JPS61125231A - Analog-digital converter - Google Patents

Abstract

PURPOSE:To apply accurately A/D conversion to a value to be measured and the discriminate whether the value to be measured is a setting value or below by providing a function of a digital comparator in addition to the A/D converting function. CONSTITUTION:A main body section of an A/D converter applies sequential comparison type A/D conversion by operating normally a 3-output buffer 109. Further, the A/D converter acts like a digital comparator. That is, the 3-output buffer 109 is brought into the floating state by using a signal from ports P1.3 of a microcomputer 106 to output a prescribed setting value to the A/D converter 100 from ports P0.0-P0.7. The setting value is subjected to A/D conversion and the setting analog value obtained in this way is inputted to a non- inverting terminal of the comparator 112. An analog value Vin to be measured and the setting analog value are compared by comparing whether a value inputted to the port 1.0 is logical H or L.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an analog/digital (A/D) variable control device.

[Prior Art] With the development of microcomputers in recent years, many industrial devices and household devices have come to be digitally controlled.

The objects to be controlled in industrial equipment and household equipment are often analog variables (e.g. temperature, temperature), and therefore A/D converters and D/A converters are very useful as interfaces. It has come to occupy an important position.

FIG. 1 shows the configuration of a conventional successive approximation type A/D converter.

In FIG. 1, 101 is an 8-bit D/A converter;
102 is a holding register composed of eight D-FFs, 103 is a shift register composed of eight D-FFs, 104 is a comparator, and 1θ5 is a reference power source for the D/A converter. In such a configuration, the MSH of the holding register 102 is set to 1 by the A/D conversion star value code.
Set it so that it stands upright. That is, D/A converter +
(+0000000) is input to 01, and the corresponding analog 4f1vref card D/A converter lO1
Color comparator 104 (7) Input to the positive end. In the comparator 104, the analog input voltage V to be measured is
and the analog e vrefn are compared, and if v1n≧vref, the comparator 104
The output of the comparator 104 becomes Low, and if vin≦vref, the output of the comparator 104 becomes the old gh. When the output of the comparator 104 is old gh, the 8th pin (MSB
) is reset, and when the output is Low, the 8th bit of the holding register 102 remains at 1+. Then, the next 7th bit of the holding register 102 is set to 1, and the same process is repeated. That is, if the output of the comparator 104 is old gh, the D/A converter lot has (01
000000) is input, and if the output is the same or Low, D
(11000000) is input to the /A converter +01. In this way, the D/A setting value is determined bit by bit starting from the 8th bit (MSB) of the holding register 102, and finally it is decided whether to set the LSH to 1 or reset it. With this, A/D conversion is completed. Then, as a result of A/D conversion, a D/A converter l
The last digital value set to ot is output.

FIG. 2 shows how 1 is set one by one in the holding register 102 for a certain analog Ichikawa to be measured, starting from the 8th bit (MSB). In other words, first of all, MS
By setting 1 to H, l/2 full scale (F
Compare the analog E of S) and the voltage to be measured. In this case, since the power of the set value is lower than the voltage to be measured, next, 1/4 FS (7 bits) (l=1) is added and the voltage to be measured and the output of the D/A converter 101 are compared. . In this case, the set value (output of the D/A converter) is larger than the voltage to be measured, so next, instead of 1/4 FS, 1/8 F
S (6th bit) is added and applied, 4111 constant voltage and D/
Compare with the output of A converter. By doing this, the set value of the D/A converter will gradually approach the measured voltage value, and after the comparison at the LSB of the holding register 102 is completed, the unmeasured voltage value and the D/A converter The difference from the output of is within the quantization error. The time required for such A/D conversion is (clock time)×(number of bits/1). That is, since the holding register 102 has 8 bits, a time corresponding to 9 clocks is required in this case.

By the way, when applying A/D conversion while controlling a controlled object, there are cases where you want to obtain an accurate value by A/D conversion, and cases where you want to obtain whether the value is greater than or equal to a certain set value -F. There are cases. For example, if you want to maintain a certain heat source at 180°C, read the temperature from the sensor using A/D conversion, calculate how far that temperature value is from 180°C, and calculate how much the power supply will deviate from that. Control method to determine whether the temperature is good and whether the value is >80°C
There is a control mode in which it is determined whether the power is above or below, and if it is below, a predetermined amount of power is supplied, and if it is above, no power is supplied. The former determines a certain supply amount from an accurate value, and the latter determines the supply amount from an accurate value, and the latter
The supply amount is determined only from the following information. In this way, in A/D conversion, when there are a plurality of inputs to be measured, there are cases where the former method is used and cases where the latter method is used.

However, in the conventional A/Dg converter as described above, a predetermined process is always followed. That is, for example, in the above example, a conversion time equivalent to nine clocks is always required. Therefore, for example, even if you only want to know whether the measured value is above or below a certain set value through A/D conversion as described above, the conversion time equivalent to 9 clocks is always used. , was unable to use the equipment properly and efficiently.

[Objective] An object of the present invention is to solve the above-mentioned problems, to accurately A/D convert a measured value using successive approximation logic, and to perform A/D conversion of a measured value to ensure that the measured value is greater than or equal to a certain set value. An object of the present invention is to provide an A/D converter that can determine whether

Embodiment] FIG. 3 is a block diagram showing an embodiment of an A/D conversion device according to the present invention. In FIG. 3, 108 is a holding register, and 107 is a shift register, in which a predetermined value is set in the holding register 108 every clock. 1
09 is a 3-output (3-state ζ) buffer, which manually inputs the output of holding register +08. 110 is a D/A converter, which manually outputs the output of the three-output puff γ108. 1st I is the reference power supply of the D/A4J converter 110, 112 is a comparator, and is a D/A converter! The analog output signal from 10 and the analog signal to be measured are input, and the comparison result is output to the holding register 108. These shift register 107, holding register 108 . 3 outputs 7 y 1
offl.

The D/A converter 110, the reference %@Ill, and the comparator 2 constitute the main body of the A/D converter.

1of is an 8-bit microcomputer that controls the main body of the A/D converter. The boat po, o to Po, 7 of the microcomputer 106 is A/
After the D conversion is completed, the digital value held in the holding register 108 is input, and the D/A converter 110 directly outputs a predetermined digital value. Bo) Pl, 1 is A/Df
Outputs a signal instructing the start of conversion to shift register 107 and holding register 1 (18. Baud) Pl,
2 inputs the A/D conversion end r signal from the holding register 108. Boat P1.3 outputs a control signal to three-output puffer 108. Baud 1-Pl, 0 inputs the output from comparator ]12.

In such a configuration, the main body of the A/D converter converts the successive approximation type A by normally operating the 3-output buffer l0i1 in the same way as the conventional A/D converter explained in FIG. /D conversion can be performed.

Furthermore, the A/D converter of the present invention can be operated as a digital comparator in the following manner.

That is, first, the signal from the boat P1.3 of the microcomputer IO[i causes the 3-output buffer 1011 to
1) in the a-ting state, boats PO10 to PO4
7 outputs a predetermined setting value to the D/A'Ii converter 110. This set value is D/A converted by the D/A converter 110, and the set analog value thus obtained is sent to the comparator 11.
It is input to the positive terminal of 2. Then, the comparator 112 compares the set analog value and the measured analog value V, and sends the result to the microcomputer 106 (Baud) Pl,0
Enter. Boat P1. By checking in the microcomputer 10B whether the value input to O is old gh or Low, the measured analog value V and the n set analog value can be compared.

By using such a digital comparator function, control as shown in FIG. 4, for example, can be performed. That is, FIG. 4 shows a control flow when the measured value input is a temperature sensor, the controlled object is a heat source, and the manipulated variable or the number of energizing pulses of the power source. Note that this control procedure is stored in the ROM within the microcomputer 10S. Fourth
As shown in the figure, in step STP], the port P1.3 of the microcomputer 106 is set to ON (1), and the 3-output cover 7109 is placed in a floating state. Next, in step 5TEP2, D/A converter 1 is transferred from boat P0.7 of microcomputer +06.
At 10, a temperature sensor outputs a digital value corresponding to 180°C. Next, in step 5TEP 3, it is determined whether the human power of the microcomputer 10B (Pl, O) is 1()light), and if YES, the process proceeds to step 5TEP 4, where energization to the controlled object is started, Next, the process proceeds to step 5TEP 5, in which a timer is activated for a time of 1 second, and then, in step 5TEP 8, energization to the controlled object is terminated after a time of T seconds has elapsed. Of course, other commands may be executed during this one second, and if NO in step 5TEP3, the control flow is not executed and the process moves to the next task.

Also, the baud of the microcomputer 108]・Po, 0
By setting the setting values output from ~ to po and 7 to the D/Af converter 110 to two different values, for example v1 and v2, and respectively implementing the control flow described in 1- for these values Vl and v2. , it can be confirmed whether the analog value to be measured is between the values Vl and v2.

Furthermore, the A/D conversion device of the present invention allows certain settings to be made!
It is possible to carry out a soft start by performing step-by-step control at the time of starting operation so that the value becomes 1. In other words, the manipulated variable is changed when the controlled variable reaches 50% of the set value in the A/D conversion device of the present invention, when it reaches 70% of the set value, and when it reaches 90% of the set value. When taking the step of guiding the controlled variable to the set value, first determine whether the controlled variable is greater than or equal to 50% of the set value.

Since it is only necessary to know whether it is 70% or less and whether it is 80% or more or less, the present invention A/D
The converter operates as a digital comparator, and as the controlled variable approaches the set value, finer control becomes necessary, so once the controlled variable exceeds 80% of the set value, the A/
It is sufficient to obtain an accurate value by D conversion and apply feedback to the controlled object based on this. In this way, with the A/D conversion device of the present invention, the digital comparator function and the A/D conversion function can be appropriately used depending on the object to be controlled, and the object to be controlled can be controlled extremely efficiently. .

In addition, in the second embodiment, the main body of the A/D converter and the microcomputer were made independent; however,
The main body may be built into a microcomputer. By doing so, it is possible to obtain further advantages in terms of software and hardware.

[Effects] As described above, according to the present invention, it is possible to provide an A/D conversion device having a digital comparator function as well as an A/D conversion function.

This allows A/D
The conversion function and the digital comparator function can be used appropriately, and even for the same control target, the digital comparator function and the A / The A/D conversion function can be used and applied separately, and therefore the A/D conversion device can be used extremely efficiently.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a conventional successive approximation type A/D converter, Fig. 2 is a diagram showing the A/D conversion process in the converter, and Fig. 3 is a diagram of an A/D conversion device according to the present invention. FIG. 4 is a block diagram showing an example of the embodiment. FIG. 4 is a diagram showing an example of a control flow when the same A/D conversion device is applied. +06...Microcomputer, +07...Shift register, +08...Holding register, 10i1...3 output buffer, +10...D/A converter, Ill...Reference power supply, 112... Comparator.

Claims (1)

[Claims] A D/A converter; a comparator that compares the analog value output from the D/A converter with the analog value to be measured; and based on the comparison result of the comparator, successive input means for inputting digital values for successive approximation into the D/A converter; direct input means for directly inputting digital values into the D/A converter; and digital values from the successive input means and the direct input means. Select any one of the digital values from the input means and
1. An A/D conversion device comprising: switching means for inputting the input to the A/D converter; and means for independently reading the comparison result of the comparator.