JPH0970178A - Air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the overheat protective function of an active filter from operating when the temperature of the filter becomes higher than the temperature resulting from the heat generated by the filter itself by allowing the temperature of an air conditioner (outdoor) to rise as a whole in the same state as that where the outside air temperature is abnormally high. SOLUTION: An active filter 5 is provided between a bridge rectifier circuit 2 and a smoothing capacitor 3 so as to shape an input current to a sine wave having a phase which is nearly equal to that of an output voltage. The temperature of the filter 5 is detected by means of a thermistor 33 and the difference between the detected temperature and a reference temperature is found by means of an error amplifier 35. A reference output voltage VOref which becomes the target value of the output voltage VO of an air conditioner is corrected in accordance with the output value of the amplifier 35. The correction is performed so that the voltage VOref can become lower as the detected temperature becomes higher. Then a switching waveform generating section 40 controls the switching of a power transistor 9 so that the difference between the corrected reference output voltage VOref and the output voltage VO can become zero.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air conditioner having an inverter circuit that changes the frequency of a compressor of an outdoor unit so that an optimum capacity can be obtained according to a load.

[0002]

2. Description of the Related Art Conventionally, there is known an air conditioner which realizes a refrigeration cycle by sequentially operating a compressor, a condenser, a pressure reducer, an evaporator and the like. Air conditioners in recent years include an inverter circuit that supplies AC drive power to a compressor,
The output frequency of the inverter circuit is controlled according to the load. As a result, the optimum operating capacity of the air conditioner for the load is obtained, and the comfort of air conditioning and the energy saving effect are improved.

In a conventional air conditioner, a DC voltage is obtained by rectifying an AC output voltage of a commercial power source with a bridge rectifying circuit and smoothing it with a smoothing capacitor, and this DC voltage is converted into an AC voltage of an arbitrary frequency by an inverter circuit. It is converted to voltage and given to the compressor. In such an air conditioner, since a capacitor input type circuit is formed, the input current is
It flows only near the top of the rectified waveform of the input voltage.
For this reason, there has been a problem that the power factor of the power supply is reduced and the harmonic current is increased, so that not only the power loss is increased but also the power supply line is adversely affected by the harmonic current.

In view of such circumstances, IEC (Internati
Since 1996, the onal Electrotechnical Commission) has been regulating the harmonic current of the power supply. Therefore, it is necessary to take some measures against such regulations.

As a technique for suppressing the harmonic current, an air conditioner equipped with an active filter has been proposed in Japanese Patent Laid-Open Nos. 4-26374 and 5-68376. The active filter is equipped with a switching element that switches the rectified voltage on and off.By appropriately turning the switching element on and off according to the input current waveform, the charging current waveform of the smoothing capacitor can be approximated to the input current waveform. Has become. This active filter reduces the harmonic components of the power supply current,
And the power factor can be increased.

Next, an example of a conventional air conditioner having an active filter will be described.

In this air conditioner, as shown in FIG. 10, the output of the AC commercial power source 71 is full-wave rectified by the bridge rectifier circuit 72, and the voltage passed through the active filter 73 is smoothed by the smoothing capacitor 74. It becomes a DC voltage. This DC voltage is converted into an AC voltage having an arbitrary frequency by the power module (inverter circuit) 75, and is given to the compressor 76 that serves as a load.

The active filter 73 includes a choke coil 77, a high speed recovery diode 78 and a power transistor 79.
The amount of input current to the smoothing capacitor 74 is controlled by switching 9 of FIG. The power transistor 79 is on / off controlled by the switching waveform generated by the switching waveform generator 80. The switching waveform generator 80 generates the switching waveform based on the input current waveform and the input voltage waveform to the active filter 73.

The power transistor 79 operates so as to bring the waveform of the charging current of the smoothing capacitor 74 closer to the input current waveform by the above switching waveform. This reduces the harmonic components of the power supply current and improves the power factor.

Further, in the above air conditioner, the operation is performed so that the input current waveform approaches the input voltage waveform, so that the output voltage V _O from the active filter 73 is the commercial power supply 71.
Is controlled to be higher than the effective value voltage of. Therefore, the switching waveform generation unit 80 feedback-controls the output voltage V _O so that the boosted value of the output voltage V _O from the effective value voltage is always constant. More specifically, the difference between the output voltage V _O obtained by the error amplifier 81 and the reference voltage from the reference power supply 82 is obtained, and the switching waveform generator 80 determines the switching waveform based on the difference.

Further, the above air conditioner has a circuit overheat protection function. This overheat protection function is provided by the active filter 73 detected by the thermistor 83 and the resistor 84.
It operates based on the temperature of. An error in the detected temperature with respect to the reference temperature based on the reference voltage from the reference power supply 85 is output by the error amplifier 86, and the temperature rise detection value output unit 87 detects the temperature rise value based on the error. Then, the step-up stop signal generator 88 causes the active filter 73 to change the power transistor 79 according to the temperature rise value.
When it is determined that the temperature has risen above a predetermined value, the switching waveform generator 80 stops outputting the switching waveform.

As a result, the power transistor 79 is stopped, and heat is generated due to the loss of the power transistor 79, the fast recovery diode 78, etc.
Is prevented from overheating abnormally.

The above-mentioned air conditioner also has an overvoltage protection function and an overcurrent protection function. The overvoltage protection function causes the switching waveform generation unit 80 to stop the output of the switching waveform when the overvoltage detection unit 89 detects that the output voltage from the active filter 73 is an overvoltage. Overcurrent protection function
When the overcurrent detection unit 90 detects that the input current to the active filter 73 is an overcurrent, the switching waveform generation unit 80 stops the output of the switching waveform.

In the above air conditioner, the inverter control waveform is output from the operating frequency setting circuit 91 to the power module 75 according to the operating conditions during operation.
Then, the power module 75 chops the output voltage from the active filter 73 based on the waveform, and applies the drive voltage of the operating frequency set to the compressor 76.

In the power module 75, heat is generated due to the loss of each switching element, and the amount of generated heat is detected as a voltage drop of the thermistor 92. In particular,
The amount of heat generation (temperature) is input to the error amplifier 94 as a voltage divided by the thermistor 92 and the resistor 93.
In the error amplifier 94, the reference voltage (output of the reference power supply 95)
The error of the above voltage with respect to is calculated, and the error is output to the operation stop signal generator 96. When the operation stop signal generation unit 96 detects that the temperature is abnormally rising based on the above error amount, it gives an operation stop instruction to the operation frequency setting circuit 91.

As a result, when the power module 75 has an abnormal temperature, the operating frequency setting circuit 91 stops the chopping operation of the power module 75. In this way, each switching element in the power module 75 is protected from being destroyed by overheating.

[0017]

As described above, the conventional air conditioner is provided with the overheat protection function for protecting each part of the active filter 73 from overheating. However, since the outdoor unit of the air conditioner is installed outdoors, the temperature may be abnormally high due to direct sunlight when the temperature is high in summer. In this case, the temperature detected by the thermistor 83 becomes higher than the temperature due to self-heating of the active filter 73. Therefore, the boost stop signal generation unit 88 may stop the active filter 73 even when the self-heating of the active filter 73 is not excessive.

Further, the above air conditioner is provided with an overheat protection function for protecting each part of the power module 75 from overheating. However, when the outdoor unit becomes abnormally hot as described above, the thermistor The temperature detected by 92 becomes higher than the temperature due to self-heating of the power module 75. Therefore, the operation stop signal generation unit 96 may stop the power module 75 even when the self-heating of the power module 75 is not excessive.

In the above air conditioner, since the output of the commercial power source 71 is unstable, when the input voltage to the active filter 73 is low, the boosted value of the active filter 73 is the operation of the air conditioner. It becomes unstable to changes in load. Therefore, the voltage applied to the compressor 76 fluctuates and it becomes difficult to maintain a normal operating state.

In the above air conditioner, the voltage applied to the compressor 76 is controlled by the power module 75 based on the operating conditions during operation. However, since the value of the voltage output from the active filter 73 is constant regardless of the operating condition, a voltage higher than that required for the operating condition may be applied to the compressor 76. In such a case, there is a problem that extra power loss occurs during the chopping operation of the power module 75, resulting in an increase in power consumption.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an air conditioner capable of maintaining a good operating condition even when the temperature is abnormal or the voltage is unstable and rises. Has an aim.

[0022]

In order to solve the above problems, an air conditioner according to claim 1 of the present invention has a rectifying means for rectifying an AC voltage output from an AC power source and a rectified AC. Smoothing means for smoothing the voltage so as to be a direct current voltage, reverse converting means for converting the direct current voltage from the smoothing means to an alternating voltage having a variable voltage and frequency and applying the same to the compressor, Is provided between the smoothing means and the smoothing means, and the amount of current flowing into the smoothing means is adjusted by switching of the switching element, thereby shaping the input current into a waveform having substantially the same phase as the input voltage and a substantially sine wave. An active filter, temperature detecting means for detecting the temperature of the switching element, and the switch so that the output voltage of the active filter becomes a target value. A switching control means for controlling the switching of the switching element and stopping the switching element when the temperature of the switching element is equal to or higher than a predetermined value, and the target value is corrected according to the temperature detected by the temperature detecting means. And a correction means for performing the correction.

In the air conditioner according to the first aspect, when the temperature detecting means detects the temperature of the switching element, the correcting means corrects the target value according to the temperature. For example, when the temperature of the switching element rises, the target value is corrected in accordance with the temperature rise. As a result, the output voltage of the active filter is lowered and the amount of current flowing through the switching element is reduced. As a result, self-heating of the switching element is suppressed, and the temperature detected by the temperature detecting means is lowered.

Therefore, the temperature of the switching element is
Even when the outside air temperature becomes higher than the temperature due to self-heating of the switching element due to abnormally high temperature, the frequency at which the switching element is stopped by the switching control means can be significantly reduced.

An air conditioner according to a second aspect of the present invention is the air conditioner of the first aspect, further comprising maximum frequency defining means for defining a maximum value of the frequency according to the output voltage of the active filter. There is.

Therefore, when the output voltage of the active filter decreases due to the decrease of the target value as described above, the maximum frequency defining means sets the maximum value of the frequency accordingly. For example, when the output voltage of the active filter decreases, the maximum frequency value is corrected in accordance with the decrease. As a result, the maximum drive capacity of the compressor by the inverse conversion means, that is, the maximum operation capacity of the air conditioner is reduced, so that even if the output voltage of the active filter is reduced, the compressor can be driven with the ability according to it. .

In order to solve the above-mentioned problems, an air conditioner according to a third aspect of the present invention rectifies the AC voltage output from the AC power supply and the rectified AC voltage into a DC voltage. A smoothing means for smoothing the DC voltage from the smoothing means, an inverse conversion means for converting the DC voltage from the smoothing means into an AC voltage having a variable voltage and frequency, and applying the AC voltage to the compressor; the rectifying means and the smoothing means. And an active filter for shaping the input current into a waveform having substantially the same phase as the input voltage and a substantially sine wave by adjusting the amount of current flowing into the smoothing means by switching the switching element, and the alternating current A frequency setting means for defining the maximum value of the frequency according to the voltage or the output voltage of the active filter. That.

In the air conditioner according to the third aspect, the frequency setting means sets the maximum value of the frequency in the inverse conversion means according to the AC voltage or the output voltage of the active filter. When the AC voltage is low, the output voltage of the active filter tends to be low. Especially, when the operating load of the air conditioner is heavy, the tendency becomes remarkable.

Therefore, when the AC voltage or the output voltage of the active filter is lowered, the frequency is set so as to be lowered accordingly, so that the driving capability of the compressor by the inverse conversion means is lowered, so that the load fluctuation occurs. Even if the output voltage of the active filter is insufficient (insufficient boosting), the operation of the compressor does not become unstable.

In order to solve the above-mentioned problems, an air conditioner according to a fourth aspect of the present invention rectifies the AC voltage output from the AC power supply and rectifies the AC voltage into a DC voltage. The smoothing means for smoothing the DC voltage from the smoothing means, the inverse conversion means for converting the DC voltage from the smoothing means into an AC voltage having a variable voltage and frequency and applying the voltage to the compressor, and the temperature of the inverse conversion means. Temperature detecting means, and the frequency is set according to the driving capacity required to drive the compressor, and the inverse conversion means is operated when the temperature detected by the temperature detecting means is equal to or higher than a predetermined value. The power control means for stopping and the maximum frequency defining means for defining the maximum value of the frequency set by the power controlling means according to the temperature detected by the temperature detecting means are provided. It is characterized in that.

In the air conditioner according to the fourth aspect, the inverse conversion means chops the DC voltage based on the frequency set by the frequency setting means, and drives the compressor with the voltage. On the other hand, when the temperature detecting means detects the temperature of the inverse converting means, the maximum frequency defining means defines the maximum value of the frequency according to the temperature. That is, the frequency is limited according to the temperature of the inverse conversion means.

For example, if the temperature of the inverse conversion means rises,
When the maximum value is set so as to lower the frequency accordingly, the maximum drive capacity of the compressor by the inverse conversion means, that is, the maximum operation capacity of the air conditioner is reduced, so the heat generation of the inverse conversion means is reduced. Therefore, the temperature of the inverse transformation means
Even if the outside air temperature becomes higher than the temperature due to self-heating of the inverse conversion means due to abnormally high temperature, the frequency with which the inverse conversion means is stopped by the power control means can be significantly reduced.

In order to solve the above-mentioned problems, the air conditioner according to a fifth aspect of the present invention rectifies the AC voltage output from the AC power supply and the rectified AC voltage into a DC voltage. A smoothing means for smoothing the DC voltage from the smoothing means, an inverse conversion means for converting the DC voltage from the smoothing means into an AC voltage having a variable voltage and frequency, and applying the AC voltage to the compressor; the rectifying means and the smoothing means. And an active filter that adjusts the amount of current flowing into the smoothing means by switching of a switching element to shape the input current into a waveform that has substantially the same phase as the input voltage and is approximately a sine wave. Switching control means for controlling switching of the switching element so that the output voltage of the filter becomes a target value, and the inverse conversion A temperature detecting means for detecting a temperature of the stage, according to the detected temperature is characterized by comprising a correction means for correcting the target value by the temperature detecting means.

In the air conditioner according to the fifth aspect, when the temperature of the inverse conversion means is detected by the temperature detection means, the correction means corrects the target value according to the temperature.
For example, when the temperature of the inverse conversion means rises, the target value is corrected in accordance with the rise in temperature. As a result, the output voltage of the active filter becomes high and the current flowing through the inverse conversion means can be reduced. Therefore, the self-heating of the switching element is suppressed, and the temperature detected by the temperature detecting means is lowered.

Therefore, even if the temperature of the inverse conversion means becomes higher than the temperature due to self-heating of the inverse conversion means due to abnormally high outside air temperature, the frequency of stopping the inverse conversion means by the power control means is greatly increased. Can be lowered.

In order to solve the above-mentioned problems, an air conditioner according to a sixth aspect of the present invention rectifies the AC voltage output from the AC power supply and rectifies the AC voltage into a DC voltage. Smoothing means for smoothing as described above, inverse conversion means for converting the voltage and frequency to variable AC voltage by chopping the DC voltage from the smoothing means and applying it to the compressor, and necessary for driving the compressor. The power control means for setting the frequency in accordance with the driving capability, the rectifying means and the smoothing means, and adjusting the amount of current flowing into the smoothing means by switching of the switching element An active filter that shapes the current into a waveform that has almost the same phase as the input voltage and is almost a sine wave, and the output voltage of the active filter becomes the target value. And switching control means for controlling the urchin switching of the switching element, and according to the frequency set by the power control means is characterized by comprising a correction means for correcting the target value.

In the air conditioner according to the sixth aspect, the correction means corrects the target value in accordance with the frequency set by the power control means. As a result, the output voltage of the active filter is controlled according to the driving capacity of the compressor (operating capacity of the air conditioner) by the inverse conversion means. Therefore, the output voltage of the active filter does not become higher than required by the inverse conversion means, and the loss in the chopping operation of the inverse conversion means can be reduced.

[0038]

BEST MODE FOR CARRYING OUT THE INVENTION

[Embodiment 1] The following description will discuss Embodiment 1 of the present invention with reference to FIGS. 1 and 2.

Air conditioner (outdoor unit) according to the present embodiment
As shown in FIG. 1, includes a bridge rectifier circuit 2, a smoothing capacitor 3, a power module 4, and an active filter 5 as a power supply system. Further, the air conditioner includes an inverter control unit and an active filter control unit as a control system.

The power supply system is configured to generate a DC voltage by rectifying the AC voltage from the commercial power supply 1 by the bridge rectifying circuit 2 and smoothing it by the smoothing capacitor 3. Further, the power supply system is configured to generate a three-phase AC voltage in the power module 4 based on the DC voltage and apply the AC voltage to the compressor 6.

Power module 4 as inverse conversion means
Includes six transistors 11 to 16 and six diodes 21 to 26. Transistors 11 and 12,
Transistors 13 and 14 and transistors 15 and 16
Are each connected in series between two power supply lines. On the other hand, the diodes 21 to 26 are connected to the transistor 11
~ 16 are individually connected in parallel. The power module 4 as the inverse conversion means outputs three-phase AC voltage by switching the transistors 11 to 16 based on an inverter control waveform from an operating frequency setting circuit 42 described later.

The compressor 6 is connected to the respective connection points of the transistors 11 and 12, the transistors 13 and 14 and the transistors 15 and 16. This compressor 6
It is driven by a three-phase AC voltage from the power module 4.

Further, in the power supply system, the active filter 5 is provided between the bridge rectifying circuit 2 as the rectifying means and the smoothing capacitor 3 as the smoothing means.
The active filter 5 includes a choke coil 7 and a high speed recovery diode (hereinafter referred to as a high speed diode).
8 and a power transistor 9. In this embodiment, an insulated gate bipolar transistor is used as the power transistor 9, but another high speed switching element may be used.

Choke coil 7 and high speed diode 8
Are provided in series with one of the power supply lines on the rectification side. Power transistor 9 as a switching element
Has a collector connected to a connection point between one end of the choke coil 7 and an anode of the high speed diode 8, and an emitter connected to the other (ground side) of the rectification side power supply line.

The active filter 5 controls the amount of current flowing through the choke coil 7 by switching the power transistor 9 with respect to the current flowing into the smoothing capacitor 3 via the choke coil 7 and the high speed diode 8. ing.

The inverter control unit includes the maximum frequency setting unit 3
1 and an operating frequency setting circuit 32.

The maximum frequency setting section 31 as the maximum frequency defining means sets the maximum operating frequency of the air conditioner in accordance with the magnitude of the output voltage V _O of the active filter 5. The operating frequency setting circuit 32 as the power control means controls the switching frequency and the inverter voltage (input voltage to the compressor 6) in the power module 4 based on the above-mentioned maximum operating frequency so as not to rise above a predetermined value. (Inverter waveform) is output. This limits the operating capacity of the compressor 6.

The active filter control section includes a thermistor 33, a resistor 34, an error amplifier 35, a reference power supply 36, an output voltage setting section 37, a reference power supply 38, an error amplifier 39, and a switching waveform generating section. 40 and 40.

The thermistor 33 as the temperature detecting means is
It is provided close to the active filter 5 and particularly detects heat generation due to loss of the high speed diode 8 and the power transistor 9. The thermistor 33 is connected in series with the resistor 34 and has one end grounded. The other end of the resistor 34 is connected to a power supply that outputs a DC voltage. Thermistor 33 and resistor 3
The circuit formed by 4 and 4 detects the temperature of the active filter 5 by outputting the above-mentioned DC voltage divided by the thermistor 33 and the resistor 34 whose resistance value changes according to the temperature as a detection voltage. It is like this.

The connection point between the thermistor 33 and the resistor 34 is
It is connected to one input terminal of the error amplifier 35. Further, the other input terminal of the error amplifier 35 is connected to the reference power source 3
6 is connected. The reference power supply 36 is adapted to generate a reference voltage V _ref1 which determines a reference temperature. The error amplifier 35 outputs the error of the detection voltage with respect to the reference voltage V _{ref1 as} an error voltage.

The output voltage setting section 37 as the correction means is
Based on the error voltage from the error amplifier 35, the reference power source 38
_{Is adapted} to correct the reference output voltage V _Oref . Specifically, when the error voltage is large, that is, when the difference between the detected temperature and the reference temperature is large, the output voltage setting unit 37 _lowers the reference output voltage V _Oref as the target value according to the temperature difference. Correct to. The error amplifier 39 outputs the error of the output voltage V _O with respect to the reference output voltage V _Oref corrected by the output voltage setting unit 37 as an error voltage.

The switching waveform generator 40 as switching control means controls the switching waveform given to the control electrode of the power transistor 9 based on the error voltage from the output voltage setting unit 37, that is, the pulse width of the pulse-shaped switching control signal. It is like this. As a result, the output voltage of the active filter 5 is controlled. Further, the switching waveform generator 40 is adapted to generate a switching control signal so that the input current waveform approaches the input voltage waveform based on the waveform of the input current and the waveform of the input voltage to the active filter 5. .

In the air conditioner configured as described above, when the temperature of the active filter 5 rises due to the heat generated by the loss of the high speed diode 8 and the power transistor 9, the resistance value of the thermistor 33 decreases. For this reason, the detection voltage input to the error amplifier 35 decreases, and the error in the detection voltage with respect to the reference voltage V _ref1 increases, and the error voltage output from the error amplifier 35 increases.

In the output voltage setting section 37, the reference output voltage V
_Oref is corrected so as to decrease according to the increased error voltage. Specifically, the reference output voltage V _Oref is as shown in FIG.
As shown in, the error voltage (temperature difference) is constant up to the standard value. On the other hand, when the temperature difference exceeds its standard value, the reference output voltage V _Oref is corrected in an inversely proportional relationship that decreases as the temperature difference increases, as shown by the solid line in the figure, or in the figure. As shown by the broken line, it is corrected so as to gradually decrease.

Then, since the error of the output voltage V _O with respect to the corrected reference output voltage V _Oref becomes large, the error voltage from the error amplifier 39 becomes large. Then, the switching waveform generator 40 generates a switching waveform that eliminates the above error.

As a result, the switching voltage and the number of times of switching of the power transistor 9 are reduced, the switching operation of the power transistor 9 is limited, and the current flowing through the high speed diode 8 is reduced. As a result, the amount of heat generated by the high speed diode 8 and the power transistor 9 is reduced, and the output voltage V _O is reduced.

When the self-heating of the active filter 5 becomes excessive, if the detected temperature rises above a predetermined value, the switching waveform generator 40 generates a switching waveform so as to stop switching of the power transistor 9. To do. As a result, it is possible to prevent abnormal operation or destruction of the high speed diode 8 and the power transistor 9 due to an abnormal temperature rise.

On the other hand, in the power module 4, the maximum frequency setting section 31 and the operating frequency setting circuit 32 limit the driving capability of the compressor 6 based on the output voltage V _O.
Therefore, even if the output voltage V _O drops as described above,
The operation of the compressor 6 can be normally maintained without the inverter voltage becoming insufficient.

As described above, in the present air conditioner, the switching of the power transistor 9 is controlled so as to decrease the output voltage V _O of the active filter 5 according to the temperature rise of the active filter 5. Therefore, heat generation of the high speed diode 8 and the power transistor 9 can be suppressed. Therefore, even if the temperature of the air conditioner becomes abnormally high due to an increase in the outside air temperature, it is possible to suppress an abnormal increase in the temperature detected by the thermistor 33. As a result, the frequency of unnecessarily stopping the air conditioner can be significantly reduced.

[Second Embodiment] The second embodiment of the present invention is described below with reference to FIGS. 3 and 4. In the present embodiment, the first
Constituent elements having the same functions as the constituent elements in the embodiment are given the same reference numerals, and the description thereof will be omitted.

The air conditioner according to the present embodiment, as shown in FIG. 3, has a bridge rectifier circuit 2, a smoothing capacitor 3,
A power supply system including the power module 4 and the active filter 5, an inverter control unit, and an active filter control unit are provided.

The inverter control unit includes the input voltage detection circuit 4
1, a maximum frequency setting unit 42, and an operating frequency setting circuit 3
And 2.

The input voltage detection circuit 41 outputs the average value of the input voltage V _in to the active filter 5. The maximum frequency setting unit 42 determines the maximum operating frequency of the air conditioner according to the magnitude of the output voltage V _O of the active filter 5. In addition, the maximum frequency setting unit 42 determines the maximum operating frequency to be a low value when at least one of the output voltage V _O and the average value is lower than the standard value. The use of the average value of the input voltage V _in to determine the maximum operating frequency is based on the fact that the input voltage V _in is a major factor in determining the output voltage V _O.

The active filter control section uses the reference power source 3
8, the error amplifier 39, and the switching waveform generator 40
And The error amplifier 39 outputs the error of the output voltage V _O with respect to the reference voltage from the reference power supply 38 as an error voltage.

[0065] In the configured the air conditioner as described above, the input voltage V _in is the input voltage detection circuit 4 to the output voltage, that the active filter 5 from the bridge rectifier circuit 2
When input to 1, the input voltage detection circuit 41 outputs the average value of the input voltage V _in . The maximum frequency setting unit 42 sets the maximum operating frequency based on the output voltage V _O.

At this time, if the output voltage V _O is lower than the standard value, the maximum operating frequency is set low. Further, even when the average value is lower than the standard value, the maximum operating frequency is set low. Specifically, as shown in FIG. 4, the maximum operating frequency is set to a constant value within a range in which the output voltage V _O (detection voltage) or the average value (detection voltage) is equal to or higher than the standard value. On the other hand, in the range where the detected voltage is lower than each standard value, the maximum operating frequency is corrected by a proportional relationship which becomes lower as the detected voltage decreases as shown by the solid line in the figure, or As shown by the broken line, it is corrected so as to gradually decrease.

Then, the operating frequency setting circuit 32 sets the actual operating frequency in a region lower than the input maximum operating frequency. As a result, the power module 4
Even if the input voltage V _in is low, it drives the compressor 6 within the range and the maximum operating frequency of the acceptable load variations. Therefore, stably regardless of fluctuations in the input voltage V _in can be maintained operation.

[Third Embodiment] The third embodiment of the present invention will be described below with reference to FIGS. 5 and 6. In the present embodiment, the first
Constituent elements having the same functions as the constituent elements in the embodiment are given the same reference numerals, and the description thereof will be omitted.

The air conditioner according to the present embodiment, as shown in FIG. 5, has a bridge rectifier circuit 2, a smoothing capacitor 3,
A power supply system including the power module 4 and the active filter 5, an inverter control unit, and an active filter control unit are provided.

The inverter control section includes a thermistor 51,
It has a resistor 52, an error amplifier 53, a reference power supply 54, a maximum frequency setting section 55, and an operating frequency setting circuit 32. Moreover, the active filter control unit is configured similarly to the active filter control unit in the second embodiment.

The thermistor 51 as the temperature detecting means is
It is provided close to the power module 4, and in particular,
The heat generation due to the switching loss in the power module 4 is detected. This thermistor 51
Is connected in series with the resistor 52 and has one end grounded. The other end of the resistor 52 is connected to a power supply that outputs a DC voltage.

The circuit formed by the thermistor 51 and the resistor 52 outputs the above-mentioned DC voltage divided by the thermistor 51 and the resistor 52, whose resistance value changes according to the temperature, as the detected temperature. The temperature of the module 4 is detected.

The connection point between the thermistor 51 and the resistor 52 is
It is connected to one input terminal of the error amplifier 53. In addition, the other input terminal of the error amplifier 53 is connected to the reference power source 5
4 are connected. The error amplifier 53 has a reference power source 54.
The error of the above-mentioned detected voltage with respect to the reference voltage V _ref2 (voltage that determines the reference temperature) is output as an error voltage.

The maximum frequency setting section 55 as the maximum frequency defining means determines the maximum operating frequency of the air conditioner according to the magnitude of the error voltage from the error amplifier 53. Specifically, when the error voltage is large, that is, when the difference between the detected temperature and the reference temperature is large, the maximum frequency setting unit 55 determines that the maximum operating frequency becomes a low value according to the temperature difference.

In the air conditioner constructed as described above, when the temperature of the power module 4 rises due to heat generation due to switching loss in the power module 4, the resistance value of the thermistor 51 decreases. For this reason, the detection voltage input to the error amplifier 53 decreases, and the error in the detection voltage with respect to the reference voltage V _ref2 increases, and the error voltage output from the error amplifier 53 increases.

In the maximum frequency setting section 55, the maximum operating frequency is set so as to decrease according to the increased error voltage. Specifically, the maximum operating frequency is constant when the error voltage (temperature difference) is below the standard value, as shown in FIG. On the other hand, when the temperature difference exceeds its standard value, the maximum operating frequency is corrected by an inversely proportional relationship that decreases as the temperature difference increases, as shown by the solid line in the figure, or by the broken line in the figure. As shown, it is corrected so as to gradually decrease. Then, the operating frequency setting circuit 32 generates an inverter waveform according to the maximum operating frequency that has become a low value.

As a result, the operating capacity of the power module 4 is suppressed, and the amount of heat generated by the switching loss of the power module 4 can be reduced. Therefore, even if the temperature of the air conditioner becomes abnormally high due to an increase in the outside air temperature, it is possible to suppress the abnormal temperature rise of the active filter 5.

Further, in the present air conditioner, when the self-heating of the power module 4 becomes excessive, if the detected temperature rises above a predetermined value, the operating frequency setting circuit 32 switches the elements of the power module 4. The inverter waveform is generated so as to stop. As a result, it is possible to prevent abnormal operation or destruction of each element due to an abnormal temperature rise.

Therefore, by suppressing the abnormal temperature rise of the active filter 5 as described above, the frequency of unnecessarily stopping the air conditioner can be greatly reduced.

Next, another air conditioner according to this embodiment will be described.

As shown in FIG. 7, this air conditioner has an inverter control section having an operating frequency setting circuit 32 and an active filter control section having the following configuration.

The active filter control section includes a thermistor 51, a resistor 52, an error amplifier 53, and a reference power supply 54.
The output voltage setting unit 37, the reference power supply 38, the error amplifier 39, and the switching waveform generation unit 40.

The output voltage setting unit 37 corrects the reference output voltage V _Oref from the reference power supply 38 based on the error voltage from the error amplifier 53. Specifically, when the error voltage is large, that is, when the difference between the detected temperature and the reference temperature is large, the output voltage setting unit 37 increases the reference output voltage V _Oref within a predetermined range according to the temperature difference. To correct. This is because when the temperature difference becomes abnormally large _unless the correction range of the reference output voltage V _Oref is limited.
Since the reference output voltage V _Oref becomes too high, the output voltage setting unit 3
This is because there is a disadvantage that the breakdown voltage of the circuit element in the latter stage of 7 is exceeded.

In the air conditioner constructed as described above, the difference between the temperature of the power module 4 detected by the thermistor 51 and the reference temperature (reference voltage V _ref2 ) is the same as in the air conditioner described above. Desired.

In the output voltage setting unit 37, when the difference becomes large, the reference output voltage V _Oref is corrected so as to become high accordingly. Specifically, the reference output voltage V _Oref is
As shown in FIG. 8, the error voltage (temperature difference) is constant below the standard value. On the other hand, when the temperature difference exceeds the standard value, the reference output voltage V _Oref is corrected by a proportional relationship which increases as the temperature difference increases as shown by the solid line in the figure, or in the figure. As shown by the broken line, it is corrected so as to rise in stages. In any case, the correction is performed within the range in which the reference output voltage V _Oref does not exceed the upper limit value.

Then, the switching waveform generator 40 outputs the reference output voltage V _Oref output from the error amplifier 39.
Based on the error of the output voltage V _O with respect to, a switching waveform that eliminates the error is output.

As a result, the switching voltage of the power transistor 9 and the number of times of switching increase, and the output voltage V _O of the active filter 5 increases. As a result, the voltage applied to the power module 4 increases, so that the current flowing through the power module 4 decreases. Therefore, the amount of heat generated by the switching loss of the power module 4 can be reduced. Therefore, also with the above configuration, when the air conditioner becomes abnormally high in temperature, it is possible to suppress an abnormal temperature rise of the power module 4, and to significantly reduce the frequency of unnecessarily stopping the air conditioner. Can be made.

[Fourth Embodiment] The fourth embodiment of the present invention will be described below with reference to FIG. In the present embodiment, constituent elements having the same functions as those of the constituent elements in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

The air conditioner according to this embodiment, as shown in FIG. 9, has a bridge rectifier circuit 2, a smoothing capacitor 3,
The power supply system includes the power module 4 and the active filter 5, the inverter control unit including the operating frequency setting circuit 32, and the active filter control unit.

The active filter control section has an output voltage setting section 61, a reference power supply 38, an error amplifier 39, and a switching waveform generating section 40. The output voltage setting unit 61 as a correction unit sets the reference output voltage V _Oref from the reference power source 38 according to the operating frequency information from the operating frequency setting circuit 32.

In the air conditioner constructed as described above, the output voltage setting unit 61 outputs the reference output voltage V _Oref corresponding to the above operating frequency information. Then
A switching waveform is output from the switching waveform generator 40 based on the error voltage from the error amplifier 39.
As a result, the output voltage V _O of the active filter 5 is controlled to be equal to the reference output voltage V _Oref .

As described above, according to the present air conditioner, the output voltage V _O is controlled according to the operating frequency, so that the applied voltage suitable for the power module 4, that is, the minimum required voltage for the operating capacity can be obtained. You can Therefore, the switching loss in the power module 4 can be minimized.

[0093]

As described above, in the air conditioner according to the first aspect of the present invention, the rectifying means for rectifying the AC voltage output from the AC power supply and the rectified AC voltage become the DC voltage. Between the smoothing means for smoothing, the inverse conversion means for converting the DC voltage from the smoothing means into an AC voltage having a variable voltage and frequency and applying the voltage to the compressor, the rectifying means and the smoothing means. And an active filter for shaping the input current into a waveform having substantially the same phase as the input voltage and a substantially sine wave by adjusting the amount of current flowing into the smoothing means by switching of the switching element, and the switching element The temperature detection means for detecting the temperature and the switching of the switching element are controlled so that the output voltage of the active filter becomes a target value. In addition, a switching control means for stopping the switching element when the temperature of the switching element is equal to or higher than a predetermined value, and a correction means for correcting the target value according to the temperature detected by the temperature detecting means. It has a structure.

As a result, the temperature of the switching element is detected, and the target value is corrected according to the temperature. For example, if the target value is corrected to decrease as the temperature of the switching element increases, The amount of current flowing through the switching element is reduced. Therefore, the self-heating of the switching element is suppressed and the temperature detected by the temperature detecting means is lowered. Therefore, even if the temperature of the switching element becomes higher than the temperature due to self-heating of the switching element due to abnormally high outside air temperature, the switching control means can significantly reduce the frequency of stopping the switching element. Therefore, there is an effect that the continuous operation of the air conditioner can be maintained even when the outside air has an abnormally high temperature as described above.

An air conditioner according to claim 2 of the present invention is the air conditioner of the first aspect, further comprising maximum frequency defining means for defining a maximum value of the frequency according to the output voltage of the active filter. It has a structure.

As a result, when the output voltage of the active filter decreases due to the decrease in the target value as described above, the maximum value of the frequency is set accordingly.
For example, the correction is performed so that the maximum value of the frequency becomes lower as the output voltage of the active filter decreases. Therefore, since the maximum drive capacity of the compressor by the inverse conversion means, that is, the maximum operation capacity of the air conditioner is reduced, even if the output voltage of the active filter is reduced, the compressor can be driven with the ability according to it. . Therefore, the air conditioner can be stably operated regardless of the change in the output voltage of the active filter.

An air conditioner according to claim 3 of the present invention comprises a rectifying means for rectifying the AC voltage output from the AC power supply,
Smoothing means for smoothing the rectified AC voltage so as to become a DC voltage, and inverse conversion means for converting the DC voltage from the smoothing means into an AC voltage having a variable voltage and frequency and applying it to the compressor. Is provided between the rectifying means and the smoothing means, and the amount of current flowing into the smoothing means is adjusted by switching the switching element, so that the input current has substantially the same phase as the input voltage and has a substantially sine wave. The configuration is provided with an active filter that shapes the waveform, and frequency setting means that defines the maximum value of the frequency according to the AC voltage and the output voltage of the active filter.

As a result, the maximum value of the frequency in the inverse conversion means is set in accordance with the AC voltage and the output voltage of the active filter, so that the frequency becomes lower as the AC voltage and the output voltage decrease, for example. The setting reduces the driving capability of the compressor by the inverse conversion means. Therefore, even if load fluctuation occurs, the operation of the compressor does not become unstable due to insufficient output voltage of the active filter. Therefore, there is an effect that the air conditioner can be stably operated even when the AC voltage is often unstable and low.

An air conditioner according to claim 4 of the present invention comprises a rectifying means for rectifying the AC voltage output from the AC power supply,
Smoothing means for smoothing the rectified AC voltage so as to become a DC voltage, and inverse conversion means for converting the DC voltage from the smoothing means into an AC voltage having a variable voltage and frequency and applying it to the compressor. A temperature detection means for detecting the temperature of the inverse conversion means, and the frequency is set according to the drive capacity required to drive the compressor, and the temperature detected by the temperature detection means is a predetermined value. Power control means for stopping the inverse conversion means when the above is the case, and maximum frequency defining means for defining the maximum value of the frequency set by the power control means according to the temperature detected by the temperature detecting means It is a configuration provided with.

As a result, when the temperature of the inverse conversion means is detected, the maximum value of the frequency is set in accordance with the temperature, so that the maximum frequency is decreased so that the temperature decreases in the inverse conversion means, for example. When the value is set, the maximum drive capacity of the compressor by the inverse conversion means, that is, the maximum operation capacity of the air conditioner decreases. Therefore, even if the heat generation of the inverse conversion means is reduced and the temperature of the inverse conversion means becomes higher than the temperature due to self-heating of the inverse conversion means due to abnormally high outside air temperature, the power control means causes the inverse conversion means. The frequency of stopping can be greatly reduced. Therefore, there is an effect that the continuous operation of the air conditioner can be maintained even when the outside air has an abnormally high temperature as described above.

An air conditioner according to claim 5 of the present invention comprises a rectifying means for rectifying the AC voltage output from the AC power supply,
Smoothing means for smoothing the rectified AC voltage so as to become a DC voltage, and inverse conversion means for converting the DC voltage from the smoothing means into an AC voltage having a variable voltage and frequency and applying it to the compressor. Is provided between the rectifying means and the smoothing means, and the amount of current flowing into the smoothing means is adjusted by switching the switching element, so that the input current has substantially the same phase as the input voltage and has a substantially sine wave. An active filter shaped into a waveform, switching control means for controlling the switching of the switching element so that the output voltage of the active filter becomes a target value, temperature detection means for detecting the temperature of the inverse conversion means, and this temperature With a configuration including a correction unit that corrects the target value according to the temperature detected by the detection unit. That.

As a result, when the temperature of the inverse conversion means is detected, the target value is corrected in accordance with the temperature. Therefore, for example, the correction is performed so that the target value becomes higher as the temperature of the inverse conversion means rises. When this is done, the output voltage of the active filter becomes high and the current flowing through the inverse conversion means becomes small. Therefore, the self-heating of the switching element is suppressed, and the temperature detected by the temperature detecting means is lowered. Therefore, also in this air conditioner, when the temperature of the inverse conversion means becomes higher than the temperature due to self-heating of the inverse conversion means, the frequency of stopping the inverse conversion means can be significantly reduced. Therefore, there is an effect that the continuous operation of the air conditioner can be maintained even when the outside air has an abnormally high temperature.

An air conditioner according to claim 6 of the present invention comprises a rectifying means for rectifying the AC voltage output from the AC power supply,
Smoothing means for smoothing the rectified AC voltage into a DC voltage, and inverse conversion means for converting the DC voltage from the smoothing means into an AC voltage having a variable voltage and frequency and applying it to the compressor. And a power control means for setting the frequency according to the driving capacity required for driving the compressor, and a smoothing means provided between the rectifying means and the smoothing means and switching the switching element. By adjusting the amount of current flowing in,
An active filter that shapes the input current into a waveform that has substantially the same phase as the input voltage and is substantially a sine wave, and switching control means that controls the switching of the switching element so that the output voltage of the active filter becomes a target value, And a correction unit that corrects the target value according to the frequency set by the power control unit.

As a result, the target value is corrected according to the set frequency, so that the output voltage of the active filter is controlled according to the driving capacity of the compressor by the inverse conversion means (operating capacity of the air conditioner). . Therefore, the output voltage of the active filter does not become higher than required by the inverse conversion means, and the loss in the chopping operation of the inverse conversion means can be reduced. Therefore, it is possible to reduce unnecessary power consumption and operate the air conditioner with high efficiency.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of an air conditioner according to a first embodiment of the present invention.

FIG. 2 is a graph showing correction of a reference output voltage based on a temperature difference between a temperature of an active filter and a reference temperature in the air conditioner of FIG.

FIG. 3 is a circuit diagram showing a configuration of an air conditioner according to a second embodiment of the present invention.

FIG. 4 is a graph showing correction of a maximum operating frequency based on a detected voltage in the air conditioner of FIG.

FIG. 5 is a circuit diagram showing a configuration of an air conditioner according to a third embodiment of the present invention.

6 is a graph showing correction of a maximum operating frequency based on a temperature difference between a temperature of an inverter module and a reference temperature in the air conditioner of FIG.

FIG. 7 is a circuit diagram showing a configuration of another air conditioner according to a third embodiment of the present invention.

8 is a graph showing the correction of the reference output voltage based on the temperature difference between the temperature of the inverter module and the reference temperature in the air conditioner of FIG. 7.

FIG. 9 is a circuit diagram showing a configuration of an air conditioner according to a fourth embodiment of the present invention.

FIG. 10 is a circuit diagram showing a configuration of a conventional air conditioner.

[Explanation of symbols]

1 Commercial power supply (AC power supply) 2 Bridge rectification circuit (rectification means) 3 Smoothing capacitor (smoothing means) 4 Power module (inverse conversion means) 5 Active filter 6 Compressor 9 Power transistor (switching element) 31 ・ 42 ・ 55 Maximum frequency Setting unit (maximum frequency regulating unit) 32 Operating frequency setting circuit (power control unit) 33.51 Thermistor (temperature detection unit) 37.61 Output voltage setting unit (correction unit) 40 Switching waveform generation unit (switching control unit) 41 Input Voltage detection circuit

Claims (6)

[Claims] 1. A rectifying unit for rectifying an AC voltage output from an AC power source, a smoothing unit for smoothing the rectified AC voltage to a DC voltage, and a DC voltage from the smoothing unit being chopped. The amount of current flowing into the smoothing unit is adjusted by switching the switching element, which is provided between the rectifying unit and the smoothing unit, and the inverse conversion unit that converts the voltage and frequency into an alternating voltage and applies it to the compressor. By doing so, an active filter that shapes the input current into a waveform that has almost the same phase as the input voltage and is almost a sine wave, temperature detection means that detects the temperature of the switching element, and the output voltage of the active filter that is the target value. The switching of the switching element is controlled so that And switching control means for stopping the switching element when it is more, the air conditioner characterized by comprising a correction means for correcting the target value according to the temperature detected by said temperature detecting means. 2. The air conditioner according to claim 1, further comprising maximum frequency defining means for defining a maximum value of the frequency according to an output voltage of the active filter. 3. A rectifying means for rectifying the AC voltage output from the AC power source, a smoothing means for smoothing the rectified AC voltage to a DC voltage, and a DC voltage from the smoothing means for chopping. The amount of current flowing into the smoothing means is adjusted by switching the switching element provided between the rectifying means and the smoothing means, and the inverse conversion means for converting the voltage and frequency into a variable AC voltage and applying it to the compressor. By doing so, an active filter that shapes the input current into a waveform that is approximately in phase with the input voltage and is approximately a sine wave, and the maximum value that defines the maximum value of the frequency according to the AC voltage or the output voltage of the active filter. An air conditioner comprising a frequency regulating means. 4. A rectifying means for rectifying the AC voltage output from the AC power supply, a smoothing means for smoothing the rectified AC voltage to a DC voltage, and a DC voltage from the smoothing means for chopping. Inverse conversion means for converting the voltage and frequency into a variable AC voltage and applying it to the compressor, temperature detection means for detecting the temperature of the inverse conversion means, and drive capacity required for driving the compressor And the frequency is set according to the temperature detected by the temperature detection means, and the power control means for stopping the inverse conversion means when the temperature detected by the temperature detection means is equal to or higher than a predetermined value. An air conditioner comprising: a maximum frequency defining unit that defines a maximum value of the frequency set by the power control unit. 5. A rectifying means for rectifying the AC voltage output from the AC power source, a smoothing means for smoothing the rectified AC voltage to a DC voltage, and a DC voltage from the smoothing means for chopping. The amount of current flowing into the smoothing means is adjusted by switching the switching element provided between the rectifying means and the smoothing means, and the inverse conversion means for converting the voltage and frequency into a variable AC voltage and applying it to the compressor. By doing so, an active filter that shapes the input current into a waveform that has approximately the same phase as the input voltage and is approximately a sine wave, and a switching that controls the switching of the switching element so that the output voltage of the active filter becomes the target value. The control means, the temperature detecting means for detecting the temperature of the inverse conversion means, and the temperature detecting means for detecting the temperature. An air conditioner characterized by comprising a correction means for correcting the target value in accordance with the temperature. 6. A rectifying means for rectifying an AC voltage output from an AC power source, a smoothing means for smoothing the rectified AC voltage to a DC voltage, and a DC voltage from the smoothing means for chopping. Inverse conversion means for converting the voltage and frequency into a variable AC voltage and applying it to the compressor, power control means for setting the frequency according to the driving capacity required for driving the compressor, and the rectifying means. Is provided between the smoothing means and the smoothing means to adjust the amount of current flowing into the smoothing means by switching of the switching element, thereby shaping the input current into a waveform substantially in phase with the input voltage and substantially sinusoidal. A filter and a switch that controls switching of the switching element so that the output voltage of the active filter becomes a target value. And control means, the air conditioner is characterized in that according to the frequency set by the power control means and a correction means for correcting the target value.