JPH03198429A - Input level deciding circuit for a/d converter - Google Patents

Abstract

PURPOSE:To easily and accurately adjust the input level of an A/D converter by detecting the maximum value and the minimum value of the output signal of the A/D converter, and inverting the result to project the image on a monitor. CONSTITUTION:A device consists of an input terminal 1, an A/D converter 2, a D/A converter 3, logic circuits 4 and 5, and a monitor 6. A maximum value and a minimum value of the digital signal converted by the A/D converter 2 are detected, and the signal is inverted, and this inverted digital signal is converted to an analog signal and is outputted. Thus, the input signal level of the A/D converter 2 is accurately discriminated in real time, and an operator can easily and accurately adjust the input signal level while seeing the image.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to adjusting the input level to an A/D converter in a device equipped with an A/D converter such as a television receiver. The present invention relates to an input level determination circuit of an A/D converter used to determine the input level of the A/D converter.

[Prior Art] Figure fJS4 is a configuration diagram of a conventional A/D converter manual level determination circuit. The A/D converter (3) converts an analog signal into a digital signal, and the A/D converter (3) converts the digital signal (C
) to an analog signal, and (4) is an output terminal for the converted analog signal (b).

Next, the operation of the above configuration will be explained.

When an analog video signal with a waveform as shown in FIG. 5(a) is input to the input terminal (1), the input analog video signal (a) is converted into a digital signal (e) by the A/D converter (2). ) is converted to Here, if the video signal (a) that can be input to the A/D converter (2) is within the range between (violet) in FIG. 5 as the upper limit and y) as the lower limit, the digital signal (C) is a signal in which the upper part of (heavy) and the lower part of (ri) in FIG. 5 are cut out.

Next, the converted digital signal (C) is converted into a D/A
The signal is inputted to a converter (3), converted into an analog signal with a waveform as shown in FIG. 5(b), and outputted to an output terminal (4).

Here, the output signal (
In order to obtain b), - When adjusting the input level to the A/D converter (2), adjust the level by yourself while observing the output signal waveform of the D/A converter (3) with an oscilloscope, etc. I was adjusting.

[Problems to be Solved by the Invention] Since the input level determination circuit of the conventional A/D converter is configured as described above, it is necessary to accurately determine the level of the input signal in order to make the waveforms of the input and output signals the same. When adjusting, D/A
The level of the input signal must be adjusted while observing the output signal waveform of the converter (3) using an oscilloscope or the like, which poses a problem that level adjustment becomes complicated and troublesome.

This invention was made to solve the above-mentioned problems, and it is possible to easily and accurately measure the input level of an A/D converter by eliminating the troublesome work of observing the output signal waveform with an oscilloscope or the like. A/
An object of the present invention is to provide an input level determination circuit for a D converter.

[Means for solving the problem] An input level determination circuit for an A/D converter according to the present invention includes:
It is characterized by being configured to detect the maximum and minimum values of a digital signal converted by an A/D converter, invert the signal, and convert the inverted digital signal into an analog signal and output it. shall be.

[Operation] According to the present invention, an input analog signal is converted into a digital signal, and the maximum value and minimum value of the converted digital signal are detected, so that the output signal can be displayed on a monitor of a television receiver, etc. While displaying the image, the input level of the A/D converter can be easily adjusted so that the correct image is obtained.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described based on the drawings.

FIG. 1 is a block diagram of an input level determination circuit of an A/D converter according to an embodiment of the present invention, in which (1)
is an input terminal for analog signal (a), (2) is an A/D converter that converts the input analog signal into a digital signal (C), (3) is a D/A converter, and (4) is an A/D converter. converter(
A logic circuit that calculates the maximum and minimum values of the digital signal (C) converted in step 1), which includes an AND circuit (41), NO
It consists of an R circuit (42) and an OR circuit (43).

(5) is a logic circuit that inverts the output of the A/D converter (2), consisting of multiple XOR circuits (51), (6) is a monitor, and (d) is a digital signal obtained by the logic circuit (4). The signal (e) is a digital signal obtained by the logic circuit (5).

Next, the operation of the above configuration will be explained.

Now, when an analog video signal with a waveform as shown in FIG. 2(a) is input to the input terminal (1), the A/D converter (
The input signal conversion level of 2) is (K) to ( in Fig. 2(a)).
When the signal shown in FIG. 2(a) is within the range of (f
), and the A/D converter (2) converts the 8-bit digital signal (C
) is converted to

Next, this digital signal (C) is input to the logic circuit (4), and at this time, the AND circuit (41) outputs rlJ and the NOR circuit (42) as shown in the truth table of FIG. rOJ is output as shown in the truth table of FIG. 3, and each output is input to the OR circuit (43), and this OR circuit (43) A digital signal (d) of "1" is output.

Next, digital signal (C) and digital signal (d)
is input to the logic circuit (5), and the digital signal is inverted in the XOR circuit (51) as shown in the truth table of FIG. 3 to obtain an 8-bit digital signal Ce) of roooooooooJ.

Furthermore, the signal shown in FIG. 2(a) becomes the minimum at point (g) in FIG. 2, and the signal shown in FIG.
It is converted into an 8-bit digital signal (c) of ooooooJ.

Next, this digital signal (C) is input to the logic circuit (4), and at this time, the AND circuit (41) outputs "O" as shown in the truth table of FIG. 3, while the NOR circuit ( 42) outputs "rl" as shown in the truth table of Fig. 3, and each output is input to the OR circuit (43), which is in turn as shown in the truth table of Fig. 3. The rQJ digital signal LHd) is output as follows.

Next, the digital signal (C) and the digital signal (d
) is input to the logic circuit (5), and the digital signal is inverted in the XOR circuit (51).

rllllllllllJ's 8-bit digital signal
e) is obtained.

The digital signal as shown in FIG. 2(e) obtained as described in L is converted into an analog signal by the D/A converter (3), resulting in a waveform as shown in FIG. 2(b). The output signal is manually input to the monitor (6).

This output signal (b) is completely different from the human input signal (a),
If the input signal level of the A/D converter (2) is not appropriate,
When the output signal is input to a monitor (6) such as a television receiver, a clear image cannot be obtained. Therefore, while looking at the monitor (6), adjust the A/
D Proper adjustment can be made by making adjustments to maximize the human power signal level.

[Effects of the Invention] As described above, according to the present invention, by detecting the maximum value and minimum value of the output signal of the A/D converter, inverting them, and displaying the image on a monitor, etc. The input signal level of the D converter can be accurately determined in real time, and the human signal level can be easily and accurately adjusted while viewing the image.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of an input level determination circuit of an A/D converter according to an embodiment of the present invention, Fig. 2 is a waveform diagram of input/output signals, Fig. 3 is a logic circuit truth diagram, and Fig. 4 is a conventional A/D
FIG. 5 is a block diagram of the input level determination circuit of the converter, and is a waveform diagram of the human output signal of the conventional circuit. (2)...A/D converter, (3)...D/A converter, (4), (5)...logic circuit, (6)...monitor. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] (1) A that converts input analog signals to digital signals
/D converter; a logic circuit that detects the maximum value and minimum value of the digital signal output from the A/D converter;
An A/D converter comprising: a logic circuit that inverts a digital signal output from the A/D converter; and a D/A converter that converts the inverted digital signal into an analog signal. input level judgment circuit.