JP3319523B2 - Control device and compressor for brushless motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a brushless motor in which each winding of a motor having a plurality of windings, such as a brushless DC motor, is sequentially energized at a commutation timing corresponding to a predetermined rotational position of a rotor. And a compressor .

[0002]

2. Description of the Related Art In recent years, in air conditioners and refrigerators, brushless motors, which are a type of DC motors, have been adopted for driving compressors with variable capacity and saving power consumption. .
In the case of a brushless motor, the rotation position signal of the rotor is usually required to determine the current-carrying phase of the winding.However, depending on the usage environment of the motor, such as when the motor is exposed to a refrigerant like an air conditioner or a refrigerator compressor. Rotor permanent magnet
In some cases, it is difficult to arrange a position detection sensor that detects For this reason, there has been proposed a technique for detecting a voltage induced by a permanent magnet in a winding of a motor and electrically processing the voltage to obtain a rotational position signal. Since no induced voltage is generated when the motor is stopped, commutation is forcibly performed to rotate the motor, and when a sufficiently detectable induced voltage is generated, control for performing commutation based on the rotational position detection signal based on the induced voltage is performed. Is being done.

The prior art will be described with reference to FIGS. 6 and 7. FIG. In FIG. 6, a capacitor 2 is connected to a DC power supply 1 in parallel. The positive power supply line 1a of the DC power supply 1 is connected to a positive input terminal of a three-phase bridge circuit 3 as a switching circuit, and the negative power supply line 1b is connected to a negative input terminal of the three-phase bridge circuit 3. I have. The three-phase bridge circuit 3 includes transistors T1 to T6 as switching elements. The output terminal 3u of the three-phase bridge circuit 3,
3v, 3w, the respective windings 4u, 4v,
4w is connected.

An energizing signal forming circuit 5 as energizing signal forming means includes a rotational position detecting circuit 6 and a commutation timing determining circuit 7, and the rotational position detecting circuit 6 has output terminals 3u and 3v. , 3w terminal voltages Vu, Vv, Vw
Are supplied by the commutation timing determination circuit 7, and the energization signals XU +, XU-, XV +,
XV-, XW + and XW- are formed. This energization signal X
U +, XU-, XV +, XV-, XW +, XW- are supplied to the switching circuit 8.

On the other hand, the variable frequency clock generation circuit 9
The clock frequency is varied on the basis of the frequency command signal Sf given from the start control circuit 10 and is given to the forced energizing signal forming circuit 11 as the forced energizing signal forming means. The forcible energization signal forming circuit 11 generates the forcible energization signals YU +, YU-, YV +, Y in a predetermined pattern.
V-, YW +, and YW- are output and provided to the switching circuit 8. The start control circuit 10 has a timer function, and outputs a frequency command signal Sf at a predetermined time at the time of start and outputs a selection signal Sc at a high level.

When the selection signal Sc is at the high level, the switching circuit 8 outputs the forced energization signals YU +, YU-, YV +,
YV-, YW +, YW- are selected, and based on this, the base drive control signals U +, U +,
U-, V +, V-, W +, W-
To each of the unit drive circuits 12a to 12f, and the selection signal Sc
Is low level, the energization signals XU +, XU-, XV +, XV-, XW +, XW- based on the rotation position detection are selected, and based on this, the base drive control signals U +, U-, V + for the transistors T1 to T6 are selected. , V-, W +,
W- is output.

FIG. 7 is a flowchart showing the operation of each part at the time of starting. In step S1, the selection signal Sc of the start control circuit 10 is set to a high level, and the switching circuit 8 forces the forced energization signals YU +, YU-, YV.
+, YV-, YW +, YW- are selected, and forced energization of the motor 4 is started. In step S2, the first timer function of the start control circuit 10 sets the predetermined time ta.
The forced energization is continued until elapses. During this predetermined time ta, as shown in step S3, the frequency command signal Sf of the start control circuit 10 is output in a cycle by the second timer function of the start control circuit 10. Then, the commutation frequency of the forced energization is increased in the variable frequency clock generation circuit 9 as shown in step S4. By these actions, the motor 4 rotates, and the motor 4 is increased to the number of rotations at which the induced voltage that enables the detection of the rotational position is generated.

When the predetermined time ta elapses, the energization signal is switched as shown in step S5. That is, the selection signal Sc of the start control circuit 10 is set to the low level, and the switching circuit 8 supplies the energization signal XU based on the detection of the rotational position.
+, XU-, XV +, XV-, XW +, XW- are given by switching, and the motor 4 is driven based on this.

[0009]

As described above,
After the state of forced energization, the operation shifts to energization corresponding to the rotor rotation position. In the forced energized state, the torque generated by the motor has a large ripple, resulting in unstable starting.For example, when applied to an air conditioner compressor, it causes vibration or noise at the time of starting, or causes deterioration of the compressor or peripheral equipment. It is possible that Further, a large current is generated when the motor is started, which leads to an increase in power consumption.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a brushless motor driving method and a brushless motor capable of stably starting in a shorter time.
An object of the present invention is to provide a control device for a siles motor and a compressor .

[0011]

The control of the brushless motor according to the first aspect of the present invention.
The device determines a commutation timing from a terminal voltage of the winding, and a switching circuit having a switching element for sequentially energizing a multi-phase winding of the brushless motor , and corresponds to the commutation timing. Energizing signal forming means for obtaining the energizing signal obtained, a commutation timing is determined at a predetermined time, a forcible energizing signal forming means for obtaining a forcible energizing signal corresponding to the commutating timing, and an energizing mode for the plurality of windings. Estimating means for estimating, at each commutation, whether or not the motor is in a synchronous state from a change in the comparison result between the terminal voltage of each phase winding and the reference voltage during each energizing mode; and Selection means for selecting the energization signal by the energization signal forming means when estimating the signal, and selecting the forcible energization signal by the forcible energization signal forming means when estimating that the state is not synchronized. Depending on the selection result of the selecting means, having characterized in that comprising a drive circuit for driving the switching element. The brushless mode of the invention according to claim 2
The energizing signal forming means according to the first aspect of the present invention, wherein the energization signal forming means determines whether the induced voltage generated in the winding is positive or negative based on a comparison result between the winding terminal voltage and the reference voltage; A commutation timing determining means for determining a commutation timing based on the positive / negative change time. A control device for a brushless motor according to the invention of claim 3.
The device is characterized in that, in the invention of claim 1, when the motor stops rotating at a fixed position, the energizing mode corresponding to the stop position is set as the initial energizing mode. A control device for a brushless motor according to the invention of claim 4.
A switching circuit having a switching element for sequentially energizing a multi-phase winding of the brushless motor , and a commutation timing is determined from a comparison result between a terminal voltage of the winding and a reference voltage. Energization signal forming means for obtaining an energization signal corresponding to the commutation timing; forced energization signal formation means for determining the commutation timing at a predetermined time and obtaining a forced energization signal corresponding to the commutation timing; Estimating means for estimating, at each commutation, whether or not the motor is in a synchronous state based on a comparison result between the terminal voltage of the wire and the reference voltage and the energizing mode for the plurality of windings; and the estimating means estimates the synchronous state. A selecting means for selecting the energizing signal by the energizing signal forming means and selecting the forcible energizing signal by the forcible energizing signal forming means when it is presumed that the state is not synchronized with the energizing signal forming means; Depending on-option results have featured in comprising a drive circuit for driving the switching element. A control device for a brushless motor according to claim 5
In a control device for a brushless motor that drives a compressor without a position sensor, a switching circuit having a switching element for sequentially energizing a multi-phase winding of the brushless motor, and An energization signal forming means for determining an energization signal corresponding to the commutation timing determined from the comparison result between the terminal voltage of the terminal and the reference voltage, and a predetermined energization mode corresponding to the load torque of the compressor as an initial energization signal mode. Determining the current timing at a predetermined time and obtaining a forced current signal corresponding to the commutation timing; a comparison result between a terminal voltage of each phase winding and a reference voltage; Estimating means for estimating, at each commutation, whether or not the motor is in a synchronous state from the energizing mode for the line, and that the estimating means estimates the synchronous state. A selecting means for selecting the energizing signal by the energizing signal forming means and selecting a forced energizing signal by the forcible energizing signal forming means when it is presumed that the state is not synchronized with the energizing signal forming means; and And a driving circuit for driving.

According to a sixth aspect of the present invention, the compressor is a brush
A compressor provided with a brushless motor,
The brushless motor according to any one of claims 1 to 5,
Driven by a motorless control device
It has features.

[0014]

According to the first aspect of the invention, the following operations and effects can be obtained. That is, in the synchronized state, the comparison result between the terminal voltage of the winding of each phase and the reference voltage changes in a predetermined manner according to the conduction mode for the plurality of windings. Therefore, it is possible to estimate whether or not the motor is in the synchronous state based on the energization mode in the operating state and the comparison result between the terminal voltage of each phase winding and the reference voltage. However, according to the first aspect of the present invention, whether or not the motor is in a synchronous state is determined each time of commutation based on a change in the comparison result between the terminal voltage and the reference voltage during each energizing mode. Can be quickly determined. Then, since the commutation is determined each time, even if the synchronization is accidentally determined, it is determined as asynchronous in the subsequent energizing modes, and stable driving can be performed. Further, not only at the time of starting, but also when the motor that has been driven stably becomes suddenly out of synchronization due to some abnormal situation, it is possible to detect the abnormality.

According to the second aspect of the present invention, the energization signal forming means determines whether the induced voltage generated in the winding is positive or negative based on the result of comparison between the winding terminal voltage and the reference voltage, and whether the induced voltage is positive or negative. If the configuration includes a commutation timing determination unit that determines the commutation timing based on the change time, the comparison unit can be used for the estimation.

According to the third aspect of the invention, when the motor stops rotating at a fixed position, the energizing mode corresponding to the stop position is set as the initial energizing mode, so that a stable start can be achieved in a short time. According to the invention of claim 4, the following operation and effect can be obtained. That is, in the synchronized state, the comparison result between the terminal voltage of the winding of each phase and the reference voltage changes in a predetermined manner according to the conduction mode for the plurality of windings. Therefore,
It is possible to estimate whether or not the motor is in the synchronous state based on the energizing mode in the operating state and the result of comparison between the terminal voltage of each phase winding and the reference voltage. The estimating means estimates, at each commutation, whether or not the motor is in a synchronous state from a comparison result between the terminal voltage of each phase winding and the reference voltage, and an energization mode for the plurality of windings. When the synchronization state is estimated, the energization signal by the energization signal forming means is selected, and when it is estimated that the synchronization state is not established, the forced energization signal by the forced energization signal forming means is selected. Therefore, if it is estimated that the motor is in the synchronous state, the current is immediately switched to the energization corresponding to the rotational position, so that the motor can be shifted to the stable rotational state in a short time. Claim 5
According to the invention, in the control device of the brushless motor that drives the brushless motor used in the compressor, in consideration of the fact that the brushless motor stops rotating at a fixed position, it is possible to first drive the switching element in the initial energization mode, The compressor can be shifted to the stable rotation state in a short time. According to the invention of claim 6, it is possible to provide a compressor that can start stably in a short time.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS. 1 to 4, but different parts from FIG. 6 will be described. As shown in FIG. 1, each winding 4u, 4v, 4
The terminal of w is one input of the comparators 22a, 22b and 22c.
Terminals of each winding 4u, 4v, 4w
The voltage is detected. The energization signal forming circuit 21 as the energization signal generation means shown in FIG. 1 determines the sign of the induced voltage generated in each of the windings 4u, 4v, 4w from the comparison result between the winding terminal voltages Vu, Vv, Vw and the reference voltage V0. It has comparators 22a, 22b and 22c as comparing means for judging, and a commutation timing determining circuit 23 as commuting timing determining means for determining a commutation timing based on the positive / negative change time of the induced voltage. Have been. The reference voltage V0 is formed by a reference voltage generation circuit 22d. The reference voltage generation circuit 22d is connected by a resistance voltage dividing circuit (not shown) connected between the positive power supply line 1a and the negative power supply line 1b. It is configured.

FIG. 2 shows the detection of each winding 4u, 4v, 4w.
Shows the waveforms of the terminal voltages Vu, Vv, Vw obtained. About 60
The slope portion over the section of the degree (period Ta) is the induced voltage of the winding, and the square portion is the applied voltage. From FIG. 2, it is understood that the commutation timing is delayed by about 30 degrees from the time when the induced voltage crosses the reference voltage V0.

The terminal voltages Vu, Vv, Vw are output from the comparator 22
a, 22b, and 22c are compared with the reference voltage V0,
Comparison result of each comparator 22a, 22b, 22c (output)
Is as shown in FIG. Each comparison result is provided to the commutation timing determination circuit 23. The commutation timing determination circuit 23 finally determines the energization signals XU +, XU-, XV +, X based on each comparison result and the phase delay of 30 degrees and the like.
V-, XW +, and XW- are synthesized. Energization signal XU +, X
The starting points of U−, XV +, XV−, XW +, and XW− are at a time that is delayed by 30 degrees from the time when the induced voltage crosses the reference voltage V0, and therefore, these energization signals XU +, XU
The phase patterns of −, XV +, XV−, XW +, and XW− match the commutation timing patterns required for the transistors T1 to T6 of the three-phase bridge circuit 3, so that the energization corresponding to the appropriate commutation timing. A signal can be obtained.

The microcomputer 24 functions as estimating means and selecting means. The microcomputer 24 includes comparators 22a and 22a.
b, 22c, and the mode signal MD from the switching circuit 8.

FIG. 4 shows a flow of the operation.
At the start of the start, as shown in step S1, the microcomputer 24 sets the energization mode parameter N to "0" and sets the initial energization mode among the energization modes A, B, C, D, E, and F by a function as a selection means in the microcomputer 24. A mode, for example, energization mode A is selected. In this case, “0” indicates the energizing mode A, “1” indicates the energizing mode B, “2” indicates the energizing mode C, “3” indicates the energizing mode D, and “4” indicates the parameter N. Indicates the energizing mode E, "5"
Indicates the energization mode F. The counting function of the parameter N is a hexadecimal counter. The contents of the energization modes A, B, C, D, E and F are as shown in the following table.

[0023]

[Table 1] That is, as can be seen from this table and FIG. 2, each energization mode has a different on / off pattern for transistors T1 to T6, and energization mode A is a combination pattern of base drive control signals U +, V-. The energizing mode B is a base drive control signal U +, W-, the energizing mode C is a base drive control signal V +, W-, the energizing mode D is a base drive control signal V +, U-, and the energizing mode E is a base drive control signal. W +, U- and the conduction mode F are a combination pattern of the base drive control signals W +, V-. In this energization mode, a current flows as shown in FIG. The brushless motor is operated by selecting this energization mode in a predetermined order.

After step S1, in step S2, the microcomputer 24 sets the selection signal Sc to a high level, whereby the switching circuit 8 causes the forced energization signals YU +, YU-, YV +, YV-, Y
The base drive control signals U +, U-, V +, V-, W +, and W- are output based on the commutation timing of W + and YW-. Then, as shown in step S4, the microcomputer 24 determines whether or not the motor 4 is in a synchronized state (the details of this determination method will be described later). In other words, the driving state
Is determined. If they are not synchronized, the microcomputer 24 sets the energization mode to the next energization mode B by incrementing the energization mode parameter N by "1" as shown in step S5. Then, step S2
And the forced energization control shown in step S3 is executed again.

For example, thereafter, in step S4,
When the synchronization state is estimated, as shown in step S6,
The microcomputer 24 sets the energizing mode to the next energizing mode C by incrementing the current parameter N of the energizing mode by “1”. Thereafter, the microcomputer 24 sets the selection signal Sc to a low level.
As a result, the switching circuit 8 supplies the energization signals XU +, XU-,
Based on the commutation timing of XV +, XV-, XW +, XW-, the base drive control signals U +, U-, V +, V-, W
Output +, W-. Thus, commutation is performed based on the rotation position detection.

As described above, for the first energization, the forced energization is performed, and thereafter, the forced energization signals YU +, YU-, YV +, YV
-, YW +, YW-, or the energization signals XU +, XU-, XV +, XV-, XW +, X based on the detected rotational position.
The base drive control signals U +, U-, V +, V-, W +, W- are output based on any of the commutation timings of W-, and the motor 4 is driven.

Now, the principle of estimating the motor synchronization state will be described. The brushless motor is driven by selecting six types of energizing modes A, B, C, D, E, and F in a predetermined order as shown in FIG. FIG. 2 shows the relationship between the motor applied voltage when sequentially energizing in the predetermined energizing mode and the induced voltage in the ideal synchronous state, and furthermore, the positive power supply line 1a and the negative power supply line as the reference voltage V0. The comparison result of the reference voltage V0 and the motor voltage (the output state of the comparators 22a, 22b, and 22c) is shown using the midpoint potential of 1b. The relationship between the change in the comparison result in the ideal synchronous state and the energization modes A, B, C, D, E, and F is shown in the table above.

During each energization mode, each winding
4u, 4v, 4w terminal voltages are detected (terminal voltage detection
Output process) Input to each of the comparators 22a, 22b, 22c
Cage, each of the comparators 22a, 22b, the outputs of 22c changes as shown in Table. For example, in the period of the energization mode A, "H (output of the comparator 22a), L (comparator 22b
, H (output of comparator 22c) "to" H (output of comparator 22a), L (output of comparator 22b), L (output of comparator 22c) ". If a change in each comparison result is detected in each energization mode, there is a high possibility that the motor is in a synchronized state. Thus, the microcomputer 24 determines the current supply mode and the comparators 22a, 22b, 22
c, the change in the output of the current comparators 22a, 22b, and 22c at each commutation (for each energization mode) (this is the output of the comparator 2).
2a, 22b, 22c to the microcomputer 24) and current energization mode information (this is based on the mode signal MD from the switching circuit 8 and the microcomputer 8
) And the change in the data, it is possible to roughly estimate the synchronization state (determination step) .

By the way, every time commutation occurs, the current comparator 22
Even when the changes in the outputs a, 22b and 22c coincide with the changes in the data, the motor may not be in a synchronized state temporarily. For example, when the rotor is rotating in the reverse direction. However, in the present embodiment, by selecting the forced energization based on the estimation result and the energization by detecting the rotational position, the forward rotation is finally stabilized.

That is, when the rotor is rotated in the forward direction by the first energization, commutation is performed by forced energization, and by the time of transition to the next energization mode, the rotor is accelerated and the rotation speed at which the induced voltage is sufficiently generated Has been reached. in this case,
The result of the estimation based on the comparison result between the terminal voltages Vu, Vv, Vw and the reference voltage V0 is a synchronous state estimation, and energization corresponding to the rotor rotational position is selected and executed (control operation).
About) After that, the rotor is further accelerated in the forward direction by switching to the energization corresponding to the rotor rotation position, and the subsequent estimation result is a synchronization state estimation.
The motor reaches a stable state by energization corresponding to the rotational position.

When the first energization generates a reverse torque and the rotor rotates in the reverse direction, when the first commutation is performed by the forced energization and then the next energization mode is entered, the motor Due to the relationship between the torque and the load torque, the amount and direction of generation of the motor torque and the direction of rotation of the rotor are undefined. At this time, the terminal voltages Vu, V
The result of the estimation based on the comparison result between v and Vw and the reference voltage V0 is likely to be estimated to be asynchronous. However, there is a possibility that the generation of torque in the reverse direction occurs continuously, the rotational speed in the reverse direction increases, and it is estimated that synchronization is achieved. In this case, the current is switched to the energization corresponding to the rotational position. However, it is extremely unlikely that synchronization will be continuously assumed in the next energization mode after the switching, and the energization is switched to the forced energization. As a result, the rotor is naturally braked and rotates in the forward direction. Then, the rotor enters a synchronized state and shifts to energization corresponding to the rotational position.

As described above, according to the present embodiment, when the rotor is rotated in the forward direction by the first energization, the state can be shifted to the stable energization state corresponding to the rotational position in a short time. When the commutation is performed mainly by forcible energization and a synchronous state is established, the state shifts to a stable energized state corresponding to the rotational position. In other words, although the details differ depending on the initial stop position of the rotor and the like, the transition from the forced energization state to the energization corresponding to the rotational position can be made in a minimum time.

Further, according to the present embodiment, the forced energization is switched even when the motor 4 is locked due to a sudden increase in the load torque during the rotation of the motor 4, so that the cause of the increase in the load torque is eliminated. When restarted, restart can be performed automatically.

Further, in this embodiment, the comparison result of the comparison circuits 22a, 22b and 22c of the energization signal forming circuit 21 is used for estimating the synchronization state by comparing the terminal voltage with the reference voltage. In addition, the configuration can be simplified as compared with a case where a dedicated comparing unit is provided for estimation.

In the above embodiment, the initial energizing mode is uniquely set to the energizing mode A. However, when the motor 4 stops rotating at a fixed position, the following may be performed.
For example, when a motor is used for driving a compressor of an air conditioner, as shown in FIG. 5 as a second embodiment of the present invention, the relationship between load torque (pressure on the discharge side and suction side of the compressor) The rotation stop position is always at the fixed position Q. In this case, the stop position of the rotor is always a fixed rotation angle position. The energizing modes corresponding to this fixed position Q (the energizing modes A, B, C, D, E, and F described above)
) Is set as the initial energizing mode, and starting in this initial energizing mode enables stable starting in a short time.

[0036]

As apparent from the above description, the present invention has the following effects.

According to the first aspect of the present invention, whether or not the motor is in a synchronous state is determined each time of commutation based on a change in the comparison result between the terminal voltage and the reference voltage during each energizing mode. Asynchronous decisions can be made quickly. Then, even if it is accidentally determined to be synchronous, it is determined to be asynchronous in the energizing mode after that, and stable driving is possible. Further, not only at the time of starting, but also when the motor that has been driven stably becomes suddenly out of synchronization due to some abnormal situation, it is possible to detect the abnormality. Claim
According to the invention of the sixth aspect, it is possible to provide a compressor capable of performing a stable start in a short time.

[0038]

[0039]

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram showing a signal waveform of each unit.

FIG. 3 is a diagram showing an energization mode.

FIG. 4 is a flowchart for explaining the operation.

FIG. 5 is a circuit diagram showing a relationship between a load torque, a rotation angle, and a stop position according to a second embodiment of the present invention.

FIG. 6 is a circuit diagram showing a conventional example.

FIG. 7 is a flowchart for explaining the operation at the time of starting.

[Explanation of symbols]

3 is a three-phase bridge circuit (switching circuit), 4 is a brushless motor, 4u, 4v, 4w are windings, 11 is a forced energization signal generation circuit (forced energization signal generation means), 12 is a drive circuit, and 21 is an energization signal formation. Circuit (energization signal forming means),
22a, 22b, 22c are comparators (comparison means), 23 is a commutation timing determination circuit (commutation timing determination means),
Reference numeral 24 denotes a microcomputer (estimating means, selecting means).

Claims (6)

(57) [Claims] 1. A switching circuit having a switching element for sequentially energizing windings of a plurality of phases of a brushless motor, and a commutation timing is determined from a terminal voltage of the winding, and the commutation timing is determined. Energizing signal forming means for obtaining an energizing signal corresponding to the above, a forced energizing signal forming means for determining a commutation timing at a predetermined time and obtaining a forced energizing signal corresponding to the commutating timing, energizing the plurality of windings Estimating means for estimating, at each commutation, whether or not the motor is in a synchronous state from the mode and a change in the comparison result between the terminal voltage of each phase winding and the reference voltage during each energizing mode; and A selection means for selecting an energization signal by the energization signal forming means when estimating the synchronization state and selecting a forced energization signal by the forced energization signal generation means when estimating that the state is not synchronized. When, in accordance with the selection result of the selecting means, the control device for a brushless motor comprising a drive circuit for driving the switching element. 2. An energizing signal forming means, comprising: comparing means for determining whether the induced voltage generated in the winding is positive or negative based on the result of comparison between the winding terminal voltage and the reference voltage; and commutation based on the positive / negative change time of the induced voltage. The control device for a brushless motor according to claim 1, further comprising: a commutation timing determining means for determining a timing. If the wherein the motor stops rotating at a constant position, the <br/> brushless motor according to claim 1, characterized in that to set the energization mode corresponding to the stop position as the initial energization mode Control device. 4. A switching circuit having a switching element for sequentially energizing a multi-phase winding of a brushless motor, and determining a commutation timing from a comparison result between a terminal voltage of the winding and a reference voltage. An energization signal forming means for obtaining an energization signal corresponding to the commutation timing; a forced energization signal formation means for determining a commutation timing at a predetermined time and obtaining a forced energization signal corresponding to the commutation timing; Estimating means for estimating, at each commutation, whether or not the motor is in a synchronized state, based on a comparison result between the terminal voltage of the phase winding and the reference voltage and an energizing mode for the plurality of windings; Selecting means for selecting an energizing signal by the energizing signal forming means when estimating the state and selecting a forcible energizing signal by the forcible energizing signal forming means when estimating that the state is not synchronized; Depending on the selection result of the selecting means, the control device for a brushless motor comprising a drive circuit for driving the switching element. 5. A control device for a brushless motor for driving a compressor without a position sensor, comprising: a switching circuit having switching elements for sequentially energizing windings of a plurality of phases of the brushless motor; An energization signal forming means for determining an energization signal corresponding to the commutation timing determined from a comparison result between the terminal voltage of the winding and the reference voltage, and a predetermined energization mode corresponding to the load torque of the compressor as an initial energization signal mode. A forced energization signal forming means for determining a commutation timing at a predetermined time and obtaining a forced energization signal corresponding to the commutation timing; a comparison result between a terminal voltage of a winding of each phase and a reference voltage; Estimating means for estimating, at each commutation, whether or not the motor is in a synchronous state from the energization mode for the windings; Selection means for selecting the energization signal by the energization signal formation means when the power supply signal generation means selects the forced energization signal by the forced energization signal formation means when presuming that the synchronization state is not established, and according to the selection result of the selection means, A control device for a brushless motor, comprising: a drive circuit for driving a switching element. 6. A compressor provided with a brushless motor, wherein the brushless motor is described in any one of claims 1 to 5.
A compressor characterized in that the compressor is driven by a control device of the mounted brushless motor.