JPH06113548A - Inverter - Google Patents

Abstract

PURPOSE:To enhance efficiency of motor or the like while allowing low noise driving by providing means for switching the connection of a rectifying/ smoothing circuit between voltage doubler rectifier connection and both wave rectifier connection. CONSTITUTION:The inverter comprises a rectifying/smoothing circuit constituted of a rectifying diode 13 and a smoothing capacitor 15 and when a triac 14 is normally turned ON, the rectifying circuit functions as a voltage doubler rectifier to produce an output voltage of about 280V. When the triac 14 is normally turned OFF, the rectifying circuit functions as a normal both wave rectifying circuit to produce an output voltage of about 140V. When the circuit is conducted at a specific phase position of AC voltage, an output voltage between 140V and 280V is produced depending on the peak value. Since the output voltage has possibility of fluctuation, an output voltage detecting resistor 16 and an output voltage detecting circuit 21 detect fluctuation of the output voltage and control the conduction phase such that an optimal voltage is obtained. This constitution enhances motor efficiency and allows low noise driving by suppressing high frequency components in the motor current.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter device for driving a load such as a motor in an air conditioner or the like.

[0002]

2. Description of the Related Art FIG. 5 shows an example of the configuration of a conventional inverter device used in an air conditioner. In the figure, 1 is a line filter, 2 is a reactor for improving the power factor,
3 is a rectifying diode, 4 is a smoothing capacitor, and the rectifying diode 3 and the smoothing capacitor 4 constitute a rectifying / smoothing circuit. Reference numeral 5 is a transistor module including six switching elements, 6 is an AC compressor motor, an induction motor, and 7 is a microcomputer or the like, which is an air conditioner controller including a waveform synthesizing circuit. In the operation of the inverter device, the reactor 2, the diode 3, and the smoothing capacitor 4 rectify and smooth AC 100V AC power from the commercial power source to obtain a DC voltage. In this case, since the DC output voltage is subjected to the voltage doubler rectification, about 280 V can be obtained without load. This DC voltage is supplied to the transistor module 5, and AC power is supplied to the compressor motor 6 by chopping with an AC PWM signal of several KHz to several tens KHz. The AC PWM signal for controlling the on / off of the transistor module 5 is generated by the microcomputer 7.

In the above-mentioned inverter device for an air conditioner, it is possible to change the operating frequency and energization time.
The apparent voltage is changed by changing the energization time. That is, the power control is performed by increasing the energization time when the compressor motor 6 is rotating at high speed and shortening the energization time when rotating at low speed. Therefore, at medium to low speeds, the energization time becomes short and the voltage utilization ratio becomes poor. In addition, the operating frequency is set to a high frequency during high-speed rotation and a low frequency during low-speed rotation according to the voltage.

By the way, a DC method using a synchronous motor as a compressor motor has been used in recent years. The DC method using a synchronous motor is different in that a feedback circuit for the number of rotations is added and that it is not necessary to artificially generate AC power by a PWM signal.
It is similar to the C method. That is, power control is performed by increasing the energization time during high speed rotation and shortening the energization time during low speed rotation.

On the other hand, conventionally, the transistor module 5
There is also a method in which the direct current voltage applied to is varied and the energization time is not changed. These are methods using a commercial transformer or using a switching power supply, and the equipment is so large that they are hardly used in air conditioners.

[0006]

A speed control method for a compressor motor or the like in a conventional inverter device is a method for controlling an energization time. In the middle and low speed range, the energization time is shortened and the voltage utilization ratio is deteriorated. Along with this, there is a problem that the harmonic component of the current increases and noise is easily generated. There is also a system in which the DC voltage applied to the transistor module is varied and the energization time is not controlled, but the conventional system is disadvantageous in cost because the circuit becomes bulky. Furthermore, DC using a synchronous motor
In the method, the DC voltage is chopped to control the speed, but the energization time becomes short in the low speed range, and it becomes difficult to detect the position detection signal without a position detection sensor such as a compressor motor. Therefore, a filter may be used, but the response becomes slow and the controllability deteriorates.

The present invention has been made in view of the above problems, and it is possible to improve the efficiency of, for example, a motor as a load and to drive with low noise, and to detect the rotor position without a sensor. An object of the present invention is to provide an inverter device capable of improving the quality of induced voltage in a compressor motor or the like to improve the accuracy of position detection and improve controllability.

[0008]

In order to solve the above problems, the present invention provides a rectifying / smoothing circuit for converting an input AC power of a constant voltage into a DC power, and a DC power converted by the rectifying / smoothing circuit. In an inverter device having a transistor module for chopping and supplying required power to a load, and a drive means for driving the transistor module, the rectification / smoothing circuit is connected to a double voltage rectification circuit and a double-wave rectification circuit. The gist is to have a switch means for switching to the connection.

[0009]

In the above structure, when the AC input is a commercial power supply of 100 V, the voltage applied to the transistor module is 1
It is possible to change from 40V to 280V. Therefore, when the load is a motor, the duty ratio of the PWM signal is increased in the medium to low speed range to improve the motor efficiency, and the harmonic components of the electric power are reduced to enable low noise driving.
Especially when the DC motor is driven, it is not necessary to perform chopping, and the loss of the transistor module is reduced. When the load is a DC compressor motor, the induced voltage is detected in order to detect the position without a sensor. However, the quality of the induced voltage is improved, the position detection accuracy is improved, and the controllability is improved. Furthermore, by setting to the state of the double-wave rectification circuit at the time of starting, the AC input 200
It is possible to prevent damage to parts when V is applied erroneously.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a first embodiment of the present invention. The present embodiment is an example in which an induction motor in an air conditioner is controlled as a load. In the figure, 11 is a line filter, 12 is a reactor, 13 is a rectifying diode, and 14
Is a triac as semiconductor switching means, 15 is a smoothing capacitor, and the rectifying diode 13 and the smoothing capacitor 15 constitute a rectifying / smoothing circuit. 1
6 is an output voltage detection resistor, 17 is a transistor module consisting of 6 switching elements, 18 is an AC compressor motor and an induction motor, 19 is an AC zero cross detection circuit, 20 is a triac drive circuit, 21 is an output voltage detection circuit, and 22 is This is a controller of the entire air conditioner including a waveform synthesizing circuit as a driving means such as a microcomputer.

Next, the operation of the inverter device configured as described above will be described. Since the air conditioner using the inverter device operates with the optimum capacity according to the surrounding environment, the rotation speed of the compressor motor is changed. In this case, generally, the speed control is performed while keeping the ratio of the operating frequency and the operating voltage constant. The speed control method in this embodiment is performed as follows. The drive signal of the transistor module 17 from the controller 22 always sets the energization time to the maximum state. And the operating voltage is TRIAC 1
This is performed by changing the DC voltage applied to the transistor module 17 by limiting the energization time of No. 4 described above.
When the triac 14 is constantly turned on, the rectifier circuit becomes a voltage doubler rectifier circuit and the output voltage reaches close to 280V. Also, if the triac 14 is always off,
The rectifier circuit is always a double-wave rectifier circuit, and the output voltage is 140
It becomes about V. When the triac 14 is turned on at the position of a specific phase of the AC voltage, the output voltage becomes a value between 140V and 280V depending on the peak value of the AC voltage at that time. Since the output voltage may fluctuate due to load fluctuations and the like, the fluctuation of the output voltage is detected by the output voltage detection resistor 16 and the output voltage detection circuit 21, and the triac 14 is energized so as to have an optimum voltage. Control the phase. According to the first embodiment of the present invention, as compared with the conventional method, the conduction time is set to be longer in the medium and low speed rotation range, so that the PW is increased.
The duty ratio of the M signal is increased and the motor efficiency is improved. Further, the harmonic components of the motor current are reduced, and low noise driving becomes possible.

FIG. 2 shows a second embodiment of the present invention. This embodiment is an example in which a synchronous motor in an air conditioner is controlled as a load. 2 that are the same as or equivalent to the constituent elements in FIG. 1 are designated by the same reference numerals as those used above, and redundant description will be omitted. In FIG. 2, 23 is a DC compressor motor, a synchronous motor, and 24
Is a position detection circuit.

Next, the operation of the inverter device according to this embodiment will be described. In this embodiment, since the synchronous motor 23 is controlled, the position detection circuit 24 detects the rotor position, and the operating frequency of the drive signal of the transistor module 17 is controlled according to the position detection signal. The speed control is performed by changing the DC voltage applied to the transistor module 17 as in the first embodiment. Conventional D
The purpose of chopping in the C compressor motor control is to control the voltage, not to apply a pseudo AC voltage as in the case of the AC compressor motor. Therefore, if the DC voltage of the transistor module 17 can be changed, it is not necessary to perform chopping as in the conventional case. As a result, in the DC method, in addition to the effect of the AC method, the waveform generating circuit functioning as a driving unit in the controller 22 can be realized with a simple configuration, and the switching loss of the transistor module 17 is reduced. Further, the above-mentioned position detection signal is detected by the induced voltage of the applied voltage, but since the applied voltage is not chopped as in the prior art in this embodiment, the induced voltage becomes thin even in the middle and low speed ranges, making it difficult to detect. Since it is not necessary to perform shaping by using a filter in the position detection circuit 24, high speed control is possible.

FIG. 3 shows a third embodiment of the present invention. In the present embodiment, a relay is used as a mechanical switch means instead of the triac in the first and second embodiments. In FIG. 3, the same or equivalent components as those in FIGS. 1 and 2 are designated by the same reference numerals, and the duplicated description will be omitted. In FIG. 3, 25 is a relay as mechanical switch means, 26
Is a back electromotive voltage absorption diode, and 27 is a relay drive circuit.

Next, the operation of the inverter device according to this embodiment will be described with reference to FIG. In the medium to low speed range, the relay 25 is released, the rectifier circuit is connected to a double-wave rectifier circuit, and the applied voltage to the transistor module 17 is 140V.
And In this state, the energization time is controlled to control the operating voltage. When the load becomes heavy in the high speed rotation range, relay 2
5 is made conductive, the wiring of the rectifier circuit is made a double voltage rectifier circuit, and the applied voltage of the transistor module 17 is set to 280
V. In this state, the conduction time is controlled to control the operating voltage. In the present embodiment, the output voltage cannot be continuously varied as in the first and second embodiments, but the rectifier circuit can be switched to a double voltage rectifier circuit and a double wave rectifier circuit. In this case, the operation is not always performed with the energization time extended, but in the state of the double-wave rectification circuit, the energization time is almost double that of the conventional one. Therefore, as in the first embodiment and the like, the duty ratio of the PWM signal becomes high in the medium and low speed regions, the motor efficiency is improved, and low noise driving becomes possible.
FIG. 4 shows operation waveforms at this time together with a comparative example. The figure shows an example in which the operating voltage is limited to about half. The control from (a) to (b) in the same figure is the voltage control in the present embodiment, and the energization time is kept at T, and the configuration of the rectifier circuit is switched from the voltage doubler rectifier circuit to the double-wave rectifier circuit and the transistor Apply voltage E of module 17 to 1/2
As the power is limited. On the other hand, in the control from (c) to (d) in the same figure, the voltage E applied to the transistor module 17 is not changed by the conventional control method, and the energization time T is 1 /
The power is limited to 2.

Further, the effect of each of the above-described embodiments will be described. In the first to third embodiments, by setting the double-wave rectification state at the time of starting, the energizing time at the time of starting becomes twice as long as that in the conventional case, so that the controllability at the time of starting is improved. Further, even if the erroneous application of 200 V is performed, there is no possibility that a high voltage will be applied to the circuit, and it is possible to prevent the destruction of parts. Further, the additional components for producing these effects are only semiconductor switches or mechanical switches and a switch driving circuit, and can be realized at low cost.

[0018]

As described above, according to the present invention,
Since a switching means for switching the connection of the rectification / smoothing circuit for supplying the DC voltage to the transistor module between the connection of the voltage doubler rectification circuit and the connection of the double-wave rectification circuit is provided, an AC input of a commercial power supply of 100V is provided. If the voltage applied to the transistor module is 140 V
It becomes possible to vary up to 80V, and when the load is a motor, the duty ratio of the PWM signal becomes high in the medium and low speed range to improve the motor efficiency, and the harmonic components of the current are reduced, resulting in low noise. It can be driven.
In particular, when controlling the DC motor, chopping is not necessary and the loss of the transistor module can be reduced. Further, in the case of the DC compressor motor, the induced voltage is detected in order to detect the position without a sensor. However, the quality of the induced voltage is improved and the accuracy of the position detection can be improved and the controllability can be improved. Furthermore, when starting, rectification
By setting the smoothing circuit to the state of the double-wave rectification circuit,
It is possible to prevent damage to parts when an AC input of 200 V is erroneously applied.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of an inverter device according to the present invention.

FIG. 2 is a circuit diagram showing a second embodiment of the present invention.

FIG. 3 is a circuit diagram showing a third embodiment of the present invention.

FIG. 4 is a diagram showing an example of operation waveforms in the third embodiment together with a comparative example.

FIG. 5 is a circuit diagram showing a conventional inverter device.

[Explanation of symbols]

13 Rectifier Diode 14 Triac (Semiconductor Switch Means) 15 Smoothing Capacitor That Composes Rectifying / Smoothing Circuit with Rectifier Diode 17 Transistor Module 18 Induction Motor (Load) 22 Controller as Driving Means 23 Synchronous Motor (Load) 25 Relay (Mechanical) Switch means)

[Procedure amendment]

[Submission date] November 24, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

Claims (1)

[Claims] 1. A rectifying / smoothing circuit for converting input AC power having a constant voltage into DC power, and a transistor module for chopping the DC power converted by the rectifying / smoothing circuit to supply required power to a load. In an inverter device having a driving means for driving the transistor module, a switching means is provided for switching the connection of the rectification / smoothing circuit to the connection of the voltage doubler rectification circuit and the connection of the double-wave rectification circuit. Inverter device.