JPH04185091A - Video signal processing circuit - Google Patents

Abstract

PURPOSE:To allow an IC to correspond to both of a liquid crystal TV and a CRT TV by adding either one of a Y signal and a reference voltage source signal selected by each switch either one of the 1st and 2nd chrominance signal to output the added signal and adding the 3rd chrominance signal formed from the 1st and 2nd chrominance signals to the Y signal to output the added signal. CONSTITUTION:Either one of the Y signal outputted from a video signal processing circuit and the reference voltage source signal is selected by each of switches 27, 28 in a matrix circuit and added to each of color difference signals R-Y, B-Y outputted from chroma signal processing circuits by each of adders 24, 25 and respective added values are outputted from terminals 3, 5. On the other hand, the color difference signals R-Y, B-Y are synthesized by a G-Y matrix 16 to form the 3rd color difference signal G-Y, which is added to the Y signal by an adder 26 and the added signal or the Y signal is outputted from a terminal 4. Since the liquid crystal TV original chrominance signal and a CRT TV added signal between the color difference signal and the Y signal are outputted from the same IC, the IC can correspond to both the TVs.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a video signal processing circuit for a television receiver. .

(Prior Art) In recent years, many TV receivers have built-in satellite broadcasting receivers (BS), allowing them to selectively receive images from a variety of video signal sources. Against this tendency, T
The V upper set uses so-called PIF (Picture In Picture), which allows you to monitor other sources simultaneously on a small screen.
re) Adding functions is once again in the spotlight. A receiving circuit for a small screen requires another independent video signal processing circuit in addition to the video signal processing circuit for the main screen.

Video circuits for small screens include many digital circuits such as field memories, microcomputers, and timing controllers for performing actual screen display. These digital circuits usually operate on a 5V power supply, and the entire circuit is shielded with a metal plate to prevent spurious signals.

A low-voltage IC circuit for LCD TVs that can operate on a 5V power supply is suitable for such a video signal processing circuit for a small screen.
It is often adopted. In LCD TV applications, signals are output almost directly to the LCD panel, so it is common to configure a matrix circuit to output the primary colors of R, G, and H.
Since CRT is the target for PIF of large screen TV, B-
It is common to output Y, RY color difference signals, a Y signal, and a Y signal.

Therefore, an IC with Madrisk circuit for LCD TV is
If you try to use it for PIF use in RT, you will need to re-matrix it outside the IC to obtain the signal, or you will have to design and remanufacture the matrix circuit for PIF to create an IC, which results in a lack of flexibility in adopting a set. There are drawbacks.

(Problem to be solved by the invention) In the conventional video signal processing circuit for small screen, LCD screen and CRT
However, the state of the drive signal is different, and conventional IC-based video signal processing circuits for small screens are not compatible with LCD and CRT TVs.

An object of the present invention is to provide a video signal processing circuit that can be used for liquid crystal TVs and CRT-TVs with one type of IC and is flexible enough to be used as a set.

[Structure of the Invention] (Means for Solving the Problems) In the video signal processing circuit of the present invention, a reference power supply V rer is prepared in place of the Y signal, and the B and R matrix circuits use the Y signal input to the adder and Switch between Vrer and
The G matrix circuit is capable of switching between the primary color G signal and the Y signal, and the polarity of the switching circuit is controlled by an external control signal.

(Function) With this configuration, in the B and R matrix circuits, it is possible to select whether the signal to be added is the Y signal or no signal (DC), so whether to output the B and R primary color signals or the B-Y and R- It becomes possible to select and switch whether to output a Y color difference signal. In addition, the G matrix circuit allows switching between the G primary color signal and the Y signal, so the same IC can be used for LCD TVs (primary colors) and CRTs (two color difference signals and Y signals) using an external control signal. is possible.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a video signal processing circuit according to the present invention.

In FIG. 1, a video signal separated by a Y/C separation circuit from a composite video signal detected by a video intermediate frequency detection circuit (not shown) is input to terminal 1, and a chroma signal is input to terminal 2. The video signal undergoes signal processing such as contrast control 6, image quality adjustment, DC reproduction 7, and brightness control in the video signal processing circuit 11, and then is sent to the matrix circuit 21 as a Y signal 15.

In the chroma signal processing circuit 12, the chroma signal at the terminal 2 is amplified by the ACC circuit 8, the continuous wave phase-locked to the burst signal is reproduced by the color synchronization circuit 10, and the demodulation circuit 9 generates a color difference signal using the reproduced continuous wave. Demodulate. The demodulated color difference signals B-Y and RY signals are input to the matrix circuit 21. Further, the reference power supply Vref' 23 and the output switching signal 20 are input to the matrix circuit 21.

FIG. 2 shows the matrix circuit 21 of FIG. 1 in more detail. Two input color difference signals R-Y, B-
A G-Y signal is generated from Y by a G-Y matrix circuit 16. The R-Y signal is connected to one input terminal of the adder 24, and either the Y signal 15 or the reference power supply Vref'23 is connected to the other input terminal of the adder 24 via the switch 2.
7 to select and input. Similarly, the BY signal is connected to one input terminal of the adder 25, and either the Y signal or V rel' is selected by the switch 28 and input to the other input terminal. G-Y with R-Y and B-Y input
The output signal of the matrix circuit 16 is connected to one input terminal of an adder 26, and the Y signal is connected to the other input terminal. Either the output of the adder 26 or the Y signal is selected by a switch 29.

The output signal of the adder 24 is sent to the R or RY signal output terminal 3.
, the output signal of the adder 25 is connected to the B or BY signal output terminal 5, and the selection signal of the switch 29 is connected to the G or Y signal output terminal 4. When the switches 27 to 29 are connected in the illustrated state, primary color signals R, B, and G appear at the output terminals 3 to 5;
-Y.

B-Y and Y signals appear. Switching of the switches 27 to 29 is performed by an external control signal 20, and all switches operate in conjunction with each other.

FIG. 3 shows the RY matrix circuit section of FIG. 2 in more detail. In the same figure, transistor Ql-
Q9 is a voltage-current conversion circuit 100 that converts an RY voltage input signal into a current, and transistors QIO to Q15 are a switching circuit 200 that selects a Y signal or Vrer. The switching circuit 200, the resistor R12, and the converted current of the voltage-current conversion circuit 100 constitute an adder circuit 300, which is outputted via the buffer circuit 400 of transistors Q1B and 028.

This is an output switching control circuit 500 that switches the output of transistors Q19 to Q26.

Transistors Q2 and Q3 and resistors R2 and R8 are biased with constant current to transistor Ql, and differential amplifier DA
Configure. The signal current converted by this differential amplifier DA is transferred to the current mirror circuit CMI of transistors Q4 to Q7.
The signal is then folded back, and further single-ended by a current mirror circuit CM2 of transistors Q8 and Q9 and output. The switching circuit 200 is composed of two sets of differential amplifiers DA2 and DA3 connected as voltage followers, and shares a current mirror circuit CM3 of transistors Q14 and Q15, which is a load circuit. V rer signal to the base of transistor QIO and Y to the base of transistor Q12.
Input the signal. The output is transistor Q11 and Q1
3 from the collector/base common connection point. For example, if the Y signal is selected, the transistor Qll
A Y signal appears at the base of the circuit and is output at low impedance. Since the RY color difference current signal flows to the base of the transistor Qr3 via the resistor R12, the RY signal appears between the terminals of the resistor R12. Therefore,
The signal at the base terminal of transistor Q18 is connected to the Y signal R-Y.
The R signal is obtained by superimposing the signals. On the contrary, Vve
Assuming that the r signal is output, the transistor Qll
The base is at Vrer potential (DC), and only the RY color difference signal generated at the resistor R12 appears at the base of the transistor Q1B.

Let vth be the potential at the connection point of resistors R17 and RlB. Among the transistors Q21 and Q22 that constitute the constant current biased differential amplifier DA4, when the base potential of transistor Q22 is higher than vth, transistor Q21 is turned on, and when it is lower, it is turned on. transistor Q22 turns on. Now, when transistor Q21 turns on, transistor Q2
All constant current supplied by 0 flows through transistor Q21. The output current of the transistor Q21 activates the voltage follower circuit of the differential amplifier DA2 via the current mirror circuit CM4 of the transistors 023 and Q25. Conversely, when transistor Q22 is on, the current mirror circuit CM5 of transistors Q24 and Q2B
The differential amplifier D A :11 becomes active. Since only the activated voltage follower circuit outputs a signal, the Y signal or the Vrer signal can be switched by switching the bias current.

A circuit that can selectively connect similar circuits to the B-Y and G matrix circuit sections to obtain an output of B or B-Y at the output terminal 5 and an output of 6 or Y at the output terminal 4. can be realized.

In this way, the output is set to R, by the external control signal.
It can be set to a state in which G and B are output and a state in which RY and B-YSY are output. Therefore, it is possible to realize a video signal processing circuit for use in liquid crystal TVs and CRT-TVs using a common IC, and it is possible to flexibly support TVs with different display means.

FIG. 4 shows another embodiment of the invention. Second
Although the G matrix circuit shown in the figure switches between the G and Y signals, the same effect as shown in FIG. 2 can be achieved by cutting the G-Y signal as shown in FIG. 4.

The present invention is not limited to the above-described embodiments, but can also obtain similar effects for multiple systems of input signals input from the outside, and in that case, a switch to select between internal and external inputs of the matrix circuit can be used. All you have to do is set it up.

[Effects of the Invention] As described above, according to the video signal processing circuit of the present invention, it is possible to realize a common IC for matrix circuits for LCD TVs and CRT-TVs, and it is possible to achieve flexibility in set compatibility. You can have it.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing a video signal processing circuit of the present invention, FIG. 2 is a system diagram showing a specific example of the matrix circuit of FIG. 1, and FIG. 3 is a more specific diagram showing a part of FIG. FIG. 4 is a system diagram showing another embodiment of the present invention. 27-29... Switches 24-26... Adders 3-5... Output terminal

Claims (3)

[Claims] (1) A first switch that selects either the Y signal or the reference voltage source, and first and second adding means that add the signal selected by this switch and the first and second color difference signals, respectively. , first and second outputs supplying the outputs of the first and second adding means, and said first and second outputs.
means for generating a third color difference signal from the color difference signal; third addition means for adding the output of this means and the Y signal; and either one of the output of the third addition means and the Y signal. , a second switch for selection, and a third output taken out from the output of the second switch. (2) First and second switches that select one of the B-Y and R-Y color difference signals, the G-Y color difference signal generated by combining these color difference signals, the Y signal, and the reference voltage source. and,
a first adder that adds the first switch output and the B-Y signal; a second adder that adds the output of the second switch and the R-Y signal;
first and second output terminals that respectively take out the output of the second adder; a third adder that adds the G-Y and Y signals; and a third adder that adds the output of the adder and the Y signal. A video signal processing circuit comprising a third switch for selection and a third output terminal for taking out the output of the switch. (3) A claim characterized in that the third switch is a switch for inputting the G-Y signal to the third adder, and the third output terminal is connected to the output of the third adder. 2. The video signal processing circuit according to item 2.