JP4269920B2 - Brushless motor drive device - Google Patents

Description

  The present invention relates to a drive device that drives a brushless motor.

  Conventionally, a brushless motor having a rotor having a permanent magnet and a stator winding composed of a three-phase winding has been used in various devices, but this kind of brushless motor is opened by the rotation of the rotor. Some have position detection means for detecting the rotational position of the rotor by comparing the induced voltage (terminal voltage) generated in the stator winding of the phase (phase not energized) with the reference voltage. Also, as a starting method for starting the brushless motor, when the rotor is stopped, a plurality of energization patterns with different combinations of stator windings that are energized at the same time are used regardless of the detection result of the position detecting means. Brushless operation that starts the rotor by performing a synchronous operation that sequentially switches while gradually increasing the switching frequency, and sequentially switches the plurality of energization patterns based on the detection result of the position detection means when the switching frequency reaches a predetermined frequency. There is a method of switching to. Hereinafter, the starting method will be briefly described with reference to FIG.

  FIG. 8 shows two-phase stators that are energized simultaneously to a brushless motor having three-phase (U-phase, V-phase, and W-phase) stator windings 51 arranged outside the rotor 50. Six energization patterns P1 to P6 that are combinations of the windings 51, the state of magnetic poles (N pole, S pole) by the stator winding 51 immediately before commutation in each energization pattern P1 to P6, and the position of the rotor 50 Is shown. That is, in the energization pattern P1, the W phase and the U phase are energized and the W phase is the S pole and the U phase is the N pole. In the energization pattern P2, the U phase and the V phase are energized and the U phase is the N pole and the V phase is In the energization pattern P3, the V phase and the W phase are energized, the V phase is the S pole, and the W phase is the N pole. In the energization pattern P4, the W phase and the U phase are energized, and the W phase is the N pole. In the energization pattern P5, the U phase and the V phase are energized, the U phase is the S pole, and the V phase is the N pole. In the energization pattern P6, the V phase and the W phase are energized, and the V phase is the N pole. The W phase is the S pole. Here, FIG. 8 (a) shows a synchronous operation without load, FIG. 8 (b) shows a synchronous operation with load, and FIG. 8 (c) shows a brushless operation. The generated torque is zero during synchronous operation with no load, and the rotor 50 is delayed by the rotation angle (load angle) θL compared to when there is no load during synchronous operation with a load and during brushless operation. Commutation (switching between the energization patterns P1 to P6) is performed. In addition, as shown in FIG. 5C, commutation is performed based on the detection result of the position detection means during the brushless operation, and the load angle θL is always 60 degrees (electrical angle) regardless of the load state.

  On the other hand, FIG. 9 shows the state of torque, induced voltage, and detection result (position detection signal) of the position detection means before and after transition from synchronous operation to brushless operation. In FIG. 9, the torque (static torque) generated when the rotor 50 is rotated with the phase to be energized fixed is a dotted line, the torque generated by the actual energization is the solid line, and the rotor 50 is The induced voltage generated in the stator winding 51 when rotated is indicated by a dotted line, and the induced voltage generated in the open-phase stator winding 51 is indicated by a solid line. Further, the position detecting means detects the position of the rotor 50 at the timing when the induced voltage (solid line) generated in the open-phase stator winding 51 crosses zero.

  When there is no load, the load angle θL is zero because there is no load during synchronous operation as shown in FIG. 9A, and the induced voltage of the open phase (U phase) is zero crossed when shifting from synchronous operation to brushless operation. Without being able to detect the position of the rotor 50 by the position detecting means. On the other hand, when there is a load, for example, when the load angle θL is 30 degrees, the phase of the torque is advanced by 30 degrees with respect to the electrical angle as shown in FIG. Immediately after, the induced voltage of the open phase (V phase) is zero-crossed, and the position of the rotor 50 can be detected. At this time, the torque change ΔT when shifting from the synchronous operation to the brushless operation is about 50% of the maximum torque. Further, when the load angle θL is 60 degrees, as shown in FIG. 9C, the torque phase is advanced by 60 degrees with respect to the electrical angle, so the operation shifts from the synchronous operation to the brushless operation and the electrical angle is 30 degrees. After proceeding (after the rotor 50 rotates), the induced voltage of the open phase (V phase) crosses zero, and the position of the rotor 50 can be detected.

  As described above, when there is no load at the time of synchronous operation, the rotor cannot be commutated because the position detection means cannot detect the position of the rotor at the time of transition from synchronous operation to brushless operation, and the rotation of the rotor 50 is stopped. However, Patent Literature 1 and Patent Literature 2 disclose a driving device that solves this problem.

  First, in the drive device disclosed in Patent Document 1, after starting the rotor by synchronous operation, the energization pattern is skipped when shifting from synchronous operation to brushless operation, and before and after the transition from synchronous operation to brushless operation. FIG. 10 shows the state of the torque, induced voltage, and position detection signal. In FIG. 10, the static torque is a dotted line, the torque generated by actual energization is the solid line, the induced voltage generated in the stator winding when the rotor is rotated is the dotted line, and the open-phase stator winding The induced voltages generated in the lines are indicated by solid lines.

  Thus, even in the absence of a load, as shown in FIG. 10A, after the transition from the synchronous operation to the brushless operation and the electrical angle advances by 30 degrees, the induced voltage in the open phase (V phase) crosses zero. The position of the rotor can be detected. At this time, the torque change ΔT when shifting from the synchronous operation to the brushless operation is about 87% of the maximum torque. Further, when there is a load, for example, when the load angle θL is 30 degrees, the phase of torque is advanced by 30 degrees with respect to the electrical angle as shown in FIG. When the electrical angle advances by 60 degrees and the electrical angle advances by 60 degrees, the induced voltage of the open phase (W phase) is zero-crossed, and the rotor position can be detected. Similarly, when the load angle θL is 60 degrees, as shown in FIG. 10C, the torque phase is advanced by 60 degrees with respect to the electrical angle, so that the operation shifts from synchronous operation to brushless operation and the electrical angle is 90 degrees. After proceeding, the induced voltage of the open phase (W phase) is zero-crossed and the rotor position can be detected. At this time, the torque change ΔT when shifting from the synchronous operation to the brushless operation is about 87% of the maximum torque.

  As described above, in the drive device disclosed in Patent Document 1, the energization pattern is skipped when shifting from the synchronous operation to the brushless operation. Therefore, the induced voltage of the open phase can be detected after the shift to the brushless operation. It is possible to reliably detect the position of the first rotor after completion of the synchronous operation.

On the other hand, the drive device disclosed in Patent Document 2 increases the load angle by changing the switching frequency (commutation frequency) of the energization pattern or the increase rate of the voltage applied to the stator winding during synchronous operation. In the same way as the driving device disclosed in Patent Document 1, it is possible to detect the induced voltage in the open phase after the transition to the brushless operation, and to perform the first rotation after the end of the synchronous operation. The child position can be reliably detected.
Japanese Patent No. 3326256 JP 2001-178184 A

  However, the above-described driving devices disclosed in Patent Document 1 and Patent Document 2 have the following problems. That is, in the drive device disclosed in Patent Document 1, since the energization pattern is skipped during the transition from the synchronous operation to the brushless operation, the torque before and after the transition changes discontinuously, and the brushless motor vibrates. There was a problem of rapid acceleration. On the other hand, in the drive device disclosed in Patent Document 2, since it takes time to change the increase rate of the commutation frequency or the applied voltage, the brushless motor is started in a short time (for example, several tens of milliseconds) and the brushless motor is started from the synchronous operation. There was a problem that it was not possible to shift to driving.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a brushless motor that can shift from synchronous operation to brushless operation in a short time and has less torque fluctuation at the time of transition from synchronous operation to brushless operation. It is to provide a driving device.

In order to achieve the above object, a first aspect of the present invention provides a driving apparatus for driving a brushless motor having a rotor having a permanent magnet and a stator winding composed of a three-phase winding. The position detection means for detecting the rotational position of the rotor by comparing the terminal voltage of the wire with the reference voltage, and switching the energization state to each phase of the stator winding by switching the DC voltage supplied from the power source The energization switching means, the control means for controlling the energization switching means to sequentially switch a plurality of energization patterns with different combinations of stator windings that are energized at the same time, and the power supply is supplied to the brushless motor via the energization switching means. and a current detecting means for detecting a current that, the control means includes a sequentially switched synchronous operation control of the plurality of energization patterns regardless of the detection result of the position detection means, position detection The brushless operation control for sequentially switching the plurality of energization patterns based on the detection result of the stage is performed, and the synchronous operation control is performed while gradually increasing the switching frequency of the plurality of energization patterns when the rotor is stopped. When the rotor is started, and after the switching frequency reaches the predetermined frequency, the energization pattern is switched once at a frequency larger than the predetermined frequency , and then the brushless operation control is performed, and at the time of transition from the synchronous operation control to the brushless operation control. The frequency higher than the predetermined frequency is changed according to the level of the current detected by the current detection means .

According to the present invention, it is possible to make a transition from synchronous operation to brushless operation in a short time, and to reduce torque fluctuation at the time of transition from synchronous operation to brushless operation. Moreover, for example, if the current detected by the current detection means is small, the rate of increasing the frequency is increased, and if the current is large, the rate is decreased, so that the brushless operation is not affected by the size of the load. Motor vibration and sudden acceleration can be prevented.

  According to a second aspect of the present invention, in the first aspect of the invention, the control means switches the energization pattern once at a frequency that is greater than one time and less than six times the predetermined frequency when shifting from synchronous operation control to brushless operation control. It is characterized by.

  According to the present invention, it is possible to reduce the torque fluctuation at the time of shifting to the brushless operation corresponding to the load state at the time of the synchronous operation, and it is possible to suppress the vibration and sudden acceleration of the brushless motor.

  According to a third aspect of the invention, in the first or second aspect of the invention, the control means fixes the switching frequency to the predetermined frequency for a predetermined time after the predetermined frequency is reached and before the transition from the synchronous operation control to the brushless operation control. And synchronous operation control.

  According to the present invention, it is possible to eliminate the influence on the load due to the inertia of an object that transmits the rotational force of the brushless motor to the load, and it is possible to suppress vibration and sudden acceleration during the transition to the brushless operation.

According to the present invention, there is an effect that it is possible to shift from synchronous operation to brushless operation in a short time and to reduce torque fluctuation at the time of transition from synchronous operation to brushless operation. Also, for example, if the current detected by the current detection means is small, the rate of increasing the frequency is increased, and if the current is large, the rate is decreased, so that the brushless operation is not affected by the size of the load. There is also an effect that vibration and sudden acceleration of the motor can be prevented.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, the drive device according to the present invention is suitable for various electric devices (for example, electric tools) using a brushless motor as a power source.

Here, before describing the embodiment of the present invention, a basic example having the same basic configuration as the embodiment of the present invention will be described.
As shown in FIG. 1A, the brushless motor M has a rotor 50 having a permanent magnet and a stator winding 51 composed of a three-phase winding, and a U-phase, V-phase, and W-phase stator. The winding 51 is star-connected and connected to the inverter circuit 1 of the driving device A. The inverter circuit 1 has a series circuit in which two switching elements 2a and 2d, 2b and 2e, 2c and 2f, each having a diode connected in antiparallel, are connected in parallel to both ends of a DC power supply E. And a drive unit 3 for switching the six switching elements 2a to 2f, and the middle point of each series circuit in the switching element group (two switching elements 2a, 2b,. The three stator windings 51 of the brushless motor M are connected to the connection point). That is, commutation is performed by the drive unit 3 individually switching the six switching elements 2a to 2f based on a command given from the control unit 4. Further, the position detection unit 5 compares the voltages between the terminals of the U phase and the V phase, the V phase and the W phase, and the W phase and the U phase in the stator winding 51 with the reference voltage, thereby generating a zero cross of the induced voltage (rotor 50 position) is detected and a position detection signal is output to the control unit 4.

  The control unit 4 has a configuration shown in FIG. The speed setting circuit 41 obtains a command speed corresponding to the operation amount of the operation unit B (for example, the resistance value of the variable resistor) and outputs it to the speed control circuit 42. The speed detection circuit 43 calculates the rotation speed of the rotor 50 based on the time interval at which the position detection signal is output from the position detection unit 5 and outputs it to the speed control circuit 42. The speed control circuit 42 is a stator that is determined according to the difference between the rotation speed and the command speed so that the rotation speed of the rotor 50 input from the speed detection circuit 43 matches the command speed input from the speed setting circuit 41. The command value of the voltage applied to the winding 51 is calculated and output to the brushless energization pattern circuit 44. The brushless energization pattern circuit 44 is necessary for applying to the stator winding 51 an applied voltage determined by a command value input from the speed control circuit 42 for each energization pattern of the stator winding 51 described in the prior art. The condition, that is, the on-duty ratio of the drive pulse output for switching each switching element in the drive unit 3 is obtained, and the command value of the energization pattern including the on-duty ratio is set to a predetermined value from the input time of the position detection signal. It outputs to the switching circuit 45 after an electrical angle.

  The command speed is also output to the synchronous control circuit 46. When the synchronous control circuit 46 confirms that the command speed has changed from zero, it outputs a control signal for switching to synchronous operation to the switching circuit 45, and The switching frequency (commutation frequency) f for switching the energization pattern is output to the synchronous energization pattern circuit 47 while gradually increasing from the initial value f0 to the predetermined value fs. When the commutation frequency f reaches the predetermined value fs, the synchronous operation is started. A control signal for instructing the shift to the brushless operation is output to the switching circuit 45. The synchronous energization pattern circuit 47 obtains an on-duty ratio of a drive pulse necessary for obtaining an applied voltage corresponding to a speed command value for each energization pattern of the stator winding 51 and energization including the on-duty ratio. The pattern command value is output to the switching circuit 45 at a timing determined by the commutation frequency f. The switching circuit 45 outputs the command value input from the synchronous energization pattern circuit 47 to the drive unit 3 of the inverter circuit 1 while being switched to the synchronous operation by the control signal, and is switched to the brushless operation by the control signal. During this time, the command value input from the brushless energization pattern circuit 44 is output to the drive unit 3 of the inverter circuit 1. The drive unit 3 switches the energization pattern based on the command value input from the control unit 4 and changes the on-duty ratio of the drive pulse to adjust the applied voltage to the stator winding 51, so-called PWM ( (Pulse width modulation) control is performed.

  Next, with reference to the flowchart of FIG. 2 and the timing chart of FIG. 3, the operation at the start of the brushless motor will be described in more detail.

  First, in the synchronous control circuit 46, when the activation is confirmed by the command speed changing from zero as described above, the commutation frequency f is set to the initial value f0, and the elapsed time t of the synchronous operation is set to the initial value (zero). And the control signal is set to L level to switch to synchronous operation (step 1), and the commutation frequency f is increased from the initial value f0 to the predetermined value fs at a constant increase rate (steps 2 and 3). . Further, after the commutation frequency f reaches the predetermined value fs, the synchronous control circuit 46 fixes the commutation frequency f to fs until the elapsed time t reaches the predetermined time t2, and continues the synchronous operation (step 4). When the elapsed time t reaches the predetermined time t2, the commutation frequency f is increased to a frequency fs × a (a = 2 to 6) larger than the predetermined value fs (step 5), and the increased commutation frequency f ( = Fs × a) (switch the energization pattern once) and then set the control signal to H level to shift from synchronous operation to brushless operation (steps 6 and 7). Note that the time ts required to cause current to flow once at the increased commutation frequency f (= fs × a) is approximately 1 / (fs × a).

  Here, the torque, the induced voltage before and after the transition from the synchronous operation to the brushless operation, when the magnification a for increasing the commutation frequency f before the transition from the synchronous operation to the brushless operation is 2 times or 6 times, The results of examining the state of the position detection signal are shown in FIGS. 4 and 5, respectively. In each figure, the static torque is a dotted line, the torque generated by actual energization is the solid line, the induced voltage generated in the stator winding 51 when the rotor 50 is rotated is the dotted line, and the open phase is fixed. The induced voltage generated in the child winding 51 is indicated by a solid line.

  First, the case where the magnification a is set to 2 will be described. When synchronous operation is performed with no load (the load angle θL is zero), as shown in FIG. 4A, ts (= 1 / (fs × 2)) When switching to an energization pattern for energizing the W-phase and U-phase (commutation) only during that time, the rotor 50 rotates only 30 degrees (= 60 degrees / a) in electrical angle, so the load angle θL is 30 degrees. Then, when shifting to brushless operation, it can be seen that the position of the rotor 50 can be detected from the zero cross of the induced voltage of the V phase immediately after the transition. At this time, the torque change ΔT when shifting from the synchronous operation to the brushless operation is about 50% of the maximum torque. Further, in the case of synchronous operation with the load angle θL being 30 degrees, the W phase and the U phase are energized only for ts from the energization pattern for energizing the W phase and the V phase as shown in FIG. 4B. By switching (commutating) to the energization pattern, the load angle θL becomes 60 degrees, and after that, when transitioning to brushless operation, the transition is made to brushless operation and the electrical angle advances by 30 degrees, and then rotation starts from the zero cross of the W-phase induced voltage. It can be seen that the position of the child 50 can be detected. Also at this time, the torque change ΔT when shifting from the synchronous operation to the brushless operation is about 50% of the maximum torque. Further, when the synchronous operation is performed with the load angle θL being 60 degrees, the W phase and the U phase are energized for ts from the energization pattern for energizing the W phase and the V phase as shown in FIG. By switching to the energization pattern (commutation), the load angle θL becomes 90 degrees, and then when switching to brushless operation, the operation proceeds to brushless operation and the electrical angle advances by 60 degrees, and then rotates from the zero cross of the induced voltage of the W phase. It can be seen that the position of the child 50 can be detected. Also at this time, the torque change ΔT when shifting from the synchronous operation to the brushless operation is about 50% of the maximum torque.

  On the other hand, the case where the magnification a is 6 will be described. In the case of synchronous operation with no load (the load angle θL is zero), as shown in FIG. 5 (a), ts (= 1 / (fs × 6)) When switching to an energization pattern for energizing the W-phase and U-phase (commutation) only during this period, the rotor 50 rotates only 10 degrees (= 60 degrees / a) in electrical angle, so the load angle θL is 50 degrees. Then, when the operation proceeds to the brushless operation, it can be seen that the position of the rotor 50 can be detected from the zero cross of the induced voltage of the V phase after the operation proceeds to the brushless operation and the electrical angle advances 20 degrees. At this time, the torque change ΔT when shifting from the synchronous operation to the brushless operation is about 17% of the maximum torque. In addition, when synchronous operation is performed with the load angle θL being 30 degrees, the W phase and the U phase are energized only for ts from the energization pattern for energizing the W phase and the V phase as shown in FIG. 5B. By switching (commutating) to the energization pattern, the load angle θL becomes 80 degrees, and after that, when shifting to the brushless operation, the operation proceeds to the brushless operation and the electrical angle advances by 50 degrees, and then the rotation starts from the zero cross of the induced voltage of the W phase. It can be seen that the position of the child 50 can be detected. At this time, the torque change ΔT when shifting from the synchronous operation to the brushless operation is about 34% of the maximum torque. Further, when the synchronous operation is performed with the load angle θL being 60 degrees, the W phase and the U phase are energized only for ts from the energization pattern for energizing the W phase and the V phase as shown in FIG. 5C. By switching (commutating) to the energization pattern, the load angle θL becomes 110 degrees, and after that, when shifting to the brushless operation, the operation proceeds to the brushless operation and the electrical angle advances by 80 degrees and then rotates from the zero cross of the induced voltage of the W phase. It can be seen that the position of the child 50 can be detected. At this time, the torque change ΔT when shifting from the synchronous operation to the brushless operation is about 76% of the maximum torque.

Thus, in this basic example , after performing the synchronous operation while gradually increasing the commutation frequency f from the initial value f0 to the predetermined value fs, the commutation frequency f is set to a frequency fs × a larger than the predetermined value fs. By switching to a brushless operation after switching the energization pattern once (commutating), the induced voltage in the open phase can be reliably detected after the transition to the brushless operation, and the first rotation after the end of the synchronous operation Not only can the position of the child 50 be detected reliably, but torque fluctuation (torque change ΔT) when shifting from synchronous operation to brushless operation can be reduced as compared with that described in Patent Document 1. Moreover, as disclosed in Patent Document 2, the brush angle is increased after increasing the load angle by changing the commutation frequency during synchronous operation or the rate of increase of the voltage applied to the stator winding. There is an advantage that the brushless motor can be started in a short time (for example, several tens of milliseconds) and shifted from the synchronous operation to the brushless operation, compared with the case where the operation is shifted to the service operation. Further, according to the magnification a (= 2 to 6) that increases the commutation frequency f when shifting from the synchronous operation to the brushless operation, the increase amount of the load angle θL when shifting from the synchronous operation to the brushless operation is 10 degrees. If the adjustment is made within a range from 50 degrees to 50 degrees, it is possible to reduce the torque fluctuation ΔT corresponding to the load state (load angle θL) during the synchronous operation, and it is possible to suppress the vibration and sudden acceleration of the brushless motor M. It is. Therefore, it is desirable to increase the magnification a when the load during the synchronous operation is small, and decrease the magnification a when the load is large.

In this basic example , after the commutation frequency f reaches the predetermined value fs, the commutation frequency f is fixed to the predetermined value fs for a predetermined time (t = t2 to t3) before the transition from the synchronous operation to the brushless operation. Since the synchronous operation is performed, the influence on the load due to the inertia of the rotating object (for example, the bit in the electric tool) can be eliminated, and the vibration and sudden acceleration at the time of the transition to the brushless operation by the rotating object can be suppressed. There are advantages.

(Embodiment )
As shown in FIG. 6, the present embodiment includes a current detection circuit 6 that detects a current supplied from the DC power source E to the brushless motor M via the inverter circuit 1, and the control unit 4 performs the brushless operation from the synchronous operation control. It is characterized in that the magnification a that makes the commutation frequency f larger than the predetermined value fs is changed according to the level of the current detected by the current detection circuit 6 at the time of transition to control. However, since other configurations and basic operations are the same as those in the basic example , common constituent elements are denoted by the same reference numerals and description thereof is omitted.

  The current detection circuit 6 outputs a detection signal having a voltage level corresponding to the magnitude of the current supplied from the DC power supply E to the brushless motor M to the synchronization control circuit 46 of the control unit 4 by using, for example, a voltage drop of a resistor. (See FIG. 6B). Then, after the commutation frequency f reaches the predetermined value fs, the synchronous control circuit 46 fixes the commutation frequency f to fs until the elapsed time t reaches the predetermined time t2, and continues the synchronous operation. When the predetermined time t2 is reached, the commutation frequency f is increased to a frequency fs × a (a = 2 to 6) larger than the predetermined value fs. At this time, based on the detection signal input from the current detection circuit 6. As shown in FIG. 7, the magnification a is determined in proportion to the magnitude of the current I supplied from the DC power source E to the brushless motor M (however, the proportionality constant is a negative value). That is, in the synchronous control circuit 46, the magnification a is increased when the current I is small, and the magnification a is decreased when the current I is large, so that the magnification a is appropriately set according to the size of the load (the magnitude of the current I). Since the size is adjusted, vibration and sudden acceleration of the brushless motor M during the transition to the brushless operation can be prevented without being affected by the size of the load.

The basic example of this invention is shown, (a) is a whole schematic block diagram, (b) is a block diagram of a control part. It is a flowchart for operation | movement description same as the above. It is a timing chart for operation | movement description same as the above. (A)-(c) is a wave form diagram for operation explanation same as the above. (A)-(c) is a wave form diagram for operation explanation same as the above. 1 shows an embodiment of the present invention , (a) is a schematic configuration diagram of the whole, (b) is a block diagram of a control unit. It is operation | movement explanatory drawing same as the above. It is explanatory drawing explaining the drive principle of a brushless motor. (A)-(c) is a wave form diagram for operation explanation same as the above. (A)-(c) is a wave form diagram for operation explanation same as the above.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inverter circuit 4 Control part 45 Switching circuit 46 Synchronous control circuit 47 Synchronous energization pattern circuit

Claims (3)

In a driving device for driving a brushless motor having a rotor having a permanent magnet and a stator winding composed of a three-phase winding, the terminal voltage of the stator winding of the open phase is compared with a reference voltage to thereby compare the rotor Position detection means for detecting the rotational position, energization switching means for switching the energization state of each phase of the stator winding by switching the DC voltage supplied from the power source, and energization switching means for controlling the energization switching means simultaneously. A control means for sequentially switching a plurality of energization patterns with different combinations of stator windings, and a current detection means for detecting a current supplied from the power source to the brushless motor via the energization switching means. Synchronous operation control for sequentially switching the plurality of energization patterns irrespective of the detection result of the position detection means, and the plurality of energization patterns based on the detection result of the position detection means When the rotor is in a stopped state, the rotor is started by performing synchronous operation control while gradually increasing the switching frequency of a plurality of energization patterns, and the switching frequency is a predetermined frequency. After switching to the brushless operation control after switching the energization pattern once at a frequency higher than the predetermined frequency after reaching the frequency, the current detection means sets the frequency to be larger than the predetermined frequency when shifting from the synchronous operation control to the brushless operation control. The brushless motor drive device is characterized in that it is changed according to the level of the current detected by the motor.   2. The brushless motor drive device according to claim 1, wherein the control means switches the energization pattern once at a frequency greater than 1 and less than 6 times the predetermined frequency when shifting from the synchronous operation control to the brushless operation control. . The control means performs the synchronous operation control by fixing the switching frequency to the predetermined frequency for a predetermined time after shifting to the brushless operation control from the synchronous operation control after reaching the predetermined frequency. The brushless motor drive device described .

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