JPH0338925A - Digital/analog converter - Google Patents

Abstract

PURPOSE:To vary a function form of digital/analog conversion comparatively freely by varying a reference voltage and the relation between a digital input and an analog quantity to be selected to vary the function of digital/analog conversion. CONSTITUTION:The D/A converter is provided with a reference voltage generating circuit 1 generating many reference voltage 6a1-6an, 6b1-6bn from 3 reference voltages 2a-2c or over and with a decode switch circuit 3 selecting a prescribed value in each reference voltage in response to a digital input 3a, outputting the result as analog quantities 4a, 4b and able to vary the relation between the digital input 3a and the output analog quantities 4a, 4b. Moreover, the function of digital/analog conversion is varied by varying at least one of the value of the reference voltages 2a, 2b, 2c and the relation between the digital input 3a and the selected analog quantities 4a, 4b. Thus, the relation of the function between the digital quantity and the analog quantity to be converted is easily varied.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] This invention relates to a digital/analog converter (hereinafter referred to as a D/A converter).
This invention relates to converters (abbreviated as converters), and in particular to techniques for varying the functional relationship between digital and analog.

[Prior art]

One example of conventional D/A converters is ``Microcomputer Age's A/D and D/A conversion technology'' (published by Nikkan Kogyo Shimbun).
There are things listed in.

FIG. 6 is a circuit diagram of the above-mentioned conventional example.

In Fig. 6, there are various ways of generating the reference potential.
In this example, the R-2R type is used. That is, V.R.E.
F is a reference voltage applied from the outside, which is divided by a plurality of 10Ω resistors (R) and 20Ω resistors (2R) to create a plurality of different reference potentials at predetermined intervals.

Then, switches 81 to S8 are activated according to BITI to BIT8 of the digital input signal to be converted into an analog signal.
By turning on and off, the output terminal (OUT2.
0UT1) is output.

FIG. 7 is a diagram showing the relationship between digital input and analog output in the above circuit.

As can be seen from FIG. 7, each part of the analog output is multiplied by an externally applied reference voltage V REF. Therefore, by changing the reference voltage VFIEF, it is possible to output an analog output corresponding to digital human power as a value scaled corresponding to the reference voltage V REF.

[Problem to be solved by the invention]

However, the conventional D/A converter as mentioned above only has a simple multiplication function as mentioned above.
In a reference potential generation circuit that does not perform simple multiplication but has a predetermined functional form, the functional form cannot be changed freely. Therefore, 1. For example, when the D/A converter itself has characteristics corresponding to a predetermined membership function, such as a D/A converter used in a fuzzy controller, the form of the function cannot be changed. ,
There was a problem.

The present invention was made in order to solve the problems of the prior art as described above, and it is possible to easily change the functional relationship between the digital quantity and analog quantity to be converted.
/A converter.

[Means to solve the problem]

In order to achieve the above object, one aspect of the present invention is as follows.

The invention is constructed as described in the claims.

That is, in the present invention, there is provided a reference potential generation circuit that generates a large number of reference potentials from three or more reference voltages, inputs each reference potential, and selects a predetermined value from each reference potential in accordance with the digital input. a decoding switch circuit that outputs an analog value as an analog value and whose relationship between the digital input and the output analog value is variable; The digital/analog conversion function can be changed by changing the VL function.

[Embodiments of the invention]

FIG. 1 is an illustration of a practical example of the present invention.

In FIG. 1, 2a, 2b, and 2c are reference voltages applied from the outside, and for example, 2a is the midpoint voltage between 2b and 20.

Further, the reference voltage 5a is obtained from the above-mentioned midpoint reference voltage 2a and reference voltage 2b via the adder circuit 1a. Also,
Reference voltage 5b is obtained from reference voltage 2a via buffer lb. Further, the reference voltage 5c is obtained from the reference voltage 2a and the base 1 voltage 2c via the subtraction circuit 1c.

above,! ! By dividing the quasi-voltages 5a, 5b, 5c by two resistors Ra□-Ra, Rb1-Rbn connected in series, a plurality of reference potentials 6a0-6a, 6b1-6bo (however, , 6 an=
6 bx) is obtained.

The parts described so far constitute the base potential generator 1.

A plurality of reference potentials 6a, 6 an, 6 b 1 to 6 bn outputted from the base Q potential generator 1 described above are given to a decode switch circuit 3, which converts the analog quantity 4
a and 4b are selected. Note that in this case, the case where the output analog quantity is a bivalent function of the input digital quantity is exemplified, so the output is 4a.

There are two of them, 4b.

The decode switch circuit 3 has a configuration as shown in FIG.

That is, the decode switch circuit 3 is constituted by an array of a plurality of switches 7 indicated by circles. By turning on and off the array of switches 7 in response to the digital input signal 3a to be converted into an analog quantity, reference potentials 6a1 to 6a11, 6 are applied to n reference potential input terminals.
b1 to b6bn are switched and output as an analog quantity to output 4a or 4b.

Further, in the array of decode switch circuits 3, the position of the switch 7 can be changed by a selection signal 3b (not shown in FIG. 2; details will be explained later in FIG. 5).

Next, the effect will be explained.

The present invention provides, for example, D having the characteristics as shown in FIG.
/A conversion. Note that A/D conversion is also possible by reversing the input and output in FIG. 4 (details will be described later).

The characteristic shown in FIG. 4 is a conversion of a functional form in which an analog quantity is a multivalued function of a digital quantity. Such conversion is necessary, for example, when incorporating a membership function in fuzzy control into D/A conversion, but it can also be applied to other than fuzzy control.

In FIG. 1, the reference voltage 5b is the reference voltage 2a at the midpoint.
(e.g. 2.5V) via buffer 1b,
Its value is, for example, 2.5■. Further, the reference voltage 5a is an output obtained by adding the reference voltage 2a and the reference voltage 2b by the adding circuit 1a, and is, for example, 4V. Further, the base voltage 5c is calculated by subtracting the difference between the reference voltage 2a and the reference voltage 2c.
It is the output calculated by c, and is 1, for example, 1V.

A plurality of resistors Ra1 are connected between the reference pressure 5a and the reference voltage 5b.
~Ran, and the reference voltage 5b and the base 41! Between the voltages 5c, the voltage is divided by a plurality of resistors Rb□ to Rbn,
A plurality of reference potentials 6a, ~6 any6b□~6, respectively
Generate bn.

The above reference potentials 6a□ to 68.6b1 to 6bn are applied to the decode switch circuit 3.

Inside the decode switch circuit 3, each switch 7 in the array is turned on and off according to the digital signal 3a.
As a result, analog quantities are output to outputs 4a and 4b.

In the above circuit, the reference voltage 2a at the midpoint is fixed, and base 4! By changing the voltage 2b and the reference voltage 2c, the functional form can be changed from characteristic A to characteristic B in FIG. That is, by changing the upper and lower limits of the reference voltage, the upper and lower widths of the reference potentials 6a1 to 6a16b1 to 6b are changed,
The shape of the function in FIG. 4 can be freely changed as shown in A and H.

Also, base 4 of the midpoint! Reference voltage 2b and 2 for voltage 2a
Make 0 asymmetric (i.e. 2a is off the midpoint)
By doing so, the characteristics shown in FIG. 4 can be made into a biased functional form.

Furthermore, by changing the position of the switch 7 in the array using the selection signal 3b, it is also possible to change the functional form from characteristic B to characteristic C in FIG.

In order to change the position of the switch 7 within the array, a configuration as shown in FIG. 5 can be considered, for example.

In FIG. 5, 8a and 8b are transistors provided at each intersection of the array. Further, the signal 38'' is one of the digital signals Q and 3a, and the signal 3b' is one of the selection signals 3b.

In the above circuit, if the selection signal 3b'' is set to ``1'' and the transistor 8b is turned on, this line is always in a conductive state, and the switching by the signal 3a' and the transistor 8a becomes almost non-existent.

On the other hand, if the signal 3b' is set to "O" and the transistor 8b is turned off, a switch by the signal 3a' and the transistor 8a will work, and the above-mentioned switch 7 will be provided at this intersection.

As described above, the position where the switch 7 is provided can be freely changed.

As described above, with a relatively simple configuration, the characteristic A in Fig. 4,
The function form can be changed like characteristic B and characteristic C. Therefore, if the present invention is applied to fuzzy control, for example, membership functions can be easily tuned.

In the above embodiment, three reference voltages 2a, 2b, and 2c are used as externally applied reference voltages, but it is also possible to provide more than four reference voltages to achieve further different characteristics. It's easy to do.

Next, FIG. 3 is a block diagram of an embodiment of a digital/analog converter (hereinafter abbreviated as a D/A converter) using the A/D converter of the present invention described above. This example is -
A successive conversion type voltage comparison type converter is shown as an example.

In FIG. 3, the D/A converter 10 is the above-described D/A converter of the present invention, and compares the analog voltage Vo to be output with the analog input voltage 13 to be converted using a comparator circuit 2. , control circuit 14 and register 1
1, the output of the D/A converter 10 is successively changed, and when the data in the register 11 is taken out when it becomes equal to the analog input voltage 13, the data becomes digitally converted data.

Incidentally, if the D/A converter 10 has two analog outputs 4a and 4b as in the embodiment shown in FIG. 1, two comparator circuits 12 may be provided and comparisons may be made between each.

〔Effect of the invention〕

As described above, according to the present invention, there is provided a base potential generation circuit that generates a large number of reference potentials from three or more reference voltages, and a base potential generation circuit that inputs each reference potential and generates a base potential for each base in accordance with digital input.
N! A decode switch circuit that selects a predetermined value in the potential and outputs it as an analog value, and that has a variable relationship between the digital input and the output analog value, and selects the value of the reference voltage and the digital input. By configuring the digital/analog conversion function so that it can be changed by changing at least one of the relationships with the analog value, it is possible to change the function form between digital and analog relatively freely./A A converter can be realized. This effect can be obtained. If the D/A converter of the present invention is used as a D/A converter in an A/D converter of a fuzzy controller, conversion using a membership function can be easily performed. This effect can be obtained.

[Brief explanation of drawings]

FIG. 1 is an embodiment of the present invention, FIG. 2 is an embodiment of a decode switch circuit, and FIG. 3 is an embodiment of an A/D converter using the D/A converter of the present invention. 4 is a diagram showing changes in conversion characteristics in the present invention, FIG. 5 is a diagram showing the configuration of an array in the decode switch circuit, and FIG. 6 is an example diagram of a conventional D/A converter. , FIG. 7 is a diagram showing the conversion characteristics of a conventional D/A converter. <Explanation of symbols> 1...Reference potential generation circuits 1a, 1b, lc - Arithmetic units 2a, 2b, 2G...Reference voltage 3 given from the outside
...Decode switch circuit 3a...Digital input to be converted 3b...Selection signals 4a, 4b...Analog outputs of conversion results 5a, 5b,
5cm reference voltage 68, ~6an, 6b, ~6b, ---Reference potential 7...
・Switches 8a, 8b in the array...MoS transistors

Claims (1)

[Claims of Claims] A reference potential generation circuit that receives three or more reference voltages having different values and outputs a greater number of reference potentials than the input reference voltages by dividing the reference voltages with resistance. inputting each reference potential output from the reference potential generation circuit, selecting a predetermined value from each of the reference potentials according to the digital input to be converted into an analog value, and outputting it as an analog value; a decoding switch circuit capable of changing the relationship between the digital input and the selected analog value according to an external control signal, and at least one of the value of the reference voltage and the relationship between the digital input and the selected analog value. A digital/analog converter characterized in that a digital/analog conversion function is made variable by changing .