JPH089548A - Controller of air conditioner - Google Patents

Abstract

PURPOSE:To decide the overcurrent of the controller of an air conditioner and cut off the power feed to its compressor in case of the overcurrent. CONSTITUTION:In an converter device, an AC power supply voltage 1 is passed through a filter circuit 2, and the voltage 1 is converted into a predetermined DC voltage by a rectification circuit 3 and a smoothing circuit 4, and after the converting of the DC voltage into an AC voltage by an inverter circuit 5, the AC voltage is fed to a compressor 6. The AC input current of the inverter device is sensed by a current transformer 9 and an input current sensing circuit 10, and the DC input voltage of the inverter circuit 5 is sensed by a voltage dividing resistor 11 and a DC voltage sensing circuit 12. In a microcomputer 8, the upper limit values of the AC input current for various driving frequencies and the decision reference value in case of the DC input voltage reduction caused by an overcurrent are memorized. In case of the overcurrent, the control of the inverter device is stopped.

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, its input current is detected, and when the detected value exceeds a permissible value, a microcomputer switches the inverter circuit to lower the operating frequency of the compressor. The input current is kept below the allowable value. FIG. 3 shows an example of the control device, in which electric power from the AC power supply 21 is passed through a filter circuit 22 and then converted into a predetermined DC voltage by a rectifier circuit 23 and a smoothing circuit 24, and an AC voltage is converted by an inverter circuit 25. And is supplied to the compressor 26.
The inverter circuit 25 is composed of a plurality of switching elements, which are switching-controlled by a pulse signal from a drive circuit 28 controlled by a microcomputer 27. The input current is detected by the input current detecting means including the current transformer (CT) 29 and the input current detecting circuit 30, and the overcurrent generated due to the abnormality of the compressor 26 is detected by the resistor 31 and the overcurrent detecting circuit 32. Is detected by the overcurrent detection means, and these detection signals are input to the microcomputer 27, and when overcurrent is detected, the switching control of the inverter circuit 25 is stopped to shut off the power supply to the compressor 26. It has become. Reference numeral 33 shown in the figure is a discharge resistor.

[0003]

The current transformer 29 described above has no particular problem, but since the resistor 31 for detecting the overcurrent is provided in series with the power line on the input side of the inverter circuit 25, it does not generate heat. Is large. Since this heat generation adversely affects other components constituting the inverter device, it is necessary to take measures such as improving ventilation to prevent downsizing of the control device. Therefore, it is an object of the present invention to provide an air conditioner control device that solves the above problems.

[0004]

The present invention has been made to solve the above problems and includes an inverter circuit and
In the air conditioner comprising the control means and the input current detecting means, etc., and variably controlling the operating frequency of the compressor, an upper limit value of the input current is provided for each operating frequency of the compressor, When the input current exceeds the upper limit value, or when a DC voltage detecting means is provided on the input side of the inverter circuit and the DC voltage detected by the detecting means becomes a predetermined value or less, I decided to cut off the power supply.

[0005]

Since the operating frequency of the compressor and the output voltage of the inverter circuit are substantially proportional to each other, the output voltage is low and the input current is small when the operating frequency is low. if,
If the operating frequency is low but the input current is high, it can be seen that the load current is high due to some abnormality. Also, if the load (compressor motor) is short-circuited, the DC input voltage of the inverter circuit will drop, but with the above configuration, these phenomena can be detected and when the input current exceeds the upper limit value. Alternatively, the power supply to the compressor can be cut off when the DC input voltage of the inverter circuit drops below a predetermined value.

[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 source, 2 is a filter circuit, 3 is a rectifying circuit, 4 is a smoothing circuit, 5 is an inverter circuit having a plurality of switching elements, and 6 Is an inverter-controlled compressor, 7 is a drive circuit that drives an inverter circuit, 8 is a microcomputer that controls the drive circuit 7, 9 is a current transformer for detecting an input current, 10 is an input current detection circuit, and 11 is A voltage divider resistor for detecting the DC input voltage of the inverter circuit 5, and 12 is a DC voltage detection circuit. The power from the AC power supply 1 is passed through the filter circuit 2, converted into a predetermined DC voltage by the rectifier circuit 3 and the smoothing circuit 4, and supplied to the inverter circuit 5. Switching of the plurality of switching elements of the inverter circuit 5 is controlled by pulse signals from the drive circuit 7 controlled by the microcomputer 8.

The input current detected by the current transformer 9 is converted into a DC voltage by the input current detection circuit 10 and input to the A / D port of the microcomputer 8. On the other hand, the output from the voltage dividing resistor 11 is input to the other A / D port of the microcomputer 8 via the DC voltage detection circuit 12. The microcomputer 5 is not shown,
In addition to an A / D converter that digitally converts analog data from the input current detection circuit 10 and the DC voltage detection circuit 12, a signal generation unit that generates a PWM signal required for inverter control, a timer circuit unit, a comparison circuit unit, and a storage unit. And a storage unit for comparing and determining the upper limit value of the input current for each operating frequency of the compressor 6 and the decrease in the DC input voltage of the inverter circuit 5 due to the drastic increase of the load current (overcurrent). When the input current exceeds the upper limit value or the DC input voltage becomes a predetermined value (determination reference value) or less, the inverter control is stopped and the compressor 6 is stored. It is designed to cut off the power supply of.

FIG. 2 is a flow chart showing an outline of the control operation of the microcomputer 8. When the inverter control is started, the operating frequency is read in step ST1, and the upper limit value stored in the storage section is stored in step ST2. The upper limit value for the operating frequency read in step ST1 is read from the inside, and subsequently, in step ST3, the input current value detected by the current transformer 9 and the input current detection circuit 10 is read. At step ST4, the input current value read at step ST3 is changed to step S
It is determined whether or not it is larger than the upper limit value read at T2, and if the input current value is smaller than the upper limit value, step S
Returning to T1, the work of steps ST1 to ST4 is repeated. When it is determined that the input current value is larger than the upper limit value, it is determined that an overcurrent has occurred in the inverter device, the inverter control is stopped in step ST5, and the power supply to the compressor 6 is cut off.

[0009]

With the control device as described above, overcurrent can be detected on the input current detection circuit side using the current transformer and the DC voltage detection circuit side using the voltage dividing resistor. If a current is detected, the power supply to the load is immediately cut off, so it is safe, and since there is no need to connect a resistor in series with the load, there is no danger of heat generation and no adverse effects on other parts. Therefore, the overall size of the device can be reduced.

[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 flowchart showing an outline of a control operation according to the present invention.

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 Filter circuit 3 Rectifier circuit 4 Smoothing circuit 5 Inverter circuit 6 Compressor (compressor motor) 7 Drive circuit 8 Microcomputer 9 Current transformer 10 Input current detection circuit 11 Voltage dividing resistor 12 DC voltage detection circuit

Claims (4)

[Claims] 1. An air conditioner comprising an inverter circuit, control means therefor, input current detection means, etc., and variably controlling the operating frequency of a compressor, wherein an input for each operating frequency of the compressor is provided. An air conditioner control device, wherein an upper limit value of current is provided, and when the input current exceeds the upper limit value, power supply to the compressor is cut off. 2. An air conditioner comprising an inverter circuit, control means therefor, input current detection means, etc., and variably controlling the operating frequency of the compressor, wherein a DC voltage is applied to the input side of the inverter circuit. 2. The control device for an air conditioner, wherein the control means is provided, and when the DC voltage detected by the detection means becomes equal to or lower than a predetermined value, the power supply to the compressor is cut off. 3. An air conditioner comprising an inverter circuit, control means therefor, input current detection means, etc., and variably controlling the operating frequency of the compressor, and an input for each operating frequency of the compressor. An upper limit value of the current is provided, and when the input current exceeds the upper limit value, or a DC voltage detecting means is provided on the input side of the inverter circuit, and the DC voltage detected by the detecting means is below a predetermined value. The control device for an air conditioner, characterized in that the power supply to the compressor is shut off when the air conditioner is reached. 4. The control device for an air conditioner according to claim 1, wherein the power supply to the compressor is shut off by stopping the operation of the inverter circuit.