JPH05168248A - Air-conditioner - Google Patents

Abstract

PURPOSE:To enable life of a relay to be improved by turning on a relay for short-circuiting a resistance for suppressing an inrush current in starting charging when the charging current to a smoothing capacitor is detected and charging is nearly completed and then the charging current is fully reduced in a capacitor input type power-supply circuit. CONSTITUTION:When operation of an air-conditioner is initiated, a control device 9 generates a PWM waveform according to a desired number of revolutions of a compressor 7 and then inverter-controls the compressor 7 according to the PWM waveform. An input current of an inverter device 2 is detected by the input current sensor 7, an overcurrent protection function is operated in the case of overcurrent, and then an inverter part 5 is controlled so that the number of revolutions of the compressor 7 can be reduced. In a capacitor input type circuit configuration, power is supplied through a resistor 11 when power is turned on, a control device 9 judges that a smoothing capacitor 4 was fully charged according to detection input current from an input current conversion circuit 8, and then a drive circuit 13 is driven and a relay 12 is turned on, thus enabling the resistor 11 to be short-circuited.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to control of a power supply circuit of an air conditioner.

[0002]

2. Description of the Related Art In many air conditioners, as shown in FIG. 1, for example, a load of a compressor 6 or the like is controlled by an inverter. The inverter device 2 is a rectifier circuit for converting alternating current into direct current. The inverter circuit unit 5 includes a unit 3, a smoothing capacitor 4 that smoothes the rectified voltage, an inverter circuit unit 5 that converts the smoothed DC voltage into an AC voltage, and the inverter circuit unit 5 uses a PWM waveform generated by the microcomputer 9. It is designed to be controlled. By the way, in a so-called capacitor input type circuit configuration using the smoothing capacitor 4, a large charging current flows to the smoothing capacitor 4 side when the power is turned on, which may damage the rectifying element or the like of the rectifying circuit unit 3. Therefore, in order to prevent such an accident, a charging current to the smoothing capacitor 4 is supplied to the input side of the rectifier circuit unit 3 in parallel with a relay 12 driven and controlled by a microcomputer and a resistance element 11. The inrush current is suppressed by flowing the side. In addition, the compressor 6
The relay 12 is controlled to be turned on when power is supplied to a load such as. The timing for turning on the relay 12 has been set in the microcomputer 9 in advance so that a predetermined time has elapsed after the power of the microcomputer 9 was turned on or immediately before power is supplied to a load such as the compressor 6.

[0003]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
Even if the timing of turning on the switch 12 is set to be after a predetermined time has elapsed from the power-on of the microcomputer 9, the smoothing capacitor 4 and other parts to be used have different temperature characteristics and other variations, and therefore the smoothing capacitor 4 The charging time is not always constant, and is too long or too short depending on how the timing is taken, so it cannot be said that the control is appropriate. In particular, if the timing of turning on the relay 12 is too early, the contact of the relay 12 will be closed while the charging current is still large, which may adversely affect the contact. Therefore, it is an object of the present invention to provide an air conditioner that solves the above problems.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and includes a rectifying circuit section for converting an alternating current into a direct current, a smoothing capacitor for smoothing a rectified voltage, and a smoothed capacitor. An air conditioner including a current detecting means on the input side of an inverter device including an inverter circuit unit for converting DC to AC, and a contact side of a relay for drive control by a microcomputer and a resistance element in parallel. In the above, it is decided to control the relay to be turned on when the input current detected by the current detecting means becomes equal to or less than a preset value after the power is turned on.

[0005]

According to the above control method, the charging current to the smoothing capacitor can be detected by the input current detecting means provided on the input side of the inverter device, so that the charging to the smoothing capacitor is almost completed. The relay can be turned on after the charging current has dropped sufficiently.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a block diagram showing an outline of an inverter device of an air conditioner and its control system. Reference numeral 1 is an AC power source, 2 is a rectifier circuit unit 3 for converting AC to DC, and a smoothing capacitor 4 for smoothing a rectified voltage. And an inverter device including an inverter circuit unit 5 that converts the smoothed DC voltage into an AC voltage, 6 is a compressor that controls the inverter, 7 is an input current sensor that detects an input current of the inverter device 2, and 8 is an input current. An input current conversion circuit that digitally converts a detection signal from the sensor 7 to obtain a detection input current, 9 is a control device including a microcomputer, and 10 is a drive that drives and controls the inverter unit 5 based on a control signal from the control device 9. A circuit, 11 is a resistance element for suppressing the rising (rush current) of the charging current flowing in the smoothing capacitor 4 when the power is turned on,
Reference numeral 12 is a relay driven by the drive circuit 13. Although not shown in the drawings, a zero-cross detection circuit or the like for detecting the zero-cross of the input alternating current is provided on the input side of the rectifier circuit unit 3 for determining the input frequency and interrupting the control signal.

When the operation of the air conditioner is started, the control device 9 generates a PWM (pulse width modulation) waveform according to a desired rotation speed of the compressor 6, and the compressor 6 is inverter-controlled by this PWM waveform. .. At that time, the input current of the inverter device 2 is detected by the input current sensor 7, but if the input current becomes an overcurrent, the overcurrent protection function is activated to reduce the rotation speed of the compressor 6. It controls the section 5. By the way, in a so-called capacitor input type circuit configuration including the smoothing capacitor 4, a charging current first flows through the smoothing capacitor 4 when the power is turned on, and the rush current may damage the rectifying element of the rectifying circuit unit 3. The resistance element 11 is provided to suppress this inrush current. When the power is turned on, power is supplied from the resistance element 11 side, and the relay 12 is turned on when the smoothing capacitor 4 is sufficiently charged. In this embodiment, the timing of turning on the relay 12 is controlled by the method described below.

The control method will be described below with reference to FIG. In FIG. 2, (A) shows the input current waveform after the power is turned on until the smoothing capacitor 4 is charged. (B) shows changes in the input current detected by the input current sensor 7. (C) shows the timing when the relay 12 is turned on. In the program of the control device 9, the judgment reference value as shown by the broken line in (B) is set. This judgment reference value is a value which is considered to be the end of charging of the smoothing capacitor 4, and the microcomputer drives the drive circuit 13 when the detected input current from the input current conversion circuit 8 becomes less than the judgment reference value. It controls to turn on the relay 12.

[0009]

In the case of the air conditioner which performs the control as described above, the change in the charging current to the smoothing capacitor can be grasped by the input current detecting means, so that the relay can be operated after the charging current is sufficiently reduced. The air conditioner can be turned on, and the input current detecting means can be shared with the existing air conditioner and can be realized by only changing the program of the microcomputer. Therefore, the reliability of the air conditioner can be improved without any special cost. ..

[Brief description of drawings]

FIG. 1 is a block diagram showing an outline of an inverter device of an air conditioner and a control system thereof according to the present invention and a conventional example.

FIG. 2 is a time chart for explaining the control method of the present invention.

[Explanation of symbols]

 1 AC power supply 2 Inverter device 3 Rectifier circuit part 4 Smoothing capacitor 5 Inverter part 6 Compressor 7 Input current sensor 8 Input current conversion circuit 9 Control device (microcomputer) 10 Drive circuit 11 Resistance element 12 Relay 13 Drive circuit

Claims (1)

[Claims] 1. A current detection at an input side of an inverter device including a rectifier circuit unit for converting AC to DC, a smoothing capacitor for smoothing a rectified voltage, and an inverter circuit unit for converting smoothed DC to AC. With the provision of means, the contact side of the relay controlled by a microcomputer,
In an air conditioner including a resistance element in parallel, it is controlled so that the relay is turned on when the input current detected by the current detection means after the power is turned on becomes equal to or less than a preset value. A characteristic air conditioner.