JP2005252794A - Method and device for correcting input signal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an accurate digital conversion value with a simple configuration without requiring the setting of power supply voltage with high accuracy. <P>SOLUTION: An output value of an analog-to-digital converter 2 is corrected by a prescribed correction method by using a correction constant memorized by predetermined memory 3 on the basis of an actual measurement value of a prescribed reference value of reference voltage applied to the analog-to-digital converter 2 and a target value of the reference voltage, and the corrected value is used as a digital conversion value of an analog input signal in the analog-to-digital converter 2 to be able to obtain an accurate digital conversion value with difference of a digital conversion value caused by voltage fluctuation corrected. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to correction processing of an input signal in an electronic device or the like that uses a signal digitally converted by analog / digital conversion as an input signal, and in particular, an accurate digital conversion value of an input signal regardless of a change in power supply voltage. The present invention relates to an input signal correction method and an input signal correction apparatus that can be obtained.

  In various electronic devices, devices, etc. (hereinafter referred to as “electronic devices” for convenience) using an IC having a processing function as a computer integrated into a semiconductor integrated circuit called a so-called microcomputer or the like, for example, Signals from sensors, etc. may be required in the operation. When the output signal from the sensor is an analog signal, the sensor signal converted into a digital signal is input via an analog / digital converter. Will be used.

  In such a case, for example, as shown in FIG. 3A, a reference voltage (Ref) of an analog / digital converter (indicated as “A / D” in FIG. 3) 31 provided in the electronic device S is provided. When the power supply voltage applied to the external sensor 32 is the common voltage v1, even if the power supply voltage v1 changes, the change in the output voltage of the sensor 32 and the reference voltage of the analog / digital converter 31 Therefore, the conversion value of the analog / digital converter 31 is the same as the original conversion value, and the input value recognized by a microcomputer (not shown) is not changed and no problem occurs. .

  However, as shown in FIG. 3B, in the configuration in which the reference voltage of the analog / digital converter 31 and the power supply voltage of the sensor 32 are supplied from separate power sources, the analog / digital converter is used. The reference voltage 31 and the voltage applied to the sensor 32 must be accurately set to predetermined values, respectively. If any voltage deviates from the set value, the output value from the analog / digital converter 31 is essentially Therefore, there is a problem in that even a microcomputer (not shown) is recognized by an incorrect input value and used for processing.

  As a means for solving such an inconvenience, for example, an analog / digital converter having at least two input terminals is provided, a signal to be converted is provided at one input terminal, and a voltage stabilization is provided at the other input terminal. A reference voltage stabilized by a circuit or the like is input, and a conversion value of the reference voltage when the power supply voltage is at a normal value is obtained in advance, and stored in a memory or the like. When the change occurs, the conversion value of the converted signal is corrected based on the ratio between the converted value of the reference voltage in that case and the converted value stored in the memory or the like, and an accurate converted value of the converted signal is obtained. What can be obtained is known and well known (for example, see Patent Document 1).

JP 2002-290236 A

However, in the above-described conventional device, not only a circuit for generating a stabilized reference voltage used for correction is required, but the reference voltage needs to be converted from analog to digital like the converted signal. As with the signal to be converted, an input terminal is required, leading to an increase in the price of the analog / digital converter, and an increase in the price of an electronic device using such an analog / digital converter.
The present invention has been made in view of the above circumstances, and an input signal correction method and an input signal correction capable of obtaining an accurate digital conversion value with a simple configuration without requiring a highly accurate setting of a power supply voltage. A device is provided.

In order to achieve the above object of the present invention, an input signal correction method according to the present invention includes:
An input signal correction method in an electronic device configured to convert an analog input value into a digital value using an analog / digital converter and to use the digital value for operation,
The digital conversion value is corrected to a predetermined value using a correction constant determined in advance based on an actual measurement value of a reference voltage applied to the analog / digital converter at a predetermined reference value and a target value of the reference voltage. The corrected value is used as a digital conversion value of the analog input value.
In order to achieve the above object of the present invention, an input signal correction apparatus according to the present invention includes:
An input signal correction device in an electronic device configured to convert an analog input value into a digital value using an analog / digital converter and to use the digital value for operation,
The input signal correction device uses the correction constant determined in advance based on an actual measurement value of a reference voltage applied to the analog-digital converter in a predetermined reference value and a target value of the reference voltage, The digital conversion value is corrected by a predetermined correction formula, and the corrected value is used as the digital conversion value of the analog input value.

  According to the present invention, even if a variation in the reference voltage of the analog / digital converter occurs, the output value of the analog / digital converter is corrected by using the correction constant stored in advance in the nonvolatile storage element. Unlike conventional models, it is not necessary to set the reference voltage of an analog / digital converter with high accuracy, which reduces manufacturing costs and allows accurate input with a simple configuration. It is possible to obtain a signal value and to provide a highly reliable device.

Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 and 2.
The members and arrangements described below do not limit the present invention and can be variously modified within the scope of the gist of the present invention.
First, the input signal correction apparatus according to the embodiment of the present invention is an example applied to a vehicle electronic control unit, and a configuration example thereof will be described with reference to FIG.
In FIG. 1, a vehicle electronic control unit (indicated as “ECU” in FIG. 1) 101 is the center of vehicle engine control and transmission control, and executes processing such as a program for engine control and transmission control. In addition to the microcomputer 1 (indicated as “CPU” in FIG. 1) for executing a program for input signal correction processing, which will be described later, and an analog for converting the analog output signal of the external sensor 4 into a digital signal. A digital converter (indicated as “A / D” in FIG. 1) 2 and a memory (“ROM” in FIG. 1) 3 for storing correction constants required for input signal correction processing described later are provided. It is configured as follows.

Here, the memory 3 is preferably a nonvolatile memory such as an EEPROM, for example. In addition, the vehicle electronic control unit 1 usually temporarily stores a non-volatile memory in which a program to be executed by the microcomputer 1 is stored, and arithmetic values and data obtained in various arithmetic processes. Although a RAM or the like for storing is provided, the illustration of the embodiment of the present invention is omitted to simplify the description of the embodiment of the present invention and facilitate understanding of the present invention.
The reference voltage (Ref voltage) applied to the analog / digital converter 2 and the power supply voltage applied to the microcomputer 1 are supplied from the same power supply (not shown).

FIG. 1 shows a configuration in which one sensor 4 is provided outside the vehicle electronic control unit 101 from the viewpoint of simplifying the configuration and making the description easy to understand. These are provided with various sensors for engine control, transmission control, etc., and are input to the vehicle electronic control unit 101.
The power supply voltage Vs required for the sensor 4 is supplied from a power supply (not shown) separate from the power supply in the vehicle electronic control unit 101. Note that the voltage applied to the sensor 4 is stabilized, which is a precondition for the microcomputer 1 to correctly recognize the output voltage of the sensor 4 by the input signal correction process described below. .

Next, an input signal correction process executed in the microcomputer 1 in this configuration will be described with reference to a subroutine flowchart shown in FIG.
This input signal correction process is executed as a subroutine process in the main routine when the output signal of the analog / digital converter 2 is used in the microcomputer 1, for example, for engine control. It is.
When the processing is executed, the output signal of the analog / digital converter 2 is read, and the voltage output signal of the sensor 4 is read into the microcomputer 1 as a digital signal (see step S100 in FIG. 2). .
Next, a correction constant (details will be described later) is read from the memory 3 (see step S102 in FIG. 2), and subsequently, the correction of the output value of the analog / digital converter 2 read in advance, in other words, Correction of the recognition voltage (CPU recognition voltage) in the microcomputer 1 is performed based on the following formula 1 (see step S104 in FIG. 2).
Actually, although it is a digital operation, an arithmetic expression with an analog value will be shown and described for easy understanding.

  CPU recognition voltage (V) = CPU input voltage (V) × {1+ (correction constant / resolution)} Equation 1

  Here, the CPU recognition voltage is a value after correcting the output value of the analog / digital converter 2 used for control or the like in the microcomputer 1. The CPU input voltage is a voltage value input to the microcomputer 1 as a digital value from the analog / digital converter 2, in other words, an output voltage value of the sensor 4. Although the details of the correction constant will be described later, the correction constant is obtained by Equation 2, and so to speak, should be referred to as a change (difference) in the digital value accompanying the change in the reference voltage.

Further, here, the resolution is based on a decimal number display. For example, in the case of an analog / digital converter having an output of 10 bits, the resolution in Expression 1 is 1024. That is, in other words, the maximum value of the digital conversion value in a state where a normal reference voltage (corresponding to a standard Ref voltage described later) is applied to the analog / digital converter 2.
The correction constant is calculated in advance based on Equation 2 below and stored in the memory 3 as described above.

  Correction constant = (actual ref voltage / standard ref voltage) x resolution-resolution ... Equation 2

Here, the standard Ref voltage as a target value of the reference voltage is a design value of an output voltage of a power supply circuit (not shown) that generates a reference voltage applied to the analog / digital converter 2.
Further, the actual Ref voltage is, for example, the power supply voltage of the microcomputer 1 and the reference voltage (Ref voltage) of the analog / digital converter 2 in the final adjustment stage (predetermined reference time) of the manufacturing process of the vehicle electronic control unit 101. ) Is an actual measurement value of the applied voltage. The final adjustment is necessary so that the output of the analog / digital converter 2 with respect to the output signal of the sensor 4 and the recognition value in the microcomputer 1 become a predetermined value (or a value within a predetermined range) as designed. Make adjustments.
Then, after actual measurement of the actual Ref voltage, a correction constant is calculated based on Equation 2 described above, and the value is stored in the memory 2.
The “resolution” in Equation 2 is the same as the “resolution” in Equation 1.

Next, correction of the CPU recognition voltage will be described with specific numerical examples.
First, for example, the standard Ref voltage = 5120 mv, the actual Ref voltage = 5320 mv, the output voltage of the sensor 4 = 3.00 v, and the number of output bits of the analog / digital converter 2 = 10 bits, that is, decimal display resolution. Suppose = 1024. Under this premise, if the above correction is not performed first, the CPU recognition voltage is as follows.

CPU recognition voltage = (standard ref voltage / actual ref voltage) × sensor output voltage.

That is, in the above specific numerical example, CPU recognition voltage = (5120/5320) × 3.00 = 2.89 (v).
As described above, when the Ref voltage of the analog / digital converter 2 is deviated from the standard Ref voltage during use, the microcomputer 1 has 2.89 (v) even though the sensor output voltage is 3.00 v. ) Is mistakenly recognized and used for various control processes.

On the other hand, CPU recognition voltage is calculated | required as follows by the correction | amendment in embodiment of this invention.
First, the correction constant is expressed by Equation 2 as follows: Correction constant = (5320/5120) × 1024−1024 = 40.
Therefore, it can be understood from Equation 1 that the CPU recognition voltage = 2.89 × (1 + 40/1024) = 3.00, and the output voltage of the sensor 4 is accurately recognized by the microcomputer 1.
Here, the correction constant 40 is, in other words, the difference between the maximum value of the digital conversion value at the actual Ref voltage and the maximum value of the digital conversion value at the standard Ref voltage. In other words, 40/1024 is the ratio of this difference to the maximum value of the digital conversion value at the standard Ref voltage. Multiplying the output value of the analog / digital converter 2 by (1 + 40/1024) means that the maximum value of the digital conversion value at the actual Ref voltage and the digital conversion at the standard Ref voltage with respect to the maximum value of the digital conversion value at the standard Ref voltage This means that the ratio of the difference between the maximum value and the maximum value is added to the output value of the analog / digital converter 2.

As described above, in the above description, the sensor output voltage and the CPU recognition voltage are shown as analog values for easy understanding, but in reality, the analog / digital converter 2 is used. The digital output value is corrected based on the above-described equations 1 and 2, and the digital value after the correction is recognized by the microcomputer 1 as the output value of the sensor 4.
After the CPU recognition voltage is corrected as described above, the process returns to the main rune (not shown).
Note that the processing of the above-described steps S100 and S102 only needs to be performed prior to the processing of step S104, and therefore, the processing after each processing need not be limited to the order shown in FIG.

In the above configuration example, the input signal (converted signal) of the analog / digital converter 2 is the output signal of the sensor 4, but of course, it is not necessary to be limited to the sensor 4; For example, the voltage of a specific electronic component (for example, a resistor) may be used for monitoring the operation of the circuit or controlling the operation of a circuit.
In the configuration example described above, the memory 3 is dedicated for storing correction constants. However, for example, the memory 3 may be shared with a non-volatile memory in which a program executed by the microcomputer 1 is stored. It is.

It is a block diagram which shows the structural example of the electronic control unit for vehicles by which the input signal correction apparatus in embodiment of this invention is implement | achieved. It is a subroutine flowchart which shows the process sequence of the input signal correction method performed by the microcomputer of the electronic control unit for vehicles shown by FIG. FIG. 3A is a schematic circuit diagram showing an example of circuit connection between an analog / digital converter and a sensor for explaining problems in a conventional circuit, and FIG. 3A shows a common power supply for the analog / digital converter and the sensor. FIG. 3B is a schematic circuit diagram in the case where the analog / digital converter and the sensor power supply are separate from each other.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Microcomputer 2 ... Analog-digital converter 3 ... Memory 4 ... Sensor

Claims (7)

An input signal correction method in an electronic device configured to convert an analog input value into a digital value using an analog / digital converter and to use the digital value for operation,
The digital conversion value is corrected to a predetermined value using a correction constant determined in advance based on an actual measurement value of a reference voltage applied to the analog / digital converter at a predetermined reference value and a target value of the reference voltage. An input signal correction method, wherein the correction is performed by an equation, and the corrected value is used as a digital conversion value of the analog input value.   The correction constant is obtained by dividing the target value of the reference voltage by the actually measured value of the reference voltage at a predetermined reference time, and the analog value when the target value of the reference voltage is applied to the analog-to-digital converter.・ Multiply the maximum digital conversion value of the digital converter and subtract the maximum digital conversion value of the analog / digital converter when the target value of the reference voltage is applied to the analog / digital converter. The input signal correction method according to claim 1, wherein the input signal correction value is obtained.   The predetermined correction formula adds 1 to the value obtained by dividing the correction constant by the maximum value of the digital conversion value of the analog / digital converter when the target value of the reference voltage is applied to the analog / digital converter. 3. The input signal correction method according to claim 2, wherein the added value is multiplied by an output value of the analog / digital converter. An input signal correction device in an electronic device configured to convert an analog input value into a digital value using an analog / digital converter and to use the digital value for operation,
The input signal correction device uses the correction constant determined in advance based on an actual measurement value of a reference voltage applied to the analog-digital converter in a predetermined reference value and a target value of the reference voltage, An input signal correction apparatus configured to correct a digital conversion value by a predetermined correction formula and use the corrected value as a digital conversion value of the analog input value.   The correction constant is obtained by dividing the target value of the reference voltage by the actually measured value of the reference voltage at a predetermined reference time, and the analog / digital converter when the target value of the reference voltage is applied to the analog / digital converter. Multiplying the maximum digital conversion value of the digital converter, and subtracting the maximum digital conversion value of the analog / digital converter when the target value of the reference voltage is applied to the analog / digital converter. 5. The input signal correction apparatus according to claim 4, wherein the input signal correction apparatus is a value.   The predetermined correction formula adds 1 to the value obtained by dividing the correction constant by the maximum value of the digital conversion value of the analog / digital converter when the target value of the reference voltage is applied to the analog / digital converter. 6. The input signal correcting apparatus according to claim 5, wherein the added value is multiplied by an output value of the analog / digital converter. An analog-to-digital converter that digitally converts an analog signal input from the outside; and a signal processing unit that uses an output signal of the analog-to-digital converter; and the power supply voltage of the signal processing unit is the analog-to-digital converter An electronic control unit configured to be supplied as a reference voltage of
The electronic control unit divides the target value of the reference voltage applied to the analog / digital converter by the actually measured value of the reference voltage at a predetermined reference time, and the divided value is referred to the analog / digital converter. When the target value of voltage is applied, the maximum value of the digital conversion value of the analog-to-digital converter when the target value of voltage is applied is multiplied, and when the target value of reference voltage is applied to the analog-to-digital converter from the multiplied value, A non-volatile memory preliminarily stored as a correction constant obtained by subtracting the maximum digital conversion value of the digital converter is provided,
The signal processing unit reads the correction constant from the nonvolatile memory, and corrects the digital conversion value of the analog input value input from the analog / digital converter using a predetermined correction formula using the correction constant. The corrected value is configured as a digital conversion value of the analog input value,
In the predetermined correction formula, 1 is added to a value obtained by dividing the correction constant by the maximum value of the digital conversion value of the analog / digital converter when the target value of the reference voltage is applied to the analog / digital converter. An electronic control unit characterized in that the added value is multiplied by the output value of the analog / digital converter.

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