JP2000350490A - Brushless motor control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a brushless motor control device that achieves control, where the phase of the output voltage of an inverter circuit part is adjusted by a closed loop, corresponding to load fluctuation for increasing the efficiency of a motor by an inexpensive and space-saving configuration. SOLUTION: In the brushless motor control device that detects a rotor position and controls an inverter circuit part 2, so that the inverter circuit part 2 rotates at setting speed, a current detection means 8 and a control means 9 are provided, where the current detection means 8 detects the current to a sensorless DC brushless motor 1 as the brushless motor at the input side of the inverter circuit part 2, and the control means 9 controls the phase of the output voltage of the inverter circuit part 2, so that the current of the sensorless DC brushless motor 1 continuously and orthogonally crosses the flux of the magnet of a rotor, based on the detected current value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless motor control device for driving and controlling a brushless motor used in a compressor for an air conditioner.

[0002]

2. Description of the Related Art Conventionally, some compressors for air conditioners and the like use a brushless motor control device that drives a sensorless DC (direct current) brushless motor with a three-phase 120 ° current as a brushless motor. Conventional sensorless DC
As shown in FIG. 7, the brushless motor control device (first conventional example) includes a sensorless DC brushless motor 1 and a switching element, converts a DC voltage into an AC voltage, and applies the DC voltage to the sensorless DC brushless motor 1. Inverter circuit 2 and sensorless DC brushless motor 1
A position detecting circuit unit 3 for detecting the induced voltage of the rotor of the sensorless DC brushless motor 1 from the terminal voltage of the non-energized phase of each of the U, V, and W phases to estimate the position of the rotor.
A microcomputer (hereinafter abbreviated as “microcomputer”) 4 for controlling the output voltage and rotation speed to the sensorless DC brushless motor 1 and a DC power supply 5 for supplying DC input power to the inverter circuit unit 2. I have.

The microcomputer 4 takes in the motor rotation speed and the set rotation speed obtained from the position information of the rotor, and controls the output voltage of the inverter circuit unit 2 so as to match the rotation speed, thereby providing a sensorless DC brushless motor. The number of revolutions of 1 is approaching the set number of revolutions. That is, if the actual rotation speed is higher than the set rotation speed, the output voltage of the inverter circuit unit 2 is lowered, and if the rotation speed is low, the output voltage of the inverter circuit unit 2 is raised to drive the sensorless DC brushless motor 1.

In addition, the inverter circuit 2
As shown in FIG. 8, a shunt resistor 6 is arranged between the DC power supply 5 and the inverter circuit section 2 to protect the inverter circuit element and the like from being destroyed. In some cases, an overcurrent protection circuit 7 that detects and outputs a signal to the inverter circuit unit 2 to protect the inverter circuit unit 2 so as not to cause damage due to the overcurrent is provided.

However, it is inefficient to control the motor only by the rotation speed as in the above-mentioned control method, and in order to obtain the maximum torque of the motor, the phase of the voltage output to the motor is changed so that the magnetic flux and the current are orthogonal. It is necessary to control. Hereinafter, this control will be described. In the case of an SPM (surface type permanent magnet) DC brushless motor in which a magnet is attached to a rotor, the magnetic flux φ _M by the magnet and the winding current I
FIG. 9A shows the relationship between the force and the force F. Around the winding current I, a magnetic flux φ _I (armature reaction) is generated by the winding current I as shown in FIG.
In FIG. 9A, the winding current I is arranged at a position perpendicular to the magnetic flux φ _M , which means that the current is caused to flow so that the magnetic flux is always orthogonal to the current by the control. Thus, the torque becomes the maximum value.

[0009] The relationship between the magnetic flux φ _M generated by the magnet, the magnetic flux φ _I generated by the current, and the resultant magnetic flux φ is as shown in FIG. It has become. That is, it is as shown in the following (Equation 1). φ = φ _M + φ _I (Equation 1) In the case of 120 ° conduction, the magnetic flux φ _I does not become a sine wave, but is shown here as a sine wave for simplification.

The position detection signal detected by the position detection circuit 3 shown in FIG. 7 appears in the non-energized phase among the phases in which the voltage induced by the synthetic magnetic flux φ is energized by 120 °. In the detected composite magnetic flux φ, the magnetic flux φ _M representing the actual position of the rotor magnet includes the magnetic flux φ _I due to the winding current I. The phase is shifted by the phase difference θ shown in FIG. This phase difference theta, determined by the magnitude of the magnetic flux phi _I, which is the magnitude of the winding current I, i.e. varies with the load of the motor.

To obtain the maximum torque of the motor, the magnetic flux φ _M
It is necessary to flow the winding current I at right angles.
Therefore, the motor drive signal from the microcomputer 4 must be output after being advanced by the phase difference θ from the position detection signal based on the synthetic magnetic flux φ. Therefore, there is a brushless motor control device (second conventional example) as shown in FIG. 10 in order to realize the above phase control. This brushless motor control device has a phase shift θ (or winding current I
May be stored the data of the magnetic flux phi _I) inside the microcomputer 4a by, is what determines the θ advance angle of the output voltage with frequency. The microcomputer 4a calculates the advance angle θ of the position detection signal based on the frequency-current table stored therein, and outputs a signal advanced in phase by the advance angle θ to the inverter circuit unit 2.

As another brushless motor control device (third conventional example), a magnetic flux φ _I by a winding current I is used.
Is proportional to the winding current I, as shown in FIG. 11, the winding current I is detected using a current sensor 3a or the like,
There is one that determines the phase shift θ of the position detection signal based on this and outputs an output signal. The microcomputer 4b includes a current sensor 3 for detecting a winding current I of the motor, as shown in FIG.
captures the output of a to estimate the flux phi _I according to the winding current I, calculates the advance angle θ of the output voltage, and outputs a signal advanced in phase by advance θ of the result to the inverter circuit 2 ing. The current sensor 3a is provided in at least two of the three phases U, V, and W of the sensorless DC brushless motor 1.

[0010]

However, in the above-described first conventional brushless motor control device, since only the rotation speed control is performed, the efficiency of the motor is poor and the maximum torque of the motor cannot be obtained. Therefore, in order to improve the efficiency of the motor, control as shown in the second and third conventional examples is performed. However, the second and third conventional examples have the following problems.

In the above-mentioned second conventional example, the advance angle θ (or the magnetic flux φ _I due to the winding current _I ) is stored in the microcomputer in accordance with the frequency, and the advance angle θ of the output voltage is determined according to the frequency. To decide. This control method assumes that the load (current value) for a certain frequency is constant, and the control is in an open loop. In this open-loop control, the magnetic flux and the current cannot be made orthogonal to the load fluctuation, so that the maximum efficiency cannot be obtained. is there.

In the third conventional example, the winding current is detected by using current detecting means such as a current sensor, and the lead angle θ of the output voltage is determined based on the detected winding current. With this control method, control can be performed in a closed loop corresponding to the load, but expensive components such as a current sensor are required, and a relatively large current sensor must be provided outside the motor. However, there is a problem that a large space is required.

SUMMARY OF THE INVENTION The present invention solves these conventional problems, and realizes control for increasing the motor efficiency by adjusting the phase of the output voltage in a closed loop in response to a load change with an inexpensive and space-saving configuration. It is an object of the present invention to provide a brushless motor control device.

[0014]

According to the present invention, there is provided a brushless motor control device comprising: a current detecting means for detecting a current to a brushless motor at an input side of an inverter circuit; and a brushless motor control device based on the detected current value. And control means for controlling the phase of the output voltage of the inverter circuit section so that the current and the magnetic flux of the rotor magnet are always orthogonal to each other.

According to the present invention, the control for increasing the efficiency by performing the phase control of the output voltage in a closed loop in response to the load fluctuation can be realized with an inexpensive and space-saving configuration.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is directed to a brushless motor control device for controlling an inverter circuit so as to rotate at a set number of revolutions by detecting a rotor position. Current detection means for detecting a current to the brushless motor on the input side; and an output of the inverter circuit unit such that the current of the brushless motor and the magnetic flux of the magnet of the rotor are always orthogonal based on the detected current value. A brushless motor control device provided with control means for controlling a phase of a voltage, wherein a magnetic flux due to a winding current is calculated based on the detected current value, and a magnet of a rotor in a composite magnetic flux is calculated from the magnetic flux. The phase of the output voltage of the inverter circuit can be controlled so that the magnetic flux generated by the rotor magnet and the winding current are always orthogonal to each other. Una current sensor can be unnecessary, inexpensive can be realized a state where the orthogonalizing the flux and winding current by the magnet of the rotor in a space-saving arrangement, it is possible to increase the efficiency of the motor.

According to a second aspect of the present invention, there is provided an inverter circuit unit for driving a sensorless DC brushless motor with three-phase 120 ° conduction, and a position detecting circuit unit for detecting a rotor position of the sensorless DC brushless motor. In a brushless motor control device having a shunt resistor arranged in series at a position where all motor currents flow, a current value flowing through the shunt resistor is detected, and based on the detected current value, a motor current and a motor rotor magnet are detected. This is a brushless motor control device provided with control means for controlling the phase of the output voltage of the inverter so that the magnetic flux is always orthogonal to the motor. Can be realized inexpensively and in a small space.

According to a third aspect of the present invention, there is provided the brushless motor control apparatus according to the second aspect, wherein the control means is configured to perform sampling of a current flowing through the shunt resistor at regular intervals of motor rotation. In addition, the fluctuation of the detected current value due to the rotational pulsation can be reduced, and the phase accuracy of the output voltage can be controlled with improved detection accuracy, so that the efficiency of the motor can be further increased.

According to a fourth aspect of the present invention, in the control device for a DC brushless motor according to the second aspect, the control means is configured to adjust a sampling period of a current flowing through the shunt resistor according to the motor speed. The number of current detection samplings can be increased to an appropriate degree so that the number of current detection samplings is too small in the high rotation speed region, and the output voltage control is coarse in the low rotation speed region against sudden changes. This control of the output voltage can be finely controlled so that the average of the current detection can be optimized in a wide range from the low rotation speed region to the high rotation speed region, and the control can be performed by increasing the current detection accuracy. Output voltage control performance can be improved, and motor efficiency can be increased.

Hereinafter, a brushless motor control device according to the present invention will be described based on a specific embodiment. (Embodiment 1) A brushless motor control device according to Embodiment 1 of the present invention shown in FIG. 1 controls an inverter circuit unit 2 so as to detect a rotor position and rotate at a set number of revolutions, similarly to a conventional example. A brushless motor control device for controlling,
Current detecting means 8 for detecting a current to the sensorless DC brushless motor 1 as a brushless motor on the input side of the inverter circuit section 2; and a current for the sensorless DC brushless motor 1 and a magnet for the rotor based on the detected current value. This is different from the conventional example in that a control means 9 for controlling the phase of the output voltage of the inverter circuit section 2 so that the magnetic flux always crosses at right angles is provided.

The current detecting means 8 includes, for example, a shunt resistor 6 arranged in series at a position where all motor currents flow, and a current detecting circuit section 10 for detecting a current flowing through the shunt resistor 6.
It is composed of The control means 9 is provided in the microcomputer 11 which controls the output voltage to the motor, the phase and the number of rotations. The inverter circuit section 2 is configured by a switching element, and converts a DC voltage into an AC voltage and applies the AC voltage to the motor. The position detection circuit unit 3 detects the induced voltage due to the magnetic flux φ of the motor rotor from the terminal voltage of the non-energized phase among the U, V, and W phases of the brushless motor, and estimates the position of the rotor. . DC power supply 5
Supplies DC input power to the inverter circuit unit 2.

Here, this sensorless DC brushless model
Data 1 is controlled by PAM (Pulse Amplitude Modulation:
(Pulse amplitude modulation)
The relationship between the motor terminal voltage and the current will be described. In FIG.
As shown, U, of the sensorless DC brushless motor 1
The terminal voltage of each of the V and W phases is V_U, V_V, V_WWhen
And the winding current of each of the U, V, and W phases is_U, I_V,
I_WAnd flows to the theoretical shunt resistor excluding noise
Current I _RS As shown. AC motor for DC motor
Since there is no reactive power component as seen in the
I_U, I_V, I_WIs the terminal voltage as shown in FIG.
V_U, V _V, V_WTheoretically have the same phase. In FIG.
As shown, in the phase switching pattern 1, the current is U
The current flows from the phase to the V phase, and no current flows to the W phase. Therefore,
I of the current of the shunt resistor 6_RS Is the current flowing in the U-phase
Become the same. In phase switching pattern 2, the current is
Since it flows from the U phase to the W phase and not to the V phase, the shunt resistor
Current I of anti-6_RS Becomes the same as the current flowing in the U phase.
The same applies to other phase switching patterns, so the shunt resistance
6 current I_RS Is theoretically a current flowing through the motor.

In the position detection circuit section 3 shown in FIG. 1, the position of the rotor of the motor is detected by the induced voltage of the synthetic magnetic flux φ appearing in the non-energized phase during the 120 ° energization.
As can be seen from (b), in order to determine the actual position of the rotor, the magnetic flux φ _I due to the winding current I must be removed. Here, the relationship between the rotation speed and the control of the brushless motor control device will be described.

As shown in FIG. 3, after the rotation speed of the motor reaches the set rotation speed and is stabilized, the current I _RS flowing through the shunt resistor 6 is detected by the current detection circuit 10, and a filter circuit (not shown) is used. Alternatively, the microcomputer 11 removes high frequency components from the detected current _IRS , and the microcomputer 11
The winding current I is calculated using the current I _RS from which the high-frequency component has been removed.
Calculates by magnetic flux phi _I, obtains a phase difference θ between the magnetic flux phi _M by the magnet of the detected synthesized magnetic flux phi and the rotor from the position detection signal, orthogonal to the magnetic flux phi _M and the winding current I by the magnet of the rotor So that the maximum efficiency can be obtained.
Control the phase of the output voltage. Specifically, the microcomputer 1
1, to increase the advance of the phase of the output voltage of about inverter circuit 2 is greater current _{I RS θ (0~π / 4)} .

With this configuration, a current sensor as in the prior art can be dispensed with, and a state in which the magnetic flux φ _M by the rotor magnet and the winding current I are orthogonal to each other in an inexpensive and space-saving configuration. And the efficiency of the motor can be increased. In the first embodiment, since the magnetic flux φ _M generated by the rotor magnet and the winding current I can always be orthogonalized to increase the efficiency of the motor, the winding current I can be reduced to an optimum level. the amplitude of the magnetic flux phi _I by winding current I shown in (b) can be reduced to an optimum extent, this flux phi _I
Can be reduced to an optimum degree.

(Second Embodiment) The control means of the second embodiment has a function of sampling the current flowing through the shunt resistor 6 at regular intervals of the motor rotation, in the control means 9 of the first embodiment. This is an additional configuration. Specifically, noise is removed from the current flowing through the shunt resistor 6 by the microcomputer 11 or a filter circuit (not shown),
The microcomputer 11 averages the current value after the noise removal at regular intervals synchronized with the rotation of the motor.

FIG. 2 is a diagram theoretically showing the relationship between the motor terminal voltage and the current when the DC brushless motor is controlled to have a three-phase 120 ° conduction. Since a current component sometimes flowing in the reverse direction and a component due to the reactance of the motor are included, the winding current of each phase has a pulsation as shown in FIG. Because of such pulsations, in the second embodiment, the average of the current after noise removal is set for each cycle (electric angle / mechanical angle) as shown in FIG. Do it.
As shown in FIG. 5, the current values after noise removal are averaged for each cycle regardless of the number of rotations of the motor. However, the sampling interval is constant regardless of the number of rotations of the motor.
When the motor as shown in (a) is rotating at high speed,
The sampling number is, for example, 12 points.
If the motor as shown in (b) is rotating at low speed,
The sampling number is, for example, 24 points.

In this manner, the pulsation is removed from the pulsating current waveforms shown in FIG. 4 to remove the pulsation-free winding current of each phase and the current flowing through the shunt resistor 6 as shown in FIG. Have gained. Here, the average of the current after noise removal is set for each cycle, but may be set arbitrarily such as for every 1/6 cycle.

Here, the control of the sensorless DC brushless motor 1 is referred to as PAM (Pulse Amplitude Modulation:
The relationship between the motor terminal voltage and the current when three-phase 120 ° conduction is performed in the pulse amplitude modulation) system will be described. As shown in FIG. 2, the terminal voltages of the U, V, and W phases of the motor are V _U , V _V , and V _W, and the winding currents of the U, V, and W phases are I _U , I _V , Let I _W be the current flowing through the shunt resistor, excluding noise, I _RS As shown. In the case of a DC motor, since there is no reactive power component as seen in an AC motor, the winding currents I _U , I _V , and I _W are, as shown in FIG. 2, changed to terminal voltages V _U , V _V , and V _W. On the other hand, they have the same phase theoretically. As shown in FIG. 2, in the phase switching pattern 1, a current flows from the U phase to the V phase, and no current flows in the W phase. Therefore, I _RS of the current of the shunt resistor 6 Is the same as the current flowing in the U phase. Further, in the phase switching pattern 2, since the current flows from the U phase to the W phase and does not flow to the V phase, the current I _{RS of the} shunt resistor 6 Becomes the same as the current flowing in the U phase. Since the same applies to other phase switching patterns, the current I _{RS of the} shunt resistor 6 is Is theoretically a current flowing through the motor.

In the position detection circuit unit 3 shown in FIG. 1, the position of the rotor of the motor is detected by the induced voltage of the magnetic flux φ appearing in the non-energized phase during the 120 ° energization.
As can be seen from (b), in order to determine the actual position of the rotor, the magnetic flux φ _I due to the winding current I must be removed. Here, the relationship between the rotation speed and the control of the brushless motor control device will be described.

As shown in FIG. 3, after the rotation speed of the motor reaches the set rotation speed and stabilizes, the current I _RS flowing through the shunt resistor 6 Is detected by a current detection circuit 10 and a current I _RS detected by a filter circuit (not shown), a microcomputer 11 or the like. And removes high-frequency components from the
The current value from which the high-frequency component has been removed is averaged for each cycle synchronized with the rotation of the motor to obtain a pulsation-free current. Using this pulsation-free current, the magnetic flux φ _I by the winding current _I is calculated. obtains the magnetic flux phi _M by the magnet of the rotor in the synthetic magnetic flux phi detected from the position detection signal, the inverter for maximum efficiency is obtained by orthogonalizing the flux phi _M and the winding current I by the magnet of the rotor The phase of the output voltage of the circuit unit 2 is controlled. Specifically, the microcomputer 11 outputs the current I _RS Is larger, the advance angle θ (0) of the phase of the output voltage of the inverter circuit unit 2 is larger.
To π / 4).

With this configuration, a current sensor as in the prior art can be dispensed with, and a state in which the magnetic flux φ _M generated by the rotor magnet and the winding current I are orthogonal to each other can be realized in an inexpensive and space-saving configuration. Can be realized. Further, by detecting the current value after removing noise from the current flowing through the shunt resistor 6 at regular intervals synchronized with the rotation of the motor and detecting the average value, fluctuations in the current detection value due to rotational pulsation can be reduced. Since the detection accuracy can be increased and the phase control of the output voltage can be performed, the efficiency of the motor can be further increased.

(Third Embodiment) The control means of the third embodiment has a function of adjusting the sampling period of the current flowing through the shunt resistor 6 in accordance with the motor rotation speed, in accordance with the control means 9 of the first embodiment. Is added. Specifically, noise is removed from the current flowing through the shunt resistor 6 by the microcomputer 11 or a filter circuit (not shown), and the microcomputer 11 sets the cycle of averaging the current value after removing the noise in accordance with the rotation speed of the motor. I am adjusting it.

When the current is detected as in the above-described second embodiment, it works effectively in the rotation speed region where the sampling number is set well, but in the high rotation speed region, the current sampling number which becomes the control base is controlled. And the sampling time is long in the low rotation speed region, so that the output voltage control does not follow a sudden change in current. In order to solve such a problem, the microcomputer 11 adjusts the cycle of averaging the current value after noise removal according to the number of rotations of the motor.

Here, an operation of adjusting the cycle of averaging the current value after noise removal by the microcomputer 11 according to the number of rotations of the motor will be described. As shown in FIG.
In the high rotation speed region, the current average period is lengthened to control the phase of the output voltage of the inverter circuit unit 2, and as shown in FIG. 6B, the current averaging period is controlled to be short in the low rotation speed region. . That is, the current averaging time is adjusted so that it does not greatly change depending on the rotation speed.

With this configuration, the current detection sampling number can be appropriately increased so that the current detection sampling number is not too small in the high rotation speed region.
This control of the output voltage can be finely controlled so that the control of the output voltage is not delayed in the low rotation speed region, and the average of the current detection can be optimized in a wide range from the low rotation speed region to the high rotation speed region. By increasing the current detection accuracy and controlling the output voltage, the output voltage control performance can be improved and the efficiency of the motor can be increased.

[0037]

As described above, according to the brushless motor control device of the present invention, the current detection means for detecting the current to the brushless motor at the input side of the inverter circuit section, and the brushless motor based on the detected current value. Control means for controlling the phase of the output voltage of the inverter circuit unit so that the current of the motor and the magnetic flux of the magnet of the rotor are always orthogonal to each other, so that the winding current is determined based on the detected current value. Calculate the magnetic flux, find the magnetic flux of the rotor magnet in the composite magnetic flux from this magnetic flux, and control the phase of the output voltage of the inverter circuit so that the magnetic flux of the rotor magnet and the winding current are always orthogonal. This eliminates the need for a current sensor as in the past, and realizes a state in which the magnetic flux generated by the rotor magnet and the winding current are orthogonal to each other with an inexpensive and space-saving configuration. Bets can be, it is possible to increase the efficiency of the motor.

In the case where the current detecting means is configured to detect a current value flowing through a shunt resistor arranged in series at a position where the entire motor current flows, the magnetic flux generated by the magnet of the rotor and the winding current are determined. Raising the motor efficiency by making the motors orthogonal to each other can be realized inexpensively and in a small space. Further, when the control means is configured to perform sampling of the current flowing through the shunt resistor at every fixed cycle of the motor rotation, the current value flowing through the shunt resistor is averaged at every fixed cycle synchronized with the rotation of the motor. By detecting, fluctuations due to rotational pulsation of the current detection value can be reduced,
Since the phase control of the output voltage can be performed by increasing the detection accuracy, the efficiency of the motor can be further increased.

In the case where the control means is configured to adjust the sampling period of the current flowing through the shunt resistor according to the motor rotation speed, the current detection sampling number may be too small in the high rotation speed region. The number can be increased to an appropriate degree, and the output voltage control can be finely controlled so that the control of the output voltage does not become slow in the low rotation speed region, and in a wide range from the low rotation speed region to the high rotation speed region. , The average of the current detection can be optimized, and the performance of the output voltage control can be improved by increasing the current detection accuracy and controlling.
The efficiency of the motor can be increased.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a brushless motor control device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing current / voltage waveforms of main parts of the first embodiment.

FIG. 3 is an explanatory diagram showing a relationship between a rotation speed and control in the first embodiment.

FIG. 4 is a diagram showing current / voltage waveforms before averaging according to the second embodiment of the present invention.

FIG. 5 is a view for explaining sampling intervals according to the second embodiment;

FIG. 6 is a diagram illustrating adjustment of a sampling period according to the third embodiment of the present invention.

FIG. 7 is a block diagram showing the configuration of a first conventional example of a brushless motor control device.

FIG. 8 is a block diagram in which an overcurrent protection circuit is provided in the first conventional example.

FIG. 9 is a magnetic flux distribution diagram showing a magnetic flux by a magnet of a rotor and a magnetic flux by a winding current.

FIG. 10 is a block diagram showing a configuration of a second conventional example of a brushless motor control device.

FIG. 11 is a block diagram showing a configuration of a third conventional example of a brushless motor control device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sensorless DC brushless motor 2 Inverter circuit part 3 Position detection circuit part 5 DC power supply 6 Shunt resistor 8 Current detection means 9 Control means 10 Current detection circuit part 11 Microcomputer

Claims (4)

[Claims] 1. A brushless motor control device for detecting a rotor position and controlling an inverter circuit portion to rotate at a set number of revolutions, wherein current detection means for detecting a current to the brushless motor at an input side of the inverter circuit portion. And a control means for controlling a phase of an output voltage of the inverter circuit unit based on the detected current value so that a current of the brushless motor and a magnetic flux of a magnet of the rotor are always orthogonal to each other. Control device. 2. A three-phase sensorless DC brushless motor.
In a brushless motor control device having an inverter circuit unit driven by 20 ° conduction, a position detection circuit unit for detecting a rotor position of the sensorless DC brushless motor, and a shunt resistor arranged in series at a position where all motor currents flow. A control means for detecting a current value flowing through the shunt resistor and controlling a phase of an output voltage of the inverter based on the detected current value so that a motor current and a magnetic flux of a motor rotor magnet are always orthogonal to each other. Brushless motor control device. 3. The brushless motor control device according to claim 2, wherein the control means is configured to sample the current flowing through the shunt resistor at every fixed period of the motor rotation. 4. The brushless motor control device according to claim 2, wherein the control means adjusts a sampling period of the current flowing through the shunt resistor according to the motor speed.