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

Abstract

To satisfy desired air volume-static pressure characteristics without excessively restricting a drive current while satisfying restrictions of a power supply capacity.SOLUTION: A motor drive control device includes: a control circuit section 4 for generating a drive control signal Sd for controlling actual rotation speed of a motor based on a speed command signal indicating target rotation speed of a motor 100; and a motor drive section 90 for driving the motor 100 based on the drive control signal Sd. The control circuit section 4 includes a power control section 60 that can select either a speed feedback control mode for generating the drive control signal Sd so that actual rotation speed of the motor 100 coincides with the target rotation speed, or a current feedback control mode for generating the drive control signal Sd so that a drive current of the motor 100 coincides with a target current. The power control section 60 sets a current threshold according to a power supply voltage Vdd supplied from outside as the target current, and when detecting that the drive current is equal to or larger than the current threshold, switches from the speed feedback control mode to the current feedback control mode.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a motor drive control device, a motor unit, and a motor drive control method. [Background technology]

[0002] Fans (fan motors) have been widely used in home appliances, office automation equipment, etc. as devices for cooling components installed inside these appliances. Generally, the performance of a fan is expressed by its airflow-static pressure characteristics (hereinafter also referred to as "PQ characteristics").

[0003] The PQ characteristic expresses the relationship between the pressure loss (static pressure) between the fan's intake and exhaust ports and the air volume. In the PQ characteristic, when the static pressure is at its maximum (maximum ventilation resistance), the fan's air volume is zero, and when the static pressure is zero (zero ventilation resistance), the fan's air volume is maximum. The state when the static pressure is zero, i.e., when the fan's air volume is maximum, is also called the "free air state."

[0004] Nowadays, when it comes to fan motors, there are power supply capacity constraints. For example, if the current limit value of a host device driving 10 motors in a server system is 30A, the current limit value of each motor must be set to 3A.

[0005] Under these circumstances, fan motors may be required to limit their current in airflow ranges other than the operating point in the PQ characteristics (the operating range determined by the airflow and static pressure required by the customer) due to customer requirements or specifications.

[0006] When using conventional speed feedback control to maintain a constant actual rotation speed of a fan motor, it becomes necessary to increase the motor's drive current at points where the static pressure in the PQ characteristics is high, compared to the operation point and the free air region (the region where the fan's air volume is at its maximum).If the motor's drive current is increased without any limits, there is a risk of damaging the motor or its drive circuit, so some kind of countermeasure is necessary.

[0007] Conventionally, for example, Patent Document 1 proposes a motor control device that limits current by detecting an overcurrent with an overcurrent detection circuit that uses an algorithm for overcurrent protection. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-158443 Summary of the Invention [Problem to be solved by the invention]

[0009] However, in the motor control device of Patent Document 1, the peak value of the current is used as a general overcurrent protection algorithm to determine whether or not there is an overcurrent, and therefore the peak value varies greatly depending on the degree of advance angle and individual differences, and the current limit value (current threshold) used to determine whether or not there is an overcurrent must be set in advance to a value smaller than the user's request.

[0010] In such a case, the drive current of the motor may be restricted too much, and the drive current may be restricted even at the operation point, which may result in the desired PQ characteristics not being achieved.

[0011] The present invention is intended to solve the above-mentioned problems, and aims to provide a motor drive control device, a motor unit, and a motor drive control method that can satisfy the desired air volume-static pressure characteristics without excessively limiting the motor drive current while satisfying the constraints of the power supply capacity. [Means for solving the problem]

[0012] A motor drive control device according to a representative embodiment of the present invention comprises a control circuit unit that generates a drive control signal for controlling the actual rotation speed of the motor based on a speed command signal that indicates a target rotation speed of the motor, and a motor drive unit that drives the motor based on the drive control signal, wherein the control circuit unit has a power control unit that can select either a speed feedback control mode in which the drive control signal is generated so that the actual rotation speed of the motor matches the target rotation speed, or a current feedback control mode in which the drive control signal is generated so that the drive current of the motor matches the target current, and the power control unit sets a current threshold corresponding to an externally supplied power supply voltage as the target current, and switches from the speed feedback control mode to the current feedback control mode when it detects that the drive current has become equal to or greater than the current threshold.

[0013] According to one aspect of the present invention, it is possible to realize a motor drive control device, a motor unit, and a motor drive control method that can satisfy the desired air volume-static pressure characteristics while satisfying the constraints of the power supply capacity and without excessively restricting the motor drive current. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a diagram illustrating an example of a configuration of a fan system according to an embodiment of the present invention. [Figure 2] 5 is a flowchart showing an example of the flow of a motor drive control process based on the operation of a power control unit in the motor drive control device of the fan system according to the present embodiment. [Figure 3]1A is a diagram showing an example of a change in drive current due to speed feedback control using conventional overcurrent protection, and FIG. 1B is a diagram showing an example of a change in drive current due to power control according to the present embodiment. [Figure 4] FIG. 1 is a diagram illustrating an example of limiting a drive current value by conventional overcurrent protection. [Figure 5] FIG. 10 is a diagram showing an example of limiting the drive current value in the current feedback control mode according to the present embodiment. [Figure 6] FIG. 10 is a diagram showing a comparative example of changes in the actual rotation speed of the motor relative to the air volume in the conventional speed feedback control and the power control according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] <Embodiments of the present invention> DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, components common to the embodiments will be designated by the same reference numerals, and repeated description will be omitted.

[0016] Fig. 1 is a diagram showing an example of the configuration of a fan system 1 according to an embodiment of the present invention. The fan system 1 shown in Fig. 1 includes a higher-level device 2 and a motor unit 10. A motor drive control device 3 of the motor unit 10 is a device for controlling the drive of a motor 100 as a driven object.

[0017] The motor 100 is, for example, a three-phase brushless motor. The type of motor 100 is not particularly limited, and the number of phases is not limited to three. An impeller (not shown), for example, is connected to the output shaft of the motor 100. The impeller (not shown) is a component that generates wind and is configured to be rotatable by the torque of the motor 100. For example, the rotation shaft of the impeller is coaxially connected to the output shaft of the motor 100.

[0018] In the embodiment of the present invention, for example, the impeller and the motor 100 constitute one fan (fan motor). The motor 100 and the motor drive control device 3 constitute one motor unit .

[0019] In this case, the motor unit 10 is assumed to be placed in a closed space within a server, for example, and to constitute a cooling system that cools various electronic components that make up the server using an impeller (not shown) connected to the motor 100. The motor unit 10 (motor drive control device 3 and motor 100) operates based on various commands from the higher-level device 2.

[0020] The motor drive control device 3 rotates the motor 100 by periodically passing a drive current through the three-phase coils that make up the motor 100. The motor drive control device 3 has a control circuit unit 4, a current detector 70, and a motor drive unit 90. Note that the components of the motor drive control device 3 shown in FIG. 1 are only a part of the whole. The motor drive control device 3 may have other components in addition to those shown in FIG. 1.

[0021] The motor drive unit 90 outputs a drive signal generated based on the drive control signal Sd output from the control circuit unit 4 of the motor drive control device 3 to the motor 100, thereby driving the motor 100. The motor drive unit 90 selectively energizes the three-phase coils of the motor 100.

[0022] Specifically, the motor drive unit 90 has an inverter circuit 91 and a pre-drive circuit (not shown). The pre-drive circuit generates an output signal for driving the inverter circuit 91 based on a drive control signal Sd output from the control circuit unit 4, and outputs the output signal to the inverter circuit 91. The inverter circuit 91 generates and outputs a drive signal based on the output signal from the pre-drive circuit, and energizes three-phase coils provided in the motor 100.

[0023] The current detector 70 is a functional unit for detecting the drive current flowing through the motor 100, i.e., the drive current flowing through each coil of the motor 100. The current detector 70 outputs a voltage Vm corresponding to the drive current of the motor 100 to the control circuit unit 4.

[0024] The current detector 70 includes a resistor (not shown) connected in series between each coil of the motor 100 and ground potential via the motor drive unit 90, and outputs the voltage Vm generated across the resistor as a drive current (detection current) flowing through each coil of the motor 100.

[0025] The host device 2 is a control device that controls the motor drive control device 3. For example, if the motor unit 10 (the motor drive control device 3 and the motor 100) constitutes a cooling system for a server, the host device 2 is a program processing device that realizes the main functions of the server.

[0026] For example, the upper device 2 is realized by accommodating in a single housing together with the motor unit 10 a program processing device (e.g., a microcontroller) having a configuration in which a processor such as a CPU (Central Processing Unit), various storage devices such as RAM (Random Access Memory) and ROM (Read Only Memory), and peripheral circuits such as a counter (timer), an A / D (Analog-Digital) conversion circuit, a D / A (Digital-Analog) conversion circuit, a clock generation circuit, and an input / output I / F (Interface) circuit are interconnected via a bus or dedicated lines.

[0027] The higher-level device 2 controls the rotation of the motor 100 so that the air volume of the impeller (not shown) is appropriate in response to environmental changes (such as changes in processing load and temperature inside the server).

[0028] As shown in FIG. 1, the upper device 2 has a speed command section 21 that transmits a speed command signal Sc indicating the target rotation speed Rtg of the motor 100 (hereinafter referred to as the "target rotation speed") to the motor drive control device 3 of the motor unit 10, and a power supply section 22 that supplies a power supply voltage Vdd to drive the control circuit section 4.

[0029] The speed command unit 21 is realized, for example, by a processor in a program processing device constituting the higher-level device 2, which executes various arithmetic processing in accordance with programs stored in memory and controls peripheral circuits such as counters and A / D conversion circuits.

[0030] The speed command unit 21 monitors the rotation state of the motor 100 controlled by the motor drive control device 3 by receiving, via a communication unit (not shown), a rotation speed signal So (e.g., an FG (Frequency Generator) signal) that indicates the actual rotation speed Rmv of the motor 100 (hereinafter referred to as the "actual rotation speed") output from the control circuit unit 4 of the motor drive control device 3. The transmission and reception of the rotation speed signal So may be achieved, for example, by using a dedicated line connecting the higher-level device 2 and the motor drive control device 3, or by serial communication.

[0031] The motor drive control device 3 has, as its main functions, a motor drive control function for controlling the rotation of the motor 100, a communication function for communicating with the higher-level device 2, and a monitoring function for monitoring the operating state of the motor 100.

[0032] Specifically, as a motor drive control function, the motor drive control device 3 generates a drive control signal Sd using the drive control signal generation unit 40 of the control circuit unit 4 in response to the speed command signal Sc from the higher-level device 2, and outputs this drive control signal Sd to the motor 100 via the motor drive unit 90.

[0033] As a result, the motor drive control device 3 outputs a drive signal corresponding to the drive control signal Sd to the motor 100 via the motor drive unit 90, and periodically passes a drive current through the coils of each phase of the motor 100 to rotate the motor 100.

[0034] As a communication function, the motor drive control device 3 receives various commands (speed command signal Sc, etc.) from the upper device 2 by sending and receiving data with the upper device 2, and also sends responses to the received commands to the upper device 2.

[0035] As a monitoring function, the motor drive control device 3 monitors the operating state of the motor 100 by measuring physical quantities related to the operation of the motor 100 to be driven, and based on the measurement results, controls the fan driven by the motor 100 so that it satisfies the desired air volume-static pressure characteristics (PQ characteristics).

[0036] Here, physical quantities related to the operating state of the motor 100 include, for example, the drive current (coil current) of the motor 100, the actual rotation speed, the drive voltage (coil voltage), the ambient temperature, etc. In this embodiment, the drive current (coil current) of the motor 100 and the actual rotation speed Rmv of the motor 100 are primarily used.

[0037] The motor drive control device 3 has a control circuit 4 as a functional unit for realizing the above-mentioned functions. The control circuit 4 has, for example, a drive control signal generation unit 40, a power control unit 60, a rotation speed monitoring unit 51, an FG signal generation unit 52, a current monitoring unit 53, a power supply voltage monitoring unit 54, etc.

[0038] Of these functional units of the control circuit unit 4, the drive control signal generation unit 40, the power control unit 60, the rotation speed monitoring unit 51, the FG signal generation unit 52, the current monitoring unit 53, and the power supply voltage monitoring unit 54 are realized, for example, by a program processing device. Specifically, in a program processing device (for example, a microcontroller) having 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 one another via a bus or dedicated lines, the CPU executes various arithmetic processing in accordance with programs stored in the memory, and controls the peripheral circuits such as the A / D conversion circuit and the input / output interface circuit based on the processing results, thereby realizing the above-mentioned functional blocks.

[0039] The motor drive control device 3 may be configured such that the control circuit unit 4, the motor drive unit 90, and at least some of the other functional units are packaged as a single integrated circuit device (IC), or such that the control circuit unit 4, the motor drive unit 90, and the other functional units are each packaged as individual integrated circuit devices.

[0040] Hereinafter, each of the functional units that make up the control circuit unit 4 of the motor drive control device 3 will be described in detail.

[0041] The drive control signal generating unit 40 is a functional unit for generating a drive control signal Sd for controlling the driving of the motor 100. For example, when the drive control signal generating unit 40 receives a speed command signal Sc output from the higher-level device 2, the drive control signal generating unit 40 generates the drive control signal Sd so that the actual rotation speed Rmv of the motor 100 matches the target rotation speed Rtg specified by the speed command signal Sc. Here, the drive control signal Sd is, for example, a PWM (Pulse Width Modulation) signal.

[0042] The drive control signal generating unit 40 includes a speed command analyzing unit 41, a duty ratio determining unit 42, and an energization control unit 43.

[0043] The speed command analysis unit 41 receives the speed command signal Sc output from the speed command unit 21 of the higher-level device 2, and analyzes the target rotation speed Rtg specified by the speed command signal Sc. For example, when the speed command signal Sc is a PWM signal having a duty ratio corresponding to the target rotation speed Rtg, the speed command analysis unit 41 analyzes the duty ratio of the speed command signal Sc, and outputs information on the rotation speed corresponding to the duty ratio as target rotation speed information S1.

[0044] The duty ratio determination unit 42 determines the duty ratio of the PWM signal serving as the drive control signal Sd based on the target rotation speed information S1 output from the speed command analysis unit 41 and the current feedback instruction information S5 or the speed feedback instruction information S6 supplied from the power control unit 60 described later, and outputs the duty ratio information S2 to the current control unit 43.

[0045] The energization control unit 43 generates a PWM signal according to the duty ratio information S2 determined by the duty ratio determination unit 42, and outputs this PWM signal to the motor drive unit 90 as a drive control signal Sd.

[0046] The motor drive unit 90 drives the motor 100 based on the drive control signal Sd generated by the drive control signal generation unit 40. The inverter circuit 91 of the motor drive unit 90 outputs a drive signal to the motor 100 based on the output signal output from the above-mentioned pre-drive circuit, and energizes the coil of the motor 100.

[0047] The rotation speed monitoring unit 51 is a functional unit that measures the actual rotation speed Rmv of the motor 100. For example, the rotation speed monitoring unit 51 measures the actual rotation speed Rmv of the motor 100 based on a position detection signal Sh of a Hall element serving as a position detector 101 disposed near the motor 100, and outputs the measurement result as rotation speed information Sr of the motor 100 to the operation command unit 61 of the power control unit 60. Here, the position detection signal Sh is a Hall signal output from the Hall element serving as the position detector 101, and is a signal that indicates the rotational position of the motor 100, i.e., a signal that corresponds to the rotation of the motor 100.

[0048] The FG signal generating unit 52 generates an FG signal as a rotation speed signal So that indicates the actual rotation speed Rmv of the motor 100. The FG signal generating unit 52 generates a signal (FG signal) having a period (frequency) proportional to the actual rotation speed Rmv of the motor 100, based on the position detection signal (Hall signal) Sh output from the position detector 101 (Hall element).

[0049] The FG signal output from the FG signal generating unit 52 is input to the higher-level device 2 as a rotation speed signal So.

[0050] The current monitoring unit 53 receives the voltage Vm detected by the current detector 70 as the detected current, calculates the actual measured value of the drive current flowing through the motor 100 based on the voltage Vm (hereinafter simply referred to as the "actual measured current value"), and outputs the actual measured current value to the operation command unit 61 of the power control unit 60 as drive current information Si.

[0051] Specifically, the current monitoring unit 53 obtains the smoothed current of the motor 100 by smoothing the voltage Vm detected by the current detector 70. Furthermore, the current monitoring unit 53 includes a ΔΣ ADC (a ΔΣ modulation type analog-to-digital conversion circuit) that performs AD conversion on the detected current or the smoothed current. For example, the current monitoring unit 53 converts the detected current based on the voltage Vm (analog signal) input from the current detector 70 into a digital signal using ΔΣ modulation, thereby calculating an actual current value, which is the average value of the detected current integrated over time. The current monitoring unit 53 outputs the calculated actual current value to the operation command unit 61 of the power control unit 60 as drive current information Si. Note that in the case of a ΔΣ ADC, it is sufficient to convert either the detected current or the smoothed current; however, if a SAR (successive approximation register) ADC is used, for example, the smoothed current is converted.

[0052] The power supply voltage monitoring unit 54 monitors the voltage value of the power supply voltage Vdd supplied from the power supply unit 22 of the higher-level device 2 to the motor drive control device 3, and outputs the voltage value to the operation command unit 61 of the power control unit 60 as power supply voltage information Sv.

[0053] The power control unit 60 includes an operation command unit 61 , a current feedback unit 62 , and a speed feedback unit 63 .

[0054] The operation command unit 61 is a functional unit that receives as input the target rotation speed information S1 from the speed command analysis unit 41, the rotation speed information Sr from the rotation speed monitoring unit 51, the drive current information Si from the current monitoring unit 53, and the power supply voltage information Sv from the power supply voltage monitoring unit 54, and determines, based on this information, whether to control the motor 100 in a speed feedback control mode (hereinafter also referred to as the "speed FB control mode") or in a current feedback control mode (hereinafter also referred to as the "current FB control mode").

[0055] Here, the speed feedback control mode is a mode in which a drive control signal Sd is generated so that the actual rotation speed Rmv of the motor 100 matches the target rotation speed Rtg. On the other hand, the current feedback control mode is a mode in which a drive control signal Sd is generated so that the drive current of the motor 100 matches the target current. Specifically, this is a mode in which the motor 100 is driven so that the actual current measurement value (drive current information Si) of the motor 100 matches the current threshold value Sth (e.g., 5.0 (A)) which is the target current.

[0056] The operation command unit 61 constantly monitors the drive current information Si from the current monitoring unit 53, and determines whether the actual measured current value of the motor 100 is less than a predetermined current threshold Sth or greater than or equal to the current threshold Sth based on the drive current information Si. Here, the current threshold Sth is a threshold that the operation command unit 61 sets in accordance with the voltage value of the power supply voltage Vdd indicated by the power supply voltage information Sv from the power supply voltage monitoring unit 54. In other words, the operation command unit 61 changes the current threshold Sth in accordance with the value of the power supply voltage Vdd so that the power of the motor 100 becomes a desired value.

[0057] For example, when there is a constraint that the motor 100 must be driven with a power of 60 W, if the voltage value of the power supply voltage Vdd is 12 V, the operation command unit 61 sets the current threshold Sth to 5.0 (A), and if the voltage value of the power supply voltage Vdd is 10 V, the operation command unit 61 sets the current threshold Sth to 6.0 (A). That is, the current feedback control mode can also be referred to as the power feedback control mode. Hereinafter, as a specific example, the case where the current threshold Sth is 5.0 (A) will be described.

[0058] The operation command unit 61 compares the drive current information Si (measured current value) from the current monitoring unit 53 with the current threshold Sth. If the drive current information Si (measured current value) is less than the current threshold Sth (Si < Sth), the operation command unit 61 generates operation command information S4 for driving and controlling the motor 100 in the speed feedback control mode, and outputs the operation command information S4 to the speed feedback unit 63.

[0059] Specifically, the operation command unit 61 compares the target rotation speed Rtg calculated based on the target rotation speed information S1 input from the speed command analysis unit 41 with the actual rotation speed Rmv of the motor 100 calculated based on the rotation speed information Sr input from the rotation speed monitoring unit 51, and outputs operation command information S4 that instructs the actual rotation speed Rmv of the motor 100 to match the target rotation speed Rtg to the speed feedback unit 63.

[0060] On the other hand, the operation command unit 61 compares the drive current information Si (measured current value) with the current threshold Sth. As a result, if the drive current information Si (measured current value) is greater than or equal to the current threshold Sth (Si ≥ Sth), the operation command unit 61 generates operation command information S3 for driving and controlling the motor 100 in the current feedback control mode, and outputs the operation command information S3 to the current feedback unit 62.

[0061] When the speed feedback unit 63 receives the operation command information S4 from the operation command unit 61, the speed feedback unit 63 generates speed feedback instruction information S6 based on the operation command information S4, and outputs the speed feedback instruction information S6 to the duty ratio determination unit 42 of the drive control signal generation unit 40.

[0062] On the other hand, when the current feedback unit 62 receives the operation command information S3 from the operation command unit 61, it generates current feedback instruction information S5 based on the operation command information S3 and outputs this current feedback instruction information S5 to the duty ratio determination unit 42 of the drive control signal generation unit 40.

[0063] Here, the operation command unit 61 outputs either operation command information S3 or operation command information S4 based on the comparison result between the drive current information Si (actual current measurement value) and the current threshold value Sth, so that the power control unit 60 outputs only either current feedback instruction information S5 or speed feedback instruction information S6 to the duty ratio determination unit 42.

[0064] The operation command unit 61 outputs operation command information S3 for executing the current feedback control mode or operation command information S4 for executing the speed feedback control mode over the entire air volume range determined by the PQ characteristics. Here, the entire air volume range determined by the PQ characteristics is the range from the minimum air volume (maximum pressure) to the maximum air volume (minimum pressure).

[0065] As described above, the power control unit 60 can select either a speed feedback control mode in which a drive control signal Sd is generated so that the actual rotation speed Rmv of the motor 100 matches the target rotation speed Rtg, or a current feedback control mode in which a drive control signal Sd is generated so that the actual current measurement value, which is the drive current of the motor 100, matches the target current.

[0066] The power control unit 60 sets a current threshold value Sth, which is set according to the power supply voltage Vdd supplied from the outside (in this embodiment, the upper device 2), as the target current, and when it detects that the drive current (actual current measurement value) has become equal to or greater than the current threshold value Sth, it switches from the speed feedback control mode to the current feedback control mode.

[0067] In the present invention, the power control unit 60 controls the drive current of the motor 100 based on the current threshold value Sth set in accordance with the voltage value of the power supply voltage Vdd indicated by the power supply voltage information Sv from the power supply voltage monitoring unit 54, and therefore the control by the power control unit 60 is collectively referred to as "power control."

[0068] The duty ratio determination unit 42 determines the duty ratio of the PWM signal as the drive control signal Sd based on the target rotation speed information S1 output from the speed command analysis unit 41 and the current feedback instruction information S5 input from the current feedback unit 62 or the speed feedback instruction information S6 input from the speed feedback unit 63.

[0069] Specifically, when the duty ratio determination unit 42 receives the current feedback instruction information S5, it determines the duty ratio information S2 based on the current feedback instruction information S5 so that the actual measured current value of the motor 100 matches the current threshold value Sth of 5.0 (A).

[0070] Furthermore, when the duty ratio determination unit 42 receives the speed feedback instruction information S6, it determines the duty ratio information S2 based on the speed feedback instruction information S6 so that the actual rotation speed Rmv of the motor 100 matches the target rotation speed information S1 (target rotation speed Rtg) from the speed command analysis unit 41.

[0071] Next, the drive control process procedure of the motor 100 by the power control unit 60 will be described. FIG. 2 is a flowchart showing an example of the flow of a motor drive control process based on the operation of the power control unit 60 in the motor drive control device 3 of the fan system 1 according to this embodiment.

[0072] The operation command unit 61 of the power control unit 60 calculates the target rotation speed Rtg (rpm) based on the target rotation speed information S1 input from the speed command analysis unit 41 (step S1). Next, immediately after the motor 100 starts to drive, the operation command unit 61 calculates the actual rotation speed Rmv (rpm) of the motor 100 during driving based on the rotation speed information Sr input from the rotation speed monitoring unit 51 (step S2).

[0073] Immediately after starting to drive the motor 100, the operation command unit 61 outputs operation command information S4 to the speed feedback unit 63 to instruct the actual rotation speed Rmv of the motor 100 to match the target rotation speed Rtg, thereby executing the speed feedback control mode (step S3). During the speed feedback control mode, the motor drive control device 3 controls the drive of the motor 100 so that the actual rotation speed Rmv of the motor 100 matches the target rotation speed Rtg.

[0074] Specifically, the speed feedback unit 63 generates speed feedback instruction information S6 including the actual rotation speed Rmv of the motor 100 in accordance with the operation command information S4 received from the operation command unit 61, and outputs the generated speed feedback instruction information S6 to the duty ratio determiner 42 of the drive control signal generator 40. The duty ratio determiner 42 calculates the difference between the actual rotation speed Rmv and the target rotation speed Rtg of the motor 100 based on the speed feedback instruction information S6 received from the speed feedback unit 63, determines the duty ratio of the PWM signal serving as the drive control signal Sd so that the difference becomes zero, and outputs the determined duty ratio information S2 to the energization control unit 43. The energization control unit 43 generates the drive control signal Sd based on the duty ratio information S2, thereby driving the motor 100 so that the actual rotation speed Rmv of the motor 100 matches the target rotation speed Rtg.

[0075] During execution of the speed feedback control mode, the operation command unit 61 monitors the drive current information Si, which is the actual current measurement value corresponding to the detected current (voltage Vm) detected by the current detector 70 (step S4). In the speed feedback control mode, the actual rotation speed Rmv of the motor 100 is attempted to match the target rotation speed Rtg, so if the load on the motor 100 increases for some reason, the drive current of the motor 100 increases.

[0076] At this time, the current monitoring unit 53 calculates the actual measured current value of the motor 100 using, for example, a ΔΣADC, and calculates the drive current information Si. Here, the drive current information Si is specifically the integral value of the detected current (voltage Vm) over a certain period of time, and is not the instantaneous peak value of the drive current at a certain point in time.

[0077] The operation command unit 61 compares the actual current measurement value (drive current information Si) calculated by the current monitoring unit 53 with a current threshold value Sth set according to the voltage value of the power supply voltage Vdd, and determines whether the actual current measurement value (drive current information Si) is greater than or equal to the current threshold value Sth (step S5).

[0078] If the actual current measurement value (drive current information Si) is less than the current threshold value Sth (step S5: NO), the operation command unit 61 returns to step S3 and, while remaining in the speed feedback control mode, controls the drive so that the actual rotation speed Rmv of the motor 100 matches the target rotation speed Rtg. In this case, since the actual current measurement value (drive current information Si) is less than the current threshold value Sth, the load on the motor 100 has not increased, and the drive current of the motor 100 has not increased either.

[0079] In response to this, if the actual current measurement value (drive current information Si) becomes equal to or greater than the current threshold value Sth (step S5: YES), the operation command unit 61 stops the speed feedback control mode and switches from the speed feedback control mode to the current feedback control mode (step S6).

[0080] The reason why the measured current value (drive current information Si) exceeds the current threshold value Sth is that in the speed feedback control mode, even though the actual rotation speed Rmv of the motor 100 is being made to match the target rotation speed Rtg, if the load on the motor 100 increases for some reason, a large drive current is required.

[0081] Specifically, the operation command unit 61 stops outputting operation command information S4 to the speed feedback unit 63 and outputs operation command information S3 to the current feedback unit 62, causing the current feedback unit 62 to execute the current feedback control mode. The current feedback unit 62 generates current feedback instruction information S5 in response to the operation command information S3 received from the operation command unit 61 and outputs the information to the duty ratio determiner 42 of the drive control signal generator 40. Based on the current feedback instruction information S5 received from the current feedback unit 62, the duty ratio determiner 42 determines duty ratio information S2 so that the actual current value (drive current information Si) matches the current threshold value Sth of 5.0 (A), and outputs the information to the energization control unit 43. The energization control unit 43 outputs the drive control signal Sd generated based on the duty ratio information S2 via the motor drive unit 90, thereby driving the motor 100 so that the actual current value (drive current information Si) matches the current threshold value Sth of 5.0 (A).

[0082] Next, a description will be given of a change in drive current due to speed feedback control using conventional overcurrent protection and a change in drive current due to power control according to this embodiment.

[0083] Fig. 3(A) is a diagram showing an example of the change in drive current in speed feedback control using conventional overcurrent protection, and Fig. 3(B) is a diagram showing an example of the change in drive current using power control according to this embodiment. In both figures, the curve indicated by the symbol W shows the required air volume-static pressure characteristic (PQ characteristic).

[0084] As shown in Figure 3(A), when only speed feedback control using conventional overcurrent protection is performed, the load on motor 100 is large in the two air volume regions surrounded by dashed lines (the region where air volume is 0 to q1 and the region between q2 and q3), and even when the drive current must be limited to 5.0 (A), the drive current of motor 100 increases and exceeds the current threshold value Sth of 5.0 (A).

[0085] To avoid such a situation, the operation command unit 61 of the power control unit 60 according to this embodiment issues a command to switch from the speed feedback control mode to the current feedback control mode. The operation command unit 61 executes the current feedback control mode by controlling the drive current of the motor 100 so that the actual current measurement value (drive current information Si) coincides with the current threshold value Sth (step S7).

[0086] As a result, the motor drive control device 3 can control the actual current measurement value (drive current information Si) so that it does not exceed the current threshold value Sth of 5.0 (A) in the entire air volume range (0 to q3) determined by the PQ characteristics, as shown in Figure 3 (B).

[0087] 3(B), the actual current measurement value (drive current information Si) does not exceed the current threshold value Sth of 5.0 (A) not only in the speed feedback control mode executed in regions B and D but also in the current feedback control mode executed in regions A and C. Therefore, the motor drive control device 3 can prevent damage to the motor 100, motor drive unit 90, etc. due to an increase in drive current.

[0088] Thus, in the current feedback control mode, the motor drive control device 3 controls the actual current measurement value (drive current information Si) so that it matches the current threshold value Sth of 5.0 (A), so that the drive current is not restricted more than necessary in anticipation of the risk of damage to the motor 100, etc., and it is possible to obtain the desired air volume-static pressure characteristic (PQ characteristic) that exceeds the air volume-static pressure characteristic (PQ characteristic) W required in the operating range.

[0089] While the current feedback control mode is being executed (step S7), the operation command unit 61 determines whether the actual rotation speed Rmv of the motor 100 exceeds a predetermined percentage (X%) of the target rotation speed Rtg (expressed as "Rmv>Rtg+X(%)"). For example, if the target rotation speed Rtg is 16,800 rpm and X=5%, when the actual rotation speed Rmv of the motor 100 exceeds 17,640 rpm, this means that the load on the motor 100 has decreased and the drive current can be reduced from the current value. Therefore, the operation command unit 61 returns to step S3, and the control mode can be changed back from the current feedback control mode to the velocity feedback control mode (step S3).

[0090] In this embodiment, when returning from current feedback control mode to velocity feedback control mode, the criterion for judgment is whether the actual rotation speed Rmv of the motor 100 exceeds a predetermined percentage (X%) of the target rotation speed Rtg. However, the judgment is not limited to this, and the criterion for judgment may be whether the actual rotation speed Rmv of the motor 100 exceeds the target rotation speed Rtg by a predetermined value (Y rpm) (whether "Rmv > Rtg + Y" holds). Note that the values ​​X and Y can be set arbitrarily. In other words, the criterion for judgment is whether the actual rotation speed Rmv of the motor 100 falls within a predetermined range of the target rotation speed Rtg.

[0091] Here, when the actual rotation speed Rmv of the motor 100 exceeds the target rotation speed Rtg+X%, it is considered that the actual current measurement value (drive current information Si) obtained by smoothing the detected current in the current feedback control mode has become less than the current threshold value Sth, and therefore the operation command unit 61 switches from the current feedback control mode to the speed feedback control mode.

[0092] Thereafter, the operation command unit 61 repeats the processing of steps S3 to S8, and controls the drive of the motor 100 while switching between the speed feedback control mode and the current feedback control mode.

[0093] Next, differences between the current limiting function based on the conventional overcurrent protection and the current limiting function based on the current feedback control mode according to this embodiment will be described.

[0094] FIG. 4 is a diagram showing an example of drive current limitation by conventional overcurrent protection. FIG. 5 is a diagram showing an example of drive current limitation in current feedback control mode according to the present embodiment. In FIG. 4, the upper part shows the current waveform of the detected current and the value of the motor drive current (actually flowing current) before limitation, and the lower part shows the current waveform of the detected current and the value of the motor drive current (actually flowing current) after limitation. In FIG. 5, the upper part shows the current waveform of the detected current and the value of the actual current (actually flowing current) before limitation, and the lower part shows the current waveform of the detected current and the value of the actual current (actually flowing current) after limitation. Also, (a) to (d) of FIG. 4 and FIG. 5 each show example current waveform patterns.

[0095] As shown in Figure 4, in a conventional motor drive control device, when overcurrent protection is used to determine whether an overcurrent state exists that exceeds the current threshold using the peak current value, in (a), (c), and (d), the peak current value exceeds 5.0 (A) at a certain timing, so at that point, the drive current is temporarily stopped until the peak current value falls below 5.0 (A).

[0096] For example, in the case of Figure 4(a), even if the average value of the drive current is 5.0 (A), the detected current (peak value) exceeds 5.0 (A) at a certain point, so the drive current is temporarily stopped. As a result, the effective value of the drive current becomes 4.66 (A). As a result, the required air volume vs. static pressure characteristics (PQ characteristics) cannot be obtained.

[0097] In the case of Figure 4(b), the detected current (peak value) does not exceed 5.0 A, so the drive current is not stopped and the effective value of the drive current remains at 5.0 A. However, in the cases of Figures 4(c) and 4(d), the detected current (peak value) exceeds 5.0 A at a certain point, so the drive current is stopped. As a result, the effective value of the drive current becomes 4.66 A, just like in Figure 4(a). In other words, with current limiting using conventional overcurrent protection, the effective value of the drive current falls below the desired value, making it impossible to achieve the required PQ characteristics.

[0098] In contrast, in the motor drive control device 3 according to this embodiment, the current monitoring unit 53, as an example, calculates the actual measured current value (drive current information Si) in digital form by integrating the voltage Vm (analog signal) corresponding to the detected current over time using a ΔΣADC.

[0099] As shown in Figures 5(a) and 5(c), even if the detected current (peak value) exceeds 5.0 A at a certain timing, the drive current will continue to be supplied without reduction as long as the actual measured current value is less than 5.0 A. This allows the motor drive control device 3 to maintain the originally required PQ characteristics of the motor 100, as shown in Figure 3(B).

[0100] Also, as shown in Figure 5(b), if the drive current is less than 5.0 (A) at all times, the actual measured current value, which is the average value of the drive current, is less than the current threshold value Sth, so in this case too, the drive current will be supplied without being reduced.

[0101] On the other hand, as shown in Figure 5(d), even if the detected current (peak value) exceeds 5.0 (A) at a certain timing and the actual measured current value exceeds the current threshold value Sth, such as 5.33 (A), the drive current is not stopped but is reduced so that the actual measured current value matches the current threshold value Sth (5.0 (A)). This allows the motor drive control device 3 to suppress the drive current so that it does not exceed the current threshold value Sth that meets the customer's requirements or specifications.

[0102] In other words, in the motor drive control device 3 of this embodiment, even if the instantaneous detected current (peak value) exceeds 5.0 (A), it is possible to supply a drive current controlled so that the drive current matches the current threshold value Sth of 5.0 (A).

[0103] 6 shows a comparison example of the change in actual motor rotation speed relative to airflow in conventional speed feedback control and power control according to this embodiment. Specifically, waveform Wm shows the change in actual motor rotation speed relative to airflow in conventional speed feedback control, and waveform Im shows the change in actual motor rotation speed Rmv relative to airflow in power control according to this embodiment.

[0104] 6, in conventional control using only speed feedback control, the actual rotation speed of the motor, as indicated by the waveform Wm, is approximately constant at about 17,000 rpm over the entire air volume range. In contrast, in power control according to the present embodiment, which controls the drive of motor 100 by switching between a speed feedback control mode (speed FB control mode) and a current feedback control mode (current FB control mode), as indicated by the waveform Im, in the current feedback control mode, the actual rotation speed Rmv fluctuates between approximately 17,000 rpm and approximately 15,700 rpm, compared to the waveform Wm of conventional speed feedback control.

[0105] Conventional speed feedback control controls the actual rotation speed of the motor so that it matches the target rotation speed, so the actual rotation speed of the motor is constant at around 17,000 rpm, but the drive current increases in the air volume range where the load on the motor is large.

[0106] In contrast, in the case of power control according to the present embodiment, which is performed by switching between speed feedback control mode and current feedback control mode, when the speed feedback control mode is being executed, the actual rotation speed Rmv of the motor 100 is controlled to be around 17,000 rpm.

[0107] On the other hand, when the current feedback control mode is being executed, the actual rotation speed Rmv of the motor 100 is farther away from approximately 17,000 rpm than in the case of conventional speed feedback control. This is because in the current feedback control mode, even when the load on the motor 100 is large and the actual rotation speed Rmv is decreasing, the drive current is limited to approximately 5.0 (A) so that it matches the current threshold value Sth.

[0108] While the actual rotation speed of the motor in conventional speed feedback control is approximately 17,000 rpm, the actual rotation speed Rmv of motor 100 in the operating range in the current feedback control mode according to this embodiment drops to approximately 16,700 rpm. However, in reality, the rate of this drop (the rate of decrease of 16,700 rpm from 17,000 rpm) is only about 2%, which is well within the specification range (for example, target rotation speed ±5%) and does not pose a problem.

[0109] As described above, the motor drive control device 3 according to this embodiment controls the actual rotation speed Rmv of the motor 100 so that it matches the target rotation speed Rtg in the speed feedback control mode, and when the actual current measurement value as the drive current information Si becomes equal to or greater than the current threshold value Sth, stops the speed feedback control mode and switches to the current feedback control mode. In this way, even if the load on the motor 100 increases, by executing the current feedback control mode, it is possible to prevent a drive current that greatly exceeds the current threshold value Sth from flowing through the motor 100.

[0110] In the current feedback control mode, the motor drive control device 3 controls the drive current to the motor 100 so that it matches the current threshold value Sth, thereby preventing damage to the motor 100, the motor drive unit 90, etc.

[0111] When the power control unit 60 of the motor drive control device 3 detects that the actual rotation speed Rmv of the motor 100 falls within a predetermined range of the target rotation speed Rtg while in current feedback control mode, it switches to speed feedback control mode. Specifically, the operation command unit 61 of the power control unit 60 monitors the actual rotation speed Rmv of the motor 100, and when the actual rotation speed Rmv of the motor 100 exceeds a predetermined percentage (X%) of the target rotation speed Rtg or a predetermined value (Y rpm) (X and Y are arbitrary numerical values) of the target rotation speed Rtg, it determines that the load on the motor 100 has lightened and switches back from current feedback control mode to speed feedback control mode.

[0112] As described above, when the load on the motor 100 becomes lighter while the current feedback control mode is in operation, and the drive current of the motor 100 can be set to a value lower than the current threshold Sth, the control mode is switched back from the current feedback control mode to the speed feedback control mode, thereby avoiding the flow of excess drive current to the motor 100.

[0113] In this way, the motor drive control device 3 can maintain the air volume-static pressure characteristics (PQ characteristics) required for the motor 100 while suppressing unnecessary power consumption by switching between the current feedback control mode and the speed feedback control mode based on the current threshold Sth.

[0114] In addition, the motor drive control device 3 controls the drive of the motor 100 by switching between speed feedback control mode and current feedback control mode depending on the load on the motor 100 over the entire air volume range, thereby satisfying the current limitations required by customer requests and specifications not only within the operating range but also over the entire air volume range determined by the air volume-static pressure characteristics (PQ characteristics).

[0115] <Extension of the embodiment of the present invention> The present invention made by the inventors 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.

[0116] For example, in the present embodiment, the operation command unit 61 executes the speed feedback control mode when the motor 100 is first driven and then switches to the current feedback control mode, but the present invention is not limited to this, and the current feedback control mode may be executed when the motor 100 is first driven and then switched to the speed feedback control mode. In other words, it does not matter which control mode is executed first, as long as the speed feedback control mode and the current feedback control mode can be alternately switched.

[0117] The number of phases of the motor 100 driven by the motor drive control device 3 of the above-described embodiment is not limited to three. Furthermore, the number of Hall elements is not limited to three.

[0118] Furthermore, there is no particular limitation on the method for detecting the actual rotation speed Rmv of motor 100. For example, a position sensorless method may be used in which the actual rotation speed Rmv is detected using a back electromotive force induced in the motor coil, without using a position detector such as a Hall element.

[0119] The above-described flowchart is a specific example, and the present invention is not limited to this flowchart. For example, other processes may be inserted between each step, or the processes may be parallelized. [Explanation of symbols]

[0120] 1...fan system, 2...host device, 3...motor drive control device, 4...control circuit section, 10...motor unit, 21...speed command section, 22...power supply section, 40...drive control signal generation section, 41...speed command analysis section, 42...duty ratio determination section, 43...energization control section, 51...rotation speed monitoring section, 52...FG signal generation section, 53...current monitoring section, 54...power supply voltage monitoring section, 60...power control section, 61...operation command section, 62...current feedback section, 63...speed feedback section, 70...current detector, 90...motor drive section, 91...inverter circuit, 100...motor, 10 1...position detector, Im...waveform indicating actual rotation speed, Rmv...actual rotation speed, Rtg...target rotation speed, Sc...speed command signal, Sd...drive control signal, So...rotation speed signal, Sh...position detection signal, Sv...power supply voltage information, Sr...rotation speed information, Si...drive current information (actual measured current value), Sth...current threshold (target current), S1...target rotation speed information, S2...duty ratio information, S3, S4...operation command information, S5...current feedback instruction information, S6...speed feedback instruction information, Vdd...power supply voltage, Vm...voltage, W...air volume-static pressure characteristics, Wm...waveform indicating actual rotation speed.

Claims

1. a control circuit unit that generates a drive control signal for controlling an actual rotation speed of the motor based on a speed command signal that indicates a target rotation speed of the motor; a motor drive unit that drives the motor based on the drive control signal, the control circuit unit has a power control unit that can select either a speed feedback control mode in which the drive control signal is generated so that the actual rotation speed of the motor coincides with the target rotation speed, or a current feedback control mode in which the drive control signal is generated so that the drive current of the motor coincides with the target current, The power control unit A current threshold value corresponding to an externally supplied power supply voltage is set as the target current, and when it is detected that the drive current has reached or exceeded the current threshold value, the control mode is switched from the speed feedback control mode to the current feedback control mode. Motor drive control device.

2. 2. The motor drive control device according to claim 1, When the power control unit detects that the drive current has become less than the current threshold in the current feedback control mode, the power control unit switches from the current feedback control mode to the speed feedback control mode. Motor drive control device.

3. 3. The motor drive control device according to claim 1, The power control unit is capable of selecting the speed feedback control mode and the current feedback control mode within the entire air volume range from minimum to maximum, the air volume being determined by the air volume-static pressure characteristics of the motor. Motor drive control device.

4. 4. The motor drive control device according to claim 1, a current detector for detecting the drive current; a current monitoring unit that acquires, as the drive current, a current measurement value calculated by smoothing the detected current detected by the current detector; Equipped with Motor drive control device.

5. 5. The motor drive control device according to claim 4, The detected current, which is an analog signal, is converted into a digital signal by a ΔΣ ADC. Motor drive control device.

6. 6. The motor drive control device according to claim 1, The power control unit switches to the speed feedback control mode when detecting that the actual rotation speed of the motor falls within a predetermined range with respect to the target rotation speed during execution of the current feedback control mode. Motor drive control device.

7. 7. The motor drive control device according to claim 1, The power control unit an operation command unit that selectively switches between the speed feedback control mode and the current feedback control mode; a current feedback control unit that controls the drive current so that it coincides with the target current in response to a command from the operation command unit; a speed feedback control unit that controls the actual rotation speed of the motor in response to a command from the operation command unit so that the actual rotation speed of the motor coincides with the target rotation speed; Equipped with Motor drive control device.

8. 8. The motor drive control device according to claim 7, The operation command unit changes the current threshold value in accordance with the value of the power supply voltage so that the power of the motor becomes a desired value. Motor drive control device.

9. a motor to be driven; a motor drive control device that controls the drive of the motor, The motor drive control device includes: a control circuit that generates a drive control signal for controlling an actual rotation speed of the motor based on a speed command signal that indicates a target rotation speed of the motor; a motor drive unit that drives the motor based on the drive control signal, the control circuit unit has a power control unit that can select, as a drive control mode, either a speed feedback control mode in which the drive control signal is generated so that the actual rotation speed of the motor coincides with the target rotation speed, or a current feedback control mode in which the drive control signal is generated so that the drive current of the motor coincides with the target current, The power control unit A current threshold value corresponding to an externally supplied power supply voltage is set as the target current, and when it is detected that the drive current has reached or exceeded the current threshold value, the control mode is switched from the speed feedback control mode to the current feedback control mode. Motor unit.

10. a drive control signal generating step of generating, by a control circuit unit, a drive control signal for controlling an actual rotation speed of the motor based on a speed command signal indicating a target rotation speed of the motor to be driven; a motor driving step of driving the motor by a motor driving unit based on the drive control signal, the drive control signal generating step includes a drive control step in which, as a drive control mode controlled by a power control unit, it is possible to select either a speed feedback control mode in which the drive control signal is generated so that the actual rotation speed of the motor coincides with the target rotation speed, or a current feedback control mode in which the drive control signal is generated so that the drive current of the motor coincides with a target current; In the drive control step, A current threshold value corresponding to an externally supplied power supply voltage is set as the target current, and when it is detected that the drive current has reached or exceeded the current threshold value, the control mode is switched from the speed feedback control mode to the current feedback control mode. Motor drive control method.

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