JPH0160156B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to an input signal switching device for a display device, and in particular, for a display device that receives RGB three primary color signals, the input signal switching device automatically switches signals depending on whether the three primary color signals are analog signals or digital signals. The present invention relates to a device for switching routes. Conventional technology and its problems In the conventional color signal output method, RGB
The signal system is a system that separately outputs three primary color signals of R (red), G (green), and B (blue) and horizontal and vertical synchronization signals. In addition to these three primary color signals, there are analog signals extracted from color television cameras, etc., and transistors and signals from personal computers, etc.
There are two types: digital signals (TTL signals) extracted from transistor logic (TTL). However, the same
The three primary color signals supplied to the RGB input terminal are only one of the above-mentioned analog signals and digital signals, and the problem is that it is not possible to automatically switch between analog and digital signals for reception and display. The dot was hot. Therefore, the present invention makes it possible to receive and display either signal by determining whether the analog signal or digital signal is supplied to the same input terminal and switching the signal transmission path according to the input signal format. An object of the present invention is to provide an input signal switching device in a display device that can be used. Means for Solving the Problems The present invention provides three primary color signals supplied to the three primary color signal input terminals.
When the primary color signal is an analog signal, a first synchronization signal transmitted together with the analog signal is provided;
When the three primary color signals supplied to the input terminal are digital signals, a second synchronization signal is transmitted together with this digital signal, and depending on the detection level of the supplied first or second synchronization signal, an identification circuit that identifies whether the three primary color signals supplied to the input terminal are analog signals or digital signals;
It is constructed of a switching circuit that selectively supplies the input signal of the input terminal to either the analog signal processing circuit or the digital signal processing circuit according to the output control signal of the identification circuit, and an example thereof will be described below. This will be explained with drawings. Embodiment FIG. 1 shows a block system diagram of an embodiment of the apparatus of the present invention. In the figure, 1, 2, and 3 are input terminals for red, green, and blue signals, respectively, and the primary color signals input to input terminals 1, 2, and 3 are sent to color signal processing circuits 5, 6, and 7, respectively. Supplied. In addition, a vertical synchronizing signal that is separately transmitted is input to the input terminal 4 together with the primary color signals that are supplied to the above-mentioned input terminals 1 to 3, and this vertical signal is supplied to the identification circuit 8 and the synchronizing signal processing circuit 9, respectively. Ru. As will be described later, the identification circuit 8 determines whether the input primary color signals at the input terminals 1 to 3 are analog signals transmitted from a color television camera or the like, or digital signals (TTL signals) transmitted from a personal computer or the like. If the input primary color signal is an analog signal, the switch circuits 12 and 1 are output via the output terminal 10.
At the same time, the switch circuit 18 in the color signal processing circuit 5 and the color signal processing circuit 6 are applied via the output terminal 11 to turn on the control signals 3 and 14.
A control signal is applied to a switch circuit (not shown) corresponding to switch circuit 18 in (analog signal processing circuit). When the switch circuits 12 to 14 are turned on, the inputs 1, 2, and 3 are connected to the resistor 1 whose resistance value is, for example, 75Ω.
5, 16, 17 and switch circuits 12, 13, 1
Connected to ground via 4. Note that the color signal processing circuits 6 and 7 have the same configuration as the color signal processing circuit 5, so in the following explanation, only the operation of the color signal processing circuit 5 will be explained, and the explanation of the operation of the color signal processing circuits 6 and 7 will be omitted. do. On the other hand, when the identification circuit 8 identifies that the input primary color signal is the digital signal from the vertical synchronization signal level, it generates a control signal to turn off the switch circuits 12 to 14 and outputs it to the output terminal 10. The switch circuit 18 is switched and connected to the terminal a side to generate a control signal for selectively outputting the input signal to the digital signal processing circuit 19 and output it to the output terminal 11. By turning off the switch circuits 12 to 14,
Each primary color signal coming into input terminals 1 to 3 is connected to a resistor 15.
-17 are not terminated and are supplied to color signal processing circuits 5-7. The signal forms of the input primary color signals of the input terminals 1 to 3, the on/off states of the switch circuits 12 to 14, and the connection state of the switch circuit 18 are summarized in the following table.

[Table] Further, the synchronization signal processing circuit 9 is supplied with a vertical synchronization signal and furthermore a horizontal synchronization signal, and generates a deflection current etc. to be passed through a yoke for deflecting an electron beam of a cathode ray tube (CRT) 27, which will be described later. The digital signal processing circuit 19 performs waveform shaping on the input digital signal using a gate circuit as described later, and then outputs a contrast-adjusted voltage-current conversion signal. On the other hand, the analog signal processing circuit 20 performs voltage-current conversion on the input analog signal for contrast adjustment as described later, and outputs the converted analog signal. The red signal current taken out from the digital signal processing circuit 19 or the analog signal processing circuit 20 is output to the output terminal 2.
1 to the color output circuit 24. Similarly, the green signal current and blue signal current taken out from the color signal processing circuits 6 and 7 are output from the output terminals 22 and 2.
3 to color output circuits 25 and 26. The color output circuits 24, 25, and 26 perform current-voltage conversion and amplification on the input primary color signal current to obtain a required voltage, and output the voltage to the cathode of the CRT 27.
As a result, a color image is displayed on the CRT 27. According to this embodiment, regardless of whether the primary color signal is an analog signal or a digital signal, by supplying it to the input terminals 1 to 3, it is possible to identify whether it is an analog signal or a digital signal from the level of the vertical synchronization signal, and automatically convert the primary color signal to an analog signal or a digital signal. color signal processing circuit 5~
Since the signal path within 7 is switched,
The CRT 27 can display both analog and digital signals. Next, the apparatus of the present invention will be explained in more detail with reference to FIGS. 2 and 3. FIG. 2 shows a circuit diagram of an embodiment of the device of the present invention. In the figure, the same components as in FIG. 1 are designated by the same reference numerals. In FIG. 2, input terminals 1, 2 and 3 are connected to one input terminal of each of TTL AND circuits 29 ₁ , 29 ₂ and 29 ₃ , while resistors R ₁₁ and R ₁₂ each having a resistance value of 75Ω
and _R13 to the respective collectors of switching NPN transistors _Q11 , _Q12 , and _Q13 , and input terminals 1, 2, and 3 are connected to switching NPN transistors via capacitors _C11 , _C12 , and _C13 .
Connected to each base of Q ₃₁ , Q ₃₂ and Q ₃₃ .
The other input terminal of each of the AND circuits 29 ₁ , 29 ₂ and 29 ₃ is connected to the switching terminal via the output terminal 11.
Connected to the connection point between the collector of the NPN transistor Q ₈ and the resistor R ₁₀ , and also connected to the switching NPN transistors Q ₂₁ and Q ₂₂ via the resistors R ₃₁ , R ₃₂ and R ₃₃
and connected to the base of Q ₂₃ . Additionally, capacitors C ₁₁ , C ₁₂ and C ₁₃ and transistors Q ₃₁ , Q ₃₂
and each connection point with the base of Q ₃₃ is a transistor
collectors of Q ₂₁ , Q ₂₂ and Q ₂₃ and diodes D ₁₁ ,
The cathodes of D ₁₂ and D ₁₃ are connected, and the anodes of diodes D ₁₁ , D ₁₂ and D ₁₃ are connected to a DC voltage source.
Commonly connected to E ₃ . Diode _D11 , _D12
and _D13 are clamp diodes for applying a predetermined bias to the input signal. The collectors of transistors Q ₃₁ , Q ₃₂ and Q ₃₃ are
The collectors of NPN transistors Q ₄₁ , Q ₄₂ and Q ₄₃ are connected to the emitters of differential amplification NPN transistors Q ₅₁ and Q ₆₁ , the emitters of Q ₅₂ and Q ₆₂ , and the emitters of Q ₅₃ and Q ₆₃ , respectively. Also transistor
Q ₃₁ and Q ₄₁ emitters, Q ₃₂ and Q ₄₂ emitters and
The emitters of Q ₃₃ and Q ₄₃ are resistors R ₄₁ , R ₄₂ and R ₄₃ respectively.
is grounded through. The base of the transistor _Q41 and the output terminal of the AND circuit ₂₉₁ are connected to a DC voltage source _E2 via a resistor _R51 . Similarly, the bases of transistors Q ₄₂ and Q ₄₃ and AND circuit 2
The output terminals 9 ₂ and 29 ₃ are connected to E ₂ via resistors R ₅₂ and R ₅₃ . Transistor Q ₆₁ , Q ₆₂
and Q ₆₃ are connected to output terminals 21, 22 and 23, respectively. Further, each base and each collector of transistors Q ₅₁ , Q ₅₂ and Q ₅₃ are connected to DC voltage sources E ₄ and E ₁ , respectively. Furthermore, the transistor Q ₆₁ ,
The bases of Q ₆₂ and Q ₆₃ are commonly connected to the slider of the variable resistor VR. This variable resistor VR is a variable resistor for contrast adjustment, and is a variable resistor common to the color signal processing circuits 5, 6, and 7, respectively. On the other hand, the input terminal 4 is connected to the switching circuit via a detection circuit consisting of a diode D ₂ and a capacitor C ₂ and a resistive voltage divider circuit consisting of resistors R ₆ and R ₇ .
Connected to the base of NPN transistor _Q7 . Collector and collector resistance of transistor Q ₇
The connection point with _R8 is connected to the transistor through resistor _R9 .
The base resistors of transistors Q ₁₁ , Q ₁₂ and Q ₁₃ are connected through output terminal 10 while being connected to the base of Q _{8 .}
Connected to R ₂₁ , R ₂₂ and R ₂₃ . diode
D ₂ , capacitor C ₂ , resistors R ₆ to R ₁₀ and transistors Q ₇ and Q ₈ constitute an identification circuit 8. As can be seen from FIG. 2, the color signal processing circuit 5 from the input terminal 1 to the output terminal 21, and the input terminal 2
Since the color signal processing circuit 6 from the input terminal 3 to the output terminal 22 and the color signal processing circuit 7 from the input terminal 3 to the output terminal 23 have the same configuration, the following explanation will mainly focus on the operation of the color signal processing circuit 5. do. First, a case where analog primary color signals are input to input terminals 1, 2, and 3 will be described. When this analog signal is received, a vertical synchronizing signal having a waveform as shown in FIG. 3A is received at the input terminal 4 in addition to the primary color signal. As shown in FIG. 3A, this vertical synchronization signal has a vertical period of 16.7ms, a negative voltage vertical synchronization signal period of 0.19ms, and a voltage amplitude of 1Vp-p to 8Vp-p, Since it is transmitted through capacitive coupling, the following equation holds true. V ₁ +V ₂ ≦8 V ₁ /V ₂ =0.19/16.51 (1) However, in the above formula, V ₁ is the positive amplitude of the vertical synchronization signal, V ₂ is the negative amplitude, and 16.51 is the vertical period.
The period (unit: ms) is obtained by subtracting the vertical synchronization signal period of 0.19 ms from 16.7 ms. Therefore, it can be seen from equation (1) that the positive amplitude V ₁ is 0.1V or less. On the other hand, the vertical synchronization signal transmitted together with the primary color signal of the digital signal, which will be described later, is shown in Fig. 3B.
As shown in Figure A, the vertical period and vertical synchronization signal period are the same as those of the vertical synchronization signal shown in Figure A.
The voltage amplitude is OV or 5V (minimum value is 2.8V), and the positive amplitude V ₁ is expressed as 2.8≦V ₁ ≦5 (2). Therefore, the identification circuit 8 is connected to the input terminal 4
The positive amplitude V ₁ of the vertical synchronization signal that has entered is detected by the diode D ₂ and the capacitor C ₂ . When the primary color signal of the analog signal is input, the vertical synchronization signal shown in _FIG .
This voltage is further resistively divided by resistors R ₆ and R ₇ and then applied to the base of transistor Q ₇ , so transistor Q ₇ is turned off. Therefore, the collector potential of the transistor _Q7 becomes a positive voltage value of the DC voltage source _E1 , that is, a high level (hereinafter referred to as "H"), and is output to the output terminal 10, while
It is applied to the base of transistor Q ₈ through resistor R ₉ , turning it on. Therefore, the transistor
The collector potential of Q ₈ becomes approximately the ground level, that is, a low level (hereinafter referred to as "L"), and is output to the output terminal 11. The "H" control signal taken out from the output terminal 10 is applied to the bases of transistors Q ₁₁ , Q ₁₂ and Q ₁₃ corresponding to switch circuits 12, 13 and 14 to turn them on. Therefore, the analog signals coming into input terminals 1, 2 and 3 are
After being terminated to R ₁₁ , R ₁₂ and R ₁₃ , AND circuit 2
It is applied to one input terminal of each of 9 ₁ , 29 ₂ and 29 ₃ and to capacitors C ₁₁ , C ₁₂ and C ₁₃ . On the other hand,
The "L" control signal from the output terminal 11 is applied to the other input terminal of each of the AND circuits 29 ₁ , 29 ₂ and 29 ₃ . Therefore, AND circuits 29 ₁ to 29 ₃
The output signal of is always "L", so that transistors Q ₄₁ , Q ₄₂ and Q ₄₃ are turned off. Further, the "L" control signal from the output terminal 11 turns off the transistors Q ₂₁ , Q ₂₂ and Q ₂₃ , respectively. The input analog signals at input terminals 1, 2 and 3 are therefore supplied to the bases of transistors Q ₃₁ , Q ₃₂ and Q ₃₃ . The red signal voltage supplied to the base of transistor Q ₃₁ causes the transistor
A collector current of a level corresponding to the red signal voltage flows through Q ₅₁ and Q ₆₁ , respectively, so that the output terminal 21
A current with a level corresponding to the red signal voltage is extracted. Here, the base voltage of the transistor Q ₆₁ changes depending on the resistance value of the variable resistor VR, and the collector current of the transistor Q ₆₁ also changes depending on the base voltage. A red signal current whose amplitude value is variably controlled by the device VR, that is, whose contrast is adjusted, is extracted. Similarly, output terminals 22, 23
From these, a green signal current and a blue signal current whose contrast has been adjusted by a variable resistor VR are taken out, respectively. Of course, these output currents are analog signals. Next, the case where primary color signals of digital signals are input to input terminals 1, 2 and 3 will be explained. In this case, the detected voltage of the voltage value shown by the above equation (2) is applied to the base of transistor Q ₇ after being resistively divided by resistors R ₆ and R ₇ , so transistor Q ₇ is turned on. Ru. Therefore, the transistor
The collector potential of _Q7 becomes “L”, and the output terminal 1
0 as an "L" control signal, and is applied to the base of transistor _Q8 to turn it off. Therefore, the collector potential of the transistor _Q8 becomes "H" and is outputted to the output terminal 11 as an "H" control signal. Since the transistors Q ₁₁ , Q ₁₂ and Q ₁₃ are turned off by the above-mentioned “L” control signal from the output terminal 10, the input digital signals at the input terminals 1, 2 and 3 are transmitted through the resistors R ₁₁ , R ₁₂ and R ₁₃ and is supplied to one input terminal of each of AND circuits 29 ₁ , 29 ₂ and 29 ₃ . Furthermore, the AND circuits 29 ₁ , 29
The gates of transistors _{Q 2} and 29 ₃ are controlled to be in an "open" state, and transistors Q ₂₁ , Q ₂₂ and Q ₂₃ are respectively controlled to be on. Transistors Q ₂₁ , Q ₂₂ and
When Q ₂₃ is turned on, their collector potentials are always “L”, so transistors Q ₃₁ , Q ₃₂ and
The base potential of Q ₃₃ is also always “L”, and Q ₃₁ , Q ₃₂
and Q ₃₃ are respectively turned off. Therefore, the digital signals input to input terminals 1, 2 and 3, respectively, are sent to AND circuits 29 ₁ , 29 ₂ and 2
After the waveform is shaped by 9 ₃ and its logic “1” level is made to be the same level as the peak level of the analog signal by DC voltage source E ₂ , the bases of transistors Q ₄₁ , Q ₄₂ and Q ₄₃ are is supplied to That is, when an analog signal is input, the primary color signal voltage supplied to the bases of the transistors Q ₃₁ , Q ₃₂ and Q ₃₃ is input as a digital signal, the signal transmission path is switched and the primary color signal voltage is supplied to the bases of the transistors Q ₄₁ , Q ₄₂ and Q. It will be supplied to each of _{the 43} bases. In this way, the red signal voltage supplied to the base of the transistor Q ₄₁ causes collector currents of levels corresponding to the red signal voltage to flow through the transistors Q ₅₁ and Q ₆₁ , respectively, and as a result, the output terminal 2
1, a digital signal current whose level corresponds to the red signal voltage and whose level is controlled by the variable resistor VR is taken out. Similarly, from the output terminals 22 and 23, a green signal current and a blue signal current of digital signal waveforms whose contrast is adjusted by a variable resistor VR are taken out, respectively. The signal forms of the input signals at the input terminals 1, 2 and 3, the control signal levels at the output terminals 10 and 11, and the transistors _Q11 to _Q13 ,
The relationship between on and off of Q ₂₁ to _{Q 23} is shown in the following table.

[Table] Application examples Note that the present invention is not limited to the above embodiments; for example, even if a horizontal synchronization signal is supplied to the identification circuit 8, it will be possible to similarly distinguish between analog signals and digital signals. can do. Effects As described above, according to the present invention, the signal transmission path is switched depending on whether the input primary color signal is an analog signal or a digital signal and is supplied to a predetermined signal processing circuit. It has the advantage that whether the primary color signal supplied to the receiver is an analog signal or a digital signal, it can be automatically switched and displayed on the display.

[Brief explanation of drawings]

FIG. 1 is a block system diagram showing an embodiment of the device of the present invention, FIG. 2 is a circuit diagram showing an embodiment of the device of the present invention, and FIGS. 3A and 3B are for explaining the operation of the circuit shown in FIG. 2. FIG. 3 is a vertical synchronization signal waveform diagram. 1...Red signal input terminal, 2...Green signal input terminal, 3...Blue signal input terminal, 4...Vertical synchronization signal input terminal, 5-7...Color signal processing circuit, 8...
...Identification circuit, 9...Synchronization signal processing circuit, 12-1
4, 18... switch circuit, 19... digital signal processing circuit, 20... analog signal processing circuit,
21 to 23...Primary color signal output terminals, 29 ₁ to 29 ₃
...AND circuit.

Claims (1)

[Claims] 1. In a display device that receives and displays three primary color signals supplied to a three primary color signal input terminal, when the three primary color signals supplied to the input terminal are analog signals, the first color signal transmitted together with the analog signal
When the three primary color signals supplied to the input terminal are digital signals, a second synchronization signal transmitted together with the digital signal is supplied; 3 supplied to the input terminal according to the detection level of the synchronization signal of
an identification circuit that identifies whether the primary color signal is the analog signal or the digital signal; and an output control signal of the identification circuit that selectively inputs the input signal of the input terminal to either the analog signal processing circuit or the digital signal processing circuit. 1. An input signal switching device for a display device, comprising a switching circuit that supplies signals, and displays output signals of the analog signal processing circuit and the digital signal processing circuit.