JPH01140016A - Dc voltage generator - Google Patents

Abstract

PURPOSE:To obtain a device comprising a small number of components and having high reliability, by providing an A/D converter converting digitally an analog DC voltage output from a variable gain amplifier and feeding it back to an arithmetic element, so as to minimize an error correction circuit. CONSTITUTION:Digital DC voltage data (DDV) subjected to corrective computation in an arithmetic element CPU 120 and outputted therefrom are inputted to and stored in RAM 14 and changed into an analog DC voltage (ADV) in DAC 20. This ADV is led to a variable gain amplifier 30 composed of an operational amplifier and a variable attenuator, and it is amplified therein by a necessary amount and outputted to change over an output voltage range (measuring range). This ADV is converted into DDV by an A/D converter 15 and fed back to the CPU 120. Thereby zero data are set in the DAC 20 first, an offset error is corrected, and thereafter the correction of a gain error is conducted by the same arithmetic operation cycle. Through this cycle, accordingly, the correction for the entire measuring range is completed. Therefore from these operations a, DC voltage in the necessary measuring range is obtained thereafter without any error.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an improvement of a DC voltage generator that simplifies the circuit configuration for correcting errors included in analog DC voltage output.

<Conventional technology> The conventional technology will be explained below using the drawings.

FIG. 3 is a block system diagram showing an outline of a conventional DC voltage generator.

In FIG. 3, the main parts α of the DC voltage generator are registers 1. A digital/analog converter (referred to below as r) that converts the digital DC voltage from register 1 into an analog DC voltage.
The operational amplifier 3a and the variable attenuator 3b amplify the 2° converted analog DC voltage (abbreviated as 'DAcJ) to the desired DC voltage according to the measurement range and output it to the output terminal α.
It is constituted by a variable gain amplifier 3 consisting of. In this main part α, the analog-converted DC voltage has an offset error when the voltage is zero and a gain error when the voltage is 100%. Therefore, from a first random access memory (hereinafter referred to as rRAM) 4, a first DAC 5, and a first fixed attenuator (hereinafter referred to as "ATTJ") 6, The offset error correction signal of the offset error correction circuit β is supplied to the adder/subtractor 7 to cancel the offset error.
10, and an adder/subtracter 11 that adds or subtracts the output of the second ATT 10 to the reference voltage Vref.
A gain error correction signal of is supplied to the DAC 2 to cancel the gain error.

Here, the main part α, the offset error correction circuit β, and the gain error correction circuit γ are read-only memories (rR
It is controlled by an arithmetic unit (hereinafter referred to as rCPU) 12 comprising, for example, a processor, which performs necessary arithmetic operations using arithmetic expressions and the like stored in OM (abbreviated as OM) 13.

With such a configuration, an accurate DC voltage with errors corrected is output from the main part α according to the measurement range.

<Problems to be Solved by the Invention> However, in this conventional DC voltage generator, since each error correction circuit occupies a considerable portion of the main part α, the overall circuit configuration becomes complicated and There are many problems, such as the large number of circuit components, increased product price, complexity of manufacturing, increased stock of used parts, and difficulty in maintenance.

The present invention has been made in view of the problems of the conventional technology, and it is possible to generate an inexpensive DC voltage with a small number of parts, a small size, and a condylar property by minimizing the error correction circuit. Our goal is to provide the equipment.

Means for Solving Problems〉 To achieve the above-mentioned object, the DC voltage generator of the present invention converts a digital DC voltage into an analog DC voltage, and uses a variable gain amplifier to generate a desired analog voltage according to the measurement range. Gain error and offset error included in the output analog DC voltage in a DC voltage generator that amplifies and outputs DC voltage.

and a calculation unit that calculates a correction value for analog DC voltage output for each measurement range in order to correct DC voltage characteristics based on these errors, and a random access memory that stores data calculated by the calculation unit. , a digital/analog converter that converts a digital DC voltage from the random access memory into an analog DC voltage and outputs it to the variable gain amplifier; and a digital/analog converter that converts the analog DC voltage output from the variable gain amplifier into a digital DC voltage. and an analog/digital converter that feeds back the converted data to the arithmetic unit.

<Example> Hereinafter, an example of the present invention will be described in detail based on the drawings. In the following drawings, parts that overlap with those in FIG. 3 are given the same numbers, and their explanations will be omitted.

FIG. 1 is a block system diagram showing an outline of the DC voltage generator of the present invention.

In Figure 1, in order to correct the gain error, offset error, and DC voltage characteristics based on these errors that exist in the DC voltage converted to analog, the DC voltage generator is connected to the analog DC voltage output for each measurement range. a calculation unit (CPU) 120 that performs correction calculations;
This R
A DAC 20 that inputs digital DC voltage data stored in the AM 14 and converts it into an analog DC voltage;
A variable gain amplifier 30 consisting of an operational amplifier and a variable attenuator for amplifying and outputting the analog DC voltage from the DAC 20 by the required amount and for switching the output voltage range (measurement range); An analog/digital converter (hereinafter abbreviated as "ADC") 15 inputs an analog DC voltage output from CP tJ 120, converts it into a digital DC voltage, and feeds it back to CP tJ 120 via a data bus.

FIG. 2 is a flowchart for explaining the present invention.

The present invention will be described in detail below with reference to FIGS. 1 and 2.

First, the offset error and gain error were combined.

The maximum value of the error is the total number of levels (2n) of DA C20.

For example, if the DAC 20 is set to 12 bits (1
=12. In other words, it is assumed that the total number of levels is 4096 levels). Also, the maximum value of the error shall be 1% or less of the full scale. At this time, in the DAC 2, 40 levels out of all levels are allocated for error correction.

First, offset errors are corrected.

The offset error value differs for each measurement range.

Therefore, it is necessary to correct offset errors for all measurement ranges. In order to use the CPU 120 to perform correction calculations for the analog DC voltage output for each measurement range, first, the CPU 120 and ROM 130 are used to perform R
Zero data is set in the DAC 20 via the AM 14. The zero data at this time is stored at an arbitrary address in the RAM 14. In the variable gain amplifier 30, a measurement range in which offset error should be measured is switched and selected using a variable attenuator.

An analog DC voltage based on zero data is output from the DAC 20. Zero data corresponding to the current input value of the DAC 20, including the analog DC voltage from the DAC 20 and an offset error based on the selected measurement range.
The analog DC voltage output VSTLO (where n is used to indicate that it differs depending on each measurement range) is
It is output from the variable gain amplifier 3o. This zero data
Analog DC voltage output Vsπ. is digitally converted via the ADC 15, and fed back via the data bus as data for performing correction calculations in the CPU 120,
Operate the CPU 120 and store the measurement range/- in the RAM 14.
+! It is stored as an offset error corresponding to the load value.

Such a cycle is executed over all measurement ranges.

After the offset error correction cycle is completed, the gain error is then corrected.

The gain error correction is performed by adjusting the total number of levels of the D A C 20 stored in advance at an arbitrary address in the RAM 14
Full scale data (hereinafter abbreviated as rF-S data) Dps, which is the value (4o56 level) obtained by subtracting the level assigned for error correction (for example, 40 level) from the 4096 level), is controlled by the CPU 120. Set in the DAC 20 based on the signal.

In the variable gain amplifier 30, a variable attenuator is used to switch and select a measurement range for gain error correction.

The analog DC voltage based on the F-S data Dps is DA
It is output from C20. F-S data including gain error based on the output of this DAC 20 and the selected measurement range I) F-S analog DC voltage output v corresponding to ps
Qπ (where n is used to indicate that it varies depending on the measurement range) is output from the variable gain amplifier 30. This F・S analog DC voltage output vo1 is A D
Digital conversion via C15 and C via data bus.
Feedback is provided to the PU 120. The CPU 120 calculates the value based on this fed-back value (Val), the stored zero data analog DC voltage [(Vsuo) corresponding to this measurement range, and the F-S data DFS in the measurement range at that time. The gain error correction/slope characteristic (represented as LSB) is: LSB=Dps/(Vc+u Vsuo) −(1
). This correction calculation result is stored in the RAM 14 as measurement range data at that time. Then, the intermediate value (linearity) of this slope characteristic is determined. For this purpose, the required intermediate value is set and the zero/FS intermediate data analog DC voltage value Vl)ujN is used to represent the intermediate value) is measured.

The linear correction value calculated by the CPU 120 is (Vc T
L r XLSB) -Vs TLO- (2). This calculation result is additionally stored in the RAM 14 as detailed slope characteristic data in the measurement range at that time. Such a calculation cycle is executed for all intermediate values necessary for linear correction. In this way, correction characteristics for offset errors, gain errors, and intermediate values accompanying these in the measurement range are obtained.

When this calculation cycle is completed, similar correction calculations are performed for other measurement ranges. Is it corrected in this way for all measurement ranges? ii Do calculations.

Since the correction over the entire measurement range is completed through such a cycle, the DC voltage in the required measurement range can be obtained without error based on these results.

<Effects of the Invention> As described above, the present invention has been specifically explained along with the examples.
According to the DC voltage generator of the present invention, the offset error and the gain error can be corrected with one system of closed draw 1, so the overall configuration can be made simple, so the entire device can be downsized and the necessary The number of parts can be reduced,
This has the effect of simplifying the manufacturing process, reducing parts stock, achieving a significant overall cost reduction, and realizing highly reliable products due to easier maintenance. .

[Brief Description of the Drawings] Fig. 1 is a block system diagram showing an overview of the DC voltage generator of the present invention, Fig. 2 is a flowchart for explaining the invention, and Fig. 3 is an overview of a conventional DC voltage generator. FIG. α...Main part, 2.20...Digital/analog converter (DAC), 3, 30...Variable gain amplifier, 1
2.120... Arithmetic unit (CPU), 14... Random access memory (RAM), 15... Analog/digital converter (ADC).

Claims (1)

[Claims] In a DC voltage generator that converts a digital DC voltage to an analog DC voltage, amplifies it to a desired analog DC voltage according to the measurement range using a variable gain amplifier, and outputs it, the gain error and offset included in the output analog DC voltage. In order to correct errors and DC voltage characteristics based on these errors, there is a calculation section that calculates a correction value for the analog DC voltage output for each measurement range, and a random access memory that stores the data calculated by the calculation section. memory and the random
a digital/analog converter that converts a digital DC voltage from an access memory into an analog DC voltage and outputs it to the variable gain amplifier; and a digital/analog converter that converts the analog DC voltage output from the variable gain amplifier into a digital DC voltage and performs the calculation. A DC voltage generator comprising: an analog/digital converter that provides feedback to the DC voltage generator;