Patent Publication Number: US-2020295632-A1

Title: Identification method for identifying type of brushless dc motor, identification device, and brushless dc motor

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a U.S. national stage of PCT Application No. PCT/JP2018/042167, filed on Nov. 14, 2018, and claiming priority under 35 U.S.C. § 119(a) and 35 U.S.C. § 365(b) from Japanese Application No. 2017-229275, filed Nov. 29, 2017; the entire disclosures of which are hereby incorporated herein by reference. 
    
    
     1. FIELD OF THE INVENTION 
     The present disclosure relates to an identification method for identifying the type of a brushless DC motor, an identification device, and a brushless DC motor. 
     2. BACKGROUND 
     Many electronic devices include, for example, a fan motor as a cooling device for releasing heat generated inside to the outside. In an electronic device, a fan motor is electrically connected to a system controller and operates under the control of the system controller. 
     In a conventional identification method, a fan motor and a system controller communicate with each other to obtain fan identification information. For example, the mode is switched from a normal mode to a command mode, and the fan motor and the system controller transmit and receive commands via a power supply line, a pulse width modulation (PWM) line, and a tachometer (TACH) line. The system controller obtains the fan identification information by handshaking and determines compatibility with the fan motor. In this case, both the system controller and the fan require complicated control software such as switching between the normal mode and the command mode. 
     A conventional motor drive has a regenerative resistor and an operation switch, and has a regenerative power consumption unit connected between DC buses. The operation switch is controlled by comparing the drive voltage and the regenerative voltage. By turning on the operation switch, it is possible to consume the regenerative power from the motor by the regenerative resistor. 
     In the above-described conventional art, a method for more easily identifying information on a brushless DC motor has been desired. 
     SUMMARY 
     An example embodiment of an identification method of the present disclosure is an identification method to identify information on a brushless DC motor output from the brushless DC motor. The identification method is used by an identification device. The brushless DC motor includes at least one resistor connected between a power supply line and a GND line, an inverter that drives a motor, and a switching circuit that switches connection and disconnection between the power supply line and the inverter. The method includes supplying an input voltage from the identification device to the brushless DC motor via the power supply line, disconnecting the inverter from the power supply line via the switching circuit, reading a resistance value of the at least one resistor in a state where driving of the inverter is stopped, and identifying information on the brushless DC motor based on the read resistance value of the at least one resistor. 
     An example embodiment of an identification device of the present disclosure is an identification device to identify information on a brushless DC motor. The brushless DC motor includes at least one resistor connected between a power supply line and a GND line, an inverter that drives a motor, and a switching circuit that switches connection and disconnection between the power supply line and the inverter. The identification device includes a power supply terminal that supplies an input voltage to the brushless DC motor via the power supply line, and a controller to identify information on the brushless DC motor. The controller supplies the input voltage to the brushless DC motor, and in a state where the inverter is disconnected from the power supply line via the switching circuit to stop driving of the inverter, reads the resistance value of the at least one resistor, and identifies the information on the brushless DC motor based on the read resistance value of the at least one resistor. 
     An example embodiment of a brushless DC motor of the present disclosure includes a circuit board, a power supply terminal to supply an input voltage from the outside, the power supply terminal being on the circuit board, an inverter that drives a motor, at least one resistor connected between a power supply line connected to the power supply terminal and a GND line, the at least one resistor having a resistance value larger than a DC resistance of the motor, and a switching circuit to switch connection and disconnection between the power supply line and the inverter, the switching circuit including an under voltage lockout circuit that disconnects the inverter from the power supply line when the level of the input voltage is equal to or lower than a threshold. In a state where the input voltage at the level equal to or lower than the threshold is supplied via the power supply terminal and where the inverter is disconnected from the power supply line by the switching circuit to stop driving of the inverter, a current including information indicating the resistance value of the at least one resistor flows through the power supply terminal. 
     The above and other elements, features, steps, characteristics and advantages of the present disclosure will become more apparent from the following detailed description of the example embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a flowchart of an identification method to identify the type of a brushless DC motor according to an example embodiment of the present disclosure. 
         FIG. 2  is a block diagram schematically showing examples of typical block configurations of a user system  100  and a brushless DC motor  200  according to a first example embodiment of the present disclosure. 
         FIG. 3  is a block diagram schematically showing an example of a block configuration inside the user system  100 . 
         FIG. 4  is a block diagram schematically showing another example of a block configuration of the user system  100  and the brushless DC motor  200  according to the first example embodiment of the present disclosure. 
         FIG. 5  is a flowchart of an identification method of identifying the type of the brushless DC motor  200  according to the first example embodiment of the present disclosure. 
         FIG. 6  is a diagram illustrating a table used to identify the type of the brushless DC motor  200 . 
         FIG. 7  is a flowchart of a further identification method to identify the type of the brushless DC motor  200  according to the first example embodiment of the present disclosure. 
         FIG. 8  is a block diagram schematically showing a variation of a block configuration of the user system  100  and the brushless DC motor  200  according to the first example embodiment of the present disclosure. 
         FIG. 9  is a flowchart showing a specific example of a process of step S 200  for reading an identification resistance value. 
         FIG. 10  is a diagram illustrating a table used to identify the type of a brushless DC motor, using an ASCII code as unique information. 
         FIG. 11A  is a circuit diagram showing a circuit configuration of a variation of identification resistance circuitry  250 . 
         FIG. 11B  is a circuit diagram showing a circuit configuration of a variation of the identification resistance circuitry  250 . 
         FIG. 11C  is a circuit diagram showing a circuit configuration of a variation of the identification resistance circuitry  250 . 
         FIG. 12A  is a flowchart showing another specific example of the process of step S 200  of reading the identification resistance value. 
         FIG. 12B  is a flowchart showing another specific example of the process of step S 200  of reading the identification resistance value. 
         FIG. 13  is a block diagram schematically showing examples of typical block configurations of a user system  100  and a brushless DC motor  200  according to a second example embodiment of the present disclosure. 
         FIG. 14  is a circuit diagram showing an exemplary circuit configuration of an under voltage lockout circuit  272 . 
         FIG. 15  is a flowchart of an identification method for identifying the type of the brushless DC motor  200  according to the second example embodiment of the present disclosure. 
         FIG. 16  is a block diagram schematically showing examples of typical block configurations of a user system  100 , an identification device  100 A, and a brushless DC motor  200  according to a third example embodiment of the present disclosure. 
         FIG. 17  is a block diagram schematically showing another example of a block configuration of the user system  100 , the identification device  100 A, and the brushless DC motor  200  according to the third example embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, example embodiments of identification methods and identification devices to identify the type of a brushless DC motor according to the present disclosure will be described in detail with reference to the accompanying drawings. However, in order to avoid the following description from being unnecessarily redundant and to make it easier for those skilled in the art to understand, a detailed description more than necessary may be omitted. For example, a detailed description of a well-known item or a redundant description of substantially the same configuration may be omitted. In addition, example embodiments of the present disclosure are not limited to the devices or methods illustrated below. For example, one example embodiment can be combined with another example embodiment. 
     Before describing an example embodiment of the present disclosure, overview of an identification method according to the present disclosure will be described with reference to  FIG. 1 .  FIG. 1  shows a flowchart of an identification method for identifying the type of a brushless DC motor according to the present disclosure. 
     The identification method according to the present disclosure is an identification method used for an identification device that identifies information on a brushless DC motor output from the brushless DC motor. The brushless DC motor is typically a two-wire motor having a power supply terminal and a GND terminal, and includes at least one resistor connected between the power line and the GND line. When a power supply voltage is supplied to the brushless DC motor via the power supply terminal, in a state where the inverter is stopped (off), an identification current including identification information indicating a resistance value of at least one resistor flows through the power supply terminal. In this specification, at least one resistor may be referred to as an “identification resistor”, and a resistance value thereof may be referred to as an “identification resistance value”. 
     An identification method according to the present disclosure includes a step of supplying a power supply voltage from an identification device to a brushless DC motor via a power supply line (step S 100 ), a step of reading a resistance value of at least one resistor in a state where the inverter of the brushless DC motor is stopped (step S 200 ), and a step of identifying information on the brushless DC motor based on the read resistance value of at least one resistor (step S 300 ). 
     According to the identification method according to the present disclosure, it is possible to identify various types of information on a brushless DC motor output from the brushless DC motor. Such information includes, for example, brushless DC motor identification information, brushless DC motor serial number, lot number, rated current or rated voltage, and the like. In the present specification, example embodiments for identifying the type of a brushless DC motor, among various types of information related to the brushless DC motor, will be mainly described. 
       FIG. 2  schematically shows examples of typical block configurations of the user system  100  and the brushless DC motor  200  according to the present example embodiment. In this specification, the structure and the operation of the brushless DC motor  200  will be described using a fan motor as an example. The brushless DC motor of the present disclosure includes an inner rotor type or outer rotor type motor. The brushless DC motor  200  is not limited to a fan motor, and is a brushless DC motor used for various applications. The brushless DC motor  200  is, for example, a motor used for home appliances such as an air conditioner or a washing machine, and a vehicle-mounted motor. 
     The user system  100  is electrically connected to the brushless DC motor  200 . The user system  100  can supply power to the brushless DC motor  200 . The user system  100  can be mounted on a brushless DC motor production management system in a factory that produces a wide variety of products. The user system  100  is a system in an electronic device or a vehicle-mounted system on which the brushless DC motor  200  can be mounted. For example, the brushless DC motor  200  is preferably mounted on an electronic device such as a server, a main body of a desktop personal computer, or a game machine. For example, when brushless DC motors  200  with different specifications are produced at the same location, the user system  100  is part of a series of inspection systems. Alternatively, when the brushless DC motor  200  is mounted as a fan motor on the main body of a server or a desktop personal computer, the user system  100  is the entire system or part of the system including various electronic components mounted on a motherboard. 
     The user system  100  includes, for example, a controller  110  and a memory  120 . The user system  100  according to the present example embodiment has a function of identifying the type of the brushless DC motor  200 , as described later. In other words, the user system  100  can be used as an identification device for identifying the type of the brushless DC motor  200 . Therefore, in this specification, the user system  100  may be referred to as an identification device  100  in some cases. 
     The controller  110  mainly controls the entire user system  100  and can control power supply to the brushless DC motor  200 . The controller  110  can further identify the type of the brushless DC motor  200 . The controller  110  is, for example, a semiconductor integrated circuit such as a micro control unit (MCU) or a field programmable gate array (FPGA). 
     The memory  120  is, for example, a writable memory (for example, PROM), a rewritable memory (for example, flash memory), or a read-only memory. The memory  120  stores, for example, a control program having a command group for causing the controller  110  to identify the type of the brushless DC motor  200 . For example, the control program is temporarily expanded in a RAM (not shown) at the time of booting. The memory  120  does not need to be externally attached to the controller  110 , and may be mounted on the controller  110 . The controller  110  including the memory  120  is, for example, the above-described MCU. 
     The user system  100  includes a Vmot terminal and a GND terminal as connection terminals with the brushless DC motor  200 . The Vmot terminal is a terminal for a motor power supply. For example, a motor power supply voltage Vmot in a range from 7.0 to 13.8 V is supplied to the brushless DC motor  200  from the Vmot terminal. 
       FIG. 3  schematically shows an example of a more detailed block configuration inside the user system  100 . 
     The user system  100  further includes, for example, a DC power supply  151 , a resistance value detector  152 , and a discriminator  153 . When referring to the internal block configuration of the user system  100  or the identification device  100 , the components of the controller  110 , the DC power supply  151 , the resistance value detector  152 , and the discriminator  153  may be collectively referred to simply as “controller  110 ”. 
     The DC power supply  151  mainly generates a motor power supply voltage Vmot (for example, 7.0 to 13.8 V) to be supplied to the brushless DC motor  200  during normal motor driving. The normal motor driving means driving the motor in a state where the inverter  230  of the brushless DC motor  200  is operated by supplying power to the inverter  230 . 
     The resistance value detector  152  can generate a power supply voltage to be supplied to the brushless DC motor  200  and supply the power supply voltage to the brushless DC motor  200 , in identifying the type of the brushless DC motor  200 . The power supply voltage may be lower than the motor power supply voltage Vmot generated by the DC power supply  151 . Furthermore, the resistance value detector  152  can detect the identification resistance value of the brushless DC motor  200  based on the identification current flowing through the power supply line and the power supply voltage, in identifying the type of the brushless DC motor  200 . 
     The discriminator  153  identifies the type of the brushless DC motor  200  based on the identification resistance value of the brushless DC motor detected by the resistance value detector  152 . The discriminator  153  is typically mounted on the controller  110 . 
       FIG. 2  is referred to again. 
     The brushless DC motor  200  is, for example, a DC fan having an impeller. The brushless DC motor  200  is, for example, an axial fan, a centrifugal fan, a cross flow fan, or a sirocco fan. The brushless DC motor  200  typically includes a regulator  210 , a motor drive IC  220 , an inverter  230 , a circuit board CB on which those electronic components are mounted, a coil  240 , identification resistance circuitry  250  having at least one resistor  251 , and a Hall element  260 . For example, the regulator  210 , the motor drive IC  220 , the inverter  230 , and the Hall element  260  constitute a drive circuit for energizing the coil  240  to drive the motor. 
     The regulator  210  reduces the motor power supply voltage Vmot of, for example, 13.8 V to generate a power supply voltage Vcc (for example, 5 V) for the motor drive IC  220 . In the brushless DC motor  200 , the power supply voltage Vcc supplied to the motor drive IC  220  is preferably generated based on the motor power supply voltage Vmot. As a result, it is not necessary to provide a terminal for the power supply voltage Vcc in the brushless DC motor  200 , and the number of terminals and lead wires can be reduced. However, the power supply voltage Vcc may be supplied from the user system  100  to the brushless DC motor  200  separately from the motor power supply voltage Vmot. 
     The motor drive IC  220  includes, for example, an MCU  221  and is connected to the inverter  230 . The MCU  221  generates a PWM signal for controlling rotation of the motor. The motor drive IC  220  generates a control signal for controlling the inverter  230  according to the PWM signal and outputs the control signal to inverter  230 . 
     The MCU  221  incorporates a general timer function. By using this function, the MCU  221  can stop generating the PWM signal until a predetermined time elapses from the start of application of the power supply voltage Vcc. The predetermined time is, for example, about 0.1 s. Thus, driving of the inverter  230  can be stopped from the start of application of the power supply voltage Vcc until the predetermined time elapses. 
     The motor drive IC  220  monitors the rotation speed of the motor based on, for example, the output from the Hall element  260 , and generates a PWM signal according to the rotation speed of the motor. The output method is, for example, two pulses per rotation. However, a technique that does not use a Hall element is known. When such a technique is employed, the Hall element  260  is not essential. 
     The inverter  230  is electrically connected to motor drive IC  220  and coil  240  of the motor. The inverter  230  converts the power of the motor power supply to the power to be supplied to the fan motor under the control of the motor drive IC  220 , and energizes the coil  240  of the motor. 
     The coil  240  is a winding of the motor. 
     The identification resistance circuitry  250  has at least one resistor  251 . In one example embodiment, at least one resistor  251  is one resistor. For example, the identification resistor  251  has a resistance value that is ten times or more the DC resistance of the motor. With a large resistance value, it is possible to suppress the power loss due to the identification resistor  251  during normal motor driving. As the identification resistor  251 , for example, a resistor having a resistance value in a range from 1 kΩ to 100 kΩ can be used. 
     The resistance value of the identification resistor  251  differs for each type of a plurality of brushless DC motors. As the unique information of the brushless DC motor, a different unique resistance can be assigned to the identification resistor  251  for each type of the brushless DC motors. 
     For example, an identification resistor can be assigned as unique information of a brushless DC motor for each supplier that manufactures brushless DC motors. For example, a  20  kQ identification resistor can be assigned to a supplier A, a  30  kQ identification resistor can be assigned to a supplier B, and a  40  kQ identification resistor can be assigned to a supplier C. Further, identification resistors having resistance values different from these can be assigned to a plurality of suppliers, respectively. 
     For example, an identification resistor can be assigned as unique information for each product lot. For example, a  20  kQ identification resistor can be assigned to a product lot number A, a  30  kQ identification resistor can be assigned to a product lot number B, and a  40  kQ identification resistor can be assigned to a product lot number C. Further, a different identification resistance value can be assigned to each of a plurality of product lot numbers. Thus, there are as many types of the plurality of brushless DC motors as, for example, the number of suppliers or as the number of product lots to be managed. 
     The brushless DC motor  200  includes, for example, a circuit board CB on which a Vmot terminal and a GND terminal are disposed corresponding to the terminals on the user system  100  side. 
       FIG. 4  schematically shows other exemplary block configurations of the user system  100  and the brushless DC motor  200 . 
     The user system  100  may further include a light emitting element  130 . The light emitting element  130  has, for example, a plurality of light emitted diodes (LEDs). The plurality of LEDs are notification devices that notify the identification result of the type of the brushless DC motor  200 . For example, a plurality of LEDs can be provided by the number of types of a plurality of brushless DC motors. For example, if there are two types of brushless DC motors of suppliers A and B, two LEDs with different emission colors can be provided. For example, a red LED for supplier A and a blue LED for supplier B can be used. 
       FIG. 5  shows a flowchart of an identification method for identifying the type of the brushless DC motor  200  according to the present example embodiment. 
     The identification method according to the present example embodiment is a method used for the identification device  100 , for example. In the process of manufacturing a wide variety of products having motors, it is generally necessary to identify the type of the brushless DC motor  200  in order to prevent mixing of different types of motors. For example, the identification method of the present disclosure is suitably used for a method of inspecting compatibility of the brushless DC motor  200  with the user system  100  when manufacturing a product in a factory. For example, a step of checking compatibility of the brushless DC motor  200  can be incorporated as part of the product manufacturing process. 
     First, in a state where the terminals of the identification device  100  (user system  100 ) and the brushless DC motor  200  are electrically connected, an identification power supply voltage is supplied from the identification device  100  to the brushless DC motor  200 . For example, a power supply voltage of 13.8 V generated by the resistance value detector  152  is supplied to the brushless DC motor  200  as an identification power supply voltage. However, the motor power supply voltage Vmot may be supplied as the identification power supply voltage from the DC power supply  151  to the brushless DC motor  200  in the same manner as that during normal driving. 
     Generation of a PWM signal is stopped using the timer function of the MCU  221  of the motor drive IC  220  from the start of application of the identification power supply voltage until a predetermined time (for example, 0.1 s) elapses. Thereby, driving of the inverter  230  is stopped. In this state, although the identification power supply voltage is supplied to the inverter  230  but the PWM signal is not input, driving of the inverter  230  remains stopped. As a result, power is not supplied from the inverter  230  to the coil  240  of the motor. 
     With use of the identification device  100 , an identification resistance value is read as unique information of the brushless DC motor  200  in state where the inverter  230  is stopped. More specifically, an identification resistance value is read as unique information of the brushless DC motor  200  with use of the resistance value detector  152  of the identification device  100  in a state where the inverter  230  is stopped. When an identification power supply voltage is applied to the brushless DC motor  200 , a current flowing through the identification resistor  251  according to the identification resistance value flows through the resistance value detector  152 . This is because the motor current does not flow through the motor. That is, only the identification current including the information on the identification resistance value flows to the resistance value detector  152 . By measuring the identification current, the resistance value detector  152  can detect the identification resistance value from the current value and the identification power supply voltage. On the other hand, when the inverter  230  is driven, the motor current flows and the current fluctuation increases, so that it is difficult to detect the identification resistance value. 
     The discriminator  153  refers to a table and identifies the type of the motor based on the detected identification resistance value. 
       FIG. 6  illustrates a table used to identify the type of the brushless DC motor  200 . The table is a look-up table (LUT) for associating a plurality of brushless DC motor types with pieces of unique information of the plurality of brushless DC motors. The unique information of the brushless DC motor indicates the identification resistance value. The table is stored in the memory  120 , for example. As described above, a plurality of types of brushless DC motors exist, for example, for respective suppliers, and for example, there are three types of suppliers A, B, and C. For example, the type of motor can be represented by, for example, a 3-bit digital signal. 
     For example, the discriminator  153  may include an AD converter (not shown). The discriminator  153  converts the identification resistance value (analog value) detected by the resistance value detector  152  into a digital signal. The unique information of the brushless DC motor can also be represented by a digital value having the same bit width as the resolution of AD conversion. Note that the AD converter may be mounted on the resistance value detector  152  in the preceding stage. 
     When the identification of the type of the brushless DC motor by the identification device  100  is completed, the stopped state of the inverter  230  is released. Thereafter, for example, the motor power supply voltage Vmot is supplied from the DC power supply  151  to the brushless DC motor  200 . When a PWM signal is provided from the motor drive IC  220  to the inverter  230 , the inverter  230  starts driving of the motor in a normal state. 
     According to the identification method of the present example embodiment, it is possible to identify the type of the brushless DC motor  200  in a state where the inverter  230  is stopped. Identification of the type of the brushless DC motor  200  can be performed separately from the normal driving of the motor, so that the load on the identification device  100  can be reduced. Furthermore, communication by handshaking between the identification device  100  and the brushless DC motor  200  as in the related art is unnecessary. In addition, an existing power supply terminal can be used, and it is not necessary to newly provide a dedicated terminal for identification. Product cost can be reduced by reducing the number of parts. Since input and output terminals such as a PWM terminal and a TACH terminal are not particularly required for identification, an advantage is obtained particularly for identifying the type of a two-wire motor. 
     The identification method of the present disclosure is preferably used not only at the time of product manufacturing but also, for example, when replacing a failed brushless DC motor with a new brushless DC motor. It is possible to check whether or not the replaced brushless DC motor is compatible with the system. Also, for example, each product provided to a brushless DC motor is connected to the Internet. The so-called Internet of Things (IoT) is realized. For example, a supplier of an individual product equipped with a brushless DC motor can identify a product equipped with a specific brushless DC motor by analyzing big data including the unique information of the brushless DC motor. This can stabilize the quality, for example, by preventing occurrence of defects. 
       FIG. 7  shows a further specific example of a flowchart of the identification method for identifying the type of the brushless DC motor  200 . 
     As shown in  FIG. 7 , the identification method according to the present example embodiment can further include a step S 400  of notifying a result of identifying the type of the brushless DC motor  200 . 
     As an example of the notifying method, it is possible to notify a result of identifying the type of the brushless DC motor  200  using the light emitting element  130  (for example, a plurality of LEDs) shown in  FIG. 4 . The controller  110  of the identification device  100  causes the LED assigned to the identification target brushless DC motor  200 , among a plurality of LEDs assigned to the respective types of brushless DC motors, to emit light based on the result of identifying the type of the brushless DC motor  200 . Note that the light emitting element is not limited to an LED, and may be an element that gives notice by light. 
     For example, a red LED can be assigned to a supplier A, a blue LED can be assigned to a supplier B, and a green LED can be assigned to a supplier C. When the controller  110  of the identification device  100  identifies a brushless DC motor of the supplier C, the controller  110  can cause a green LED to emit light. Thus, for example, a factory worker can visually recognize whether or not the brushless DC motor to be identified is a motor of the supplier C. 
     As another example, a result of identifying the type of the brushless DC motor  200  can be notified using a display device (for example, a liquid crystal display) or a speaker. For example, the identification result can be displayed on a liquid crystal display as character information. For example, it is possible to change the pitch of the sound for each type of a plurality of brushless DC motors and make the speaker sound. 
     As another example, the controller  110  of the identification device  100  may temporarily write the identification result to the memory  120  or transmit it to another apparatus or device that needs the identification result. These modes are also examples of notifying the identification result. 
     In addition to the type information of the brushless DC motor, various types of information on the brushless DC motor such as the serial number, lot number, input power, input current, input voltage, motor temperature, rated current or rated voltage of the brushless DC motor can be associated with the identification resistance value. With the identification resistor associated with such information being provided on the brushless DC motor side, the identification device  100  can acquire various types of information regarding the brushless DC motor. 
       FIG. 8  schematically shows variations of the block configurations of the user system  100  and the brushless DC motor  200  according to the present example embodiment. 
     In the configuration of the variation, the identification resistance circuitry  250  includes an identification resistor  251  and a switch element  252  connected between one end of the identification resistor  251  and the GND line. However, the switch element  252  may be connected between the other end of the identification resistor  251  and the power supply line. As the switch element  252 , for example, a semiconductor switch element of a bipolar or unipolar transistor can be used. 
     For example, the motor drive IC  220  can control on/off of the switch element  252  at predetermined time intervals. The predetermined time interval is, for example, 1 ms. 
       FIG. 9  shows a more detailed flowchart of step S 200  for reading the identification resistance value in the processing flow of the identification method for identifying the type of the brushless DC motor  200  according to the present variation. 
     As in step S 210 A, generation of a PWM signal is stopped using the timer function of the MCU  221  of the motor drive IC  220  from the start of application of the identification power supply voltage until a predetermined time (for example, 0.1 s) elapses. 
     In a state where driving of the inverter  230  is stopped, the switch element  252  is turned on/off by the motor drive IC  220 . For example, the motor drive IC  220  turns on/off the switch element  252  every 1 ms. When the switch element  252  is turned on, the resistance value of the identification resistor  251  is set as an identification resistance value, and when the switch element  252  is turned off, a high impedance value is set as an identification resistance value. The resistance value of the identification resistor  251  is, for example, 20 kΩ. 
     In one example embodiment, for example, a state in which 20 kΩ is set as the identification resistance value can be assigned to the communication state H indicating the high-level digital information “1”, and a state in which the high impedance value is set as the identification resistance value can be assigned to a communication state L indicating the low-level digital information “0”. For example, by turning on/off the switch element  252  every ms by the motor drive IC  220 , character string information configured of various code words such as an ASCII code or a binary code can be transmitted to the identification device  100 . 
     For example, by turning on/off the switch element  252  in the order of “off, on, off, on, on, off, on, off”, the character string information of the ASCII code “01011010” for uppercase “Z” can be transmitted. The character string information includes information on a plurality of resistance values including 20 kΩ and a high impedance value. More specifically, the character string information is configured of digital information corresponding to an identification resistance value of 20 kΩ and digital information “0” corresponding to a high impedance value. The character string information is transmitted at a predetermined bit rate. The predetermined time interval can be determined based on the predetermined bit rate. 
     The character string information output from the brushless DC motor  200  is sequentially acquired using the resistance value detector  152  of the identification device  100 . When the resistance value detector  152  receives the character string information of the ASCII code “01011010” for the capital letter “Z”, the identification resistance value is detected in the order of “high impedance value, 20 kΩ, high impedance value, 20 kΩ, 20 kΩ, high impedance value, 20 kΩ, high impedance value”. 
     For example, the ASCII code “01000001” for uppercase “A” can be assigned to the supplier A, the ASCII code “01000010” for uppercase “B” can be assigned to the supplier B, and the ASCII code “01000011” for uppercase “C” can be assigned to the supplier C. The resistance value detector  152  identifies the type of the motor by referring to the table based on the acquired character string information, that is, a plurality of resistance value groups. 
       FIG. 10  illustrates a table used to identify the type of the brushless DC motor using an ASCII code as unique information. This table associates a plurality of brushless DC motor types with a plurality of ASCII codes. In this example, the ASCII code is the unique information of the brushless DC motor. 
     For example, after power is supplied to the brushless DC motor of the supplier A, the ASCII code “01000001” is output from the brushless DC motor. The identification device  100  can acquire the ASCII code “01000001” information and refer to the look-up table to specify that the motor to be identified is the brushless DC motor of the supplier A. 
     The identification resistance circuitry  250  of the brushless DC motor  200  has various other variations. 
     The identification resistor  251  can include a plurality of resistors connected in series or in parallel to each other. The identification resistance circuitry  250  can further include at least one switch element connected to the plurality of resistors. A resistance value group including at least one of a resistance value of each of the plurality of resistors and a combined resistance value that can be set by each of the resistance values is obtained, and information on the brushless DC motor  200  is detected based on the resistance value group by the resistance value detector  152 . In other words, the resistance value detector  152  identifies information on the brushless DC motor  200  based on a change in the resistance value due to turning on/off of the switch element. 
       FIGS. 11A to 11C  show circuit configurations of variations of the identification resistance circuitry  250 .  FIG. 12A  is a more detailed flowchart of step S 200  for reading the identification resistance value in the processing flow of the identification method for identifying the type of the brushless DC motor  200  including the identification resistance circuitry  250  shown in  FIG. 11A or 11B .  FIG. 12B  shows a more detailed flowchart of step S 200  for reading the identification resistance value in the processing flow of the identification method for identifying the type of the brushless DC motor  200  including the identification resistance circuitry  250  shown in  FIG. 11C . 
     As shown in  FIG. 11A , in one example embodiment, the identification resistance circuitry  250  has resistors  251 A,  251 B, and  251 C that are connected in parallel with each other. A switch element  252 A is connected in series to the resistor  251 A, a switch element  252 B is connected in series to the resistor  251 B, and a switch element  252 C is connected in series to the resistor  251 C. 
     As shown in  FIG. 12A , in step S 200 , generation of a PWM signal is stopped using the timer function of the MCU  221  of the motor drive IC  220  from the start of application of the identification power supply voltage until a predetermined time (for example, 0.1 s) elapses (step S 230 A). 
     In a state where driving of the inverter  230  is stopped, the switch elements  252 A,  252 B and  252 C connected to the resistors  251 A,  251 B, and  251 C are sequentially turned on (step S 230 B). The resistor  251 A has a resistance value r1, the resistor  251 B has a resistance value r2, and the resistor  251 C has a resistance value r3. For example, the resistance value r1 is 20 kΩ, the resistance value r2 is 30 kΩ, and the resistance value r3 is 40 kΩ. 
     The resistance values r1, r2, and r3 are sequentially acquired as identification resistance values by the resistance value detector  152  of the identification device  100  (step S 230 C). The resistance value detector  152  can identify the type of the brushless DC motor based on a combination of the three resistance values r1, r2, and r3. Thus, the number of identifiable types can be increased by increasing the number of identification resistors. 
     As shown in  FIG. 11B , in one example embodiment, the identification resistance circuitry  250  includes a plurality of resistors  251 A,  251 B, and  251 C connected to each other in series. A switch element  252 A is connected in series to the resistor  251 A, and a switch element  252 B is connected in series to the resistor  251 B. One ends of the switch element  252 A and the switch element  252 B are connected to each other. 
     For example, in a state where the switch elements  252 A,  252 B and  252 C are all turned off, a combined resistance (r1+r2+r3) of the resistance values r1, r2 and r3 is read by the resistance value detector  152 . Next, in a state where the switch element  252 B is turned on and the switch element  252 A is turned off, a combined resistance (r1+r2) of the resistance values r1 and r2 is read by the resistance value detector  152 . Finally, in a state where the switch element  252 A is turned on and  252 B is turned off, the resistance value r1 is read by the resistance value detector  152 . The type of the brushless DC motor  200  can be identified based on the combination of the read three resistance values. 
     As shown in  FIG. 11C , in one example embodiment, the identification resistance circuitry  250  has a variable resistance  253 . For example, the motor drive IC  220  can perform control to switch the resistance value of the variable resistance  253 . As shown in  FIG. 12B , while driving of the inverter  230  is stopped, the resistance value of the variable resistance is sequentially switched by the motor drive IC  220 , and a plurality of resistance values (resistance value group of variable resistance) set according to switching of the resistance value of the variable resistance are set to the brushless DC motor  200  (steps S 240 A and S 240 B). By sequentially reading out the plurality of resistance values by the resistance value detector  152 , it is possible to identify the type of the brushless DC motor  200  based on the combination of the resistance values (step S 240 C). 
     A brushless DC motor  200  according to the present example embodiment is different from the brushless DC motor  200  according to the first example embodiment in that a switching circuit  270  is provided as means for stopping the inverter  230 . Hereinafter, differences from the first example embodiment will be mainly described. 
       FIG. 13  schematically shows examples of typical block configurations of the user system  100  and the brushless DC motor  200  according to the present example embodiment. 
     The brushless DC motor  200  further includes the switching circuit  270  having a switch element  271  and an under voltage lockout circuit (UVLO)  272 . The switching circuit  270  switches connection and disconnection between the power supply line and the regulator  210  or the inverter  230 . 
     As the switch element  271 , for example, a semiconductor switch element such as a unipolar transistor (MOSFET, JFET) or a bipolar transistor can be used. As the switch element  271 , for example, an optocoupler, a thyristor, a mechanical relay, or the like may be used. 
       FIG. 14  shows an exemplary circuit configuration of the under voltage lockout circuit  272 . 
     The under voltage lockout circuit  272  has, for example, a plurality of resistors R 1 , R 2 , R 3 , and R 4 , a comparator AMP, and a switch element SW. The under voltage lockout circuit  272  is connected to a power supply line. The under voltage lockout circuit  272  disconnects the inverter  230  from the power supply line when the level of the input voltage Vin supplied via the power supply line is equal to or lower than a threshold. As a result, no input voltage is supplied to the inverter  230 . The threshold is set lower than the lower limit value of the range of the operating power supply voltage (for example, 7 to 13.8 V) used for normal motor driving. The threshold can be set to, for example, about 5.0 V. 
     The under voltage lockout circuit  272  compares the input voltage with the reference voltage Vref. The reference voltage Vref corresponds to the threshold described above. For example, when a P-type semiconductor switch element is used as the switch element  271 , if the input voltage is equal to or lower than the reference voltage Vref, the under voltage lockout circuit  272  outputs a high-level voltage to turn off the switch. On the other hand, when the input voltage is higher than the reference voltage Vref, the under voltage lockout circuit  272  outputs a low-level voltage to turn on the switch element  271 . 
     Note that, in this example, a P-type semiconductor switch element is illustrated as the switch element  271 . However, an N-type semiconductor switch element, a PNP transistor, an NPN transistor, or the like may be used depending on the circuit configuration. 
       FIG. 15  shows a flowchart of an identification method for identifying the type of the brushless DC motor  200  according to the present example embodiment. 
     In supplying the identification power supply voltage, a level equal to or lower than the above-described threshold, that is, a low-level input voltage different from that in the normal driving, is supplied via the power supply line. The identification power supply voltage is supplied from, for example, the resistance value detector  152  (see  FIG. 3 ) of the identification device  100 . However, as described above, this may be supplied from the DC power supply  151  (see  FIG. 3 ). 
     By supplying a low-level identification power supply voltage, the switching circuit  270  disconnects the inverter  230  from the power supply line. As a result, the power supply to the inverter  230  is cut off, and the inverter  230  is stopped. Since the regulator  210  is also disconnected from the power supply line by the switching circuit  270 , the power supply voltage Vcc of the motor drive IC is not generated. Therefore, motor drive IC  220  also stops. 
     In a state where the inverter  230  is stopped, an identification current including information indicating the identification resistance value of the identification resistor  251  flows through the power supply terminal of the brushless DC motor  200 . As in step S 210 B described in the first example embodiment, in a state where the inverter  230  is stopped, the identification resistance value is read as unique information of the brushless DC motor  200  using the identification device  100 . When a low-level identification power supply voltage is applied to the brushless DC motor  200 , no motor current flows through the inverter  230 , but an identification current flows through the identification resistor  251  according to the identification resistance value. 
     The type of the brushless DC motor  200  is identified by the discriminator  153  based on the detected identification resistance value with reference to, for example, the table illustrated in  FIG. 6  (step S 300 ). 
     According to the identification method of the present example embodiment, unlike the conventional hand handshake, the type of the brushless DC motor  200  can be identified by reading the identification resistance value while the motor drive IC  220  (mainly the MCU  221 ) is not activated and the inverter  230  is stopped. 
       FIG. 16  schematically shows examples of typical block configurations of the user system  100 , an identification device  100 A, and the brushless DC motor  200 . 
     The identification device  100 A according to the present example embodiment is a device different from the user system  100 , unlike the first or second example embodiment. The identification device  100 A includes, for example, an MCU  110 A equipped with a DC power supply  151 , a resistance value detector  152 , and a discriminator  153 , and a light emitting element  130 . Note that, for simplicity,  FIG. 16  does not show the DC power supply  151 , the resistance value detector  152 , and the discriminator  153 . The identification device  100 A includes a Vmot terminal and a GND terminal as terminals necessary for identifying the type of the brushless DC motor  200 . 
     The user system  100 , the identification device  100 A, and the brushless DC motor  200  are electrically connected to each other between the Vmot terminal and the GND terminal. The identification power supply voltage can be supplied from the identification device  100 A to the brushless DC motor  200  via the Vmot terminal. 
     When the power supply is turned on, an identification current including information on the identification resistance value flows through the power supply line. The identification device  100 A can identify the type of the brushless DC motor  200 , for example, according to the processing flow shown in  FIG. 5  or  FIG. 15 . The MCU  110 A may transmit the identification result to the controller  110  of the user system  100 . 
       FIG. 17  schematically shows other exemplary block configurations of the user system  100 , the identification device  100 A, and the brushless DC motor  200 . 
     The identification device  100 A is electrically connected to the user system  100  and the brushless DC motor  200 , for example, via a test point (TP). TP 1  is a TP for identification power supply. TP 2  is a TP for GND. A dedicated probe is connected to the identification device  100 A, and the probe can be applied to the TP to identify the type of the brushless DC motor  200 . 
     The outline of one aspect of the present disclosure is as described below. 
     An identification method according to an exemplary example embodiment of the present disclosure is an identification method used for an identification device that identifies information on a brushless DC motor output from the brushless DC motor. The brushless DC motor  200  includes, for example, at least one resistor  250  connected between a power supply line and a GND line, an inverter  230  that drives the motor, and a switching circuit  270  that switches connection and disconnection between the power supply line and the inverter that are shown in  FIG. 13 . As described with reference to  FIG. 15 , the identification method includes supplying the identification power supply voltage from the identification device  100  to the brushless DC motor  200  via the power supply line, disconnecting the inverter  230  from the power supply line by the switching circuit  270 , reading the identification resistance value of the at least one resistor  251  in a state where driving of the inverter  230  is stopped, and identifying information on the brushless DC motor  200  based on the read identification resistance value of the at least one resistor  251 . The information on the brushless DC motor  200  includes, for example, identification information of the brushless DC motor  200 , serial number of the brushless DC motor  200 , lot number, input power, input current, input voltage, motor temperature, rated current or rated voltage, and the like. 
     According to such an identification method, the identification resistance value can be read without particularly operating the MCU  221  of the brushless DC motor  200 , in a state where the inverter  230  of the brushless DC motor  200  is stopped. This provides a brushless DC motor identification method capable of identifying information on the brushless DC motor without performing a handshake. 
     In one example embodiment, as shown in  FIG. 13 , the switching circuit  270  includes an under voltage lockout circuit  272  that disconnects the inverter  230  from the power supply line when the level of the input voltage is equal to or lower than a threshold. In supplying an input voltage, an input voltage of a level equal to or lower than a threshold is supplied through a power supply line. The threshold can be, for example, 5.0 V. 
     According to such an identification method, driving of the inverter  230  can be reliably stopped using the under voltage lockout circuit  272 . 
     In one example embodiment, the threshold is set lower than the lower limit value of a range of the operating power supply voltage used for normal motor driving. The range of the operating power supply voltage is, for example, from 7.0 V to 13.8 V. 
     According to such an identification method, the inverter  230  can be disconnected from the power supply line when the input voltage is equal to or lower than the lower limit value of the range of the operating power supply voltage by using the under voltage lockout circuit  272 . 
     In one example embodiment, the information on the brushless DC motor  200  indicates the type of the brushless DC motor  200 . For example, as described with reference to  FIG. 5 , a unique resistance that is different for each type of the plurality of brushless DC motors is assigned to at least one resistor  251 , and in reading the identification resistance value, the resistance value of the unique resistance is read by the resistance value detector  152  as unique information of the brushless DC motor  200 , and in identifying the information on the brushless DC motor  200 , the type of the brushless DC motor  200  is identified based on the read value of the unique resistance. 
     According to such an identification method, it is possible to identify the type of the brushless DC motor  200  without performing a handshake. 
     In one example embodiment, in identifying the type of the brushless DC motor  200 , with reference to a look-up table that associates a plurality of types of brushless DC motors and pieces of unique information of the plurality of brushless DC motors, the type of the brushless DC motor  200  is identified based on the value of the read unique resistance. The look-up table is exemplified in  FIG. 6 , for example. 
     According to such an identification method, it is possible to associate the types of the plurality of brushless DC motors with pieces of unique information of the plurality of brushless DC motors using the lookup table. 
     In one example embodiment, the identification method further includes notifying the result of identifying the type of the brushless DC motor  200  using the identification device  100 . 
     According to such an identification method, for example, as described above, the controller  110  of the identification device  100  may temporarily write the identification result to the memory  120 , or transmit it to another apparatus or device that needs the identification result. Further, it is possible to notify the result of identifying the type of the brushless DC motor  200  using a display device (for example, a liquid crystal display) or a speaker. 
     In one example embodiment, the identification method further includes allowing, from among a plurality of light emitting elements  130  each assigned to each of a plurality of types of brushless DC motors, that is, a plurality of LEDs for example, a light emitting element assigned to the brushless DC motor  200  to be identified to emit light based on the result of identifying the type of the brushless DC motor. 
     According to such an identification method, for example, a red LED can be assigned to a supplier A, a blue LED can be assigned to a supplier B, and a green LED can be assigned to a supplier C. When the controller  110  of the identification device  100  identifies the brushless DC motor of the supplier C, the green LED is allowed to emit light. 
     In one example embodiment, the brushless DC motor  200  is a DC fan having an impeller, for example. 
     According to such an identification method, for example, the type of the brushless DC motor  200  such as an axial fan, a centrifugal fan, a cross flow fan, or a sirocco fan can be identified. 
     The identification device  100  according to an example embodiment of the present disclosure is an identification device that identifies information on a brushless DC motor. As described with reference to  FIG. 13 , the brushless DC motor  200  includes at least one resistor  251  connected between a power supply line and a GND line, the inverter  230  that drives the motor, and the switching circuit  270  that switches connection and disconnection between the power supply line and the inverter  230 . The identification device  100  includes the power supply terminal Vmot for supplying an input voltage to the brushless DC motor  200  via a power supply line, and the controller  110  for identifying information on the brushless DC motor  200 . As described with reference to  FIG. 15 , the controller  110  supplies the input voltage to the brushless DC motor  200 , and in a state where the inverter  230  is disconnected from the power supply line by the switching circuit  270  to stop driving of the inverter  230 , the controller reads the identification resistance value of at least one resistor  251 , and identifies the information on the brushless DC motor  200  based on the read identification resistance value of at least one resistor  251 . 
     According to such an identification device, the identification resistance value can be read without particularly operating the MCU  221  of the brushless DC motor  200 , in a state where the inverter  230  of the brushless DC motor  200  is stopped. This provides a brushless DC motor identification device capable of identifying information on the brushless DC motor without performing a handshake. 
     As described with reference to  FIG. 13 , the brushless DC motor  200  according to an example embodiment of the present disclosure includes the circuit board CB, the power supply terminal Vmot for supplying an input voltage from the outside, the power supply terminal Vmot being disposed on the circuit board CB, the inverter  230  that drives the motor, at least one resistor  251  connected between a power supply line connected to the power supply terminal Vmot and the GND line, the at least one resistor  251  having a resistance value larger than the DC resistance of the motor, and the switching circuit  270  for switching connection and disconnection between the power supply line and the inverter  230 , the switching circuit  270  including an under voltage lockout circuit  272  that disconnects the inverter  230  from the power supply line when the level of the input voltage is equal to or lower than a threshold. In a state where the input voltage at the level equal to or lower than the threshold is supplied via the power supply terminal Vmot and where the inverter  230  is disconnected from the power supply line by the switching circuit  270  to stop driving of the inverter  230 , a current including information indicating the identification resistance value of at least one resistor  251  flows through the power supply terminal Vmot. The threshold can be, for example, 5.0 V. 
     According to such a brushless DC motor, the brushless DC motor  200  capable of transmitting the identification resistance value to the identification device  100 , in a state where the inverter  230  of the brushless DC motor  200  is stopped, is provided. 
     In one example embodiment, the threshold is lower than the lower limit value of the range of the operating power supply voltage used for normal motor driving. The range of the operating power supply voltage is, for example, from 7.0 V to 13.8 V. 
     According to such a brushless DC motor, the inverter  230  can be disconnected from the power supply line using the under voltage lockout circuit  272 . 
     In one example embodiment, the identification resistor  251  has a resistance value that is at least 10 times the DC resistance of the motor. 
     According to such a brushless DC motor, it is possible to suppress power loss due to the identification resistor  251  during normal motor driving. 
     Example embodiments of the present disclosure are widely used in various devices including various fan motors, such as a personal computer, a game machine, a vacuum cleaner, a dryer, a washing machine, and a refrigerator. 
     Features of the above-described example embodiments and the modifications thereof may be combined appropriately as long as no conflict arises. 
     While example embodiments of the present disclosure have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present disclosure. The scope of the present disclosure, therefore, is to be determined solely by the following claims.