JPS58207782A - Signal clamping device - Google Patents

Abstract

PURPOSE:To decrease the number of pin terminals, by having only to use one capacitor for a clamping filter so as to clamp the pedestal of plural analog signals, in a signal clamping device used for a television receiver. CONSTITUTION:A detecting loop for clamping voltage is provided only for one external primary color signal GTX. To control the power supply of control amplifier circuits 17, 19, 21 of the three systems including the primary color signals RTX, BTX not constituting the detecting loop respectively, the clamping voltage obtained across the clamping filter is applied in parallel as a bias voltage for a current source of the circuits. Thus, only one pin terminal 11 providing a capacitor 43 for the clamping filter at the outside of an IC is required.

Description

[Detailed description of the invention] INDUSTRIAL APPLICATION This invention is used for a television receiver.R,G.

The present invention relates to a signal clamping device that can be used in DC reproduction of the B three primary color signals, and is intended to provide a signal clamping device that can reduce the number of bins when integrated into an IC.

As shown in FIG. 1, in a television receiver, a composite video signal is input to a video input terminal 1, and a video amplification circuit 2. Images are projected onto a cathode ray tube (CRT) 5 via a color signal processing circuit 3 and a video output circuit 4, and additional external devices such as a video tape recorder and a digital converter are also available. When connecting a computer, etc., one word for display on the monitor is input to input terminal 1. However, even if you try to display the image on the I'J 1t-CRT5 when the personal computer comes out, the image quality that can be reproduced is limited by circuits 2 and 3 due to the special nature of the TV video signal, so the image quality is not as high as originally desired. .

Generally, both a composite video signal and primary color signals (R, G, B) are prepared as the video output signal of a personal converter, so using the R, G, and B signals, A method of driving the CRT5 has been considered. An example of a configuration having such a function is shown in FIG.

This includes a switching circuit 7 having means (mechanical or electrical) for switching between the outputs of the conventional television circuits 2 and 3 and R, G, and B signals applied to the input terminal 6 from the outside. The switching circuit 7 allows the TV signal or external R, G, B
I'm trying to choose between a traffic light and a traffic light.

FIG. 3 shows a conventional example of this switching circuit 7 and will be described. R and G of analog signals from external additional equipment.

The B primary color signals RTx, GTx, and BTx are each input into terminals 8, 10.12 after having their direct current cut off by capacitors. In order to perform DC reproduction of the primary color signals RTx, 9Tx, and BTx, three sets of VrC clamp circuits are provided, and these are connected to clamp input circuits 14, 15, 14, 15, and 15, respectively.
16, amplifier circuit 17, 19, 21, pedestal clamp circuit 18, 20, 22, clamp filter one terminal 9,
11.13 to the capacitor 42.43.44. The clamp pulse from the clamp pulse input terminal 3o is supplied to each of the above circuits via the pulse shaping circuit 23. In order to clamp the R, G, B input signals, the above circuit uses [14, 17, 1s:], [15, 19
2o] and [16, 21, 22] have the same circuit configuration, and three clamp filters are also provided individually. The amplifier circuits 17, 19, and 21 are commonly controlled by an external control signal applied from the terminal 32, so that the gain can be changed and the contrast of the externally supplied image can be adjusted. Well, in order to slightly change the DC level based on one clamp circuit (the circuit for the primary color signal "TX" in Figure 3) and absorb circuit variations, I installed DC level adjustment elements at terminals 31 and 33. By connecting it, you can adjust the DC level from the outside and adjust the white balance on the CRT5.

The DC-regenerated primary color signals pass through blanking circuits 24, 25, 26, and signal switching circuits 27, 28, 2.
9 is input. Each of the signal switching circuits 27, 28, and 29 receives a TV demodulated primary color signal RTVI from the output side of the conventional TV reception circuits 2 and 3 to input terminals 39 and 40° 41.
The GTVtBTV signal is supplied, and the level of the switching signal applied to the switching signal input terminal 35 (1
V or oV)i from the external signal R'rx t"TX t
BTX and TV signal RTV.

``TV'' and ``TV'' are switched and either one is
It is output to output terminals 38, 37, and 36. These output signals are applied to the CRTs from output terminals 36, 37, and 38 via the video output circuit 4 to drive them.

An advantage of the conventional circuit as described above is that the number of circuits required to clamp the primary color signals RTX, GTX, and BTx supplied from the outside is not required depending on the number of input signals, and the number of filters for clamping is the same. It becomes necessary. For this reason, there is a major drawback in that the number of terminal bins increases when configured with an IC.

The present invention improves these conventional drawbacks, and even when processing and clamping multiple input signals from the outside at the same time, only one clamping filter needs to be used. Therefore, the number of pin terminals of the IC can be reduced. The object of the present invention is to provide a device that can reduce the amount of energy used.

Below, a block diagram of an embodiment of the present invention is shown in FIG.
A specific circuit example thereof will be explained with reference to FIG. In addition, the third
Portions similar to those in the figures will be described using the same reference numerals.

In the apparatus of this embodiment, r[, one external primary color signal (
For example, only for the primary color signal GTX), the clamp input circuit 15. The amplifier circuit 19 and the pedestal clamp circuit 45 vC constitute a clamp circuit. That is,
A detection loop for the clamping voltage is provided only for the primary color signal GTx, and the clamping voltage obtained at both ends of the clamping filter is applied to the R-'rxt GTx, which also includes the primary color signals RTXI and BTX that do not constitute other detection loops.
tBTx 3-system control amplifier circuit 1γ, 19°2
In order to control each of the power supplies of 1, they are supplied in parallel as bias voltages for the current sources of the circuit. In this way, the capacitor 43 of the clamp filter
1. Only one pin terminal 11 is required to be added outside of -C, and the number of pin terminals 11 can be realized with the minimum number of fractions.

In the specific circuit diagram of FIG. 6, the amplifier circuit in the processing system of the primary color signal GTx is a transistor Q40"""4
□, and the transistor Q4. The emitter voltage of transistor 0
Bedes, which controls the terminal voltage of the clamp filter composed of transistors Q4 to Q9 from one side, and at the same time is composed of transistors Qo to Q3.

The output of the tal clamp circuit 46 also controls the terminal voltage of the clamp filter at the same time. Clamp filter voltage (
Collector voltage of transistor Q7.

That is, the voltage at terminal 11) is the primary color signal R'rx IG
Transistor Q12 for power control of three separate systems of TX and BTX. Q14. A current source transistor Q12 that controls Q1□. Q16. Add as common base bias for Q18. The voltage of the clamp filter, which depends on the collector voltage of the clamp pulse, blanking pulse, and collector voltage of the transistor Q45 for the amplifier of the primary color signal TX, is the same as that of the transistor Q12, Q14, Q1.
Simultaneously control the emitter voltage of □ and change the power supply voltage of transistors Q29"3o, Q31"402QQ, QQQ, respectively41 p 42 B29 539 5
5, it is possible to fix the DC voltage level to the next stage, that is, the emitter voltage of transistors Q34 and Q46tQ5□, to a constant pedestal voltage.

Note that transistors Q191Q20 fQ21 and Q2
2゜Q23. The collectors of the transistors Q2o and Q22 of the differential amplifier constituted by Q24 are connected to the base circuit vcA of the power supply control transistors Q12 (RTx) and Q1□ (BTx), and then the transistors Q19 and Q
By controlling 23 base circuits with direct current,
It is possible to adjust the white balance on the CRT by matching the potential of the output terminals 38 and 36 to the potential of the output terminal 37. The resistance value of the emitter resistor of the current source transistor Q21゜Q24 is set to 1j12 of the resistance value of the emitter resistor of the reference transistor Q16, and the DC level of the red system and blue system is adjusted arbitrarily with respect to the standard green system. Direction (vG±α) VC can be adjusted.

As described above, according to the present invention, a plurality of analog signals can be converted into a Bedestarck
By using a lamp, the number of pin terminals can be reduced when integrated into an IC, the circuit can be greatly simplified, and costs can be reduced, which has a large effect.

[Brief explanation of drawings]

Figure 1 is a block diagram of a general television receiver, Figure 2 is a block diagram of a television receiver with a function that allows switching of external RGB signal input, and Figure 3 is a television receiver with a conventional signal clamp device. Machine block diagram, 4th
The figure is a block diagram of a television receiver having a signal clamping device according to an embodiment of the present invention, and FIG. 6 is a specific circuit diagram thereof. 8.10.12...Input terminal for external primary color signal,
11...Clamp filter terminal, 14,1
5゜16... Clamp input circuit, 17, 19.
21... Amplifier circuit, 23... Clamp pulse input terminal, 24.25... Blanking circuit, 43... Capacitor, 46...
...Bedestal clang circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 3 Figure 4

Claims (1)

[Claims] A plurality of analog signal input terminals and an output terminal are provided, and a plurality of clamp circuits are provided for clamping the plurality of analog signals applied to the input terminals and outputting the clamped signals to the output terminal. A signal clamping device characterized in that the clamping voltage is a filter voltage generated by one clamping voltage generating circuit, and the clamping voltage is differentially supplied to the plurality of clamping circuits.