIG. 2A. In this case, the base potential of the transistor Q ₁ provided therein is raised, which is applied to the pulse detector 13. As a result, the emitter potential of the transistor Q ₃ provided in the pulse detector 13 becomes high, thereby causing the collector potential to rise momentarily. Therefore, the current flowing through the coil L increases, and the voltage between the coil L increases, thereby detecting a fine pulse signal such as a white character. As shown in FIG. 2A, when the R signal including the back peak is applied to the CRT driver 11 as it is, the back peak portion is saturated as shown in FIG. 2B. To prevent this, the voltage across the coil L is applied to the base of the transistor Q ₄ provided in the amplifier 14. The transistor Q ₄ of the amplifier 14 amplifies the pulse signal applied to the base to a predetermined magnitude, and then applies it to the base of the transistor Q ₅ provided in the signal feedback unit 15. At this time, the limiter 16 sets the limit level according to the driving voltage, that is, the resistance values of the divided resistors R ₁ and R ₂ for dividing 9V. The transistor Q ₇ provided in the limiter 16 receives the limit level voltage set by the voltage divider R ₁ and R ₂ as a base, and the emitter of the transistor Q ₅ provided in the signal return unit 15 is provided. If the drive voltage applied to the emitter is greater than or equal to the limit level, it is turned on, and if it is less than or equal to the limit level, it is turned off to limit the level of the pulse signal applied to the signal feedback unit 15, thereby greatly controlling the amplitude of the back peak portion. The transistor Q ₅ provided in the signal feedback unit 15 limits the amplified pulse signal applied to the base according to the limit level of the limiter 16 applied to the emitter and applies it to the base of the transistor Q ₆ . Transistor Q ₆ is for the buffer, which is limited to a constant level applied to the base, and returns a pulse signal whose amplitude is largely adjusted to the amplitude compression unit 17 through the output terminal drawn from the emitter. The returned pulse signal causes the transistor Q ₂ in the amplitude compression unit 17 to be “on”, and as a result, a predetermined level is superimposed on the base of the transistor Q _{3 in the} pulse detection unit 13, thereby providing a CRT. The emitter potential of the transistor Q ₁ provided inside the driver 11 is increased. As a result, as shown in FIG. 2C, the signal compressed in the amplitude of the back peak portion is input to the base of the transistor Q ₁ , thereby reducing the gain of the CRT 12, thereby preventing the blooming shape appearing on the screen.

As described above, the adaptive back peak compression circuit of the present invention has narrow white characters, and when the back peak signal is mixed in the R, G, and B signals, the gain of the R, G, and B signals is adjusted. By compressing only the amplitude of the back peak part, it suppresses the blooming and improves the focus, thereby improving the overall image quality.

Claims (6)

In a television receiver having a CRT driving unit for driving control of a CRT based on red (R), green (G), and blue (B) signals, A pulse detector detecting a back level pulse signal of the R, G, and B signals; An amplifier for amplifying the detected pulse signal to a predetermined size; A voltage dividing resistor for dividing the driving voltage according to the resistance value to set the limit level, and a transistor which is in an " ON / OFF " state according to the set limit level; A limiter to limit the amplitude of the back peak portion to a large limit; A signal feedback unit for returning the amplitude adjusted pulse signal to the CRT driving unit; And And an amplitude compression unit for compressing only the amplitude of the back peak portion of the feedback input pulse signal to lower the gain of the CRT driving unit. The method of claim 1, wherein the pulse detection unit A transistor in which the emitter potential is increased when the fine back peak is generated in the R, G, and B signals, thereby causing the collector potential to rise momentarily; And And a coil connected between the collector and the ground of the transistor, the current flowing as the collector potential of the transistor increases to increase the voltage between both ends. The method of claim 2, wherein the amplifying unit is a "ON (ON) / OFF (OFF)" state according to the voltage across the coil is provided with a transistor for amplifying and outputting a pulse signal detected by a predetermined magnitude Adaptive back peak compression circuit. delete The method of claim 3, wherein the signal return unit A transistor having a emitter connected in common to an emitter of a transistor provided in the limiter and outputting the amplified pulse signal applied to a base at a predetermined limit level; And And a transistor having a base connected to an output terminal drawn out to a collector of the transistor and returning a limited pulse signal to the amplitude compression unit. The transistor of claim 5, wherein the amplitude compression unit is turned “ON” according to the feedback pulse signal applied to the base, and is overlapped with the transistor base of the pulse detector to reduce the gain of the CRT driver. Adaptive back peak compression circuit, characterized in that.