JPS6048758B2 - Picture tube drive circuit - Google Patents

Description

[Detailed description of the invention] The present invention relates to a picture tube drive circuit.

FIG. 1 shows a picture tube drive circuit of a television receiver.

In this picture tube drive circuit, a luminance signal (hereinafter referred to as the Y signal) is input to the emitter of the transistor Q, and a color difference signal, for example, the R-Y signal, is input to the base of the transistor Q. The signal appears at , is supplied to the picture tube 11 from the collector of the transistor Qll, and is displayed.
In addition, in FIG. 1, 12 is a power supply. In the case of the above configuration, since the frequency characteristics of the final stage transistors Q, , are poor, compensation is usually made by increasing the frequency characteristics of the signal itself. Incidentally, in recent years, apart from the original television broadcast program, signals indicating characters, figures, graphs, etc. (hereinafter collectively referred to as characters) have been input to television receivers from external display systems. , character display devices that display this on a picture tube are being actively developed.

When inputting a signal from this character display device to a television receiver, the input signal pattern may be a pattern in which the high frequency signal (RF) is input as is, a pattern in which it is input as a video signal, or a pattern in which the signal is input as a Y signal, a primary color signal, and synchronization. There are patterns etc. that are input as signals. RF
Alternatively, when inputting as a video signal, if the display frequency is high, dot interference will occur due to the influence of color subcarriers.
Furthermore, even if the Y signal and primary color signals are simply converted and input, the picture tube drive circuit shown in Figure 1 has problems such as blurred display and blurred colors due to the poor frequency characteristics of the transistors Q. arise. Furthermore, since the primary color signals and Y signals output from the character display device are generally TTL (transistor-transistor logic) level digital signals, in order to input them to the picture tube drive circuit as shown in Figure 1, they must be analog signals. It is necessary to convert it into a signal that can be input to the circuit. In this case, if the frequency characteristics of this conversion circuit are poor, the phenomenon of display blurring and color blurring becomes worse. This invention was made in order to deal with the above-mentioned circumstances, and has excellent frequency characteristics, and does not cause color bleeding or image distortion.
It is an object of the present invention to provide a picture tube drive circuit that does not cause an image to become blurred.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 2 is a circuit diagram of the picture tube drive circuit.

In FIG. 2, 21 is an input terminal to which a TTL level Y signal is applied, and this input terminal 21 is connected to the inverter circuit 2.
For example, an inverter circuit (ΠL integrated circuit) 23 having an open collector output configuration in the waveform shaping circuit 22 for 3A and Y signals.
B and resistance R2,,R. . transistor Q
It is connected to the emitter of 2. This transistor Q
The collector of 2 is connected to a power supply terminal 24 to which a positive potential V is applied, and the base is connected to the slider of a variable resistor 25 inserted between the power supply terminal 24 and the reference potential terminal. Reference numeral 26 denotes an input terminal to which a digitized primary color signal, for example, an R signal, is applied. .

3.R.

. sequentially through the positive potential V. is connected to a power supply terminal 29 to which is applied. The resistors R2, , R2. connection midpoint a
is the transistor Q22 constituting the level shift circuit 30
is connected to the base of this transistor Q2.
2 and a mixed amplification transistor Q having a common base. . connected to the base of On the other hand, the resistance R. . ,R. . The connection midpoint b is the transistor Q of the level shift circuit 30.
. connected to the base of. In the level shift circuit 30, the collector of a transistor Q22 is connected to the power supply terminal 24, and the emitter is connected to three diodes Dm and D.

. , D23 through the forward series connection of transistor Q2.
It is connected to the base of 5. This transistor Q25
The base of is connected to the reference potential terminal via the resistor R25,
The emitter is diode D. , in the opposite direction to the transistor Q. . The collector is connected to the reference potential terminal. Transistor Q. . The collector of is connected to the reference potential terminal, and the emitter is resistor R. . is connected to the emitter of transistor Q23 via. The collector of the transistor Q23 is connected to the emitter of the output transistor QI, which has a grounded base.
5, the base is at a positive potential V. is connected to a power supply terminal 31 to which V is applied, and the collector is connected to a positive potential V through a load resistor R2.
. It is connected to the power supply terminals 3 and 2 to which is applied, and is also connected to the cathode of the picture tube 33. In addition, in the figure R
, G, and B axes, only the R axis is shown, but since the other two axes are constructed in the same manner, the explanation of these two axes will be omitted.

However, in this case, the input terminal 21, the Y signal waveform shaping circuit 22, and the transistors Q22 and Q of the level shift circuit 30
. , diode D. ,,D. . , D23, resistance R5 is 3
Commonly used for axes. The operation in the above configuration will be explained.

Since the Y signal and the R signal are TTL level digital signals as described above, in order to enable input to the analog circuit, the inverter circuit 2 which is a TTL integrated circuit as described above is used.
3,28.

First, to explain the Y signal input system, this Y signal is '
When the level is '1', the inverter circuit 23A is 'o'
', the inverter circuit 23B is turned off, and the voltage obtained by dividing the power supply voltage V1 by the variable resistor 25 is applied to the bases of the transistors Q22 and Q23.

A voltage Va lowered by the base-emitter voltage VD (in the following description, the forward drop voltage of the diode is also referred to as VD) is applied. On the other hand, when the Y signal is at the ``0'' level, the inverter circuit 23A becomes ``1'', the inverter circuit 23B is turned on, and the transistors Q22,
The base of Q23 has a power supply voltage V and a resistor R. , , R2 is applied with a divided voltage Vb. Next, the R signal input system will be explained.

When this R signal is at the "O" level, the inverter circuit 28 is turned off. In this case, the base of the transistor Q2 is 2V higher than the base voltage of the transistors Q22 and Q23.
It is held at a voltage (Va-2VD) or (Vb-2VD) lowered by D. This is transistor Q. The base of transistor Q is connected between the base and emitter of transistor Q22 by diodes D2l, D22, and D23.
. ,Q. The base voltage of transistor Q2 is set to a voltage that is 4 VD lower than the base voltage of transistor Q2, and the base voltage of transistor Q2 is set to a voltage that is 2 VD higher than the base voltage of transistor Q25 by diode D24 between the base and emitter of transistor Q25. It is from. On the other hand, the R signal is '“
1'' level, the base voltage of the transistor Q2 is the power supply voltage V2 and the resistor R2. , the value Vc divided by R23
is set to Here, the operation will be explained in more detail with reference to Tables 1 and 2 and the signal waveform diagrams of FIGS. 1 to 6, which are listed at the end of the detailed description of the invention. For example, Table 1 shows the input pattern of the Y signal and R, G, B signals to the picture tube drive circuit at the character display position when the character display is a character display. In this case, the Y signal input is ``1''. '
The display colors are R, G, as shown in 7 to 9.
Depends on the selection of the B signal. In addition, Table 2 shows the input pattern in the background area other than the character display position, and in this case, the Y signal is at the ``O'' level. is the transistor Q.,Q
, and the horizontal axis shows time t. First, to explain the part shown as 1 in FIG. 3, since both the Y signal and R signal are at the ``0'' level in this part,
Transistors Q23 and Q2. The difference in base voltage is 2VD
So, transistor Q. . ,Q. ,,Q. . is turned off, and transistor Q is turned off. . The collector of is supplied with the power supply voltage V,
appears. In this state, the Y signal is at ``0'' level, so the background color is output, and ◎, ? in Table 2. As shown in 1, the background color is determined by the output states of the other two axes. However, in this case, in state 9, the screen becomes black and nothing is displayed. Next, the part shown as 2 in FIG. 3 will be explained. Since both the Y signal and the R signal are at the ``1'' level in this part, it is the transistor Q2.

and Q. 2. The difference in base voltage of is (Va-Vc).
In this state, the Y signal is at the "1" level, so the specified color is output, and for example, when characters are displayed on the screen.The displayed color at this time is determined according to the output state of the other two axes. It is determined to be one of 7, 4, 4, [phase] in Table 1.Next, to explain the part shown as 3 in Fig. 3, in this part, the Y signal and R signal are respectively ``o'' level, ''
1'' level, so the transistor Q. . and Q2.
The difference between the base voltages of the transistors Q23 and Q is (Vb-Vc). ,,Q. 6 turns on, transistor Q.

6 collector voltage decreases.

This state is a state in which the background color is output because the Y signal is at the ``0'' level, and corresponds to when, for example, parts other than characters are displayed on the screen. The display color at this time is determined as 7, 4, 4, or [phase] in Table 2 according to the output states of the other two axes. Next, to explain the part shown as 4 in FIG. 3, since the Y signal and R signal in this part are at the ``1'' and ``o'' levels, respectively, the base potential of the transistor Q2 is It changes following the base potential of transistor Q23, and the voltage difference between the two becomes 2VD.

In this state, the Y signal is at the ``1'' level, so the specified color is output, and the R signal is at the ``0'' level, so the displayed color is determined to be ◎, 7, or 1 in Table 1. If the signals of the other two axes are also at the ``0'' level, the characters are displayed in black according to 9 in Table 1. Like this 4, the Y signal is ''
1'' level, and when the R signal is at ``0'' level, transistor Q2.

The base potential of is shifted by the level shift action of the level shift circuit 30. As a result, transistor Q2
3 base potential and transistor Q2. The difference between the base potential and the base potential becomes 2VD, and the transistor Q23 is turned off. Therefore, when the Y signal is at the "1" level, the picture tube 33
The R signal is not mixed in, the frequency characteristics of the circuit are improved, and there is no color bleeding or blurring of the image. Next, to explain the part shown as 5 in FIG. 3, in this part, the Y signal and R signal are respectively 440,...
4th 1,,i441,,,440,,4440,,,4
41,... This shows the state changing from 3-4 to 3 as mentioned above on the screen. That is, in the part 5a of 5, 7, 4, ? of Table 2. , [Yes], the background is displayed in color, and the part 5b is ◎, ? in Table 1. , 1, 9, for example, characters are displayed in color. In this case as well, when the Y signal goes to the ``1'' level, the base waveform of the transistor QM follows the base waveform of the transistor Q23 and rises rapidly, and when the Y signal returns to the ``0'' level,
fall rapidly.

Therefore, when the Y signal is at the '1' level, the picture tube 3
3, the R signal is not mixed in, the frequency characteristics of the circuit are improved, and there is no color bleeding or blurring of the image. Next, to explain the part shown as 6 in FIG. 3, in this part the Y signal and R signal are respectively 440, .
,No.4 1,,0441,,,“1,,0440,,,4
This shows the state changing from 3-2 to 3 as mentioned above on the screen.

In other words, in the part 6a of 6, 7, 4, ? , the background is displayed in color according to [phase], and in the part 6b, 7 in Table 1 is displayed.
,4,4,For example, characters are displayed in a color according to [phase],
At part 6c, the state returns to 6a again. This embodiment described in detail above has the following effects.

First, when the R signal is not input (R signal ``0'' level), the Y signal is either ``0'' level or ``1'' level. level, the base voltage of transistor QM is 2V higher than the base voltage of transistor Q23.
The transistor Q is held at a value lowered by D.

. ,Qm,Q. . is in an off state, and no R signal is mixed into the picture tube 33. Therefore, when displaying a character using at least one of the G and B axes, the frequency characteristics of the circuit are improved without blurring the color or blurring the image due to the inclusion of red. This is true not only when the R signal is not input, but also when the other two axes signals are not input, or when characters are displayed in black without inputting all three axes signals.Also, Mixed amplification transistor Q.

A grounded base type transistor Q with excellent frequency characteristics is used to supply the character signal mixed and amplified by the transistor Q to the picture tube 33.

. The frequency characteristics of the circuit are excellent due to the fact that the circuit is supplied via a simple circuit configuration and there is little frequency attenuation, making it possible to prevent problems such as color blurring and image blurring as much as possible. Note that the present invention is not limited to the above embodiments, and the point is that when no R (or G, B) signal is input, the emitter voltage of the mixed amplification transistor is changed to its base voltage so that the mixed amplification transistor is turned off. It suffices to have a configuration that allows the change to follow. FIG. 4 shows a picture tube drive circuit portion of a television receiver having the above-mentioned picture tube drive circuit and a picture tube drive circuit for original television signals.

In FIG. 4, the same parts as in FIG. 2 are given the same reference numerals, and R, G, B3 $111 is shown for both the television signal system and the character signal system. First, in the character signal system, 41 and 42 are input terminals for G and B signals, respectively, 43 and 44 are waveform shaping circuits, and Q. ,,Q
．． . and D, , D, 2 constitute level shift circuits for the G and B axes, respectively. transistor and diode, Q
,. ,Q. . and R. ．． ,R. . are a mixed amplification transistor and a resistor on the G and B axes, respectively. Next, to explain the original television signal system, 45 is a Y signal input terminal, 46 is a Y signal amplification circuit 47, 48, 49 is a color difference signal (R-Y), (G-Y), ( B-Y) demodulation circuit, Q,.

,Q. ,Q. , are the Y signal and color difference signal (R-Y), respectively.
, (G-Y), and (B-Y). Also, Q. ,,Q. , and R.

. ,R. , are the output transistors and load resistances of the G and B axes, respectively, and the output transistor Q of the three axes. . ,Q,,,
Q. 9. Load resistance R. ,,R. 3, R. , are used for both the character signal system and the television signal system. Output transistor Q26, Q. 3.Q.

, a switching circuit 50 is inserted in front of the output transistors QI, Q. 8, Q. The character signal and television signal for 9 are switched. In other words, the transistors Q5O (5Q5, , Q52 and Q53, Q
, , and Q55 are supplied with R-axis, G-axis, and B-axis signals of the television signal, respectively. Also, transistors Q56 and Q5, , Q, and 8 and Q form a differential pair. ，
Q. The R-axis, G-axis, and B-axis signals of character signals are supplied to the common emitters of O and Q6l, respectively. Therefore,
Now, when the selector switch 51 is short-circuited, the transistors Q, , Q5. ,Q. . is turned on, and the signals of each axis of the television signal are transmitted through transistors Q8 and Q5, .
Q63 and Q3, Q6. and Q. , through the output transistor Q. . ,Q,8,Q. , is supplied to Conversely, when the selector switch 51 becomes open, the transistor Q5
,, Q59, Qm are turned on, and the signals of each axis of the character signal are output to the output transistors Q26, Q. ,,Q. . is supplied to In the switching circuit 50, Q is a transistor, C is a capacitor, R is a resistor, 52 is an inverter circuit,
Dz is a Zener diode, and 53 and 54 are power supply terminals. By using such a switching circuit 50, it is possible to realize a picture tube drive circuit that can be used for both the original television signal and character signals while leaving the original picture tube drive circuit for the television signal unchanged. FIGS. 5 and 6 are block diagrams schematically showing a device in which a television receiver and a character display device are integrated.

That is, what is shown in FIG. 5 is a television receiver capable of receiving television text multiplex broadcasts and television still image multiplex broadcasts. In FIG. 5, 61 is a television signal receiving circuit, 62 is a multiplex broadcast receiving circuit that extracts characters and still image signals (character signals) superimposed on the television signal from the television signal, and 63 is a fourth broadcast receiving circuit. This is the picture tube drive circuit illustrated in the figure. When displaying a text multiplexed still image on a television screen, output the R, G, B, and Y signals in synchronization with the television signal, and input only the Y signal instead of the switch in Fig. 4 51. By doing this, you can insert a still image into the TV screen.

Furthermore, the one shown in FIG. 6 uses a microcomputer, for example, and has an integrated character display device that stores information unrelated to the television signal in a memory in advance and displays this on a picture tube as necessary. This indicates a television receiver capable of receiving satellite broadcasts or a television receiver capable of receiving captain broadcasts. That is, 64 in the figure is a character display unit corresponding to a character signal generating circuit using a microcomputer or the like or a receiving circuit for captain broadcasting. In addition, when displaying on a television receiver from this character display unit, Y, R, G
, B signals, a synchronization signal can be input, and display can be performed by switching to the synchronization signal of the television signal. As described above, according to the present invention, the frequency characteristics are excellent, and
It is possible to provide a picture tube drive circuit that does not cause color bleeding or blur images.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing a conventional picture tube drive circuit, Fig. 2 is a circuit diagram showing an embodiment of the picture tube drive circuit according to the present invention, and Fig. 3 explains the operation of the circuit shown in Fig. 2. 4 is a circuit diagram showing an example of the configuration when the picture tube drive circuit of the present invention is added to the picture tube drive circuit of a television receiver, and FIGS. 5 and 6 are respectively shown in FIG. FIG. 4 is a schematic block diagram of a television receiver having a picture tube drive circuit as shown in FIG. 4; 30... Lebel shift circuit, 33... Picture tube, Q.

Claims (1)

[Claims] 1 Provided for each axis of R (red), G (green), and B (blue), a digitized luminance signal is applied to the base, a digitized primary color signal of the corresponding axis is applied to the emitter, and the collector receives the image. A mixed amplification transistor connected to the tube side,
Provided for each axis of R, G, and B, the emitter potential of the mixing amplification transistor is changed to follow its base potential so that the corresponding mixing amplification transistor is turned off when the primary color signal of the corresponding axis is not input. A picture tube drive circuit equipped with a level shift circuit.