JPS5842995B2 - Video signal processing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a video signal processing device used in a television receiver, in particular to a power supply means, and the invention relates to a video signal processing device used in a television receiver. It is an object of the present invention to provide a device that can display a stable image without fluctuations in the voltage between the cathode and the first grid that affects a cathode ray tube, and that can be realized using a minimum number of voltage stabilizing means. That is.

Recently, television receivers have been using integrated circuit elements (ICs).
Technology is rapidly progressing, and it has become common for almost all circuits, even video signal processing circuits, to be integrated into ICs.

However, in such an IC-based circuit, if the operating power supply voltage changes, the level and amplitude of the output signal will change significantly, and the signal voltage between the cathode of the cathode ray tube and the first grid will change. Therefore, the brightness and contrast of the image may change due to fluctuations in the power supply voltage.

In order to eliminate this inconvenience, conventionally used IC
All power supply voltages for the devices were stabilized by separate voltage stabilization circuits, or voltage stabilization circuits were installed inside each IC device immediately after its power supply terminals. .

However, if all the operating voltages of IC elements are stabilized in this way, the power consumed by the voltage stabilization circuit will increase, and moreover, a large capacity stabilization circuit and many voltage stabilization circuits for each IC element will be required. The disadvantage was that there was a lot of loss in the circuit.

Further, even if the power supply voltage to the IC element can be stabilized in this way, the power supply voltage to the cathode ray tube cannot be stabilized, and this causes a problem in that images change.

Therefore, the present invention solves all such conventional drawbacks, and makes it possible to prevent the image on the cathode ray tube from changing even if the power supply voltage changes, and to realize it at low cost using a minimum voltage stabilizing circuit with a small capacity. The purpose is to provide a device that can.

Therefore, in the present invention, by applying a fluctuating power supply voltage from a horizontal output circuit to a video circuit, an AGC detection circuit, an RFAGC circuit, and a cathode ray tube, which are all composed of integrated circuit elements, their electrical voltages can be changed. The voltage between the cathode and the grid of the cathode ray tube does not change even when the power supply voltage is changed, and the voltage stabilization circuit is used to stabilize only the operation starting point reference voltage of the VIP circuit and RFAGC circuit, which require a stabilized power supply voltage. This is characterized in that a minimum stabilizing circuit with a small capacity is used to apply the power supply voltage.

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

First, FIG. 1 shows its schematic configuration, where 1 is a tuner, and 2 is a VV that amplifies the VIP signal obtained from tuner 1.
IP circuit, 3 is a video detection circuit that detects the VIP signal, 4 is a matrix mixer of the video signal and color demodulation signal, etc. to generate three R-G-B color signals, and these are sent to cathode ray tube 5 (3). This is a video circuit that prints on each of the two cathodes.

This video circuit 4 includes a color demodulation circuit 6, a matrix circuit 7 that mixes the video signal and the color demodulation signal and converts them into three color signals, and a cathode ray tube 5 that amplifies the color signals. The color output circuit 8 and the like are also provided.

Further, 9 is an AGC detection circuit that generates an AGC voltage from the output signal of the video detection circuit 3 and applies it to the VIP circuit 2;
is an RFAGC circuit that generates a so-called delayed type RFAGC voltage from the AGC voltage and applies it to the tuner 1.

A variable resistor 11 is added to this RFAGC circuit 10 for creating a reference voltage for determining its operation starting point.

The parts surrounded by broken lines in Fig. 1 are parts that cannot be constructed by IC elements, and the VIP circuit 2 is shown in Fig. 2.
, an example of an IC element including a video detection circuit 3, an AGC detection circuit 9, and an RFAGC circuit 10 is shown.

The VIP circuit 2 is composed of three sets of differential amplifiers 2a to 2c, and the video detection circuit 3 is composed of a synchronous detection circuit 3a using differential amplifiers and two sets of buffer amplifier circuits 3b and 3c.

The AGC detection circuit 9 is a buffer amplification circuit 9a for video signals.
The AGC voltage is applied to the first and second stage differential amplifiers 2a and 2b of the VIP circuit 2 by forming the peak detection circuit 9b and a buffer amplifier circuit 9c for the AGC voltage.

Further, the RFAGC circuit 10 includes a differential amplifier 10a and a buffer amplifier circuit 10b.
The AGC voltage from the AGC detection circuit 9 is applied to one input terminal of the , and the variable resistor 11 is applied to the other input terminal.
A reference voltage is added to the RFAGC operation so that the RFAGC operation is started only when the AGC voltage exceeds this reference voltage.

Further, 12 is a rectifier circuit that rectifies the commercial power supply, 13 is a voltage stabilization circuit that stabilizes the voltage of the main power supply supplied from the rectifier circuit 12, and 14 is a horizontal output circuit.

The rectifier circuit 12, voltage stabilization circuit 133, and horizontal output circuit 14 are the same as conventional ones, and the operation of the voltage stabilization circuit 13 considerably stabilizes the main power supply against voltage fluctuations in the commercial power supply line. However, some fluctuations remain, and the various power supply voltages generated from the horizontal output circuit 14 also fluctuate in accordance with the fluctuations.

An example of the rectifier circuit 12 and the voltage stabilizing circuit is shown in FIG. 3, and an example of the horizontal output circuit 14 is shown in FIG. 4.

In this device, power is supplied to almost all the circuits from this horizontal output circuit 14, and the fluctuating power supply voltage is transmitted to the video detection circuit 3, video circuit 4, cathode ray tube 5,
It is applied to the AGC detection circuit 9, the filter and the RFAGC circuit 10.

What should be noted here is that both the video detection circuit 3 and the various circuits in the video circuit 4 have the characteristic that when the power supply voltage increases, the output increases, and when the power supply voltage decreases, the output decreases. A color signal output is applied to the cathode of the cathode ray tube 5, and a varying power supply voltage from the horizontal output circuit 14 is also applied to the first grid of the cathode ray tube 5.

In this way, when the power supply voltage from the horizontal output circuit 14 increases, the level of the color signal applied to the cathode of the cathode ray tube 5 increases, but at the same time, the voltage of the first grid also increases, and conversely, the horizontal output When the power supply voltage from the circuit 14 decreases, the level of the color signal applied to the cathode of the cathode ray tube 5 decreases, and the voltage of the first grid also decreases, so that the cathode - the first grid always decreases.
An excellent effect is obtained in that the voltage between the grids is kept constant, and therefore the image does not change due to fluctuations in the power supply voltage.

However, if the power supply voltage of the VIP circuit 2 decreases and the gain decreases, the receiving characteristics in a weak electric field will deteriorate, so a power supply voltage stabilized by the voltage stabilizing circuit 15 is applied to the VIP circuit 2.

Since this voltage stabilizing circuit 15 only needs to stabilize the power supply voltage for the VIF circuit 2, a minimal one with a small current capacity can be sufficient.

The one in Fig. 2 is composed of a constant voltage diode 15d and transistors 15a, isb, and 15c connected to the respective differential amplifiers 2a, 2b, and 2c, but one transistor is common to the three differential amplifiers. Alternatively, it may be just a constant voltage diode.

Therefore, the power consumption and cost due to the addition of this voltage stabilizing circuit 15 can be almost ignored.

Furthermore, in the RFAGC circuit 10, if the loop gain is sufficiently large, the AGC voltage will hardly change even if the power supply voltage fluctuates.
This means that the input electric field that starts the FAGC operation changes accordingly.

In order to prevent this, in this device, a stabilized voltage is also applied to the variable resistor 11 for creating the reference voltage.

In the case of this variable resistor 11 as well, since almost no current flows, it suffices to have a minimum capacity.

Therefore, the power supply voltage may be applied from the voltage stabilizing circuit 15 described above.

However, when the voltage stabilizing circuit 15 is built into an IC element, one extra pin for extraction is required, so instead of that, a constant voltage diode 13a existing in the voltage stabilizing circuit 13 for the main power supply is used. It is most effective to apply a voltage stabilized from

Of course, the current capacity of the constant voltage diode 13a is not large, but it can obtain enough current to be applied to the variable resistor 11.As detailed above, in the present invention, the video detection circuit, video circuit, and AGC
Since the detection circuit, RFAGC circuit, and cathode ray tube are all supplied with varying power supply voltage from the horizontal output circuit, even if these power supply voltages fluctuate, the voltage between the cathode and the first grid in the cathode ray tube will not change. can be eliminated and image fluctuations can be effectively prevented.
VIP circuit and R that absolutely require a stabilized power supply
Since the stabilized power supply voltage from the voltage stabilization circuit is used only for the operation start reference voltage of the FAGC circuit, a voltage stabilization circuit with a minimum current capacity can be used, reducing power consumption. , and the cost can be significantly reduced.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a video signal processing device according to an embodiment of the present invention, and FIGS. 2, 3, and 4 are detailed circuit diagrams of a portion of the same device. 1...Tuner, 2...VIF circuit,
3...Video detection circuit, 4...Video circuit, 5...Cathode ray tube, 6...Color demodulation circuit, 7...Matrix Circuit, 8... Color output circuit, 9... AGC detection circuit, 10...
... RFAGC circuit, 11... Variable resistor,
12... Rectifier circuit, 13... Voltage stabilization circuit, 14... Horizontal output circuit, 15...
...Voltage stabilization circuit.

Claims (1)

[Claims] 1. A tuner, a VIP circuit that amplifies the VIP signal,
a video detection circuit that detects the VIP signal; a video circuit that generates a color signal from the video signal and the color demodulation signal and applies it to the cathode ray tube; and a video circuit that generates an AGC voltage from the output signal of the video detection circuit to generate the VIP circuit. an RFAGC circuit that generates an RFAGC voltage from the output of the AGC detection circuit and applies it to the tuner; and a horizontal output circuit that generates a fluctuating power supply voltage. circuit, AGC detection circuit, RFAG
In addition to supplying varying power supply voltages to the C circuit button and the cathode ray tube, a power supply voltage stabilized by a voltage stabilization circuit is supplied to the operation start point reference voltage of the VIP circuit and the RFAGC circuit. Features of video signal processing device.