JP2000193532A - A/d converting circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain effects equivalent to those in a case that a constant is changed without changing a constant by performing conversion through the use of computations of a computing means to compute the output of an A/D converter and a constant of a storage means to store constants necessary for computations. SOLUTION: A temperature detecting element 102 is formed of an NTC thermistor serially connected to a resistor 103, and connected between the positive and negative electrodes of a D.C. power source 101. The voltage, a signal S110, of the node between the temperature detecting element 102 and the resistor 103 is changed by temperature, the signal 110 is inputted to the A/D converter 104, and the result of A/D conversion is outputted. A computing means 105 performs predetermined computations with the output of the A/D converter 104 as input and outputs its result. The computations of the computing means 105 are performed with data hold in RAM 106 as a constant, and the output computed by the computing means 105 and the RAM 106 is held in RAM 107. The program of program RAM 108 is constituted so that the data held in the RAM 107 may be used as data on which programs operate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
/ D conversion circuit.

[0002]

2. Description of the Related Art In a conventional A / D converter circuit, an NTC thermistor and a divided voltage of a resistor are input to an A / D converter, A / D converted by the A / D converter, and used.

[0003]

However, the accuracy of temperature detection is important, and there are many situations in which the detected temperature must be changed depending on the result of the temperature detection. Therefore, in such a case, the constant of the resistor connected in series with the thermistor was changed to shift the detection temperature.

It is an object of the present invention to provide a circuit which has the same effect as changing a constant without changing the constant.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention converts an A / D conversion result by an A / D converter by a certain algorithm.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention specifically has a DC stabilized power supply and an A / D converter for implementing the above-mentioned means, and connects a temperature detecting element and a resistor in series to form a DC power supply. Connect between positive and negative, and input the divided voltage between the temperature detecting element and the resistor to the A / D converter,
By performing A / D conversion, the temperature detected by the temperature detecting element is recognized based on the output of the A / D converter.
The A / D conversion circuit has an operation means for operating the output of the A / D converter, and a storage means for storing a constant required for the operation. This is performed by using the constant of the means, and the detected temperature is changed without changing the resistance.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

In FIG. 1, a temperature sensing element 102 is constituted by an NTC thermistor, connected in series with a resistor 103 and connected between the positive and negative electrodes of a DC power supply 101.

The voltage at the connection point between the temperature sensing element 102 and the resistor 103 and the signal S110 change with temperature.
The signal S110 is input to the A / D converter 104, and the result of the A / D conversion is output. Also,
The calculation means 105 performs a predetermined calculation with the output of the A / D converter 104 as an input and outputs the result.

The operation of the operation means 105 is performed by the RAM 1
In this configuration, the data held in 06 is calculated as a constant, and the result calculated by the calculating means 105 and the RAM 106 is output from the calculating means 105. This output is output to the RAM 107,
107.

Further, an arbitrary program is written in the program ROM 108, and the program is configured to use data held in the RAM 107 as data for operating the program.

In this embodiment, the A / D converter 104,
The RAM 106, the RAM 107, the arithmetic means 105, and the program ROM 108 are configured to be built in the one-chip microcomputer 109.

Next, referring to FIG.
An example in which the data 8 uses the data in the RAM 107 will be described.

A program ROM 108 is a RAM 107
Has reference data A to be compared with the data held in.

When the program starts, first the RAM
The data 107 and the reference data A are compared. R in comparison
If the data of AM 107 is large, process A is performed, and if it is small, process B is performed.

FIG. 3 shows the A / D due to a change in resistance due to a change in the temperature of the thermistor of the temperature sensing element 102 in FIG.
The output of the converter 104 is changed by the resistor 103 at 10 kΩ.
And 11 kΩ.

In the case of the configuration of this embodiment, the output of the A / D converter 104 increases as the temperature rises. When the resistance 103 connected in series to the temperature sensing element 102 is changed, data shifts.

Here, the resistance of the temperature-sensitive element 102 at an arbitrary temperature is Rs, the constant of the resistor 103 is R1, and the output of the A / D converter 104 is DT1 R2 when the combination of Rs and R1 is R1 and R2 is R1. Assuming that the output of the A / D converter 104 in the case of the combination of Rs and R2 is DT2, R1 / (Rs + R1) = DT1 (1) R2 / (Rs + R2) = DT2 (2)

According to the equations (1) and (2), DT2 is replaced by DT1 and R1, R
R2 · DT1 / (R1−DT1 · R1 + R2 · DT1) = DT2 · (3) Since R1 and R2 are both constants, if R2 = a · R1 (a is a constant), the equation (3) is obtained. Is a · DT1 / (1− (1−a) · R1) = DT2 (4)

Therefore, the output of the A / D converter 104 at an arbitrary temperature using the resistor 103 having an arbitrary constant is subjected to the operation of the equation (4) to obtain the A / A when the resistor 103 is multiplied by a. It can be converted to the output of a D converter.

The reference data A for comparison in the operation flowchart of the program ROM 108 is stored in the ROM and cannot be rewritten.

When it is necessary to change the temperature at the branch point between the processing A and the processing B, the constant of the resistor 103 is usually changed.

However, the arithmetic means 105 is configured to execute the equation (4) according to the configuration of the present embodiment without changing the constants, and the constants of R1 and a are stored in the RAM 106. Using the constant of R1 (4)
Configure to execute the expression. Therefore, the same effect can be obtained only by rewriting data without changing the constant of the resistor 103.

[0024]

According to the present invention, with the above-described structure,
It is possible to configure a temperature detection circuit that is not affected by the completion of the structure of the temperature detection portion.

[Brief description of the drawings]

FIG. 1 is a block diagram of an A / D conversion circuit according to one embodiment of the present invention.

FIG. 2 is a flowchart showing an operation example of the program ROM.

FIG. 3 is a diagram showing a change in the thermistor output with temperature and a change with resistance.

[Explanation of symbols]

102: temperature sensing element (NTC thermistor), 103: resistance,
104: A / D converter, 105: arithmetic means, 10
6: RAM, 107: RAM, 108: program ROM, 109: one-chip microcomputer

Claims (1)

[Claims] A DC stabilized power supply and an A / D converter are provided. A temperature detecting element and a resistor are connected in series to be connected between plus and minus of the DC power supply. Input voltage to the A / D converter.
A / D conversion allows the A / D converter to recognize the temperature detected by the temperature detection element based on the output of the A / D converter.
The D conversion circuit has an operation means for operating the output of the A / D converter, and a storage means for storing a constant required for the operation. An A / D conversion circuit characterized in that conversion is performed by using constants of means.