JPS63301625A - A/d converting device - Google Patents

Abstract

PURPOSE:To accurately convert an analog input to a digital output by providing a means to generate a fixed voltage separately from a reference voltage generating part and checking digital quantity A/D converted from the fixed voltage. CONSTITUTION:A fixed voltage generating part 2, regardless of the voltage fluctuation of a supplying power source 6, receives the voltage from the supplying power source 6 and generates fixed voltage prescribed beforehand lower than the reference voltage of a reference voltage generating part 1 and an A/D converting part 3 uses the reference voltage from the reference voltage generating part 1 and A/D converts an analog input Ain and the fized voltage from the fixed voltage generating part 2. An operating part 4 compares internal A/D converting quantity which is prescribed beforehand with external A/O converting quantity in which the fixed voltage is A/D converted, then according to this compared result, correction is added to digital quantity in which the analog input is A/D converted and a digital output Dout is obtained. Thus, the supplying power source 6 is fluctuated and even when the reference voltage from the reference voltage generating part 1 is fluctuated, the analog input can be accurately converted to the digital output.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is an A/D that converts analog input into digital output.
(analog/digital) conversion device.

[Conventional technology]

Conventional A/D consisting of a reference voltage generator and an A/D converter
When performing A/D conversion in a converter, for example, a voltage is supplied from a power supply such as an on-board battery to a reference voltage generation section such as a stabilized power supply circuit, and thereby the output voltage from the stabilized power supply circuit or this output voltage is The resistor-divided voltage is applied to the A/D converter as a reference voltage. This allows A/
The D converter compares this reference voltage with the analog human power to be A/D converted, and converts this analog input into a digital output.

For example, when the reference voltage is 5V and the resolution is 10 bits, A/
When performing D conversion, the voltage of ILSB (least significant bit) at this time is as follows. Here, by inputting the analog input voltage 2.5■ to the A/D converter, a digital quantity '512'' is obtained. That is, this digital quantity '512' is a value corresponding to the analog input terminal 2.5■ becomes.

[Problem that the invention seeks to solve]

FIG. 7 is a diagram for explaining the problems of the conventional A/D conversion device, and shows the relationship between the voltage of the power supply and the amount of A/D conversion (in this case, digital amount). That is, in this figure, when the power supply deteriorates or when power is supplied to a high load, the voltage decreases, and the reference voltage from the stabilized power supply circuit also decreases by V accordingly. At this time, the digital amount obtained by A/D converting the analog input becomes larger than before the voltage of the power supply decreases, and the analog input appears to be higher than before the A/D conversion.

For example, if the reference voltage V, , for the above-mentioned 10-bit resolution A/D conversion drops from 5V to 4V, then the voltage of ILSB at this time becomes. For example, when an analog input voltage of 2.5V is input to an A/D converter, a digital quantity "640" is obtained. This digital amount “64
0″ is the reference voltage ■, is the analog input voltage 3 based on 5■
．． This corresponds to 125V, which is essentially the analog input voltage input to the A/D converter (A/D conversion). If the reference voltage fluctuates, a problem arises in that accurate digital quantities cannot be obtained.

The present invention has been made in view of the above problems, and provides an A/D converter that can accurately convert analog input into digital output even if the power supply fluctuates and the reference voltage fluctuates accordingly. The purpose is to provide a conversion device.

Means for Solving Problem C] FIG. 1 is a block diagram showing the principle configuration of an A/D conversion device based on the present invention. In the figure, reference numeral 1 denotes a reference voltage generating section, which receives a voltage from a power supply 6 and generates a reference voltage. Reference numeral 2 denotes a fixed voltage generator, which receives the voltage from the power supply 6 and generates a predetermined fixed voltage lower than the reference voltage of the reference voltage generator 1, regardless of voltage fluctuations in the power supply 6. 3 is an A/D conversion section, and a reference potential generation section l
The analog input A iFl and the fixed voltage from the fixed potential generation section 2 are A/D converted using the reference voltage from the fixed potential generator 2. 4
is the digital output D out which is not affected by the voltage fluctuation.
This is an arithmetic unit that generates .

[Function] In the above configuration, by inputting the fixed voltage from the fixed voltage generating section 2 to the A/D converting section 3, the A/D converting section 3 converts the voltage supplied from the supply power source 6 based on the fixed voltage. The fixed voltage is A/D converted based on the reference voltage outputted from the reference voltage generator 1 to obtain an external A/D conversion amount. On the other hand, the calculation unit 4 holds a predetermined internal A/D conversion amount, compares this internal A/D conversion amount with the external A/D conversion amount, and changes the analog input to the A/D conversion amount according to the comparison result. Correction is applied to the D-converted digital amount to obtain a digital output Dout. In this way, even if the power supply 6 fluctuates and the reference potential from the reference potential generator 1 fluctuates, analog input can be accurately converted to digital output.

〔Example〕

FIG. 2 is a block diagram showing one embodiment of the present invention. In this figure, 10 is a general stabilized power supply circuit as a reference potential generation section 1, and a battery 6 as a power supply 6.
A reference voltage is generated based on the supply voltage from zero. 20
and 25 are diodes and resistors forming the fixed voltage generation circuit 200 as the fixed potential generation section 2, which generate a fixed voltage V rot set lower than the reference voltage based on the voltage supplied from the battery 6; Here, the forward voltage of the diode 20 connected in the forward direction with respect to the battery 6 is used as the fixed voltage V□. 30
is an A/D converter as the A/D converter 3, which converts an analog input voltage (2) from an analog sensor 70 such as a temperature sensor and a fixed voltage V raf into digital quantities. 40 is a microcomputer as the calculation unit 4, which detects fluctuations in the reference voltage based on the digital quantity obtained by A/D conversion of the fixed voltage and corrects the digital quantity DA obtained by A/D converting the analog input voltage vA. do.

This microcomputer 40 includes a holding means for holding the internal A/D conversion amount, a taking means for taking in the external A/D conversion amount, and a comparison between the internal A/D conversion amount and the external A/D conversion amount. and a correction means that corrects the A/D conversion amount to be digitally output according to the comparison result sent from the comparison means. Further, the comparison means may send the comparison result to the correction means only when the difference between the internal A/D conversion amount and the external A/D conversion amount becomes a predetermined value or more. . Note that the microcomputer 40 generally includes a CPU, a ROM, a RAM, an I10 circuit, and the like.

The operation based on the above configuration will be explained based on the flowchart shown in FIG. 3 for the case where the power supply voltage of the battery 60 is lower than the reference voltage. First, when a switch (not shown) that drives the A/D converter W5 is turned on, in step 301, initialization is performed such as resetting various registers in the CPU and initializing the contents of the RAM. The process then reaches step 302. In step 302, a fixed voltage (2) is stored in advance in the ROM. , read out the digital ID of
D. is a digital scale. It is set as fAV and the process proceeds to step 303. In step 303, the A/D converter 3
0, the fixed voltage VW from the fixed voltage generation circuit 200 is based on the reference voltage from the stabilized power supply circuit 10. , is A/D converted, and the digital amount obtained at this time is D ra
Step 304 is reached as f.

In step 304, it is determined whether the difference between the digital 1Dref and the digital quantity Do is within the range α (for example, within the range of "±10") due to variations in A/D conversion (including quantization errors, etc.). However, if this difference is within the variation range α, the process proceeds to step 305, and if this difference is not within the variation range α, the process proceeds to step 306. In step 305, taking into account variations in A/D conversion, etc., the digital quantity D1° and the digital quantity 11DrerAv (in this case, the digital quantity D0 read from the ROM,
After this step 305 is completed, the newly set digital ND, , □9 is applied. ) and set the resulting value as Dr*rav.

In step 306, the analog input voltage (2) from the analog sensor 70 is A/D converted via the A/D converter 30, and the digital amount obtained at this time is treated as DA, and the process proceeds to step 307. In step 307, the digital fl
,, take the difference between t - (A/D converted digital amount of fixed voltage V rat) and the digital fl DrafAv, and determine whether this difference is greater than a predetermined value β (for example, "15" or more) However, if this difference is greater than or equal to the predetermined value β, that is, the voltage of the battery 6o has decreased and the reference voltage has decreased, the process proceeds to step 308, and if the difference is not greater than the predetermined value β, that is, the reference voltage has not decreased. Proceed to step 309. In step 308, the digital it VA of the A/D-converted analog input voltage {circle around (1)} is corrected using the following equation (1).

DA (Digital voltage after correction = DA (For example, before correction, when the reference voltage drops from 5V to 4V for A/D conversion with a resolution of 10 bits, the l at this time is
As already determined, the LSB voltage is the input voltage ■. 2
．． 5) If the fixed voltage V rat is 2V, the A/D converted digital quantity DA and . , becomes . In addition, the digital quantity corresponding to the fixed voltage of 2V is 410'' (in this case, the digital quantity is .fA
(corresponds to v), so it follows from equation (1) above. This digital quantity "512" corresponds to the analog input voltage of 2.5V for the reference voltage 5■ described above. This corrects the digital amount DA.

In step 309, the digital amount DA is stored in the RAM, and the process returns to step 303, where processing is performed from step 303. In this way, the fixed voltage ■1. ．． A
By checking the /D converted digital quantity Drat, even if the voltage of the battery 60 drops and the reference voltage drops, the analog input voltage can be converted into a digital quantity accurately by A/D.
can be converted.

Further, FIG. 4 is a flowchart showing a modified operation of an embodiment of the present invention, and the flowchart shown in FIG. On the other hand, the flowchart shown in FIG. 4 shows the operation of the A/D converter which can be applied not only when the power supply voltage of the battery 60 decreases but also when it increases. That is, in step 407 of this figure, the absolute value of the difference between the digital quantity Dr11f (digital quantity obtained by A/D conversion of the fixed voltage Vrer) and the digital quantity DrmfAv is taken, and the magnitude of this absolute value and the predetermined value β is determined. By comparison, it is possible to detect an increase or decrease in the power supply voltage of the battery 60. Based on this detection, in step 408, the digital amount DA obtained by A/D converting the analog input voltage vA is corrected in the same manner as step 308 in FIG. Therefore, the other steps 401-406 and 409 are the third steps.
Processing similar to steps 301 to 306 and 309 in the figure is performed.

Furthermore, FIG. 5 is a flowchart showing a modified operation of an embodiment of the present invention, in which the digital quantity D ref (digital quantity obtained by A/D conversion of the fixed voltage V rmf) and the digital it Dr @ f A V and The analog input voltage V always depends on the digital quantity D□, regardless of the difference between.

This is to correct the digital amount DA obtained by A/D converting. That is, the same processing as in the flowchart of FIG. 3 is performed by omitting step 307 (Dar Drav>β?).

FIG. 6 is a flowchart showing a modified operation of an embodiment of the present invention, in which fixed voltages V, . . . are stored in advance in the ROM. , is not used by reading out the digital quantity D0 of The digital LED
, (as so-called DrefAv). This is effective when the storage capacity of the ROM is insufficient. This figure shows the operation of the A/D conversion device. First, in step 601, initialization as described above is performed, and the process proceeds to step 602. In step 602, the fixed voltage V rpf is set to the A/D
Convert and obtain digital quantity D rllf step 60
Proceed to step 3. In step 603, the digital quantity D ref is set to D□,9, and the process proceeds to step 604. The steps after this, that is, steps 604 to 610 are the third step.
Processing similar to steps 303 to 309 in the figure is performed. However, in step 604, as described above, the digital quantity ND, f is used instead of the digital quantity D0. Furthermore, by omitting step 608, digital 1 by A/D conversion of the fixed voltage V ref as shown in FIG.
0. p, and digital flD,. The analog input voltage vA always corresponds to the digital quantity D-t regardless of the difference from fAv.
It is also possible to correct the digital Ioa by A/D conversion.

Note that the fixed voltage generating circuit 200 may use the energizer voltage of a Zener diode, the voltage between the base and emitter of a transistor, or the output voltage from a three-terminal regulator as the fixed voltage.

Although the fixed voltage from the fixed voltage generation circuit 200 is set to be lower than the reference voltage, it may be set to a voltage lower than the lowest voltage at which the A/D converter can be driven, for example.

〔Effect of the invention〕

As explained above, according to the present invention, a means for generating a fixed voltage is provided separately from a stabilized power supply circuit that generates a reference voltage, and by checking a digital quantity obtained by A/D converting this fixed voltage, a battery, etc. An A/D converter is realized that can accurately convert analog human power into digital output even if the power supply varies and the reference voltage varies.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the principle configuration of an A/D conversion device based on the present invention, Fig. 2 is a block diagram showing an embodiment of the present invention, and Fig. 3 is an operation of an embodiment of the present invention. FIGS. 4 to 6 are flowcharts showing modified operation examples of an embodiment of the present invention. FIG. 7 is a diagram illustrating problems with the conventional A/D conversion device. 1... Reference voltage generation section, 2... Fixed voltage generation section,
3... A/D conversion section, 4... Arithmetic section, 5...
A/D converter, 6... power supply.

Claims (1)

[Claims] 1. A reference voltage generator (1) that generates a reference voltage using a power supply (6), and a digital output of an analog input to be converted into an analog/digital (A/D) using the reference voltage. In the A/D converter, the A/D converter includes an A/D converter (3) that outputs a fixed voltage, which generates a predetermined fixed voltage lower than the reference voltage regardless of voltage fluctuations of the power supply (6). (2), holding a predetermined internal A/D conversion amount, and an external A/D conversion amount of the fixed voltage obtained via the A/D conversion section (3) and the internal A/D conversion amount; An A/D conversion device comprising: a calculation unit (4) that compares the values with the digital output and adds correction to the digital output according to the comparison result. 2. The arithmetic unit (4) includes a holding means for holding the internal A/D conversion amount, a taking means for taking in the external A/D conversion amount, and a holding means for holding the internal A/D conversion amount, and a holding means for holding the internal A/D conversion amount, and a storage device for storing the internal A/D conversion amount and the external A/D conversion amount. A according to claim 1, comprising a comparison means for comparing the A/D conversion amount and a correction means for correcting the A/D conversion amount to be digitally output according to the comparison result sent from the comparison means. /D conversion device. 3. The comparison means sends a comparison result to the correction means only when the difference between the internal A/D conversion amount and the external A/D conversion amount becomes a predetermined value or more. The A/D conversion device described in . 4. The A/D conversion device according to claim 2 or 3, wherein the arithmetic unit (14) comprises a microcomputer. 5. The A/D conversion device according to claim 1, wherein the fixed voltage generating section (2) generates a fixed voltage using a forward voltage of a diode. 6. The A/D conversion device according to claim 1, wherein the fixed voltage generating section (2) generates a fixed voltage based on the base-emitter voltage of a transistor. 7. The A/D conversion device according to claim 1, wherein the fixed voltage generating section (2) generates a fixed voltage using a Zener voltage of a Zener diode. 8. The A/D conversion device according to claim 1, wherein the fixed voltage generating section (2) generates a fixed voltage based on the output voltage from a three-terminal regulator.