JP3465816B2 - Display device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal having a relatively stable frequency such as a computer signal, a television signal received by a television tuner, and a video tape recorder. The present invention relates to a display device that displays both a VTR signal and a general video signal whose frequency is relatively unstable, such as a VTR signal reproduced by a VTR. 2. Description of the Related Art In a display device connected to a personal computer (hereinafter abbreviated as a personal computer) for displaying data (a personal computer signal),
The self-running deflection frequency is made to follow the frequency of the input video signal by immediately responding to a change in the frequency of the input video signal. Thus, the display device can display the personal computer signal in an instant corresponding to the switching of the display mode of the personal computer. FIG. 3 is a block diagram showing an example of a conventional display device adapted to immediately respond to a change in the frequency of an input video signal. In FIG. 3, a microcomputer (hereinafter abbreviated as a microcomputer) 1 includes:
Horizontal sync signal of video signal by PC signal and PLL
The horizontal oscillation signal from the circuit 2 is input. The horizontal synchronization signal is also input to the PLL circuit 2. The PLL circuit 2
A horizontal oscillation signal synchronized with the horizontal synchronization signal is generated. This horizontal oscillation signal is supplied to each circuit section such as a horizontal deflection circuit of the display device. The microcomputer 1 includes counting units 11 and 12,
The counter 11 counts the horizontal synchronization signal, and the counter 12
The horizontal oscillation signal from the L circuit 2 is counted. Counting unit 11,
The output of the counter 12 is input to the comparator 13, which compares the outputs of the counters 11 and 12. The output of the comparison unit 13 is input to the voltage generation unit 14, and the voltage generation unit 14 generates a voltage according to the output of the comparison unit 13. The PLL circuit 2
As is well known, it has a voltage controlled oscillator (VCO) 21, and the voltage output from the voltage generator 14 is input to the VCO 21 as a VCO voltage. As a result, the PLL circuit 2 immediately follows the change in the horizontal frequency of the input video signal and makes the free-running frequency coincide with the horizontal frequency of the input video signal. At this time, the microcomputer 1 performs a certain degree of filtering on the change in the horizontal synchronization signal in determining whether or not the horizontal frequency of the input video signal has changed in consideration of the influence of noise and the like. However, this filtering greatly depends on the responsiveness of the horizontal frequency, that is, the responsiveness to the switching of the display mode of the personal computer, so that it has to be minimized. [0006] By the way, in recent display devices, not only a video signal by a personal computer signal whose frequency is relatively stable, but also a television signal received by a television tuner or a VTR reproduced by a VTR. Video signals having relatively unstable frequencies such as signals have also been displayed. When an operation for immediately following a change in the horizontal frequency as described with reference to FIG. 3 is performed on a video signal such as a VTR signal that is not stable over a certain range of horizontal frequency, the following problem occurs. is there. For example, the horizontal frequency follow-up function operates even when the horizontal frequency is slightly changed, such as when the VTR is rewound or fast-forwarded, and the horizontal frequency is switched, so that the VTR signal can be stabilized. Cannot be displayed. Further, even when a television signal received by a television tuner is input, the horizontal synchronization signal from the synchronization separation circuit is not stable under the condition of inter-station noise or a weak electric field. Problems will arise. As described above, in the conventional display device, a personal computer video signal whose frequency should immediately follow a change in horizontal frequency is stable, and a frequency which should not immediately follow a change in horizontal frequency is unstable. There is a problem in that it cannot cope with both general video signals (television signals and VTR signals received by a television tuner). The present invention has been made in view of such a problem, and can cope with both a personal computer video signal having a stable frequency and a general video signal having an unstable frequency. It is an object to provide a display device capable of displaying an image. According to the present invention, in order to solve the above-mentioned problems of the prior art, a plurality of input terminals (3A to 3D) in a plurality of signal formats and an input from the input terminals are provided. A selection circuit (4) for selecting a video signal to be output, a synchronization separation circuit (5) for separating a horizontal synchronization signal from a video signal input from an input terminal selected by the selection circuit,
A PL having a voltage-controlled oscillator (21) and horizontally oscillating by a horizontal synchronization signal separated by the synchronization separation circuit;
An L circuit (2); and a horizontal frequency tracking circuit (1) for comparing the horizontal oscillation signal with the horizontal synchronization signal by comparing the horizontal oscillation signal output from the PLL circuit with the horizontal synchronization signal. In the display device, the plurality of input terminals are connected to a computer signal.
First input terminals (3C, 3D) to which only image signals are input
And a second input terminal to which only a general video signal is input,
(3B), video signal by computer signal and general video
And a third input terminal (3
A), wherein the selection circuit has the first to third input terminals.
Controlling which input terminal is selected
A control circuit (6), wherein the control circuit includes the third input circuit.
Video signal by computer signal and general video signal
Manages user settings for inputting
Switching the selection circuit to select the first input terminal.
When controlled, the horizontal oscillation signal is converted to the horizontal synchronization signal.
The horizontal frequency so as to be the first mode to follow
Controlling the tracking circuit to operate, and the selecting circuit
When switching control is performed to select the second input terminal,
The horizontal oscillation is performed by supplying a fixed voltage to the voltage-controlled oscillator.
Before the second mode in which the signal has a fixed frequency,
Control to make the horizontal frequency tracking circuit inactive,
Switching control so that the selection circuit selects the third input terminal.
The first mode according to the user setting.
Mode or one of the second modes
Thus, the present invention provides a display device characterized by controlling the horizontal frequency tracking circuit . Hereinafter, a display device according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is a block diagram showing one embodiment of the display device of the present invention, and FIG.
5 is a flowchart showing the operation of the display device of the present invention. In FIG. 1, the same parts as those in FIG. 3 are denoted by the same reference numerals. The display device of the present invention has video signal input terminals of various signal formats. In FIG.
The input terminal 3A is a BNC terminal. An RGB signal which is a personal computer video signal or a component video signal which is a general video signal such as a television signal or a VTR signal received by a television tuner is input to the input terminal 3A. Is done. That is, the input terminal 3A is a terminal to which one of a personal computer video signal and a general video signal is selectively input. Since the signal processing inside the display device is different between the RGB signal and the component video signal, the user previously selects whether to input a personal computer video signal or a general video signal to the input terminal 3A by using a menu or the like. Keep it. The host CPU 6 manages whether a personal computer video signal or a general video signal is being input to the input terminal 3A. An input terminal 3B is a composite video input terminal or a Y / C separation input terminal (so-called S input terminal) into which a luminance (Y) signal and a color (C) signal are separated and inputted.
The input terminal 3B receives a composite video signal as a general video signal or a Y / C separated component video signal. That is, the input terminal 3B is
This is a terminal to which only general video signals are input. Input terminal 3
C and 3D are D-SUB terminals.
RGB signals, which are PC video signals, are input to C and 3D. That is, the input terminals 3C and 3D are terminals to which only personal computer video signals are input. The personal computer video signals or general video signals input from these input terminals 3A to 3D are input to the selection circuit 4. The selection circuit 4 selects one of the input terminals 3A to 3D under the control of the host CPU 6.
When a user operates a key provided on a remote control transmitter or a main body (not shown), the host CPU 6 controls the selection circuit 4 to select any one of the input terminals 3A to 3D. The video signal from the terminal selected by the selection circuit 4 is input to the synchronization separation circuit 5. The synchronization separation circuit 5
The horizontal synchronization signal is separated from the input video signal. The horizontal synchronizing signal is input to a microcomputer (hereinafter abbreviated as a microcomputer) 1 and a PLL circuit 2. The PLL circuit 2 generates a horizontal oscillation signal synchronized with the horizontal synchronization signal. This horizontal oscillation signal is supplied to each circuit section such as a horizontal deflection circuit of the display device. The microcomputer 1 also receives the horizontal oscillation signal from the PLL circuit 2. In the present invention, the microcomputer 1 operates in a frequency tracking mode in which the horizontal frequency of the input horizontal synchronizing signal is tracked and in a predetermined free-running frequency without following the horizontal frequency of the input horizontal synchronizing signal. A fixed frequency mode is provided, and either the frequency following mode or the fixed frequency mode is selected. First, the operation in the frequency tracking mode will be described. The microcomputer 1 includes counting units 11 and 12. The counting unit 11 counts horizontal synchronization signals, and the counting unit 12 counts horizontal oscillation signals from the PLL circuit 2. Counting unit 1
1 and 12 are input to the comparing unit 13 and
Compares the outputs of the counting units 11 and 12. The output of the comparison unit 13 is input to the voltage generation unit 14, and the voltage generation unit 14
A voltage corresponding to the output of the comparing unit 13 is generated. As is well known, the PLL circuit 2 has a voltage controlled oscillator (VCO) 21, and the voltage output from the voltage generator 14 is V
It is input to the VCO 21 as a CO voltage. As a result, the PLL circuit 2 immediately follows the change in the horizontal frequency of the input video signal and makes the free-running frequency coincide with the horizontal frequency of the input video signal. At this time, the microcomputer 1 performs a certain degree of filtering on the change in the horizontal synchronization signal in determining whether or not the horizontal frequency of the input video signal has changed in consideration of the influence of noise and the like. This filtering is minimized because it greatly affects the responsiveness of the horizontal frequency, that is, the response to the switching of the display mode of the personal computer. The frequency tracking mode is a mode to be used when the video signal selected and input by the selection circuit 4 is a personal computer video signal whose frequency is stable. A control method for selecting the frequency tracking mode will be described later in detail. Note that the microcomputer 1
By comparing the horizontal oscillation signal output from the PLL circuit 2 with the horizontal synchronization signal from the synchronization separation circuit 5, the circuit operates as a horizontal frequency tracking circuit that causes the horizontal oscillation signal to follow the horizontal synchronization signal. Next, the operation in the fixed frequency mode will be described. As described above, it is not preferable to set the frequency tracking mode for a general video signal having an unstable frequency such as a television signal or a VTR signal received by a television tuner. Therefore, for a general video signal having an unstable frequency, the voltage generator 14 does not generate a VCO voltage according to the output of the comparator 13 but supplies a fixed VCO voltage to the VCO 21 to set a fixed frequency mode. . The voltage generator 14 converts the fixed VCO voltage to the VCO 21
, The PLL circuit 2 generates a horizontal oscillation signal oscillating at a fixed free-running frequency, and enters a fixed frequency mode. The voltage generator 14 is a VCO corresponding to the output of the comparator 13
Whether to generate a voltage or a fixed VCO voltage,
The host CPU 6 switches. Here, a method of controlling switching between the frequency following mode and the fixed frequency mode by the host CPU 6 will be described with reference to FIG. In FIG. 2, when a video signal is input to the display device, it is determined in step S1 whether or not the input has changed. The change in the input means both that the display mode of the personal computer is switched and that the terminal selected by the selection circuit 4 is switched by the input terminals 3A to 3D. If there is no change in the input, the process returns to step S1. If it is determined in step S1 that there is a change in the input, the process proceeds to step S2, in which the selected terminal is the input terminal 3C or 3D dedicated to a personal computer video signal.
Is determined. Input terminals 3C and 3D are DS
Since only the RGB signal which is a UB terminal and a personal computer video signal is input, the host CPU 6 proceeds to step S8.
At, control is performed in the frequency tracking mode, and the process returns to step S1. If it is determined in step S2 that the selected terminal is not the input terminal 3C or 3D, the process proceeds to step S3, and it is determined whether the selected terminal is the input terminal 3B dedicated to a general video signal. The input terminal 3B is a composite video input terminal or an S input terminal, and only the general video signal is input.
At 9, control is performed in the frequency fixed mode, and the process returns to step S1. If it is determined in step S3 that the selected terminal is not the input terminal 3B, the process proceeds to step S4 to determine whether the selected terminal is the input terminal 3A to which a personal computer video signal and a general video signal are selectively input. Is determined. Input terminal 3A
If not, the host CPU 6 controls the frequency tracking mode in step S8, and returns to step S1. If it is the input terminal 3A, the process proceeds to step S5. In step S5, it is determined whether or not the video signal input to the input terminal 3A is of a component type. The component system referred to here means that a video signal is a Y signal and two color difference signals (Pb, Pr or Cb, Cb).
This is the signal form input in r). In the case of the component system, the video signal input to the input terminal 3A is a general video signal, and in the case of the non-component system, it is a personal computer video signal based on RGB signals. Therefore, if it is determined in step S5 that it is not the component system, the host CPU 6 determines in step S8
Control is performed in the frequency tracking mode, and the process returns to step S1. Whether or not the video signal input to the input terminal 3A is of the component type can be determined by the setting by the user as described above, and the host CPU 6 recognizes whether or not of the component type. I have. Further, if it is determined in step S5 that the component system is used, it is determined in step S6 whether or not the horizontal synchronization signal of the input video signal is 15 kHz. The count value of the counting unit 11 is the host C
Since the input is input to the PU 6, the host CPU 6 recognizes the horizontal synchronization signal of the input video signal. The horizontal synchronization signal is 15 kHz (strictly speaking, 15.75 kHz
If z), since it is a general video signal of an NTSC signal or a PAL signal, the host CPU 6 proceeds to step S9.
At, the mode is controlled to the fixed frequency mode, and the process returns to step S1. If the horizontal synchronization signal is not 15 kHz, step S
Move to 7. In step S7, the horizontal synchronizing signal of the input video signal is 33 kHz (strictly, 33.75
(kHz). The horizontal sync signal is 33
If it is kHz, it is a general video signal of an HDTV signal, so that the host CPU 6 controls the mode to the fixed frequency mode in step S9, and returns to step S1. If the horizontal synchronization signal is not 33 kHz, in step S8, the mode is controlled to the frequency tracking mode, and the process returns to step S1. In a VTR provided with a time base collector (TBC), the horizontal frequency of the output video signal is stable. VTRs that record and reproduce HDTV signals often have a TBC. Therefore, when it is determined in step S7 that the signal is an HDTV signal, the process may proceed to step S8 to control the frequency tracking mode. As described above, in the display device of the present invention, when the selection circuit 4 selects an input terminal for inputting a personal computer video signal, the host CPU 6 as the control circuit selects the microcomputer 1 as the horizontal frequency tracking circuit. Is operated to set a frequency tracking mode in which the horizontal oscillation signal generated by the PLL circuit 2 follows the horizontal synchronization signal. When the selection circuit 4 selects an input terminal for inputting a general video signal, the microcomputer 1 performs the frequency tracking mode. Make the function inoperable and
A fixed voltage is supplied to the control circuit 21 so that the horizontal oscillation signal generated by the PLL circuit 2 is controlled to have a fixed frequency in a fixed frequency mode. Therefore, in the case of a personal computer video signal, the personal computer signal can be displayed instantly in response to the switching of the display mode of the personal computer. In the case of a general video signal, the general video signal can be displayed even when the horizontal frequency changes. It can be displayed stably. Further, in this embodiment, the host CPU 6
Operate also as a control circuit for switching control of the selection circuit 4. Therefore, the host CPU 6 can switch between the frequency following mode and the fixed frequency mode in synchronization with the switching control of the selection circuit 4. That is, the input terminal 3
If the selection circuit 4 is controlled to select a terminal to which only a personal computer video signal is input, such as a D-SUB terminal for C and 3D, a frequency tracking mode is set in conjunction with the switching control,
Composite video input terminal of input terminal 3B or Y
If the selection circuit 4 is controlled to select a terminal to which only the general video signal is input, such as the / C input terminal, the fixed frequency mode can be set in conjunction with the switching control. Therefore, in this case, it is not necessary to determine whether the input video signal is a personal computer video signal or a general video signal. In this embodiment, the host CPU 6
In the case where one of the PC video signal and the general video signal is selectively input, such as the BNC terminal of the input terminal 3A, a user setting for inputting either the PC video signal or the general video signal to the terminal. It also operates as a control circuit that manages Therefore, when the host CPU 6 controls the selection circuit 4 to select the input terminal 3A, the host CPU 6 can control to select two modes according to the signal format preset for the input terminal 3A by the user. . Further, since the frequency of the horizontal synchronization signal from the counting unit 11 is also used as information for selecting a mode, a mode is not erroneously selected. As described in detail above, the display device of the present invention comprises a plurality of input terminals in a plurality of signal formats, a selection circuit for selecting a video signal inputted from the input terminals, A synchronous separating circuit for separating a horizontal synchronizing signal from a video signal inputted from an input terminal selected by the selecting circuit, and a voltage controlled oscillator, wherein a horizontal synchronizing signal separated by the synchronizing separating circuit is used to oscillate horizontally.
And LL circuit, in a display apparatus having a horizontal frequency tracking circuit to follow the horizontal oscillating signal to said horizontal synchronizing signal by comparing the horizontal synchronizing signal and a horizontal oscillation signal outputted from the PLL circuit, a plurality of
The input terminal accepts only video signals from computer signals.
The first input terminal to be input and the general video signal only
A second input terminal to be connected to the
And a third video signal to which one of the video signal and the general video signal is selectively inputted.
An input terminal, and the selection circuit has a first input terminal and a third input terminal.
To control which input terminal is selected
Circuit, and the control circuit is connected to a third input terminal.
The video signal from the computer signal or the general video signal.
In addition to managing user settings for inputting, the selection circuit
When switching control is performed to select the first input terminal, water
The first mode in which the flat oscillation signal follows the horizontal synchronization signal
Control to operate the horizontal frequency tracking circuit
Switching control so that the selection circuit selects the second input terminal.
In this case, a fixed voltage is supplied to the voltage-controlled oscillator to
Let's use the second mode where the flat oscillation signal has a fixed frequency.
Control to make the horizontal frequency tracking circuit inoperative,
Switching control is performed so that the selection circuit selects the third input terminal.
At this time, the first mode and the second mode are set according to user settings.
Horizontal frequency tracking so that either mode
A computer whose frequency is stable because it controls the slave circuit.
Both video signals (PC video signals) and general video signals having an unstable frequency can be handled, and a good image can be displayed in any case. Further
In addition, the control circuit sets the mode in conjunction with the switching control of the selection circuit.
Is switched, so that the input video signal is
It is necessary to determine whether the signal is an image signal or a general video signal.
Absent. In addition, the control circuit that manages user settings
The mode is switched according to the setting, so the mode is
You do not have to choose a code.

[Brief description of the drawings] FIG. 1 is a block diagram showing one embodiment of the present invention. FIG. 2 is a flowchart showing the operation of the present invention. FIG. 3 is a block diagram showing a conventional example. [Explanation of symbols] 1 microcomputer (horizontal frequency tracking circuit) 2 PLL circuit 3A to 3D input terminal 4 Selection circuit 5 Sync separation circuit 6. Host CPU (control circuit) 21 Voltage controlled oscillator

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G09G 1 / 00,5 / 00-5/42 H04N 3 / 27,5 / 46

Claims (1)

(57) [Claims] (1) A plurality of input terminals having a plurality of signal formats,
A selection circuit that selects a video signal input from the input terminal, a synchronization separation circuit that separates a horizontal synchronization signal from a video signal input from the input terminal selected by the selection circuit, and a voltage-controlled oscillator, PL that oscillates horizontally by the horizontal synchronization signal separated by the synchronization separation circuit
And L circuit, in a display apparatus having a horizontal frequency tracking circuit to follow the horizontal oscillating signal to said horizontal synchronizing signal by comparing the horizontal synchronizing signal and a horizontal oscillation signal outputted from the PLL circuit, wherein Multiple input terminals are connected to video signals
Signal input to the first input terminal
To the second input terminal to which the
One of the video signal and the general video signal
A third input terminal, wherein the selection circuit is connected to any one of the first to third input terminals.
A control circuit is provided to switch between selecting the input terminal of
The control circuit includes a video signal based on a computer signal input to the third input terminal.
User settings to input either
Control and switching control so that the selection circuit selects the first input terminal.
In this case, the horizontal oscillation signal is added to the horizontal synchronization signal.
Follow the horizontal frequency so that the first mode
Controlling the circuit to operate, and switching the selection circuit to select the second input terminal.
When controlled, a fixed voltage is supplied to the voltage-controlled oscillator.
And a second mode for supplying the horizontal oscillation signal to a fixed frequency.
The horizontal frequency tracking circuit is disabled so that the
And the selection circuit switches to select the third input terminal.
When controlling, according to the user setting, the first
Mode or one of the second modes.
Controlling the horizontal frequency tracking circuit as described above .