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

Abstract

A motor drive control device (1) comprises: a signal input terminal (P3) for inputting a drive command signal (Sc) indicating a drive state of a motor (40); a control circuit (2) that, on the basis of the drive command signal (Sc) input to the signal input terminal (P3), generates a drive control signal (Sd) such that the motor (40) rotates in a direction of rotation designated by the drive command signal (Sc); and a drive circuit (3) that drives the motor (40) on the basis of the drive control signal (Sd). The control circuit (2) determines that a first direction is designated as the direction of rotation in a case where a state in which the drive command signal (Sc) is at a first logic level continues for a first time (T1) or longer, and determines that a second direction opposite to the first direction is designated as the direction of rotation in a case where a state in which the drive command signal (Sc) is at a second logic level opposite to the first logic level continues for a second time (T2) or longer.

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 relates to, for example, a motor drive control device that controls the rotation of a motor in a fan unit.

[0002] Fans (fan motors) have been widely known as cooling devices for dissipating heat generated inside electrical equipment and the like to the outside and cooling the inside of the equipment. The fan has a motor and an impeller connected to the motor's output shaft, and generates airflow (wind) by rotating the impeller in response to rotation of the motor's output shaft. The fan, for example, constitutes a single fan unit together with a motor drive control device for controlling the drive of the fan motor.

[0003] In general, in fan units, a motor drive control device drives a motor in response to instructions from a host device, causing the fan (motor) to rotate in one direction at a constant rotational speed. However, if the fan unit is used for a long period of time, dust may accumulate on the impeller, making it difficult for the motor to rotate. Fans used outdoors are particularly prone to attracting dust and sand. Therefore, fan units with a function to rotate the fan in the opposite direction are known, with the aim of removing dust from the fan.

[0004] For example, Patent Document 1 discloses a technology in which a fan rotates in the forward direction when the duty ratio of a PWM signal that specifies the rotation speed is between 5% and 45%, and rotates in the reverse direction when the duty ratio of the PWM signal is between 55% and 95%.

[0005] U.S. Pat. No. 1,006,0438

[0006] However, according to the technology disclosed in Patent Document 1, the rotation direction of the motor (fan) is specified by the range of the duty ratio of the PWM signal, which has the problem that the range of rotation speeds that can be set by the duty ratio of the PWM signal is narrowed.

[0007] The present invention has been made in view of the above-mentioned problems, and has an object to make it possible to switch the rotation direction of a motor while ensuring a wide setting range for the rotation speed of the motor.

[0008] A motor drive control device according to a representative 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 based on the drive command signal input to the signal input terminal so that the motor rotates in the rotation direction specified by the drive command signal; and a drive circuit that drives the motor based on the drive control signal, wherein the control circuit determines that a first direction is specified as the rotation direction when the drive command signal remains at a first logic level for a first time period or longer, and determines that a second direction opposite to the first direction is specified as the rotation direction when the drive command signal remains at a second logic level opposite to the first logic level for a second time period or longer.

[0009] The motor drive control device according to the present invention makes it possible to switch the rotation direction of the motor while ensuring a wide setting range for the rotation speed of the motor.

[0010] 1 is a block diagram showing the configuration of a fan unit according to an embodiment; FIG. 2 is a perspective view showing a schematic view of the appearance of a fan unit according to an embodiment; FIG. 3 is a diagram showing the relationship between the duty ratio of a drive command signal Sc (PWM signal) during forward rotation of a motor and a target rotation speed; FIG. 4 is a diagram showing the relationship between the duty ratio of a drive command signal Sc (PWM signal) during reverse rotation of a motor and a target rotation speed; FIG. 5 is a flowchart showing an example of the flow of processing by a motor drive control device according to an embodiment; and FIG. 6 is a diagram showing an example of the relationship between a drive command signal and an operating state of a fan in a fan unit according to an embodiment.

[0011] 1. Overview of the Embodiments First, an overview of representative embodiments of the invention disclosed in this application will be described. Note that in the following description, as an example, reference numerals in the drawings corresponding to components of the invention are written in parentheses.

[0012] [1] A motor drive control device (1) according to a representative 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 generates a drive control signal (Sd) for controlling the rotation of the motor based on the drive command signal input to the signal input terminal so that the motor rotates in a rotation direction specified by the drive command signal; and a drive circuit (3) that drives the motor based on the drive control signal, wherein the control circuit determines that a first direction (e.g., a forward direction) has been specified as the rotation direction when a state in which the drive command signal is at a first logic level (e.g., a low level) continues for a first time (T1) or more, and determines that a second direction (reverse direction) opposite to the first direction has been specified as the rotation direction when a state in which the drive command signal is at a second logic level (e.g., a high level) opposite to the first logic level continues for a second time (T2) or more.

[0013] [2] In the motor drive control device described in [1] above, when a PWM signal is input as the drive command signal after the first time or more has elapsed since the drive command signal was at the first logic level, the control circuit may generate the drive control signal so that the motor rotates in the first direction at a rotation speed corresponding to a duty ratio of the PWM signal, and when a PWM signal is input as the drive command signal after the second time or more has elapsed since the drive command signal was at the second logic level, the control circuit may generate the drive control signal so that the motor rotates in the second direction at a rotation speed corresponding to a duty ratio of the PWM signal.

[0014] [3] A fan unit (6) according to a representative embodiment of the present invention is characterized by comprising the motor (40), an impeller (41) connected to the output shaft of the motor, and the motor drive control device (1) described in [1] or [2] above.

[0015] [4] A method according to a representative embodiment of the present invention is a motor drive control method for controlling the rotation of a motor (40) using a motor drive control device (1). The method includes a first step (S1 to S8) of generating a drive control signal (Sd) for controlling the rotation of the motor based on a drive command signal (Sc) that indicates a drive state of the motor so that the motor rotates in a rotation direction specified by the drive command signal, and a second step (S9) of driving the motor based on the drive control signal, wherein the first step includes a third step (S1, S2, S4) of determining that a first direction is specified as the rotation direction when the drive command signal remains at a first logic level (e.g., low level) for a first time period (T1) or more, and a fourth step (S1, S3, S5) of determining that a second direction (reverse direction) opposite to the first direction is specified as the rotation direction when the drive command signal remains at a second logic level (e.g., high level) opposite to the first logic level for a second time period (T2) or more.

[0016] [5] In the motor drive control method described in [4] above, the first step is characterized in that it includes a fifth step (S6-S9) of generating the drive control signal so that, when a PWM signal is input as the drive command signal after the third step, the motor rotates in the first direction at a rotation speed corresponding to the duty ratio of the PWM signal, and a sixth step (S6-S9) of generating the drive control signal so that, when a PWM signal is input as the drive command signal after the fourth step, the motor rotates in the second direction at a rotation speed corresponding to the duty ratio of the PWM signal.

[0017] 2. Specific Examples of Embodiments Specific examples of embodiments of the present invention will be described below with reference to the drawings. In the following description, components common to the embodiments will be designated by the same reference numerals, and repeated description will be omitted.

[0018] 1 is a block diagram showing the configuration of a fan unit 6 according to an embodiment of the present invention, and FIG. 2 is a perspective view schematically showing the appearance of the fan unit 6 according to the embodiment of the present invention.

[0019] The fan unit 6 according to the embodiment is a device that generates wind by rotating an impeller (impeller wheel). The fan unit 6 can be used, for example, as a cooling device that exhausts heat generated inside a device to the outside and cools the inside of the device.

[0020] 1, the fan unit 6 includes a fan 4 and a motor drive control device 1. The fan 4 includes a motor 40 and an impeller 41 attached to the 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.

[0021] The motor drive control device 1 is a device for controlling the drive of a motor 40. As shown in Fig. 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 Fig. 1 are only a part of the whole, and the motor drive control device 1 may include other components in addition to those shown in Fig. 1.

[0022] As shown in FIG. 1, the motor drive control device 1 has a plurality of external terminals, such as a power supply terminal P1, a ground terminal P2, a signal input terminal P3 for inputting a signal, and a signal output terminal P4 for outputting a signal.

[0023] 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 supply 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 drawn out of the casing 47 of the fan unit 6 and connected to a host device (not shown) and a power supply device (not shown) provided outside the fan unit 6, thereby electrically connecting the motor drive control device 1 to the power supply device and the host device.

[0024] A DC voltage Vdc is supplied to the power supply terminal P1 from the power supply device via a signal line 49. This supplies the power supply voltage to the control circuit 2 and the drive circuit 3. Note that a regulator may be provided in the motor drive control device 1, and the regulator may generate a new DC voltage from the DC voltage Vdc and supply it as the power supply voltage to the control circuit 2. The ground terminal P2 is connected to the ground potential GND via a signal line 50.

[0025] As will be described later, a drive command signal Sc instructing the drive state of the motor 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 will be 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.

[0026] When the fan unit 6 receives power from a host device, the power supply terminal P1 and the ground terminal P2 may be connected to a power line and a ground line, respectively, within the host device.

[0027] The position detector 5 is a device for detecting the rotational position of the rotating shaft (rotor) of the motor 40. The position detector 5 is, for example, a Hall element. For example, three Hall elements corresponding to the respective phases (U phase, V phase, W phase) of the motor 40 are arranged at approximately equal intervals around the rotor (magnet) of the motor 40. The number of Hall elements is not particularly limited.

[0028] 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 that indicates the rotational position of the motor 40, i.e., a signal that corresponds to the rotational position of the rotor (magnet) of the motor 40.

[0029] The position detector 5 may be any device that has the function of detecting position information of the rotating shaft (rotor) of the motor 40 and outputting it as an electrical signal, and may be, for example, a rotary encoder. Alternatively, without providing the position detector 5, the rotational position of the motor 40 may be detected by a so-called sensorless method in which the control circuit 2 detects back electromotive voltages induced in each phase (U phase, V phase, W phase) of the motor 40 and detects the rotational position of the motor 40 based on the back electromotive voltages.

[0030] The control circuit 2 is a circuit that performs overall control of the motor drive control device 1. The control circuit 2 generates a drive control signal Sd for controlling the rotation of the motor 40. The control circuit 2 is, for example, a program processing device (e.g., various types of computers such as a microcontroller) that has a configuration in which a processor such as a CPU, various storage devices such as RAM and ROM, and peripheral circuits such as a counter (timer), an A / D conversion circuit, a D / A conversion circuit, a clock generation circuit, and an input / output I / F circuit are connected to each other via buses or dedicated lines. Details of the control circuit 2 will be described later.

[0031] 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 from the pre-drive circuit, and energizes the three-phase coils of the motor 40. The rotation direction of the motor 40 can be changed by switching the order in which the three-phase coils are energized. For example, the inverter circuit is configured by a pair of series circuits of two switch elements connected in series between a DC voltage Vdc and a ground potential GND, each pair being arranged for one phase of the coil. In each pair of two switch elements, a terminal of each phase of the motor 40 is connected to the connection point between the switch elements.

[0032] The pre-drive circuit generates an output signal for driving the inverter circuit based on the drive control signal Sd and outputs it to the inverter circuit. The pre-drive circuit generates and outputs drive signals for driving each switch element of the inverter circuit based on the drive control signal Sd, for example.

[0033] The drive signal output from the pre-drive circuit turns on / off each switch element constituting the inverter circuit, thereby supplying power to each phase of the motor 40 and causing the rotor of the motor 40 to rotate.

[0034] In the motor drive control device 1, at least some of the functional parts of the control circuit 2 and the drive circuit 3 may be packaged as a single semiconductor integrated circuit device (IC: Integrated Circuit), or the drive circuit 3 and the control circuit 2 may each be packaged as individual semiconductor integrated circuit devices.

[0035] Next, the control circuit 2 will be described in detail.

[0036] Based on the drive command signal Sc input to the signal input terminal P3, the control circuit 2 generates a drive control signal Sd for controlling the rotation of the motor 40 so that the motor 40 rotates in the rotation direction specified by the drive command signal Sc. Specifically, the control circuit 2 has a function of generating the drive control signal Sd so that the motor 40 is in the rotation state specified by the drive command signal Sc. Furthermore, the control circuit 2 has a function of switching the rotation direction of the motor 40. That is, the control circuit 2 can rotate the motor 40 in a first direction or a second direction opposite to the first direction, depending on the drive command signal Sc.

[0037] 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-mentioned functions. These functional blocks are realized, for example, by the CPU in the control circuit 2 executing various arithmetic processing in accordance with programs stored in memory and controlling 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 dedicated circuits (dedicated hardware logic circuits, etc.).

[0038] 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 a first direction or a second direction opposite to the first direction. In the following description, the first direction may be referred to as the "forward direction," rotation in the forward direction may be referred to as "positive rotation," the second direction may be referred to as the "reverse direction," and rotation in the negative direction may be referred to as "negative rotation." Details of the drive control signal generation unit 20 will be described later.

[0039] The rotation state signal generator 25 is a functional block that generates a rotation state signal So indicating the rotation state of the motor. The rotation state signal generator 25 generates the 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 generator 25 generates the 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.

[0040] Here, the rotation state signal So is, for example, an 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 generating unit 25 generates the FG signal by a known method, for example, based on a Hall signal serving as the rotation position detection signal Sh.

[0041] The rotation state signal generator 25 may output the rotation state signal So by including information indicating the rotation direction of the motor 40. For example, when the motor 40 is rotating forward, the rotation state signal generator 25 may output a signal having a frequency corresponding to the period of the rotation position detection signal Sh and a duty ratio of 50% as the rotation state signal So from the signal output terminal P4. On the other hand, when the motor 40 is rotating backward, the rotation state signal generator 25 may output a signal having a frequency corresponding to the period of the rotation position detection signal Sh and a duty ratio other than 50% as the rotation state signal So from the signal output terminal P4.

[0042] Next, a detailed description will be given of the drive control signal generator 20. The drive control signal generator 20 generates a drive control signal Sd based on the drive command signal Sc.

[0043] Here, the drive command signal Sc is a signal that indicates a 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 a target rotation speed that is a target value for the rotation speed of the motor 40. For example, the drive command signal Sc is a binary signal, and is a signal having a voltage that corresponds to a first logic level or a second logic level that is opposite to the first logic level.

[0044] In this embodiment, as an example, the first logic level is a low level (for example, ground voltage) and the second logic level is a high level (for example, DC voltage Vdc), but this is not limiting.

[0045] The drive control signal generating unit 20 determines that a first direction (forward direction) is specified as the rotation direction of the motor 40 when the drive command signal Sc remains at a first logic level (low level) for a first time T1 or more, and determines that a second direction (reverse direction) is specified as the rotation direction of the motor 40 when the drive command signal Sc remains at a second logic level (high level) opposite to the first logic level for a second time T2 or more.

[0046] Specifically, when a PWM signal is input as the drive command signal Sc after the drive command signal Sc has been at the first logic level (low level) for a first time T1 or more, the drive control signal generation unit 20 generates the drive control signal Sd so that the motor 40 rotates forward at a rotation speed corresponding to the duty ratio of the PWM signal. Also, when a PWM signal is input as the drive command signal Sc after the drive command signal Sc has been at the second logic level (high level) for a second time T2 or more, the drive control signal generation unit 20 generates the drive control signal Sd so that the motor 40 rotates backward at a rotation speed corresponding to the duty ratio of the PWM signal.

[0047] More specifically, the drive control signal generating unit 20 includes, for example, a drive command signal analyzing unit 21 , a signal generating unit 22 , and a rotation speed calculating unit 23 .

[0048] The drive command signal analysis unit 21 analyzes the drive command signal Sc input to the signal input terminal P3 from an external device (host device).

[0049] For example, when the drive command signal Sc remains at the first logic level (low level) for a first time T1 or longer, the drive command signal analysis unit 21 outputs designated rotation direction information Str that specifies the "forward direction" as the rotation direction of the motor 40. On the other hand, when the drive command signal Sc remains at the second logic level (high level) for a second time T2 or longer, the drive command signal analysis unit 21 outputs designated rotation direction information Str that specifies the "reverse direction" as the rotation direction of the motor 40.

[0050] Here, the first time T1 and the second time T2 may be the same value or different values. In this embodiment, the first time T1 and the second time T2 are assumed to be the same value (T1=T2).

[0051] When a PWM signal is input as the drive command signal Sc after the drive command signal Sc has been at the first logic level or the second logic level for at least the first time T1 or the second time T2, the drive control signal generating unit 20 analyzes the duty ratio of the PWM signal and determines the target rotation speed of the motor 40.

[0052] 3A and 3B are diagrams showing the relationship between the duty ratio of the drive command signal Sc (PWM signal) and the target rotation speed.

[0053] Fig. 3A shows the relationship between the duty ratio of the drive command signal Sc and the target rotation speed when the motor 40 rotates in the forward direction. Fig. 3B shows the relationship between the duty ratio of the drive command signal Sc and the target rotation speed when the motor 40 rotates in the forward direction. In Figs. 3A and 3B, the horizontal axis represents the duty ratio of the drive command signal Sc, and the vertical axis represents the target rotation speed.

[0054] 3A and 3B show an example in which the target rotation speed is assigned to each duty ratio within the range of 5% to 95% of the duty ratio of the drive command signal Sc.

[0055] 3A and 3B, information on a table or function that indicates the correspondence relationship between the duty ratio of the drive command signal Sc and the target rotation speed is stored in advance in a storage device within the control circuit 2. The drive control signal generator 20 analyzes the duty ratio of the drive command signal Sc input to the signal input terminal P3, and determines the target rotation speed corresponding to the analyzed duty ratio using the table or function, and outputs the target rotation speed information Stv.

[0056] The drive command signal analysis unit 21 analyzes the drive command signal Sc using the above-described method to generate information Str on the designated rotation direction and information Stv on the target rotation speed, and provides these to the signal generation unit 22 .

[0057] The rotation speed calculation unit 23 is a functional unit that calculates the actual rotation speed of the motor 40. The rotation speed calculation unit 23 calculates the rotation speed of the motor 40 using a known calculation method based on the rotation position detection signal Sh, and provides rotation speed information Sv to the signal generation unit 22. In the case of the sensorless system described above, for example, the rotation speed calculation unit 23 detects a back electromotive force induced in each phase (U phase, V phase, W phase) of the motor 40, and calculates the rotation speed of the motor 40 based on the back electromotive force.

[0058] The signal generating unit 22 generates a drive control signal Sd for the motor 40 based on information Str on the designated rotation direction of the motor 40, information Stv on the target rotation speed of the motor 40, and information Sv on the rotation speed of the motor 40. Specifically, the signal generating unit 22 calculates the error between the target rotation speed and the rotation speed of the motor, calculates the manipulated variable of the motor 40 by, for example, a PID (Proportional Integral Differential) control calculation so that the error becomes zero, generates a PWM signal having a duty ratio according to the manipulated variable so that the motor 40 rotates in the designated rotation direction, and outputs the PWM signal as the drive control signal Sd.

[0059] In the case of open-loop control, which does not attempt to maintain the rotational speed of the motor 40 but instead attempts to rotate it with a constant force, the signal generating unit 22 generates a PWM signal having a duty ratio according to the amount of operation for maintaining the predetermined rotational speed, and outputs it as the drive control signal Sd.

[0060] FIG. 4 is a flowchart showing an example of the flow of processing by the motor drive control device 1 according to the embodiment.

[0061] For example, the control circuit 2 is activated when a DC voltage Vdc is applied to the fan unit 6. First, the control circuit 2 determines the signal level of the drive command signal Sc input to the signal input terminal P3. Specifically, the control circuit 2 determines whether the drive command signal Sc is at a first logic level (low level) (step S1).

[0062] If the drive command signal Sc is at the first logic level (step S1: YES), the control circuit 2 determines whether the state in which the drive command signal Sc is at the first logic level has continued for a first time T1 or more (step S2).If the state in which the drive command signal Sc is at the first logic level has not continued for the first time T1 or more (step S2: NO), the control circuit 2 returns to step S1.

[0063] If the drive command signal Sc remains at the first logic level for a first time T1 or longer (step S2: YES), the control circuit 2 (drive control signal generating unit 20) determines that the "forward direction" is specified as the rotation direction of the motor 40 (step S4).

[0064] On the other hand, if the drive command signal Sc is at the second logic level (high level) (step S1: NO), the control circuit 2 determines whether the state in which the drive command signal Sc is at the second logic level has continued for at least the second time T2 (step S3). If the state in which the drive command signal Sc is at the second logic level has not continued for at least the second time T2 (step S3: NO), the control circuit 2 returns to step S1. If the state in which the drive command signal Sc is at the second logic level has continued for at least the second time T2 (step S3: YES), the control circuit 2 (drive control signal generator 20) determines that the "reverse direction" is specified as the rotation direction of the motor 40 (step S5).

[0065] After determining the designated rotation direction of the motor 40 in step S4 or step S5, the control circuit 2 determines whether a PWM signal has been input as the drive command signal Sc (step S6). If a PWM signal has not been input as the drive command signal Sc (step S6: NO), the control circuit 2 returns to step S1. If a PWM signal has been input as the drive command signal Sc (step S6: YES), the drive control signal generator 20 of the control circuit 2 sets the rotation speed corresponding to the duty ratio of the drive command signal Sc as the target rotation speed using the method described above (step S7).

[0066] The control circuit 2 generates a drive control signal Sd so that the motor 40 rotates in the direction (forward or reverse) specified in step S4 or step S5 at the target rotation speed set in step S7 (step S8). The drive circuit 3 then drives the motor 40 based on the drive control signal Sd, causing the motor 40 to rotate (step S9).

[0067] FIG. 5 is a diagram showing 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.

[0068] 5, reference numeral 301 indicates a change over time in the drive command signal Sc, and reference numeral 302 indicates a change over time in the operating state of the fan 4 (motor 40). Here, as an example, it is assumed that when the duty ratio of the drive command signal Sc is 50%, the target rotation speed is set to 5000 rpm, and when the duty ratio of the drive command signal Sc is 90%, the target rotation speed is set to 9500 rpm.

[0069] 5, for example, when the control circuit 2 is started at time t0, a drive command signal Sc of the first logic level (low level) is input to the control circuit 2. At this time, the control circuit 2 generates a drive control signal Sd to stop the rotation of the motor 40.

[0070] At time t1, when a first time T1 has elapsed since time t0, the control circuit 2 determines that the "forward direction (positive rotation)" has been specified as the rotation direction of the motor 40. Thereafter, at time t2, when a PWM signal with a duty ratio of 50% is input as the drive command signal Sc, the control circuit 2 sets the target rotation speed to 5000 rpm using the method described above, and generates the drive control signal Sd so that the motor 40 rotates in the positive direction at a rotation speed of 5000 rpm.

[0071] At time t3 when the duty ratio of the drive command signal Sc is changed from 50% to 90%, the control circuit 2 changes the target rotation speed from 5000 rpm to 9500 rpm and generates a drive control signal Sd so that the motor 40 rotates forward at a rotation speed of 9500 rpm.

[0072] Thereafter, at time t4 when the drive command signal Sc is fixed at the second logic level (high level), the control circuit 2 generates a drive control signal Sd to stop the rotation of the motor 40. At time t5, when a second time T2 has elapsed since time t4, the control circuit 2 determines that the "reverse direction (negative rotation)" has been specified as the rotation direction of the motor 40. Thereafter, at time t6 when a PWM signal with a duty ratio of 90% is input as the drive command signal Sc, the control circuit 2 sets the target rotation speed to 9500 rpm using the method described above, and generates a drive control signal Sd to rotate the motor 40 in the negative direction at a rotation speed of 9500 rpm.

[0073] At time t7 when the duty ratio of the drive command signal Sc is changed from 90% to 50%, the control circuit 2 changes the target rotation speed from 9500 rpm to 5000 rpm and generates a drive control signal Sd so that the motor 40 rotates in the negative direction at a rotation speed of 5000 rpm.

[0074] Thereafter, at time t8 when the drive command signal Sc is fixed at the second logic level (high level), the control circuit 2 generates a drive control signal Sd to stop the rotation of the motor 40. Then, at time t9 when the first time T1 has elapsed since time t8, the control circuit 2 again determines that the "forward direction (positive rotation)" has been specified as the rotation direction of the motor 40, and waits for the input of a PWM signal as the drive command signal Sc.

[0075] As described above, according to the motor drive control device 1 of the embodiment, when the drive command signal Sc remains at the first logic level for a first time period T1 or longer, the control circuit 2 generates the drive control signal Sd so that the motor 40 rotates in a first direction. On the other hand, when the drive command signal Sc remains at the second logic level for a second time period T2 or longer, the control circuit 2 generates the drive control signal Sd so that the motor 40 rotates in a second direction. This allows the rotation direction of the motor 40 to be specified based on the logic level of the drive command signal Sc and the duration of that logic level. Therefore, the target rotation speed of the motor 40 can be assigned to various signal patterns that the drive command signal Sc can assume. This makes it possible to switch the rotation direction of the motor 40 while ensuring a wide setting range for the rotation speed of the motor 40.

[0076] Furthermore, in the motor drive control device 1 according to the embodiment, when a PWM signal is input as the drive command signal Sc after the drive command signal Sc has been at the first logic level for a first time T1 or more, the control circuit 2 generates the drive control signal Sd so that the motor 40 rotates in the first direction at a rotation speed corresponding to the duty ratio of the PWM signal. On the other hand, when a PWM signal is input as the drive command signal Sc after the drive command signal Sc has been at the second logic level for a second time T2 or more, the control circuit 2 generates the drive control signal Sd so that the motor 40 rotates in the second direction at a rotation speed corresponding to the duty ratio of the PWM signal. This eliminates the need to use a specific duty ratio of the PWM signal to specify the rotation direction of the motor 40, even when a PWM signal is used as the drive command signal Sc that specifies the target rotation speed of the motor 40. This ensures a wide setting range of duty ratios to which the target rotation speed can be assigned.

[0077] <<Extending the Embodiments>> The invention made by the present inventor has been specifically described above based on the embodiments, but it goes without saying that the present invention is not limited thereto and can be modified in various ways without departing from the spirit of the invention.

[0078] For example, in the above embodiment, the control circuit 2 may determine that the drive command signal Sc is at a first logical level (low level) when the duty ratio of the PWM signal serving as the drive command signal Sc is a first value (e.g., 5%) or less, and may determine that the drive command signal Sc is at a second logical level (high level) when the duty ratio of the PWM signal serving as the drive command signal Sc is a second value (e.g., 95%) or more.

[0079] Although the control circuit 2 returns to step S1 if a PWM signal is not input as the drive command signal Sc in step S6 of FIG. 4 , this is not limiting. For example, if a PWM signal is not input as the drive command signal Sc in step S6, the control circuit 2 may wait, without returning to step S1, while retaining information about the specified rotation direction until a PWM signal is input. Alternatively, a waiting time may be provided during which the control circuit 2 waits for input of a PWM signal while retaining information about the specified rotation direction. For example, if a PWM signal is input as the drive command signal Sc within the waiting time, the control circuit 2 may proceed to step S7. If a PWM signal is not input as the drive command signal Sc by the time the waiting time has elapsed, the control circuit 2 may return to step S1.

[0080] In addition, in the above embodiment, the motor 40 is a three-phase brushless motor, but the type and number of phases of the motor 40 are not limited to this. For example, the motor 40 may be a single-phase brushless motor.

[0081] Furthermore, the above-described flowcharts are merely examples for explaining the operation, and are not intended to be limiting. That is, the steps shown in each diagram of the flowchart are specific examples, and the present invention is not limited to these flows. For example, the order of some processes may be changed, other processes may be inserted between processes, or some processes may be performed in parallel.

[0082] 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 signal analysis unit, 22...signal generation unit, 23...rotational speed calculation unit, 25...rotational state signal generation unit, 40...motor, 41...impeller, 49-52...signal lines, Sc...drive command signal, Sd...drive control signal, Stv...target rotational speed information, Str...specified rotation direction information, Sv...rotational speed information, Sh...rotational position detection signal

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 generates a drive control signal for controlling the rotation of the motor so that the motor rotates in the rotation direction specified by the drive command signal 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, wherein the control circuit determines that a first direction has been specified as the rotation direction when the drive command signal remains at a first logic level for a first time period or longer, and determines that a second direction opposite to the first direction has been specified as the rotation direction when the drive command signal remains at a second logic level opposite to the first logic level for a second time period or longer.

2. A motor drive control device as claimed in claim 1, wherein the control circuit generates the drive control signal so that the motor rotates in the first direction at a rotation speed corresponding to the duty ratio of the PWM signal when a PWM signal is input as the drive command signal after the first time or more has elapsed while the drive command signal is at the first logical level, and generates the drive control signal so that the motor rotates in the second direction at a rotation speed corresponding to the duty ratio of the PWM signal when the PWM signal is input as the drive command signal after the second time or more has elapsed while the drive command signal is at the second logical level.

3. A fan unit comprising: the motor; an impeller connected to the output shaft of the motor; and the motor drive control device according to claim 1 or 2.

4. 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 that indicates the drive state of the motor, so that the motor rotates in a rotation direction specified by the drive command signal; and a second step of driving the motor based on the drive control signal, wherein the first step comprises: a third step of determining that a first direction has been specified as the rotation direction when a state in which the drive command signal is at a first logical level continues for a first time period or longer; and a fourth step of determining that a second direction opposite to the first direction has been specified as the rotation direction when a state in which the drive command signal is at a second logical level opposite to the first logical level continues for a second time period or longer.

5. A motor drive control method as claimed in claim 4, wherein the first step further comprises: a fifth step of generating the drive control signal when a PWM signal is input as the drive command signal after the third step, so that the motor rotates in the first direction at a rotation speed corresponding to the duty ratio of the PWM signal; and a sixth step of generating the drive control signal when a PWM signal is input as the drive command signal after the fourth step, so that the motor rotates in the second direction at a rotation speed corresponding to the duty ratio of the PWM signal.

Images