JPH10337080A - Control method for brushless motor, and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable optimum rotation control by detecting the position of a rotor accurately, regardless of the dispersion of the circuit (parts) constant of the controller of a brushless motor. SOLUTION: DC power is applied to a brushless motor 4, being switched with the plural transistors of an inverter part 3, whereby the brushless motor 4 is controlled for its rotation. At this time, a position detecting circuit 10 composes terminal voltages with a resistance circuit 5a so as to get neutral point voltage on one side, and generates the first to third reference voltages with a reference voltage generating circuit 10a, and also, compares the neutral point voltage with the first to third reference voltages with first to third comparison circuits 10b, 10b, 10c, and 10d, and outputs the position detection signals A and B of comparison results to a control circuit 11 on the other. The control circuit 11 detects the position of the rotor by the input position detection signal A, B, and C, and computes the interval between its positional detections, and selects the positional detection signal getting the positional detection interval capable of rotation control with the best balance out of these positional detection intervals, and detects the position of the rotor by the selected positional detection signal at positional detection operation, and switches the current application to the armature winding of a brushless motor 4, based on this positional detection.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotation control technique for a sensorless DC brushless motor (hereinafter referred to as a brushless motor), and more particularly, to detecting an optimum rotor position and enabling the most balanced rotation control. And a device for controlling a brushless motor.

[0002]

2. Description of the Related Art In this brushless motor, the position of a rotor is detected, and the energization of an armature winding current of the brushless motor is switched based on the detected position. Therefore, for example, as shown in FIG. 7, the control device of the brushless motor converts the commercial power supply 1 to DC by the AC / DC conversion unit 2, and switches the converted DC power supply by the inverter unit 3 to drive the brushless motor 4. Supply to the secondary winding.

In order to detect the position of the rotor of the brushless motor 4, a position detecting circuit 5 includes armature windings U,
The terminal voltages of V and W (three voltage waveforms having a phase shift of 120 degrees) are compared with the reference voltage k, and the result of the comparison is used as a position detection signal (including the intersection of the induced voltage and the reference voltage). (Computer) 6. The position detecting circuit 5 includes a resistor circuit 5a for synthesizing the terminal voltages of the armature windings U, V, and W to artificially obtain a neutral point voltage of the brushless motor 4, and a reference circuit for generating a reference voltage. It comprises a voltage generating circuit 5b and a comparing circuit 5c for comparing the neutral point voltage (induced voltage) with a reference voltage.

More specifically, a resistor circuit 5a star-connects three resistors R1, R2, and R3, grounds the connection point via a resistor R4, and connects the connection point (see point A in FIG. 7). A neutral point voltage obtained by combining the terminal voltages is obtained (FIG. 8).
(A)). The reference voltage generation circuit 5b divides the power supply of the control circuit by the resistors R5 and R6 to generate a reference voltage k (see FIG. 8A). In this case, the reference voltage k is obtained by dividing the power supply of the inverter unit 3 by the resistors R5 and R6 so that the reference voltage k becomes の of the neutral point voltage. The comparison circuit 5c is a comparator that inputs a neutral point voltage to an inverting input terminal and inputs a reference voltage to a non-inverting input terminal, and outputs the comparison result as a position detection signal (see FIG. 8B).

[0005] The control circuit 6 uses the edge (rising edge, falling edge) of the position detection signal from the position detection circuit 5 to intersect the neutral point voltage and the reference voltage (see the point in FIG. 8A; Intersection with the reference voltage)
The energization switching timing is calculated based on this position detection, and the switching elements (transistors) Ua, V of the inverter unit 3 are calculated based on the calculated energization switching timing.
A drive signal for driving a, Wa, X, Y, and Z is output to the drive circuit 7, and the energization of the armature winding of the brushless motor 4 is switched.

In this case, when the neutral point voltage (induced voltage) is rising, the first rising edge of the position detection signal after the energization switching is used as the rotor position detection (FIG. 8).
When the neutral point voltage (induced voltage) is falling, the first falling edge of the position detection signal after energization switching is used as the rotor position detection (see FIG. 8B). Down arrow). By detecting the position of the rotor in this manner, the energization of the armature windings U, V, W can be appropriately switched, and the rotation of the brushless motor 4 can be appropriately controlled.

[0007]

However, in the above-described method of controlling a brushless motor, the position detection of the rotor may not be optimal due to variations in the circuit (component) constants of the control device. The position detection differs for each device due to the error of the resistance that constitutes the above. Particularly, when the rotational speed of the brushless motor is high, the step-out may occur depending on the difference in the position detection.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to be able to accurately detect the position of a rotor irrespective of variations in circuit (component) constants. It is an object of the present invention to provide a brushless motor control method and device capable of performing the most balanced rotation control without stepping out of the motor and reducing the cost.

[0009]

In order to achieve the above object, the present invention obtains a neutral point voltage obtained by synthesizing terminal voltages of armature windings of a brushless motor, and obtains a neutral point voltage and a reference voltage. A brushless motor that detects the position of the rotor of the brushless motor based on the comparison result, switches energization of the armature windings of the brushless motor based on the position detection, and controls the rotation of the brushless motor. The control method, comparing the neutral point voltage and a plurality of different reference voltages to obtain a plurality of position detection signals, while obtaining a position detection interval of the rotor by the plurality of position detection signals, Among the position detection intervals, the position of the rotor is detected by a position detection signal that obtains the position detection interval that enables the most balanced rotation control, and the brush is detected based on the position detection. It is characterized in that to obtain the energization switching timing of the armature winding of the Resumota.

According to the present invention, a neutral point voltage obtained by synthesizing terminal voltages of armature windings of a brushless motor is obtained, and the neutral point voltage is compared with a reference voltage. A brushless motor control device that detects the position of the brushless motor, switches the energization of the armature winding of the brushless motor based on the position detection, and controls the rotation of the brushless motor. Reference voltage generating means for generating different reference voltages, comparing means for comparing the neutral point voltage with the plurality of different reference voltages, and obtaining a position detection interval of the rotor based on a position detection signal of the comparison result. At the same time, a position detection signal that has obtained a position detection interval that enables the most balanced rotation control among these position detection intervals is selected, and the selected position detection signal is Ri detects the position of the rotor, is characterized in that it comprises a control means based on switching the energization of the armature winding of the brushless motor the position detection.

In this case, it is preferable that the reference voltage generating means connects a plurality of resistors in series, and divides a power supply used for the rotation control by the plurality of resistors to generate the plurality of reference voltages.

According to the present invention, a neutral point voltage obtained by synthesizing a terminal voltage of an armature winding of a brushless motor is obtained, and the neutral point voltage is compared with a reference voltage. A brushless motor control device that detects a position, switches energization of an armature winding of the brushless motor based on the position detection, and controls rotation of the brushless motor. A reference voltage generating means for generating a third reference voltage and switching between the second reference voltage and the third reference voltage, and comparing the neutral point voltage with the first reference voltage; Comparing means for comparing the neutral point voltage with the switched second reference voltage, and comparing the neutral point voltage with the switched third reference voltage;
The position detection signal of the rotor is obtained from the position detection signal of the comparison result obtained by the comparison means, and the position detection signal that obtains the position detection interval enabling the most balanced rotation control among these position detection intervals. Control means for detecting the position of the rotor based on the selected position detection signal, and switching the energization of the armature winding of the brushless motor based on the position detection. And

In this case, the reference voltage generating means connects three resistors in series, and connects one end of the three resistors to a grounded resistor and a switch connected in series to the same resistor. Preferably, the first and second reference voltages are generated when the switch is turned off and the switch is turned off, and the first and third reference voltages are generated when the switch is turned on.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to FIGS. FIG.
7, the same parts as those in FIG. 7 are denoted by the same reference numerals, and redundant description is omitted. According to the brushless motor control method and device of the present invention, if a plurality of reference voltages to be compared with the neutral point voltage are prepared, the possibility of more optimal rotor position detection is increased, and the reference voltage generation circuit It is noted that it is only necessary to increase the number of comparators as the resistance increases, and the cost of the position detection circuit does not increase so much.

For this purpose, as shown in FIG. 1, a position detecting circuit 10 of a control device to which the brushless motor control method of the present invention is applied is replaced with a resistor circuit 5a and a reference voltage generating circuit 5b which are the same as those in FIG. And resistors R7, R8, R9, R1
0 is connected in series, a power supply (output voltage of the AC / DC converter 2) of the control circuit is divided, and a reference voltage generating circuit 10a for generating first to third reference voltages, and the resistor circuit 5a. A first comparison circuit 10b that compares the obtained neutral point voltage with the first reference voltage and outputs a position detection signal A to the control circuit 11, and compares the neutral point voltage and the second reference voltage with each other. A second comparison circuit 10c for comparing and outputting the position detection signal B to the control circuit 11, and a third comparison circuit for comparing the neutral point voltage with the third reference voltage and outputting the position detection signal C to the control circuit 11.
Is provided.

The reference generating circuit 10a generates first to third reference voltages (different reference voltages) k1, k2, and k3, and the first to third reference voltages k1, k2, and k3 are set to neutral point voltages as much as possible. Of each resistor R7, R8, R
9. Determine the value of R10.

The control circuit 11 has input position detection signals A,
Based on B and C, the position of the rotor of the brushless motor 4 is detected, and the position detection intervals are calculated.
Among these position detection intervals, a position detection signal that obtains a position detection interval capable of performing the most balanced rotation control is selected. The control circuit 11 has the function of the control circuit 6 shown in FIG. Therefore, prior to the position detection operation of the brushless motor 4, the above-described processing is executed to select an optimum position detection signal. During the position detection operation, the position of the rotor is detected by the selected position detection signal. Based on the timing, the switching elements Ua, Va, Wa, X, Y, and Z of the inverter unit 3 are controlled, and the energization of the armature windings U, V, and W of the brushless motor 4 is switched.

Next, the operation of the position detection circuit 10 and the control circuit 11 will be described with reference to FIG. Note that FIG.
(A) corresponds to FIG. 8 (a), and is a waveform of the neutral point voltage obtained by the resistance circuit 5a. First, it is assumed that the control circuit 11 starts the brushless motor 4, executes a synchronous operation process, rotates the brushless motor 4, and then switches to the position detection operation.

When switching to the position detection operation, an optimum position detection signal is selected from the position detection signals A, B, and C from the position detection circuit 10. In this case, the first comparison circuit 10b is a comparator, and its non-inverting input terminal receives the neutral point voltage, and its inverting input terminal receives the first reference voltage k1. Similarly, the neutral point voltage is input to the non-inverting input terminal of the second comparing circuit 10c, the second reference voltage k2 is input to the inverting input terminal, and the non-inverting input terminal of the third comparing circuit 10d. , And a third reference voltage k3 is input to the inverting input terminal. Therefore, the first
The output of the comparison circuit 10b of FIG.
The waveform shown in (b) is obtained, and the output (position detection signal B) of the second comparison circuit 10c has the shape shown in FIG.
The output (position detection signal C) of the comparison circuit 10d has the form shown in FIG.

The control circuit 11 uses the three position detection signals A, B, and C to detect the position of the rotor (see FIG. 2).
(Intervals of arrows shown in (b), (c), and (d)) are sequentially calculated, and a position detection signal having an optimum position detection interval is selected from these position detection intervals. When selecting a position detection interval capable of performing the most balanced rotation control among the position detection intervals, for example, a position detection interval closest to an empirically obtained value is selected, and ideal energization of the brushless motor 4 is performed. The one closest to the position detection interval that contributes to switching is selected. That is, even if there are variations in circuit (component) constants, it is possible to select a position detection signal that obtains an optimum position detection interval from a plurality of different reference voltages (first to third reference voltages).

When the operation of the brushless motor 4 is shifted to the position detection operation, the position of the rotor is detected by the position detection signal having the selected position detection interval, and the brushless motor 4 is detected based on the position detection timing. 4 switches the energization of the armature winding. Therefore, the circuit (component)
Even if the constants vary, the rotation control of the brushless motor 4 can be optimally performed, and even if the rotation speed increases, the rotation control is performed based on the optimum position detection signal. The motor 4 does not lose synchronism.

FIG. 3 is a block diagram of a control device for explaining a modified embodiment of the present invention. In the figure, the same parts as those in FIG. The brushless motor control and device according to the present invention reduces the number of comparison circuits (comparators) in the position detection circuit,
Reduce costs.

Therefore, as shown in FIG. 3, the position detection circuit 12 generates the same resistance circuit 5a as in FIG. 1, a first reference voltage k1, and generates a second reference voltage k2 and a third reference voltage k1. a reference voltage generating circuit 12a which is generated by switching between k3 and k3.
And a fourth comparison circuit 12b for comparing the neutral point voltage obtained by the resistance circuit 5a with the first reference voltage k1, a neutral point voltage and a second reference voltage k2, and A fifth comparison circuit that compares the neutral point voltage with the third reference voltage k3, and outputs the position detection signals D, E, and F of the respective comparison results to the control circuit 1
Output to 3.

The reference voltage generating circuit 12a includes a resistor R11,
When R12 and R13 are connected in series, a resistor R14 having one end grounded and a resistor R14 and a switch means (transistor) Tr connected in series to the resistor R14 are connected in parallel, and the transistor Tr is turned on. Resistor R1
3 and the resistor R14 are connected in parallel.

Therefore, when the transistor Tr is turned off, the output voltage of the AC / DC converter 2 is changed to the resistances R11 and R11.
12, R13 to divide the first reference voltage k1 and the second
When the transistor Tr is turned on, the output voltage of the AC / DC converter 2 is divided by the resistors R11, R12, R13, and R14 to generate the first reference voltage k2. k1 and a third reference voltage k3 are generated (see FIG. 5A). In this case, the first reference voltage k1 generated when the transistor Tr is turned on and off is slightly different, but the third reference voltage k3 is at a level lower than the second reference voltage k2. Further, the first to third reference voltages k
1, k2 and k3 need not be exactly the same as in the previous embodiment.

The control circuit (microcomputer) 13 has a function of outputting a control signal for turning on and off the transistor Tr to the position detection circuit 12 in addition to the function of the control circuit 11 shown in FIG.

Next, the operation of the position detection circuit 12 and the control circuit 13 will be described with reference to FIGS. FIGS. 4A and 5A correspond to FIG. 7A and show the waveform of the neutral point voltage obtained by the resistor circuit 5a.
First, the control circuit 13 starts the brushless motor 4, executes a synchronous operation process, rotates the brushless motor 4, and then switches to the position detection operation.

When the operation is switched to the position detection operation, a control signal for turning on and off the transistor Tr is output to the position detection circuit 12, and among the position detection signals D, E and F from the position detection circuit 10, Select the position detection signal. In this case, when the transistor Tr is turned off, the fourth
The output of the comparison circuit 12b of FIG.
The waveform shown in (b) is obtained, and the output (position detection signal E) of the fifth comparison circuit 12c is in the form shown in FIG. When the transistor Tr is turned on, the output (position detection signal D) of the fourth comparison circuit 12b has the form shown in FIG. 5B, and the output (position detection signal F) of the fifth comparison circuit 12c is FIG. 5C is obtained.

Therefore, the control circuit 13 controls the transistor T
The position detection interval of the rotor is determined by the position detection signals D and E in a state where r is turned off (the interval between the arrows shown in FIGS. 4B and 4C).
Is calculated, and then the position detection interval of the rotor is detected by the position detection signals D and F with the transistor Tr turned on (FIG. 5).
(B) and (c) are sequentially calculated, and a position detection signal having an optimum position detection interval is selected from these position detection intervals.

In the position detection operation of the brushless motor 4, the position of the rotor is detected by the position detection signal that has obtained the selected position detection interval, and the position of the brushless motor 4 is determined based on the position detection timing. Switch the energization of the armature winding. Therefore, as in the previous embodiment, the rotation control of the brushless motor 4 can be optimally performed even if the circuit (component) constants vary, and even if the rotation speed increases, the optimum position detection signal is output. Since the rotation control is performed on the basis, the brushless motor 4 does not lose synchronism. Further, although the resistor R14 and the transistor Tr are added, the number of the comparison circuits can be reduced by one, so that the cost of the position detection circuit 12 can be suppressed lower than in the previous embodiment.

FIG. 6 is a block diagram of a control device for explaining another modified embodiment which further advances the modified embodiment. In the figure, the same parts as those in FIG. In this case, the position detection circuit 14
Is the same resistance circuit 5a as in FIG. 1, a reference voltage generation circuit 14a that generates by switching the first reference voltage, the third reference voltage, and the third reference voltage, and the neutral point voltage obtained by the resistance circuit 5a. A sixth comparison circuit for comparing the first reference voltage, comparing the neutral point voltage with the second reference voltage, and further comparing the neutral point voltage with the third reference voltage; , And outputs the position detection signals G, H, and I of the comparison result to the control circuit 15.

The reference voltage generation circuit 12a includes a resistor R15,
R16 connected in series with one end grounded
In contrast, a resistor R17 and switch means (transistor) Tr1 connected in series to the resistor R17 are connected in parallel, and a resistor 18 and switch means (transistor) Tr2 connected in series to the resistor 18 are connected in parallel. I have. The resistance R16 and the resistances R17 and R18 are determined by the combination of the on and off states of the transistors Tr1 and Tr2.
Are connected in parallel in various combinations, and different reference voltages can be generated. For example, the transistors Tr1 and Tr2 are turned off to generate a first reference voltage, the transistor Tr1 is turned on, the transistor Tr2 is turned off to generate a second reference voltage, the transistor Tr1 is turned on, and the transistor Tr2 is turned on. And generating a third reference voltage.

The control circuit (microcomputer) 15 has a function of outputting a control signal for turning on and off the transistors Tr1 and Tr2 to the position detection circuit 12 in addition to the function of the control circuit 11 shown in FIG. Further, the operation of this control device is the same as that of the previous modified embodiment, and thus the description thereof is omitted.

In the case of the other modified embodiment, as can be seen from FIG. 6, since the number of comparison circuits can be reduced as compared with the pre-modified embodiment, the cost of the position detection circuit 12 is reduced. Can be suppressed to a lower level.

In the above-described embodiment, three reference voltages are used. However, more different reference voltages may be used. In this case, a more optimal position detection signal can be obtained (more accurate rotor position detection becomes possible), and the rotation control of the brushless motor 4 can be made more ideal.

[0036]

As described above, according to the first aspect of the present invention, there is provided a method and a device for controlling a brushless motor, which are different from the neutral point voltage obtained by combining the terminal voltages of the armature windings of the brushless motor. A plurality of position detection signals are obtained by comparing with a reference voltage, and a position detection interval of the rotor of the brushless motor is obtained from the position detection signals, and a position that enables the most balanced rotation control among these position detection intervals. The position of the rotor is detected by the position detection signal that has obtained the detection interval, and the energization of the armature winding is switched based on this position detection. Therefore, even if the circuit (component) constants vary, The optimum position detection signal can be obtained from a plurality of different reference voltages, that is, the position of the rotor can be accurately detected. Sumota there is an effect that it is possible to perform the most balanced good rotation control without step-out of.

According to the second aspect of the present invention, the reference voltage generating means for generating a plurality of different reference voltages, the neutral point voltage obtained by combining the terminal voltages of the armature windings of the brushless motor, the plurality of reference voltages, And a position detecting interval that obtains the position detection interval of the rotor based on the position detection signal as a result of the comparison, and a position detection interval that enables the most balanced rotation control among the position detection intervals. Control means for selecting a detection signal, detecting the position of the rotor based on the selected position detection signal, and switching the energization of the armature winding of the brushless motor based on the detected position. Therefore, even if there are variations in circuit (component) constants, an optimum position detection signal can be obtained with a plurality of different reference voltages, that is, the rotor position can be accurately detected. It can be an effect that the optimum position detection makes it possible to perform a best balance good rotation control brushless motor without step-out.

According to a third aspect of the present invention, in the second aspect, the reference voltage generating means connects a plurality of resistors in series, and divides a power supply used in the rotation control by the plurality of resistors to generate the plurality of resistors. Since the reference voltage is generated, in addition to the effect of the second aspect, since the reference voltage is formed by the resistor, there is an effect that the cost can be reduced.

According to the fourth aspect of the present invention, a reference voltage generating means for generating the first to third reference voltages and switching between the second and third reference voltages to generate the reference voltage, Comparing means for comparing the neutral point voltage obtained by combining the terminal voltages of the motor armature windings with the first reference voltage, comparing the neutral point voltage with the switched second reference voltage, and Comparing means for comparing the neutral point voltage with the switched third reference voltage; and a position detection interval of the rotor obtained by a position detection signal of a comparison result obtained by the two comparing means. A position detection signal that obtains a position detection interval that enables the most balanced rotation control among the detection intervals is selected, and the position of the rotor is detected based on the selected position detection signal. And Since such a control means for switching the energization of the armature winding of the Shiresumota, even if there are variations in the circuit (component) constant, it is possible to obtain an optimum position detection signal by a plurality of different reference voltages,
In other words, the position of the rotor can be accurately detected, and the optimum position detection enables the most balanced rotation control without stepping out of the brushless motor. By means, three types of position detection signals can be obtained. That is, since one comparison means (converter) is required, the cost can be reduced.

According to a fifth aspect of the present invention, in the fourth aspect, the reference voltage generating means connects three resistors in series, and connects one end of the three resistors to a resistor which is grounded. Switch means connected in series to the resistor are connected in parallel, the first and second reference voltages are generated when the switch means is turned off, and the first and third reference voltages are generated when the switch means is turned on. Is generated, and in addition to the effect of the fourth aspect, since it is constituted by the resistor and the switch means (transistor), there is an effect that the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of a control device to which an embodiment of the present invention is applied, to which a control method of a brushless motor is applied.

FIG. 2 is a schematic time chart for explaining the operation of the control device shown in FIG. 1;

FIG. 3 is a schematic block diagram of a control device of a brushless motor according to a modified embodiment of the present invention.

4 is a schematic time chart for explaining the operation of the control device shown in FIG. 3;

FIG. 5 is a schematic time chart for explaining the operation of the control device shown in FIG. 3;

FIG. 6 is a schematic block diagram of a control device for a brushless motor according to another modified embodiment of the present invention.

FIG. 7 is a schematic block diagram of a conventional control device for a brushless motor.

FIG. 8 is a schematic time chart for explaining the operation of the control device shown in FIG. 7;

[Explanation of symbols]

2 AC / DC conversion unit 3 Inverter unit 4 Brushless motor (sensorless DC brushless motor) 5a Resistance circuit 10, 12, 14 Position detection circuit 10a, 12a, 14a Reference voltage generation circuit 10b First comparison circuit 10c Second comparison circuit 10d Third comparison circuit 11, 13, 15 Control circuit (control means) 12b Fourth comparison circuit 12c Fifth comparison circuit 14b Sixth comparison circuit A, B, C, D, E, F, G, H , I position detection signal k1 first reference voltage k2 second reference voltage k3 third reference voltage R7, R8, R9, R10, R11, R12, R13,
R14, R15, R16, R17 Resistor Tr, Tr1, Tr2 Transistor (switch means)

Claims (5)

[Claims] 1. A neutral point voltage obtained by synthesizing a terminal voltage of an armature winding of a brushless motor, a neutral point voltage is compared with a reference voltage, and a comparison result of the rotor of the brushless motor is obtained based on the comparison result. A brushless motor control method for detecting a position, switching energization of an armature winding of the brushless motor based on the position detection, and controlling rotation of the brushless motor, wherein the neutral point voltage and a plurality of While obtaining a plurality of position detection signals by comparing with different reference voltages, the position detection intervals of the rotor are obtained by the plurality of position detection signals, and the most balanced rotation control among these position detection intervals is enabled. The position of the rotor is detected by a position detection signal that obtains a position detection interval, and the energization switching timing of the armature winding of the brushless motor is obtained based on the position detection. A method for controlling a brushless motor, wherein 2. A neutral point voltage obtained by synthesizing a terminal voltage of an armature winding of the brushless motor, the neutral point voltage is compared with a reference voltage, and a comparison result of the rotor of the brushless motor is obtained based on the comparison result. A brushless motor control device that detects a position, switches energization of an armature winding of the brushless motor based on the position detection, and controls the rotation of the brushless motor. Reference voltage generating means for generating different reference voltages; comparing means for comparing the neutral point voltage with the plurality of different reference voltages; and obtaining a position detection interval of the rotor based on a position detection signal of the comparison result. Among the position detection intervals, a position detection signal that obtains a position detection interval that enables the most balanced rotation control is selected, and the rotation is selected based on the selected position detection signal. A control device for a brushless motor, comprising: control means for detecting a position of a trochanter and switching energization of an armature winding of the brushless motor based on the detected position. 3. The brushless motor according to claim 2, wherein said reference voltage generating means connects a plurality of resistors in series, and divides a power supply used for said rotation control by said plurality of resistors to generate said plurality of reference voltages. Control device. 4. A neutral point voltage obtained by combining terminal voltages of an armature winding of the brushless motor, a neutral point voltage is compared with a reference voltage, and a position of a rotor of the brushless motor is determined based on the comparison result. A brushless motor control device that controls the rotation of the brushless motor by switching the energization of the armature winding of the brushless motor based on the position detection, wherein first to A reference voltage generating means for generating a third reference voltage and switching between the second reference voltage and the third reference voltage, and comparing the neutral point voltage with the first reference voltage. Comparing means, the neutral point voltage and the switched second
Comparing means for comparing the neutral point voltage with the switched third reference voltage, and detecting the position of the rotor by the position detection signal of the comparison result obtained by the comparing means. In addition to obtaining the interval, a position detection signal that obtains a position detection interval that enables the most balanced rotation control among these position detection intervals is selected, and the position of the rotor is detected by the selected position detection signal. Control means for switching the energization of the armature winding of the brushless motor based on the position detection. 5. The reference voltage generating means connects three resistors in series, and connects a resistor connected in series with the resistor whose one end is grounded to a resistor whose one end is grounded. 5. The brushless motor control according to claim 4, wherein said first and second reference voltages are generated when said switch means is turned off, and said first and third reference voltages are generated when said switch means is turned on. apparatus.