JP2014187855A - Control device of dc brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device of a DC brushless motor capable of surely detecting position detection signal by eliminating failure in picking the position detection signal of a rotor which is caused by a ripple of an applied DC voltage.SOLUTION: A position detection mask time Tm is set which prohibits detection of a position detection signal at the next time on the basis of a position detection section time before one rotation of a motor or a position detection section time obtained from a current position detection signal. There are provided, position detection mask processing means which prohibits detection of a position detection signal of the next time on the basis of the position detection mask time Tm that is set, a circuit for measuring a DC voltage value applied to an inverter, and ripple calculation processing means which calculates a ripple voltage value from the measured DC voltage value. If the calculated ripple voltage value is larger than a predetermined value, the position detection mask processing means sets a preset minimum mask time Tmin, to prohibit detection of a position detection signal at the next time.

Description

  The present invention relates to a control technique for a sensorless DC brushless motor (hereinafter referred to as a DC brushless motor) used in a compressor of an air conditioner, and more particularly, to detect the position of a rotor reliably and perform appropriate rotation control. The present invention relates to a DC brushless motor control device.

  As a position sensorless driving method for a DC brushless motor, a method having a non-conduction phase such as a 120-degree energization method (rectangular wave energization method) using an inverter is known. For example, in the 120-degree energization method, the 120-degree section of the 180-degree section is energized, and the rotor position is detected based on the zero cross of the induced voltage generated by the rotation of the rotor in the non-energized 60-degree section. The motor is driven by switching the direction of the current flowing through the stator winding of each phase based on the above.

  Here, if noise or the like is superimposed on the waveform of the induced voltage to be detected, there is a possibility of detecting an incorrect position other than the expected zero cross, so that between the position detection and the next position detection, Processing for avoiding erroneous detection is performed by prohibiting (masking) acquisition of position detection signals for a predetermined time (hereinafter referred to as mask time) after position detection (see, for example, Patent Documents 1 to 3). ).

  In the control method of Patent Document 1, the difference between the current position detection time and the previous position detection time is defined as the position detection interval time, and the next position detection is performed based on the previous position detection interval time and the current position detection interval time. The mask time to be used is calculated. For this reason, the mask time can be changed for each position detection section. In the control method of Patent Document 1, the mask time is set on the assumption that the torque fluctuation per one rotation of the motor is regular.

JP-A-10-271879 Japanese Patent Laid-Open No. 10-28395 JP 9-215380 A

  By the way, as an environmental characteristic in which the motor is used, the capacity of the smoothing capacitor of the rectifier circuit due to secular change, for example, the difference between the outside air temperature and the indoor set temperature is large, and the compressor of the air conditioner on which the motor is mounted When operating with a high load, the ripple voltage of the DC power source converted from the AC power source by the rectifier circuit increases, the DC voltage applied to the inverter fluctuates, and the rotational speed of the motor changes. It affects the detection timing.

  Since the fluctuation of the DC voltage applied to the inverter has a different period from the motor rotation speed, if the control method of Patent Document 1 is applied as it is, the next position detection timing is overlooked, and erroneous detection is performed. There is a risk of triggering. That is, as shown in FIG. 9, the torque force fluctuation due to the voltage fluctuation is added to the fluctuation of the position detection section time. For this reason, in the control method of Patent Document 1, the next position detection timing is predicted based on the record of the past position detection section time, and the inequality (regular position detection section time <predicted position detection section time) is obtained. When the condition is established, there is a risk that the regular position detection signal may be missed depending on the determined mask time.

  For example, FIG. 10A is a ripple characteristic of a DC power supply, and the motor is driven by this DC power supply. The ripple period T varies depending on the rectification method of the AC power supply. If the half-wave rectification method is used, the ripple period T is the same as the period of the AC power supply.

  FIG. 10-2 is a diagram when the motor cycle is 1.5 times the ripple cycle. Since the number of ripple peaks and valleys differs for each rotation, the DC voltage applied to the inverter driven by the motor fluctuates and the rotation speed differs (faster at higher voltage peaks and slower at lower valleys). FIG. 10-3 shows the result of fluctuation of the motor rotation cycle due to the change in the rotation speed due to the ripple in the state of FIG. 10-2.

  Therefore, when the position detection timing is predicted in the section of the motor cycle T1 in FIG. 10-3, the cycle is actually shortened as in the section of the motor cycle T2, so that the regular position detection signal is generated within the set mask time. If it occurs, this position detection signal may be missed.

  As shown in FIG. 10-4, when the number of peaks and valleys is the same in one cycle (one rotation of the motor), the influence of ripple is eliminated, so that the motor cycle T1 and the motor cycle T2 are the same and detected. There is no risk of signal loss.

  The present invention has been made in view of the above, and a controller for a DC brushless motor capable of reliably capturing a position detection signal by eliminating a missing position detection signal of a rotor due to a ripple of a DC voltage to be applied. The purpose is to provide.

  In order to solve the above-described problems and achieve the object, a control apparatus for a DC brushless motor according to the present invention includes a rectifier circuit that converts alternating current into direct current, and an inverter that converts direct current into alternating current and drives the DC brushless motor. A control circuit that PWM-controls the inverter via a drive circuit that generates a PWM signal, and energizes the stator windings of each phase of the DC brushless motor from the inverter, and the rotor of the DC brushless motor In the DC brushless motor control apparatus for controlling the energization timing for the stator winding based on the position detection signal of the rotor obtained from the induced voltage generated in the stator winding of the non-energized phase due to rotation, 1 of the DC brushless motor It is obtained from the position detection section time before rotation or the current position detection signal. Based on the position detection section time, a position detection mask processing means for setting a position detection mask time for prohibiting detection of the next position detection signal for a predetermined time from the current position detection, and a DC voltage applied to the inverter are measured. And a ripple calculation processing means for calculating a ripple voltage value from a DC voltage value measured by the DC voltage measurement circuit, and the ripple voltage value calculated by the ripple calculation processing means is greater than a predetermined value. If it is larger, the position detection mask processing means sets the position detection mask time to a predetermined minimum mask time.

  According to another aspect of the present invention, there is provided a control apparatus for a DC brushless motor according to the above-described invention, wherein in the above-described invention, a cycle ratio calculation for comparing and calculating a cycle between a rotation cycle of the DC brushless motor and a ripple cycle Rt of a DC voltage applied to the inverter. And when the rotation cycle of the DC brushless motor is an integer multiple of the ripple cycle of the DC voltage, the position detection mask processing unit is further configured to output the position detection mask. The time is set to the position detection mask time set based on the position detection section time.

  According to the present invention, there is an effect that the position detection signal can be reliably detected by eliminating the missing position detection signal of the rotor due to the ripple of the applied DC voltage. In addition, when the motor rotation cycle is an integer multiple of the DC voltage ripple cycle, the influence of the applied DC voltage ripple is offset, so the mask time based on the current position detection interval time is reduced as it is. Can be used without.

FIG. 1 is a schematic configuration diagram of a control device for a DC brushless motor according to the present invention. FIG. 2 is a diagram illustrating an example of a flowchart of the ripple value measurement step. FIG. 3 is a time chart for explaining the position detection mask time in the present invention. FIG. 4 is a diagram showing an example of a flowchart of the control device for the DC brushless motor according to the present invention. FIG. 5 is an explanatory diagram of waveforms in the case of ripple cycle ≦ motor rotation cycle (integer multiple of ripple voltage cycle). FIG. 6 is an explanatory diagram of waveforms in the case of ripple cycle <motor rotation cycle (non-integer multiple of ripple voltage cycle). FIG. 7 is an explanatory diagram of waveforms in the case of ripple cycle> motor rotation cycle. FIG. 8 is a time chart showing an example of position detection timing. FIG. 9 is an explanatory diagram when a regular position detection signal is missed. FIG. 10A is an explanatory diagram of ripple characteristics of the DC power supply. FIG. 10B is an explanatory diagram of the case where the motor is driven at a cycle that is 1.5 times the ripple cycle. FIG. 10C is an explanatory diagram illustrating a result of a change in the rotation period of the motor due to a change in the rotation speed due to the ripple. FIG. 10-4 is an explanatory diagram of a case where the motor is driven with a cycle twice the ripple cycle.

  Embodiments of a control apparatus for a DC brushless motor according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

  As shown in FIG. 1, the control device 10 includes a rectifier circuit 12 that converts alternating current supplied from an alternating current power supply AC into direct current, an inverter 14 that converts direct current into alternating current and drives a DC brushless motor M, and a motor M. A position detection circuit 16 for obtaining a rotor position detection signal from an induced voltage generated in a stator winding in a non-conduction phase due to rotation of the rotor of the rotor, and a timing for switching energization to the stator winding based on the position detection signal from the position detection circuit 16 On the other hand, an inverter control means for controlling the inverter by outputting a predetermined drive signal to the switching elements BU, BV, BW, BX, BY, BZ of the inverter 14 via the drive circuit 20 in order to switch the energization at this calculation timing. And a control circuit 18 including 23. The control circuit 18 includes a CPU (Central Processing Unit) and a memory.

  The configuration and operation of the position detection circuit 16 will be described. The position detection circuit 16 includes resistors 161 to 166 and a comparator 167. One end of each of the resistors 161 to 163 is connected to each phase of the stator of the motor M, and the other end of each of the resistors 161 to 163 is connected. A resistor 164 is connected between a connection point of each of the resistors 161 to 163 and the ground, and a connection point of each of the resistors 161 to 163 and the resistor 164 is connected to a non-inverting input terminal of the comparator 167. Hereinafter, the voltage at the connection point of each of the resistors 161 to 163 and the resistor 164 is referred to as a virtual neutral point voltage. A resistor 165 and a resistor 166 are connected in series between the positive side of the rectifier circuit 12 and the ground, and the voltage at the connection point of the resistors 165 and 166 is supplied to the inverting input terminal of the comparator 167 as a reference voltage. . This reference voltage is set so as to coincide with the voltage at the zero cross point (positive / negative inflection point) of the virtual neutral point voltage. The comparator 167 detects the zero-cross point of the virtual neutral point voltage (that is, the zero-cross point of the induced voltage) by comparing the virtual neutral point voltage with the reference voltage, and detects the position of the rotor of the motor M (hereinafter referred to as “the rotor position of the motor M”). A position detection signal for simply “position detection” is output.

  The control device 10 further includes a DC voltage measurement circuit 22, a ripple calculation processing means 26, and a position detection mask processing means 24 in the control circuit 18.

  The DC voltage measurement circuit 22 measures a DC voltage value applied to the inverter 14. Since the DC voltage is high, the voltage divided by the resistor is AD converted by the A / D converter, and the converted voltage value is input to the ripple calculation processing means 26 of the control circuit 18. The ripple calculation processing unit 26 calculates a ripple voltage value ΔVdc and a ripple cycle Rt of the DC voltage from the input voltage value. A method for calculating the ripple voltage value ΔVdc and the ripple period Rt will be described next.

  As shown in the flowchart of FIG. 2, the DC voltage fluctuation is monitored, for example, by measuring the DC voltage value by the DC voltage measuring circuit 22 every 1 msec, and measuring the value at least 20 msec (the maximum value of the ripple period, (Ripple period when half-wave rectification is performed at an input AC power supply frequency of 50 Hz) is stored (step S101). The ripple voltage value ΔVdc and the ripple cycle Rt are calculated by extracting the maximum value and the minimum value of the DC voltage value from the stored DC voltage value (step S102). The calculated ripple voltage value ΔVdc and ripple cycle Rt are stored (step S103), the process returns to S101 (step S104), and the above processing is repeated.

  The position detection mask processing unit 24 multiplies the position detection section time obtained from the previous and current position detection signals by the position detection circuit 16 by a predetermined coefficient α (α <1) and prohibits position detection. And the detection of the next position detection signal is prohibited between the current position detection and the position detection mask time.

  In the above configuration, the rotational speed of the motor also fluctuates due to fluctuations in the DC voltage due to power supply ripple. Therefore, if the ripple voltage exceeds a predetermined value Vdc_err, the position detection time is affected, and the position set by the position detection mask processing means 24 The position detection signal is generated before the detection mask time and cannot be detected. Therefore, the ripple calculation processing means 26 in the control circuit 18 has the position detection mask processing means 24 in the case where the ripple voltage value calculated from the DC voltage value measured in the DC voltage measurement circuit 22 is larger than the predetermined value Vdc_err. The detection of the position detection signal is prohibited by setting the position detection mask time to a predetermined minimum mask time. The minimum mask time setting condition is a period in which position detection is possible at the maximum motor speed with the shortest position detection period. Actually, however, the time from the switching of energization, which will be described later, to immediately after the switching of the upper and lower arms of the inverter is completed. Is the lower limit of the minimum mask time, and is determined by actual machine verification or the like.

Next, the position detection mask time will be described with reference to FIG.
As shown in FIG. 3, in the position detection mask processing means 24, the current position detection section obtained from the timing t0 at which the previous position detection signal (one section before) is detected and the timing t1 at which the current position detection signal is detected. The time Δt is predicted as the predicted time T (time from t1 to t4) of the next position detection section, and the position detection mask time Tm (time from t1 to t3) for prohibiting the detection of the next position detection signal is set. To do. As a method for setting the mask time Tm, a value obtained by multiplying the current position detection section time Δt by a predetermined coefficient α (α <1) is set as the mask time. In FIG. 3, the predicted time T and the mask time Tm of the next position detection section are set based on the continuous position detection time. In practice, however, the position detection signal depends on the number of motor poles. The number of times of output per cycle varies, for example, 12 times for a 4-pole motor and 18 times for a 6-pole motor during one revolution of the motor. As shown in Patent Document 1, the load of the motor has a characteristic of torque fluctuation in units of one rotation of the motor, and therefore the position detection section time varies every time a position detection signal is detected. Therefore, the predicted time T of the next position detection section is a predetermined coefficient α (α <1) for the position detection section time of 12 sections before if it is a 4-pole motor, and for the position detection section time of 18 sections if it is 6 poles. By adopting the value multiplied by as the mask time, the influence of the position detection section time due to the motor load is eliminated. Further, the motor cycle is calculated by adding the position detection section time for one rotation.

  The detection of the next position detection signal is prohibited for the mask time Tm from t1 to t3 in the predicted time T of the next position detection section from the timing t1 at which the current position is detected, and the remaining time from t3 to t5 is the position. It becomes a detectable period. t5 assumes that the position detection time from t1 is the longest, and t4 is a predicted value of position detection to the last. Therefore, even if the position detection circuit 16 does not detect the position by t4, it is determined that the step is out of step. Without detection, position detection is possible until t5. In the present invention, when the ripple value calculated from the DC voltage value measured by the DC voltage measurement circuit 22 in the ripple calculation processing unit 26 is larger than the predetermined value Vdc_err, the position detection mask processing unit 24 sets the mask time Tm. The time is shortened to a predetermined minimum mask time Tmin (from t1 to t2), and detection of the next position detection signal is prohibited for the shortened mask time Tmin.

  In this way, by shortening the mask time to Tmin from the time Tm calculated by the position detection mask processing means 24, the position detectable period is lengthened, and the motor cycle is determined from fluctuations in rotational speed due to DC voltage fluctuations due to ripples. Even if a position detection signal is input before the mask time Tm set by the position mask processing means 24, the situation in which the position detection signal is missed can be avoided as compared with the conventional control method of Patent Document 1. it can. Therefore, according to the present invention, it is possible to eliminate the missing position detection signal of the rotor due to the ripple of the DC voltage to be applied, and to reliably detect the position detection signal.

  In the above-described embodiment, the control circuit 18 further includes period ratio calculating means 28 for obtaining a period ratio between the rotation period Mt of the motor and the ripple period Rt of the DC voltage applied to the inverter. As a result of the calculation by means 28, if the motor rotation cycle Mt is longer than the DC voltage ripple cycle Rt and the motor rotation cycle Mt is an integer multiple of the DC voltage ripple cycle Rt, the position detection mask process is performed. The means 24 prohibits the detection of the next position detection signal for the position detection mask time Tm set based on the current position detection section time Δt. As described above, when the relationship is an integral multiple, there is no influence of ripple (see FIG. 10-4), so that the position detection mask processing means 24 obtains it without going through the process of shortening the mask time Tm. Position detection can be performed using the mask time Tm.

The processing operation of the position detection mask processing means 24 will be described with reference to FIG.
As shown in the flowchart of FIG. 4, the position detection circuit 16 detects the next position detection signal from the current position detection t1 based on the current position detection section time ΔT obtained from the previous and current position detection signals. The position detection mask time Tm to be prohibited is set (step S111). Next, when the ripple value calculated based on the DC voltage value measured by the DC voltage measurement circuit 22 is equal to or higher than a predetermined voltage (Yes in step S112), the ripple calculation processing unit 24 performs step. On the contrary, if the voltage is less than the predetermined voltage (No in step S112), the process returns to S111 while maintaining the mask time Tm set in the previous step S111 (step S116).

  On the other hand, if it is determined in step S113 that the motor rotation cycle is greater than or equal to the ripple cycle by the cycle ratio calculation unit 28 that compares and calculates the motor rotation cycle and the ripple cycle calculated by the ripple calculation processing unit 26, the process proceeds to step S114. On the other hand, if the rotation period of the motor is smaller than the ripple period, the process proceeds to step S115, where the mask time Tm set in the previous step S111 is shortened to a predetermined minimum mask time Tmin (step S115), and S111 (Step S116).

  In step S114, it is determined whether or not the ratio of the motor rotation cycle and the ripple cycle calculated by the cycle ratio calculation means 28 is an integral multiple. If the result is Yes, the setting is made in the previous step S111. The next detection of the position detection signal is prohibited at the mask time Tm, and the process returns to S111 (step S116). On the other hand, if No in step S114, the mask time Tm set in the previous step S111 is shortened to a predetermined minimum mask time Tmin (step S115), and the process returns to S111 (step S116).

  As described above, in the present invention, when it is determined that the preliminary result of the next position detection timing cannot be matched with the actual position detection timing due to the influence of the DC voltage ripple (mismatch state), By making the detection of the position detection signal valid by setting the position detection mask time to a short time, it is possible to avoid missing the position detection signal.

  Next, a specific determination method for determining whether or not the prediction result is the inconsistent state will be described.

  Focusing on ripple fluctuations of DC voltage as a variable element having a frequency that is not linked to the motor rotation speed, and further limiting the conditions that cause inconsistency from a specific rotation speed, it is possible to increase the accuracy of the determination of the inconsistency state. it can.

  In the mismatch state determination process, the sum of the fluctuation of the DC voltage and the fluctuation of the motor load torque appears as the fluctuation of the position detection section time, so that the fluctuation of the position detection section time as shown in FIG. By limiting the conditions that occur, the position detection mask time is not shortened simply by the magnitude of the ripple value, so that the mismatching state determination accuracy can be increased.

The fluctuation of the position detection time is due to the change in the rotation cycle of the motor, and the factor to change is the ripple of the motor load and the DC power supply. The relationship between the ripple cycle and the rotation cycle of the motor at this time is the following three. The explanation is divided into two cases.
(1) Ripple cycle Rt ≦ motor rotation cycle Mt (however, an integral multiple of the ripple cycle) (2) Ripple cycle Rt <motor rotation cycle Mt (however, a non-integer multiple of the ripple cycle) (3) When ripple cycle Rt> motor rotation cycle Mt

  FIG. 5 corresponds to (1), FIG. 6 corresponds to (2), and FIG. 7 corresponds to (3). The upper part of each figure represents the position detection time with respect to the elapsed time, the middle part represents the load fluctuation of the motor, and the lower part represents the ripple that is the DC voltage fluctuation. The load characteristic of the middle stage motor represents the load characteristic of one cycle (represented by two vertical dotted lines) of the motor when mounted on the compressor. Further, the upper position detection time is a figure showing that the position detection time becomes longer as the time becomes larger, and is therefore inversely proportional to the rotational speed of the motor. Therefore, when the position detection time is long, the rotation speed is slow. For example, when the load on the motor is light and the DC voltage is high, the rotation speed increases. Conversely, when the motor load is heavy and the DC voltage is low, the rotation speed decreases. The upper position detection time characteristic is a characteristic obtained by adding the lower DC voltage fluctuation to the middle motor load.

  When the motor rotation period (1) is an integral multiple of the ripple period, as shown in FIG. 5, the position detection time before one rotation of the motor is the same as the next position detection time. The speed is constant. When the motor rotation period (2) is a non-integer multiple of the ripple period, as shown in FIG. 6, there is a difference between the position detection time before one rotation of the motor and the next position detection time. In the case of (3) ripple cycle> motor rotation cycle, as shown in FIG. 7, there is also a timing at which a difference occurs between the position detection time before one rotation of the motor and the next position detection time.

  To summarize the above results, if any one of the following conditions 1 and 2 is satisfied, there is a possibility that the preliminary result of the next position detection timing is not appropriate.

Condition 1: Ripple cycle <motor rotation cycle and ripple cycle × integer ≠ motor rotation cycle Condition 2: ripple cycle> motor rotation cycle

  Here, when the position detection mask time is set to a predetermined minimum mask time, the ripple voltage ΔVdc recorded in the DC voltage monitoring process is set to a predetermined value regardless of whether the above condition 1 or 2 is satisfied. When the position detection time is affected beyond the value Vdc_err, it may be determined that the state is inconsistent. Here, the voltage Vdc_err can be determined in advance by actual machine verification or the like.

Next, a position detection processing method when it is determined as an inconsistent state will be described.
If it is determined that the prediction result of the next position detection timing is in an inconsistent state, the position detection mask time Tm already set by the position detection mask processing means 24 is invalidated and the position detection mask time is set to the time. The predetermined minimum mask time Tmin shorter than Tm is set, and the mask time is set to be shorter than that set by the position detection mask processing means 24 to permit detection of the position detection signal. The lower limit value of the shortened position detection mask time can be the time from the switching of energization to the time immediately after the switching of the upper and lower arms of the inverter.

  The reason for this is that, for example, as shown in FIG. 8, the signal detected by the position detection circuit 16 cannot correctly detect the zero-cross point of the induced voltage due to the chopping waveform superimposed on the induced voltage. Cannot be specified. Therefore, before switching the next energized phase so that the signal detected by the position detection circuit 16 can maintain a constant level of Low level or High level, the upper arm of the phase to be switched (BU in FIG. 1). , BV and BW phases are switched) and the lower arm (BX, BY and BZ phases in FIG. 1 are switched). For example, the circle in the lower left of FIG. 8 is an example of switching from the W-Y phase energization state to the U-Y phase energization. In order to facilitate position detection, the lower arm (the BY phase in FIG. ) Switching to switching of the upper arm (BW phase in FIG. 1) until the U-phase voltage rises and exceeds a predetermined threshold value, the position detection signal is low regardless of switching on / off. In order to maintain the level, it is possible to determine the timing at which the level is switched to the High level for the first time as the position detection timing.

  As described above, the control device for the DC brushless motor according to the present invention eliminates the loss of the rotor position detection signal due to the ripple of the DC voltage applied to the DC brushless motor used in the compressor of the air conditioner. Since the position detection signal can be reliably detected, it is suitable for stable motor control.

DESCRIPTION OF SYMBOLS 10 DC brushless motor control apparatus 12 Rectifier circuit 14 Inverter 16 Position detection circuit 18 Control circuit 20 Drive circuit 22 DC voltage measurement circuit 23 Inverter control means 24 Position detection mask processing means 26 Ripple calculation processing means 28 Period ratio calculation means M Motor AC AC source

Claims (2)

A rectifier circuit that converts alternating current to direct current; an inverter that converts direct current to alternating current to drive a DC brushless motor; and a control circuit that performs PWM control of the inverter via a drive circuit that generates a PWM signal. While energizing the stator windings of each phase of the DC brushless motor, based on the rotor position detection signal obtained from the induced voltage generated in the stator windings of the non-energized phase by the rotation of the rotor of the DC brushless motor In the control device for the DC brushless motor for controlling the energization timing to the stator winding,
Detection of the next position detection signal for a predetermined time from the current position detection based on the position detection section time before one rotation of the DC brushless motor or the position detection section time obtained from the current position detection signal. Position detection mask processing means for setting a position detection mask time for prohibiting,
A DC voltage measuring circuit for measuring a DC voltage applied to the inverter, and a ripple calculation processing means for calculating a ripple voltage value from a DC voltage value measured by the DC voltage measuring circuit,
When the ripple voltage value calculated by the ripple calculation processing unit is larger than a predetermined value, the position detection mask processing unit sets the position detection mask time to a predetermined minimum mask time. Control device for DC brushless motor. Period ratio calculating means for comparing and calculating the period between the rotation period of the DC brushless motor and the ripple period Rt of the DC voltage applied to the inverter is further included. As a result of calculation by this means, the rotation period of the DC brushless motor is When the relationship is an integral multiple of the ripple period of the DC voltage,
2. The DC brushless motor control device according to claim 1, wherein the position detection mask processing unit sets the position detection mask time to the position detection mask time set based on the position detection section time. 3.

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