JPH089685A - Control apparatus of air conditioner - Google Patents

Abstract

PURPOSE:To prevent malfunction of overcurrent protection by a method wherein the detection signal of an input signal for an air conditioner is input to an A/D port for a microcomputer and an A/D-converted value is corrected by the A/D-converted value of a constant voltage which is input from another A/D port. CONSTITUTION:An input current for an inverter device 2 which inverter controls a compressor motor 3 is detected by an input current detection circuit 4, and it is input to an A/D port for a microcomputer 5. The microcomputer 5 controls the inverter device 2 in such a way that the input current does not exceed a permissible value. However, when an irregularity (+ or -10%) exists in a power- supply voltage for the microcmputer 5, an A/D reference voltage which is used to judge an overcurrent is changed, and the overcurrent cannot be protected precisely. In order to prevent the malfunction of the protection of the overcurrent, a constant voltage (2 V) is input to another A/D port for the microcomputer 5 from a constant-voltage source 6, and the A/D-converted value of the input current is corrected by the A/D-converted value of the constant voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an air conditioner that performs variable capacity control.

[0002]

2. Description of the Related Art In an air conditioner that performs variable capacity control, the input current is detected, and when the detected value exceeds a permissible value, a microcomputer controls an inverter device to lower the operating frequency of a compressor motor, The input current is kept below the allowable value. FIG. 3 shows an example of the control device, which includes an input current detection circuit 24 and an inverter device.
22 and a microcomputer 25 that controls the inverter device 22. The inverter device 22 includes a converter unit 26 including a rectifier circuit that converts an AC input voltage obtained from the AC power supply 21 into a predetermined DC voltage, a smoothing capacitor 27 that smoothes an output voltage of the converter unit 26, and a smoothed DC The input current detection circuit is composed of an inverter unit 28 that converts the voltage into an AC voltage and supplies it to the compressor motor 23.
24 is a current detector (current transformer CT) 29 and a resistor 3
0, 31, a diode 32, a capacitor 33, and a variable resistor 34, and the output voltage is input to the A / D port of the microcomputer 25 via the resistor 35.
The microcomputer 25 is input to the A / D port and
The / D converted value is compared with the allowable value stored in the storage unit, and the operating frequency of the compressor motor is determined based on the comparison result.

[0003]

By the way, a power supply voltage of, for example, DC 5V is applied to the microcomputer 25 for controlling the inverter device 22 separately from the voltage from the input current detection circuit 24 input to the A / D port. However, the power supply voltage of the microcomputer 25 drops by, for example, 10%.
It works even if it becomes 5V. Thus, if the power supply voltage decreases, the A / D reference voltage also decreases. However, since the input current detection circuit 24 is an independent circuit that is not directly related to the power supply voltage of the microcomputer 25, the input current detection circuit 24 outputs A / A
Before the input current reaches the allowable value, the voltage input to the D port does not change depending on the power supply voltage of the microcomputer 25 and only the A / D reference voltage based on the power supply voltage of the microcomputer 25 decreases. The overcurrent protection function of the microcomputer 25 will operate. Therefore, conventionally, a variable resistor is required for each assembled controller.
Although the adjustment of 34 has been made to cope with the change (variation) of the power supply voltage of the microcomputer 25, there is a problem that it takes time to adjust the variable resistor 34. Therefore, it is an object of the present invention to provide an air conditioner control device that solves the above problems.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and the output of an input current detection circuit is input to an A / D port of a microcomputer,
Comparing the value converted by the A / D conversion unit with the allowable value of the input current stored in the storage unit, and controlling the inverter device of the compressor motor so that the input current does not exceed the allowable value. In, a constant voltage is applied to another A / D port provided in the microcomputer, and the A / D converted value of the input voltage input from the input current detection circuit is converted into the A / D converted value of the identification voltage. I tried to correct it.

[0005]

With the control device configured as described above, the constant voltage A input from the constant voltage source to the predetermined A / D port is irrespective of the variation in the power supply voltage of the microcomputer.
Since the A / D converted value of the output voltage of the input current detection circuit can be corrected by the / D converted value, an accurate input current protection operation can be performed even if the power supply voltage of the microcomputer varies.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows an outline of a control device for an air conditioner. 1 is an AC power supply, 2 is an inverter device, 3 is a compressor motor controlled by an inverter, 4 is an input current detection circuit, and 5 is an inverter device 2. A microcomputer 6 for controlling is a constant voltage source capable of extracting a constant voltage of 2V.
The inverter device 2 includes a converter unit 7 including a rectifier circuit that converts an AC input voltage obtained from the AC power source 1 into a predetermined DC voltage, a smoothing capacitor 8 that smoothes an output voltage of the converter unit 7, and a smoothed DC. The input current detection circuit 4 includes a current detector (current transformer CT) 10, resistors 11, 12, and 13, a diode 14, and a capacitor. 15 and the output voltage is input to the A / D port of the microcomputer 5 via the resistor 16. In addition to the A / D port that takes in the output voltage of the input current detection circuit 4, the microcomputer 5 has a plurality of A
There is a / D port, and a constant voltage of 2 V from the constant voltage source 6 is input to one of them via a resistor 17. Although not shown, the microcomputer 5 includes an A / D conversion unit, a signal generation unit that generates a PWM signal necessary for inverter control, a timer circuit unit, a comparison circuit unit, a storage unit, and the like. When the input current detected by the input current detection circuit 4 exceeds the permissible value, the operating frequency of the compressor motor 3 is lowered to keep the input current below the permissible value.

By the way, A / of the microcomputer 5
When the D precision is 8 bits, the A / D converted value is 255, and this value is from -5 to 5 for example when the power supply voltage (microcomputer voltage) of the microcomputer 5 is 5V, as shown in FIGS. % Even if it changes to 4.5 V, the microcomputer 5 which is designed to perform overcurrent protection operation when the output voltage of the input current detection circuit 4 is 3 V has an A / D ratio when the microcomputer voltage is 5 V. Conversion value is 1
It becomes 54, and the judgment to apply the overcurrent protection operation is made with this value, but if the microcomputer voltage is 4.5 V, the A / D conversion value becomes 171 and the above 1
In the case where the overcurrent protection operation is executed at 54, the overcurrent protection operation is executed when the output voltage of the input current detection circuit 4 is 2.7V instead of 3V. Therefore, in this embodiment, as a means for eliminating such a problem, a constant voltage of 2V obtained from the constant voltage source 6 as shown in FIG. 1 is used, the A / D converted value of 2V is read, and the program software is used. The overcurrent protection operation value is 2: A / D2 = 3: A / D3 (A / D2 is 2V A
/ D converted value) A / D3 = 3/2 x A / D2 is obtained, and the air conditioner is protected from overcurrent based on the value of A / D3. In this way, even if the microcomputer voltage changes from 5V to 4.5V (even if it varies).
The overcurrent protection operation can be executed when the output voltage of the input current detection circuit 4 becomes 3V.

[0008]

According to the air conditioner equipped with the control device as described above, the input current is always detected accurately and the quality is stable regardless of the variation in the power supply voltage of the microcomputer. The conventional variable resistor for adjusting the output of the input current detection circuit can be replaced with a general resistor, eliminating the need for the output adjustment of the input current detection circuit, which was required for each product. improves.

[Brief description of drawings]

FIG. 1 is a circuit block diagram of a control device for an air conditioner showing an embodiment of the present invention.

FIG. 2 is a diagram showing a difference in A / D conversion value caused by a variation in power supply voltage of a microcomputer according to the present invention and a conventional example.

FIG. 3 is a circuit block diagram of a control device for an air conditioner showing a conventional example.

[Explanation of symbols]

 1 AC power supply 2 Inverter device 3 Compressor motor 4 Input current detection means 5 Microcomputer 6 Constant voltage source

Claims (1)

[Claims] 1. An output of an input current detection circuit is input to an A / D port of a microcomputer, a value converted by an A / D conversion unit is compared with an allowable value of an input current stored in a storage unit, and input. In a configuration in which an inverter device of a compressor motor is controlled so that a current does not exceed a permissible value, a constant voltage is applied to another A / D port provided in the microcomputer so that the identification voltage A A of the input voltage input from the input current detection circuit by the / D conversion value
A control device for an air conditioner, characterized in that a / D conversion value is corrected.