Control circuit, motor drive device, motor system, and control method

Abstract

To suppress a loss increase of a motor caused by distortion of a phase current waveform of the motor.SOLUTION: A control circuit (2) controls an inverter (1) which drives a motor (Z1). The control circuit comprises: a determination section (21) which determines whether or not distortion of a phase current waveform of the motor is equal to or more than a first predetermined level; and a frequency adjustment section (22) which lowers a switching frequency of the inverter in a case where it is determined by the determination section that the distortion of the phase current waveform is equal to or more than the first predetermined level.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a control circuit, a motor drive device, a motor system, and a control method. [Background technology]

[0002] Generally, when a motor rotates, a ripple current is generated in the motor (see, for example, Patent Document 1). By increasing the switching frequency of the inverter that drives the motor, the ripple current can be reduced, and motor losses can be reduced. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 7-222483

[0004] [overview] However, if the switching frequency of the inverter is set too high, the distortion of the phase current waveform of the motor becomes large, and there is a risk that the increased distortion of the phase current waveform of the motor will increase the loss of the motor.

[0005] A control circuit according to the present disclosure is configured to control an inverter configured to drive a motor, and includes a determination unit configured to determine whether distortion of a phase current waveform of the motor is equal to or greater than a first predetermined level, and a frequency adjustment unit configured to reduce a switching frequency of the inverter when the determination unit determines that the distortion of the phase current waveform is equal to or greater than the first predetermined level.

[0006] A motor drive device according to the present disclosure includes the control circuit configured as described above, the inverter, and a detector configured to detect the phase current waveforms.

[0007] A motor system according to the present disclosure includes the motor drive device configured as described above and the motor. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing a configuration of a motor system according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a diagram illustrating a first configuration example of the determination unit. [Figure 3] FIG. 3 is a flowchart showing a first operation example of the control circuit. [Figure 4] FIG. 4 is a flowchart showing a second operation example of the control circuit. [Figure 5] FIG. 5 is a diagram illustrating a second configuration example of the determination unit. [Figure 6] FIG. 6 is a flowchart showing a third operation example of the control circuit.

[0009] [Detailed explanation] 1 is a diagram showing the configuration of a motor system according to an embodiment of the present disclosure. The motor system X1 includes a motor drive device Y1 and a motor Z1.

[0010] The motor drive device Y1 includes an inverter 1, a control circuit 2, and a current detector 3.

[0011] The inverter 1 converts DC power into AC power and supplies the converted AC power to the motor Z1 to drive the motor Z1. In the example shown in Fig. 1, the inverter 1 is a three-phase inverter, but the inverter 1 may also be, for example, a single-phase inverter.

[0012] 1 includes a U-phase leg, a V-phase leg, and a W-phase leg, which are connected in parallel.

[0013] The U-phase leg includes a high-side transistor MHU as an upper arm and a low-side transistor MLU as a lower arm. The V-phase leg includes a high-side transistor MHV as an upper arm and a low-side transistor MLV as a lower arm. The W-phase leg includes a high-side transistor MHW as an upper arm and a low-side transistor MLW as a lower arm. The U-phase leg supplies U-phase current to motor Z1. The V-phase leg supplies V-phase current to motor Z1. The W-phase leg supplies W-phase current to motor Z1.

[0014] In the configuration shown in FIG. 1, the transistors included in the inverter 1 are NMOS (n-channel Metal Oxide Semiconductor) transistors, but some or all of the transistors included in the inverter 1 may be transistors other than NMOS transistors.

[0015] The current detector 3 detects the phase current and outputs the detection result as a voltage signal. Since the current detector 3 continuously detects the phase current, it also detects the phase current waveform. For example, a shunt resistor, a current transformer, etc. can be used as the current detector 3.

[0016] 1, the current detector 3 detects the W-phase current, but the current detector 3 may detect a phase current other than the W-phase current. Also, in the configuration shown in FIG. 1, the current detector 3 is provided outside the control circuit 2, but the current detector 3 may be built into the control circuit 2.

[0017] The control circuit 2 controls the inverter 1 based on, for example, a signal indicating the target rotation speed of the motor Z1, a signal indicating the rotor position of the motor Z1, and the like.

[0018] The control circuit 2 includes a determination unit 21 and a frequency adjustment unit 22. The control circuit 2 may include, for example, a processor and a memory. The processor executes a control program stored in the memory to realize the functions of the determination unit 21 and the frequency adjustment unit 22. Note that part or all of the determination unit 21 and the frequency adjustment unit 22 may be realized by dedicated circuits.

[0019] The determining unit 21 determines whether or not the distortion of the phase current waveform detected by the current detector 3 is equal to or greater than a first predetermined level.

[0020] When the determination unit 21 determines that the distortion of the phase current waveform is equal to or greater than a first predetermined level, the frequency adjustment unit 22 reduces the switching frequency of the inverter 1. Specifically, the frequency adjustment unit 22 generates gate drive signals GHU, GLU, GHV, GLV, GHW, and GLW, and when the determination unit 21 determines that the distortion of the phase current waveform is equal to or greater than a first predetermined level, the frequency adjustment unit 22 reduces the frequencies of the gate drive signals GHU, GLU, GHV, GLV, GHW, and GLW.

[0021] By adjusting the switching frequency of inverter 1 with frequency adjustment unit 22, it is possible to suppress an increase in motor loss due to distortion of the motor's phase current waveform. Furthermore, even if the specific structure of inverter 1 or the specific structure of motor Z1 is changed, by adjusting the switching frequency of inverter 1 with frequency adjustment unit 22, it is possible to suppress an increase in motor loss due to distortion of the motor's phase current waveform.

[0022] A gate drive signal GHU is supplied to the gate of the high-side transistor MHU. A gate drive signal GLU is supplied to the gate of the low-side transistor MLU. A gate drive signal GHV is supplied to the gate of the high-side transistor MHV. A gate drive signal GLV is supplied to the gate of the low-side transistor MLV. A gate drive signal GHW is supplied to the gate of the high-side transistor MHW. A gate drive signal GLW is supplied to the gate of the low-side transistor MLW. The gate drive signals GHU, GLU, GHV, GLV, GHW, and GLW are, for example, PWM (Pulse Width Modulation) signals.

[0023] In the configuration shown in FIG. 1, the control circuit 2 outputs each gate drive signal. Alternatively, the control circuit 2 may output each gate control signal, and a pre-driver may be provided between the control circuit 2 and the inverter, and the pre-driver may amplify the gate control signal to generate the gate drive signal.

[0024] Fig. 2 is a diagram illustrating a first exemplary configuration of the determination unit 21. The determination unit 21 illustrated in Fig. 2 includes a conversion unit 211. The conversion unit 211 converts the phase current waveform into a frequency spectrum. The conversion unit 211 performs, for example, FFT (Fast Fourier Transformation) processing on the phase current waveform to convert the phase current waveform into a frequency spectrum.

[0025] 3 is a flowchart showing a first operation example of the control circuit 2. The control circuit 2 that performs the first operation example includes the determination unit 21 shown in FIG.

[0026] When starting the rotation control of the motor Z1, the control circuit 2 starts the flow shown in Fig. 3. When ending the rotation control of the motor Z1, the control circuit 2 ends the flow shown in Fig. 3 by interrupt processing.

[0027] First, in step S10, the determination unit 21 acquires the phase current waveform for the most recent fixed period. For example, the determination unit 21 includes a buffer memory, and information about the phase current waveform for the fixed period is stored in the buffer memory.

[0028] During the rotation control of motor Z1, step S10 is repeatedly executed. The fixed period in the previous step S10 and the fixed period in the current step S10 may partially overlap, or may be continuous with the fixed period in the current step S10, or may be separated from each other.

[0029] In the next step S20, the conversion unit 211 performs FFT (Fast Fourier Transformation) processing on the phase current waveform for the fixed period acquired in step S10, and converts the phase current waveform for the fixed period acquired in step S10 into a frequency spectrum.

[0030] In the next step S30, the determination unit 21 determines whether or not the distortion of the phase current waveform is equal to or greater than a first predetermined level LV1, based on the frequency spectrum obtained in step S20.

[0031] The determination unit 21 may determine whether the distortion of the phase current waveform is equal to or greater than a first predetermined level LV1 based on components of the frequency spectrum obtained in step S20 that are equal to or greater than twice the rotational frequency of the motor Z1. This determination prevents frequency components generated by the rotation of the motor Z1 from being mistakenly treated as frequency components generated by distortion of the phase current waveform. Note that the rotational frequency of the motor Z1 may be a target rotational frequency of the motor Z1 or an actual rotational frequency of the motor Z1.

[0032] Furthermore, the determination unit 21 may determine whether the distortion of the phase current waveform is equal to or greater than a first predetermined level LV1 based on the maximum value of the components of the frequency spectrum obtained in step S20 that are equal to or greater than twice the rotational frequency of the motor Z1. For example, if the maximum value of the components of the frequency spectrum obtained in step S20 that are equal to or greater than twice the rotational frequency of the motor Z1 is equal to or greater than a threshold value, the determination unit 21 may determine that the distortion of the phase current waveform is equal to or greater than the first predetermined level LV1. Alternatively, for example, if a certain number of peak values ​​(maximum values) of the components of the frequency spectrum obtained in step S20 that are equal to or greater than twice the rotational frequency of the motor Z1 are taken in descending order, and if their average or total value is equal to or greater than a threshold value, the determination unit 21 may determine that the distortion of the phase current waveform is equal to or greater than the first predetermined level LV1.

[0033] If it is determined that the distortion of the phase current waveform is equal to or greater than the first predetermined level LV1 (YES in step S30), the frequency adjuster 22 reduces the switching frequency of the inverter 1 by a predetermined value Δf1 (step S40). After the processing of step S40 is completed, the process returns to step S10. The predetermined value Δf1 is a positive value. The predetermined value Δf1 may be a fixed value or a variable value that increases as the distortion of the phase current waveform increases.

[0034] If it is determined that the distortion of the phase current waveform is less than the first predetermined level LV1 (NO in step S30), the frequency adjuster 22 increases the switching frequency of the inverter 1 by a predetermined value Δf2 (step S50). The processing of step S50 makes it possible to suppress an increase in loss in the motor Z1 due to an increase in the ripple current. When the processing of step S50 ends, the process returns to step S10. The predetermined value Δf2 is a positive value. The predetermined value Δf2 may be a fixed value or may be a variable value that increases as the distortion of the phase current waveform increases. When the predetermined values ​​Δf1 and Δf2 are both fixed values, the predetermined values ​​Δf1 and Δf2 may be the same value or may be different values.

[0035] 3 is a loop, so that frequency adjuster 22 continues to lower the switching frequency of inverter 1 until determiner 21 determines that the distortion of the phase current waveform is less than first predetermined level LV1. Therefore, the distortion of the phase current waveform can be reliably reduced to less than first predetermined level LV1.

[0036] 3, there is a risk that the switching frequency of the inverter 1 will frequently increase and decrease repeatedly. In order to suppress the frequency at which the switching frequency of the inverter 1 will increase and decrease repeatedly, the frequency adjuster 22 may have a hysteresis characteristic.

[0037] Fig. 4 is a flowchart showing a second operation example of the control circuit 2. The control circuit 2 performing the second operation example includes the determination unit 21 shown in Fig. 2 and the frequency adjustment unit 22 having a hysteresis characteristic.

[0038] The flowchart shown in Fig. 4 is obtained by adding steps S1, S41, S42, S43, and S51 to the flowchart shown in Fig. 3. In the following description of the flowchart shown in Fig. 4, points that overlap with the description of the flowchart shown in Fig. 3 will be omitted as appropriate.

[0039] First, in step S1, frequency adjuster 22 sets the value of parameter LVn to 0. For example, frequency adjuster 22 includes a buffer memory, and the value of parameter LVn is stored in the buffer memory.

[0040] In the next step S10, the determination unit 21 acquires the phase current waveforms for the most recent fixed period.

[0041] In the next step S20, the conversion unit 211 performs FFT processing on the phase current waveform for the fixed period acquired in step S10, and converts the phase current waveform for the fixed period acquired in step S10 into a frequency spectrum.

[0042] In the next step S30, the determination unit 21 determines whether or not the distortion of the phase current waveform is equal to or greater than a first predetermined level LV1, based on the frequency spectrum obtained in step S20.

[0043] If it is determined that the distortion of the phase current waveform is equal to or greater than the first predetermined level LV1 (YES in step S30), frequency adjuster 22 reduces the switching frequency of inverter 1 by a predetermined value Δf1 (step S40). After completing the process of step S40, frequency adjuster 22 sets the value of parameter LVn to 1 (step S41), and then returns to step S10.

[0044] If it is determined that the distortion of the phase current waveform is less than the first predetermined level LV1 (NO in step S30), the determination unit 21 determines whether the distortion of the phase current waveform is equal to or greater than a second predetermined level LV2 based on the frequency spectrum obtained in step S20 (step S42). Note that the second predetermined level LV2 is lower than the first predetermined level LV1.

[0045] If it is determined that the distortion of the phase current waveform is equal to or greater than the second predetermined level LV2 (YES in step S42), frequency adjuster 22 determines whether or not parameter LVn is 1 (step S43). If it is determined that parameter LVn is 1 (YES in step S43), the process proceeds to step S40. On the other hand, if it is determined that parameter LVn is not 1 (NO in step S43), the process proceeds to step S50.

[0046] Also, if it is determined that the distortion of the phase current waveform is less than the second predetermined level LV2 (NO in step S42), the process proceeds to step S50.

[0047] In step S50, frequency adjuster 22 increases the switching frequency of inverter 1 by a predetermined value Δf2. In step S51 following step S50, frequency adjuster 22 sets the value of parameter LVn to 0 (step S51), and then returns to step S10.

[0048] Fig. 5 is a diagram showing a second configuration example of the determination unit 21. The determination unit 21 shown in Fig. 5 includes a waveform comparison unit 212. The waveform comparison unit 212 compares the phase current waveform with a reference sine wave waveform. The frequency of the reference sine wave waveform corresponds to the target rotation frequency of the motor Z1. The comparison result between the phase current waveform (target waveform) and the reference sine wave waveform (template waveform) is, for example, the similarity obtained by template matching.

[0049] 6 is a flowchart showing a third operation example of the control circuit 2. The control circuit 2 performing the third operation example includes the determination unit 21 shown in FIG.

[0050] The flowchart shown in Fig. 6 is obtained by replacing step S20 with step S25 in the flowchart shown in Fig. 3. Below, differences between the flowchart shown in Fig. 6 and the flowchart shown in Fig. 3 will be described.

[0051] In step S25, the waveform comparison unit 212 compares the phase current waveform with a reference sinusoidal waveform.

[0052] Then, in step S30, the determination unit 21 determines whether or not the distortion of the phase current waveform is equal to or greater than a first predetermined level LV1, based on the comparison result obtained in step S20.

[0053] <Other> The above-described embodiments should be considered to be illustrative in all respects and not restrictive. The technical scope of the present disclosure is indicated by the claims, not by the description of the above-described embodiments, and should be understood to include all modifications that fall within the meaning and scope equivalent to the claims.

[0054] For example, the control circuit 1 may be configured to include a determination unit 21 and a frequency adjustment unit 22 having a hysteresis characteristic, as shown in FIG.

[0055] <Additional Notes> A supplementary note will be provided for the present disclosure, the specific configuration examples of which have been shown in the above-described embodiments.

[0056] The control circuit (2) of the present disclosure is a control circuit configured to control an inverter (1) configured to drive a motor (Z1), and has a configuration (first configuration) including a determination unit (21) configured to determine whether or not distortion of a phase current waveform of the motor is equal to or greater than a first predetermined level, and a frequency adjustment unit (22) configured to lower the switching frequency of the inverter when the determination unit determines that the distortion of the phase current waveform is equal to or greater than the first predetermined level.

[0057] According to the control circuit of the first configuration, the switching frequency of the inverter can be lowered when it is determined that the distortion of the motor's phase current waveform is equal to or greater than a first predetermined level, thereby suppressing an increase in motor loss due to distortion of the motor's phase current waveform.

[0058] In the control circuit of the first configuration, the frequency adjustment unit may be configured to continue lowering the switching frequency until the determination unit determines that the distortion of the phase current waveform is less than the first predetermined level (second configuration).

[0059] In the control circuit of the second configuration, the frequency adjustment unit may be configured to increase the switching frequency when the judgment unit determines that the distortion of the phase current waveform is less than the first predetermined level (third configuration).

[0060] In the control circuit of the second configuration, the judgment unit may also be configured to judge whether the distortion of the phase current waveform is equal to or greater than a second predetermined level lower than the first predetermined level, and the frequency adjustment unit may be configured to further lower the switching frequency of the inverter when the judgment unit judges that the distortion of the phase current waveform is equal to or greater than the second predetermined level while the switching frequency is being continued to be lowered (fourth configuration).

[0061] In the control circuit of any of the above first to fourth configurations, the determination unit may be configured (fifth configuration) to include a conversion unit (211) configured to convert the phase current waveform into a frequency spectrum, and to determine whether or not distortion of the phase current waveform is equal to or greater than the first predetermined level based on the frequency spectrum.

[0062] In the control circuit of the fifth configuration, the judgment unit may be configured to judge whether or not the distortion of the phase current waveform is equal to or greater than the first predetermined level based on components of the frequency spectrum that are at least twice the rotational frequency of the motor (sixth configuration).

[0063] In the control circuit of the sixth configuration, the judgment unit may be configured to judge whether or not the distortion of the phase current waveform is equal to or greater than the first predetermined level based on the maximum value of the component of the frequency spectrum that is equal to or greater than twice the rotational frequency of the motor (seventh configuration).

[0064] In the control circuit of any of the above first to fourth configurations, the determination unit may be configured (eighth configuration) to include a waveform comparison unit (212) configured to compare the phase current waveform with a reference sine wave waveform, and to determine whether or not the distortion of the phase current waveform is equal to or greater than the first predetermined level based on the comparison result of the waveform comparison unit.

[0065] The motor drive device (Y1) of the present disclosure has a configuration (ninth configuration) including a control circuit of any one of the first to eighth configurations, a detector (3) configured to detect the phase current waveform, and the inverter.

[0066] A motor system (X1) of the present disclosure has a configuration (tenth configuration) including the motor drive device of the ninth configuration and the motor.

[0067] A control method disclosed herein is a control method for controlling an inverter (1) configured to drive a motor (Z1), and includes the steps of: determining whether or not distortion of a phase current waveform of the motor is equal to or greater than a first predetermined level; and, when it is determined that the distortion of the phase current waveform is equal to or greater than the first predetermined level, lowering a switching frequency of the inverter (eleventh configuration). [Explanation of symbols]

[0068] 1 inverter 2. Control circuit 3 Current detector 21 Judgment section 22 Frequency adjustment unit 211 Conversion Unit 212 Waveform comparison section MHU, MHV, MHW high-side transistors MLU, MLV, MLW low-side transistors X1 Motor System Y1 motor drive unit Z1 motor

Claims

1. 1. A control circuit configured to control an inverter configured to drive a motor, comprising: a determination unit configured to determine whether a distortion of a phase current waveform of the motor is equal to or greater than a first predetermined level; a frequency adjusting unit configured to reduce a switching frequency of the inverter when the determining unit determines that the distortion of the phase current waveform is equal to or greater than the first predetermined level; A control circuit comprising:

2. 2. The control circuit according to claim 1, wherein the frequency adjuster is configured to continue to decrease the switching frequency until the determiner determines that the distortion of the phase current waveform is less than the first predetermined level.

3. 3. The control circuit according to claim 2, wherein the frequency adjuster is configured to increase the switching frequency when the determiner determines that the distortion of the phase current waveform is less than the first predetermined level.

4. the determination unit is configured to also determine whether or not the distortion of the phase current waveform is equal to or greater than a second predetermined level that is lower than the first predetermined level, 3. The control circuit according to claim 2, wherein the frequency adjusting unit is configured to further reduce the switching frequency of the inverter when the determining unit determines that distortion of the phase current waveform is equal to or greater than the second predetermined level while the switching frequency is being continuously reduced.

5. 2. The control circuit according to claim 1, wherein the determination unit includes a conversion unit configured to convert the phase current waveform into a frequency spectrum, and is configured to determine whether distortion of the phase current waveform is equal to or greater than the first predetermined level based on the frequency spectrum.

6. 6. The control circuit according to claim 5, wherein the determination unit is configured to determine whether distortion of the phase current waveform is equal to or greater than the first predetermined level based on components of the frequency spectrum that are equal to or greater than twice the rotational frequency of the motor.

7. 7. The control circuit according to claim 6, wherein the determination unit is configured to determine whether distortion of the phase current waveform is equal to or greater than the first predetermined level based on a maximum value of a component of the frequency spectrum that is equal to or greater than twice the rotational frequency of the motor.

8. 2. The control circuit according to claim 1, wherein the determination unit includes a waveform comparison unit configured to compare the phase current waveform with a reference sinusoidal waveform, and is configured to determine whether distortion of the phase current waveform is equal to or greater than the first predetermined level based on a comparison result of the waveform comparison unit.

9. A motor drive device comprising: the control circuit according to any one of claims 1 to 8; a detector configured to detect the phase current waveforms; and the inverter.

10. A motor system comprising: the motor drive device according to claim 9; and the motor.

11. 1. A control method for controlling an inverter configured to drive a motor, comprising: determining whether a distortion of a phase current waveform of the motor is equal to or greater than a first predetermined level; reducing a switching frequency of the inverter when it is determined that the distortion of the phase current waveform is equal to or greater than the first predetermined level; A control method comprising:

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