KR930011137B1 - Automatic tint control circuit and method - Google Patents

Abstract

he tint circuit automatically adjusts the bust signal in the composite video signal and the phase of the subcarrier. The circuit comprises: a synchronizing separator (1) separating the horizontal synchronizing signal from the composite video signal; a delay circuit (13) generating burst flag signal from the horizontal synchronizing signal; a CPU (14) controlling the circuit.

Description

Automatic Tint Control Circuit and Its Method

1 is a composite video signal demodulation circuit in a typical television circuit.

2 is an automatic tint adjustment circuit diagram according to the present invention.

3 is an input and output waveform diagram of the first microcomputer.

4 is a flowchart for implementing an automatic tint adjustment method according to the present invention.

* Explanation of symbols for main parts of the drawings

1: A / D converter 2: Y / C separator

3: Automatic Color Control Unit (ACC) 4: Bandpass Filter (BPF)

5: Automatic Phase Controller (APC) 6: Voltage Controlled Oscillator (VCO)

7: Low pass filter (LPF) 8: A / D converter

9: first delay unit 10: demodulator multiplier

11: D / A converter 12: Sync separation part

13: second delay unit 14: micom

15: smoothing part 16: the adder

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to digital color demodulation in televisions for digital video signal processing, and more particularly to automatic tint adjustment circuits that automatically adjust the burst by matching the burst signal of the composite video signal with the phase of the subcarrier. And to a method thereof.

FIG. 1 is a circuit diagram for performing complex video signal demodulation in a general television circuit. A composite video signal is input to an A / D converter 1 for converting an analog signal into a digital signal, converted into a digital signal, and then converted into a luminance signal Y. And the color signal C are inputted to the Y / C separation unit 2 separating the color signal C.

The color signal C from the Y / C separator 2 becomes a color signal of a predetermined level in the automatic color control (ACC) 3 and is input to the multiplier 10 for demodulation.

On the other hand, the composite video signal passes only the color signal through the band pass filter (4) of 3.58MHZ so that the automatic phase controller (APC) 5 and the voltage controlled oscillator (VCO) 6 can be connected. Subsequently, a subcarrier signal whose phase coincides with the burst signal is generated. The signal is input to the low pass filter 7 to remove the noise and then converted into a digital signal in the A / D converter 8 which converts the analog signal into a digital signal.

Then, it is inputted to the demodulation multiplier 10 via a first delay unit 9 for preventing phase shift due to a path difference from the luminance signal Y, and demodulated as a color difference signal RY, BY. The A converter 11 converts the analog signal into output.

The phases of the two signals input to the demodulator multiplier 10 must be exactly matched, but the phases are not exactly matched because the transmission paths of the video signal and the subcarrier are different, so the outputs of the color difference signals RY and BY are twisted. It is displaced. To adjust this, the time constant was adjusted by varying the value of the resistor or capacitor in the automatic phase controller, but it was also difficult to accurately match, and the value was different for each set, and the phase was shifted due to drift or component degradation due to temperature change. There was a problem that can not watch a good screen change.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and an object of the present invention is to input a demodulated value during a burst period of a video signal into a microcomputer to detect a phase difference between the video signal and a subcarrier to generate a DC value of a voltage controlled oscillator that oscillates a subcarrier. It is an object of the present invention to provide an automatic tint adjustment circuit and a method for controlling a phase using a PWM port so that a phase of a burst signal and a subcarrier signal always match.

In order to achieve the above object, a feature of the present invention is a subcarrier A / D conversion type digital television circuit that multiplies a composite video signal by a signal obtained by A / D conversion to perform horizontal demodulation on a composite video signal. A second delay unit connected to the synchronous separation unit for generating a burst flag signal from a horizontal synchronous signal, a switch for applying a demodulated signal only to the burst flag period to the rear end, the delay unit and the switch; A microcomputer for controlling the system connected to the microcomputer, a smoothing unit for converting the signal of the output value controlled by the microcomputer to a direct current, the value multiplied by the burst signal and the subcarrier connected to the microcomputer, and a color signal of the composite video signal to the automatic phase controller. Automatic turn adjustment further comprises an adder for adding a signal through the signal and the smoothing unit through Is in the circuit.

Another feature of the present invention is a step of setting a multiplication value of the burst signal and the subcarrier after the composite video signal passes through each signal processing path as an initial value, and setting a variable for determining n times until the tint is maintained at its best. When the burst signal and the subcarrier phase coincide, the multiplication value of the burst signal subcarrier is controlled by the microcomputer and the multiplied value of the burst signal and subcarrier is increased by the microcomputer to find the output value. Performing a routine to determine whether the multiplication value of the burst signal and the subcarrier is increased or decreased, and after performing the routine, decrease the number of discrimination times by 1 and store n-1 in the variable. In order to check whether the phase of the subcarrier signal coincides, a step of determining whether the variable value is? If the value is not ＂ø＂, the value of the burst signal and the subcarrier multiplied is the maximum. The value of the burst signal subcarrier multiplied is multiplied to find the controlled value. A routine for determining whether or not a value multiplied by a burst signal and a subcarrier signal is decreased while decreasing a value. When the variable value is ＂ø as a result of performing the step, the value multiplied by the burst signal and a subcarrier is controlled by the microcomputer. An automatic tint adjustment method is performed in which a burst signal and a subcarrier multiplied value are maximally multiplied and fixed to a controlled value and then terminated.

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

FIG. 2 shows another automatic tint adjustment circuit in this invention, in which some elements are added to a composite video signal demodulation circuit in a general television circuit as shown in FIG. 1. The configuration is as follows.

A second delay unit 13 for generating a burst flag (BF) signal from the horizontal synchronization signal is connected to the synchronization separation unit 12 that separates the horizontal synchronization signal from the composite video signal. Then, the D / A converter 11 and the second switch SW1 for applying a value obtained by multiplying the burst signal and the subcarrier by the demodulation multiplier 10 (hereinafter referred to as ＂Vi＂) only in the burst flag period. The microcomputer 14 for controlling the system is connected to the switch SW1 and the second delay unit 13, and the microcomputer 14 controls the Vi value (hereinafter, referred to as “Vo”). Output).

In addition, the microcomputer 14 is composed of a capacitor (C1) and a resistor (R1) to connect the smoothing unit 15 for converting the signal of the Vo value from the PWM port (a) of the microcomputer 14 to direct current An adder 16 is connected to the smoothing unit 15 and the automatic phase controller 5 to add a value controlled by the microcomputer 14 and color signals from the composite image signal, and are converted through respective signal processing passages. The Vi value is applied to the microcomputer 14.

4 is a flowchart for implementing an automatic tint adjustment method according to the present invention, in which a burst signal after a composite video signal passes through each signal processing path is set to a multiplication value of a subcarrier, that is, a Vi value, and the tint is best maintained. In other words, step S1 is performed to set a variable (hereinafter referred to as XX) for determining by performing n iterations until the phase of the burst signal coincides with the phase of the subcarrier. The routine L1 is performed to determine whether the Vi is increased or decreased while increasing the Vo value in order to find the Vo value when the coincidence, that is, the Vo value when Vi is the maximum value (hereinafter referred to as Vm). N is a natural number.

The routine L1 performs step S2 of increasing the value of Vo to find the value of Vm, and performs step S3 of inputting a value of increasing Vi by 1, where Vi is increased by 1. The value is compared with the magnitude of the Vi value, that is, if Vi + 1 ≧ Vi, the process returns to the step S2, and if Vi + 1 ≧ Vi, the step S4 proceeds to the next step.

After performing the routine L1, a step S5 of reducing the number of discriminations by ＂1＂ and storing ＂n-1＂ in the X value is performed and the X to check whether the phases of the burst signal and the subcarrier signal coincide. Step S6 is performed to determine whether the value is?

If Vo is Vm, it is when the phase of the burst signal and the subcarrier signal are coincident so it is no longer necessary to determine whether the variable value for determining n times, that is, the X value is?

In step S6, if L is not X =?, The routine L2 is performed to determine whether Vi is increased or decreased while decreasing the Vo value to find the Vm value.

The routine L2 performs a step S7 of decreasing the Vo value to find Vm, and performs a step S8 of increasing the value of Vi by 2 and increasing the value of Vi by 2 and increasing the value of Vi. Compare the magnitude of the value increased by 1 하며 and return to step S8 if Vi + 2 ≧ Vi + 1 and return to step S2 if Vi + 2 ≧ Vi + 1.

On the other hand, if X, which is a variable for repetitive determination in step S6, is? °, then Vo when the burst signal and the subcarrier signal are in phase is matched, that is, Vm is found. Step S10 is performed.

In the present invention constructed and implemented as described above, the demodulated value of the video signal is input to the microcomputer 14 only in the burst period. In addition, since the burst flag signal from the second delay unit 13 is also input to the microcomputer 14, the Vi value is read and the Vo is controlled only during this period. When the burst signal and the subcarrier signal are in phase, the product of these two signals is the maximum value. Has Figure 3 shows this. Here, the value of Vo = Vm is the maximum Vi, where the phase of the burst signal and the subcarrier coincide.

When the Vo output is varied in the microcomputer 14, the PWM output of the microcomputer 14 is changed into a direct current by the smoothing unit 15, which acts as a low pass filter of the resistor R1 and the condenser C1. In addition to the output of the automatic phase controller 5, the phase of the subcarrier in the voltage controlled generator changes. Accordingly, Vi changes through the above elements, and if the microcomputer 14 controls it again, the tint is adjusted.

The waveform diagram of FIG. 3 and the flowchart of FIG. 4 will be described in more detail. In the routine L1 of the flowchart, Vi is increased or decreased by increasing Vo, and in the routine L2, Vi is increased or decreased by decreasing Vo. After determining n times to prevent errors, the maximum value of Vo is fixed.

That is, to find Vo maximum value Vm, the following series of steps are performed. First, a value of a variable (X) for discriminating n times is set (S1) until Vi and the tint are maintained at the highest level (S1), and the routine L1 is performed.

The routine L1 increases S when the slope increase side a is in the waveform diagram of FIG. 3 (S2) and inputs a value where Vi increases by ＂1＂ (S3).

And, when Vi is compared with the value of the increase of ＂1＂ and the size of Vi (S4), if Vi + 1≥Vi, return to Vo increasing gas step (S2) to find the Vm value, and if Vi + 1≥Vi then Step will be performed. In step S5, the number of determinations is decreased by 1, so that n-1 is stored in X. In step S6, it is checked whether the X value is?

That is, if X = ø, since the burst signal and the subcarrier phase coincide, there is no need to repeat the process anymore, so the Vo value at this time becomes Vm and the Vo is fixed to Vm and terminated (S10). If the result is not X = ø, routine (L2) is executed to find the value of Vm.

Since the routine L2 is the slope reduction side in FIG. 3, it decreases Vo (S7) and inputs the value of Vi increased by ＂2＂ (S8) and the value of Vi increased by ＂2＂ and the Compare the magnitudes of the Vi + 1 values and return to step S8 if Vi + 2≥Vi + 1 and return to step S2 if Vi + 2≥Vi + 1 to find the Vm values. Repeat it.

That is, according to the present invention, the image signal of the output of the D / A converter 11 is horizontally separated by the synchronization separator 12, and a burst flag signal is generated by the second delay unit 13 to switch the switch SW1 to this signal. By controlling, the demodulated video signal is input to the microcomputer 14 only in the burst flag period, and Vo is output only in the burst flag period so that the phase of the burst signal of the subcarrier and the composite video signal can be adjusted.

As described above, in order to match the phase of the burst signal of the composite video signal with the demodulation subcarrier, the present invention uses a voltage controlled oscillator that detects the demodulation result in the burst period and creates a continuous subcarrier signal as the Vo output of the PWM port of the microcom. By controlling the phase of the burst signal and the subcarrier signal, the tint is automatically adjusted so that the screen state of the television becomes better.

Claims (2)

A digital television circuit of a subcarrier A / D conversion method for performing demodulation by multiplying a composite video signal by a signal obtained by A / D conversion of a composite video signal, comprising: a synchronization separator 12 for separating a horizontal synchronization signal from the composite video signal; A second delay unit 13 connected to the synchronization separation unit 12 to generate a burst flag signal BF from the horizontal synchronization signal, a switch SW1 for applying a demodulated signal to the rear end only in the burst flag period; The microcomputer 14 for controlling the system connected to the second delay unit 13 and the switch SW1 and the value of the microcomputer 14 connected to the microcomputer 14 and the burst signal and the subcarrier signal are controlled by the microcomputer 14 to control the microcom ( The smoothing unit 15 for converting the signal Vo outputted to the PWM port a of the 14 into a direct current, the color signal of the composite video signal is a signal through the automatic phase controller 5 and the smoothing unit 15 Adder 16 which adds a signal from Automatic tint adjustment circuit included. Setting the multiplier value (Vi) of the subcarrier of the burst signal after the composite video signal passes through each signal processing path to an initial value, and setting a variable (X) value for determining n times until the tint is maintained at the highest level (S1) and the Vo value (Vm) when the burst signal and the subcarrier are in phase while increasing the value Vo controlled by the microcomputer 14 of the multiplication value Vi of the burst signal and the subcarrier. A routine L1 is performed to determine whether a multiplication value of the burst signal and the subcarrier is increased or decreased, and after the routine L1 is performed, the number of determinations is decreased by ＂1＂ to 에 n−1 ＂to the variable X. Perform step S5 of storing the step S5, and determine step S6 of determining whether the value of the variable X is? ° to check whether the phase of the burst signal and the subcarrier signal coincides; If the variable (X) value in S6) is not The routine L2 is performed to determine whether the multiplication value Vi of the burst signal and the subcarrier is increased or decreased while decreasing the Vo value to find the Vo value when the phases of the wave match (Vm), and the step S6. ) If the result of the variable (X) is ＂ø 자동 automatic tint adjustment method to perform the step (S10) to fix the Vo value to Vm and terminate.