JP2021153353A - Motor drive controller and blower - Google Patents

Abstract

To provide a motor drive controller capable of enlarging an operation range of a motor, which can be controlled by the same current detection circuit.SOLUTION: A motor drive controller for driving a motor by a position sensorless control system includes a current detection circuit 12 which detects motor current flowing in respective phases of the motor. The current detection circuit 12 includes an amplifier 20 for amplifying a detection value of the motor current; and an analog switch 23 for switching resistance values of resistors 21 and 22 which determine an amplification gain of the amplifier 20.SELECTED DRAWING: Figure 3

Description

The present disclosure relates to a motor drive control device including a current detection circuit, and a blower device including a motor drive control device.

In recent years, in blower equipment such as ventilation fans and blowers, equipment using a permanent magnet type synchronous motor having a permanent magnet in the rotor has increased in order to control a wide range of variable speeds, save power consumption, or drive with low noise. There is. The permanent magnet type synchronous motor is driven by a motor drive circuit including an inverter circuit. Specifically, the motor drive circuit drives the permanent magnet type synchronous motor by controlling the inverter circuit by pulse width modulation (PWM) and applying the voltage obtained by the PWM control to the permanent magnet type synchronous motor. do.

When driving a permanent magnet type synchronous motor, it is necessary to detect the position of the magnetic pole of the permanent magnet, which is a rotor. On the other hand, recently, a position sensorless control method in which the magnetic pole position of a permanent magnet is estimated and controlled from information such as a motor current without directly detecting the magnetic pole position of the permanent magnet has become mainstream.

Patent Document 1 below discloses a motor drive control device that drives a permanent magnet type synchronous motor by a position sensorless control method.

Japanese Patent No. 4744505

In the position sensorless control system, in order to accurately and finely control the operation of the motor, it is necessary to increase the resolution at the time of detecting the motor current as much as possible. While the motor current is an analog amount, a microcomputer (hereinafter abbreviated as "microcomputer"), which is a processor mounted on a motor drive control device, performs various processes with digital values. Therefore, when the motor current is detected and incorporated into the microcomputer, the analog amount is converted into a digital value. In order to convert an analog amount into a digital value, an analog-to-digital (AD) conversion function provided in the microcomputer is used.

The resolution of quantization when converting an analog quantity into a digital value is determined by the microcomputer, and the current value per digit is determined by the resolution of the microcomputer. Therefore, in order to improve the control accuracy in the operating range of the motor, it is necessary to set the detection range of the motor current according to the operating range of the motor. That is, even with the hardware of the same motor drive control device, there arises a problem that fine operation control cannot be performed unless the detection range of the motor current is set according to the motor drive control device. On the contrary, if the motor current detection range cannot be set according to the motor drive control device, it becomes necessary to prepare a current detection circuit having different specifications for each current detection range, which causes a problem of impairing productivity. It will be. Therefore, it is desired to expand the operating range of the motor that can be controlled by the same current detection circuit.

The present disclosure has been made in view of the above, and an object of the present invention is to obtain a motor drive control device capable of expanding the operating range of a motor that can be controlled by the same current detection circuit.

In order to solve the above-mentioned problems and achieve the object, the present disclosure is a motor drive control device for driving a motor by a position sensorless control method. The motor drive control device includes a current detection circuit that detects the motor current flowing in each phase of the motor, and a control unit that controls to change the circuit configuration of the current detection circuit. The current detection circuit includes an amplifier that amplifies the detected value of the motor current and an analog switch that switches the resistance value of the resistor that determines the amplification gain of the amplifier.

According to the motor drive control device according to the present disclosure, there is an effect that the operating range of the motor that can be controlled by the same current detection circuit can be expanded.

The figure which shows the structure of the motor drive control device which concerns on Embodiment 1. A block diagram showing an example of a hardware configuration that realizes the functions of the control unit shown in FIG. The figure which shows the structural example of the current detection circuit in Embodiment 1. The figure which shows how the current detection range is expanded by the current detection circuit in Embodiment 1. The figure which shows the structural example of the current detection circuit in Embodiment 2. Flow chart showing the operation flow in the third embodiment Perspective view provided for explanation of a ventilation fan which is an example of a blower device according to a fourth embodiment.

The motor drive control device and the blower device according to the embodiment of the present disclosure will be described in detail with reference to the accompanying drawings. In the following, the electrical connection and the physical connection will be simply referred to as "connection" without any distinction.

Embodiment 1.
FIG. 1 is a diagram showing a configuration of a motor drive control device 100 according to the first embodiment. As shown in FIG. 1, the motor drive control device 100 according to the first embodiment includes a rectifier circuit 2, a smoothing capacitor 4, an inverter circuit 5, a control unit 9, and a current detection circuit 12. The control unit 9 includes a sensorless motor control unit 10 and a current calculation unit 11. Although the details will be described later, the control unit 9 controls to change the circuit configuration of the current detection circuit 12. The current detection circuit 12 is a circuit that detects the motor current.

An AC power supply 1 is connected to the input end of the motor drive control device 100, and a motor 7 is connected to the output end. The motor drive control device 100 is a device that drives the motor 7 in a position sensorless control system by the electric power supplied from the AC power supply 1. An example of the motor 7 is a permanent magnet type synchronous motor, but the present invention is not limited to this. Any motor may be used as long as it can be driven by the position sensorless control method.

An example of the AC power supply 1 is a commercial power supply. In ordinary Japanese households, single-phase alternating current with a frequency of 50 Hz or 60 Hz and a voltage of 100 V is used. On the other hand, in the case of overseas or when the motor drive control device 100 is for business use, single-phase alternating current having a voltage of 200 V or more may be used.

An example of the rectifier circuit 2 is the illustrated full-wave rectifier circuit. The rectifier circuit 2 includes four diodes 3a, 3b, 3c, and 3d (hereinafter, appropriately referred to as “3a to 3d”) to be bridge-connected. The rectifier circuit 2 converts the AC voltage output from the AC power supply 1 into a DC voltage. The rectifier circuit 2 and the inverter circuit 5 are connected by a DC bus 15 on the high potential side and a DC bus 16 on the low potential side. The smoothing capacitor 4 is connected between the DC bus 15 and the DC bus 16 to smooth the DC voltage output by the rectifier circuit 2.

A DC voltage rectified by the rectifier circuit 2 and smoothed by the smoothing capacitor 4 is applied to the inverter circuit 5. The inverter circuit 5 performs a PWM operation under the control of the control unit 9, and converts the applied DC voltage into a three-phase AC voltage of an arbitrary voltage and an arbitrary frequency.

The inverter circuit 5 includes six switching elements 6a, 6b, 6c, 6d, 6e, 6f (hereinafter, appropriately referred to as “6a to 6f”) to be bridge-connected. An example of the switching elements 6a to 6f is an insulated gate bipolar transistor (IGBT), and another example of the switching elements 6a to 6f is a metal oxide semiconductor field effect transistor (Metal-Oxide-Semiconductor Field-). Effect Transistor: MOSFET).

Each of the switching elements 6a to 6f includes a diode connected in antiparallel. The antiparallel means that the direction of the current flowing through the diode is connected so as to be opposite to the direction of the current flowing when the switching element is conducting. The current flowing through the diode is sometimes referred to as the reflux current. In the case of MOSFET, a parasitic diode exists inside the element. Therefore, when MOSFETs are used, it is possible to omit diodes connected in antiparallel by using parasitic diodes.

The switching elements 6a and 6b are connected in series to form a U-phase leg. Similarly, the switching elements 6c and 6d are connected in series to form a V-phase leg, and the switching elements 6e and 6f are connected in series to form a W-phase leg. The U-phase leg, V-phase leg and W-phase leg are connected in parallel with each other. In each phase leg, the switching elements 6a, 6c, 6e located on the high potential side may be referred to as "upper arm switching element" or simply "upper arm". Further, the switching elements 6b, 6d, 6f located on the low potential side may be referred to as a "lower arm switching element" or simply a "lower arm".

A shunt resistor 8a is connected between the emitter of the switching element 6b and the terminal to which the low potential side of each phase leg is commonly connected, and between the switching element 6d and the terminal on the low potential side. , The shunt resistor 8b is connected. In the example of FIG. 1, a shunt resistor is not connected to the W-phase leg, but a shunt resistor may be connected to the W-phase leg as well. The method in which the shunt resistors are provided on the three three-phase legs is sometimes called the "three shunt method", and the method in which the shunt resistors are provided on the two legs is sometimes called the "two shunt method". In the case of the two-shunt system, the current of the phase without the shunt resistor can be obtained by calculation from the two currents of the phase with the shunt resistor.

The motor 7 includes a rotor 7a, a U-phase winding 7U, a V-phase winding 7V, and a W-phase winding 7W. One end of each phase winding is connected to each other, and the other end of each phase winding is connected to the connection point between the switching elements of the upper and lower arms in the leg of the corresponding phase.

The motor current flowing through the switching element 6b flows through the shunt resistor 8a and is converted into a voltage by the shunt resistor 8a. Further, the motor current flowing through the switching element 6d flows through the shunt resistor 8b and is converted into a voltage by the shunt resistor 8b. Each voltage generated in the shunt resistors 8a and 8b is input to the current detection circuit 12. The current detection circuit 12 amplifies the input voltage. Further, the current detection circuit 12 performs a level shift process so that the amplified voltage becomes a voltage value suitable for the input range of the control unit 9.

The current calculation unit 11 calculates the currents Id and Iq based on the information of the motor current output from the current detection circuit 12. The current Id is the d-axis current value in the dq coordinate system, and the current Iq is the q-axis current value in the dq coordinate system. The dq coordinate system is a coordinate system used in the internal processing of the control unit 9.

The sensorless motor control unit 10 PWM-controls the inverter circuit 5 by determining the switching time of the switching elements 6a to 6f based on the currents Id and Iq calculated by the current calculation unit 11. As a result, the current flowing through each phase winding of the motor 7 is controlled, and the motor 7 is PWM-driven.

FIG. 2 is a block diagram showing an example of a hardware configuration that realizes the function of the control unit 9 shown in FIG. When the function of the control unit 9 described above and the function of the control unit 9 described below are realized, as shown in FIG. 2, the processor 300 that performs the calculation and the memory 302 in which the program read by the processor 300 is stored are stored. , And an interface 304 for inputting / outputting signals.

The processor 300 is an example of a calculation means. The processor 300 may be referred to as an arithmetic unit, a microprocessor, a microcomputer, a CPU (Central Processing Unit), a DSP (Digital Signal Processor), or the like. Examples of the memory 302 include non-volatile or volatile semiconductor memories such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Project ROM), and EEPROM (registered trademark) (Electrically EPROM). be able to.

Specifically, the memory 302 stores a program that executes the motor control function of the control unit 9. The processor 300 sends and receives necessary information via the interface 304, the processor 300 executes a program stored in the memory 302, and the processor 300 refers to a table stored in the memory 302. Control can be performed. The calculation result by the processor 300 can be stored in the memory 302.

Next, the configuration and operation of the main part in the first embodiment will be described. FIG. 3 is a diagram showing a configuration example of the current detection circuit 12 according to the first embodiment. FIG. 3 shows an example of a circuit configuration for detecting the motor current Im flowing through the shunt resistor 8a via the switching element 6b of the lower arm of the U phase.

The current detection circuit 12 includes an amplifier 20, an analog switch 23, and resistors 21, 22, 24, 25, 26, 27. For each resistor, the alphanumeric characters in parentheses shown with the code represent the resistance value of each resistor. The output of the current detection circuit 12 is input to the microcomputer 14 provided in the control unit 9. The microcomputer 14 includes an input port 14a as an input terminal and an output port 14b as an output terminal.

In FIG. 3, the motor current Im is detected using the shunt resistor 8a. Here, if the resistance value Rs of the shunt resistor 8a is increased, the loss due to heat generation of the shunt resistor 8a becomes large. Therefore, as the resistance value Rs of the shunt resistor 8a, a small resistance value of 1Ω or less is used. On the other hand, when the resistance value is small, the voltage of the shunt resistor 8a is also small. Therefore, as shown in FIG. 3, a configuration is adopted in which the voltage amplified by the amplifier 20 is input to the microcomputer 14. A power supply voltage VCS is applied to the microcomputer 14 and the amplifier 20.

The amplifier 20 includes a positive input terminal 20a which is a non-inverting terminal, a negative input terminal 20b which is an inverting terminal, and an output terminal 20c. The analog switch 23 is a double-throw type switch, and includes a common terminal 23a, a first contact 23b, and a second contact 23c. The analog switch 23 switches contacts based on the input switch control signal.

One end of the resistor 24 is connected to the power supply voltage VCS. The other end of the resistor 24 is connected to one end of the resistor 25, the negative input terminal 20b of the amplifier 20, and the common terminal 23a of the analog switch 23. The other end of the resistor 25 is connected to the ground (GND).

One end of the resistor 26 is connected to the power supply voltage VCS. The other end of the resistor 26 is connected to one end of the resistor 27 and the positive input terminal 20a of the amplifier 20. The other end of the resistor 27 is connected to the connection point between the switching element 6b and the shunt resistor 8a.

One end of the resistor 21 is connected to the output terminal 20c of the amplifier 20 and one end of the resistor 22. The other end of the resistor 21 is connected to the first contact 23b of the analog switch 23. The other end of the resistor 22 is connected to the second contact 23c of the analog switch 23. The output terminal 20c of the amplifier 20 is connected to the input port 14a of the microcomputer 14.

Next, the operation of the current detection circuit 12 will be described. A voltage dividing voltage of the power supply voltage VCS divided by the resistor 24 and the resistor 25 is applied to the negative input terminal 20b of the amplifier 20. Further, when the motor current Im does not flow, the resistance value of the shunt resistor 8a is small, so that the voltage dividing voltage of the power supply voltage VCS divided by the resistor 26 and the resistor 27 is applied to the positive input terminal 20a of the amplifier 20. NS. On the other hand, when the motor current Im flows, a voltage obtained by superimposing the voltage of the shunt resistor 8a on the voltage dividing voltage when the motor current Im does not flow is applied to the positive input terminal 20a of the amplifier 20. This voltage is amplified by the amplifier 20. When the output voltage of the amplifier 20 is expressed by Vo, it is expressed by the following equation.

Vo = [(Rf1 / R0) + (1/2)] x Rs x Im + (1/2) x VCS ... (1)

In the above equation (1), R0 is the resistance value of the resistors 24 and 25. Further, the above equation (1) represents an output voltage when the analog switch 23 is connected to the first contact 23b. When the analog switch 23 is connected to the second contact 23c, Rf1 is replaced with Rf2. There is a relationship of Rf1> Rf2 between Rf1 and Rf2. The contact switching in the analog switch 23 is performed by the switch control signal output from the output port 14b of the microcomputer 14.

As described above, the output voltage Vo is input to the input port 14a of the microcomputer 14. Inside the microcomputer 14, an AD conversion process for converting an analog amount into a digital value is performed. Therefore, in the current detection circuit 12, the output voltage Vo of the amplifier 20 needs to be suppressed so as to be within the range of 0 to VCS [V] where AD conversion is possible. Therefore, in the first embodiment, the amplification gain of the amplifier 20 is adjusted. Specifically, in FIG. 3, the resistor that determines the amplification gain of the amplifier 20 is switched from the resistor 21 to the resistor 22. This switching can be realized by switching the contact of the analog switch 23 from the first contact 23b to the second contact 23c.

FIG. 4 is a diagram showing a state in which the current detection range is expanded by the current detection circuit 12 in the first embodiment. The horizontal axis of FIG. 4 represents the motor current Im, and the vertical axis represents the output voltage Vo of the amplifier 20. FIG. 4 shows that when the resistance value is Rf1, the motor current value when the output voltage Vo becomes the maximum value of the input range, VCS, is Im1. Further, when the resistance value is Rf2, it is shown that the motor current value when the output voltage Vo becomes the maximum value of the input range, VCS, is Im2 (> Im1).

When the same current detection circuit supports from a small-capacity motor with a small maximum motor current Im to a large-capacity motor with a large maximum motor current Im, the current detection range is expanded according to the large-capacity motor. It is necessary to keep it. In this case, the resolution of the data in the small current range of the small-capacity motor is insufficient, and the current value per digit becomes large, which causes a problem that fine operation control cannot be performed. For this reason, conventionally, measures have been taken to prepare current detection circuits having different specifications according to the current range used by the motor.

On the other hand, the current detection circuit 12 of the first embodiment has a configuration in which the resistance value that determines the amplification gain of the amplifier 20 is switched by the analog switch 23. Therefore, for example, when controlling a small-capacity motor, the contacts of the analog switch 23 are controlled so that the resistor 21 is connected, and when controlling the large-capacity motor, the resistor 22 is connected. Controls the contacts of the analog switch 23. This makes it possible for the same current detection circuit to handle current detection from small-capacity to large-capacity motors. Further, it is possible to expand the operating range of the motor that can be controlled by the same current detection circuit.

As shown in FIG. 3, the analog switch 23 for switching the resistance value is preferably connected to the negative input terminal 20b side of the amplifier 20. At the negative input terminal 20b of the amplifier 20, a resistor 24 having a resistance value R0 connected to the power supply voltage VCS at one end and a resistor 25 having a resistance value R0 connected to the ground (GND) at the other end are used to connect the power supply voltage VCS. A voltage of (1/2) × VCS obtained by dividing the voltage by 1/2 is applied. This voltage is stable because it does not depend on the motor current Im. Therefore, the voltage applied to the common terminal 23a of the analog switch 23 does not fluctuate significantly. As a result, the current detection circuit 12 shown in FIG. 3 can apply a stable potential to the analog switch 23 even if the resistance value switching control is performed.

The contact switching of the analog switch 23 may be selected depending on the model to be connected. If the storage device that holds the program that operates the microcomputer 14 is a storage device that can write and erase, the output of the signal that controls the switching of the contacts of the analog switch 23 may be described in the program.

As described above, according to the motor drive control device according to the first embodiment, the current detection circuit for detecting the motor current includes an amplifier for amplifying the detected value of the motor current and an analog switch. The control unit controls to switch the resistance value of the resistor that determines the amplification gain of the amplifier by switching the contacts of the analog switch. As a result, current detection from a small-capacity motor to a large-capacity motor can be handled by the same current detection circuit, so that the operating range of the motor that can be controlled by the same current detection circuit can be expanded.

Embodiment 2.
FIG. 5 is a diagram showing a configuration example of the current detection circuit 12A according to the second embodiment. In the current detection circuit 12A, in the configuration of the current detection circuit 12 according to the first embodiment shown in FIG. 3, the analog switch 23 is replaced with the analog switch 23A, and the resistor 22 is replaced with the resistor 22A. The analog switch 23A is a single-throw switch, and includes a common terminal 23Aa and a contact 23Ab. The analog switch 23A switches the circuit on and off based on the input switch control signal.

The common terminal 23Aa of the analog switch 23A is connected to the negative input terminal 20b of the amplifier 20, the other end of the resistor 21, and one end of the resistor 25. One end of the resistor 22A is connected to one end of the resistor 21 and the output terminal 20c of the amplifier 20. The other end of the resistor 22A is connected to the contact 23Ab of the analog switch 23A. Other configurations are the same as or equivalent to the configuration of the current detection circuit 12 shown in FIG. 3, and the same or equivalent components are designated by the same reference numerals. Hereinafter, the description of the duplicated contents will be omitted as appropriate.

Similar to the first embodiment, the current detection circuit 12A in the second embodiment has a mechanism for adjusting the amplification gain of the amplifier 20 according to the capacity of the motor. In the second embodiment, the resistor 21 is left connected, and the analog switch 23A switches whether or not the resistor 22A is connected. When the circuit operation of the second embodiment is the same as that of the first embodiment, the resistance value Rf3 of the resistor 22A may be a value satisfying the following equation.

Rf3 = (Rf1 × Rf2) / (Rf1-Rf2) ... (2)

Since the above equation (2) can be modified as Rf3 = Rf2 / [1- (Rf2 / Rf1)], there is a relationship of Rf3> Rf2 between Rf2 and Rf3.

As the analog switch 23A in the second embodiment, a switch of a simple form having only a short-circuit and an open function can be used instead of an alternative switch. As a result, the unit price of parts can be suppressed as compared with the first embodiment.

As described above, according to the motor drive control device according to the second embodiment, the current detection circuit for detecting the motor current includes an amplifier for amplifying the detected value of the motor current and an analog switch. The control unit controls to switch the resistance value of the resistor that determines the amplification gain of the amplifier by switching the analog switch on and off. As a result, current detection from a small-capacity motor to a large-capacity motor can be handled by the same current detection circuit, so that the operating range of the motor that can be controlled by the same current detection circuit can be expanded.

Embodiment 3.
FIG. 6 is a flowchart showing an operation flow according to the third embodiment. The third embodiment is a mode in which the amplification gain of the amplifier 20 is switched by using the motor current Im. The flowchart shown in FIG. 6 can be implemented by using any of the current detection circuit 12 of the first embodiment shown in FIG. 3 and the current detection circuit 12A of the second embodiment shown in FIG. FIG. 6 illustrates the case where the current detection circuit 12 shown in FIG. 3 is used.

When the motor current Im is smaller than the determination value Im0 (step S101, Yes), the connection of the resistor 21 is selected (step S102). On the other hand, when the motor current Im is equal to or higher than the determination value Im0 (steps S101 and No), the connection of the resistor 22 is selected (step S103). When the processing of steps S102 and S103 is completed, the process returns to step S101, and the processing of FIG. 6 is repeated. As described above, the operation flow of FIG. 6 is always started and executed during the operation of the motor 7.

In step S101 of the operation flow shown in FIG. 6, the case where the motor current Im is equal to the determination value Im0 is determined as "No", but it may be determined as "Yes". That is, the case where the motor current Im is equal to the determination value Im0 may be determined by either "Yes" or "No".

According to the motor drive control device according to the third embodiment, the switching of the resistance value that determines the amplification gain of the amplifier is performed based on the magnitude of the motor current, and the amplification gain of the amplifier is automatically switched according to the magnitude of the motor current. Therefore, it is not necessary to first determine the on or off of the analog switch, and it is not necessary to describe the initial value of the analog switch state in the program. This eliminates the need to select a program according to the model, so that the program can be standardized and standardized.

Embodiment 4.
FIG. 7 is a perspective view for explaining the ventilation fan 150, which is an example of the blower device according to the fourth embodiment. If the motor drive control device according to any one of the first to third embodiments is mounted on the ventilation fan 150, the control circuit for driving the ventilation fan 150 and the control software can be standardized. As a result, the control circuit and control software having the same specifications can be applied to many types of products, so that the cost of the products can be reduced.

The configuration shown in the above embodiments is an example, and can be combined with another known technique, can be combined with each other, and does not deviate from the gist. It is also possible to omit or change a part of the configuration.

1 AC power supply, 2 rectifier circuit, 3a, 3b, 3c, 3d diode, 4 smoothing capacitor, 5 inverter circuit, 6a, 6b, 6c, 6d, 6e, 6f switching element, 7 motor, 7a rotor, 7U U phase winding Wire, 7V V phase winding, 7W W phase winding, 8a, 8b shunt resistance, 9 control unit, 10 sensorless motor control unit, 11 current calculation unit, 12, 12A current detection circuit, 14 microcomputer, 14a input port, 14b Output port, 15,16 DC bus, 20 amplifier, 20a positive input terminal, 20b negative input terminal, 20c output terminal, 21,22,22A, 24,25,26,27 resistance, 23,23A analog switch, 23a, 23Aa Common terminal, 23b 1st contact, 23c 2nd contact, 23Ab contact, 100 motor drive controller, 150 ventilation fan, 300 processor, 302 memory, 304 interface.

Claims (6)

A motor drive control device that drives a motor by a position sensorless control method.
A current detection circuit that detects the motor current flowing in each phase of the motor, and
A control unit that controls to change the circuit configuration of the current detection circuit, and
With
The current detection circuit
An amplifier that amplifies the detected value of the motor current and
An analog switch that switches the resistance value of the resistor that determines the amplification gain of the amplifier,
A motor drive control device characterized by being equipped with. The motor drive control device according to claim 1, wherein the resistance value is switched by switching the contacts of the analog switch. The motor drive control device according to claim 1, wherein the switching of the resistance value is performed by turning the analog switch on and off. The switching of the resistance value is performed based on the magnitude of the motor current.
The motor drive control device according to claim 2 or 3, wherein the amplification gain is automatically switched according to the magnitude of the motor current. The motor drive control device according to any one of claims 1 to 4, wherein the analog switch is connected to a negative input terminal of the amplifier. A blower device including the motor drive control device according to any one of claims 1 to 5.

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