JP2008306879A - Drive unit for brushless dc motor and drive method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drive unit capable of smoothly starting up a brushless DC motor with a Hall element for detecting a magnetic pole. <P>SOLUTION: When the brushless DC motor 21 is started up, a period calculating unit 45 calculates a period Ts at an electrical angle of 60° based on a start-time speed command value Vs set in a speed setting unit 41. An inverter 22 is switched by the phase switching signal of a phase switching signal generating unit 24 every the period Ts. A voltage setting unit 44 sets a voltage command value which allows a starting torque required for staring to be generated. A PWM signal generating unit 25 generates a PWM signal corresponding to the voltage command value and transmits it to a switching signal generating unit 24. When the brushless DC motor 21 reaches a predetermined rotation speed, switches SW1, SW2 switch to side-a to implement speed control by PID 43. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a driving apparatus and a driving method for a brushless DC motor using a Hall element as a magnetic pole detection sensor.

  A brushless DC motor generally forms a phase switching signal of a predetermined excitation pattern, switches an inverter by the phase switching signal, sequentially supplies an excitation current to a three-phase coil, generates a rotating magnetic field, and rotates with a permanent magnet. The child is configured to rotate following the rotating magnetic field. And the excitation pattern which forms a phase switching signal is formed using the magnetic pole detection signal of a Hall element (magnetic pole detection sensor). In this case, a drive device has been proposed in which the excitation pattern is formed using the magnetic pole detection signal of the Hall element when the brushless DC motor is in a steady drive state, and is formed without using the magnetic pole detection signal of the Hall element at startup. (See Patent Document 1).

FIG. 5 is a block diagram of a brushless DC motor driving apparatus that forms an excitation pattern without using the magnetic pole detection signal of the Hall element when starting the brushless DC motor.
In FIG. 5, 11 is a permanent magnet rotor R, a brushless DC motor comprising three-phase coils U, V, W, and 12 is one Hall element (N, S) for detecting the magnetic poles (N, S) of the rotor R. Magnetic pole detection sensor). Reference numeral 13 denotes a magnetic pole detection signal forming circuit that forms a magnetic pole detection signal based on the output of the Hall element 12, and reference numeral 14 denotes a timer circuit that measures the period of the magnetic pole detection signal. 151 is an excitation pattern forming circuit for forming an excitation pattern (starting excitation pattern) for starting a stationary rotor R, 152 is an excitation pattern forming circuit for forming an excitation pattern during steady driving, and 16 is , An excitation pattern selection circuit for selecting an excitation pattern of the start excitation pattern formation circuit 151 or the excitation pattern formation circuit 152. Reference numeral 17 denotes a drive circuit composed of an inverter or the like.

The drive circuit 17 forms a phase switching signal according to the excitation pattern of the starting excitation pattern forming circuit 151 or the excitation pattern forming circuit 152, and controls the switching of the inverter by the phase switching signal, so that the three-phase coil of the brushless DC motor 11 is formed. The excitation current is sequentially supplied to U, V, and W.
The excitation pattern forming circuit 152 forms an excitation pattern using the magnetic pole detection signal, while the starting excitation pattern forming circuit 151 forms a starting excitation pattern without using the magnetic pole detection signal.

JP-A-9-163787

It is not clear how the conventional brushless DC motor driving device creates the starting excitation pattern at the start-up without using the magnetic pole detection signal of the Hall element. Also, it is not clear how to take (set) the initial electrical angle at startup. For this reason, the conventional brushless DC motor driving device sometimes reverses the electric angle by a maximum of 180 degrees at the time of activation, and it is difficult to smoothly activate the brushless DC motor and increase the rotation speed smoothly.
In view of this point, an object of the present invention is to provide a brushless DC motor starting device and a starting method capable of smoothly starting a brushless DC motor and smoothly increasing a rotation speed.

In order to achieve the object of the present invention, the brushless DC motor driving device according to claim 1 includes a permanent magnet rotor and a three-phase coil, and includes three Hall elements for detecting the magnetic poles of the rotor. In the drive device of the brushless DC motor provided,
A magnetic pole detection signal generator for generating a magnetic pole detection signal from the outputs of the three Hall elements;
An electrical angle determination unit for determining an electrical angle from a magnetic pole detection signal;
A cycle calculating unit that calculates a cycle of an electrical angle of 60 degrees based on a speed command value at startup;
The rotor position setting signal corresponding to the updated electrical angle cycle is generated by updating the electrical angle by 60 degrees based on the electrical angle initial value based on the cycle of the cycle calculation unit and the electrical angle initial value of the electrical angle determination unit. Rotor position setting section,
A voltage setting unit for setting the voltage command value at startup,
Constant speed control unit,
A PWM signal generator that generates a PWM signal corresponding to a voltage command value at startup or a speed control signal of a steady-state speed controller;
A phase switching signal generator for generating a phase switching signal based on a rotor position setting signal or a magnetic pole detection signal in a steady state and a PWM signal;
A phase switching unit that is driven by a phase switching signal and supplies an excitation current to the three-phase coil is provided.
The brushless DC motor drive device according to claim 2 is the brushless DC motor drive device according to claim 1, wherein the voltage command value at the time of startup and the speed control signal selector switch, the rotor position setting signal And a switch for switching the magnetic pole detection signal in the steady state, and a switch driving unit for driving these switches.
The brushless DC motor drive device according to claim 3 is the brushless DC motor drive device according to claim 2, wherein the switch drive unit sets the switch to a voltage command value at the start-up time when the brushless DC motor is started up. And switching to the rotor position setting signal side.
The brushless DC motor drive device according to claim 4 is the brushless DC motor drive device according to claim 2, wherein the switch drive unit switches the switch when the rotational speed of the brushless DC motor becomes higher than a predetermined speed. Switching to the speed control signal side and the steady-state magnetic pole detection signal side is characterized.
The brushless DC motor drive device according to claim 5 is the brushless DC motor drive device according to claim 2, wherein the switch drive unit switches the switch when the rotational speed of the brushless DC motor becomes lower than a predetermined speed. Switching to the voltage command value side at startup and the rotor position setting signal side is characterized.
The driving method of the brushless DC motor according to claim 6 is a driving method of a brushless DC motor comprising a permanent magnet rotor and a three-phase coil, and comprising a Hall element for detecting a magnetic pole of the rotor.
The electrical angle initial value is determined by the magnetic pole detection signal generated by the outputs of the three Hall elements,
Calculate the period of electrical angle 60 degrees using the speed command value at startup,
A rotor position setting signal corresponding to the cycle of the electrical angle updated by updating the electrical angle by 60 degrees based on the electrical angle initial value based on the cycle and the electrical angle initial value is generated,
A phase switching signal is generated by the rotor position setting signal and the PWM signal corresponding to the voltage command value at the time of startup,
A phase switching unit is driven by a phase switching signal to supply an exciting current to a three-phase coil.

  The present invention sets a speed command value at startup based on the acceleration characteristics of the brushless DC motor, calculates a period Ts of 60 electrical angles based on the speed command value, and outputs the three Hall elements. The electrical angle initial value is determined based on the generated magnetic pole detection signal, the cycle Ts is updated based on the electrical angle initial value, and the phase switching signal is sequentially generated every updated cycle Ts to generate the three-phase coils U, V, W. Therefore, the rotor smoothly follows the rotating magnetic field of the three-phase coils U, V, W, and the brushless DC motor starts up smoothly.

Further, the present invention provides a voltage setting unit used at startup, and controls the excitation current of the three-phase coils U, V, W at startup using the voltage command value of the voltage setting unit. Sometimes a large starting torque can be generated, and the starting is smooth even when the load is large or the wheelchair starts on a slope. And since a voltage setting part is used only at the time of starting, it does not flow an exciting current larger than necessary at the time of steady driving. Therefore, useless power consumption can be eliminated.
Further, since the present invention can be driven to decelerate only by using the speed command value at the time of start-up at the time of deceleration, it can be smoothly decelerated using the same device as at the time of start-up.

  A driving apparatus for a brushless DC motor according to an embodiment of the present invention will be described with reference to FIGS. In addition, the same code | symbol is used for the part common to each figure.

FIG. 1 shows the configuration of a brushless DC motor driving apparatus according to an embodiment of the present invention.
21 is a brushless DC motor comprising a rotor of a three-phase coil and a permanent magnet, 22 is a phase switching unit (inverter) for sequentially supplying an excitation current to the three-phase coil of the brushless DC motor 21, 23 is a DC power source, 24 Is a phase switching signal generator for generating six types of phase switching signals Vu ±, Vv ±, Vw ± for sequentially switching the inverter 22 according to a predetermined excitation pattern (pattern for exciting the coil of the brushless DC motor), 25 The PWM signal generator generates a PWM (pulse width modulation) signal (rectangular wave) to be supplied to the phase switching signal generator 24.
Reference numeral 31 denotes three Hall elements (Hall sensors) for detecting the magnetic poles (N pole and S pole) of the rotor of the brushless DC motor 21, and 32 denotes magnetic pole detection signals Vsu, Vsv, A magnetic pole detection signal generating unit 33 that generates Vsw is an electrical angle determination unit that determines an electrical angle (hereinafter referred to as an electrical angle) θ of the motor based on the magnetic pole detection signal, and 34 is based on the magnetic pole detection signal. A speed calculation unit 35 that calculates the rotation speed of the rotor 35 is a switch drive unit that switches the switches SW1 and SW2.

41 is a speed setting unit that sets a speed command value (speed target value) Vs of the rotor of the brushless DC motor 21, and 42 is a speed command value Vs of the speed setting unit 41 and a speed calculated by the speed calculation unit 34. A speed deviation calculating unit 43 that calculates a speed deviation, 43 is a PID (proportional / integral / differential) that performs speed control according to the speed deviation, 44 is a voltage setting unit, and 45 is a speed command value Vs of the speed setting unit 41. The period calculation unit 46 calculates a period (time length) Ts of an electrical angle of 60 degrees (described later) based on the electrical angle θ based on the electrical angle initial value determined by the electrical angle determination unit 33 as 60 degrees. It is a rotor position setting unit that updates the position one by one (also updates the period Ts) and generates the rotor position setting signals Vpu, Vpv, and Vpw corresponding to the updated 60-degree period Ts.
Here, since the speed setting unit 41, the speed calculation unit 34, the speed deviation calculation unit 42, and the PID 43 perform speed control during steady driving, they are collectively referred to as a steady speed control unit.

The switches SW1 and SW2 are switched to the b side at the time of startup, but are switched to the a side at the time of steady driving. When the switches SW1 and SW2 are switched to the b side, the rotor position setting unit 46 is connected to the phase switching signal generating unit 24, the voltage setting unit 44 is connected to the PWM signal generating unit 25, and to the a side. When switching, the magnetic phase detection signal generation unit 32 is connected to the phase switching signal generation unit 24, and the PID 43 is connected to the PWM signal generation unit 25 (that is, the steady-state speed control unit is connected). Therefore, the a side of the switches SW1 and SW2 is referred to as a steady time side, and the b side is referred to as a start-up / deceleration side.
The switch SW3 is a start switch and closes when operated (when pressed) when starting the brushless DC motor 21.

The speed command value Vs of the speed setting unit 41 includes a speed command value at the time of steady driving of the brushless DC motor 21 and a speed command value at start-up and deceleration (during stop). When the brushless DC motor 21 is used for a wheelchair, for example, the speed command value Vs at the time of steady driving is set corresponding to the joystick operation amount of the wheelchair. The speed command value Vs at the time of start-up / deceleration is set in advance based on the acceleration characteristic (rise characteristic of the rotational speed) and the deceleration characteristic at the start-up of the brushless DC motor. Since the rotational speed of the brushless DC motor 21 at the time of startup gradually increases from the stopped state, the speed command value Vs at the time of startup is set so that Vs1 <Vs2 <Vs3 <. Set in the speed setting unit 41. As the speed command value Vs during deceleration, a command value opposite to the speed command value Vs during startup is used.
The speed command value at the time of activation may be configured to be automatically selected when the start switch SW3 is operated.

The period calculation unit 45 calculates a period Ts of an electrical angle of 60 degrees based on the speed command value Vs by Ts (seconds) = 60 degrees / Vs (degrees / second). Therefore, the cycle Ts at the start of the brushless DC motor 21 is Ts1>TS2>Ts3>...> Tsn corresponding to the speed command value Vs1 <Vs2 <Vs3 <. It becomes shorter as the rotation speed becomes faster.
Here, the electrical angle of 60 degrees corresponds to the generation interval of the phase switching signal when the inverter 22 is driven by the three-phase 120-degree energization method.

In the voltage setting unit 44, when starting the brushless DC motor 21, a voltage that can generate a sufficient starting torque for a predetermined maximum load is set so that the brushless DC motor 21 starts smoothly and the rotation speed rises smoothly. For example, when the brushless DC motor 21 is for a wheelchair, the set voltage is set based on the maximum load that the wheelchair can travel, the maximum inclination angle of the hill, and the acceleration characteristics.
When the brushless DC motor 21 is activated and its rotational speed reaches a predetermined speed, the switch drive unit 35 moves the switches SW1 and SW2 from the b side (starting / deceleration side) to the a side (steady time side). Switch. That is, switching is performed from the voltage setting unit 44 side and the rotor position setting unit 46 side to the steady state speed control unit side and the magnetic pole signal generation unit 32 side. Further, when the brushless DC motor 21 is decelerated (stopped), when its rotational speed becomes lower than a predetermined speed, the switch drive unit 35 switches the switches SW1 and SW2 from the a side to the b side as will be described later.

Next, the operation of the brushless DC motor driving device of FIG. 1 will be described.
When the brushless DC motor 21 is stopped, the switches SW1 and SW2 are switched to the b side. When the start switch SW3 is operated at that time, the rotor position setting unit 46 fetches the electrical angle (electrical angle initial value) when the rotor is stopped from the electrical angle determination unit 33 and the cycle calculation unit 45 from the cycle. Capture Ts. As described above, the cycle Ts changes as Ts1>TS2>Ts3>...> Tsn.

  At that time, the electrical angle determination unit 33 uses the magnetic pole detection signals Vsu, Vsv, and Vsw, and the electrical angle when the brushless DC motor 21 is stopped, that is, the electrical angle initial value (the magnetic pole when the rotor is stopped). And the positional relationship between the three-phase coils). The rotor position setting unit 46 updates the electrical angle θ by 60 degrees with reference to the electrical angle initial value determined by the electrical angle determination unit 33, and the rotor position setting signal Vpu corresponding to the updated period of 60 degrees. , Vpv, Vpw are sent to the phase switching signal generator 24. When the electrical angle θ is updated by 60 degrees, the updated period Ts corresponding to 60 degrees is also updated as Ts1> TS2> Ts3>. Therefore, the phase switching signal generation unit 24 takes in the PWM signal (rectangular wave) from the PWM signal generation unit 25 and uses the PWM signal for each cycle Ts updated according to the rotor position setting signals Vpu, Vpv, Vpw. Vu ±, Vv ±, Vw ± are generated. The inverter 22 is driven by the phase switching signals Vu ±, Vv ±, Vw ±, and is sequentially switched by the phase switching signals to supply an excitation current to the coil of the brushless DC motor 21. At that time, the PWM signal generation unit 25 generates a PWM signal corresponding to the voltage command value of the voltage setting unit 44.

  The above is the operation when the brushless DC motor 21 is activated. When the brushless DC motor 21 decelerates (stops), the phase switching signal generator 24 can be controlled using the rotor position setting signal. That is, at the time of deceleration, the rotor position setting unit 46 generates a rotor position setting signal corresponding to the speed command value Vs at the time of deceleration set in the speed setting unit 41. The speed command value Vs at the time of deceleration is opposite to that at the time of start-up, and is set so as to decrease with time such that Vs1> Vs2> Vs3>. Therefore, the period Ts increases with time such that Ts1 <TS2 <Ts3 <. By setting the speed command value Vs in this way, the brushless DC motor 21 is smoothly decelerated and stopped.

  When the brushless DC motor 21 is activated and reaches a predetermined rotational speed, the switch drive unit 35 operates in accordance with a signal from the speed calculation unit 34 and switches the switches SW1 and SW2 to the a side. When the switches SW1 and SW2 are switched to the a side, the magnetic pole detection signals Vsu, Vsv, and Vsw are sent from the magnetic pole detection signal generator 32 to the phase switching signal generator 24. Thereafter, the phase switching signal generator 24 follows the magnetic pole detection signals Vsu, Vsv, Vsw and uses the PWM signal from the PWM signal generator 25 at every electrical angle of 60 degrees to use the phase switching signals Vu ±, Vv ±, Vw ±. Is generated.

On the other hand, the speed deviation calculation unit 42 calculates a deviation (speed deviation) between the speed command value Vs during steady driving of the speed setting unit 41 and the speed calculated by the speed calculation unit 34 and sends the deviation to the PID 43. The PID 43 generates a speed control signal having a magnitude corresponding to the speed deviation based on the speed deviation and sends it to the PWM signal generator 25. The PWM signal generator 25 generates a PWM signal corresponding to the speed control signal. To do. The speed setting unit 41 may be configured to switch from the speed command value at startup to the speed command value at steady driving in conjunction with the switching of the switches SW1 and SW2.
When the brushless DC motor decelerates, if the rotational speed of the brushless DC motor becomes lower than a predetermined speed, the switch driving unit 35 switches the switches SW1 and SW2 from the a side to the b side by a signal from the speed calculating unit 34, Along with the switching, the speed command value Vs of the speed setting unit 41 is switched from the speed command value during steady driving to the speed command value during deceleration.

  The brushless DC motor driving device in FIG. 1 sets a speed command value Vs at startup based on the acceleration characteristics of the brushless DC motor, calculates a cycle Ts based on the speed command value Vs, and for each cycle Ts. Since the sequential phase switching signals Vu ±, Vv ±, and Vw ± are generated, the rotor of the brushless DC motor 21 smoothly follows the rotating magnetic field generated in the three-phase coil. Further, since the brushless DC motor 21 generates a large starting torque based on the voltage command value of the voltage setting unit 44 at the time of starting, the brushless DC motor 21 starts smoothly even when the load is large or when the wheelchair starts on a slope. And since the voltage setting part 44 is used only at the time of starting, it does not flow the excitation current more than necessary at the time of steady driving. Therefore, useless current consumption during steady driving can be reduced.

FIG. 2 shows a specific configuration example of the brushless DC motor 21 and the inverter 22 shown in FIG.
The brushless DC motor 21 includes a three-phase coil U, V, W and a four-pole (N, S, N, S) rotor R, and includes three Hall elements Su, Sv, Sw for detecting the magnetic poles of the rotor. Is arranged. The magnetic pole detection signal generator 32 generates magnetic pole detection signals Vsu, Vsv, Vsw based on the outputs of the Hall elements Su, Sv, Sw. The inverter 22 includes six transistors, and six types of phase switching signals Vu−, Vu +,..., Vw + are supplied to each transistor according to a predetermined excitation pattern. . The six transistors are sequentially turned on and sequentially supply excitation current from the DC power supply 23 to the coils U, V, and W.

Next, with reference to FIGS. 3 and 4, the generation state and generation pattern (excitation pattern) of the phase switching signal generated corresponding to the 120-degree energization method of FIGS. 1 and 2 will be described.
FIG. 3 shows a phase switching signal when the brushless DC motor is activated, and FIG. 4 shows a phase switching signal during steady driving.

3, FIG. 3 (a) is a timing chart showing the generation status of the rotor position setting signals Vpu, Vpv, Vpw and the phase switching signals Vu +, Vu−,..., Vw−, and FIG. ) Shows the generation pattern of the rotor position setting signal and the generation pattern (excitation pattern) of the phase switching signal in which the time chart is arranged in a table.
In FIG. 3, the electrical angle θ is updated by 60 degrees, and the updated period Ts of 60 degrees is updated as Ts1, TS2, Ts3,... Tsn. FIG. 3 shows only Ts1 to Ts6.
The period Ts with an electrical angle of 60 degrees is determined by the rotor position setting signals Vpu, Vpv, Vpw. That is, the cycle Ts1, Ts2, Ts3,... Tsn is generated at the timing of the rotor position setting signals Vpu, Vpv, Vpw every 60 degrees electrical angle. The phase switching signals Vu +, Vu−,..., Vw− are switched every cycle Ts1, TS2, Ts3,. To do. The generated pattern (excitation pattern) is as shown in FIG. 3B, and the same pattern is repeated every 360 degrees.

Next, FIG. 4 will be described.
FIG. 4A is a time chart showing the generation status of the magnetic pole detection signals Vsu, Vsv, Vsw and the phase switching signals Vu +, Vu−,..., Vw− generated based on the magnetic pole detection signals. 4 (b) shows the generation pattern of the magnetic pole detection signal and the generation pattern (excitation pattern) of the phase switching signal arranged in the table of the time chart.
In FIG. 4, the electrical angle θ and the period T are updated by 60 degrees in the same manner as in FIG.
When the brushless DC motor is switched from the starting state to the steady driving state, the period T of the electrical angle of 60 degrees is determined by the magnetic pole detection signals Vsu, Vsv, and Vsw. That is, cycles T1, T2, T3,... Tn (only T1 to T6 are shown) are generated at the timing of the magnetic pole detection signals Vsu, Vsv, and Vsw every 60 electrical angles. Generation patterns (excitation patterns) of the phase switching signals Vu +, Vu−,..., Vw− in the periods T1, T2, T3,... Tn are the same as those in FIG.
The periods T1, T2, T3,... Tn are substantially the same when the brushless DC motor 21 is rotating at a constant speed.

The structure of the drive device of the brushless DC motor which concerns on the Example of this invention is shown. A specific configuration example of the brushless DC motor, the inverter, and the like of FIG. 1 is shown. FIG. 1 and FIG. 2 show the generation status and generation pattern (excitation pattern) of the phase switching signal at startup. The generation situation and generation pattern of the magnetic pole detection signal and the generation situation and generation pattern (excitation pattern) of the phase switching signal at the time of steady driving in FIGS. The structure of the drive device of the conventional brushless DC motor is shown.

Explanation of symbols

21 Brushless DC motor 22 Phase switching unit (inverter)
23 DC power supply 24 Phase switching signal generation unit 25 PWM signal generation unit 31 Hall element 32 Magnetic pole detection signal generation unit 33 Electrical angle determination unit 34 Speed calculation unit 35 Switch drive unit 41 Speed setting unit 42 Speed deviation calculation unit 43 PID
44 Voltage setting unit 45 Period calculation unit 46 Rotor position setting unit

Claims (6)

In a brushless DC motor driving device comprising a permanent magnet rotor and a three-phase coil and having three Hall elements for detecting the magnetic poles of the rotor,
A magnetic pole detection signal generator for generating a magnetic pole detection signal from the outputs of the three Hall elements;
An electrical angle determination unit for determining an electrical angle from a magnetic pole detection signal;
A cycle calculating unit that calculates a cycle of an electrical angle of 60 degrees based on a speed command value at startup;
The rotor position setting signal corresponding to the updated electrical angle cycle is generated by updating the electrical angle by 60 degrees based on the electrical angle initial value based on the cycle of the cycle calculation unit and the electrical angle initial value of the electrical angle determination unit. Rotor position setting section,
A voltage setting unit for setting the voltage command value at startup,
Constant speed control unit,
A PWM signal generator that generates a PWM signal corresponding to a voltage command value at startup or a speed control signal of a steady-state speed controller;
A phase switching signal generator for generating a phase switching signal based on a rotor position setting signal or a magnetic pole detection signal in a steady state and a PWM signal;
A brushless DC motor driving device comprising a phase switching unit that is driven by a phase switching signal to supply an excitation current to a three-phase coil.   2. The brushless DC motor driving device according to claim 1, wherein the switch between the voltage command value at startup and the speed control signal, the switch between the rotor position setting signal and the magnetic pole detection signal at steady state, A drive device for a brushless DC motor, comprising a switch drive unit for driving the switch.   3. The brushless DC motor driving device according to claim 2, wherein the switch driving unit switches the switch to the voltage command value side and the rotor position setting signal side at the time of starting the brushless DC motor. A brushless DC motor drive device.   3. The brushless DC motor driving apparatus according to claim 2, wherein the switch driving unit moves the switch to the speed control signal side and the steady-state magnetic pole detection signal side when the rotational speed of the brushless DC motor becomes larger than a predetermined speed. A brushless DC motor drive device characterized by switching to   3. The brushless DC motor drive device according to claim 2, wherein the switch drive unit sets the switch to the voltage command value side and the rotor position setting at the start-up when the rotational speed of the brushless DC motor becomes lower than a predetermined speed. A brushless DC motor drive device characterized by switching to the signal side. In a driving method of a brushless DC motor comprising a permanent magnet rotor and a three-phase coil and having a Hall element for detecting a magnetic pole of the rotor,
The electrical angle initial value is determined by the magnetic pole detection signal generated by the outputs of the three Hall elements,
Calculate the period of electrical angle 60 degrees using the speed command value at startup,
A rotor position setting signal corresponding to the cycle of the electrical angle updated by updating the electrical angle by 60 degrees based on the electrical angle initial value based on the cycle and the electrical angle initial value is generated,
A phase switching signal is generated by the rotor position setting signal and the PWM signal corresponding to the voltage command value at the time of startup,
A driving method of a brushless DC motor, wherein a phase switching unit is driven by a phase switching signal to supply an exciting current to a three-phase coil.

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