JP2007209154A - Controller for brushless dc motor, heat-exchange type cooling device, and ventilator blower - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a low noise and highly reliable controller for a brushless DC motor of a heat-exchange type cooling device used for cooling equipment in cellular phone base stations or the like, wherein the commutation timing for motor current is controlled properly in a sensorless manner, without the use of a position sensor, when the controller is controlled by wide-angle energization. <P>SOLUTION: The controller 12 for the brushless DC motors 2 estimates the phase of the voltage applied to the winding of the stator 4 relative to the induced voltage induced in the winding of the stator 4 of the brushless DC motor 2 which is stored beforehand, based on the change rate of the value of current supplied from a DC power supply 5 to an inverter circuit 1, and decides a timing for commutation so that the estimated phase follows a predetermined target phase. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a control device for a brushless DC motor used in a ventilation fan, for example, a heat exchange type chiller used for equipment cooling of a mobile base station, etc. The present invention relates to controlling the commutation timing of a brushless DC motor by sensorless driving without using a position sensor in a control device that rotates by wide-angle energization with a period.

  In recent years, this type of ventilation blower employs a brushless DC motor that is highly efficient and capable of continuously changing the number of revolutions for continuous ventilation for 24 hours 365 days and adjustment of the ventilation amount. In addition, because of cost requirements in the market, reduced installation space and continuous operation including nighttime, low cost, small size, low noise and high reliability of the device are required. There is a demand for cost reduction, size reduction, noise reduction, and high reliability of the control device.

  For example, specifically in a heat exchange type cooler, after taking in the air in the heating element storage box, the air is passed through the heat exchange element to exchange heat, and then returned to the heating element storage box and circulated again. And outside air ducts that take in outside air, pass through the heat exchange elements and exchange heat, and then exhaust to the outside air. Both these air paths are independent by the partition plate, Is known in which a ventilation blower for conveying each air is installed (see, for example, Patent Document 1).

  Usually, the heat exchange type cooler having such a configuration is used for cooling mobile base stations and the like, and a DC low voltage power source is supplied to the heat exchange type cooler from the mobile base station body side, and a brushless DC motor is mounted. A ventilation fan is driven.

  Hereinafter, the operation of the heat exchange type cooler will be described with reference to FIG.

  As shown in FIG. 18, the heated air in the heating element storage box 101 (hereinafter referred to as “inside air”) has an indoor brushless DC motor 104 mounted from the inside air inlet 103 of the heat exchange type cooler 102. The air is sucked by the indoor fan 105, passes through the heat exchange element 106, and then circulates in a circulation air path that returns from the inside air discharge port 107 into the heating element storage box 101. On the other hand, the outside air sucked from the outside air inlet 110 by the outside fan 109 equipped with the outside brushless DC motor 108 passes through the heat exchange element 106 and then is discharged again to the outside air from the outside air outlet 111. . The inside air passage and the outside air passage are partitioned in a substantially airtight state by the partition plate 112 so that the two air passages are independent, and a heat exchange element that exchanges sensible heat of the outside air and the inside air at the intersection of the inside air passage and the outside air passage. 106 is arranged. With the above configuration, the heat exchange type cooler 102 takes in the low temperature outside air, exchanges heat with the warm air inside the heating element storage box 101 by the heat exchange element 106, exhausts the warm outside air, and cools it. The air that has become is supplied into the box.

  The indoor brushless DC motor 104 and the outdoor brushless DC motor 108 normally use a brushless DC motor with a built-in magnetic pole sensor such as a hall element, and the control device 113 for driving the brushless DC motor has a base station installed. In order not to be affected by low-temperature outside air or dust at the place where the heat is applied, the outdoor brushless DC motor 108 installed in the inside air path of the heat exchange type cooler 102 and exposed to the outside air is connected to a power lead 114 having a long relay. And the sensor signal lead wire 115. Drive power is supplied to the control device 113 from a low-voltage DC power supply 116 installed in the heating element storage box 101 or the like.

  The wide-angle energization control of the brushless DC motor uses a brushless DC motor incorporating three magnetic pole sensors such as the normal Hall element having the above-described configuration, and corresponds to a predetermined electrical angle from the time interval of the magnetic pole position detection signal of the magnetic sensor. Calculate the energization overlap period, control the energization period of the stator coil accordingly, drive the brushless DC motor with the energization overlap period of the predetermined electrical angle, reduce the ripple of drive torque, vibration and noise Wide-angle energization control is performed to reduce the amount (see, for example, Patent Document 2).

  Hereinafter, the operation of the wide-angle energization control will be described with reference to FIGS. 19 and 20. As shown in FIG. 19, the inverter circuit 117 has a three-phase inverter bridge configuration, Q1, Q2, and Q3 are U, V, and W-phase upper arm switching elements. Similarly, Q4, Q5, and Q6 are respectively It is a U, V, W phase lower arm switching element. The switching diodes D1, D2, D3, D4, D5, and D6 are connected to each switching element in parallel. The brushless DC motor 118 includes a rotor 119 and a stator 120, and stator windings L1, L2, and L3 are arranged on the stator 120 so as to have a phase difference of 120 degrees in electrical angle. Further, three magnetic sensors 126 of Hu, Hv, and Hw are incorporated so as to have a phase difference of 120 degrees with respect to each other in electrical angle, and the position of the magnetic pole of the rotor 119 is detected. The magnetic pole position detection signal is output to the time interval calculation means 127 built in the microcomputer 122.

  The time interval calculation unit 127 calculates a time interval from the input position detection signal, and calculates the energization overlap period from the predetermined electrical angle 129 by the energization overlap period calculation unit 128.

  Between the DC power supply 116 and the switching element, a current detection resistor 121 for detecting the output current of the DC power supply 116 is disposed as shown in the figure. The arithmetic unit 124 built in the microcomputer 122 calculates the phase commutation timing of the motor current from the energization overlap period calculation means 128, and controls switching signals U +, V +, W +, U−, V−, W− for controlling the inverter. Is output. The drive circuit 125 is driven by energizing the switching elements Q1, Q2, Q3, Q4, Q5, and Q6 based on the switching signal output from the computing unit 124.

  FIG. 20A shows specific time intervals of the magnetic pole position detection signals of Hu, Hv, and Hw. FIG. 20 (b) shows specific switching signals of U +, V +, W +, U−, V−, and W− with a 150 degree energization period, energization period, energization overlap period, and non-overlapping periods. Is shown.

  Sensorless control of a brushless DC motor is a control method that determines the commutation timing of the motor based on the induced voltage, focusing on the correlation between the induced voltage induced in the stator winding during motor driving and the field. A sensorless control method is known that determines the commutation timing of the motor by estimating the magnetic pole position of the rotor based on the rate of change of the current value supplied from the power source to the inverter circuit with respect to time (for example, Patent Documents). 3).

  The operation of the brushless DC motor control device will be described below with reference to FIG.

  As shown in FIG. 21, the inverter circuit 117 has a three-phase inverter bridge configuration, Q1, Q2, and Q3 are U, V, and W phase upper arm switching elements. Similarly, Q4, Q5, and Q6 are respectively It is a U, V, W phase lower arm switching element. The switching diodes D1, D2, D3, D4, D5, and D6 are connected to each switching element in parallel. The brushless DC motor 118 includes a rotor 119 and a stator 120, and stator windings L1, L2, and L3 are arranged on the stator 120 so as to have a phase difference of 120 degrees in electrical angle. A current detection resistor 121 that detects the output current of the DC power supply 116 is disposed between the DC power supply 116 and the switching element. The voltage between the terminals of the current detection resistor 121 is input to an A / D converter 123 built in the microcomputer 122. The computing unit 124 calculates the phase commutation timing of the motor current with reference to the current value digitized by the A / D converter 123, and controls switching signals U +, V +, W +, U−, V−, W- is output. The drive circuit 125 is driven by energizing the switching elements Q1, Q2, Q3, Q4, Q5, and Q6 every 120 degrees based on the switching signal output from the computing unit 124.

The polarity of the rate of change of the current output from the DC power supply 116 with respect to time is detected, the magnetic pole position of the rotor is estimated based on the time when the polarity changes, and the polarity reversal time is measured based on the detection signal. From this time, the magnetic pole position of the rotor is estimated and the commutation timing is obtained.
JP 2001-156478 A JP-A-62-171489 JP-A-8-126379

  In such a conventional configuration, when a magnetic sensor is mounted, the magnetic sensor incorporated in the outdoor brushless DC motor and the control device are connected by a long relay lead, so the relay lead of the sensor signal is affected by noise. It is easy to receive and malfunction, and the wiring work in the heat exchange type cooling machine is complicated and troublesome, and there is a problem that it becomes a high-cost cooling machine, and since the magnetic sensor is built in the DC motor, the DC motor As a result, there is a problem that the apparatus cannot be downsized.

  In the case of a sensorless drive brushless DC motor, the commutation timing is determined by estimating the magnetic pole position on the assumption that the location where the current value is minimum, that is, the location where the induced voltage is maximum, is determined. In the case of, the current waveform is different and the current value is not minimized. Therefore, the place where the induced voltage becomes maximum cannot be estimated, and it is difficult to grasp the magnetic pole position, which causes a problem that the DC motor cannot be driven.

  Further, such a conventional configuration relates to 120-degree rectangular wave energization, and there is a problem that noise is generated due to resonance with the apparatus because there are many torque pulsations.

  The present invention solves such a conventional problem, and eliminates a magnetic sensor and a sensor signal relay connector and drives a brushless DC motor with wide-angle energization, so that it is small, low cost, low noise and highly reliable. It aims at realizing the control device of a brushless DC motor.

  In order to achieve the above object, a brushless DC motor control device of the present invention is a brushless having a rotor and a stator winding connected to a DC power supply via an inverter circuit in which a plurality of switching elements are bridge-connected. In the control device for turning on and off the switching element of the inverter circuit, extending the ON period by 120 degrees or more in electrical angle, and rotating the DC motor by wide-angle energization by providing an energization overlap period, the inverter circuit from the DC power supply Is induced in the stator winding of the brushless DC motor stored in advance based on a current waveform obtained from a current detection resistor for detecting a current supplied to the current detector and a current value output from the current detection resistor. Phase estimating means for estimating the phase of the induced voltage to be applied to the stator winding and the phase estimating means Thus the estimated phase, in which the brushless DC motor of the control device, characterized in that it comprises a commutation timing determining means for determining commutation timing so as to follow the target phase set in advance.

  By this means, it is possible to detect the current flowing through the inverter circuit and estimate the phase, and it is possible to detect the position reliably even in wide-angle energization, and sensorless driving is possible without requiring a complicated phase estimation circuit. Thus, a brushless DC motor control device that is small, low cost and low in noise can be obtained.

  Further, the other means calculates the ratio of the current value at the first and second timings determined in advance in the current waveform supplied from the DC power supply to the inverter circuit as the current change rate. The correlation curve of the phase between the voltage induced in the stator winding and the voltage applied to the stator winding from the rate of change is stored in advance.

  Thereby, by storing the correlation curve in advance, the phase can be estimated without requiring a complicated calculation, and an inexpensive microcomputer can be used, and a low-cost brushless DC motor control device can be obtained.

  Further, the other means obtains the first current value at the predetermined first timing and the second current value at the second timing in the period where the energization does not overlap, and the phase estimating means obtains the first current value at the first timing. The ratio of the second current value to the current value is calculated as the current change rate.

  As a result, in estimating the phase within the commutation cycle, the relationship between the current change rate and the phase of the induced voltage induced in the stator winding is clear, and the current value is sampled at a timing at which the change rate is relatively large. It is possible to obtain a highly reliable brushless DC motor driving apparatus that can obtain an accurate and larger current change rate and improve phase estimation accuracy.

  Further, the other means stores the current change rate in a mechanical angle for one rotation period to obtain an average value of the current change rate of one rotation so that the phase can be estimated from the average value of the current change rate of one rotation. It is a thing.

  As a result, it is possible to reduce the effects of current variations due to variations in switching elements, rotor magnets, load imbalance, etc., and drive highly reliable brushless DC motors that can improve phase estimation accuracy. A device is obtained.

  Another means is to store the current change rate for one rotation at a mechanical angle, obtain an average value of the current change rate for one rotation, and compare the latest current change rate with the current change rate before one rotation. When the difference is smaller than a predetermined value, the phase is estimated from the average value of the current change rate of one rotation. On the other hand, when the difference is larger than the predetermined value, the phase is calculated from the latest current change rate. Can be estimated.

  As a result, the magnitude of the load fluctuation can be detected, a more accurate current change rate can be obtained according to the load fluctuation, and a highly reliable brushless DC motor control apparatus capable of improving the phase estimation accuracy can be obtained. .

  Further, the other means performs time correction on the commutation period according to the phase difference between the phase estimated by the phase estimation means and the target phase, and determines the current commutation timing and the next commutation period. It is a thing.

  As a result, an optimal commutation timing can always be obtained for each commutation cycle with respect to load fluctuation, and a highly reliable brushless DC motor control device that can improve followability to load fluctuation is obtained.

  Further, the other means divides the current commutation cycle into four, estimates the phase by the phase estimation means within a period of three quarters from the previous commutation timing, and according to the phase difference from the target phase. Only the last quarter period is corrected for time.

  As a result, the commutation timing and the next commutation cycle can be determined immediately after the phase is estimated by the phase estimation means, so that it is possible to quickly detect the magnitude of the load fluctuation, and the optimum energization according to the load fluctuation. A highly reliable control device for a brushless DC motor that can obtain the timing and the energization cycle and can improve the followability to the load fluctuation is obtained.

  The other means compares the phase estimated by the phase estimation means with the target phase, and when the phase difference is larger than a predetermined phase difference, the phase difference between the target phase and the actual phase from the current commutation period. The time is corrected according to the calculation, the next commutation cycle is calculated, and the commutation timing is determined. On the other hand, when it is small, only the time section of a quarter of the predetermined commutation period is corrected for time, the next commutation period is calculated, and the commutation timing is determined.

  This makes it possible to detect the magnitude of load fluctuations, obtain the optimum energization timing according to the load fluctuation at each commutation timing, and improve the followability to the load fluctuation with high reliability. A control device for the DC motor is obtained.

  Another means is to correct the commutation timing so as to follow the target phase by changing the amount of time correction during startup and during operation.

  As a result, the rotation is unstable at start-up, so an error is likely to occur in the phase estimation.By changing the amount of time correction between start-up and operation, it is possible to reduce instability of rotation and step-out. Thus, a highly reliable brushless DC motor control device that can improve the followability to load fluctuations can be obtained.

  Further, another means is that the switching element is turned on by rectangular wave energization without an energization overlap period by setting the ON period of the switching element to 120 degrees in electrical angle at startup, and rotated at wide angle energization in operation. .

  As a result, wide-angle energization provides an energization overlap period, so control is more complicated than 120-degree energization. In particular, rotation is unstable at start-up, and errors tend to occur in the energization overlap period and phase estimation. Start with 120-degree energization with no period, and switch to wide-angle energization during operation where the rotation is stable, thereby reducing the instability and step-out of the rotation, and improving the followability to load fluctuations with high reliability A control device for the brushless DC motor is obtained.

  Another means is that a brushless DC motor control device is mounted on a ventilation fan, for example, a heat exchange type cooler.

  This eliminates the need for a relay lead wire for the sensor signal used for connection with the control means installed on the side of the inside air flow path, eliminates the need for connecting the relay wire, and thus reduces the size and cost of the sensor signal. Since there is no influence of malfunction due to noise on the wire, a highly reliable ventilation fan, for example, a heat exchange type cooler can be provided.

  According to the present invention, since a sensorless drive is possible with wide-angle energization using an inexpensive microcomputer without requiring a complicated phase estimation circuit, a compact, low-cost, low-noise brushless DC motor control device is provided. Can be provided.

  In addition, it eliminates the need for sensor signal lead wires and eliminates the effects of noise. Even if the load size changes, such as a light load or heavy load, it can always be in the optimum phase according to the load fluctuation. Thus, even when the load fluctuation is large due to disturbance or the like, the step-out does not occur. Therefore, a highly reliable and highly efficient brushless DC motor control device can be provided.

  In addition, since a magnetic sensor is not required, the brushless DC motor can be reduced in size and cost, and the lead wire for the sensor signal is not required, and there is no need to connect a relay line. An apparatus, for example, a heat exchange type cooler can be specifically provided.

  According to the first aspect of the present invention, a brushless DC motor having a rotor and a stator winding connected via an inverter circuit in which a plurality of switching elements are bridge-connected to a DC power supply is switched to the inverter circuit. In the control device for turning on and off the element, extending the ON period by 120 degrees or more in electrical angle and rotating by wide angle energization by providing an energization overlapping period, a current for detecting a current supplied from the DC power source to the inverter circuit A detection resistor and a stator winding with respect to an induced voltage induced in the stator winding of the brushless DC motor stored in advance based on a current waveform obtained from a current value output from the current detection resistor. A phase estimation means for estimating a phase of the applied voltage, and a phase estimated by the phase estimation means is predetermined. It has commutation timing determination means that determines the commutation timing so as to follow the target phase, can detect the current flowing through the inverter circuit and estimate the phase, and can reliably detect the position even in wide-angle energization. Thus, a sensorless drive is possible without the need for a complicated phase estimation circuit, and a compact, low-cost and low-noise brushless DC motor control device can be realized.

  According to a second aspect of the present invention, in the first aspect of the present invention, the phase estimation means is configured such that the first current value and the second current at a first timing determined in advance in a period in which the energization does not overlap. The second current value at the timing is obtained, and the ratio of the second current value to the first current value is calculated as a current change rate. By storing the correlation curve in advance, complicated calculation is required. Therefore, it is possible to detect the phase without using it, and it is possible to use an inexpensive microcomputer, thereby realizing a low-cost brushless DC motor control device.

  According to a third aspect of the present invention, in the second aspect of the present invention, the phase estimation means is configured to cause the first current value and the second current at a predetermined first timing in a period in which energization does not overlap. The second current value at the timing is obtained, and the ratio of the second current value to the first current value is calculated as a current change rate. In the estimation of the phase in the commutation cycle, the current change rate and The phase relationship of the induced voltage induced in the stator winding is clear, and the current value can be sampled at a position where the rate of change is relatively large, and an accurate and larger rate of current change can be obtained. In addition, a highly reliable brushless DC motor driving apparatus capable of improving the phase estimation accuracy can be realized.

  According to a fourth aspect of the present invention, in the third aspect of the present invention, the current change rate is stored as a mechanical angle for one rotation period, and an average value of the current change rate of one rotation is obtained. The phase can be estimated from the average value of the current change rate, and the effects of current variations due to variations in switching elements, rotor magnets, and load imbalance can be reduced. A highly reliable brushless DC motor drive device that can improve the estimation accuracy can be realized.

  According to a fifth aspect of the present invention, in the invention according to the fourth aspect, the current change rate is stored in a mechanical angle for one rotation period, an average value of the current change rate of one rotation is obtained, and the latest current is obtained. When the rate of change and the rate of change of current before one rotation are compared, and the difference is smaller than a predetermined value, the phase is estimated from the average value of the rate of change of current for one rotation, while the value determined in advance Is larger, the phase can be estimated from the latest current change rate, the magnitude of the load fluctuation can be detected, and a more accurate current detection rate can be obtained according to the load fluctuation, A highly reliable brushless DC motor control device capable of improving the phase estimation accuracy can be realized.

  According to a sixth aspect of the present invention, in the invention according to any one of the first to fifth aspects, time correction is performed according to the phase difference between the target phase and the actual phase from the previous commutation cycle. The commutation timing and the next commutation cycle are calculated and the commutation timing is determined, and the optimum commutation timing can always be obtained for each commutation cycle with respect to load fluctuations. Therefore, a highly reliable brushless DC motor control device that can improve the follow-up performance with respect to the fluctuation of the motor can be realized.

  According to a seventh aspect of the present invention, in the invention according to any one of the first to sixth aspects, the previous commutation cycle is divided into four parts, and the three-quarter period from the first to the third is used. The actual phase is estimated by the phase estimation means, and only the last quarter period is corrected according to the phase difference from the target phase. Immediately after the phase is estimated by the phase estimation means Because the commutation timing and commutation cycle can be determined, it is possible to quickly detect the magnitude of load fluctuations, obtain the optimum energization timing and energization period according to the load fluctuation, and follow the load fluctuation. A highly reliable brushless DC motor control device that can improve the performance can be realized.

  In the invention according to claim 8 of the present invention, in the invention according to any one of claims 1 to 7, when the target phase is compared with the actual phase and the phase difference is larger than a predetermined phase difference, the previous shift is performed. Time correction is performed from the flow period according to the phase difference between the target phase and the actual phase, the next commutation period is calculated, and the commutation timing is determined. On the other hand, when it is small, only the time interval of a quarter of the predetermined commutation period is corrected for time, and it becomes possible to detect the magnitude of the load fluctuation, and the commutation timing. A highly reliable control device for a brushless DC motor that can obtain an optimal energization timing according to the load fluctuation every time and can improve the followability to the load fluctuation can be realized.

  According to a ninth aspect of the present invention, in the first to eighth aspects of the invention, the commutation timing is corrected so as to follow the target phase by changing the time correction amount at the time of start-up and operation. Because the rotation is unstable at start-up, an error is likely to occur in the phase estimation, and changing the amount of time correction between start-up and operation causes instability of rotation and step-out. Therefore, a highly reliable brushless DC motor control device that can improve follow-up performance against load fluctuations can be realized.

  In the invention according to claim 10 of the present invention, in the invention according to claims 1 to 9, the time correction amount is changed at the time of start-up and during operation, and the rotation is unstable at the time of start-up, so that the phase Errors in estimation are likely to occur, and by changing the amount of time correction between startup and operation, it is possible to reduce the instability of rotation and out-of-step, and to improve the followability to load fluctuations with high reliability. realizable.

  According to an eleventh aspect of the present invention, in the invention according to any one of the first to tenth aspects, the brushless DC motor control device is mounted on the heat exchange type cooler, and the control means is installed on the inside air path side. Since the relay lead wire for the sensor signal used for connection to the sensor is no longer needed and the work to connect the relay wire is eliminated, it is small and low-cost, and there is no influence of malfunction due to noise on the sensor signal wire. A highly reliable heat exchange type cooler can be realized.

  The invention according to claim 12 of the present invention is the invention according to claims 1 to 11, wherein the brushless DC motor control device is mounted on the ventilation air blower, and the relay lead of the sensor signal becomes unnecessary, Since there is no need to connect the relay line, the size and cost can be reduced, and there is no influence of malfunction due to noise on the sensor signal line, so that a highly reliable ventilation fan can be realized.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
As shown in FIG. 1, the inverter circuit 1 has a three-phase inverter bridge configuration, Q1, Q2, and Q3 are U, V, and W-phase upper arm switching elements. Similarly, Q4, Q5, and Q6 are respectively It is a U, V, W phase lower arm switching element. The switching diodes D1, D2, D3, D4, D5, and D6 are connected to each switching element in parallel. The brushless DC motor 2 includes a rotor 3 and a stator 4, and stator windings L1, L2, and L3 are arranged on the stator 4 so as to have a phase difference of 120 degrees in electrical angle. Between the DC power supply 5 and the switching element, a current detection resistor 6 for detecting the output current of the DC power supply 5 is disposed as shown in the figure. The voltage between the terminals of the current detection resistor 6 is input to an A / D converter 8 built in the microcomputer 7. The phase estimation means 9 calculates a current change rate with respect to time of the current from the current value digitized by the A / D converter 8, and fixes the current change rate of the current value supplied to the inverter circuit 1 stored in advance. The phase is estimated from the phase relationship between the induced voltage induced in the child winding and the voltage applied to the stator winding. The commutation timing determination means 10 compares the phase obtained from the phase estimation means 9 with the target phase, calculates the phase commutation timing of the motor current based on the phase difference, and switching signals for controlling the inverters U +, V + , W +, U−, V−, W−. The drive circuit 11 is driven by energizing the switching elements Q1, Q2, Q3, Q4, Q5, and Q6 every 120 degrees based on the switching signal output from the commutation timing determining means 10.

  The phase estimation means 9, the commutation timing determination means 10, and the drive circuit 11 are built in the microcomputer 7.

  The control device 12 includes an inverter circuit 1, a current detection resistor 6, and a microcomputer 7. The current detection resistor 6 may be a resistor whose voltage at both ends is changed by the flowing current. In this embodiment, the resistor is 50 mΩ, and the voltage between the terminals due to the current flowing through the current detection resistor 6 is A / D. The current value is detected by converting and taking in the converter 8.

  Next, a phase estimation method will be described. FIG. 2A shows a current waveform detected by the current detection resistor in the wide-angle energization of 150 degrees. In the figure, A / D conversion is performed on current values at two arbitrary points of the commutation cycle, that is, I1 and I2, and the ratio of the current value of I2 to the current value of I1 is obtained as a current change rate Ihi by Formula 1. .

Ihi = current value of I2 / current value of I1 (Expression 1)
The current change rate when the phase of the voltage applied to the stator winding with respect to the induced voltage induced in the stator winding is changed from, for example, -30 degrees to 20 degrees with the torque being constant is obtained by Equation 1. Then, the phase relationship between the current change rate and the voltage applied to the stator winding as shown in FIG. 3 is obtained.

  From this phase relationship, in order to reduce the processing load, the phase relationship between the current change rate and the voltage applied to the stator winding as shown in FIG. 4 is simplified and stored in advance. Therefore, the current phase can be obtained from the current change rate obtained by Equation 1 using FIG.

  FIG. 2B shows a current waveform when the commutation timing is early with respect to the target phase. In this case, if the current change rate Ihi obtained by Equation 1 is 1.011, it can be estimated from FIG. 4 that the phase is −5 degrees, and if the target phase is 0 degrees, the phase difference with respect to the target phase is − It is 5 degrees, and it can be determined that the phase is an advance phase with respect to the target phase. By delaying the next commutation timing and commutation period according to the phase difference, the current waveform is brought closer to a broken line, and operation at the target phase is enabled.

  On the other hand, FIG. 2C shows a current waveform when the commutation timing is late with respect to the target phase. A broken line indicates a current waveform in the case of a target phase. In this case, if the current change rate Ihi obtained by Equation 1 is 0.963, it can be estimated from FIG. 4 that the phase is 5 degrees, and if the target phase is 0 degrees, the phase difference with respect to the target phase is 5 degrees. It can be determined that the phase is delayed with respect to the target phase, and the current commutation timing and commutation cycle are advanced according to the phase difference, thereby bringing the current waveform closer to the dashed waveform and Enable driving.

  As a result, it is possible to detect the current flowing through the inverter circuit 1 and estimate the phase, and even if the motor and the control device are separated and the motor lead wire becomes long, it is not affected by the voltage drop due to the lead wire. Highly reliable sensorless driving is possible. Further, as in this embodiment, when the heating element is a mobile base station, the DC power source is often a low-voltage DC power source such as 24V or 48V, and in that case, it is driven with a large current. Therefore, the reliability of current detection is increased and the accuracy of phase estimation is further increased.

  Although the electrical angle for wide-angle energization is 150 degrees, it may be set according to the motor, and the phase stored in advance is in the range of -30 degrees to 20 degrees, but this is also set according to the motor. What is necessary is not to make a difference in the effect.

(Embodiment 2)
The same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. FIG. 5 shows a current waveform detected by the current detection resistor in 150-degree wide-angle energization. In the figure, A / D conversion is performed on current values I1 and I2 at two arbitrary points t1 and t2 in a region of predetermined first timing and second timing in the commutation cycle, and the current value of I1 is Then, the ratio of the current value of I2 is obtained as a current change rate Ihi by Equation 1.

  Similarly, when the torque is constant and the phase of the voltage applied to the stator winding with respect to the induced voltage induced in the stator winding is changed, the current change rate is obtained by Equation 1, and the current change rate And the phase relationship between the voltage applied to the stator winding and stored in advance, and based on the obtained phase, the commutation timing is advanced or delayed, so that Enable driving.

  In this way, by storing the correlation curve in advance, the current phase can be easily obtained from the obtained current change rate, the phase can be detected without requiring complicated calculation, and an inexpensive microcomputer is used. This makes it possible to manufacture a control device for a brushless DC motor that is inexpensive and highly reliable.

(Embodiment 3)
The same parts as those in the first or second embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. FIG. 6 shows a current waveform detected by a current detection resistor in 150-degree wide-angle energization. In the figure, the previous commutation timing is t0, the current commutation timing is t1, and the commutation period from t0 to t1 is T1. It can be confirmed that the energization overlap period and the non-overlap period exist in the period of the energization cycle T1, and the shape of the current waveform is different. The energization overlapping period, the period in which energization does not overlap and the current waveform are specifically shown in FIGS. 19B and 19C.

  In a period in which the energization does not overlap, the first current value I1 at the first timing t11 determined in advance from t0 and the second current value I2 at the second timing t12 are obtained by A / D conversion, and then I1 The ratio of the current value of I2 to the current value of I2 is obtained as a current change rate Ihi using Equation 1.

  As an example, the first timing t11 is an electrical angle of 10 degrees, the second timing t12 is an electrical angle of 30 degrees, and the relationship of the current change rate in each phase is shown by a solid line in FIG. On the other hand, in the energization overlap period, as an example, the relationship of the current change rate in each phase of the first timing t11 at the electrical angle of 30 degrees and the second timing t12 at the electrical angle of 50 degrees is also shown by broken lines. From the figure, the characteristic indicated by the solid line shows a larger change in the current change rate in each phase. The broken line has almost no change. Accordingly, it can be seen that the phase estimation error is smaller when the current value is detected in the period where the current change rate is large and the energization is not overlapped.

  As a result, in the estimation of the phase in wide-angle energization, the current value can be sampled in the non-overlapping period where the current change rate changes relatively greatly, so that a more accurate current change rate can be obtained and the phase estimation accuracy can be obtained. Highly reliable driving can be achieved.

  In the present embodiment, the current change rate is obtained from the current value at the timing of 10 degrees and 30 degrees in electrical angle, and the phase is estimated, but the current value at other timings of 5 degrees and 25 degrees, for example, is also used. Good. In short, it is only necessary to obtain the current change rate at the timing when the current change becomes large in a period in which the energization does not overlap, and there is no difference in the effect.

(Embodiment 4)
The same parts as those in any of Embodiments 1 to 3 are denoted by the same reference numerals, and detailed description thereof is omitted. FIG. 8 shows a current waveform in 150-degree wide-angle energization when driving at a constant rotation speed without load fluctuation. In the figure, the amplitude of the current waveform varies due to the influence of switching element variation, rotor magnet variation, load imbalance, and the like. These variations in current have periodicity and are repeated every rotation at a mechanical angle.

  Therefore, the current change rate for one rotation is stored as a mechanical angle, and the average value is used as the current change rate to estimate the phase.

  For example, in the case of an 8-pole 12-slot brushless DC motor, energization switching corresponding to one rotation in mechanical angle is 24 times. Therefore, the current change rate for 24 times is stored, and the average value Ihia is obtained by Equation 2.

Ihia = (Ihi1 + Ihi2 + Ini3 +... + Ihi24) / 24 (Formula 2)
This can reduce the influence of current variation due to variation in switching elements, variation in rotor magnets, variation due to load imbalance, etc., and enables highly reliable driving that can improve phase estimation accuracy. .

  In the present embodiment, the current change rate for one rotation is stored as a mechanical angle, and the phase is estimated based on the average value, but it may be two rotations or 0.5 rotations. In short, it is only necessary to reduce the influence of variation, and there is no difference in the effect.

(Embodiment 5)
The same parts as those in any of Embodiments 1 to 4 are denoted by the same reference numerals, and detailed description thereof is omitted. FIG. 9 shows a current waveform in 150-degree energization when the load gradually increases. In the figure, since the load becomes heavier every commutation cycle, the phase gradually becomes a lagging phase. When the current waveform one revolution before (indicated by a broken line) is overlapped with the mechanical angle, the shape of the current waveform gradually becomes a lagging phase, and it can be seen more remarkably that the commutation cycle is delayed.

  Therefore, the current change rate is stored in the mechanical angle for one rotation period, the average value of the current change rate for one rotation is obtained by Equation 2, and the latest current change rate is compared with the current change rate before one rotation. When this difference is a predetermined value, for example, when the current change rate is smaller than ± 0.02, it is determined that the load fluctuation is small, and the phase is estimated from the average value of the current change rate of one rotation. On the other hand, when the current change rate is larger than ± 0.02, it is determined that the load fluctuation is large, and the phase is estimated from the latest current change rate.

  For example, when the latest current change rate is 1.024, the average value of the current change rates is 0.989.

  The difference between the two is 0.035, which is larger than a predetermined threshold value ± 0.02, so that it is determined that the load fluctuation is large, and the phase is estimated from the latest current change rate. On the other hand, when the latest current change rate is 0.999, similarly, the difference between the two is 0.01, and it is determined that the load fluctuation is small, and the phase is estimated from the average value of the current change rates. Become.

  As a result, the magnitude of the load fluctuation can be detected, a more accurate current detection rate can be obtained according to the load fluctuation, and a highly reliable brushless DC motor control apparatus capable of improving the phase estimation accuracy can be obtained. .

  In the present embodiment, the difference between the latest current change rate and the current change rate before one rotation is ± 0.02, but a numerical value may be determined according to the motor load, such as ± 0.01 or ± Even if it is 0.03, the effect does not produce a difference.

(Embodiment 6)
The same parts as those in any of Embodiments 1 to 5 are denoted by the same reference numerals, and detailed description thereof is omitted. Based on FIG. 10, a method for correcting the current commutation timing and determining the next commutation cycle will be described. FIG. 10A shows a current waveform when the phase is advanced by advancing the commutation timing. FIG. 10B shows a current waveform when the commutation timing is delayed and the phase is delayed. The previous commutation timing is t0, the current commutation timing is t1, and the current commutation period from t0 to t1 is T1. The phase of the current change rate and the voltage applied to the stator winding is estimated based on FIG. 11, and a correction value α is obtained from the obtained phase. T1 is determined at time t0, but is determined again after obtaining the correction value α, and is obtained from equation (3).

T1 = T1 + α × T1 (Formula 3)
Here, T1 + α × T1 is the value of T1 determined at the time of t0. The commutation timing t1 is corrected based on the T1 determined again.

  When the next commutation timing is t2, and the commutation period T2 from t1 to t2, t2 is determined with T1 obtained at this time as the next commutation period T2, and these series of operations are repeated. Flow timing and commutation cycle are determined.

  For example, when the commutation cycle T1 is 1 ms and the phase is 5 degrees, the correction value α is −1/16, and the current commutation cycle T1 is corrected to 0.9375 ms from Equation 3, and the current commutation timing t1. Is controlled so as to be closer to the target phase by making it earlier than the value determined at the previous commutation timing t0.

  On the other hand, the correction value α when the phase is −5 degrees is 1/16. Similarly, the current commutation cycle T1 is 1.0625 ms according to Equation 3, and the current commutation timing t1 is changed to the previous commutation timing t0. Control is performed so as to approach the target phase by delaying from the value determined in step (1).

  Based on the correction value thus obtained, the current commutation timing is advanced or delayed, thereby enabling operation at the target phase.

  As a result, an optimal commutation timing can always be obtained for each commutation cycle with respect to load fluctuations, and a highly reliable brushless DC motor control device that can improve followability to load fluctuations can be obtained.

  In the present embodiment, a specific example of the phase relationship between the current change rate and the voltage applied to the stator winding and the correction value α as shown in FIG. 11 is shown. What is necessary is just to decide according to a characteristic, and a difference does not arise in the effect.

  In addition, the value of α is set to the same value when determining the timing of t1 and when determining the cycle of T2. However, different values may be used, and these values may be determined in accordance with the characteristics of the motor. There is no difference.

(Embodiment 7)
The same parts as those in any of Embodiments 1 to 6 are denoted by the same reference numerals, and detailed description thereof is omitted. Based on FIG. 12, a method of correcting the current commutation timing and determining the next commutation cycle will be described. FIG. 12A shows a current waveform when the phase is advanced by advancing the commutation timing. FIG. 12B shows a current waveform when the commutation timing is delayed and the phase is delayed. The previous commutation timing is t0, the current commutation timing is t1, the commutation cycle from t0 to t1 is T1, and the time obtained by dividing the commutation cycle T1 into four is T1a. Based on FIG. 13, the phase with the voltage applied to the stator winding is estimated from the current change rate, and the correction value β is obtained based on the obtained phase. T1 is determined at the time t0, but is determined again after obtaining the correction value β, and is obtained from equation (4).

T1 = 3 × T1a + (T1a + β × T1a) (Formula 4)
Here, T1a of 3 × T1a + (T1a + β × T1a) is obtained from the T1 value determined at time t0. The commutation timing t1 is corrected based on the T1 determined again. At this time, by correcting the T1a time from the commutation timing until three-quarters of the commutation cycle T1 to four-fourths, the current commutation timing t1 is advanced or delayed. , Enabling operation at the target phase.

  When the next commutation timing is t2, and the commutation period T2 from t1 to t2, t2 is determined with T1 obtained at this time as the next commutation period T2, and these series of operations are repeated. Flow timing and commutation cycle are determined.

  For example, when the commutation cycle T1 is 1 ms and the phase is 5 degrees, the correction value β is −1/32, and the commutation cycle T2 is 0.992 ms from Equation 4, and the current commutation timing t1 is set to the previous commutation timing t1. Control is performed so as to approach the target phase by advancing the value determined at the flow timing t0.

  On the other hand, the correction value β when the phase is −5 degrees is 1/32, and similarly, the commutation cycle T2 is 1.008 ms according to Equation 4, and the current commutation timing t1 is determined by the previous commutation timing t0. Control is performed so as to approach the target phase by delaying the measured value.

  Based on the correction value thus obtained, the next commutation timing is advanced or delayed to enable operation at the target phase.

  As a result, an optimal commutation timing can always be obtained for each commutation cycle with respect to load fluctuations, and a highly reliable brushless DC motor control device that can improve followability to load fluctuations can be obtained.

  In the present embodiment, specific examples of the phase relationship between the current change rate and the voltage applied to the stator winding and the correction value β as shown in FIG. 13 are shown. What is necessary is just to decide according to a characteristic, and a difference does not arise in the effect.

  In addition, the value of β is set to the same value when determining the timing of t1 and when determining the period of T2, but different values may be used, and these values may be determined in accordance with the characteristics of the motor. There is no difference.

(Embodiment 8)
The same parts as those in any of Embodiments 1 to 7 are denoted by the same reference numerals, and detailed description thereof is omitted. A method of correcting the current commutation timing and determining the next commutation cycle will be described. When the target phase is compared with the actual phase and is larger than a predetermined phase difference, the current commutation timing is calculated by Equation 3 according to the phase difference between the target phase and the actual phase from the previous commutation period. Is corrected to determine the next commutation cycle. On the other hand, when it is smaller than the phase difference, the current commutation timing is calculated by Equation 4, and the time from the commutation timing until three-quarters of the commutation period has elapsed until four-quarters has elapsed is corrected. Then, the current commutation period at this time is determined as the next commutation period, and the current commutation timing is advanced or delayed, thereby enabling operation at the target phase.

  For example, when the target phase and the actual phase difference are larger than 10 degrees, the calculation is performed by Expression 3, and when the phase difference is less than 10 degrees, the current commutation timing is corrected by Expression 4. Therefore, when the phase difference from the target phase is 10 degrees, the commutation cycle T1 is 1 ms, and the correction value α when the phase is 10 degrees is −1/16. From Equation 3, the commutation cycle T1 is 0.9375 ms. The current commutation timing t1 is controlled to be closer to the target phase by making the current commutation timing t1 earlier than the value determined at the previous commutation timing t0.

  On the other hand, when the phase difference from the target phase is less than 10 degrees, the commutation period T1 is 1 ms, and when the phase is 5 degrees, the correction value β is −1/32. The current commutation timing t1 is corrected to 992 ms, and control is performed so as to approach the target phase by advancing the current commutation timing t1 from the value determined by the previous commutation timing t0.

  Based on the correction value thus obtained, the current commutation timing is advanced or delayed, thereby enabling operation at the target phase.

  As a result, it is possible to detect the magnitude of the load fluctuation, obtain the optimum energization timing according to the load fluctuation at each commutation timing, and improve the followability to the load fluctuation with high reliability. A control device for the DC motor is obtained.

(Embodiment 9)
The same parts as those in any of Embodiments 1 to 8 are denoted by the same reference numerals, and detailed description thereof is omitted.

  A method for correcting the current commutation timing and determining the next cycle will be described with reference to FIG. At startup and during operation, the commutation timing is corrected so as to follow the target phase by changing the correction value α as shown in FIG.

  For example, when the commutation period T1 is 1 ms and the phase is 10 degrees at the time of start-up, the correction value α is −2/16, and the commutation period T1 is corrected to 0.875 ms from Equation 3, and this commutation is performed. Control is performed so that the timing t1 is made earlier than the value determined at the previous commutation timing t0, and the commutation period is set to the next commutation period to approach the target phase.

  On the other hand, during operation, the correction value α when the phase is 10 degrees is 1/16. Similarly, the commutation cycle T1 is corrected to 0.9375 msms by Equation 3, and the current commutation timing t1 is changed to the previous commutation timing t1. Control is performed so as to approach the target phase by making this commutation cycle the next commutation cycle earlier than the value determined at the flow timing t0.

  Based on the correction value thus obtained, the current commutation timing is advanced or delayed, thereby enabling operation at the target phase.

  As a result, the rotation is unstable at start-up, so errors are likely to occur in the phase estimation.By changing the time correction value between start-up and operation, it is possible to reduce instability of rotation and step-out. Thus, a highly reliable brushless DC motor control device that can improve the followability to load fluctuations can be obtained.

  In the present embodiment, specific examples of the phase relationship between the current change rate and the voltage applied to the stator winding and the correction value α as shown in FIG. 15 are shown. What is necessary is just to decide according to a characteristic, and a difference does not arise in the effect.

(Embodiment 10)
The same parts as those in any of Embodiments 1 to 9 are denoted by the same reference numerals, and detailed description thereof is omitted. The commutation timing is corrected so as to follow the target phase by changing to 120-degree energization at start-up and changing to wide-angle energization during operation.

  FIG. 15 shows a current waveform at 120 degrees energization. FIG. 16 shows an example of the rate of change in current at 120 degrees energization. From the figure, the phase estimation means and the commutation timing determination means can be realized in exactly the same way as the wide-angle energization.

  Since wide-angle energization provides energization overlap periods, control is more complicated than 120-degree energization, and in particular, there is no phase overlap period because rotation is unstable during start-up and errors tend to occur in energization overlap periods and phase estimation. Highly reliable brushless DC motor that can be started by 120 degrees energization and can be reduced to instability of rotation and step-out by switching to wide angle energization at the time of stable operation. Can be obtained.

(Embodiment 11)
As a device equipped with a blower equipped with a brushless DC motor, a heat exchange type cooler and a ventilation blower can be cited. As an example, an embodiment in a heat exchange type cooler will be described below.

  The same parts as those in any of Embodiments 1 to 10 are denoted by the same reference numerals, and detailed description thereof is omitted. As shown in FIG. 17, a brushless DC motor control device is mounted on a heat exchange type cooler.

  In the figure, reference numeral 25 denotes an outdoor sensorless DC brushless motor, and by rotating the outdoor blower 13, the ambient air around which a heating element storage box 14 such as a mobile phone exchange base station is installed is cooled by heat exchange cooling. The air is sucked in from the outside air inlet 16 at the lower part of the machine 15, passed through the heat exchange element 17, and then discharged from the outside air outlet 18 at the upper part of the heat exchange type cooler 15. Reference numeral 19 denotes an indoor brushless DC motor, which rotates the indoor blower 20 to suck the heated inside air inside the heating element storage box 14 from the inside air inlet 21 at the top of the heat exchange type cooler 15, After passing through the exchange element 17, the air is discharged from the inside air discharge port 22 below the heat exchange type cooler 15. The movement of the outside air caused by the rotation of the outdoor blower 13 is indicated by a black arrow a, and the movement of the indoor air caused by the rotation of the indoor blower 20 is indicated by an arrow b indicated by white. Heat is exchanged when the cooled outside air and the heated indoor air pass through the heat exchange element 17, the outside air is heated and discharged into the atmosphere, and the indoor air is cooled and returned to the indoor side. The inside of the body storage box 14 can be cooled. In the heat exchange element 17, the outside air passage and the inside air passage are blocked, and the air in the outside air passage does not flow into the inside air passage of the heat exchange type cooler 15. Reference numeral 23 denotes a control box installed in the inside air passage of the heat exchange type cooler 15, and a control device 12 for driving the sensorless DC brushless motor 25 on the outdoor side is installed therein. The control device 12 is supplied with low-voltage DC power from a low-voltage DC power source 5 installed in the heating element storage box 14, and a sensorless DC brushless motor 25 on the outdoor side is passed from the control device 12 through the drive lead wire 24. Driving. The control box 23 is also provided with an indoor inverter circuit (not shown) that drives the indoor brushless DC motor 19 to operate the indoor fan 20.

  This eliminates the need for a relay lead wire for the sensor signal used for connection with the control device installed on the side of the inside air path, so that there is no influence of malfunction due to noise on the sensor signal wire, and a highly reliable brushless DC motor. In addition, the lead wire is unnecessary and the work of connecting the relay line is eliminated, so that a low-cost heat exchange type cooler can be obtained.

  In addition, by installing a brushless DC motor control device in a blower equipped with a brushless DC motor, the relay lead wire for the sensor signal becomes unnecessary, the work of connecting the relay wire is eliminated, and the size and cost are reduced. Thus, there is no influence of malfunction due to noise on the sensor signal line, and a highly reliable ventilation fan can be obtained.

1 is a block diagram of a brushless DC motor control device according to a first embodiment of the present invention. Explanatory drawing of the phase estimation method by the same phase estimation means Correlation characteristics diagram showing in-phase and current change rate Correlation diagram with simplified phase and current change rate Explanatory drawing of the phase estimation method by the phase estimation means of Embodiment 2 of this invention Explanatory drawing of the phase estimation method by the phase estimation means of Embodiment 3 of this invention Correlation characteristics diagram showing in-phase and current change rate Explanatory drawing of the phase estimation method by the phase estimation means of Embodiment 4 of this invention Explanatory drawing of the phase estimation method by the phase estimation means of Embodiment 5 of this invention Explanatory drawing of the determination method of the commutation timing by the commutation timing determination means of Embodiment 6 of this invention Correlation diagram with simplified phase and current change rate Explanatory drawing of the determination method of the commutation timing by the commutation timing determination means of Embodiment 7 of this invention Correlation diagram with simplified phase and current change rate The correlation diagram which simplified the same phase and current change rate of Embodiment 9 of this invention Explanatory drawing of 120 degree energization of Embodiment 10 of this invention Correlation characteristics diagram showing in-phase and current change rate Schematic sectional view showing the structure of a heat exchange type cooling machine equipped with a control device for a brushless DC motor according to Embodiment 12 of the present invention. Schematic sectional view showing the structure of a conventional heat exchange type cooler Diagram of a conventional brushless DC motor wide-angle energization control device Explanatory drawing of the same wide-angle control energization ((a) diagram showing magnetic pole position detection signal, (b) diagram showing switching signal, (c) diagram showing current waveform detected by current detection means) Diagram of a conventional brushless DC motor sensorless control device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inverter circuit 2 Brushless DC motor 3 Rotor 4 Stator 5 DC power supply 6 Current detection resistance 7 Microcomputer 8 A / D converter 9 Phase estimation means 10 Commutation timing determination means 11 Drive circuit 12 Controller 15 Heat exchange type cooling Machine 19 Indoor Brushless DC Motor 25 Outdoor Sensorless DC Brushless Motor

Claims (12)

A brushless DC motor having a rotor and a stator winding connected via an inverter circuit in which a plurality of switching elements are bridge-connected to a DC power supply is switched on and off for the switching elements of the inverter circuit. In a control device that is rotated by wide-angle energization by providing an energization overlap period with an electrical angle longer than 120 degrees, a current detection resistor that detects current supplied from the DC power supply to the inverter circuit, and output from the current detection resistor Phase estimation for estimating the phase of the voltage applied to the stator winding with respect to the induced voltage induced in the stator winding of the brushless DC motor stored in advance based on the current waveform obtained from the current value obtained And a commutation tag so that the phase estimated by the phase estimation means follows a predetermined target phase. Control device for a brushless DC motor and having a commutation timing determining means for determining a timing. The phase estimating means calculates a ratio of current values at predetermined first and second timings as a current change rate in the current waveform supplied from the DC power supply to the inverter circuit, and fixes the current change rate. 2. The brushless DC motor control device according to claim 1, wherein a correlation curve of a phase with a voltage applied to the child winding is stored in advance. The phase estimation means obtains a first current value at a predetermined first timing and a second current value at a second timing in a period in which the energization is not overlapped but is not the energization overlapping period, and the first The brushless DC motor control device according to claim 2, wherein the ratio of the second current value to the current value is calculated as a current change rate. The phase estimation means stores the current change rate in a mechanical angle for one rotation period, obtains an average value of the current change rate of one rotation, and can estimate the phase from the average value of the current change rate of one rotation. The brushless DC motor control device according to claim 3. The phase estimation means stores the current change rate in a mechanical angle for one rotation period, obtains an average value of the current change rate of one rotation, compares the latest current change rate with the current change rate before one rotation, When the difference is smaller than a predetermined value, the phase is estimated from the average value of the current change rate of one rotation, while when larger than the predetermined value, the phase is estimated from the latest current change rate. 4. The brushless DC motor control device according to claim 3, wherein the control device is capable of being used. The commutation timing determination means performs time correction on the commutation period according to the phase difference between the phase estimated by the phase estimation means and the target phase, and determines the current commutation timing and the next commutation period. The brushless DC motor control device according to any one of claims 1 to 5, wherein: The commutation timing determination means divides the current commutation cycle into four parts, estimates the phase by the phase estimation means by a period of three quarters from the previous commutation timing, and according to the phase difference from the target phase. 7. The brushless DC motor control apparatus according to claim 1, wherein only the last quarter period is corrected. The commutation timing determining means compares the phase estimated by the phase estimating means with the target phase, and when the phase difference is larger than a predetermined phase difference, the commutation timing determining means compares the target phase with the actual phase from the current commutation period. Time correction is performed according to the phase difference, the next commutation cycle is calculated, and the commutation timing is determined. On the other hand, when the time is small, only the time interval of a quarter of a predetermined commutation period is corrected for time, the next commutation period is calculated, and the commutation timing is determined. The control device for a brushless DC motor according to any one of 7 to 7. The brushless DC motor control device according to any one of claims 6 to 8, wherein the commutation timing determining means changes a time correction amount at the time of start-up and during operation. 10. The device according to claim 1, wherein the switching element is turned on by a rectangular wave energization without an energization overlapping period by setting the ON period of the switching element to 120 degrees in electrical angle, and is rotated by a wide angle energization in operation. A control device for a brushless DC motor according to claim 1. A heat exchange type cooler equipped with the brushless DC motor control device according to any one of claims 1 to 10. A ventilation blower equipped with the brushless DC motor control device according to any one of claims 1 to 11.

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