JP5011815B2 - Brushless DC motor control device and ventilation blower equipped with the same - Google Patents

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 cooler used for cooling a device such as a mobile base station. In a control device that rotates at a motor, the motor current commutation timing is controlled by sensorless control without using a position sensor, and the magnitude of the motor current is limited, and the protection control does not involve demagnetization of the magnet due to overcurrent. It is.

  Conventionally, 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, cost reduction, downsizing, and high reliability of ventilation fans and brushless DC motors are required.

  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 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 blower or the like is driven.

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

  As shown in the drawing, the heated air in the heating element storage box 101 (hereinafter referred to as “inside air”) is a chamber in which the indoor brushless DC motor 104 is mounted from the inside air inlet 103 of the heat exchange type cooler 102. The air is sucked by the inner blower 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 outdoor air sucked from the outdoor air suction port 110 by the outdoor air blower 109 equipped with the outdoor brushless DC motor 108 passes through the heat exchange element 106 and is then discharged again from the outdoor air outlet 111 to the outside air. . 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 brushless DC motors incorporating magnetic pole sensors such as Hall elements, 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.

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 and the field induced in the stator winding while driving the motor. Also known is a sensorless control system 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 DC power supply to the inverter circuit with respect to time (for example, Patent Document 2).

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

  As shown in FIG. 16, 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. Each switching element is connected in parallel with free-wheeling diodes D1, D2, D3, D4, D5, and D6. 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. Between the DC power supply 116 and the switching element, a current detection resistor 121 for detecting the current value of the brushless DC motor supplied from the DC power supply 116 is arranged as shown. 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 arithmetic 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 with respect to time of the current output from the DC power supply 116 is detected, the position of the magnetic pole of the rotor is estimated based on the time when the polarity changes, that is, the time when the current becomes minimum, and the detection signal The polarity reversal time is measured based on the above, and the magnetic pole position of the rotor is estimated from the time to obtain the commutation timing.

  In addition, overcurrent protection for brushless DC motors is provided with a current detection resistor that detects the current supplied from the DC power supply to the inverter circuit, and the voltage between the terminals of the current detection resistor and the reference voltage are detected by a comparator. A control method is known that performs control so that the switching element is turned off and the current does not exceed the current threshold when the threshold value is larger (for example, see Patent Document 3).

  Hereinafter, the overcurrent protection operation of the brushless DC motor will be described with reference to FIG.

  As shown in FIG. 17, the voltage between the terminals of the current detection resistor for detecting the current supplied from the DC power source to the inverter circuit and the current threshold, that is, the reference voltage are shown. The comparator compares the voltage across the current detection resistor with the reference voltage. When the reference voltage is exceeded, the switching element is turned off, the motor current is controlled to increase, and the motor current is controlled to reduce overcurrent. Is to do.

JP 2001-156478 A JP-A-8-126379 JP-A-6-351285

In such a conventional configuration, when a magnetic sensor is mounted on a brushless DC motor, 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 noise. In addition to being susceptible to malfunctions, malfunctions are difficult, wiring work in the heat exchange type cooling machine is complicated and time-consuming, and there is a problem that it becomes a high-cost cooling machine, and the magnetic sensor is built into the DC motor. However, there is a problem that the size of the DC motor becomes thick and the apparatus cannot be miniaturized.

  In the case of sensorless driving of a brushless DC motor, the commutation timing is determined by estimating the magnetic pole position on the assumption that the time when the current value becomes minimum, that is, the time when the induced voltage becomes maximum, is determined. In the case of, the current waveform is different and the current value is not minimized. Therefore, the time at which 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.

  Also, if the current value supplied to the inverter circuit changes significantly due to disturbances such as acceleration at start-up or sudden voltage fluctuations of the DC power supply, excessive current flows to the inverter circuit or brushless DC motor, causing damage to the switching element. Further, there is a problem that the efficiency of the brushless DC motor is reduced by demagnetizing the magnet of the rotor. In order to prevent this, if protection control is performed so that a current exceeding a certain value does not flow, the current waveform will be deformed, resulting in an increase in torque pulsation and the occurrence of noise due to resonance with the device. It was. In addition, it is difficult to accurately estimate the magnetic pole position, and there is a problem that the possibility of the step-out causing the brushless DC motor to stop increases or the current is increased to reduce the efficiency.

  Further, in the case of overcurrent protection of a brushless DC motor, since a comparator circuit is necessary, parts and circuit space are required, and there are problems in cost reduction and size reduction.

  Therefore, there is a need for a brushless DC motor control device that can accurately estimate the magnetic pole position, that is, the phase, protect the overcurrent, perform sensorless driving with wide-angle energization, and reduce the size, cost, and noise. .

  Here, the applicant of the present invention invented a sensorless drive circuit for a DC brushless motor described in Japanese Patent Application No. 2006-026825, wherein the energization period of the rectangular wave is increased to 120 degrees or more and rotated by wide-angle energization provided with an energization overlap period. . Based on the current waveform obtained from the current value supplied from the DC power supply to the inverter circuit, the phase of the voltage applied to the stator winding relative to the induced voltage induced in the stator winding of the brushless DC motor is estimated. The commutation timing is controlled so as to follow the target phase. By eliminating the sensor signal lead wires, the operation reliability is improved, the cost is reduced and the apparatus is downsized, the ripple of the drive torque is reduced, and the vibration and noise are reduced.

  The operation will be described below with reference to FIGS. As shown in FIG. 18, a current detection resistor 121 for detecting the current value supplied from the DC power supply 116 to the inverter circuit 117 is arranged. 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 phase estimation means 126 calculates a current change rate with respect to time of the current from the current value digitized by the A / D converter 123, and fixes the current change rate of the current value supplied to the inverter circuit 117 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 127 compares the phase obtained from the phase estimation means 126 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 125 switches the switching elements Q1, Q2, Q3, Q4, Q5, and Q6 based on the switching signal output from the commutation timing determining means 127, and is driven by wide-angle energization of 150 degrees.

  FIG. 19A shows specific U +, V +, W +, U−, V−, and W− switching signals, energization periods, energization overlap periods, and non-overlap periods of energization with a 150-degree energization period. Is shown. FIG. 19B shows a specific current waveform detected by the current detection resistor. The current waveform has periodicity, and becomes one cycle at an electrical angle of 60 degrees. In one cycle period, there are alternating energization periods and non-overlap periods.

  By adopting such a configuration, the brushless DC motor control device does not require a complicated phase estimation circuit, and can be driven sensorlessly by wide-angle energization using an inexpensive microcomputer. It was possible to reduce the noise. 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. Therefore, even when the load fluctuation is large due to disturbance or the like, the step-out does not occur, so that the reliability is high and the efficiency is high. 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 could be specifically made.

  The present invention solves such a conventional problem and further improves the function, and is supplied to the inverter circuit due to disturbance such as load fluctuation at start-up and sudden voltage fluctuation of the DC power supply due to power supply noise. Even when the current value fluctuates significantly, it is possible to prevent the switching element from being damaged or the magnet of the rotor from being demagnetized to reduce the efficiency of the brushless DC motor, and noise can be generated or stepped out. An object of the present invention is to provide a highly reliable wide-angle energization sensorless drive brushless DC motor control apparatus that can prevent the above-described problem and eliminates the need for a comparator circuit and that can be reduced in size, cost, and noise.

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, rotating the on-time period by 120 degrees or more in electrical angle and providing energization overlap period to rotate by wide-angle energization, the DC power source to the inverter circuit In a current detection resistor for detecting a supplied current and a current waveform obtained from a current value output from the current detection resistor, predetermined first and second periods of non-overlapping periods other than the energization overlapping period Of the current change rate, which is the ratio of the current value at the timing, and the induced voltage induced in the stator winding The phase relationship between the voltage applied to the stator winding is stored in advance, and the phase estimation for estimating the phase between the induced voltage induced in the stator winding and the voltage applied to the stator winding from the phase relationship. Means, commutation timing determining means for determining commutation timing so that the phase estimated by the phase estimation means follows a predetermined target phase, and a current value output from the current detection resistor is determined in advance. The brushless DC motor control apparatus includes current limiting means for controlling a voltage applied to the motor so as not to exceed the current limit value .

As a result, the current value flowing through the inverter circuit is directly detected as a current value from the current detection resistor, so that the phase in the wide-angle energization can be accurately detected and the current does not exceed a predetermined current threshold value. A control device for a brushless DC motor that can control the voltage applied to the motor and that can be reduced in size, cost, and noise without requiring a comparator circuit is obtained.

  Another means is to change the voltage value for decreasing the voltage applied to the motor according to the difference when the current flowing through the inverter circuit is large with respect to a predetermined current threshold. is there.

  As a result, the voltage value that lowers the voltage applied to the motor can be changed depending on the magnitude of the current exceeding the current threshold, and the period during which excessive current continuously flows to the motor due to sudden load fluctuations, etc. A highly reliable brushless DC motor control device that can be shortened, makes it difficult to damage the switching element and demagnetize the rotor magnet, and prevent the efficiency of the brushless DC motor from being lowered can be obtained.

  The other means controls the first threshold value determined in advance by the maximum value of the current flowing through the inverter circuit.

  As a result, since the current waveform can be accurately detected without being deformed, the magnetic pole position can be accurately estimated, and a highly reliable brushless DC motor control device capable of preventing a reduction in the efficiency of the brushless DC motor can be obtained.

  The other means controls the first threshold value determined in advance by the average value of the current flowing through the inverter circuit.

  As a result, since the current waveform can be accurately detected without being deformed, the magnetic pole position can be accurately estimated, and a highly reliable brushless DC motor control device capable of preventing a reduction in the efficiency of the brushless DC motor can be obtained.

  The other means controls the first threshold value determined in advance by the maximum value of the current flowing in the inverter circuit at the start-up and by the average value of the current during operation. The control is changed between startup and operation.

  As a result, the current is suppressed at the maximum current value during startup when there is a high risk of damage to the switching element or the rotor magnet demagnetizing. Therefore, it is possible to obtain a highly reliable brushless DC motor control device that can prevent excessive current from being continuously generated at the time of start-up and obtain a sufficient start-up torque.

  The other means controls the first threshold value determined in advance by the average value of the current flowing in the inverter circuit during operation, and when the predetermined current threshold value is exceeded, The control is performed according to the maximum value of the current, and the control is changed according to the change of the motor load.

  As a result, when the current increases and exceeds the current threshold due to sudden load fluctuations, etc., the current can be suppressed at the maximum current value, and the period during which excessive current continues to flow in the motor is shortened. Thus, a highly reliable brushless DC motor control device can be obtained.

  The other means provides a second current threshold value that is larger than the predetermined first current threshold value, and when the current flowing through the inverter circuit exceeds the second current threshold value, The current is shut down so that the current does not increase beyond the second current threshold.

  As a result, when the current greatly increases due to load fluctuation or the like and exceeds the second current threshold, the switching element is turned off to shut down the current. Can be prevented, and a highly reliable brushless DC motor control device capable of reliably preventing an excessive current from flowing through the motor can be obtained.

  The other means provides a second current threshold value that is larger than the predetermined first current threshold value, and when the current flowing through the inverter circuit exceeds the second current threshold value, The voltage value that lowers the voltage applied to the motor by shutting down the current is changed to be larger than the value that is changed by a predetermined first current threshold value.

  As a result, when the current greatly increases due to load fluctuation or the like and exceeds the second current threshold, the switching element is turned off to shut down the current. Since the voltage value for reducing the voltage applied to the motor is changed to be larger than the value that is changed by the predetermined first current threshold value, an excessive current surely flows to the motor. Thus, a highly reliable brushless DC motor control device capable of preventing the problem and continuing the driving can be obtained.

  Another means is to stop the voltage applied to the motor when the current flowing through the inverter circuit exceeds a predetermined second threshold and the timing is earlier than the predetermined timing. It is a thing.

  This makes it possible to stop the supply of motor voltage and eliminate the motor current when the motor suddenly restrains or the current value suddenly increases due to a sudden change in the voltage of the DC power supply. It is possible to prevent a brushless DC motor from deteriorating due to breakage or demagnetization of a rotor magnet, and to obtain a highly reliable brushless DC motor control device capable of reliably preventing an excessive current from flowing through the motor. .

  Another means is to stop the voltage applied to the motor when the current value used for phase estimation exceeds a predetermined second current value.

  This makes it possible to stop the supply of motor voltage and eliminate the motor current when the motor suddenly restrains or the current value suddenly increases due to a sudden change in the voltage of the DC power supply. It is possible to prevent a brushless DC motor from deteriorating due to breakage or demagnetization of a rotor magnet, and to obtain a highly reliable brushless DC motor control device capable of reliably preventing an excessive current from flowing through the motor. .

  Another means is that the 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 obtained.

  According to the present invention, in a sensorless drive with wide-angle energization, if there is a significant fluctuation in the current value supplied to the inverter circuit due to a disturbance such as acceleration at start-up or sudden voltage fluctuation of the DC power supply, The rotor magnet can be demagnetized to prevent the efficiency of the brushless DC motor from being reduced, noise generation and step-out can be prevented, and a comparator circuit is not required, making it compact, low cost and low noise. It is possible to provide a highly reliable wide-angle energization sensorless drive brushless DC motor control device and ventilation blower, for example, a heat exchange type cooler.

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 ((a) current waveform at target phase, (b) current waveform at leading phase, (c) current waveform at lagging phase) Correlation characteristics between phase and current change rate Correlation diagram with simplified phase and current change rate Explanatory drawing of current limiting method by current limiting means Explanatory drawing of the phase estimation method by the phase estimation means of Embodiment 2 of this invention Explanatory drawing which shows the difference at the time of estimating in the period which overlaps with the period when the electricity supply does not overlap by the phase estimation means of Embodiment 2 of this invention Explanatory drawing of the current limiting method by the current limiting means of Embodiment 3 of the present invention Explanatory drawing of the current limiting method by the current limiting means of Embodiment 4 of this invention Explanatory drawing of the current limiting method by the current limiting means of Embodiment 5 of the present invention Explanatory drawing of the current limiting method by the current limiting means of Embodiment 8 of this invention 10 is an explanatory diagram of a current limiting method by a current limiting means according to the tenth embodiment of the present invention (when (a) is later than a predetermined timing, (b) is earlier than a predetermined timing) Embodiment 11 of the Present Invention An explanatory diagram of a current limiting method by current limiting means Schematic sectional view showing the structure of a heat exchange type cooler 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 Block diagram of a conventional brushless DC motor control device Explanatory diagram of conventional current limiting method Block diagram of a sensorless drive circuit of a DC brushless motor rotated by wide-angle energization in Japanese Patent Application No. 2006-026825 Illustrations of specific waveforms of wide-angle energization having the 150-degree energization period ((a) switching signal, (b) current waveform detected by current detection resistor)

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 In the current waveform obtained from the detection resistor and the current value output from the current detection resistor, the ratio of the current value at the first and second timings determined in advance in the non-overlapping period other than the energization overlapping period Phase relationship between a certain current change rate and the voltage applied to the stator winding with respect to the induced voltage induced in the stator winding Preliminarily stored, phase estimation means for estimating the phase of the voltage applied to the stator winding with respect to the induced voltage induced in the stator winding from this phase relationship, and the phase estimated by the phase estimation means in advance A commutation timing determining means for determining a commutation timing so as to follow a predetermined target phase; and a current value output from the current detection resistor is applied to the motor so as not to exceed a predetermined current limit value. Current limiting means for controlling the voltage to be detected, the current flowing through the inverter circuit is detected to estimate the phase, and applied to the motor so as not to exceed a current exceeding a predetermined current threshold The voltage can be controlled, and it is possible to achieve both reliable phase estimation and current limitation. It is possible to detect the current value directly from the detection resistor, estimate the phase, and control the voltage applied to the motor so that the current does not exceed a predetermined current threshold. A brushless DC motor control device that can be made compact, low cost and low noise can be realized.

The invention according to claim 2 of the present invention, in the invention described in claim 1, the phase estimation means, the current value outputted from the current sensing resistor, a period which does not overlap the non energized by energizing the overlap period, predetermined The ratio of the current values at the first and second timings is calculated as a current change rate, and a correlation curve between the current change rate and the phase of the voltage applied to the stator winding is stored in advance.

  As a result, a highly reliable brushless DC motor capable of accurately detecting a phase in wide-angle energization and controlling a voltage applied to the motor so that the current does not exceed a predetermined current threshold value. The control device can be realized.

According to a third aspect of the present invention, there is provided the motor according to any one of the first to second aspects, wherein the motor is provided in accordance with a difference between a predetermined current threshold and a current flowing through the inverter circuit. The voltage value that lowers the applied voltage is changed, and the voltage value that lowers the voltage applied to the motor can be changed according to the magnitude of the current exceeding the current threshold, A highly reliable brushless DC motor that can shorten the period during which excessive current continuously flows through the motor due to sudden load fluctuations, etc., and makes it difficult to damage the switching element and demagnetize the rotor magnet. The control device can be realized.

According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the control is performed by the maximum value of the current flowing through the inverter circuit, and the current waveform is not deformed. Therefore, a highly reliable control device for a brushless DC motor that can accurately estimate the magnetic pole position and prevent a reduction in the efficiency of the brushless DC motor can be realized.

The invention according to claim 5 of the present invention is such that, in the invention according to any one of claims 1 to 3 , the control is performed by the average value of the current flowing through the inverter circuit, and variation is caused by averaging. Therefore, a highly reliable brushless DC motor control device that can stably suppress the motor current and prevent a reduction in motor efficiency can be realized.

According to the sixth aspect of the present invention, in the invention according to any one of the first to fifth aspects, the control is performed by the maximum value of the current flowing through the inverter circuit at the time of starting, and the average value of the current is determined during the operation. Control is performed so that the control is changed between startup and operation. At startup, when there is a high risk of breakage of the switching element or demagnetization of the rotor magnet, the current is suppressed at the maximum value of the current during operation. Can stably suppress the motor current with less variation in current value, prevent excessive current from being continuously generated at the start, and obtain a sufficient start torque. A high brushless DC motor control device can be realized.

According to a seventh aspect of the present invention, in the invention according to any one of the first to third aspects, during operation, control is performed based on an average value of a current flowing through the inverter circuit, and a predetermined current threshold value is set. When exceeded, control is performed according to the maximum value of the current, and the control is changed according to the change of the motor load. The current increased due to a sudden load fluctuation and exceeded the current threshold. In this case, it is possible to realize a highly reliable brushless DC motor control device that can suppress the current with the maximum value of the current and shorten the period during which excessive current continuously flows in the motor.

According to an eighth aspect of the present invention, there is provided an inverter according to any one of the fourth to seventh aspects, wherein a second current threshold value larger than a predetermined first current threshold value is provided, and the inverter When the current flowing through the circuit exceeds the second current threshold value, the current is shut down so that no current exceeding the second current threshold value flows. When greatly increased and exceeds the second current threshold, the switching element can be turned off to shut down the current so that no current exceeding the second current threshold flows. A reliable brushless DC motor control device that can reliably prevent an excessive current from flowing through the motor can be realized.

According to a ninth aspect of the present invention, in the invention according to any one of the fourth to eighth aspects, when the current flowing through the inverter circuit exceeds the second current threshold value, the current is shut down to Control is performed so that the current does not become larger than the current threshold value of 2, and the voltage value for lowering the voltage applied to the motor is changed to be larger than the value that is changed by the predetermined first current threshold value. If the current greatly increases due to fluctuations in the power supply voltage and exceeds the second current threshold value, the switching element is turned off and the current is shut down. The phase estimation means is configured to change larger than the value to be changed at the determined first current threshold value, to quickly reduce the current flowing through the inverter circuit so that the current waveform is not deformed. This ensures reliable phase estimation, eliminates the deformation of the current that flows through the inverter circuit quickly even if overcurrent protection works, and ensures reliable phase estimation even when overcurrent protection works. A control device for a DC motor can be realized.

According to a tenth aspect of the present invention, in the invention according to the fourth to ninth aspects, a second threshold value larger than the first threshold value determined in advance is provided, and the current flowing through the inverter circuit If the timing exceeds the second threshold, if the timing is earlier than the predetermined timing, the motor is stopped, and the motor is locked suddenly or the voltage of the DC power supply changes suddenly. If the current value suddenly increases, the motor voltage supply can be stopped to eliminate the motor current, and the efficiency of the brushless DC motor can be reduced by breaking the switching element or demagnetizing the rotor magnet. Therefore, it is possible to realize a highly reliable brushless DC motor control device that can reliably prevent an excessive current from flowing through the motor.

According to an eleventh aspect of the present invention, in the invention according to any one of the fourth to tenth aspects, the flow restricting means provides a second threshold value larger than a predetermined first threshold value, When the current flowing through the inverter circuit exceeds the second threshold during the period of estimating the motor, the motor is stopped, and the motor current value is greatly increased due to a sudden voltage fluctuation of the DC power supply. If it increases, the motor can be stopped, the switching element can be damaged, the rotor magnet can be demagnetized and the efficiency of the brushless DC motor can be prevented from being lowered, and an excessive current can be reliably prevented from flowing through the motor. A highly reliable brushless DC motor control device can be realized.

A twelfth aspect of the present invention is the invention according to any one of the first to eleventh aspects, wherein the brushless DC motor control device is mounted on a ventilation fan, for example, a heat exchange type cooler. The relay lead wire for the sensor signal used for connection with the control means installed on the air-airway side becomes unnecessary, and the work of connecting the relay wire is eliminated, so that the size and cost are reduced, and noise to the sensor signal wire is eliminated. Therefore, a highly reliable ventilation blower, for example, a heat exchange type cooler 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. Each switching element is connected in parallel with free-wheeling diodes D1, D2, D3, D4, D5, and D6. 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 current limiting means 11 compares the current value digitized by the A / D converter 8 with a predetermined current threshold value. When the current threshold value is exceeded, the switching signal is turned off. U +, V +, W +, U−, V−, W− are controlled to suppress an increase in motor current and to reduce the motor current to perform overcurrent protection.

  The drive circuit 12 switches the switching elements Q1, Q2, Q3, Q4, Q5, and Q6 based on the switching signal output from the current control means 11, and is driven by wide-angle energization of 150 degrees.

  The phase estimation means 9, the commutation timing determination means 10, the current control means 11, and the drive circuit 12 are built in the microcomputer 7.

  The control device 13 includes an inverter circuit 1, a current detection resistor 6, and a microcomputer 7.

  Next, a phase estimation method will be described. FIG. 2 (a) shows a current waveform detected by the current detection resistor at 150 degrees energization. In the figure, the current values at two arbitrary points of the commutation cycle, that is, I1 and I2, are A / D converted, 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, 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 1.012, 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 in accordance with 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 is advanced according to the phase difference, thereby making the current waveform closer to the dashed waveform and enabling operation at the target phase. To do.

  Next, a current limiting method will be described. FIG. 5 shows a current waveform detected by the current detection resistor at 150 degrees energization. In the figure, when the current value at one point at any timing other than detecting the phase, that is, I3 is A / D converted and compared with the current threshold value Ia, the current value becomes larger than the current threshold value Ia. Control is performed so that the current is prevented from increasing and the current threshold value Ia is not exceeded by decreasing the duty and decreasing the motor applied voltage Vm for each period of 60 degrees in one cycle. When the current waveform when current limitation is not performed is indicated by a dotted line, it can be seen that increase in current can be prevented by lowering the motor applied voltage.

  This detects the current flowing through the inverter circuit and estimates the phase, detects the current value at a predetermined timing, and controls the voltage applied to the motor so that the current value does not exceed the current threshold value. This makes it possible to achieve both reliable phase estimation and current limit, detect the current value flowing through the inverter circuit directly from the current detection resistor as the current value, estimate the phase, and set a predetermined current threshold. The voltage applied to the motor can be controlled so that the current does not exceed the value, and a comparator circuit is not required, and a control device for a brushless DC motor that can be reduced in size, cost, and noise can be obtained. .

  In the embodiment of the present invention, the phase stored in advance is in the range of -30 degrees to 20 degrees, but it may be set in accordance with the motor, and there is no difference in the operation effect.

  Further, although the current is detected at an arbitrary timing other than detecting the phase, the current value for detecting the phase may be compared with the current threshold value Ia, and there is no difference in the operation effect.

  Further, only one point at an arbitrary timing is compared with the current threshold value Ia, but it is also possible to compare at a plurality of timings, and this value may be determined according to the characteristics of the motor. There is no difference.

  Also, by making both phase estimation and current limit compatible, it is possible to prevent the switching element from being damaged and the magnet of the rotor from being demagnetized to reduce the efficiency of the brushless DC motor. A highly reliable wide-angle energization sensorless drive controller and ventilation fan, which eliminates the need for a comparator circuit, can be reduced in size, cost, and noise. An exchangeable chiller can be provided.

(Embodiment 2)
FIG. 6 shows a current waveform detected by a current detection resistor in 150-degree wide-angle energization. In the figure, it can be confirmed that there is an energization overlap period and a period in which energization does not overlap in one period of 60 electrical angles, and the shape of the current waveform is different. The energization overlap period, the period in which energization does not overlap, and the current waveform are specifically shown in FIGS. 19 (a) and 19 (b).

  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, a highly reliable brushless DC motor capable of accurately detecting the phase in the wide-angle energization and controlling the voltage applied to the motor so that the current does not exceed a predetermined current threshold. Can be obtained.

(Embodiment 3)
FIG. 8 shows a current waveform detected by the current detection resistor at 150 degrees energization. The current value at any one point in the period of one cycle of 60 electrical angles, that is, I3, is A / D converted, and compared with the current threshold value Ia, and the current difference Id can be obtained from Equation 2.

Id = current value of I3−current threshold value of Ia (Expression 2)
At this time, the correction voltage Vd that lowers the voltage applied to the motor so as not to exceed the current threshold value is obtained by Equation 3, where the gain is α.

Vd = Id × α (Formula 3)
Therefore, the voltage to be applied to the motor so as not to exceed the current threshold value may be a voltage obtained by reducing the correction voltage Vd from the voltage Vm applied to the motor.

  For example, when the current threshold value is 2A, the motor applied voltage Vm is 24V, and α is 0.2, assuming that the A / D converted current value I3 = 2.5A, Vd3 = 0.5V. In order to prevent the current from exceeding the current threshold at the position of I3, after the commutation timing, the energization switching is performed and at the same time the voltage applied to the motor is lowered from 24V to 23.5V. Similarly, the current threshold value can be prevented from exceeding by controlling the voltage applied for each period.

  As a result, the voltage value for lowering the voltage applied to the motor can be changed according to the magnitude of the current exceeding the current threshold, and excessive current continuously flows to the motor due to a sudden load fluctuation or the like. A highly reliable brushless DC motor control device that can shorten the period and makes it difficult to damage the switching element or demagnetize the rotor magnet is obtained.

  In the present embodiment, the gain α is 0.2, but this value may be determined in accordance with the characteristics of the motor, and there is no difference in the operational effect.

(Embodiment 4)
FIG. 9 shows a current waveform detected by the current detection resistor at 150 degrees energization. A / D conversion is performed on current values at any four points in one period of electrical angle of 60 degrees, that is, Is1, Is2, Is3, and Is4, the maximum current value is obtained, and compared with the current threshold value Ia. When it is larger than the current threshold value Ia, the current difference Id is obtained from Equation 2, and further, a correction voltage Vd that lowers the voltage applied to the motor is obtained from Equation 3. With this correction voltage, the voltage Vm applied to the motor during the period of one cycle of the next electrical angle of 60 degrees is lowered. Similarly, the current threshold value Ia is not exceeded by controlling the voltage applied to the motor for each period of the next electrical angle of 60 degrees. Therefore, the voltage to be applied to the motor so as not to exceed the current threshold value may be a voltage obtained by reducing the correction voltage Vd from the voltage Vm applied to the motor.

For example, when the current threshold value is Ia = 2.0 A, the motor applied voltage Vm is 24 V, and α is 0.2, the A / D current values are Is1 = 1.7 A and Is2 = 1.7 A, respectively. , Is3 = 2.6A and Is4 = 3.0A, the current value of Is4 is the largest, so Is4 = 3.0
Since A is compared with current threshold value Ia = 2.0A, and Is4 is larger, current difference Id == 1.0A is obtained, and correction voltage Vd = 0.2V is obtained.

  Therefore, the voltage applied to the motor is lowered from 24V to 23.8V in the period of one cycle of the next electrical angle of 60 degrees. Similarly, it is possible to prevent the current threshold from being exceeded by controlling the voltage applied to the motor for each period of 60 electrical angles.

  As a result, control is performed based on the maximum value of the current flowing through the inverter circuit, and the current waveform can be accurately detected without being deformed, so that the magnetic pole position can be accurately estimated and the efficiency of the brushless DC motor is reduced. Thus, a highly reliable brushless DC motor control device can be obtained.

  In this embodiment, the current value is set to any four points in one period of 60 degrees electrical angle. However, the number of samples may be determined according to the characteristics of the motor, and for phase detection. The current value may be sufficient, and there is no difference in the effect.

  Further, although the gain α is set to 0.2, this numerical value may be determined in accordance with the characteristics of the motor, and there is no difference in the operation effect.

(Embodiment 5)
FIG. 10 shows a current waveform detected by the current detection resistor at 150 degrees energization. A / D conversion is performed on current values at any four points in one period of electrical angle 60 degrees, that is, Is1, Is2, Is3, and Is4, and an average current value Isavg is obtained from Equation 4.

Isavg = (Is1 + Is2 + Is3 + Is4) / 4 (Formula 4)
The average current value Isavg and the current threshold value Ia are compared, and when the average current value Isavg is larger, the current difference Id is obtained by Equation 5.

Id = current value of Isag−current threshold value of Ia (Expression 5)
Therefore, a correction voltage Vd for reducing the voltage Vm applied to the motor so as not to exceed the current threshold value Ia is obtained by Equation 3. With this correction voltage Vd, the voltage Vm applied to the motor is lowered in the period of one cycle of the next electrical angle of 60 degrees. Similarly, the current threshold Ia is not exceeded by controlling the voltage Vm applied to the motor for each period of 60 electrical angles. Therefore, the voltage Vm to be applied to the motor so as not to exceed the current threshold value Ia may be a voltage obtained by subtracting the correction voltage Vd from the voltage Vm applied to the motor.

For example, when the current threshold value Ia is 2.0 A, the motor applied voltage Vm is 24 V, and α is 0.2, the current values obtained by A / D conversion are Is1 = 1.7 A, Is2 = 1.7 A, When Is3 = 2.6A and Is4 = 3.0A, the average current Isavg is 2.25A, the current difference Id is 0.25A, and the correction voltage Vd is 0.5V.

  Therefore, the voltage applied to the motor is lowered from 24V to 23.5V in the period of one cycle of the next electrical angle of 60 degrees. Similarly, the current threshold value can be prevented from exceeding by controlling the voltage applied to the motor every period of the next electrical angle of 60 degrees.

  As a result, the control is performed based on the average value of the current flowing through the inverter circuit, and the current can be suppressed without changing the energization phase, and a highly reliable brushless DC motor that can prevent the motor efficiency from being lowered. A control device is obtained.

In this embodiment, the current value is set to any four points in one period of 60 degrees electrical angle. However, the number of samples may be determined according to the characteristics of the motor, and for phase detection. The current value may be sufficient, and there is no difference in the effect.

  Further, although the gain α is set to 0.2, this numerical value may be determined in accordance with the characteristics of the motor, and there is no difference in the operation effect.

(Embodiment 6)
At startup, control is performed based on the maximum value of the current flowing through the inverter circuit, and during operation, control is performed based on the average value of the current, and control is changed between startup and operation.

  In the above configuration, A / D conversion is performed on the current values at any four points in one period of electrical angle 60 degrees, that is, Is1, Is2, Is3, and Is4. Comparison is made with the threshold value Ia, and when it is larger than the current threshold value Ia, the current difference Id is obtained from Equation 2, and further, the correction voltage Vd for lowering the voltage applied to the motor is obtained from Equation 3. On the other hand, during operation, the average current value Isavg is similarly obtained from the equation 4, the average current value Isavg is compared with the current threshold value Ia, and when the average current value Isavg is larger, the current difference Id is expressed by the equation 5 And a correction voltage Vd for reducing the voltage applied to the motor so as not to exceed the current threshold value Ia is obtained by Equation 3.

  There is a difference between the correction voltage Vd during start-up and during operation, and the voltage Vm applied to the motor is lowered with this correction voltage after one period of the next electrical angle of 60 degrees. Similarly, the current threshold value is not exceeded by controlling the voltage applied to the motor for each period of the next electrical angle of 60 degrees. Therefore, it is possible to change the control method of overcurrent protection between startup and operation.

  This suppresses the current at the maximum current value at startup when there is a high risk of damage to the switching element or the magnet of the rotor, and suppresses the motor current more stably during operation. Thus, an excessive current can be prevented from being continuously generated at the time of starting, and a sufficient starting torque can be obtained, so that a highly reliable brushless DC motor control device can be obtained.

(Embodiment 7)
During operation, control is performed based on the average value of the current flowing through the inverter circuit. When a predetermined current threshold value is exceeded, control is performed based on the maximum value of the current value, and the control is changed according to changes in the motor load. It is what I did.

  In the above configuration, A / D conversion is performed on current values at any four points in one period of an electrical angle of 60 degrees, that is, Is1, Is2, Is3, and Is4. Similarly, the average current value Isavg is expressed by Equation 4, Current difference Id is obtained from Equation 5, and a correction voltage Vd that lowers the voltage Vm applied to the motor so as not to exceed the current threshold value Ia is obtained from Equation 3. With this correction voltage Vd, the voltage Vm applied to the motor is lowered after a period of the next electrical angle of 60 degrees. In the same manner, the current threshold Ia is not exceeded by controlling the voltage Vm applied to the motor for each period of the next electrical angle of 60 degrees.

At this time, if the motor load fluctuates, the load becomes heavier and the motor current increases and the current difference Id exceeds a predetermined threshold value Idmax, currents Is1, Is2, Is3, and Is4 are respectively supplied. Compared with the threshold value Ia, the current difference Id is similarly obtained from Equation 2, and the correction voltage Vd for decreasing the voltage applied to the motor from the largest current difference Id so as not to exceed the current threshold value is obtained. The voltage Vm applied to the motor is lowered after a period of one cycle with an electrical angle of 60 degrees using this correction voltage. Similarly, the current threshold value can be prevented from exceeding by controlling the voltage Vm applied to the motor for each period of 60 electrical angles.

  As a result, when the current increases and exceeds the current threshold due to sudden load fluctuations, etc., the current can be suppressed at the maximum value of the current, and the period during which excessive current continues to flow through the motor is shortened. Therefore, a highly reliable brushless DC motor control device can be obtained.

(Embodiment 8)
FIG. 11 shows a current waveform detected by the current detection resistor at 150 degrees energization. In the figure, a second current threshold value Ib larger than the first current threshold value Ia is provided.

  As shown by the dotted line, the description will be given in a state where the current flows beyond the current threshold value Ib after Is3.

  A / D conversion is performed on current values at four points in one period of an electrical angle of 60 degrees, that is, Is1, Is2, Is3, and Is4. When it is determined that the current value exceeds the current threshold value Ib at Is3, the control is performed so as to reduce the voltage applied to the motor by performing A / D conversion by increasing the current value detection cycle. Work. Specifically, when the current value of Is3 is A / D converted, if the current threshold value Ib is exceeded, the current difference Idb with respect to the current threshold value Ib is obtained by Equation 6.

Idb = A / D converted current value−Ib current threshold value (Expression 6)
At this time, the correction voltage Vdb that lowers the voltage applied to the motor so as not to exceed the current threshold value is obtained by Equation 7, where the gain is β.

Vdb = Idb × β (Expression 7)
Therefore, the voltage to be applied to the motor so as not to exceed the current threshold value Ib may be a voltage obtained by subtracting the correction voltage Vdb from the voltage Vm applied to the motor. The correction voltage Vbd is lowered to the voltage Vm applied to the motor at every next detection cycle.

  At the commutation timing for switching energization in the period of one cycle of the next electrical angle of 60 degrees, the current difference Id is obtained from the equations 4 and 5, and the correction voltage Vd for lowering the voltage applied to the motor is obtained by the equation 3. Then, control is performed so that the applied voltage Vm of the motor is lowered by the correction voltage Vd.

  For example, when the current threshold value Ib is 3 A, the gain β is 2, and Is4 is 3.8 A, the current difference Idb from the current threshold value Ib is 0.8 A, and the correction voltage is 1.6 V. If the voltage applied to the motor when the current value of Is4 is A / D converted is 22V, a voltage of 20.4V may be applied so as not to exceed the current limit Ib.

  Similarly, the current threshold value Ib can be prevented from exceeding by controlling the voltage applied to the motor by increasing the detection cycle.

  As a result, when the current greatly increases due to load fluctuation or the like and exceeds the second current threshold, the switching element is turned off to shut down the current. Can be prevented from flowing, an excessive current can be reliably prevented from flowing through the motor, and a highly reliable brushless DC motor control device can be obtained.

  In the present embodiment, the gain β is set to 2, but this numerical value may be determined in accordance with the characteristics of the motor, and there is no difference in the operation effect.

  If the voltage is changed by PWM when the detection cycle is accelerated, the PWM carrier cycle may be determined according to the characteristics of the motor, and there will be a difference in the function and effect. Absent.

(Embodiment 9)
When the detected current value becomes larger than the second current threshold value Ib, the current value detection cycle is advanced and the voltage applied to the motor is controlled based on the correction voltage Vdb at that time. The correction value Vd of the motor voltage Vm at the commutation timing of the energization switching in the period of one cycle of 60 degrees is designed to lower the voltage more than the value obtained from Equation 3.

  In the above configuration, the correction value Vdc of the motor voltage at the time of energization switching in the period of the next electrical angle of 60 degrees is set to γ, γ is larger than α, and is obtained from Equation 8.

Vdc = Id × γ (Expression 8)
Therefore, when the detected current value becomes larger than the second current threshold value Ib, the motor voltage at the commutation timing of the energization switching in the period of the next electrical angle of 60 degrees should be applied to the motor. The voltage may be a voltage obtained by subtracting the correction voltage Vdc from the voltage Vm applied to the motor.

  As a result, when the current greatly increases due to load fluctuation or the like and exceeds the second current threshold value, the current at the commutation timing of the energization switching in the period of one cycle of the next electrical angle of 60 degrees. The voltage to be applied to the motor can be changed to a greater value than usual, so that an excessive current can be reliably prevented from flowing through the motor, and a highly reliable brushless DC motor control device can be obtained.

(Embodiment 10)
FIG. 12 shows a current waveform detected by the current detection resistor at 150 degrees energization.

In the figure, any four points period of one cycle of the electrical angle of 60 degrees, i.e. Is1, Is2, Is3, the current A / D you conversion in Is4. At this time, the current threshold Ib that does not exceed the predetermined current threshold Ib at the time Is3 and the current flows at the time Is4 exceeds the current threshold Ib that is predetermined at the Is3 time. An explanation will be given in a state where the

  As shown in FIG. 12A, when current threshold Ib is not exceeded at Is3 time and current is exceeded at Is4 time, Idb and Vdb are expressed by Equations 6 and 7. The voltage to be applied to the motor to the motor voltage at the time of commutation timing of the energization switching in the period of one cycle of the next electrical angle of 60 degrees calculated is obtained by reducing the correction voltage Vdb from the voltage Vm applied to the motor. What is necessary is just a voltage.

  As shown in FIG. 12B, it can be confirmed that the current value Ib is already larger than the predetermined current value Ib at the time of Is3, and has become larger before this measurement timing. In this case, the motor voltage Vm is set to 0 V and the motor is stopped.

  Thus, when the current value is earlier than a predetermined timing, the motor can be stopped, and a highly reliable brushless DC motor control device can be obtained.

(Embodiment 11)
FIG. 13 shows a current waveform detected by the current detection resistor at 150 degrees energization.

  In the figure, the description will be made in a state where the current value Ib exceeds a predetermined value at the timing of detecting Is1 as indicated by a dotted line.

  The current values of Is1 and Is2 are detected for phase estimation. However, when the current value is larger than a predetermined value, the motor can be stopped.

  As a result, the motor can be stopped when the current value measurement timing of the phase detection exceeds a predetermined current value. As a result, damage to the switching element and demagnetization of the rotor magnet can be prevented in advance, and a highly reliable brushless DC motor control device can be obtained.

(Embodiment 12)
As shown in FIG. 14, a brushless DC motor control device is mounted on a heat exchange type cooler.

  In the figure, the outdoor brushless DC motor 2a is used to rotate the outdoor blower 14 so that the ambient air around which the heating element storage box 15 such as a mobile phone exchange base station is installed After sucking in from the lower outside air inlet 17 and passing through the heat exchange element 18, the air is discharged from the upper air outlet 19 in the upper part of the heat exchange type cooler 16. By rotating the indoor air blower 21 with the indoor brushless DC motor 20, the heated inside air inside the heating element storage box is sucked from the inside air inlet 22 at the top of the heat exchange type cooler 16, and the heat exchange element 18. Then, the air is discharged from the inside air discharge port 23 below the heat exchange type cooler 16. The movement of the outside air due to the rotation of the outdoor blower 14 is indicated by a black arrow, and the movement of the indoor air due to the rotation of the indoor blower 21 is indicated by a white arrow. Heat is exchanged when the outside air cooled and the heated indoor air pass through the heat exchange element 18, the outside air is heated and discharged into the atmosphere, and the indoor air is cooled and returned to the indoor side, so that heat is generated. The inside of the body storage box 15 can be cooled. In the heat exchange element 18, 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 16. The control box 24 installed in the internal air passage of the heat exchange type cooler 16 is provided with a control device 13 for driving the outdoor brushless DC motor 2a. The control device 13 is supplied with low-voltage DC power from a low-voltage DC power source 5 installed in the heating element storage box 15, and drives the brushless DC motor 2 on the outdoor side through the drive lead wire 25 from the control device 13. is doing. The control box 24 also includes a room-side inverter circuit (not shown) that drives the room-side brushless DC motor 20 and operates the room-side fan 21.

  This eliminates the need for a relay lead wire for the sensor signal used for connection to the control device installed on the side of the inside air flow 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, a lead wire is unnecessary and the work of connecting a relay line is eliminated, so that a low-cost heat exchange type cooler can be obtained.

  The present invention can also be applied to a brushless DC motor control device that is generally used and a brushless DC motor control device that is mounted on a ventilation fan.

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 Current limiting means 12 Drive circuit 13 Controller

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 the current detection resistor output In the current waveform obtained by the current value, the current change rate which is the ratio of the current value at the first and second timings determined in advance during the non-overlapping period that is not the energization overlapping period is induced in the stator winding. The phase relationship between the induced voltage and the voltage applied to the stator winding is memorized in advance. A phase estimating means for estimating the phase of the voltage applied to the stator winding with respect to the induced voltage induced in the stator winding, and the phase estimated by the phase estimating means follows a predetermined target phase. A commutation timing determining means for determining the commutation timing so that the current value output from the current detection resistor does not exceed a predetermined current limit value, and a current limit for controlling a voltage applied to the motor Means for Controlling Brushless DC Motor In the current waveform obtained from the current value output from the current detection resistor, the phase estimation means is a ratio of the current values at the first and second timings determined in advance in the non-overlapping periods other than the energization overlapping period. The brushless DC motor control device according to claim 1, wherein a correlation curve of a phase between the current change rate and a voltage applied to the stator winding is stored in advance. The current limiting means changes the amount of change for decreasing the voltage applied to the motor according to the difference when the current flowing through the inverter circuit is large with respect to a predetermined threshold value. Item 3. A control device for a brushless DC motor according to any one of Items 1 to 2. Current limiting means, to the first predetermined threshold, a brushless DC according to any one of claims 1 乃 optimum 3, characterized in that for controlling the maximum value of the current flowing in the inverter circuit Motor control device.
Current limiting means, to the first predetermined threshold, a brushless DC according to any one of claims 1 乃 optimum 4, characterized in that for controlling the average value of the current flowing in the inverter circuit Motor control device. The current limiting means controls the first threshold value determined in advance by the maximum value of the current flowing through the inverter circuit at the start-up and by the average value of the current during operation. brushless DC motor control device according to any one of claims 1 乃 optimum 5, characterized. The current limiting means controls the first threshold value determined in advance by the average value of the current flowing through the inverter circuit during operation, and when the predetermined first threshold value is exceeded, , brushless DC motor control device according to any one of claims 1 乃 optimum 6, characterized in that for controlling the maximum value of the current. The current limiting means provides a second threshold value larger than a predetermined first threshold value, and shuts down the current when the current flowing through the inverter circuit exceeds the second threshold value. brushless DC motor control apparatus according to any one of claims 4 乃 optimum 7, wherein the controller controls such that the second threshold or more current is not increased. The current limiting means provides a second threshold value larger than a predetermined first threshold value, and shuts down the current when the current flowing through the inverter circuit exceeds the second threshold value. Control is performed so that the current does not become larger than the second threshold value, and the amount of change that lowers the voltage applied to the motor is changed to be larger than the value that is changed by a predetermined first threshold value. brushless DC motor control apparatus according to any one of claims 4 乃 optimum 8. The current limiting means provides a second threshold value larger than a predetermined first threshold value, and when the current flowing through the inverter circuit exceeds the second threshold value, the timing is predetermined. 10. The brushless DC motor control device according to claim 4, wherein the motor is stopped when the timing is earlier than the predetermined timing. The current limiting means provides a second threshold value that is greater than a predetermined first threshold value, and the current flowing through the inverter circuit exceeds the second threshold value during the phase estimation period. The control device for a brushless DC motor according to any one of claims 4 to 10, wherein the motor is stopped. Ventilation blower equipped with a control device for a brushless DC motor according to any one of claims 1 乃 optimum 11.

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