JP2005210356A - A/d converter and its method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an A/D converter in which the reduction of quantization errors is realized inexpensively, and to provide a method therefor. <P>SOLUTION: A sine wave generator 12 generates a sine wave which is for superposing on an input voltage V and has positive/negative symmetry and whose amplitude is larger than a voltage per 1 LSB, corresponding to the reference voltage of the A/D converter 11. The A/D converter 11 intermittently samples the input voltage V, on which the sine wave is superposed, and converts it into digital data, on the basis of the comparison of the sampled input voltage V with the reference voltage. A CPU 13a in a μCOM 13 calculates the true digital data, on the basis of a plurality of digital data, which are converted by the A/D converter 11 after intermittent sampling, within a time of integral multiple of the cycle of the sine wave. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an A / D conversion apparatus and method for intermittently sampling an input voltage and A / D converting the sampled input voltage into digital data.

  For example, in order to grasp an analog input voltage such as a terminal voltage of a vehicle-mounted battery by a microcomputer (hereinafter referred to as a microcomputer), it is necessary to convert it into digital data by an A / D converter.

  However, as shown in FIG. 4, since the A / D converter converts an analog input voltage that is a continuous signal into digital data that is a discrete signal, a quantization error always occurs. If this quantization error is large, the microcomputer cannot accurately detect the input voltage. Therefore, it is conceivable to increase the number of bits and reduce the quantization error. However, the higher the number of bits, the more expensive the A / D converter, and there is a problem in cost.

  Therefore, the present invention focuses on the above-described problems, and an object thereof is to provide an A / D conversion apparatus and method that can reduce quantization errors at low cost.

  The invention according to claim 1 is an A / D provided with A / D conversion means for sampling an input voltage and converting the input voltage into digital data based on a comparison between the sampled input voltage and a reference voltage. A conversion device for generating a periodic voltage having a positive / negative symmetry and an amplitude larger than a voltage per 1 LSB corresponding to the reference voltage to be superimposed on the input voltage; and a period of the periodic voltage Calculation means for calculating true digital data on the basis of digital data of an input voltage obtained by superimposing a plurality of the periodic voltages, which are sampled and converted intermittently by the A / D conversion means within an integral multiple of time. And an A / D converter characterized by comprising:

  According to the first aspect of the present invention, the generating means generates a periodic voltage larger than the voltage per LSB corresponding to the reference voltage and having a positive / negative symmetry to be superimposed on the input voltage. The A / D conversion means intermittently samples the input voltage on which the periodic voltage is superimposed, and converts it into digital data based on the comparison between the sampled input voltage and the reference voltage. The calculating means calculates true digital data on the basis of a plurality of converted digital data by the A / D conversion means sampling intermittently within a time that is an integral multiple of the period of the periodic voltage. Therefore, even if the number of bits of the A / D conversion means is not increased, the true digital data is data having a higher number of bits with a reduced quantization error than the digital data converted by the A / D conversion means. .

  A second aspect of the present invention is the A / D conversion apparatus according to the first aspect, wherein the calculation means calculates a value obtained by dividing a sum of the plurality of digital data by the number of the plurality of digital data. The present invention resides in an A / D converter characterized by being calculated as digital data.

  According to the second aspect of the present invention, the calculating means calculates a value obtained by dividing the sum of a plurality of digital data by the number of the plurality of digital data as true digital data. Therefore, true digital data with a reduced number of bits and a high number of bits can be calculated based on a plurality of digital data.

  The invention according to claim 3 is an A / D conversion method for sampling an input voltage and A / D converting the input voltage into digital data based on a comparison between the sampled input voltage and a reference voltage. The input voltage is superimposed with a periodic voltage that is positive and negative symmetric and has an amplitude larger than the voltage per LSB corresponding to the reference voltage, and the input voltage superimposed with the periodic voltage is intermittently sampled, and the digital A / D conversion is performed on the data, and true digital data is calculated based on the plurality of digital data obtained by sampling and A / D conversion within a time that is an integral multiple of the period of the periodic voltage. A / D conversion method.

  According to the third aspect of the present invention, a periodic voltage larger than the voltage per LSB corresponding to the reference voltage is generated, which is symmetrical with respect to the input voltage and superimposed on the input voltage. The input voltage on which the generated periodic voltage is superimposed is intermittently sampled and A / D converted into digital data based on a comparison between the sampled input voltage and a reference voltage. The A / D conversion means samples intermittently within a time that is an integral multiple of the period of the periodic voltage, and true digital data is calculated based on the plurality of converted digital data. Therefore, even if the number of bits for A / D conversion is not increased, true digital data is data with a smaller quantization error and a higher number of bits than digital data subjected to A / D conversion.

  As described above, according to the first and third aspects of the invention, even if the number of bits for A / D conversion is not increased, true digital data has a quantization error more than that of A / D converted digital data. Since the data is reduced and the number of bits is high, it is possible to obtain an A / D conversion apparatus and method that can reduce quantization errors at low cost.

  According to the second aspect of the present invention, it is possible to obtain an A / D conversion device capable of calculating true digital data with a reduced number of bits and a high number of bits based on a plurality of digital data.

  The present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing an embodiment of a battery both-end voltage monitoring device (hereinafter referred to as device) incorporating the A / D conversion device of the present invention. As shown in the figure, the device 10 includes voltage dividing resistors R1 and R2 that divide the voltage across the battery. The voltage across the battery divided by the voltage dividing resistors R1 and R2 is input to the A / D converter 11 as the input voltage V.

  In addition, a sine wave generator 12 (= generating means) is connected to the A / D converter 11 (= A / D converting means) via a DC blocking capacitor C. As a result, the A / D converter 11 is supplied with the input voltage V on which the sine wave generated by the sine wave generator 12 is superimposed. The sine wave has a positive and negative symmetry and a periodic voltage whose amplitude is larger than the voltage per 1 LSB corresponding to the reference voltage of the A / D converter 11.

  The A / D converter 11 described above samples the input voltage V described above, converts the sampled input voltage V into digital data based on a comparison with a reference voltage supplied from a reference voltage supply unit (not shown), The data is output to the microcomputer 13 (hereinafter referred to as μCOM 13).

  The above-described μCOM 13 includes a central processing unit (CPU) 13a that performs various processes according to a program, a ROM 13b that is a read-only memory that stores a processing program performed by the CPU 13a, and a work area that is used in various processes in the CPU 13a. And a RAM 13c which is a readable / writable memory having a data storage area for storing various data.

  Next, before describing the operation of the apparatus configured as described above, the A / D conversion method according to the present invention will be described with reference to FIG. First, as shown in FIG. 3, the A / D converter 11 is quantized into a stepped quantized voltage Vq indicated by a dotted line by comparing the input voltage V indicated by a solid line with the MSB corresponding to the reference voltage Vref. After that, it is encoded into digital data corresponding to the quantized voltage Vq, and A / D conversion is performed thereby.

  As described above, when the sine wave SIN is superimposed on the arbitrary input voltage Va as described above, the A / D converter 11 is supplied with the sine wave SIN having an amplitude around the input voltage Va as shown in FIG. . When the sampling period t of the A / D converter 11 described above is shorter than one period T of the sine wave SIN, within a time T corresponding to one period of the sine wave SIN, as shown by a circle, A The / D converter 11 obtains digital data of an arbitrary input voltage Va on which a plurality of sine waves SIN are superimposed. In the example shown in FIG. 3, twelve pieces of digital data are obtained.

Further, by making the amplitude of the sine wave SIN larger than the voltage V _LSB per 1 _LSB , digital data other than the digital data n corresponding to an arbitrary input voltage Va (see the black circles in FIGS. 3A and 3B). Data n-1 or n + 1 (see white circles or hatched circles in FIGS. 3A and 3B) can be obtained.

  The average value of the plurality of digital data described above is a value corresponding to an arbitrary input voltage Va. For example, when a quantization error Vs as shown in FIG. Between the corresponding digital data n and the digital data n + 1 that is one bit higher than the digital data n, the value corresponds to the quantization error Vs. As shown in FIG. 3B, when there is no quantization error, the average of the plurality of digital data described above matches the digital data n corresponding to an arbitrary input voltage Va.

  Therefore, if the digital data obtained by dividing the sum of a plurality of digital data by the number of the digital data is defined as true digital data, the A / D converter 11 does not increase the number of bits of the A / D converter 11 itself. True digital data higher than the number of bits can be obtained.

  Next, a description will be given below with reference to the flowchart of FIG. First, every time digital data is supplied from the A / D converter 11 (Y in step S1), the CPU 13a stores the supplied digital data in a temporary storage area formed in the RAM 13c and increments the counter. (Step S2). When the count value of the counter reaches a predetermined value (Y in step S3), the process proceeds to the next step S4. The predetermined value described above corresponds to the number of times the sine wave SIN is sampled within one period T when the A / D converter 11 samples every t. That is, it is considered that the period T has elapsed when the counter reaches a predetermined value.

  In the next step S4, the CPU 13a functions as a calculation means, and the input voltage data formed in the RAM 13c is obtained as a value obtained by dividing the sum of the digital data stored in the RAM 13c by the number of the digital data as true digital data. Store in the area. Then, after resetting the digital data stored in the count and temporary storage area (step S5), the process returns to step S1. Then, the CPU 13a monitors the voltage across the battery based on the true digital data obtained as described above.

  In the above-described embodiment, true digital data is calculated based on a plurality of digital data sampled and converted by the A / D converter 11 within one period T. However, even if it is not one period T, it may be anything as long as it is an integral multiple of one period T, such as time T, 2T.

  In the above-described embodiment, the sine wave SIN is superimposed on the input voltage V. However, for example, a triangular wave or a pulse-like signal may be superimposed if it is a positive and negative symmetrical and a periodic signal having an amplitude larger than the voltage per LSB.

It is a circuit diagram which shows one Embodiment of the both-ends voltage monitoring apparatus of the battery incorporating the A / D converter of this invention. It is a flowchart which shows the process sequence of CPU13a which comprises the A / D converter of FIG. It is a figure for demonstrating the A / D conversion method of this invention. It is a figure for demonstrating the quantization error of A / D conversion.

Explanation of symbols

11 A / D converter (A / D conversion means)
12 sine wave generator (generation means)
13a CPU (calculation means)

Claims (3)

An A / D conversion apparatus comprising A / D conversion means for sampling an input voltage and converting the input voltage into digital data based on a comparison between the sampled input voltage and a reference voltage,
Generating means for generating a periodic voltage larger than the voltage per 1 LSB according to the reference voltage, which is symmetric with respect to the input voltage and superimposed on the input voltage;
Based on the digital data of the input voltage on which a plurality of the periodic voltages are superimposed, the A / D conversion means intermittently samples and converts within a time that is an integral multiple of the period of the periodic voltage. An A / D conversion apparatus comprising a calculation means for calculating data. The A / D conversion device according to claim 1,
The A / D conversion apparatus characterized in that the calculation means calculates a value obtained by dividing the sum of the plurality of digital data by the number of the plurality of digital data as the true digital data. An A / D conversion method for sampling an input voltage and A / D converting the input voltage into digital data based on a comparison between the sampled input voltage and a reference voltage,
A periodic voltage larger than the voltage per 1 LSB corresponding to the reference voltage is superimposed on the input voltage, and the amplitude is symmetric.
The input voltage on which the periodic voltage is superimposed is intermittently sampled and A / D converted into the digital data,
An A / D conversion method characterized in that true digital data is calculated based on a plurality of the sampled and A / D converted digital data within a time that is an integral multiple of the period of the periodic voltage.

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