Motor drive control device, fan unit, and motor drive control method

Abstract

A motor drive control device (1) is characterized by comprising a signal input terminal (P3) for inputting a drive command signal (Sc) that indicates a drive state for a motor (40), a control circuit (2) that identifies a designated rotation direction on the basis of the drive command signal inputted into the signal input terminal and generates a drive control signal (Sd) for controlling the rotation of the motor such that the motor rotates in the identified rotation direction, and a drive circuit (3) that drives the motor on the basis of the drive control signal. The motor drive control device is also characterized in that the control circuit monitors the operating state of the motor, measures a continuation time (T) that is the time after it has been detected that the motor is stopped that the drive command signal stays at a first logic level (for example, a low level), and identifies the rotation direction on the basis of the length of the continuation time.

Description

Motor Drive Control Device, Fan Unit, and Motor Drive Control Method

[0001] The present invention relates to a motor drive control device, a fan unit, and a motor drive control method, and more particularly, to a motor drive control device that controls the rotation of a motor in a fan unit.

[0002] Conventionally, a fan (fan motor) is widely known as a cooling device that discharges heat generated inside an electrical device or the like to the outside and cools the inside of the device. The fan has a motor and an impeller connected to the output shaft of the motor, and generates an air flow (wind) as the impeller rotates in response to the rotation of the output shaft of the motor. The fan constitutes a single fan unit together with, for example, a motor drive control device for controlling the drive of the motor of the fan.

[0003] Generally, in a fan unit, the motor drive control device drives the motor in response to an instruction from a higher-level device, causing the fan (motor) to rotate in one direction at a constant rotational speed. On the other hand, if the fan unit is used for a long period of time, dust may adhere to the impeller or the like, making it difficult for the motor to rotate. This is particularly true for fans used outdoors, where dust, sand, and the like are likely to adhere. Therefore, a fan unit having a function of rotating the fan in the reverse direction for the purpose of dust removal is known. [[ID=I1]]

[0004] For example, Patent Document 1 discloses a technique in which the fan rotates forward when the duty ratio of a PWM signal specifying the rotational speed is between 5% and 45%, and the fan rotates backward when the duty ratio of the PWM signal is between <000001:55% and 95%.

[0005] U.S. Patent No. 10,060,438

[0006] However, according to the technique disclosed in Patent Document 1, since the rotation direction of the motor (fan) is specified by the range of the duty ratio of the PWM signal, there is a problem that the range of rotational speeds that can be set by the duty ratio of the PWM signal becomes narrow.

[0007] This invention has been made in view of the above-mentioned problems, and aims to enable switching of the motor's rotation direction while ensuring a wide range of motor rotation speed settings.

[0008] A motor drive control device according to a typical embodiment of the present invention comprises: a signal input terminal for inputting a drive command signal that indicates the drive state of a motor; a control circuit that generates a drive control signal for controlling the rotation of the motor so that the motor rotates in the specified rotation direction, based on the drive command signal input to the signal input terminal; and a drive circuit that drives the motor based on the drive control signal. The control circuit monitors the operating state of the motor, detects that the motor has stopped, measures the duration for which the drive command signal remains at a first logic level, and determines the rotation direction based on the length of the duration.

[0009] According to the motor drive control device of the present invention, it is possible to switch the rotation direction of the motor while ensuring a wide range of setting ranges for the motor's rotation speed.

[0010] This is a block diagram showing the configuration of a fan unit according to an embodiment. This is a schematic perspective view showing the external appearance of a fan unit according to an embodiment. This is a diagram illustrating the method for determining a specified rotation direction by a motor drive control device according to an embodiment. This is a flowchart showing an example of the processing flow by a motor drive control device according to an embodiment. This is a diagram showing an example of the relationship between the drive command signal and the operating state of the fan in a fan unit according to an embodiment.

[0011] 1. Outline of Embodiments First, a general overview of a typical embodiment of the invention disclosed in this application will be given. In the following description, as an example, reference numerals on the drawings corresponding to the components of the invention are indicated in parentheses.

[0012] [1] A motor drive control device (1) according to a typical embodiment of the present invention comprises: a signal input terminal (P3) for inputting a drive command signal (Sc) that indicates the drive state of a motor (40); a control circuit (2) that, based on the drive command signal input to the signal input terminal, identifies a specified direction of rotation and generates a drive control signal (Sd) for controlling the rotation of the motor so that the motor rotates in the identified direction of rotation; and a drive circuit (3) that drives the motor based on the drive control signal, wherein the control circuit monitors the operating state of the motor, detects that the motor has stopped, measures a duration (T) which is the time during which the drive command signal remains at a first logic level (e.g., low level), and identifies the direction of rotation based on the length of the duration.

[0013] [2] In the motor drive control device described in [1] above, the control circuit may determine that a first direction (for example, forward direction) is specified as the direction of rotation when the duration is less than a first reference time (T1), and determine that a second direction (reverse direction) opposite to the first direction is specified as the direction of rotation when the duration is greater than the first reference time and less than a second reference time (T2).

[0014] [3] In the motor drive control device described in [2] above, the control circuit may determine that the rotation direction specified before detecting that the motor was stopped is specified when the duration is greater than the second reference time.

[0015] [4] In the motor drive control device described in [2] above, an initial value may be set in advance as the specified value for the rotation direction, and the control circuit may determine that the rotation direction corresponding to the initial value is specified when the duration is greater than the second reference time.

[0016] [5] A motor drive control device according to any one of [1] to [4] above, wherein the control circuit includes a rotation state signal generation unit (25) that detects the rotation state of the motor and generates and outputs a rotation state signal (So) having a frequency corresponding to the actual rotation speed of the motor, and a drive control signal generation unit (20) that determines whether the motor is rotating based on the rotation state signal and generates the drive control signal, wherein the drive control signal generation unit includes a motor stop determination unit (24) that determines whether the motor is stopped, a drive command analysis unit (21) that, when it is determined that the motor is stopped, measures the duration, identifies the specified rotation direction based on the duration, generates information on the specified rotation direction, identifies the rotation speed based on the duty cycle of the drive command signal and generates information on the specified rotation speed, and a signal generation unit (22) that generates the drive control signal based on the specified rotation direction information and the specified rotation speed information.

[0017] [6] In the motor drive control device described in [5] above, the motor stop determination unit may determine that the motor is not stopped when the frequency of the rotation status signal is equal to or greater than a threshold, and determine that the motor is stopped when the frequency of the rotation status signal is lower than the threshold.

[0018] [7] A fan unit (6) according to a typical embodiment of the present invention is characterized by comprising the motor, an impeller (41) connected to the output shaft of the motor, and a motor drive control device (1) according to any one of [1] to [6] above.

[0019] [8] A typical embodiment of the present invention is a motor drive control method for controlling the rotation of a motor (40) by a motor drive control device (1). This method includes a first step (S11 to S21) of generating a drive control signal (Sd) for controlling the rotation of the motor based on a drive command signal (Sc) that indicates the drive state of the motor, and a second step of driving the motor based on the drive control signal. The first step is characterized by including a third step (S11) of monitoring the operating state of the motor and detecting that the motor is stopped, a fourth step (S12 to S14) of measuring a duration (T) which is the time that the state in which the drive command signal is at a first logic level continues after detecting that the motor is stopped, a fifth step (S15 to S19) of identifying a specified direction of rotation based on the length of the duration, and a sixth step (S20, S21) of generating the drive control signal so that the motor rotates in the direction of rotation identified in the fifth step.

[0020] 2. Specific Examples of Embodiments Hereinafter, specific examples of embodiments of the present invention will be described with reference to the figures. In the following description, common components in each embodiment will be denoted by the same reference numerals, and repeated explanations will be omitted.

[0021] <Embodiment> Figure 1 is a block diagram showing the configuration of the fan unit 6 according to the embodiment. Figure 2 is a schematic perspective view showing the external appearance of the fan unit 6 according to the embodiment.

[0022] The fan unit 6 according to this embodiment is a device that generates wind by rotating an impeller (vanewheel). The fan unit 6 can be used, for example, as a cooling device that expels heat generated inside a piece of equipment to the outside and cools the inside of that equipment.

[0023] As shown in Figure 1, the fan unit 6 comprises a fan 4 and a motor drive control device 1. The fan 4 comprises a motor 40 and an impeller 41 connected to the output shaft (rotating shaft) of the motor 40. The fan 4 is, for example, an axial flow fan. The motor 40 is, for example, a three-phase brushless DC (Direct Current) motor.

[0024] The motor drive control device 1 is a device for controlling the drive of the motor 40. As shown in Figure 1, the motor drive control device 1 includes, for example, a plurality of external terminals, a control circuit 2, a drive circuit 3, and a position detector 5. Note that the components of the motor drive control device 1 shown in Figure 1 are only a part of the whole, and the motor drive control device 1 may have other components in addition to those shown in Figure 1.

[0025] As shown in Figure 1, the motor drive control device 1 has a plurality of external terminals, such as a power terminal P1, a ground terminal P2, a signal input terminal P3 for inputting signals, and a signal output terminal P4 for outputting signals.

[0026] The fan unit 6 constitutes a so-called four-wire fan motor. Specifically, as shown in Figures 1 and 2, a signal line 49 is connected to the power terminal P1, a signal line 50 is connected to the ground terminal P2, a signal line 51 is connected to the signal input terminal P3, and a signal line 52 is connected to the signal output terminal P4. As shown in Figure 2, each of the signal lines 49 to 51 is brought out to the outside of the casing 47 of the fan unit 6 and connected to a higher-level device (not shown) and a power supply device (not shown) located outside the fan unit 6, thereby electrically connecting the motor drive control device 1 with the power supply device and the higher-level device.

[0027] A DC voltage Vdc is supplied to the power terminal P1 from the power supply unit via the signal line 49. This supplies the power voltage to the control circuit 2 and the drive circuit 3. Alternatively, a regulator may be provided in the motor drive control device 1, which generates a new DC voltage from the DC voltage Vdc and supplies it to the control circuit 2 as the power voltage. The ground terminal P2 is connected to the ground potential GND via the signal line 50.

[0028] As described later, a drive command signal Sc, which instructs the motor's drive state, is input to the signal input terminal P3. For example, the signal input terminal P3 is connected to a higher-level device, and the drive command signal Sc output from the higher-level device is input to the signal input terminal P3. As described later, the signal output terminal P4 outputs a rotation state signal So. For example, the signal output terminal P4 is connected to a higher-level device, and the rotation state signal So output from the control circuit 2 is input to the higher-level device from the signal output terminal P4.

[0029] Furthermore, if the fan unit 6 receives power from a higher-level device, the power terminal P1 and ground terminal P2 may be connected to the power line and ground line within the higher-level device, respectively.

[0030] The position detector 5 is a device for detecting the rotational position of the rotation axis (rotor) of the motor 40. The position detector 5 is, for example, a Hall element. For example, three Hall elements corresponding to each phase (U phase, V phase, W phase) of the motor 40 are arranged around the rotor (magnet) of the motor 40 at approximately equal intervals from each other. The number of Hall elements is not particularly limited.

[0031] The position detector 5 outputs a rotational position detection signal (Hall signal) Sh to the control circuit 2. The rotational position detection signal Sh is a signal indicating the rotational position of the motor 40, that is, a signal corresponding to the rotational position of the rotor (magnet) of the motor 40.

[0032] The position detector 5 only needs to have the function of detecting the position information of the rotation axis (rotor) of the motor 40 and outputting it as an electrical signal, and may be, for example, a rotary encoder. Alternatively, the rotation position of the motor 40 may be detected by a so-called sensorless method in which the control circuit 2 detects the back electromotive force induced in each phase (U phase, V phase, W phase) of the motor 40 and detects the rotation position of the motor 40 based on that back electromotive force, without providing the position detector 5.

[0033] Control circuit 2 is a circuit that performs overall control in the motor drive control device 1. Control circuit 2 generates a drive control signal Sd for controlling the rotation of the motor 40. Control circuit 2 is a program processing device (for example, various computers such as a microcontroller) in which a processor such as a CPU, various storage devices such as RAM and ROM, and peripheral circuits such as a counter (timer), A / D conversion circuit, D / A conversion circuit, clock generation circuit, and input / output I / F circuit are connected to each other via a bus or dedicated line. Details of control circuit 2 will be described later.

[0034] The drive circuit 3 is a circuit that drives the motor 40 based on the drive control signal Sd. The drive circuit 3 includes, for example, an inverter circuit (not shown) and a pre-drive circuit (not shown). The inverter circuit outputs a drive signal to the motor 40 based on the output signal output from the pre-drive circuit and energizes the three-phase coils of the motor 40. By switching the order in which the three-phase coils are energized, the rotation direction of the motor 40 can be switched. For example, the inverter circuit is configured by arranging a pair of series circuits of two switch elements connected in series between a DC voltage Vdc and ground potential GND for each phase coil. In each pair of two switch elements, the terminals of each phase of the motor 40 are connected to the connection point between the switch elements.

[0035] The pre-drive circuit generates an output signal to drive the inverter circuit based on the drive control signal Sd and outputs it to the inverter circuit. For example, the pre-drive circuit generates and outputs a drive signal to drive each switch element of the inverter circuit based on the drive control signal Sd.

[0036] The drive signal output from the pre-drive circuit turns on / off each switch element that makes up the inverter circuit, thereby supplying power to each phase of the motor 40 and causing the rotor of the motor 40 to rotate.

[0037] In the motor drive control device 1, at least a portion of the functional parts of the control circuit 2 and the drive circuit 3 may be packaged as a single semiconductor integrated circuit (IC), or the drive circuit 3 and the control circuit 2 may each be packaged as separate semiconductor integrated circuit devices.

[0038] Next, we will explain control circuit 2 in detail.

[0039] The control circuit 2 has the function of generating a drive control signal Sd for controlling the rotation of the motor 40 so that the motor 40 reaches the rotation state specified by the drive command signal Sc, based on the drive command signal Sc input to the signal input terminal P3.

[0040] Here, the drive command signal Sc is a signal that indicates the target drive state of the motor 40. The drive command signal Sc includes, for example, information that specifies the rotation direction of the motor 40 and information that specifies the target rotation speed, which is the target value of the rotation speed of the motor 40. For example, the drive command signal Sc is a binary signal and has a voltage corresponding to a first logic level or a second logic level opposite to the first logic level. In this embodiment, as an example, the first logic level is set to a low level (e.g., ground voltage) and the second logic level is set to a high level (e.g., DC voltage Vdc), but it is not limited to this.

[0041] Furthermore, in the fan unit 6, a first direction and a second direction opposite to the first direction can be specified as the rotation direction of the motor 40 (fan 4). In this embodiment, for example, the first direction may be referred to as the "forward direction" and rotation in the forward direction as "positive rotation," while the second direction may be referred to as the "reverse direction" and rotation in the reverse direction as "negative rotation."

[0042] Specifically, the control circuit 2 monitors the operating state of the motor 40, and after detecting that the motor 40 is stopped, measures the duration T, which is the time during which the drive command signal Sc remains at the first logic level, and determines the specified direction of rotation based on the length of the duration T.

[0043] More specifically, when the control circuit 2 detects that the motor 40 has stopped, it determines that the first direction is specified as the rotation direction, and when the continuous time T is greater than the reference time T1 and less than the reference time T2, it determines that the second direction opposite to the first direction is specified as the rotation direction. Further, when the continuous time T is greater than the reference time T2, the control circuit 2 determines that the rotation direction before detecting that the motor 40 has stopped is specified.

[0044] Further, when a pulse signal (PWM signal) as the drive command signal Sc is input, the control circuit 2 specifies the rotation speed specified based on the PWM signal, and generates a drive control signal Sd so that the motor 40 rotates in the specified rotation direction at the specified rotation speed.

[0045] As shown in FIG. 1, the control circuit 2 has a drive control signal generation unit 20 and a rotation state signal generation unit 25 as functional blocks for realizing the above-described functions. These functional blocks are realized, for example, in the control circuit 2 when the CPU executes various arithmetic processes according to a program stored in the memory and controls peripheral circuits such as an A / D conversion circuit and an input / output interface circuit based on the processing results. Note that part or all of the drive control signal generation unit 20 and the rotation state signal generation unit 25 may be realized by a dedicated circuit (such as a dedicated hardware logic circuit).

[0046] The drive control signal generation unit 20 is a functional block that generates a drive control signal Sd so that the motor 40 rotates in the first direction or the second direction opposite to the first direction. Details of the drive control signal generation unit 20 will be described later.

[0047] The rotation state signal generation unit 25 is a functional block that generates a rotation state signal So indicating the rotation state of the motor. The rotation state signal generation unit 25 generates a rotation state signal So indicating the rotation state of the motor based on the rotation position detection signal Sh output from the position detector 5 and outputs it from the signal output terminal P4. Specifically, the rotation state signal generation unit 25 generates a rotation state signal So having a frequency based on the rotation speed of the motor 40 and a predetermined duty ratio, and outputs it from the signal output terminal P4.

[0048] Here, the rotation state signal So is, for example, a FG (Frequency Generator) signal having a frequency corresponding to the rotation speed of the motor 40 and a duty ratio of 50%. The rotation state signal generation unit 25 generates a FG signal by a known method based on, for example, a hall signal as the rotation position detection signal Sh.

[0049] Note that the rotation state signal generation unit 25 may output the rotation state signal So including information indicating the rotation direction of the motor 40. For example, when the motor 40 is rotating forward, the rotation state signal generation unit 25 may output, from the signal output terminal P4, as the rotation state signal So, a signal having a frequency corresponding to the period of the rotation position detection signal Sh and a duty ratio of 50%. On the other hand, when the motor 40 is rotating backward, the rotation state signal generation unit 25 may output, from the signal output terminal P4, as the rotation state signal So, a signal having a frequency corresponding to the period of the rotation position detection signal Sh and a duty ratio other than 50%.

[0050] Next, the details of the drive control signal generation unit 20 will be described. The drive control signal generation unit 20 determines whether the motor 40 is rotating based on the rotation state signal So, and generates a drive control signal Sd.

[0051] For example, as shown in FIG. 1, the drive control signal generation unit 20 includes a drive command analysis unit 21, a signal generation unit 22, a rotation speed calculation unit 23, and a motor stop determination unit 24.

[0052] The motor stop determination unit 24 is a functional unit that determines whether the motor 40 has stopped. Specifically, the motor stop determination unit 24 monitors the rotation state signal So and determines whether the motor 40 has stopped based on the frequency or period of the rotation state signal So. For example, the motor stop determination unit 24 determines that the motor 40 has stopped when the frequency of the rotation state signal So is below a threshold value, and determines that the motor 40 has not stopped (the motor 40 is rotating) when the frequency of the rotation state signal So is greater than the threshold value. The above threshold value may be set to an appropriate value according to the application to which the fan unit 6 is applied. For example, the above threshold value is 10 Hz.

[0053] The drive command analysis unit 21 is a functional unit that analyzes the drive command signal Sc input to the signal input terminal P3. The drive command analysis unit 21 analyzes the drive command signal Sc to identify the specified rotation direction and generates information indicating the specified rotation direction (also referred to as "specified rotation direction information") Str. More specifically, when the motor stop determination unit 24 determines that the motor 40 is stopped, the drive command analysis unit 21 measures the duration T, identifies the specified rotation direction based on the duration T, and generates the specified rotation direction information Str.

[0054] Figure 3 is a diagram illustrating a method for determining a specified rotation direction using a motor drive control device according to an embodiment.

[0055] In Figure 3, the horizontal axis represents time. Furthermore, from top to bottom in Figure 3, the motor's operating state, the waveform of the drive command signal Sc input to the signal input terminal P3, and the specified rotation direction are shown, respectively. As shown in Figure 3, it is assumed that a PWM signal is input to the motor drive control device 1 as the drive command signal Sc before time t0, and that the motor 40 is rotating in the forward direction.

[0056] As shown in Figure 3, if the input of the PWM signal as the drive command signal Sc stops at time t0, the signal generation unit 22 generates a drive control signal Sd so that the rotation speed of the motor 40 becomes zero, as will be described later, and the rotation speed of the motor 40 gradually decreases. Then, at time t1 when the rotation speed has fallen below a predetermined threshold, the motor stop determination unit 24 determines that the motor 40 has stopped.

[0057] At time t1, the motor stop determination unit 24 determines that the motor 40 has stopped, and the drive command analysis unit 21 starts processing to identify the specified direction of rotation.

[0058] First, the drive command analysis unit 21 starts measuring the duration T. Next, the drive command analysis unit 21 monitors for the presence or absence of a drive command signal Sc input. If a PWM signal is input as the drive command signal Sc after the start of measuring the duration T, the drive command analysis unit 21 stops measuring the duration T and compares the duration T with reference times T1 and T2 (T1 < T2).

[0059] For example, if a PWM signal as a drive command signal Sc is input during the period from time t1 to time t2 in Figure 3, that is, if the duration T is less than the reference time T1, the drive command analysis unit 21 determines that the first direction (forward direction / positive rotation) is specified as the direction of rotation.

[0060] For example, if a PWM signal as a drive command signal Sc is input during the period from time t2 to time t3 in Figure 3, that is, if the duration T is greater than the reference time T1 and less than the reference time T2, the drive command analysis unit 21 determines that the second direction (reverse direction / negative rotation) is specified as the direction of rotation.

[0061] For example, if a PWM signal as a drive command signal Sc is input after time t3 in Figure 3, that is, if the duration T is greater than the reference time T2, the drive command analysis unit 21 determines that the direction of rotation specified is the direction in which the motor 40 was rotating immediately before it stopped.

[0062] The drive command analysis unit 21 generates and outputs specified rotation direction information Str, which includes the rotation direction information identified by the method described above.

[0063] Furthermore, the drive command analysis unit 21 analyzes the PWM signal as the input drive command signal Sc to identify the specified target rotational speed and generates information indicating the specified target rotational speed (also referred to as "specified rotational speed information") Stv. For example, information on a table or function representing the correspondence between the duty cycle of the drive command signal Sc and the target rotational speed is pre-stored in the memory device within the control circuit 2. The drive command analysis unit 21 analyzes the duty cycle of the drive command signal Sc and, using the above table or function, determines the target rotational speed corresponding to the analyzed duty cycle and generates specified rotational speed information Stv indicating the target rotational speed.

[0064] The drive command analysis unit 21 provides the specified rotation direction information Str and specified rotation speed information Stv, generated by the method described above, to the signal generation unit 22.

[0065] The rotational speed calculation unit 23 is a functional unit that calculates the actual rotational speed of the motor 40. Based on the rotational position detection signal Sh, the rotational speed calculation unit 23 calculates the actual rotational speed of the motor 40 using a known calculation method and provides the actual rotational speed information Sv, which indicates the actual rotational speed, to the signal generation unit 22. In the case of the sensorless method described above, for example, the rotational speed calculation unit 23 may detect the back electromotive force induced in each phase (U phase, V phase, W phase) of the motor 40 and calculate the actual rotational speed of the motor 40 based on that back electromotive force.

[0066] The signal generation unit 22 generates a drive control signal Sd for the motor 40 based on the specified rotation direction information Str, the specified rotation speed information Stv, and the actual rotation speed information Sv. Specifically, the signal generation unit 22 calculates the error between the specified rotation speed (target rotation speed) and the actual rotation speed of the motor 40, and calculates the control amount for the motor 40 so that the error becomes zero, for example, by PID (Proportional Integral Differential) control calculation. Then, the signal generation unit 22 generates a PWM signal having a duty cycle corresponding to the control amount so that the motor 40 rotates in the specified rotation direction, and outputs it as the drive control signal Sd.

[0067] Furthermore, if the control circuit 2 performs open-loop control, which attempts to rotate the motor 40 with a constant force rather than maintaining its rotational speed, the signal generation unit 22 may generate a drive control signal Sd for the motor 40 based on the specified rotational direction information Str and the specified rotational speed information Stv, without using the actual rotational speed information Sv. For example, the signal generation unit 22 may generate a PWM signal having a duty cycle pre-associated with the specified rotational speed information Stv so that the motor 40 rotates in the rotational direction specified by the specified rotational direction information Str, and output this as the drive control signal Sd.

[0068] Figure 4 is a flowchart showing an example of the processing flow by the motor drive control device 1 according to the embodiment.

[0069] First, the control circuit 2 determines whether the motor 40 is stopped or not (step S11). Specifically, the motor stop determination unit 24 determines whether the motor 40 is stopped or not based on the frequency (period) of the rotation state signal So using the method described above.

[0070] If it is determined that the motor 40 is stopped (step S11: YES), the control circuit 2 monitors for the presence or absence of a drive command signal Sc and starts measuring the duration T (step S12). Specifically, the drive command analysis unit 21 starts measuring the duration T when the motor stop determination unit 24 determines that the motor 40 is stopped.

[0071] Next, the control circuit 2 determines whether or not a PWM signal has been input as the drive command signal Sc (step S13). If no PWM signal has been input (step S13: NO), the drive command analysis unit 21 continues measuring the duration T (step S12). On the other hand, if a PWM signal has been input (step S13: YES), the drive command analysis unit 21 stops measuring the duration T (step S14).

[0072] After the measurement of the duration T is stopped, the control circuit 2 determines whether the duration T is less than the first reference time T1 (step S15). If the duration T is less than the first reference time T1 (step S15: YES), the drive command analysis unit 21 determines that the "first direction (forward direction)" is specified as the rotation direction of the motor 40 and generates specified rotation direction information Str indicating the "first direction (forward direction)" (step S17).

[0073] On the other hand, if the duration T is greater than the first reference time T1 (step S15: NO), the control circuit 2 determines whether the duration T is greater than the first reference time T1 and less than the second reference time T2 (step S16). If the duration T is greater than the first reference time T1 and less than the second reference time T2 (step S16: YES), the drive command analysis unit 21 determines that the "second direction (reverse direction)" is specified as the rotation direction of the motor 40 and generates specified rotation direction information Str indicating the "second direction (reverse direction)" (step S18).

[0074] On the other hand, if the duration T is greater than the second reference time T2 (step S16: NO), the drive command analysis unit 21 determines that the direction of rotation of the motor 40 is the direction in which the motor 40 was rotating immediately before it stopped (step S19). In this case, the specified rotation direction information Str is not updated from the value immediately before the motor 40 stopped.

[0075] If it is determined in step S11 that the motor 40 is not stopped, or after steps S17, S18, and S19, the drive command analysis unit 21 identifies the specified rotational speed by analyzing the duty cycle of the PWM signal as the drive command signal Sc using the method described above, and generates the specified rotational speed information Stv (step S20).

[0076] Next, the signal generation unit 22 generates a drive control signal Sd based on the specified rotation direction information Str generated in step S17, step S18, or step S19 and the specified rotation speed information Stv generated in step S20 (step S21). As a result, the motor 40 rotates in the rotation direction based on the specified rotation direction information Str and at the rotation speed based on the specified rotation speed information Stv.

[0077] Figure 5 shows an example of the relationship between the drive command signal Sc and the operating state of the fan 4 in the fan unit 6 according to the embodiment.

[0078] Figure 5 shows, from top to bottom, the waveform of the DC voltage Vdc, the waveform of the voltage at the signal input terminal P3 (drive command signal Sc), and the state of the rotational speed, respectively.

[0079] As shown in Figure 5, the fan unit 6 starts up when a DC voltage Vdc is input at time t0. At this time, assume that a PWM signal as a drive command signal Sc is input from a higher-level device to the signal input terminal P3.

[0080] For example, after the control circuit 2 is started, the operating mode of the control circuit 2 enters sleep mode. Sleep mode is an operating mode in which the control circuit 2 does not accept input signals from outside and resets the internal registers, etc., of the control circuit 2 to set initial values. For example, in sleep mode, the initial value of the specified rotation direction of the motor 40 is set in the register of the control circuit 2. Here, the initial value may be a value that specifies the forward direction or a value that specifies the reverse direction. In the following explanation, as an example, we will assume that the initial value is a value that specifies the forward direction.

[0081] At time t1, after a predetermined time has elapsed from time t0, the operating mode of the control circuit 2 switches from sleep mode to normal mode. The normal mode is an operating mode in which the motor 40 is driven according to the drive command signal Sc input to the signal input terminal P3.

[0082] When the operating mode transitions from sleep mode to normal mode, the control circuit 2 does not, for example, determine the direction of rotation based on the duration T, but rather generates a drive control signal Sd with the direction of rotation (forward direction) corresponding to the set initial value as the designated direction of rotation. Specifically, the drive command analysis unit 21 generates designated rotation direction information Str indicating the "first direction (forward direction)" and also generates designated rotation speed information Stv indicating the rotation speed corresponding to the duty cycle of the input drive command signal Sc. The signal generation unit 22 generates a drive control signal Sd based on the designated rotation direction information Str and the designated rotation speed information Stv. As a result, at time t1, the motor 40 begins to rotate in the forward direction (forward rotation).

[0083] At time t2, the input of the PWM signal as the drive command signal Sc stops. In response to the cessation of the PWM signal input, the drive command analysis unit 21 updates the specified rotational speed information Stv so that the rotational speed becomes zero, and the signal generation unit 22 stops outputting the drive control signal Sd. As a result, the rotational speed of the motor 40 decreases. At time t3, when the rotational speed falls below the threshold, the motor stop determination unit 24 determines that the motor 40 has stopped. The drive command analysis unit 21, triggered by the determination that the motor 40 has stopped, starts measuring the duration T.

[0084] Subsequently, at time t4, when the PWM signal as the drive command signal Sc is input to the control circuit 2 again, the drive command analysis unit 21 stops measuring the duration T and compares the duration T with the reference times T1 and T2. In the example in Figure 5, since the duration T between time t3 and time t4 is smaller than the reference time T1 (T < T1), the drive command analysis unit 21 determines that the "first direction (forward direction)" is specified as the rotation direction of the motor 40, and generates specified rotation direction information Str indicating the "first direction (forward direction)" and specified rotation speed information Stv indicating the rotation speed according to the duty cycle of the input drive command signal Sc. The signal generation unit 22 generates a drive control signal Sd based on the specified rotation direction information Str and the specified rotation speed information Stv. As a result, at time t4, the motor 40 starts rotating in the forward direction (forward rotation).

[0085] At time t5, the input of the PWM signal as the drive command signal Sc stops. In response to the cessation of the PWM signal input, the drive command analysis unit 21 updates the specified rotational speed information Stv so that the rotational speed becomes zero, and the signal generation unit 22 stops outputting the drive control signal Sd. As a result, the rotational speed of the motor 40 decreases. At time t6, when the rotational speed falls below the threshold, the motor stop determination unit 24 determines that the motor 40 has stopped. The drive command analysis unit 21, triggered by the determination that the motor 40 has stopped, starts measuring the duration T.

[0086] Subsequently, at time t7, when the PWM signal as the drive command signal Sc is input to the control circuit 2 again, the drive command analysis unit 21 stops measuring the duration T and compares the duration T with reference times T1 and T2. In the example in Figure 5, since the duration T between time t6 and time t7 is greater than reference time T1 and less than reference time T2 (T1 < T < T2), the drive command analysis unit 21 determines that the motor 40's rotation direction is set to "second direction (reverse direction)" and generates specified rotation direction information Str indicating "second direction (reverse direction)" and specified rotation speed information Stv indicating the rotation speed corresponding to the duty cycle of the input drive command signal Sc. The signal generation unit 22 generates a drive control signal Sd based on the specified rotation direction information Str and the specified rotation speed information Stv. As a result, from time t7 onward, the motor 40 begins to rotate in the reverse direction (negative rotation).

[0087] At time t8, the input of the PWM signal as the drive command signal Sc stops. In response to the cessation of the PWM signal input, the drive command analysis unit 21 updates the specified rotational speed information Stv so that the rotational speed becomes zero, and the signal generation unit 22 stops outputting the drive control signal Sd. As a result, the rotational speed of the motor 40 decreases. At time t9, when the rotational speed falls below the threshold, the motor stop determination unit 24 determines that the motor 40 has stopped. The drive command analysis unit 21, triggered by the determination that the motor 40 has stopped, starts measuring the duration T.

[0088] Subsequently, at time t10, when the PWM signal as the drive command signal Sc is input to the control circuit 2 again, the drive command analysis unit 21 stops measuring the duration T and compares the duration T with reference times T1 and T2. In the example in Figure 5, since the duration T between time t9 and time t10 is greater than the reference time T2 (T2 < T), the drive command analysis unit 21 determines that the rotation direction of the motor 40 is the rotation direction immediately before the motor 40 stops. In the example in Figure 5, since the rotation direction before time t9 when the motor 40 stops is the "second direction (reverse direction)", the drive command analysis unit 21 determines that the "second direction (reverse direction)" is specified as the rotation direction of the motor 40 and generates specified rotation direction information Str indicating the "second direction (reverse direction)" and specified rotation speed information Stv indicating the rotation speed according to the duty cycle of the input drive command signal Sc. The signal generation unit 22 generates a drive control signal Sd based on the specified rotation direction information Str and the specified rotation speed information Stv. As a result, from time t10 onward, the motor 40 begins to rotate in the reverse direction (negative rotation).

[0089] As described above, according to the motor drive control device 1 of the embodiment, the control circuit 2 monitors the operating state of the motor 40, and after detecting that the motor 40 is stopped, measures the duration T, which is the time during which the drive command signal Sc remains at a first logic level (low level), and determines the rotation direction based on the length of the duration T. With this, as in the conventional technology, it is not necessary to allocate a part of the duty cycle range of the PWM signal as the drive command signal Sc to the specification of the rotation direction of the motor (fan), so it is possible to switch the rotation direction of the motor while ensuring a wide range of motor rotation speed settings.

[0090] Furthermore, in the motor drive control device 1, the control circuit 2 determines that a first direction (e.g., forward direction) is specified as the direction of rotation when the duration T is less than the reference time T1, and determines that a second direction (e.g., reverse direction) opposite to the first direction is specified as the direction of rotation when the duration T is greater than the reference time T1 and less than the reference time T2. This makes it easy to specify the direction of rotation according to the length of the duration T.

[0091] Furthermore, in the motor drive control device 1, the control circuit 2 determines that the rotation direction was specified before detecting that the motor 40 was stopped, if the duration T is greater than the reference time T2. According to this, there is no need to specify the rotation direction again when a change in rotation direction is unnecessary.

[0092] Furthermore, in the motor drive control device 1, the control circuit 2 determines that the motor 40 is not stopped if the frequency of the rotation status signal So is above a threshold, and determines that the motor 40 is stopped if the frequency of the rotation status signal So is below the threshold. This makes it possible to easily detect whether the motor 40 is stopped or not.

[0093] <<Expansion of Embodiments>> The present invention has been described in detail above based on embodiments, but it goes without saying that the present invention is not limited thereto and can be modified in various ways without departing from its essence.

[0094] For example, in the above embodiment, the control circuit 2 is shown as determining that the rotation direction before detecting that the motor 40 was stopped is specified when the duration T is greater than the reference time T2, but it is not limited to this. For example, when the control circuit 2 detects that the duration T is greater than the reference time T2, it may determine that the rotation direction corresponding to the initial value (a value indicating forward direction or a value indicating reverse direction) is specified.

[0095] Furthermore, in the above embodiment, as an example, the drive command analysis unit 21 determines that the first direction (forward direction / positive rotation) is specified as the rotation direction when the duration T is less than the reference time T1, but the invention is not limited to this. For example, when the duration T is less than the reference time T1, the drive command analysis unit 21 may determine that the rotation direction is the opposite to the rotation direction before it detected that the motor 40 was stopped.

[0096] Furthermore, in the above embodiment, when the duration T matches the reference time T1 (T = T1), the drive command analysis unit 21 may determine that the first direction (forward direction) is specified as the designated direction, or it may determine that the second direction (reverse direction) is specified as the designated direction. Also, when the duration T matches the reference time T2 (T = T2), the drive command analysis unit 21 may determine that the second direction (reverse direction) is specified as the designated direction, or it may determine that the rotation direction immediately before stopping is specified as the designated direction. In other words, the processing content when the duration T matches the reference times T1 and T2 can be set appropriately according to, for example, the specifications of the system to which the present invention is applied.

[0097] Furthermore, although the above embodiment illustrates a case where the motor 40 is a three-phase brushless motor, the type and number of phases of the motor 40 are not limited thereto. For example, it may be a single-phase brushless motor.

[0098] Furthermore, the flowchart described above is merely an example illustrating the operation and is not limited to it. In other words, the steps shown in each diagram of the flowchart are specific examples and are not limited to this flow. For example, the order of some processes may be changed, other processes may be inserted between each process, or some processes may be performed in parallel.

[0099] 1...Motor drive control device, 2...Control circuit, 3...Drive circuit, 4...Fan, 5...Position detector, 6...Fan unit, 20...Drive control signal generation unit, 21...Drive command analysis unit, 22...Signal generation unit, 23...Rotation speed calculation unit, 24...Motor stop determination unit, 25...Rotation state signal generation unit, 40...Motor, 41...Impeller, 49-52...Signal lines, Sc...Drive command signal, Sd...Drive control signal, Sh...Rotation position detection signal, Stv...Specified rotation speed information, Str...Specified rotation direction information, So...Rotation state signal, T...Duration, T1...(First) reference time, T2...(Second) reference time.

Claims

1. A motor drive control device comprising: a signal input terminal for inputting a drive command signal that indicates the drive state of a motor; a control circuit that, based on the drive command signal input to the signal input terminal, identifies a specified direction of rotation and generates a drive control signal for controlling the rotation of the motor so that the motor rotates in the identified direction of rotation; and a drive circuit that drives the motor based on the drive control signal, wherein the control circuit monitors the operating state of the motor, detects that the motor has stopped, measures the duration for which the drive command signal remains at a first logic level, and identifies the direction of rotation based on the length of the duration.

2. A motor drive control device according to claim 1, wherein the control circuit determines that a first direction is specified as the rotation direction when the duration is less than a first reference time, and determines that a second direction opposite to the first direction is specified as the rotation direction when the duration is greater than the first reference time and less than a second reference time.

3. A motor drive control device according to claim 2, wherein the control circuit determines that the rotation direction specified before detecting that the motor was stopped is greater than the second reference time when the duration is greater than the second reference time.

4. A motor drive control device according to claim 2, wherein an initial value is set in advance as the specified value for the rotation direction, and the control circuit determines that the rotation direction corresponding to the initial value is specified when the duration is greater than the second reference time.

5. A motor drive control device according to claim 1, wherein the control circuit includes: a rotation state signal generation unit that detects the rotation state of the motor and generates and outputs a rotation state signal having a frequency corresponding to the actual rotation speed of the motor; a drive control signal generation unit that determines whether the motor is rotating based on the rotation state signal and generates the drive control signal, wherein the drive control signal generation unit includes: a motor stop determination unit that determines whether the motor is stopped; a drive command analysis unit that, when it is determined that the motor is stopped, measures the duration, identifies the specified rotation direction based on the duration, generates information on the specified rotation direction, identifies the rotation speed based on the duty cycle of the drive command signal and generates information on the specified rotation speed; and a signal generation unit that generates the drive control signal based on the specified rotation direction information and the specified rotation speed information.

6. A motor drive control device according to claim 5, wherein the motor stop determination unit determines that the motor is not stopped when the frequency of the rotation status signal is equal to or greater than a threshold, and determines that the motor is stopped when the frequency of the rotation status signal is lower than the threshold.

7. A fan unit comprising the motor, an impeller connected to the output shaft of the motor, and a motor drive control device according to any one of claims 1 to 6.

8. A motor drive control method for controlling the rotation of a motor using a motor drive control device, comprising: a first step of generating a drive control signal for controlling the rotation of the motor based on a drive command signal indicating the drive state of the motor; and a second step of driving the motor based on the drive control signal, wherein the first step includes: a third step of monitoring the operating state of the motor and detecting that the motor is stopped; a fourth step of measuring a duration, which is the time for which the state in which the drive command signal is at a first logic level continues after detecting that the motor is stopped; a fifth step of identifying a specified direction of rotation based on the length of the duration; and a sixth step of generating the drive control signal so that the motor rotates in the direction of rotation identified in the fifth step.

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