JPH10174449A - Dead time compensation for compressor of air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable supply of target voltage to a compressor by storing a voltage loss due to a dead time in a memory and then compensating for the voltage loss, when a power transistor is switched the next time. SOLUTION: A switching time of a power transistor is detected (S11) and thereby it is detected whether or not there is a voltage loss due to a dead time (S12). In the case that there is a voltage loss, a voltage loss value is stores in a memory (S13) and the value is used as a compensation value for the voltage loss, when the power transistor is switched the next time. In the case that there is no voltage loss, it is detected (S14) whether or not there is a voltage loss value stored in the memory. When there is no voltage loss value stored in the memory, the power transistor is switched which responds only for the dead time (S16). When there is a voltage loss value stored in the memory, it is detected whether or not there is the switching time which should be compensated for (S15). In the case that it is necessary to compensate for the switching time, the switching operation for the switching time is made, with respect corresponding to the stored voltage loss value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of driving a compressor of an air conditioner, and more particularly to a method of compensating for a dead time of an inverter corresponding to the operation of the compressor in an air conditioner employing a variable speed compressor. .

[0002]

2. Description of the Related Art Generally, forward conversion of alternating current to direct current (forward) is performed.
A device that performs DC / DC conversion is referred to as a converter, and a device that performs reverse conversion of DC to AC is referred to as an inverter.

[0003] A typical inverter air conditioner rectifies a constant AC voltage, converts it to DC, converts it to AC again, and changes the frequency or voltage based on the cooling load condition to the compressor. Apply. The compressor can change the cooling mode while the number of rotations changes according to a change in frequency or voltage, whereby it is possible to operate power saving cooling with low power consumption.

As described above, the frequency of the inverter air conditioner can be changed based on the load. Therefore, when increasing the room temperature during heating or decreasing the room temperature during cooling, the time required to reach the set temperature can be shortened. Yes, there is almost no stoppage of the compressor, so the change in indoor temperature can be precisely maintained in the minimum temperature range, and the frequency for driving the compressor changes from the lowest frequency to the maximum frequency, so the compressor starts. Since the current is lower than the operating current, other electric products are not affected when the compressor is started, and there is an advantage that power loss is smaller than that of a general air conditioner.

[0005] On the other hand, when the indoor temperature and the outdoor temperature exceed the set temperature band, the DC current of the inverter air conditioner rapidly increases while the compressor pressure increases, resulting in an overload condition or an increase in the total current. When the maximum DC peak value is reached, the operating frequency of the compressor is reduced or the compressor is stopped to protect the system, and the outdoor fan is driven for a predetermined time and then stopped.

FIG. 1 is a block diagram showing an inverter air conditioner including an indoor unit 10 and an outdoor unit 20.

The indoor unit 10 includes an indoor temperature sensor 11 for sensing the indoor temperature, an indoor fan motor 12 for blowing cold air heat exchanged by the indoor heat exchanger into the room, control of the indoor fan motor, temperature calculation, and The indoor microcomputer 13 having a timer function and the like and outputting a control signal for controlling a load based on a set program, and a set temperature and a set air volume through the remote control or the key operation panel to the indoor microcomputer 13. And a user operation unit 14 for inputting.

[0008] The outdoor unit 20 has an outdoor temperature sensor 21 for sensing the outdoor temperature, an outdoor fan motor 22 for cooling the outdoor heat exchanger to increase the efficiency of heat exchange, and a control signal from the indoor microcomputer 13. An outdoor microcomputer 23 for controlling an output frequency applied to an inverter 26; a transistor driving unit 24 for driving a compressor by a control signal of the outdoor microcomputer 23;
4, a converter 25 for converting an AC power supply to a DC power by driving the DC power supply, an inverter 26 for converting a DC power supply which has been forward-converted through the converter 25 to an AC power again to drive a compressor 27, and a voltage applied from the inverter 26. A compressor 27 forcibly compressing and circulating a refrigerant in a cooling cycle by an AC power supply, a DC peak voltage detecting unit 28 and an overcurrent detecting unit 29 for detecting a voltage and a current fluctuating based on an overload. It is composed of

In the inverter air conditioner thus constructed, the inverter 26 is connected to the outdoor microcomputer 2.
3 controls the operation of the compressor 27 by outputting a constant sine wave having a variable frequency based on a predetermined control signal applied via the transistor drive unit 24.

The inverter 26 includes two serially connected inverters.
DC power applied to the collector terminals of the two power transistors PT1a to PT6 is changed to PWM drive signals PWM1, P2.
WM2 alternately switches to generate a PWM drive power supply.

In such a conventional compressor driving apparatus, the DC power supply applied to the power transistor PT of the inverter 26 is switched by a mutually alternating PWM drive signal as shown in FIG. 3 to output a PWM DC drive power supply. Then
With this drive power supply, the compressor 27 compresses the refrigerant while rotating at a specific rotation speed.

Here, when the duty ratio of the PWM drive signal is variably changed, the drive power supply voltage applied to the compressor 27 is changed by a width corresponding to the duty ratio. Since the rotation speed of the compressor 27 changes, the circulation capacity of the refrigerant differs.

At this time, as shown in FIG. 3, PWM drive signals having different duty ratios are inputted to alternately switch the two series-connected power transistors, and based on the mutual PWM drive signals. The input is performed so as to have a certain time gap, that is, a dead time so that the turn-on time of the power transistor is not superimposed. Then the compressor 27
The power is smoothly transmitted to and operated. The dead time is usually determined to be about 16 μm.

According to the prior art, a fixed dead time is set between the PWM driving signals, and the dead time is divided into two cases.

First, when the PWM drive having the dead time is performed in a state where the operation of the compressor 27 is normal, only the DC power supplied to the inverter 26 during the dead time is used to drive the compressor 27. Instead of being consumed, it is simply passed to ground as a voltage loss.

Second, when the compressor 27 is in a load state in which an overload is applied, the two power transistors PT1a to PT6 of the inverter 26 for driving the compressor 27 are used.
Is overloaded, the temperature rises due to this, and a substantial dead time is lengthened, and the two power transistors PT1a to PT6 are simultaneously turned on to cause a shot phenomenon. Such a shot phenomenon is caused by the aforementioned 2
The power transistors PT1a to PT6 are destroyed and the inverter 10 is damaged.

Here, as shown in FIG. 3, a time delay of the off-time occurs due to the duty ratio, and this time delay is referred to as a so-called dead time. A delay time is always required for stable driving. The dead time is usually a specific delay time that meets the applicable condition, and t _stg
Although + t _off (dead time + delay time due to temperature) is specified, the temperature of the power transistor PT changes due to the overload of the compressor, and the corresponding dead time is also variable.

In the conventional air conditioner, a power transistor in an inverter for driving a compressor has a fixed dead time regardless of a normal state or a load state. Unnecessary voltage loss occurs, and in a load state, a shot phenomenon of the power transistor occurs due to a rise in temperature, so that the power transistor is destroyed.

[0019]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to store a voltage loss due to a dead time corresponding to driving of a compressor in a memory. An object of the present invention is to provide a compressor dead time compensation method in an air conditioner that can supply a target voltage to a compressor by compensating for a voltage value lost during the next switching of the power transistor.

Another object of the present invention is to detect the overload condition of the power transistor in response to the operation of the compressor in advance and change the dead time during operation of the air conditioner based on a normal state or a load state. It is an object of the present invention to provide a method for compensating for a dead time of a compressor in an air conditioner which can compensate for the dead time.

[0021]

According to the present invention, there is provided a method for compensating for a dead time of a compressor in an air conditioner according to the present invention. The method includes the steps of: providing an inverter provided with a PWM drive signal to output a drive voltage; A compressor provided with a drive voltage of the inverter and driven at a predetermined rotational speed, wherein a switching operation time of a power transistor in the inverter is detected to detect a voltage loss value due to a dead time. And, if a voltage loss value is detected in the step, storing the voltage loss value in a memory;
Reading a voltage loss value stored in the memory if the voltage loss value is not detected; adding a switching time corresponding to the voltage loss value read in the step to output a PWM signal to an inverter; Clearing a voltage loss value due to dead time stored in the memory.

The voltage loss value due to the dead time may be stored by adding a corresponding voltage loss value to a voltage loss value generated in a previous stage.

After the clearing step is performed, the method may further include a step of determining whether switching of the power transistor is completed.

Another aspect of the present invention is an air conditioner including an inverter provided with a PWM signal and outputting a drive voltage, and a compressor provided with the drive voltage of the inverter and driven at a predetermined rotation speed. In the method, the load condition of the compressor corresponding to an arbitrary operation in the air conditioner is differentially sensed, and the dead time of the compressor is varied in multiple stages so as to correspond to the differential load condition. And a step of varying the drive of the compressor by the variable drive signal having the multi-stage dead time.

[0025] The step of differentially sensing the load of the compressor may be characterized by sensing the temperature that changes based on the load applied to the power transistor in the inverter in a number of steps.

The step of varying the dead time of the compressor in multiple stages includes setting a specific reference dead time,
The dead time may be varied by adding or subtracting a predetermined time to the dead time so as to correspond to the sensed differential load.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of a method for compensating a dead time of a compressor in an air conditioner according to the present invention will be described in detail with reference to the accompanying drawings.

FIGS. 4 and 5 are flowcharts showing a method for compensating for a dead time of a compressor in an air conditioner according to the present invention.

First, referring to FIG. 4, in the present invention, an internal memory or an external memory is connected to the outdoor microcomputer 23 in order to store a voltage loss due to a dead time generated during the operation of the compressor 27. Next, the DC peak voltage converted from the sine wave output through the inverter 26 is compared with the PWM signal supplied to the power transistors PT1 to PT6 to determine the switching time for turning on / off the power transistors PT1a to PT6. Detect (S1
1). The switching time is detected to determine whether there is a voltage loss value due to the dead time stored in the memory (S12).

If there is a voltage loss value due to the dead time in the step (S12), the voltage loss value is stored in a memory (S13), and is converted into a voltage loss at the next switching of the power transistor. Use it as the corresponding compensation value. At this time, if a voltage loss value due to the dead time occurs even in the next operation, the corresponding voltage loss value is added to the voltage loss value generated in the previous stage and stored in the memory. On the other hand, if there is no voltage loss value due to the dead time, it is detected whether there is a previous stage voltage loss value stored in the memory (S14). At this time, if there is no stored voltage loss value, the corresponding power transistor is switched for the corresponding dead time (S16), and if there is the stored voltage loss value, it is stored in the memory at the corresponding switching time. It is detected whether there is a switching time for compensating the voltage loss value (S15). If there is no switching time, the step (S16) is repeated, and if there is a switching time, the switching operation of the power transistor for adjusting the switching time for the stored voltage loss value is performed (S17). After clearing the voltage loss value stored in the memory, the power transistor PT1
The above operations are repeated until the switching operations of a to PT6 are completed. Thereby, the switching loss value due to the dead time can be compensated.

FIG. 5 shows another embodiment of a method for compensating for a dead time of a compressor in an air conditioner according to the present invention.

Here, while the air conditioner is operating in a specific circulation cycle in an arbitrary operation mode, the compressor 27 of the air conditioner is caused due to the surrounding environment of the air conditioner or the unreasonable use of the user. May be overloaded, or overload may occur due to the surrounding environment due to the smooth operation of the compressor.

The outdoor microcomputer 23 of the outdoor unit 20 always reads the temperature sensed by the power transistors PT1a to PT6 of the inverter 26 for driving the compressor 27 (S21). Then the temperature read is T ₁ ° C. higher whether the primary to determine from (S22), if not higher than T ₁ ° C. and recognizes that the operation of the normal compressor 27, the temperature again is T ₀ It is determined whether the temperature is higher than ℃ (S2
3). If the read temperature is higher than T ₀ ° C, it is in a normal operation state, and the reference dead time is set as a drive signal necessary for driving the compressor 27 (S2).
5). At this time, the reference dead time is usually 16 μm.
Is set. If the read temperature is lower than T ₀ ° C,
This is an operation state of a load smaller than a normal load, and a dead time obtained by subtracting only a predetermined first time (t ₁ ) from the reference dead time is set as a drive signal necessary for driving the compressor 27 (S24). ).

However, if the read temperature is higher than T ₁ ° C, it is recognized that an arbitrary load is applied to the compressor 27, and T is re-determined to determine how much load is applied. Judge whether it is higher than ₂ ° C (S2
6). If the read temperature is not higher than T ₂ ° C, it is recognized that a slight load has occurred, and a dead time obtained by adding a predetermined first time (T ₁ ) to the reference dead time is used to drive the compressor 27. (S27). If the temperature is higher than T ₂ ° C, it is recognized that a high load has occurred, and a dead time obtained by adding only a predetermined secondary time (2t ₁ ) to the reference dead time is used for driving the compressor 27. It is set as a necessary drive signal (S28).

Here, the second time (2t ₁ ) has a longer time width than the first time (t ₁ ).

When the drive signal is determined in this way and the compressor 27 is operated, the first dead time is calculated from the reference dead time.
Time (t ₁₎ only is able to prevent voltage loss only the first hour of subtracting (t ₁₎ when the dead time obtained by subtracting the reference dead time in the first hour (t ₁₎ or the second time In the case of a dead time obtained by adding only (2t ₁ ), it is possible to prevent a shot phenomenon that is likely to occur in the inverter.

[0037]

As described above, the method of compensating for the dead time of a compressor in an air conditioner according to the present invention stores the voltage loss value due to the dead time in a memory and then loses the voltage loss at the next switching of the power transistor. By compensating the applied voltage, there is an effect that the performance of the air conditioner is improved and the efficiency of air conditioning is improved.

Further, according to the present invention, in order to improve the reliability of the power transistor of the inverter, the dead time corresponding to the temperature change of the transistor is varied, so that not only the voltage loss can be reduced in a normal driving state. As a result, the reliability of the system under load conditions can be guaranteed.

[Brief description of the drawings]

FIG. 1 is a block diagram schematically showing a configuration of a normal air conditioner.

FIG. 2 is a block diagram showing the inverter and the compressor of FIG. 1;

FIG. 3 is a diagram illustrating a dead time in a PWM waveform applied to the compressor of FIG. 2;

FIG. 4 is a flowchart illustrating a method for compensating a dead time of a compressor in an air conditioner according to the present invention.

FIG. 5 is a flowchart illustrating a dead time compensating process of the compressor according to the present invention.

[Explanation of symbols]

 Reference Signs List 10 indoor unit 11 indoor temperature sensor 12 indoor fan motor 13 indoor microcomputer 14 user operation unit 20 outdoor unit 21 outdoor temperature sensor 22 outdoor fan motor 23 outdoor microcomputer 24 power transistor drive unit 25 converter 26 inverter 27 compressor 28 DC peak voltage detection Unit 29 Overcurrent detection unit PT1 Power transistor PT2 Power transistor

Claims (6)

[Claims] 1. An air conditioner comprising: an inverter provided with a PWM drive signal to output a drive voltage; and a compressor provided with a drive voltage of the inverter and driven at a predetermined rotational speed. Detecting the voltage loss value due to the dead time by detecting the switching operation time of the power transistor, and storing the voltage loss value in the memory when the voltage loss value is detected in the step, and detecting the voltage loss value when the voltage loss value is not detected. Reading a voltage loss value stored in the memory, adding a switching time corresponding to the voltage loss value read in the step, and outputting a PWM signal to an inverter; and storing a dead time stored in the memory. Clearing the voltage loss value due to time. Machine dead time compensation method. 2. The voltage loss value due to the dead time is:
The method of claim 1, wherein the voltage loss value generated in the previous step is added to the voltage loss value and stored. 3. The method of claim 1, further comprising the step of determining whether switching of a power transistor is completed after performing the clearing step. . 4. A method for differentially sensing a load condition of a compressor corresponding to an arbitrary operation of the air conditioner, wherein a dead time of the compressor is varied so as to correspond to the differential load condition. A method of compensating for a dead time of a compressor in an air conditioner, the method comprising: varying the driving of the compressor by a variable drive signal having the multi-stage dead time. . 5. The method according to claim 4, wherein the step of differentially sensing the load of the compressor includes sensing the temperature that changes based on the load applied to the power transistor in the inverter in multiple steps. 4. The method for compensating for a dead time of a compressor in an air conditioner according to claim 1. 6. The step of varying the compressor dead time in multiple stages includes setting a specific reference dead time and adding or subtracting the reference dead time for a predetermined time, thereby detecting the detected differential time. 5. The method of claim 4, wherein the dead time is varied according to a load.