JPH0120595B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a television receiver capable of displaying channel numbers, characters, etc. in patterns on a cathode ray tube screen.

(b) Prior Art In recent years, television receivers that use a remote control device to change channels and set the volume have been on the market. Although it is possible to switch channels and set the volume from a separate location, it is difficult to see the channel numbers and volume setting level, so each time you switch channels or set the volume, for a short period of time, the number of the channel being received or the volume level being set is displayed. A television receiver has been proposed in which a display is projected on a cathode ray tube screen.

In order to display channel numbers and volume levels as described above, the display pattern stored in the memory of the display IC must be read out according to the data specified by an external device (for example, a control microcomputer). At this time, it is output on the screen based on oscillation pulses from the horizontal oscillation circuit and vertical oscillation circuit inside the television receiver. Specifically, as shown in Figure 5, the horizontal oscillation pulse ( _PH )
After the fall of [the pulse (P _H ) period corresponds to the horizontal blanking period], the number of clock pulses is counted in the display device for a predetermined period (T ₁ ), and the upper left of the pattern displayed on the CRT screen 1 is counted. Determine the horizontal position of the corner and also the vertical oscillation pulse ( _PV )
After the fall of [the pulse ( _PV ) period corresponds to the vertical blanking period], the vertical position is determined by counting the number of horizontal oscillation pulses during a predetermined period ( _T2 ). In this way, a predetermined display pattern (in FIG. 5, the channel number "8" is displayed on the screen) is displayed on the screen 1. Normally, the pattern is the image projected on the screen. It is normal to display it in the corner of the CRT screen so that it does not interfere with the viewing experience.

By the way, when a synchronizing signal is input, the horizontal and vertical oscillation frequencies of a television receiver oscillate at a frequency synchronized with the synchronizing signal, and normally the horizontal frequency is 15.75KHz and the vertical frequency is 60Hz. If there is no input, self-oscillation is performed at a frequency determined by the circuit constants of the horizontal oscillation circuit and vertical oscillation circuit. In this case, the fluctuation of the vertical oscillation frequency is particularly large compared to when oscillating with a synchronous signal.
It drops to about ~53Hz. Note that the case where no synchronization signal is input means, for example, when a composite video signal is not supplied from a video tape recorder.
This is the case when the television receiver is set to video mode.

When the vertical oscillation circuit performs synchronous oscillation as described above, the period of the vertical oscillation pulse becomes as shown in Figure 6B, and the image is formed by scanning within the range shown by the broken line in Figure 6C. However, when the synchronization signal is not input, the period of the vertical oscillation pulse becomes as shown in Fig. 6A, and the overscan amount increases, and the
An image is formed by scanning within the range indicated by the dashed line in FIG. As can be seen from this figure, the amount of overscanning is especially large in the vertical direction (up and down direction of the screen), so even if the mode "Video" is displayed in the upper right corner of the screen during synchronous oscillation,
During asynchronous oscillation, the displayed text "Video" would be displayed shifted upwards on the screen, and there was a risk that part of the text would protrude from the effective screen (indicated by the solid line) and would not be displayed. In addition, in consideration of the amount of overscan during asynchronous oscillation, display characters, channel numbers, etc. may be set in advance to be displayed at the center of the CRT screen 1 (indicated by the two-dot chain line). This is possible, but in that case it would interfere with viewing the video screen and would be visually undesirable.

Further, although Japanese Patent Publication No. 10108/1988 describes a channel display device that projects channel numbers on a cathode ray tube screen, it does not describe any means for solving the above-mentioned problems.

(c) Object of the Invention The object of the present invention is to provide a television receiver devised to solve the above-mentioned problems with a simple configuration.

(D) Structure of the Invention The present invention includes a vertical/horizontal oscillation circuit that oscillates at a frequency synchronized with the synchronization signal when a synchronization signal is input, and performs self-oscillation when the synchronization signal is not input. After inputting the horizontal oscillation pulse from the oscillation circuit, the horizontal position of the pattern displayed on the cathode ray tube screen 24 is determined by counting the number of clock pulses corresponding to the horizontal display position data, and the vertical oscillation pulse from the vertical oscillation circuit is determined. After inputting , the vertical position of the pattern displayed on the cathode ray tube screen 24 is determined by counting the number of horizontal oscillation pulses corresponding to the vertical display position data, and the vertical position of the pattern displayed on the cathode ray tube screen 24 is determined. In a television receiver configured to display a pattern, synchronization signal detection means 18 and 29 detect the presence or absence of the synchronization signal, and the value of the vertical display position data is determined by the output of the synchronization signal detection means 18 and 29. The present invention is characterized in that it includes display position changing means 23 and 27 for changing the pattern so that the pattern is displayed at a substantially constant position on the cathode ray tube screen 24 regardless of the presence or absence of the synchronization signal.

(E) Embodiment FIG. 1 is a block diagram of a television receiver embodying the present invention. In this figure, 2 is an antenna, 3 is a tuner, 4 is an intermediate frequency amplification circuit, 5 is a video detection circuit, and 6 is a block diagram of a television receiver in which the present invention is implemented. A video amplification circuit, 7 a luminance signal amplification circuit, 8 a cathode ray tube, 9 a color signal circuit, 1
0 is a synchronous circuit, 11 is a horizontal and vertical oscillation circuit, 1
2 is an audio intermediate frequency amplification circuit, 13 is an audio detection circuit, 14 is an audio amplification circuit, 15 is a speaker, 16
17 is a channel selection device, 17 is a broken shape shaping circuit, 18 is a synchronization signal detection circuit, and 19 is a screen display circuit.The present invention is characterized by the configurations of this synchronization signal detection circuit 18 and screen display circuit 19, and is as follows. An example will be explained regarding this part. The waveform shaping circuit 17 is provided to convert the signals obtained from the vertical and horizontal oscillation circuits into pulse signals of appropriate voltage levels and supply the pulse signals to the screen display circuit 19.

FIG. 2 is a book diagram schematically showing the main parts of FIG.
2 is a display position controller that outputs display position data 25 for projecting a display pattern from the screen display device 21 to a predetermined position on the cathode ray tube screen 24; The controller 20 and the display position controller 23 can be constituted by a one-chip microcomputer (hereinafter referred to as "microcomputer") for control, which will be described later and is also used as a channel selection device. Clock pulses from a clock oscillation circuit 26 are input to the screen display device 21, and the clock pulses input after the fall of the horizontal oscillation pulse (the width of which corresponds to the horizontal blanking period) are counted for a predetermined period. Therefore, the horizontal position of the display pattern is determined, and the vertical position of the display pattern is determined by counting the number of horizontal oscillation pulses after the fall of the vertical oscillation pulse (the pulse width corresponds to the vertical blanking period). Determine the position of the direction. 18 is a synchronization signal detection circuit that detects the presence or absence of a synchronization signal based on the flyback pulse, the horizontal synchronization signal, and the AFT voltage; when the detection circuit 18 does not detect a synchronization signal, the output of Thus, the vertical display position of the display pattern on the cathode ray tube screen is set at a position shifted toward the center of the screen.

FIG. 3 is a circuit diagram showing the configuration of FIG. 2 more specifically, and 27 is a one-chip microcomputer for control [manufactured by Matsushita Electronics Co., Ltd.].
MN1415], and the microcomputer 27 has the functions of the above-mentioned display data controller 20 and display position controller 23 in addition to the channel selection function depending on the program. 28 is a display IC (manufactured by Matsushita Electronics Co., Ltd.: MN1277B), which functions as the screen display device 21. 26 is the display IC2
A clock oscillation circuit is connected to the 27th pin and the 28th pin of 8, and 29 is a synchronization detection IC that operates as the synchronization signal detection circuit 18 [manufactured by Tokyo Sanyo Electric Co., Ltd.]
LA7912].

Next, the operation of the microcomputer 27 will be explained with reference to the flowchart of FIG.

For example, if the channel is to be changed, the microcomputer 27 sets data for determining the vertical position of the display pattern on the cathode ray tube screen. At this time, the vertical position data set in the microcomputer 27 is set to a data value when a synchronizing signal is input. On the other hand, IC29 for synchronization detection
The flyback pulse is supplied to the 1st pin, the horizontal sync signal is supplied to the 2nd pin, and the AFT voltage is applied to the 8th pin to detect the presence or absence of the sync signal, and when the sync signal is input. Either the 6th pin and 7th pin both output a high level, or one of them outputs a high level, thereby causing the 24th pin of the microcontroller 27 and
When a high level is supplied to at least one of pins 25 and 25, the microcomputer 27 determines that a synchronization signal has been input, sets the horizontal display position data, and displays it together with the previously set vertical display position data. As position data, the 4th pin, 26th pin, 27th pin, 31st pin, 32nd pin, 33rd pin, 34th pin, 35th pin,
Corresponding display IC28 from pin 36
Provide parallel data to pins 2 to 8, 17, and 18. These parallel data are output from the 5th pin of the microcontroller 27 and read at the rising and falling edges of the signal applied to the 12th pin of the display IC 27, and a display pattern is projected at the position specified by the data. do. In addition, pins 20 and 21 of display IC 28
From pin number 22, R (red) and G respectively.
(green) and B (blue) signals are output, and a blanking signal for blanking the video signal of the part where the display pattern is projected is output from pin 24.
In addition, a horizontal oscillation pulse is input to pin 24,
Vertical oscillation pulses are input to pin 25.

On the other hand, when the synchronization signal is not input, a low level is supplied to both the 24th pin and the 25th pin of the microcomputer 27.
Step 7 changes the value of the previously set vertical display position data. Specifically, the display IC 28 can specify the vertical position of the display pattern in 64 steps, and one step corresponds to 4 counts of horizontal oscillation pulses. If not, add a difference of 5 steps (i.e. 1.25μs).
(by delaying the display start time of the display pattern in the vertical direction) to correct the display position shift.

In the embodiment described above, the deviation of the display position on the screen is corrected by changing the value of the vertical display position data within the microcomputer.

(F) Effects of the Invention According to the present invention, in a television receiver that displays channel numbers and characters on a cathode ray tube screen, channel numbers and characters are always displayed at a fixed position on the screen regardless of the presence or absence of a synchronization signal. etc., the display position shift can be corrected by simply changing the vertical display position data. Therefore, no additional circuit such as a delay circuit for delaying the vertical oscillation pulse is required.

[Brief explanation of drawings]

1 to 4 relate to an embodiment of the present invention,
Fig. 1 is a block diagram showing the outline of a television receiver, Fig. 2 is a schematic configuration diagram, Fig. 3 is a diagram showing a specific example of its circuit, and Fig. 4 is a flowchart for explaining the operation. It is a diagram. Figure 5 is a diagram for explaining how to set the display position of the display pattern.
FIG. 6 is a diagram for explaining the conventional drawbacks. 24... Braun tube screen, 18... Synchronization signal detection circuit (synchronization signal detection means), 29... Synchronization detection IC (synchronization signal detection means), 23... Display position controller (display position changing means), 27... Microcomputer (display position changing means).

Claims (1)

[Claims] 1. A vertical/horizontal oscillation circuit that oscillates at a frequency synchronized with the synchronization signal when a synchronization signal is input, and performs self-excited oscillation when the synchronization signal is not input; The horizontal position of the pattern displayed on the cathode ray tube screen 24 is determined by counting the number of clock pulses corresponding to the horizontal display position data after inputting the horizontal oscillation pulse from the vertical oscillation circuit, and after inputting the vertical oscillation pulse from the vertical oscillation circuit. The vertical position of the pattern displayed on the cathode ray tube screen 24 is determined by counting the number of horizontal oscillation pulses corresponding to the vertical display position data, and the pattern is displayed at a predetermined position on the cathode ray tube screen 24. A television receiver configured to include: synchronization signal detection means 18, 29 for detecting the presence or absence of the synchronization signal; and the value of the vertical display position data is changed by the output of the synchronization signal detection means 18, 29. A television receiver comprising display position changing means 23 and 27, so that the pattern is displayed at a substantially constant position on the cathode ray tube screen 24 regardless of the presence or absence of the synchronization signal.