JPS5872218A - Controlling device for air conditioner - Google Patents

Abstract

PURPOSE:To improve the resolution of an A/D converter to realize the same performance as that of a higher converter through the lower converter by dividing a temperature measuring range into plural ranges and setting up the level of a temperature range by a level converter prepared in each temperature range. CONSTITUTION:A low-temperature range level converter 5a and a high-temperature range level converter 5b are connected in parallel to a temperature detector 1 and an A/D converter 3. A signal from the detector 1 is applied to the converters 5a, 5b, respectively, and in accordance with a signal from a central processing unit 4, the converter 5a or 5b converts the signal from the detector 1 into analog voltage and the analog voltage is inputted to the A/D converter 3. The digital signal converted by the converter 3 is supplied to the CPU 4, which executes prescribed operation to control a cooled heat source apparatus. Since the temperature range is divided into plural ranges and an analog level is set up in each range, the converter 3 is improved at its resolution and the same performance as that of a higher A/D converter is realized by the lower A/D converter 3.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air conditioner, and particularly to a control circuit for an air conditioner suitable for use with a heat pump type chiller unit NC having a wide temperature control range.

As shown in FIG. 1, the conventional control device of the type has a built-in thermistor installed on the object to be measured, and converts the signal from the large temperature detector 1 into an analog voltage using the level converter 2. Input this output to analog-digital converter 3,
This output is taken into the central processing unit 4 and calculated, and the cooling/heating source (not shown) is controlled in the controller. In this case, if the measurement temperature range is TX ('C) and an N-bit configuration analog-to-digital converter is used, the output of the level converter is converted into an analog-to-digital converter so that the resolution per 1°C is expressed as 2N/T. Since the input voltage range of the converter was set to be the same across all seven voltage ranges, the wider the measurement temperature range, the lower the resolution of the analog-to-digital converter9. In addition, in general, the change in electrical resistance of a thermistor due to temperature is given roughly. B is a thermistor constant, Ta is a reference temperature, and the resistance value at this time is Ra. In this way, linearity is poor because the resistance change is expressed as an exponential function.

For this reason, the wider the measurement temperature range, the larger the error, and the smaller the output voltage of the level converter per degree Celsius, which caused problems in terms of noise resistance.

An object of the present invention is to provide a control device for an air conditioner that solves the above problems.

The control device of the present invention provides a plurality of level converters for one temperature detector, and selects and controls these level converters from a central processing unit according to the temperature range, thereby improving the linearity of the temperature detector. In addition to increasing the resolution of the analog-to-digital converter, the measurement error is reduced, the noise resistance is improved, the control function is improved, and the cost is reduced.

An embodiment of the present invention will be described below with reference to FIG. 1st
The parts with the same numbers as in the figures indicate the same parts, and the explanation thereof will be omitted. 5a is a level converter for a high temperature region, and 5b is a level converter for a low temperature region, which are connected to the parallel trap temperature detector 1 and the analog/digital converter 3. Then, the signal from the temperature detector 1 is input to the level converters 5a and 5b, and is converted into an analog voltage by the level converter 5a or 5b selected according to the signal from the central processing unit 4, and is converted into an analog-digital conversion Wk3. Enter. The converted digital values are input into the central processing unit 4, which performs necessary calculations and controls cooling and heat source equipment (not shown here). In this case, if the level converter 5a is used for the low temperature region and the level converter 5b is used for the high temperature region, the output voltage of each level converter with respect to temperature becomes 0 as shown in FIG. ) from T2(”O), Tt('
C) O time Luher converter 5m) O output t-VL, (v)
,'I'2('c).

The output of the level converter 5b at this time is assumed to be VL2 (V). In addition, the temperature range of the high temperature region is changed from T2 ("O) to T3 (
)℃, the output voltage of the level converter 5& at Tz ('c) is v81 (V), and the output of the level converter 5& at T3 ('C) is vH2 (v), Tg - T
14゜”J-TF vLl +vl-1t s vu
+Vsz, and l vLl −V
ti l (+l V#I - VI41) is made to be the maximum rated input voltage range of the analog-to-digital converter. In this way, the temperature range measured by the level converter is divided into two, so the output resolution of the N-bit analog-to-digital converter is 2N/, -Tl+2'/T.
3-T! +2°2N/T, which is about twice as high as when using one level converter, improving linearity and reducing measurement errors. Furthermore, the output voltage per 1° C. of the level converter is doubled, and the noise margin against disturbance noise and voltage fluctuation is also increased, and noise resistance is also improved.

In the above example, two level converters are used to convert #51. However, the present invention is not limited to this, and any number of devices may be used. Furthermore, although the level converter is controlled by the central processing unit, it is also possible to input the output of the level converter in parallel to a multiplexer, or to use an analog-to-digital converter with a multiplexer.

According to the present invention, since the measurement temperature range is divided by a plurality of level converters, the resolution of the analog-to-digital converter is improved, and a low-order analog-to-digital converter can achieve the same performance as a high-order converter. It is possible and cost effective. Also

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a conventional control device, FIG. 2 is a diagram showing a control device of the present invention, and FIG. 3 is a diagram explaining the circuit operation of the present invention. 1...Temperature detector 2...Level converter 3...
7 fts digital converter 4...Central processing unit 5a...Level converter for low temperature region 5b...
Level converter for high temperature areas

Claims (1)

[Claims] A temperature detection element whose resistance value changes depending on the temperature, a level conversion circuit that converts this resistance value into an analog voltage, an analog/digital conversion circuit that converts the analog voltage into a digital value, and a calculation that takes in this digital value. In an air conditioner equipped with a central processing circuit that controls cooling and heat source equipment, the measured temperature range is divided into multiple ranges, a level converter is provided for each range, and the output voltage range of these level converters is analog. The input voltage should match the rated allowable input voltage range of the digital converter, and the central processing circuit should select each level conversion circuit according to the temperature range, input the output of the analog-to-digital conversion circuit, and calculate the temperature. Control device 0 for an air conditioner, characterized in that it is configured to control the operation of a source device.