JPH0145181Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field This invention relates to a color television receiver that displays channel numbers and the like within the screen.

BACKGROUND ART AND PROBLEMS A color television receiver in which channel numbers are displayed on the screen is configured as shown in FIG. 1, for example.

That is, in FIG. 1, reference numeral 1 indicates an electronically tuned tuner, to which a tuning voltage is supplied from the tuning control circuit 7, a desired channel is tuned, and the video intermediate frequency signal of that channel is extracted. It will be done. This signal is then supplied to a video detection circuit 3 through a video intermediate frequency amplifier 2, where a negative synchronous polarity composite color video signal Sc is demodulated, and this signal Sc is supplied to a synthesis circuit 4, which will be described later.

Further, a signal indicating the selected channel is extracted from the control circuit 7 for a certain period of time from the time of the channel selection operation, and is supplied to the pattern forming circuit 8. A pulse Pn displayed as a channel number (pattern) is generated for a certain period of time from the time of the channel selection operation, and this pulse Pn is supplied to the synthesis circuit 4 and synthesized into the signal Sc.

In this way, the signal Sc having the pulse Pn is taken out from the synthesis circuit 4 for a certain period of time from the time of the channel selection operation. This signal Sc is then supplied to the color video circuit 5 where it undergoes color demodulation and the like to become three primary color signals, which are then supplied to the color picture tube 6.
Therefore, when a channel selection operation is performed, the desired channel is selected and the image of that channel is displayed on the picture tube 6, and the image of that channel is superimposed on this for a certain period of time from the time of the channel selection operation. The channel number of the selected channel is displayed in white on the picture tube 6.

In this case, the synthesis circuit 4 is configured as follows. That is, the signal Sc from the detection circuit 3 is supplied to the base of the transistor _Q1 , its emitter is grounded through the diode _D1 and the resistors _R1 to _R3 , and its collector is connected to the power supply terminal _T1. . Also, the emitter of transistor Q ₁ is connected to the base of transistor Q ₂ through resistor R ₄ , and its emitter is grounded through resistor R ₅ and peak hold capacitor C ₁ , and its collector is connected to terminal T ₁ . Connected.

Furthermore, between terminal T ₁ and ground, a resistor R ₆ ,
R ₇ are connected in series, the midpoint of the connection is connected to the base of the transistor Q ₃ , the pulse Pn is supplied from the forming circuit 8 to this base through the capacitor C ₂ , and the collector of the transistor Q ₃ is connected to the base of the transistor Q ₂ . The emitter is connected to the midpoint between resistors R ₁ and R ₂ .
Further, the midpoint between the resistors R ₂ and R ₃ is connected to the video circuit 5 through the emitter follower transistor Q ₄ .

Therefore, since the transistor _Q1 works as an emitter follower, the signal Sc from the detection circuit 3 is
Transistor Q ₁ → Diode D ₁ → Resistor R ₁ , R ₂
→It is supplied to the video circuit 5 through the line of transistor _Q4 . Also, at this time, the transistor
If the base potential of Q ₂ is higher than the emitter potential, transistor Q ₂ acts as an emitter follower, and vice versa, if it is lower, transistor Q ₂
is turned off, so the white peak level of the signal Sc is held in the capacitor _C1 .

Then, when pulse Pn is supplied to transistor Q ₃ , transistor Q ₃ turns on, so the white peak level voltage held in capacitor C ₁ passes through transistor Q ₃ to resistors R ₁ and R ₂ . Supplied to the connection midpoint. Therefore,
At this time, the pulse Pn is synthesized with the signal Sc at the white peak level, and this pulse Pn
The synthesized signal Sc is supplied to the video circuit 5.

Note that when the pulse Pn is not supplied to the transistor Q ₃ , the transistor Q ₃ is off, so only the signal Sc from the detection circuit 3 is supplied as is to the video circuit 5 as described above.

In this way, in the circuit shown in FIG. 1, the channel number is superimposed on the broadcast screen and displayed in white for a certain period of time after the channel selection operation, but in this case, the forming circuit 8 is generally a logic circuit, a character generator, etc. Since the pulse Pn is formed by these, the edge of the pulse Pn is extremely steep and contains many harmonic components. and,
Since the transistor _Q3 is switched by such a pulse Pn, when the pulse Pn is combined with the signal Sc, the edge of the pulse Pn becomes extremely steep and contains many harmonic components. Among these harmonic components, the harmonic components in the band of the carrier color signal are mixed into the color signal system in the video circuit 5, so that on the screen, the color appears at the edge of the channel number displayed in white. In other words, cross-color interference occurs.

Purpose of the invention This invention attempts to solve the problems mentioned above.

Summary of the invention This invention is a color television receiver that displays patterns such as channel numbers and bars on the screen of a color picture tube using signals formed in a pattern forming circuit. A color television receiver that displays the pattern by combining the signals into a composite color video signal, and is provided with a filter circuit for removing at least a color subcarrier frequency component in the signal line of the signal displayed as the pattern. be.

Therefore, when channel numbers and the like are displayed, it is possible to prevent cross-color interference from occurring.

Example In FIG. 2, the formation circuit 8 and the capacitor C ₂
A trap circuit 11 whose trap band is the band of the carrier color signal is provided on the pulse Pn signal line between the two. In this example, trap circuit 1
1 is a resistor R ₁₁ connected in series with the signal line
and a series circuit of a coil L ₁₁ and a capacitor C ₁₁ connected in parallel on the output side.

With this configuration, even if the pulse Pn from the forming circuit 8 is steep and contains harmonic components, the band component of the carrier color signal among these harmonic components is removed by the trap circuit 11. , the waveform of the pulse Pn supplied to the transistor Q ₃ is rounded, and the pulse Pn supplied to the transistor Q ₃ is
The band component of the carrier color signal is no longer included by the trap circuit 11, and accordingly, the pulse Pn synthesized with the signal Sc also no longer contains the band component of the carrier color signal. There is no coloration, that is, cross-color interference can be prevented.

Moreover, the configuration for that purpose is the trap circuit 11.
All you have to do is add , which is both simple and inexpensive.

Note that in the above description, a similar low-pass filter may be used instead of the trap circuit 11. In addition to channel numbers, this is also effective when displaying volume as a bar, for example.

Effects of the invention When channel numbers, etc. are displayed, it is possible to prevent cross-color interference from occurring.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining this invention, and FIG. 2 is a connection diagram of an example of this invention. 11 is a trap circuit.

Claims (1)

[Claims for Utility Model Registration] Comprising a video detection circuit, a synthesis circuit, a color video circuit, a color picture tube, and a pattern forming circuit for forming pulses displayed as patterns such as channel numbers and bars, In the synthesis circuit, pulses formed in the pattern forming circuit are synthesized with the composite color video signal obtained from the video detection circuit, and this synthesized signal is converted into three primary color signals in the color video circuit, and then the pulses are converted into three primary color signals in the color video circuit. In a color television receiver in which the pattern is supplied to a picture tube and displayed on the screen of the color picture tube, at least a carrier color signal is connected to the pulse signal line from the pattern forming circuit to the synthesis circuit. A color television receiver equipped with a filter circuit that removes band components.