JP6057497B2 - DC brushless motor drive device - Google Patents

Description

  The present invention relates to a drive device for a DC brushless motor, and more particularly to a drive device suitable for a DC brushless motor as a drive source for a handpiece used for dentistry or surgery, or a hand tool used for cutting, polishing, or the like.

DC brushless motors are often used for handpiece drive motors used for dentistry and surgical treatment, and for small motors for hand tools used for cutting and polishing.
Since these handpiece and hand tool motors are mounted on products that are held in hand, it is necessary to use them at a low voltage in consideration of suppression of heat generation and prevention of electric shock. Further, these motors need to be driven in a wide range of rotational speeds from a low speed to a high speed. For example, in a dental handpiece used for an implant, when tightening an implant screw, a motor with a rotational speed of several hundred rpm is decelerated and used at several tens of rpm, but when cutting teeth, tens of thousands of rpm Use at rotational speed.
Conventionally, rectangular wave control by 120 ° energization has been used as control of this DC brushless motor, but in recent years, the use of sine wave control by 180 ° energization that can precisely control rotation with low vibration has been expanded. The rectangular wave control by 120 ° energization and the sine wave control by 180 ° energization each have advantages and disadvantages, and various methods for switching the control while referring to the rotational speed of the motor and the like have been proposed.
An example of this switching method is proposed in Patent Document 1. In the proposal of Patent Document 1, sine wave control by 180 ° energization and rectangular wave control by 120 ° energization are switched when the PWM (pulse width modulation) waveform modulation factor becomes 1, The maximum rotation speed is increased and the rated efficiency is improved.

JP 2005-27395 A

Products that are used by hand, such as handpieces and hand tools, can be controlled so that the voltage (drive voltage) supplied to the motor via the terminal does not exceed the upper limit defined by safety standards. Required. However, Patent Document 1 does not give consideration to the above requirements because of a control method for electric products such as air conditioners and refrigerators.
The present invention has been made in order to solve such problems, and controls the drive voltage so as not to exceed the upper limit value defined by, for example, safety standards while selecting sine wave control and rectangular wave control. It is an object of the present invention to provide a DC brushless motor driving device capable of performing the above.

A drive device for a DC brushless motor (hereinafter sometimes simply referred to as a motor) of the present invention includes an inverter and a control unit.
The inverter supplies a drive voltage Vo to the motor. The control unit controls increase / decrease of the drive voltage Vo supplied to the motor via the inverter, and controls one of the sine wave by 180 ° energization and the rectangular wave by 120 ° energization to control the waveform of the drive voltage Vo. .
The control unit of the present invention
The value of the driving voltage Vo supplied to the inverter is decreased by a predetermined value Vh when the sine wave selection state is changed to the rectangular wave selection state, and conversely, the predetermined value Vh is changed when the rectangular wave selection state is changed to the sine wave selection state. Control reversibly to increase only,
The drive voltage Vo is controlled so that the superimposed voltage Vo + Vn of the drive voltage value Vo and the noise voltage Vn applied to the motor terminal is less than a specified voltage Vlim.

In the drive device of the present invention, there are at least two modes for selecting the waveform of the drive voltage Vo.
In the first form, when the actual rotational speed no of the motor is less than the specified rotational speed n1, the control unit selects a sine wave, and when the actual rotational speed no is equal to or higher than the specified rotational speed n1, the control unit Is to select a square wave.
In the second form, when the drive voltage Vo supplied to the motor is less than the specified voltage V1, the control unit selects a sine wave, and when the drive voltage Vo is equal to or higher than the specified voltage V1, the control unit A rectangular wave is selected.

In the drive device of the present invention, there are at least two forms regarding the drive voltage Vo supplied to the inverter.
In the first form, the control unit controls the drive voltage Vo to increase or decrease in accordance with the increase or decrease of the actual rotational speed no of the motor.
In the second form, the control unit controls the drive voltage Vo to be constant regardless of increase or decrease of the actual rotational speed no of the motor.

The drive device of the present invention can be controlled so that the superimposed voltage Vo + Vn considering the noise voltage Vn applied to the motor is less than the specified voltage Vlim. Therefore, the sine wave control and the rectangular wave control can be selected, and the motor drive can be controlled so as not to exceed the upper limit value defined by the safety standard.
In addition, according to the present invention, when the actual rotational speed no of the motor is less than the prescribed rotational speed n1 or the drive voltage Vo is less than the prescribed voltage V1, the motor can be driven by sine wave control, so that the precise rotation with low vibration can be achieved. Can be realized. In addition, when the actual rotational speed no of the motor is the specified rotational speed n1 or more or the drive voltage Vo is the specified voltage V1 or more, the motor is driven by the rectangular wave control. It can be driven up to a high rotational speed.

1 is a circuit diagram showing a motor drive device according to a first embodiment. FIG. It is the wave form diagram which showed typically the logical voltage applied to a motor terminal from an inverter, (a) is the case by the sine wave control by 180 degrees energization, (b) is the rectangular wave control by 120 degrees energization Shows the case. FIG. 2 is a waveform diagram in which noise is added, in which (a) shows a case of sine wave control, and (b) shows a case of rectangular wave control. The vector diagram of the motor voltage in sine wave control is shown. The control content by 1st Embodiment is shown, (a) shows the relationship between the rotational speed of a motor and a converter output voltage, (b) shows the relationship between the rotational speed of a motor, and a conduction angle. It is a flowchart which shows the control procedure of the motor by 1st Embodiment. The vector diagram of the motor voltage in field weakening control is shown. The control content by 2nd Embodiment is shown, (a) shows the relationship between the rotational speed of a motor and a converter output voltage, (b) shows the relationship between the rotational speed of a motor, and a conduction angle. It is a flowchart which shows the control procedure of the motor by 3rd Embodiment.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
[First Embodiment]
A driving apparatus 100 according to the present embodiment controls driving of a DC brushless motor (hereinafter referred to as a motor) 10 incorporated in a dental handpiece. In FIG. In addition to controlling the increase / decrease of the drive voltage Vo supplied to the DC brushless motor (hereinafter referred to as motor) 10 upon receipt of AC power supply, the sine wave control by 180 ° energization (hereinafter simply referred to as sine wave control) and the rectangle by 120 ° energization The waveform of the drive voltage Vo is controlled by selecting from wave control (hereinafter simply referred to as rectangular wave control).

  In FIG. 1, AC power supplied from a commercial power source 1 is supplied to a driving device 100 via a transformer 2. The driving device 100 includes a rectifier 3, and the supplied AC power is converted into DC power by the rectifier 3, and then charged to the capacitor 4 provided in the driving device 100. A step-down converter (hereinafter referred to as a converter) 5 converts an input voltage Vin of the converter 5 supplied from the capacitor 4 through the coil 6 into an output voltage Vo of the converter 5 and outputs the converted voltage. The capacitor 7 is arranged between the inverter 8. To charge. Since this output voltage Vo becomes a drive voltage supplied to the motor 10, it may be called the drive voltage Vo below. The inverter 8 converts the DC power supplied from the capacitor 7 into AC power and supplies the drive voltage Vo to the motor 10 via the motor terminal 9.

The driving device 100 includes a control unit 11. The control unit 11 sends a control signal so that the output voltage (drive voltage) Vo of the converter 5 can be varied. Further, the drive voltage Vo of the motor 10 output from the inverter 8 can be selected and output from sine wave control (typically by 180 ° energization) and rectangular wave control (typically by 120 ° energization). Send a control signal to.
The control unit 11 is composed of a microcomputer including a CPU (Central Processing Unit) as the computing means 11a, a ROM (Read Only Memory), a RAM (Random Access Memory), etc. as the memory 11b, and stores the program stored in the memory 11b. Therefore, the calculation means 11a performs the process of sending the control signal described above.
In addition to the program, the memory 11b constituting the control unit 11 stores information serving as a reference for selecting sine wave control and rectangular wave control. The memory 11b stores information related to a switching rotational speed n1, a critical rotational speed n2, a critical rotational speed n3, noise voltages Vn and Vn ′, and an energization mode, which will be described later.
The details of the drive control of the motor 10 executed by the control unit 11 will be described later.

The driving device 100 includes a detection unit 20.
A detection unit 20 interposed between the inverter 8 and the motor 10 detects the actual rotational speed no of the motor 10. The detection unit 20 detects the drive voltage Vo supplied to the motor 10. The actual rotation speed no and the drive voltage Vo detected by the detection unit 20 are transferred from the detection unit 20 to the control unit 11. The specific means for detection is not limited, and any known means can be applied.

FIG. 2 schematically shows logical voltages applied from the inverter 8 to Vu, Vv, and Vw of the motor terminal 9.
In the case of sine wave control, a PWM waveform 13 obtained by duty-modulating the sine wave 12 is applied to the motor terminal 9 as shown in FIG. The peak value of the PWM waveform 13 is the drive voltage Vo.
However, the PWM waveform actually applied to the motor 10 via the motor terminal 9 becomes a waveform as shown in FIG. 3A due to the influence of surge and noise due to power switching. That is, the noise voltage 14 is generated when the semiconductor switch of the inverter 8 is turned on, and the noise voltage 15 is also generated when the semiconductor switch is turned off. Therefore, the PWM waveform 13 has a voltage characteristic to which the noise voltages 14 and 15 are added. Show.
On the other hand, in the case of rectangular wave control, a voltage obtained by adding an induced voltage 17 to the rectangular wave 16 is applied to the motor terminal 9 as shown in FIG. The peak value of the rectangular wave 16 is the converter output voltage (drive voltage) Vo ′.
However, the PWM waveform actually applied to the motor 10 via the motor terminal 9 becomes a waveform as shown in FIG. 3B due to the influence of surge and noise due to power switching. That is, when the semiconductor switch of the inverter 8 is turned on / off, noise voltages 18 and 19 are generated, and voltage characteristics to which the noise voltages 18 and 19 are added are shown.

The peak value of the voltage due to these surges and noise may be determined by a safety standard or the like depending on the product. For devices such as handpieces used for dentistry and surgical treatment, and hand tools used for cutting, polishing, etc., for example, there is a standard for safety voltage of the International Electrotechnical Commission (International Electrotechnical Commission). Easy to handle.
Here, the maximum value of the voltage defined by this standard is Vlim. In the case of sine wave control, surge and noise voltage are superimposed on the drive voltage Vo. Therefore, if the width of the surge or noise voltage is the noise voltage Vn (see FIG. 3), it is necessary to limit the drive voltage Vo by the control unit 11 so that Vo + Vn is less than the standard maximum value Vlim. Note that the noise voltage Vn includes both surge and noise, and the next noise voltage Vn ′ is the same. Also in the case of square wave control, if the drive voltage Vo ′ and the surge and noise voltage width are the noise voltage Vn ′, the control unit controls the drive voltage Vo ′ so that Vo ′ + Vn ′ is less than the standard maximum value Vlim. 11 need to be limited. The control unit 11 of the drive device 100 according to the present embodiment controls the drive voltages Vo and Vo ′ so that Vo + Vn and Vo ′ + Vn ′ are less than Vlim in both sine wave control and rectangular wave control. .

The control of the drive voltage Vo will be described below with reference to FIG. In FIG. 4, Vm represents a motor voltage, r represents a winding resistance, Lq represents a q-axis inductance, Iq represents a q-axis current, Ke represents an induced voltage constant, and ω represents a rotational angular velocity. Further, the limit voltage of the drive voltage Vo is V1.
The drive voltage Vo needs to be higher than the peak value of the motor voltage Vm, but the modulation rate of the PWM waveform 13 is increased to control the drive voltage Vo and the peak value of the motor voltage Vm as close as possible. Limit the increase in drive voltage Vo.
One of the features of the present embodiment is that the limit voltage V1 is provided. That is, the limit voltage V1 of the drive voltage Vo is selected from values where Vo + Vn is less than the standard maximum value Vlim in the sine wave control. The limit voltage V1 is a reference for selecting sine wave control or rectangular wave control.
When the motor rotation speed is increased from a low speed, the drive voltage Vo increases in proportion to the increase in the motor voltage Vm and reaches the limit voltage V1. The rotation speed of the motor corresponding to the limit voltage V1 is set as a motor rotation speed (hereinafter referred to as switching rotation speed) n1 at which the control unit 11 switches the selection from sine wave control to rectangular wave control, and stored in the memory 11b of the control unit 11 To do.
After switching to the rectangular wave control, when the drive voltage Vo ′ increases, Vo ′ + Vn ′ reaches the standard maximum value Vlim, but a predetermined motor rotation speed reaching Vlim is set as the limit rotation speed n3, and the control unit 11 Is stored in the memory 11b.
In the present embodiment, the drive voltages Vo and Vo ′ are detected by the detection unit 20. On the other hand, the noise voltages Vn and Vn ′ can be measured by operating the driving device 100 in advance, and can be stored in the storage unit 11b of the control unit 11 based on the measurement result, and are the same as the driving voltages Vo and Vo ′. In addition, it can also be obtained by detection in the detection unit 20.

Next, the control content of the control unit 11 in consideration of the above will be described with reference to FIG.
The controller 11 controls the drive voltage Vo to increase as the rotational speed of the motor 10 increases in the process of reaching the commanded rotational speed (command value). Here, in a region where the actual rotational speed no of the motor 10 is less than the switching rotational speed n1, the control unit 11 sets the drive voltage Vo to sine wave control. In this region, the modulation factor of the PWM waveform 13 (FIG. 2) obtained by duty-modulating the sine wave 12 (FIG. 2) is controlled to 1 irrespective of the motor rotation speed.
The switching rotational speed n1 is selected within a range up to a limit rotational speed n2 where Vo + Vn reaches the standard maximum value Vlim (FIG. 5). By setting the switching rotational speed n1 to the limit rotational speed n2, the rotational speed range of the sine wave control can be expanded.

When the actual rotational speed no of the motor 10 increases and reaches the switching rotational speed n1, the control unit 11 switches the selection of the driving voltage no from sine wave control to rectangular wave control. In this rectangular wave control region, the PWM waveform 13 is set to 100% duty and the chopping operation is not performed, and the utilization rate of the power supply voltage is maximized. By doing so, the power utilization rate becomes larger than the case where the PWM modulation rate is 1 in the sine wave control. Therefore, if the rotation speed of the motor 10 is the same before and after switching, the drive voltage Vo can be reduced by Vh by switching to rectangular wave control. This means that by switching the selection from the sine wave control to the rectangular wave control, there is a margin until Vo ′ + Vn ′ reaches the standard maximum value Vlim.
After switching to the rectangular wave control, the control unit 11 increases again the drive voltage Vo ′ decreased by the width of Vh, and increases the motor rotation speed to the limit rotation speed n3 where Vo ′ + Vn ′ reaches the standard maximum value Vlim. Can be increased. When the rotational speed of the motor 10 reaches the limit rotational speed n3, the control unit 11 prohibits the drive voltage Vo ′ from increasing.
As described above, the motor 10 can be driven in the range of the rotational speed from the low speed to the high speed while controlling so that Vo ′ + Vn ′ is less than the maximum value Vlim of the standard.

  By the way, the control unit 11 is provided with a rotation speed required for the operation by the person using the handpiece as a command value. This rotational speed command value is, for example, a low rotational speed of 1000 rpm when used for tightening an implant screw, and a high rotational speed of 25000 rpm when used for tooth cutting. If the switching rotational speed n1 is a value between a low rotational speed and a high rotational speed (for example, 2000 rpm), the motor 10 is driven only by sine wave control when the command value is a low rotational speed. On the other hand, when the command value is a high rotational speed, sinusoidal wave control is performed within the rotational speed range up to the switching rotational speed n1, and rectangular wave control is performed when the rotational speed is equal to or higher than the switching rotational speed n1.

Hereinafter, the control procedure of the motor 10 by the drive device 100 will be described with reference to FIG.
First, the control unit 11 determines the current energization mode (S101). Here, the energization mode is information for specifying whether the control unit 11 selects sine wave control or rectangular wave control. This energization mode is stored in the memory 11 b of the control unit 11. If the energization mode is rectangular wave control (S101 Yes), the control unit 11 instructs the inverter 8 to output the drive voltage Vo as a rectangular wave (S102 rectangular wave control). The inverter 8 outputs the drive voltage Vo to the motor 10 as a rectangular wave according to this instruction.

  The control unit 11 acquires the actual rotation speed no of the motor detected by the detection unit 20 during the rectangular wave control, and the first limit rotation speed n3 stored in the memory 11b of the control unit 11. Are compared (S103). If the actual rotation speed no has reached the first limit rotation speed n3 (No in S103), the control unit 11 prohibits further increase of the drive voltage Vo (S104). Thereafter, the control unit 11 controls the rotation speed of the motor 10 while prohibiting the increase of the drive voltage Vo (S110).

If the actual rotational speed no has not reached the first limit rotational speed n3 (S103 Yes), the control unit 11 compares the actual rotational speed no with the switching rotational speed n1 stored in the memory 11b (S108). If the actual rotational speed no has not reached the switching rotational speed n1 (No in S108), the controller 11 instructs the inverter 8 to continue the rectangular wave control and controls the rotational speed of the motor 10 (S110).
When the actual rotational speed no reaches the switching rotational speed n1 (S108 Yes), the control unit 11 instructs the inverter 8 to output the drive voltage Vo as a sine wave (S109 sine wave control). The inverter 8 outputs the drive voltage Vo as a sine wave to the motor 10 in accordance with this instruction. This control procedure corresponds to a case where the actual rotational speed no of the motor 10 decreases from a state where it is higher than or equal to the switching rotational speed n1 to less than the switching rotational speed n1.

  On the other hand, if the energization mode is determined by the sine wave control and the control unit 11 in S101 (S101 No), the control unit 11 instructs the inverter 8 to output the drive voltage Vo as a sine wave (S105 sine wave control). . The inverter 8 outputs a sine wave to the motor 10 in accordance with this instruction. The control unit 11 acquires the actual rotation speed no of the motor detected by the detection unit 20 during the sine wave control, and obtains this and the switching rotation speed n1 stored in the memory 11b of the control unit 11. Compare (S106). If the actual rotation speed no has reached the switching rotation speed n1 (No in S106), the control unit 11 instructs the inverter 8 to switch the selection of the energization mode from sine wave control to rectangular wave control (S107). The inverter 8 outputs the drive voltage Vo to the motor 10 as a rectangular wave according to this instruction.

  While following the above procedure, the control unit 11 executes the rotational speed control of the motor 10 to finish one cycle of processing, and repeats this at regular intervals.

Here, FIG. 7 shows a motor voltage vector in the field weakening control. In FIG. 7, Id represents a d-axis current, Im represents a motor current, and other symbols are the same as those in FIG.
In the case of field weakening control, the motor voltage Vm can be driven by sinusoidal control up to a higher rotational speed range within the range of the limit voltage V1, but the motor current Im increases as the d-axis current Id increases. The motor current ratio with and without the field weakening control is the ratio of r · Iq in FIG. 4 to r · Im in FIG. 7, and the heat generation of the motor winding increases in proportion to the square of the motor current.
Since handpieces used for dentistry and surgical treatment and hand tools used for cutting, polishing, etc. are held in hand, it is necessary to suppress heat generation. Therefore, in the first embodiment, field-weakening control in which the motor current increases and heat generation increases is avoided, and the rotation speed is increased by switching from sine wave control to rectangular wave control.
As described above, the actual rotation speed no of the motor 10 is less than the switching rotation speed n1 while controlling the drive voltage Vo supplied to the motor 10 via the motor terminal 9 to be less than the voltage Vlim defined by the safety standards. In this case, the motor 10 is driven in a wide range up to a high speed while suppressing heat generation without the field-weakening control by the rectangular wave control when the actual rotational speed no of the motor 10 is higher than the prescribed rotational speed.

[Second Embodiment]
In the first embodiment, the drive voltage Vo is increased to increase the actual rotation speed no of the motor 10, but the present invention can also increase the rotation speed of the motor 10 while keeping the drive voltage Vo constant. . In the second embodiment, an example will be described with reference to FIG. In this example, the driving voltage Vo is constant only for the sine wave control. However, the driving voltage Vo can be constant for both the sine wave control and the rectangular wave control, or only the rectangular wave control is driven. Needless to say, the voltage Vo can be kept constant.
The limit voltage V1 of the drive voltage Vo is set so that Vo + Vn is lower than the standard maximum value Vlim in the sine wave control. At this time, the drive voltage Vo is controlled to be constant so as to coincide with the limit voltage V1. On the other hand, in the rectangular wave control constant, control is performed such that the drive voltage Vo is increased as the rotational speed increases.

  In the sine wave control region, the motor voltage Vm is controlled by changing the modulation factor of the PWM waveform 13 obtained by duty-modulating the sine wave 12. The motor rotation speed when the motor rotation speed increases and the command value of the motor voltage Vm reaches the limit voltage V1 is set as the motor rotation speed (switching rotation speed) n1 that switches the selection from sine wave control to rectangular wave control. And stored in the memory 11b.

After switching to the rectangular wave control, when the drive voltage Vo ′ increases, Vo ′ + Vn ′ reaches the standard maximum value Vlim, but the limit rotational speed of the motor before reaching Vlim is set in the control unit 11 as n3. .
When the actual rotational speed no of the motor 10 increases and reaches the switching rotational speed n1, the control unit 11 switches the selection from sine wave control to rectangular wave control. Since the utilization factor of electric power is larger at 100% PWM duty in rectangular wave control than when PWM modulation rate in sine wave control is 1, if the motor rotation speed is the same before and after switching, the drive voltage Vo can be reduced by Vh.

  After switching to the rectangular wave control, the drive voltage Vo ′ decreased by the width of Vh can be increased again, and the motor rotation speed can be increased to the limit rotation speed n3 where Vo ′ + Vn ′ reaches the standard maximum value Vlim. . Thus, the motor is driven in a range from low speed to high speed while controlling so that Vo ′ + Vn ′ is less than the standard maximum value Vlim.

[Third Embodiment]
In the first embodiment and the second embodiment, the rotational speed of the motor 10 is used as a reference for selection of the sine wave control and the rectangular wave control. Vo) can also be used. This example will be described as a third embodiment.
A control procedure using a voltage value as a reference for selection between sine wave control and rectangular wave control will be described with reference to a flowchart shown in FIG. The basic control procedure in the third embodiment is the same as the control procedure in the first embodiment shown in FIG. 9, the same processes as those in FIG. 6 are denoted by the same reference numerals (step (S) No.) as those in FIG.
While the rectangular wave control is being output (S103), it is determined whether Vo + Vn has reached Vlim (S203). If Vo + Vn reaches Vlim, the control unit 11 prohibits further increase of the drive voltage Vo (S104), thereby guaranteeing drive below the maximum value of the voltage defined by the standard.
On the other hand, when the sine wave control is performed (S105), it is determined whether or not the drive voltage Vo reaches the limit voltage V1 of the sine wave control (S206). If Vo has reached V1 (No in S206), the control unit 11 switches the energization mode to rectangular wave control (S207).

  When the selection is switched from rectangular wave control to sine wave control, that is, when the rotational speed of the motor 10 decreases from a high rotational speed to a low rotational speed, the determination condition is changed. As described above, if the rotation speed of the motor is the same before and after the switching, the drive voltage Vo decreases by the width of Vh when switching from the sine wave control to the rectangular wave control. Therefore, switching of the energization mode from the rectangular wave control to the sine wave control (S109) is executed when Vo becomes V1−Vh or less (S208).

  Although the present invention has been described based on the embodiments, the drive device of the present invention is suitable for DC brushless motors used for handpieces and hand tools, but is applied to drive DC brushless motors for other uses. be able to. Further, the above-described embodiment is merely an example of the configuration of the driving device, and the specific configuration can be changed without departing from the spirit of the present invention. For example, although the commercial power source 1 is used in the above embodiment, other power sources can be used. In that case, the transformer 2, the rectifier 3, the capacitor 4, the converter 5, and the like can be selected.

100 Driving device 5 Step-down converter 8 Inverter 10 DC brushless motor (motor)
11 Control unit 20 Detection unit

Claims (3)

An inverter for supplying a drive voltage Vo to the DC brushless motor;
Controls the increase / decrease of the drive voltage Vo supplied to the motor via the inverter, and controls the waveform of the drive voltage Vo by selecting one of a sine wave by 180 ° energization and a rectangular wave by 120 ° energization. A control unit,
The controller is
The value of the drive voltage Vo is decreased by a predetermined value Vh when shifting from the sine wave selection state to the rectangular wave selection state, and conversely, from the rectangular wave selection state to the sine wave selection state. When shifting, reversibly control to increase by the predetermined value Vh,
The drive voltage Vo is controlled such that the superimposed voltage Vo + Vn of the drive voltage Vo and the noise voltage Vn is less than a specified voltage Vlim.
A drive device for a DC brushless motor. The controller is
If the actual rotational speed no of the motor is less than the prescribed rotational speed n1, select the sine wave,
If the actual rotation speed no is equal to or higher than the specified rotation speed n1, the rectangular wave is selected.
The DC brushless motor driving device according to claim 1. The controller is
3. The DC brushless motor driving apparatus according to claim 1, wherein the driving voltage Vo is controlled to increase or decrease in accordance with an increase or decrease of an actual rotational speed no of the motor.

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