JPH069283U - Output level automatic adjustment circuit - Google Patents

Abstract

(57) [Abstract] [Purpose] A circuit that automatically adjusts the output level of each video amplifier circuit in a device that outputs a video signal as three primary color signals of red, blue, and green to a predetermined level. [Structure] In three-system amplifier circuits (11 to 13), variations in input level and the like are adjusted to adjust the attenuation of an attenuator (8 to 10) provided in series with the amplifier circuits, and output terminals (14 to 16)
To a predetermined level. For this adjustment, the CPU 20 amplifies the test signals (31 to 33) by the circuit of the amplifier circuit and the attenuator, and the output of the CPU 20 is compared with each test signal or the like as a reference to determine whether the output is at a predetermined level or not. Is determined, and the attenuation of the attenuator is automatically adjusted by the control signals (36 to 38) based on the determination result. At the time of this adjustment, the switching circuit 4 switches to the b side, but normally it is the a side. The automatically adjusted attenuation data is stored in the nonvolatile memory 21.
It is stored in (EEPROM etc.), and the attenuation of each attenuator is set based on the memory data during normal use.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention mainly relates to a circuit adapted to automatically adjust the output level of each video amplification circuit in a device which outputs a video signal with three primary color signals of red, blue and green to a predetermined level. .

[0002]

[Prior art]

 A conventional technique will be described with reference to FIG. FIG. 2 shows, as an example, a main part of a video amplifier circuit in a MUSE decoder. As shown, the image amplification circuit amplifies a green (G) or luminance (Y) signal, a blue (B) or color difference (BY) signal, and a red (R) or color difference (RY) signal. It consists of three circuits and amplifies and outputs each signal. Each of these video output signals serves as a video input signal for the color television receiver. Therefore, each signal must be output at a predetermined level in order to reproduce the normal hue and contrast. For this reason, the output level adjustment knobs (VR1 to VR3) were provided in the circuit of each system as shown in the figure, and the output level was adjusted to a predetermined level at the factory.

[0003]

[Problems to be solved by the device]

 Therefore, it was necessary to manually adjust the three volumes (VR1 to VR3), which required labor (man-hours) in the production process. In addition, since it was done manually, there were some inevitable variations in these volume adjustments. It is an object of the present invention to provide a level adjustment circuit that automates output level adjustment in order to reduce the above-mentioned trouble (man-hour) and prevent adjustment variations.

[0004]

[Means for Solving the Problems]

 The present invention relates to the following video signal amplification circuit for amplifying a video signal converted from digital to analog by a D / A conversion circuit, and a first amplification circuit for amplifying a green or luminance signal and blue or blue. In a video circuit comprising a second amplifier circuit for amplifying the color difference signal of No. 1 and a third amplifier circuit for amplifying the red or red color difference signal, an attenuator is provided in series with each of the amplifier circuits, The test signal output from the CPU is input via the D / A conversion circuit and the attenuator, and the test signal output of each of the amplification circuits is converted into a digital signal by the A / D conversion circuit. And returns to the CPU, and the CPU requires the respective attenuators so that the respective output levels of the test signals to be returned become predetermined levels. Attenuation is set and each attenuation is stored in a non-volatile memory, and each attenuator is set based on the attenuation data read from the non-volatile memory during normal video signal amplification. An output level automatic adjustment circuit in a circuit is provided.

[0005]

[Action]

 The basis of the present invention is that in one amplifier circuit, variations in input level and amplification degree are adjusted by an attenuator provided in series with the amplifier circuit so that the output level becomes a predetermined value. In order to set the attenuation of this attenuator, a test signal for calibration from the CPU is amplified by the circuit of the amplification circuit and attenuator, and the output is judged whether or not the CPU has a predetermined level, and the judgment is made. Attenuator attenuation is automatically set based on the result. The automatic adjustment of the output level in the video signal amplifier circuit according to claim 2 is the one in which the above basic technical idea is applied to the first to third amplifier circuits and each output is set to a predetermined level. is there.

[0006]

【Example】

 Hereinafter, an output level automatic adjusting circuit according to the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram of an essential part showing an embodiment of an output level automatic adjusting circuit according to the present invention. In the figure, 1 is an input digital green or luminance signal, 2 is the same or blue or blue color difference signal, 3 is the same or red or red color difference signal, 4 is the input signal and the signal from the CPU 20. Switching circuits for switching the test signals (31 to 33) with the switching signal 34 from the CPU 20. Switching circuits 5, 6, and 7 are first (5), second (6) and 3 (7) D / A conversion circuits, 8, 9 and 10 are electronically controllable first (8), second (9) and third (10) whose attenuation is automatically set by CPU 20. Attenuators 11, 12, and 13 are first (11), second (12), and third (13) amplifier circuits for amplifying the signals, 14, 15 and 16 are output terminals of the signals, Reference numerals 17, 18 and 19 convert the outputs of the first to third amplifier circuits from analog to digital and feed them back to the CPU 20. A first (17), a second (18) and a third (19) A / D conversion circuit, 20 is an output of the test signal, an output of the switching signal, and a discrimination of the level of the fed back output signal, CPU, 21 for setting the attenuation of each attenuator and a non-volatile memory (EEPROM etc.) for storing the attenuation of each attenuator. The basic technical idea of the present invention is as described in the above "Operation", and the present embodiment is an application of this basic technical idea. When the color video signal in the television signal is output as the three primary color signals of red (R), blue (B), and green (G), or the three signals of luminance (Y) and color difference (BY, G-Y), A certain level relationship is required between these signals. If this relationship is not normal, hue, saturation, brightness, contrast, etc. cannot be faithfully reproduced. Therefore, the level matching of the above-mentioned three primary color signals and the like has an important meaning.

Next, the operation of the present invention will be described. In normal use, the switching circuit 4 (SW1 to SW3: interlocking switching) is at the a side position, but when adjusting the level, it is switched to the b side position. This switching is based on the switching signal 34 output from the CPU 20 in this embodiment, but may be manually switched. By setting the switching circuit to the b side, the three test signals (31 to 33) from the CPU 20 are applied to the respective circuits. These three test signals are, so to speak, calibration signals for setting the attenuation of the attenuator of each circuit. Therefore, there is no particular restriction on the content of this test signal, but it is also one method to use each signal as a white signal when the three signals are combined. These three test signals are respectively amplified to a certain level by the circuits of three systems, and the output levels thereof are fed back to the CPU 20 via the first to third A / D conversion circuits (17 to 19). The CPU 20 determines whether or not each of the returned levels is a predetermined level. This determination is performed for each circuit, but either the above test signal for each circuit or another reference signal correlated with this test signal may be used as a determination reference. That is, since the amplification degree that each circuit of the three systems should have is known in advance as described above, the propriety of the amplification degree can be determined by comparing the fed back level with the reference signal. Further, in this determination, one cycle of one vertical period (one field) is set as one unit, and an average of several units is calculated, and the average level is compared with the reference signal. Therefore, the A / D conversion circuits (17 to 19) are reset by the vertical synchronizing signal 35. Then, the CPU 20 repeats this comparison / determination and outputs the corresponding control signals (36 to 38) to the respective attenuators (8 to 10) to set the respective attenuation degrees, and outputs the predetermined values at the output terminals (14 to 16). Converge to reach the output level of. The converged point becomes the set attenuation of each attenuator, and the stable state is achieved. The set attenuation of each attenuator is stored in the non-volatile memory (EEPROM etc.) 21.

In a normal use state (a side of the switching circuit 4), the CPU 20 reads the stored attenuation data from the nonvolatile memory 21 and sets each attenuator to a predetermined attenuation. As a result, the output level of each output terminal (14-16) is set to a predetermined level. As described above, it is sufficient to set (adjust) the attenuation of each attenuator once at the factory. From this viewpoint, the first to third A / D conversion circuits (17 to 19) It means that it is only necessary to make adjustments, and it can be said that it is uneconomical to uniformly install all devices. In that case, as shown in FIG. 1, the A / D conversion circuit part is made into one block 41 and this is deleted from the device, and at the time of adjustment, this block is made into one jig by the connectors 42 and 43. You may make it connect. However, the electronic device is not limited to this device, and there is no change over time. Therefore, even if the level is adjusted correctly at the factory, it is possible that each level will shift over time. In order to correct this deviation, the attenuation degree setting described above may be constantly performed. That is, each A / D conversion circuit is provided in this device without being removed as described above, and the switching circuit 4 is automatically switched to the b side when the power supply of this device is turned off. The memory data is reset and the stored data is updated. When the power is turned on, each attenuator is reset based on the updated data. This is always repeated when the power is turned on and off. In this case, switching of the switching circuit 4 must be CPU switching, not manual configuration.

[0009]

[Effect of device]

 As described above, according to the present invention, each output level adjustment when a color video signal is output with a predetermined level of three primary color signals such as red, blue, and green is automatically adjusted by the test signal output from the CPU. By doing so, it is possible to save the trouble of manual adjustment by volume as in the past and to prevent adjustment variations, which contributes to rationalization of production and improvement of quality.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an essential part showing an embodiment of an automatic output level adjusting circuit according to the present invention.

FIG. 2 is a main part circuit diagram for explaining a conventional output level automatic adjustment circuit.

[Explanation of symbols]

 1 Green or luminance signal 2 Blue or blue color difference signal 3 Red or red color difference signal 4 Switching circuit 5 D / A conversion circuit (same for 6, 7) 8 Attenuator (same for 9, 10) 11 Amplification circuit (12, 13 Same as above 14 Output terminal (same as 15 and 16) 17 A / D conversion circuit (same as 18 and 19) 20 CPU 21 Non-volatile memory (EEPROM) 31 Test signal (same as 32 and 33) 36 Attenuation setting Control signal (same for 37 and 38)

Claims (2)

[Scope of utility model registration request] 1. An attenuator that can be electronically controlled is provided in series with an amplifier circuit, a test signal is output from a CPU, the test signal is converted into analog and input to the amplifier circuit, and the attenuator and the amplifier circuit are connected. The output thus passed is digitized and returned to the CPU, and the CPU sets the attenuator to a required attenuation so that the output level to be fed back becomes a predetermined level and stores the attenuation in a non-volatile memory, An automatic output level adjusting circuit, wherein the attenuator is set on the basis of the attenuation read from the non-volatile memory during normal signal amplification. 2. A video signal amplification circuit for amplifying a video signal converted from digital to analog by a D / A conversion circuit, comprising: a first amplification circuit for amplifying a green or luminance signal; and a blue or blue In a video circuit including a second amplification circuit for amplifying a color difference signal and a third amplification circuit for amplifying a red or red color difference signal, an attenuator is provided in series with each of the amplification circuits, Is C
The test signal output from the PU is input via the D / A conversion circuit and each of the attenuators, and the test signal output of each of the amplification circuits is converted into a digital signal by the A / D conversion circuit to convert the test signal to the CPU. Then, the CPU sets each of the attenuators to a required attenuation so that each of the test signal output levels to be fed back becomes a predetermined level, and stores each attenuation in a non-volatile memory. When the video signal is amplified, the attenuator is set based on the attenuation data read from the non-volatile memory, and the output level automatic adjusting circuit in the video signal amplifying circuit is set.