JP2010187102A - Analog/digital converter and analog/digital conversion correction method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an A/D converter for correcting temperature characteristics by a simple circuit configuration. <P>SOLUTION: The A/D converter includes a reference voltage generation part 12 for generating an analog voltage as a reference, two V/F conversion parts 13A and 13B, and two counting parts 14A and 14B. The V/F conversion part 13A and the counting part 14A are used for A/D conversion at an analog input terminal 11, and the reference voltage generation part 12, the V/F conversion part 13B, and the counting part 14B are used for correcting a result of A/D conversion. A count value of the counting part 14A at the time when a count value of the counting part 14B coincides with a predetermined count value is output to an output terminal 15 as a post-A/D conversion digital value. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an analog / digital conversion apparatus and an analog / digital conversion correction method.

  Analog / digital conversion (hereinafter referred to as A / D conversion) for converting an analog signal into a digital value is used to perform various arithmetic processes using various signals such as voice, image, and communication as numerical values (digital values). Yes. For example, Patent Document 1 discloses a conventional A / D converter. According to Patent Document 1, the A / D converter includes an analog-to-digital converter for detection that converts a detected analog signal into a detected digital signal, and a reference analog digital that converts a reference analog signal into a reference digital signal. A conversion unit, generating a highly accurate power supply voltage, dividing it using two resistors to generate a reference analog signal, converting it to a reference digital signal, and using this to detect The digital signal to be detected output from the analog / digital conversion unit is corrected.

In addition, there is a technique for performing A / D conversion with high accuracy in an A / D conversion apparatus using voltage / frequency conversion (V / F conversion). For example, according to Patent Document 2, two A / D converters are mounted, and A / D converters are simultaneously corrected while performing A / D conversions continuously. The A / D converter receives a reference voltage generator that generates a plurality of analog reference voltages and a plurality of analog reference voltages from the reference voltage generator for each of a plurality of measurement target voltage values. A first analog-to-digital converter that outputs a plurality of digital signals and a plurality of digital signals from the first analog-to-digital converter to calculate a measurement target digital signal corresponding to each of the plurality of measurement target voltage values A first arithmetic unit; a second analog-digital converter that inputs a measurement analog voltage and outputs a corresponding digital measurement value; and a digital measurement value output from the second analog-digital converter based on a measurement target digital signal In contrast, a second calculation unit that performs a calculation for a predetermined correction is included.

JP 2004-304738 A Japanese Patent No. 3877747

  Conventional A / D converters cannot perform temperature correction with a simple circuit configuration.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an A / D conversion apparatus capable of correcting temperature characteristics with a simple circuit configuration.

  In order to achieve the above object, an A / D conversion device according to a first aspect of the present invention generates first voltage / frequency conversion means for converting an analog input voltage into a frequency and a voltage serving as an analog reference. Reference voltage generation means, second voltage / frequency conversion means for converting the voltage output from the reference voltage generation means to frequency, and first count for counting the frequency output from the first voltage / frequency conversion means And second counting means for counting the frequency output from the second voltage / frequency converting means, and the first counting means and the second counting means are externally input sampling. The count operation is started from the time of signal activation, and the count value of the first count means at the time when the count value of the second count means matches a predetermined count value Characterized by a digital value after Le conversion.

  According to the present invention, A / D conversion temperature correction can be performed with a simple circuit configuration.

  Further, temperature correction for A / D conversion can be performed while performing A / D conversion continuously.

  In addition, it is not necessary to separately perform advanced calculations such as division for correction, the circuit scale is reduced, and power consumption is reduced.

  Preferably, the first voltage / frequency conversion means and the second voltage / frequency conversion means have the same voltage / frequency characteristics and temperature characteristics.

  As a result, the accuracy of A / D conversion correction can be improved.

  Preferably, the predetermined count value can be changed from outside the analog / digital converter.

  As a result, adjustment for correcting A / D conversion can be easily performed from the outside.

  Preferably, the voltage generated by the reference voltage generating means can be controlled from outside the analog / digital converter.

  As a result, adjustment for correcting A / D conversion can be easily performed from the outside.

  An analog / digital conversion correction method according to a second aspect of the present invention includes a first voltage / frequency conversion step of converting an analog input voltage into a frequency, a reference voltage generation step of generating a voltage serving as an analog reference, A second voltage / frequency conversion step for converting a voltage output from the reference voltage generation step into a frequency; a first counting step for counting a frequency output from the first voltage / frequency conversion step; A second counting step that counts the frequency output from the voltage / frequency conversion step, wherein the first counting step and the second counting step are times of activation of the sampling signal input from the outside. The counting operation is started from the first counting step, and the first counting at the time when the counting value of the second counting step matches the predetermined counting value. The count value of the step, characterized by a digital value after analog / digital conversion.

  According to the A / D conversion device of the present invention, temperature characteristics can be corrected with a simple circuit configuration.

It is a block diagram which shows the structure of the A / D converter which concerns on embodiment of this invention. 3 is a time chart illustrating an example of an operation of the A / D conversion device according to the first embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

(Embodiment 1)
FIG. 1 is a block diagram showing a configuration of an A / D conversion apparatus 10 according to an embodiment of the present invention. The A / D converter 10 includes an input terminal 11 for inputting an analog signal, a reference voltage generator 12 for generating an analog reference voltage, two V / F converters 13A and 13B, two counters 14A, 14B and an output terminal 15, and a digital value obtained by A / D converting an analog signal is output from the output terminal 15.

  The reference voltage generator 12 generates a predetermined voltage. For example, a predetermined voltage is generated by dividing the power supply voltage of the A / D converter 10 by a resistor.

  The V / F converters 13A and 13B output a pulse waveform having a frequency corresponding to the voltage of the input analog signal. The V / F converter 13A converts the voltage of the analog signal input to the input terminal 11 into a frequency and outputs it. The V / F converter 13B converts the output voltage of the reference voltage generator 12 into a frequency and outputs it. The V / F converters 13A and 13B are configured by a VCO (voltage controlled oscillator) or the like.

  The counting units 14A and 14B count the frequency. The counter 14A counts the frequency of the signal output from the V / F converter 13A. The counter 14B counts the frequency of the signal output from the V / F converter 13B. The digital value (Dx) after A / D conversion is output from the counting unit 14A to the output terminal 15.

  Next, the operation of the A / D conversion device 10 will be described.

  FIG. 2A is a time chart showing an example of the operation of the A / D converter 10 at a certain predetermined temperature. It is assumed that a predetermined voltage is input to the input terminal 11. Changes in the sampling signal, the output signal of the V / F conversion unit 13A, the count value of the counting unit 14A, the output signal of the V / F conversion unit 13B, and the count value of the counting unit 14B in order from the top of FIG. It shows how to do.

  P1 and P2 indicate activation points of the sampling signal. Sampling signals are input from the outside of the A / D converter 10 at predetermined intervals.

  The V / F converter 13A outputs a pulse signal that oscillates at a constant frequency (period TAx) corresponding to a predetermined voltage of the input terminal 11. The counting unit 14A starts counting from the activation point P1 of the sampling signal, and increases the count value by one every time a rising signal (an arrow in the figure) of the pulse waveform output from the V / F conversion unit 13A is detected.

  The V / F converter 13B outputs a pulse signal that oscillates at a constant frequency (period TBx) corresponding to a predetermined voltage of the reference voltage generator 12. The counter 14B starts counting from the activation point P1 of the sampling signal, and increases the count value by one every time a rising signal (arrow in the figure) of the pulse waveform output from the V / F converter 13B is detected.

  Px indicates a point in time when the count value of the counting unit 14B matches the predetermined count value (M). The counting unit 14B notifies the counting unit 14A that it matches the predetermined count value (M). The counting unit 14A receives the notification from the counting unit 14B, stops counting, and holds the count value Dx. Further, the counting operation is stopped until the sampling signal is newly activated (P2). The count value Dx of the counting unit 14A is output to the output terminal 15 as an A / D conversion value.

  By such an operation, the count value of the counting unit 14A in the time TCx from the activation point P1 to Px of the sampling signal becomes the A / D conversion value Dx. Here, the A / D conversion value Dx and the count time TCx are determined depending on the voltage of the input terminal 11, the predetermined count value M, the output voltage generated by the reference voltage generator 12, and the like. If TCx is increased, the A / D conversion value Dx can be increased, and the resolution is improved. Note that TCx needs to be smaller than the sampling period so that A / D conversion is completed within the sampling period. For this purpose, the predetermined count value M and the voltage generated by the reference voltage generator 12 may be adjusted.

  FIG. 2B is a time chart showing an example of the operation of the A / D conversion apparatus 10 at a temperature different from that in FIG. The voltage of the input terminal 11 and the output voltage of the reference voltage generator 12 are the same as those in FIG. It is assumed that the voltage / frequency characteristics of the V / F converters 13A and 13B change due to the temperature change, the periods of the V / F converters 13A and 13B become longer, and become periods TAy and TBy, respectively.

  Py indicates a point in time when the count value of the counting unit 14B matches the predetermined count value (M). The time TCy indicates the time from the activation time P1 of the sampling signal to the time Py. As the oscillation period of the V / F conversion unit 13B becomes longer from TBx to TBy, the time TCy is longer than the time TCx in the case of FIG.

  Since the oscillation period of the V / F conversion unit 13A is increased from TAx to TAy, the increase rate of the count value of the counting unit 14A is slowed, and as a result, the A / D conversion value tends to be small. On the other hand, the count period becomes longer from TCx to TCy. By setting the count period to the count period TCy corresponding to the temperature change condition, the influence of the longer period of the V / F conversion unit 13A is mitigated, and the A / D conversion value Dy becomes a value approximate to Dx.

  As a result, the temperature characteristic can be corrected with a simple circuit configuration.

  Further, the circuit necessary for the correction is only a comparator for comparing with the predetermined count value M, and it is not necessary to mount an arithmetic unit such as a divider for the correction, and the circuit scale can be reduced.

  Further, when the voltage / frequency characteristics and temperature characteristics of the V / F converters 13A and 13B are the same or approximate, the change in the period of the V / F converters 13A and 13B caused by the temperature change is approximately proportional. Therefore, the accuracy of A / D conversion correction can be improved by changing the count period according to the temperature.

    Further, it is desirable that the predetermined count value M compared in the counting unit 14B and the voltage generated by the reference voltage generating unit 12 can be changed from the outside of the A / D conversion device 10.

    Thereby, adjustment for correction such as adjustment of the accuracy of A / D conversion can be easily performed from the outside.

  The circuit configurations of the A / D conversion device 10, the reference voltage generation unit 12, the V / F conversion units 13A and 13B, and the counting units 14A and 14B described in each embodiment are merely examples, and can be arbitrarily changed or modified. Is possible.

10 A / D converter
11 Input terminal
12 Reference voltage generator 13A, 13B V / F converter 14A, 14B Counter
15 Output terminals P1, P2 Sampling signal activation time
M Predetermined count value TCx, TCy Count period TAx, TAy Oscillation period of V / F converter TBx, TBy Oscillation period of V / F converter Dx, Dy Digital value after A / D conversion

Claims (5)

First voltage / frequency converting means for converting an analog input voltage into a frequency;
A reference voltage generating means for generating an analog reference voltage;
Second voltage / frequency converting means for converting the voltage output from the reference voltage generating means into a frequency;
First counting means for counting the frequency output from the first voltage / frequency converting means;
Second counting means for counting the frequency output from the second voltage / frequency converting means;
An analog / digital conversion device comprising:
The first counting means and the second counting means start a counting operation from the time of activation of a sampling signal input from the outside,
The count value of the first counting means when the count value of the second counting means matches a predetermined count value is a digital value after analog / digital conversion. Conversion device. The analog / digital conversion device according to claim 1, wherein the first voltage / frequency conversion unit and the second voltage / frequency conversion unit have the same voltage / frequency characteristic and temperature characteristic. The analog / digital conversion apparatus according to claim 1, wherein the predetermined count value can be changed from outside the analog / digital conversion apparatus. The analog / digital conversion apparatus according to claim 1, wherein the voltage generated by the reference voltage generation means can be changed from outside the analog / digital conversion apparatus. A first voltage / frequency conversion step for converting an analog input voltage to a frequency;
A reference voltage generation step for generating an analog reference voltage;
A second voltage / frequency conversion step for converting the voltage output from the reference voltage generation step into a frequency;
A first counting step for counting a frequency output from the first voltage / frequency conversion step;
A second counting step for counting the frequency output from the second voltage / frequency conversion step;
An analog / digital conversion correction method comprising:
The first counting step and the second counting step start a counting operation from the time of activation of a sampling signal input from the outside,
An analog / digital signal obtained by converting the count value of the first count step at the time when the count value of the second count step matches a predetermined count value into a digital value after analog / digital conversion. Conversion correction method.

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