Motor control device, motor system, and current detection method

Abstract

In a shunt current detection method, the phase current of the third phase that flows during the first energizing period when the first phase is off and the second and third phases are on is detected. [Solution] A current detection method for detecting the third phase current flowing through a motor driven by an inverter circuit, based on a plurality of PWM signals that form a first energizing period in one cycle in which the first phase is off and the second and third phases are on, and a second energizing period in which the first and second phases are off and the third phase is on, and based on the current change range in which the third phase current changes over a time width from a first timing in the first energizing period to a second timing in the second energizing period, and a second current value detected in the second energizing period by a current detector provided on the DC side of the inverter circuit.

Description

Technical Field

[0001] The present disclosure relates to a motor control device, a motor system, and a current detection method.

Background Art

[0002] Conventionally, a one-shunt current detection method is known that uses one shunt resistor inserted into the DC part of an inverter circuit to detect the currents of U, V, and W phases for controlling a three-phase motor. In this one-shunt current detection method, PWM (Pulse Width Modulation) signals for each phase are generated such that currents can be detected in a period within one cycle in which a first phase is off and a second phase and a third phase are on, and in a period in which the first phase and the second phase are off and the third phase is on (see, for example, Patent Documents 1 and 2).

[0003] On the other hand, a one-shunt current detection method is known in which, within one cycle, a first period in which the signal level of the PWM signal of each phase changes at a timing corresponding to a set duty ratio, and a second period in which the signal level of the PWM signal of each phase changes at different fixed timings from each other are provided. In this one-shunt current detection method, PWM signals for each phase are generated such that currents can be detected within the second period in a period in which a first phase is off and a second phase and a third phase are on, and in a period in which the first phase and the second phase are off and the third phase is on (see, for example, Patent Document 3).

Prior Art Literature

Patent Literature

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problem to be Solved by the Invention

[0005] Conventional single-shunt current detection methods detect the phase current of the first phase flowing during the first energizing period when the first phase is off and the second and third phases are on, and detect the phase current of the third phase flowing during the second energizing period when the first and second phases are off and the third phase is on. However, conventional single-shunt current detection methods cannot detect the phase current of the third phase flowing during the first energizing period when the first phase is off and the second and third phases are on.

[0006] This disclosure provides a motor control device, a motor system, and a current detection method capable of detecting the phase current of the third phase flowing during a first energizing period in a single shunt current detection method, where the first phase is off and the second and third phases are on. [Means for solving the problem]

[0007] A motor control device according to one aspect of this disclosure is An inverter circuit that drives a motor based on multiple PWM signals that form a first energizing period in which the first phase is off and the second and third phases are on, and a second energizing period in which the first and second phases are off and the third phase is on, within one cycle. A current detector provided on the DC side of the inverter circuit, A current detection unit detects a plurality of phase currents flowing through the motor based on a first current value detected by the current detector during the first energizing period and a second current value detected by the current detector during the second energizing period. A generation unit that generates a plurality of PWM signals based on the detected values ​​of a plurality of phase currents, When the phase current of the third phase flowing through the motor is defined as the third phase current, The current detection unit detects the third-phase current flowing during the first energizing period based on the current change range over a time period from the first timing within the first energizing period to the second timing within the second energizing period, and the second current value.

[0008] A motor control device in another aspect of this disclosure is: An inverter circuit that drives a motor based on multiple PWM signals that form a first energizing period in which the first phase is off and the second and third phases are on, and a second energizing period in which the first and second phases are off and the third phase is on, within one cycle. A current detector provided on the DC side of the inverter circuit, A current detection unit detects a plurality of phase currents flowing through the motor based on a first current value detected by the current detector during the first energizing period and a second current value detected by the current detector during the second energizing period. A generation unit that generates a plurality of PWM signals based on the detected values ​​of a plurality of phase currents, When the phase current of the third phase flowing through the motor is defined as the third phase current, The current detection unit detects the third-phase current flowing during the first energizing period based on the rate of change of the third-phase current with respect to the time width from the first timing in the first energizing period to the second timing in the second energizing period, and the second current value.

[0009] A motor system in one aspect of this disclosure is: Motor and, An inverter circuit that drives the motor based on a plurality of PWM signals that form a first energizing period in which the first phase is off and the second and third phases are on, and a second energizing period in which the first and second phases are off and the third phase is on, within one cycle, A current detector provided on the DC side of the inverter circuit, A current detection unit detects a plurality of phase currents flowing through the motor based on a first current value detected by the current detector during the first energizing period and a second current value detected by the current detector during the second energizing period. A generation unit that generates a plurality of PWM signals based on the detected values ​​of a plurality of phase currents, When the phase current of the third phase flowing through the motor is defined as the third phase current, The current detection unit detects the third-phase current flowing during the first energizing period based on the current change range over a time period from the first timing within the first energizing period to the second timing within the second energizing period, and the second current value.

[0010] A motor system in another aspect of this disclosure is: Motor and, An inverter circuit that drives the motor based on a plurality of PWM signals that form a first energizing period in which the first phase is off and the second and third phases are on, and a second energizing period in which the first and second phases are off and the third phase is on, within one cycle, A current detector provided on the DC side of the inverter circuit, A current detection unit detects a plurality of phase currents flowing through the motor based on a first current value detected by the current detector during the first energizing period and a second current value detected by the current detector during the second energizing period. A generation unit that generates a plurality of PWM signals based on the detected values ​​of a plurality of phase currents, When the phase current of the third phase flowing through the motor is defined as the third phase current, The current detection unit detects the third-phase current flowing during the first energizing period based on the rate of change of the third-phase current with respect to the time width from the first timing in the first energizing period to the second timing in the second energizing period, and the second current value.

[0011] A current detection method according to one aspect of this disclosure is: Based on a plurality of PWM signals that form a first energizing period in which the first phase is off and the second and third phases are on, and a second energizing period in which the first and second phases are off and the third phase is on, the phase current of the third phase flowing through the motor driven by the inverter circuit is defined as the third phase current. The third phase current flowing through the first energizing period is detected based on the current change range over a time width from the first timing in the first energizing period to the second timing in the second energizing period, and the second current value detected during the second energizing period by a current detector provided on the DC side of the inverter circuit.

[0012] A current detection method according to another aspect of the present disclosure is: When, based on a plurality of PWM signals that form in one cycle a first energization period in which a first phase is off and a second phase and a third phase are on, and a second energization period in which the first phase and the second phase are off and the third phase is on, the phase current of the third phase flowing in a motor driven by an inverter circuit is defined as a third phase current, the third phase current flowing in the first energization period is detected based on a current change rate of the third phase current with respect to a time width from a first timing within the first energization period to a second timing within the second energization period, and a second current value detected in the second energization period by a current detector provided on a DC side of the inverter circuit. Effects of the Invention

[0013] According to the present disclosure, in a single-shunt current detection method, the phase current of the third phase flowing in the first energization period in which the first phase is off and the second phase and the third phase are on can be detected. Brief Description of the Drawings

[0014] [Figure 1] It is a diagram showing an example configuration of a motor system according to a first embodiment. [Figure 2] It is a diagram for explaining an overview of a phase current detection method performed by a motor control device according to the first embodiment. [Figure 3] It is a diagram showing switch states of each arm when a first current value is detected in a first energization period by the current detector. [Figure 4] It is a diagram showing switch states of each arm when a second current value is detected in a second energization period by the current detector. [Figure 5] It is a timing chart exemplifying phase currents of each phase flowing in the motor during the first energization period and the second energization period. [Figure 6] It is a timing chart for explaining the method of detecting the third phase current flowing in the first energization period. [Figure 7]This is a timing chart used to explain how to measure the current change amplitude or current change rate. [Modes for carrying out the invention]

[0015] Hereinafter, with reference to the drawings, a motor control device, a motor system, and a current detection method according to embodiments of this disclosure will be described in detail.

[0016] Figure 1 is a diagram showing an example configuration of a motor system according to the first embodiment. The motor system 201 shown in Figure 1 controls the rotational operation of the motor 4. The equipment on which the motor system 201 is mounted includes, for example, a copier, a personal computer, a refrigerator, a pump, etc., but is not limited to these. The motor system 201 comprises at least a motor 4 and a motor control device 101.

[0017] Motor 4 has multiple coils. Motor 4 has, for example, a three-phase coil including a U-phase coil, a V-phase coil, and a W-phase coil. A specific example of motor 4 is a three-phase brushless motor. The U-phase coil, V-phase coil, and W-phase coil are connected to each other, for example, by a star connection. The U-phase is an example of the first phase. The V-phase is an example of the second phase. The W-phase is an example of the third phase.

[0018] The motor control device 101 controls the drive of the motor 4 by converting DC to 3-phase AC by controlling multiple 3-phase bridge-connected switching elements to turn on or off according to an energizing pattern that includes a 3-phase PWM signal. The motor control device 101 includes an inverter circuit 23, a current detector 24, a current detection unit 27, a drive circuit 33, and a generation unit 35 to control the motor 4.

[0019] The inverter circuit 23 converts the DC power supplied from the DC power supply 21 into three-phase AC power by switching multiple switching elements, and rotates the rotor of the motor 4 by flowing the three-phase AC drive current through the three-phase coils of the motor 4. The inverter circuit 23 drives the motor 4 based on multiple energization patterns (more specifically, three-phase PWM signals) generated by the generation unit 35.

[0020] The inverter circuit 23 has multiple three-phase bridge-connected arms Up, Vp, Wp, Un, Vn, and Wn. The upper arms Up, Vp, and Wp are high-side switching elements connected to the positive side of the DC power supply 21 via the positive busbar 22a. The lower arms Un, Vn, and Wn are low-side switching elements connected to the negative side (specifically, the ground side) of the DC power supply 21. Each of the multiple arms Up, Vp, Wp, Un, Vn, and Wn is turned on or off according to the corresponding drive signal from the multiple drive signals supplied from the drive circuit 33 based on the PWM signal included in the energization pattern described above. Hereinafter, the multiple arms Up, Vp, Wp, Un, Vn, and Wn may be simply referred to as arms or switching elements unless otherwise specified.

[0021] The connection point between the U-phase upper arm Up and the U-phase lower arm Un is connected to one end of the U-phase coil of motor 4. The connection point between the V-phase upper arm Vp and the V-phase lower arm Vn is connected to one end of the V-phase coil of motor 4. The connection point between the W-phase upper arm Wp and the W-phase lower arm Wn is connected to one end of the W-phase coil of motor 4. The other ends of the U-phase coil, V-phase coil, and W-phase coil are connected to each other.

[0022] Specific examples of arms include N-channel MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) and IGBTs (Insulated Gate Bipolar Transistors). However, arms are not limited to these.

[0023] The current detector 24 is installed on the DC side of the inverter circuit 23 and outputs a detection signal Sd corresponding to the current value of the current flowing on the DC side of the inverter circuit 23. The current detector 24 shown in Figure 1 is connected to the negative bus 22b on the DC side of the inverter circuit 23 and generates a detection signal Sd corresponding to the current value of the current flowing through the negative bus 22b. The current detector 24 is, for example, a current detection element placed on the negative bus 22b, and more specifically, a shunt resistor inserted into the negative bus 22b. A current detection element such as a shunt resistor generates a voltage signal corresponding to the current value of the current flowing through it as a detection signal Sd. The negative bus 22b is an example of a DC line of the inverter circuit 23. The current detector 24 is a device connected in series with the negative bus 22b. Note that the current detector 24 only needs to output a detection signal corresponding to the current value of the current flowing through the negative bus 22b, and other current detection methods such as a magnetic current sensor may also be used.

[0024] The current detection unit 27 detects the phase currents Iu, Iv, and Iw of each phase flowing through the motor 4 using a method that detects multiple phase currents from a single current detector 24 (a so-called single-shunt current detection method). Phase current Iu is an example of the first phase current (first phase current) flowing through the motor and is sometimes referred to as the U phase current. Phase current Iv is an example of the second phase current (second phase current) flowing through the motor and is sometimes referred to as the V phase current. Phase current Iw is an example of the third phase current (third phase current) flowing through the motor and is sometimes referred to as the W phase current.

[0025] The current detection unit 27 detects the phase currents Iu, Iv, and Iw of the U, V, and W phases flowing through the motor 4 by acquiring a detection signal Sd based on multiple energizing patterns (more specifically, three-phase PWM signals) generated by the generation unit 35. More specifically, the current detection unit 27 detects the phase currents Iu, Iv, and Iw by acquiring a detection signal Sd at an acquisition timing synchronized with the multiple energizing patterns (more specifically, three-phase PWM signals) generated by the generation unit 35.

[0026] For example, the current detection unit 27 receives the analog voltage detection signal Sd generated by the current detector 24 into an AD (Analog to Digital) converter at acquisition timings set according to multiple energizing patterns. This AD converter is provided in the current detection unit 27. The current detection unit 27 then performs an AD conversion of the received analog detection signal Sd into a digital detection signal Sd, and digitally processes the resulting digital detection signal Sd to detect the phase currents Iu, Iv, and Iw of the U, V, and W phases of the motor 4. The detected values ​​of the phase currents Iu, Iv, and Iw of each phase detected by the current detection unit 27 are supplied to the generation unit 35.

[0027] The generation unit 35 generates a signal that specifies a pattern for energizing the inverter circuit 23 (the energizing pattern of the inverter circuit 23). The energizing pattern of the inverter circuit 23 can also be rephrased as a pattern for energizing the motor 4 (the energizing pattern of the motor 4). The signal that specifies the energizing pattern of the inverter circuit 23 includes, for example, a three-phase PWM signal for energizing the inverter circuit 23. Based on the detected values ​​of the phase currents Iu, Iv, and Iw of each phase of the motor 4 detected by the current detection unit 27, the generation unit 35 generates a multi-phase (three-phase in this example) PWM signal for energizing the inverter circuit 23.

[0028] The generation unit 35 generates, for example, the energizing pattern of the inverter circuit 23 using vector control. Note that the method for generating the energizing pattern of the inverter circuit 23 is not limited to vector control; it may also be a method that uses VF control or the like to determine the phase voltage of each phase.

[0029] The control device (current detection unit 27 and current generation unit 35) includes electronic circuits such as a CPU (Central Processing Unit), GPU (Graphics Processing Unit), FPGA (Field Programmable Gate Array), or ASIC (Application Specific Integrated Circuit). The control device may also be a computer having memory and a processor. The control device performs the various control operations described in this specification by executing a program such as instruction code stored in memory, or by designing a circuit for a special application.

[0030] The generation unit 35 generates, for example, a three-phase PWM signal, which is a signal that specifies the energizing pattern of the inverter circuit 23. The generation unit 35 includes, for example, a duty cycle setting unit (setting unit 39) and a PWM signal generation unit (signal generation unit 32).

[0031] The setting unit 39 sets the duty cycles Udu, Vdu, and Wdu of the PWM signals for each phase based on the current detection results from the current detection unit 27. For example, the setting unit 39 sets the phase voltage commands Vu for each phase, which are generated by known vector control based on the detected phase currents Iu, Iv, and Iw from the current detection unit 27. * ,Vv * VW * Based on this, the duty cycles Udu, Vdu, and Wdu for each phase are derived.

[0032] The signal generation unit 32 generates PWM signals P, U, and W for each phase based on the duty cycles Udu, Vdu, and Wdu of each phase set by the setting unit 39. For example, the signal generation unit 32 generates PWM signals P, U, and W for each phase based on the duty cycles Udu, Vdu, and Wdu of each phase set by the setting unit 39 and one or more carriers. A carrier is a carrier wave signal whose level increases and decreases periodically. The signal generation unit 32 generates three-phase PWM signals U, V, and W based on the comparison result between the threshold values ​​of each phase corresponding to the duty cycles Udu, Vdu, and Wdu of each phase and one or more carriers.

[0033] PWM signal U includes PWM signal UH for driving the U-phase upper arm Up and PWM signal UL for driving the U-phase lower arm Un. PWM signal V includes PWM signal VH for driving the V-phase upper arm Vp and PWM signal VL for driving the V-phase lower arm Vn. PWM signal W includes PWM signal WH for driving the W-phase upper arm Wp and PWM signal WL for driving the W-phase lower arm Wn.

[0034] The generation unit 35 outputs the PWM signals U, V, and W for each phase generated by the signal generation unit 32 to the drive circuit 33.

[0035] The drive circuit 33 outputs drive signals that switch the six arms Up, Vp, Wp, Un, Vn, and Wn included in the inverter circuit 23, according to the energization pattern that includes the PWM signals U, V, and W for each phase provided by the generation unit 35. As a result, a three-phase AC drive current is supplied to the motor 4, causing the rotor of the motor 4 to rotate.

[0036] Figure 2 is a diagram illustrating the overview of the phase current detection method by the motor control device 101 according to the first embodiment.

[0037] The PWM signal U is a PWM signal used to drive the two switching elements that make up the upper and lower arms of the U-phase. When the PWM signal U is at a low level, the switching element of the lower arm of the U-phase turns on (the switching element of the upper arm of the U-phase turns off), and when the PWM signal U is at a high level, the switching element of the lower arm of the U-phase turns off (the switching element of the upper arm of the U-phase turns on). In response to changes in the level of the PWM signal U, the two switching elements that make up the upper and lower arms of the U-phase operate complementary on / off operations.

[0038] The PWM signal V is used to drive the two switching elements that make up the upper and lower arms of the V phase. When the PWM signal V is low level, the switching element of the lower arm of the V phase turns on (the switching element of the upper arm of the V phase turns off), and when the PWM signal V is high level, the switching element of the lower arm of the V phase turns off (the switching element of the upper arm of the V phase turns on). In response to changes in the level of the PWM signal V, the two switching elements that make up the upper and lower arms of the V phase operate complementary on / off operations.

[0039] The PWM signal W is used to drive the two switching elements that make up the upper and lower arms of the W phase. When the PWM signal W is low level, the switching element of the lower arm of the W phase turns on (the switching element of the upper arm of the W phase turns off), and when the PWM signal W is high level, the switching element of the lower arm of the W phase turns off (the switching element of the upper arm of the W phase turns on). In response to changes in the level of the PWM signal W, the two switching elements that make up the upper and lower arms of the W phase operate complementary on / off operations.

[0040] The cycle T of the three-phase PWM signals U, V, and W includes a first period A and the remaining second period B. The first period A, from timing t0 to timing t4, is the section for adjusting the duty cycle of each of the three-phase PWM signals U, V, and W. The second period B, from timing t4 to timing t8, is the section for detecting the phase currents Iu, Iv, and Iw of each phase flowing through the motor 4.

[0041] The generation unit 35 generates PWM signals for each phase such that the signal levels of the PWM signals for each phase switch at timings corresponding to the duty cycle set for each during the first period A, and switch at fixed timings that differ from each other during the second period B. The current detection unit 27 acquires a first current value I1 detected by the current detector 24 during the first energizing period Tc1 within the second period B, and a second current value I2 detected by the current detector 24 during the second energizing period Tc2 within the second period B, for each period T. Based on the acquired first current value I1 and second current value I2, the current detection unit 27 detects multiple phase currents Iu, Iv, and Iw flowing through the motor 4 during the period T in which those first current values ​​I1 and second current values ​​were detected.

[0042] During the first period A, the timings t1, t2, and t3 at which the signal levels of the PWM signals U, V, and W switch vary according to the corresponding duty cycle among the multiple duty cycles Udu, Vdu, and Wdu set by the setting unit 39.

[0043] On the other hand, in the second period B, the timings t5, t6, and t7 at which the signal levels of the PWM signals U, V, and W switch are fixed regardless of the multiple duty cycles Udu, Vdu, and Wdu set by the setting unit 39. In other words, the order in which the signal levels of the PWM signals U, V, and W switch in the second period B is fixed. For example, as shown in Figure 2, in the second period B, the signal levels of the PWM signals switch in the order of U-phase, V-phase, and W-phase, and this order does not need to be changed in any period T during drive control after motor 4 is started, unless a predetermined condition is met. Note that the order in which the signal levels of the PWM signals U, V, and W for each phase switch is not limited to the above example.

[0044] In the second period B, the current detection unit 27 acquires a first current value I1 detected by the current detector 24 at a fixed first timing tm1, which occurs between the change in the signal level of the PWM signal U and the change in the signal level of the PWM signal V. The first timing tm1 may be the same timing in each period T. In the second period B, the current detection unit 27 acquires a second current value I2 detected by the current detector 24 at a fixed second timing tm2, which occurs between the change in the signal level of the PWM signal V and the change in the signal level of the PWM signal W. The second timing tm2 may be the same timing in each period T.

[0045] In the example shown in Figure 2, the fixed first timing tm1 is a point in time included in the first energizing period Tc1 between the timing t5 when the signal level of the U-phase PWM signal U switches and the timing t6 when the signal level of the V-phase PWM signal V switches. The fixed second timing tm2 is a point in time included in the second energizing period Tc2 between the timing t6 when the signal level of the V-phase PWM signal V switches and the timing t7 when the signal level of the W-phase PWM signal W switches.

[0046] For example, the current detection unit 27 acquires a first current value I1 detected by the current detector 24 at a first timing tm1, which is a predetermined time width t1a elapsed from the timing t5 when the PWM signal U transitions from on to off. The time width t1a may be a fixed time with the same length in each period T. The current detection unit 27 acquires a second current value I2 detected by the current detector 24 at a second timing tm2, which is a predetermined time width t2a elapsed from the timing t6 when the PWM signal V transitions from on to off. The time width t2a may be a fixed time with the same length in each period T.

[0047] Figure 3 shows the switch state of each arm when the current detector 24 detects the first current value I1 during the first energizing period Tc1. During the first energizing period Tc1, the upper arm Up is off and the upper arms Vp and Wp are on (U phase is off and V and W phases are on). Therefore, the first current value I1 acquired by the current detection unit 27 during the first energizing period Tc1 represents the current value of the U phase current Iu. Thus, the current detection unit 27 can detect the first current value I1 acquired during the first energizing period Tc1 as the current value of the U phase current Iu.

[0048] Figure 4 shows the switch state of each arm when the current detector 24 detects the second current value I2 during the second energizing period Tc2. During the second energizing period Tc2, the upper arms Up and Vp are off and the upper arm Wp is on (U and V phases are off and W phase is on). Therefore, the second current value I2 obtained by the current detection unit 27 during the second energizing period Tc2 represents the sum of the current value of the phase current Iu of the U phase and the current value of the phase current Iv of the V phase.

[0049] The phase currents Iu, Iv, and Iw of the U, V, and W phases are related by the equation "Iu + Iv + Iw = 0". In other words, the relationship is "Iw = -(Iu + Iv)".

[0050] Based on this relationship, the current detection unit 27 can calculate (detect) the current value of the W-phase phase current Iw from the second current value I2 (=-(Iu+Iv)) acquired during the second energizing period Tc2. Then, based on this relationship, the current detection unit 27 can calculate (detect) the current value of the V-phase phase current Iv from the current value of the U-phase phase current Iu detected by the first current value I1 and the current value of the W-phase phase current Iw detected by the second current value I2.

[0051] In this way, the current detection unit 27 can detect the current values ​​of the phase currents Iu, Iv, and Iw flowing through the motor 4 based on the first current value I1 detected by the current detector 24 during the first energizing period Tc1 and the second current value I2 detected by the current detector 24 during the second energizing period Tc2.

[0052] Figure 5 is a timing chart illustrating the phase currents Iu, Iv, and Iw of each phase flowing through the motor 4 during the second period B, which includes the first energizing period Tc1 and the second energizing period Tc2.

[0053] The generation unit 35 generates multi-phase PWM signals U, V, and W, which form a first energizing period Tc1 in which the U phase is off and the V and W phases are on, and a second energizing period Tc2 in which the U and V phases are off and the W phase is on, within one period T. In this example, the first energizing period Tc1 and the second energizing period Tc2 are formed within the second period B within one period T.

[0054] The first energized period Tc1, in which the U phase is off and the V and W phases are on, refers to the period when the upper arm Up and lower arms Vn and Wn are off, and the lower arm Un and upper arms Vp and Wp are on. The second energized period Tc2, in which the U and V phases are off and the W phase is on, refers to the period when the upper arm Up and Vp and lower arm Wn are off, and the lower arm Un and Vn and upper arm Wp are on.

[0055] The current detection unit 27 detects the current value of the U-phase phase current Iu flowing during the first energizing period Tc1 based on the first current value I1 (= +Iu) detected by the current detector 24 during the first energizing period Tc1 using a single-shunt current detection method. Then, the current detection unit 27 calculates (detects) the current value of the W-phase phase current Iw flowing during the second energizing period Tc2 based on the second current value I2 (= -(Iu + Iv)) detected by the current detector 24 during the second energizing period Tc2 using a single-shunt current detection method.

[0056] However, the current value of the phase current Iw detected based solely on the second current value I2 is the current value of the phase current Iw flowing during the second energizing period Tc2, and not the current value of the phase current Iw flowing during the first energizing period Tc1. The phase current Iw actually flowing through the motor 4 rises or falls as time elapses from the first timing tm1 in the first energizing period Tc1 to the second timing tm2 in the second energizing period Tc2. In the example shown in Figure 5, the phase current Iw rises by a current change amount ΔIwa. Thus, when detecting the phase current Iw based solely on the second current value I2 detected during the second energizing period Tc2, the detection error (current change amount ΔIwa) caused by the detection delay between the first timing tm1 and the second timing tm2 is always included in the detected value of the phase current Iw.

[0057] The current value of the phase current Iw detected based solely on the second current value I2 (including the current change range ΔIwa) is a detection value at a different timing than the current value of the phase current Iu detected based on the first current value I1. When phase currents Iw and Iu are detection values ​​at different timings, the variation in the error of the detection value of the phase current Iv derived from phase currents Iw and Iu tends to be large. Furthermore, if the current change range ΔIwa is included in the detection value of phase current Iw, this variation in error may become even larger. If the phase currents Iu and Iw can be detected almost simultaneously using the 1-shunt current detection method, then, similar to the 3-shunt current detection method, the phase currents Iu, Iw of two phases or Iu, Iv, Iw of three phases can be detected almost simultaneously. This makes it possible to suppress the variation in the detection error of the phase currents Iu, Iw of two phases or Iu, Iv, Iw of three phases.

[0058] In the first embodiment of this disclosure, the current detection unit 27 has the function of detecting the phase current Iw that flows during the first energizing period Tc1, which is the same as the detection period of the phase current Iu, in a single-shunt current detection method. As a result, the phase current Iu and the phase current Iw are detected almost simultaneously. This function will be described in detail below.

[0059] <Method for measuring current change amplitude ΔIw or current change rate a>

[0060] Figure 7 is a timing chart illustrating the method for measuring the current change range ΔIw or current change rate a. The motor control device 101 measures the current change range ΔIw or current change rate a, which is used to detect the phase current Iw (specifically, the current value Iw1 at the first timing tm1) flowing during the first energizing period Tc1, in advance before or at the time of starting the motor 4 with the controlled variable at zero.

[0061] Here, the state where the controlled variable is zero refers to the state where the current is GND (0[A]) at timing t5 in Figures 5, 6, or 7. Timing t5 is the timing at which the first energizing period Tc1 begins.

[0062] During the first energizing period Tc1, when the U phase is off and the V and W phases are on, the phase current Iw flowing through the W phase coil of motor 4 changes at the same rate of change as the phase current Iv flowing through the V phase coil of motor 4, as can be understood from the current path shown in Figure 3. During the second energizing period Tc2, when the U and V phases are off and the W phase is on, the phase current Iw flowing through the W phase coil of motor 4 changes at twice the rate of change of the phase current Iv flowing through the V phase coil of motor 4, as can be understood from the current path shown in Figure 4.

[0063] Therefore, in Figure 7, assuming that the phase current Iw changes according to a linear first-order equation, the first current change rate a1 of the phase current Iw in the first energizing period Tc1 is half of the second current change rate a2 of the phase current Iw in the second energizing period Tc2 which is continuous with the first energizing period Tc1. In other words, the second current change rate a2 of the phase current Iw in the second energizing period Tc2 is twice the first current change rate a1 of the phase current Iw in the first energizing period Tc1 immediately preceding the second energizing period Tc2.

[0064] Utilizing this current change characteristic of the phase current Iw, the generation unit 35 shifts the phase of the V-phase PWM signal V to a phase that overlaps with the U-phase PWM signal U in order to measure the current change width ΔIw or the current change rate a. At this time, the duty cycle of all PWM signals U, V, and W is the same 50% before and after the shift of the PWM signal V. By shifting the phase of the PWM signal V until it overlaps with the phase of the PWM signal U, the second energized period Tc2, in which the U-phase and V-phase are off and the W-phase is on, becomes twice the length of the PWM signal V before the shift.

[0065] The current detection unit 27 acquires the phase current Iw detected by the current detector 24 at the same two timings as the first timing tm1 and second timing tm2 before the shift of the PWM signal V, while the phase of the PWM signal V is shifted until it overlaps with the phase of the PWM signal U. As a result, the current detection unit 27 can detect the current value Iw1 of the phase current Iw flowing through the W-phase coil of the motor 4 at the same timing as the first timing tm1, and the current value Iw2 of the phase current Iw flowing through the W-phase coil of the motor 4 at the same timing as the second timing tm2.

[0066] The current detection unit 27 can measure the current change width ΔIw of the phase current Iw over a time width Δt from the first timing tm1 to the second timing tm2 by determining the difference between the two current values ​​(current value Iw1 and current value Iw2) detected while the phase of the PWM signal V is shifted. The current detection unit 27 stores the measured current change width ΔIw in the memory 40.

[0067] Alternatively, the current detection unit 27 can measure the rate of change a of the phase current Iw with respect to the time width Δt by dividing the difference between the two current values ​​(current value Iw1 and current value Iw2) detected with the phase of the PWM signal V shifted by the time width Δt. The current detection unit 27 stores the measured rate of change a in the memory 40. Since the measured rate of change a is equal to the second rate of change a2, the current detection unit 27 may store the measured rate of change a in the memory 40 as the second rate of change a2. Since the measured rate of change a is twice the first rate of change a1, the current detection unit 27 may store half of the measured rate of change a in the memory 40 as the first rate of change a1.

[0068] The current detection unit 27 calculates the first current change width ΔIw1 by multiplying the first current change rate a1 stored in the memory 40 by the first time width t1b (Figure 7). The current detection unit 27 calculates the second current change width ΔIw2 by multiplying the second current change rate a2 stored in the memory 40 by the second time width t2a (Figure 7). The current detection unit 27 can calculate the current change width ΔIw by adding the first current change width ΔIw1 and the second current change width ΔIw2. The current detection unit 27 stores the calculated current change width ΔIw in the memory 40.

[0069] Therefore, the current detection unit 27 can calculate (detect) the current value Iw1 (=I2-ΔIw) of the phase current Iw flowing during the first energizing period Tc1 by subtracting the current change range ΔIw from the second current value I2 detected by the current detector 24 during the second energizing period Tc2. Then, the current detection unit 27 can calculate (detect) the current value (=-I1-Iw1) of the phase current Iv flowing during the first energizing period Tc1 based on the first current value I1 (=Iu) detected by the current detector 24 during the first energizing period Tc1 and the calculated (detected) current value Iw1.

[0070] Figure 6 is a timing chart illustrating the method for detecting the third-phase current (in this example, the phase current Iw) flowing during the first energizing period Tc1. The motor control device 101 detects the phase current Iw (more specifically, the current value Iw1 at the first timing tm1) flowing during the first energizing period Tc1 using the current change width ΔIwb or current change rate b measured in advance as described above.

[0071] <First detection method> In Figure 6, the current detection unit 27 detects the phase current Iw flowing during the first energizing period Tc1 based on the current change width ΔIwb, which is the current change width ΔIwb over a time width Δt, and the second current value I2 detected by the current detector 24 during the second energizing period Tc2, in the first detection method.

[0072] The time width Δt corresponds to the time length from the first timing tm1 in the first energizing period Tc1 to the second timing tm2 in the second energizing period Tc2. The current value Iwb1 corresponds to the current value of the phase current Iw flowing at the first timing tm1 in the first energizing period Tc1. The current value Iwb2 corresponds to the current value of the phase current Iw flowing at the second timing tm2 in the second energizing period Tc2, and is equal to the second current value I2 detected by the current detector 24 during the second energizing period Tc2. The difference between the current value Iwb1 and the current value Iwb2 corresponds to the current change width ΔIwb, which is the width by which the phase current Iw changes over the time width Δt (ΔIwb = |Iwb2 - Iwb1|).

[0073] Since there is such a correlation between the current value Iwb1, the current value Iwb2 (second current value I2), and the current change range ΔIwb, if the current change range ΔIwb and the second current value I2 are determined, the current value Iwb1 is also determined. In accordance with this correlation, the current detection unit 27 detects the current value Iwb1 of the phase current Iw flowing during the first energizing period Tc1 based on the current change range ΔIwb, which is the current change range in which the phase current Iw changes over a time width Δt, and the second current value I2 detected during the second energizing period Tc2. As a result, the current change range ΔIwb caused by the detection delay is removed from the detected value of the current value Iwb2 of the phase current Iw.

[0074] Thus, according to the first detection method, the current detection unit 27 has the function of detecting the phase current Iw that flows during the first energizing period Tc1, which is the same as the detection period of the phase current Iu, in the one-shunt current detection method, so that the phase current Iu and the phase current Iw can be detected almost simultaneously. The current detection unit 27 can then use the relationship "Iu + Iv + Iw = 0" to detect the phase current Iv that flows during the first energizing period Tc1 based on the detected value of the phase current Iu that flows during the first energizing period Tc1 and the detected value of the phase current Iw that flows during the first energizing period Tc1. As a result, the variation in the error of the detected value of the phase current Iw and the phase current Iv derived from the phase current Iu is suppressed. As the variation in the detection error of two-phase phase currents Iu, Iw or three-phase phase currents Iu, Iv, Iw is suppressed, for example, the speed unevenness or operating noise of the motor 4 is reduced. The effects of these detection errors become greater as the current values ​​of the phase currents Iu, Iv, and Iw decrease. Therefore, the impact on the behavior of motor 4 is reduced, especially when the current values ​​of the phase currents Iu, Iv, and Iw are below a predetermined value (for example, when motor 4 is started).

[0075] The motor control device 101 may include a memory 40 (Figure 1) for storing the current change width ΔIwb. The current detection unit 27 may detect the current value Iwb1 of the phase current Iw flowing during the first energizing period Tc1 based on the current change width ΔIwb stored in the memory 40 and the second current value I2 detected during the second energizing period Tc2.

[0076] The current change range ΔIwb may be data measured when the motor 4 is started, data measured periodically during drive control after the motor 4 is started, or data measured in advance before the motor 4 is started (for example, before shipment). The measured current change range ΔIwb is stored in memory 40.

[0077] Memory 40 is, for example, non-volatile memory. If the data to be stored is for temporary use, memory 40 may also be RAM (Random Access Memory).

[0078] Figure 6 illustrates a case where the phase current Iw increases from the first energizing period Tc1 to the second energizing period Tc2. In this case, the current detection unit 27 may detect the current value Iwb1 of the phase current Iw flowing during the first energizing period Tc1 by subtracting the current change range ΔIwb from the second current value I2 detected by the current detector 24 during the second energizing period Tc2 (Iwb1 = I2 - ΔIwb). Although not specifically shown, there is a case where the phase current Iw decreases from the first energizing period Tc1 to the second energizing period Tc2. In this case, the current detection unit 27 may detect the current value Iwb1 of the phase current Iw flowing during the first energizing period Tc1 by adding the current change range ΔIwb to the second current value I2 detected by the current detector 24 during the second energizing period Tc2 (Iwb1 = I2 + ΔIwb).

[0079] The current detection unit 27 may derive (detect) the current value Iwb1 corresponding to the current change range ΔIwb and the second current value I2 based on a correlation rule (e.g., a map or calculation formula) between the current value Iwb1, the current value Iwb2 (second current value I2), and the current change range ΔIwb.

[0080] The current detection unit 27 may derive the current change width ΔIwb based on the current change rate b of the phase current Iw. For example, the current detection unit 27 calculates the current change width ΔIwb by multiplying the time width Δt by the current change rate b.

[0081] The current change rate b may be data pre-stored in memory 40. The current change rate b may be data measured when motor 4 is started, data measured periodically during drive control after motor 4 is started, or data measured before motor 4 is started (for example, before shipment). The measured current change rate b is stored in memory 40.

[0082] The rate of change of current b corresponds to the rate of change of the phase current Iw with respect to the time width Δt from the first timing tm1 in the first energizing period Tc1 to the second timing tm2 in the second energizing period Tc2. The rate of change of current b of the phase current Iw may also be expressed as the slope of the phase current Iw. The change in phase current Iw between the first timing tm1 and the second timing tm2 can be approximated by a linear first-order equation, but it may also be approximated by a higher-order equation of second order or higher. The rate of change of current b corresponds to the value obtained by dividing the difference between the current value Iwb2 and the current value Iwb1 by the time width Δt (a = (Iwb2 - Iwb1) / Δt).

[0083] The third timing tm3 corresponds to the boundary timing t6 between the first energization period Tc1 and the second energization period Tc2. The first time interval t1b corresponds to the period from the first timing tm1 to the third timing tm3, and is a fixed time with the same length for each period T. The second time interval t2a corresponds to the period from the third timing tm3 to the second timing tm2, and is a fixed time with the same length for each period T. Time interval t1a corresponds to the period from timing t5 to the first timing tm1, and is a fixed time with the same length for each period T. Time interval t2b corresponds to the period from the second timing tm2 to timing t7, and is a fixed time with the same length for each period T.

[0084] The current detection unit 27 may calculate the above-mentioned current change width ΔIwb by adding a first current change width ΔIwb1, in which the phase current Iw changes over a first time width t1b, and a second current change width ΔIwb2, in which the phase current Iw changes over a second time width t2a.

[0085] The first current change range ΔIwb1 and the second current change range ΔIwb2 may be data pre-stored in the memory 40. The first current change range ΔIwb1 and the second current change range ΔIwb2 may be data measured when the motor 4 is started, data measured periodically during drive control after the motor 4 is started, or data measured in advance before the motor 4 is started (for example, before shipment). The measured first current change range ΔIwb1 and the measured second current change range ΔIwb2 are stored in the memory 40.

[0086] The current detection unit 27 may derive a first current change width ΔIwb1 based on a first current change rate b1 of the phase current Iw with respect to a first time width t1b, or it may derive a second current change width ΔIwb2 based on a second current change rate b2 of the phase current Iw with respect to a second time width t2a. For example, the current detection unit 27 calculates the first current change width ΔIwb1 by multiplying the first time width t1b by the first current change rate b1. For example, the current detection unit 27 calculates the second current change width ΔIwb2 by multiplying the second time width t2a by the second current change rate b2.

[0087] The first current change rate b1 and the second current change rate b2 may be data pre-stored in memory 40. The first current change rate b1 and the second current change rate b2 may be data measured when the motor 4 is started, data measured periodically during drive control after the motor 4 is started, or data measured in advance before the motor 4 is started (for example, before shipment). The measured first current change rate b1 and the measured second current change rate b2 are stored in memory 40.

[0088] <Second detection method> In Figure 6, the current detection unit 27 detects the phase current Iw flowing during the first energizing period Tc1 based on the current change rate b of the phase current Iw with respect to the time width Δt and the second current value I2 detected by the current detector 24 during the second energizing period Tc2. Explanations of the same aspects in the second detection method as in the first detection method are omitted by referring to the explanation above.

[0089] The current rate of change b corresponds to the value obtained by dividing the difference between the current value Iw2 and the current value Iw1 by the time width Δt (b = (Iwb2 - Iwb1) / Δt). Since such a correlation exists between the current value Iwb1, the current value Iwb2 (second current value I2), and the current rate of change b, if the current rate of change b and the second current value I2 with respect to the time width Δt are determined, the current value Iwb1 is also determined. In accordance with this correlation, the current detection unit 27 detects the current value Iwb1 of the phase current Iw flowing during the first energizing period Tc1 based on the current rate of change b of the phase current Iw with respect to the time width Δt and the second current value I2 detected during the second energizing period Tc2. As a result, the current change width ΔIwb caused by the detection delay is removed from the detected value of the current value Iwb2 of the phase current Iw.

[0090] Thus, according to the second detection method, the current detection unit 27 has the function of detecting the phase current Iw that flows during the first energizing period Tc1, which is the same as the detection period of the phase current Iu, in the one-shunt current detection method. Therefore, the phase current Iu and the phase current Iw can be detected almost simultaneously. In other words, the same effects as described above as in the first detection method can be obtained.

[0091] The motor control device 101 may include a memory 40 (Figure 1) for storing the current change rate b. The current detection unit 27 may detect the current value Iwb1 of the phase current Iw flowing during the first energizing period Tc1 based on the current change rate b stored in the memory 40 and the second current value I2 detected during the second energizing period Tc2.

[0092] The current detection unit 27 may derive (detect) the current value Iwb1 corresponding to the current rate of change b and the second current value I2 based on a correlation rule (e.g., a map or calculation formula) between the current value Iwb1, the current value Iwb2 (second current value I2), and the current rate of change b.

[0093] As described above, embodiments have been explained, but these embodiments are presented as examples only, and the present invention is not limited by these embodiments. The above embodiments can be implemented in various other forms, and various combinations, omissions, substitutions, and modifications are possible without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents.

[0094] For example, in the embodiments described above, the U phase, V phase, and W phase were explained as examples of the first phase, second phase, and third phase, respectively, but their corresponding relationships may be interchanged. [Explanation of symbols]

[0095] 4 motors 21 DC power supply 22a Positive side bus bar 22b Negative bus bar 23 Inverter Circuit 24 Current detector 27 Current detection unit 33 Drive Circuit 35 Generation part 40 memory 101 Motor control device 201 Motor System Up, Vp, Wp, Un, Vn, Wn Arm

Claims

1. An inverter circuit that drives a motor based on multiple PWM signals that form a first energizing period in which the first phase is off and the second and third phases are on, and a second energizing period in which the first and second phases are off and the third phase is on, within one cycle. A current detector provided on the DC side of the inverter circuit, A current detection unit detects a plurality of phase currents flowing through the motor based on a first current value detected by the current detector during the first energizing period and a second current value detected by the current detector during the second energizing period. The system comprises a generation unit that generates a plurality of PWM signals based on the detected values ​​of a plurality of phase currents, When the phase current of the third phase flowing through the motor is defined as the third phase current, The motor control device includes a current detection unit which detects the third-phase current flowing during the first energizing period based on the current change range over a time period from the first timing within the first energizing period to the second timing within the second energizing period, and the second current value.

2. When the boundary timing between the first energizing period and the second energizing period is defined as the third timing, The motor control device according to claim 1, wherein the current detection unit calculates the current change width by adding a first current change width, which is the change in the third phase current over a first time interval from the first timing to the third timing, and a second current change width, which is the change in the third phase current over a second time interval from the third timing to the second timing.

3. The motor control device according to claim 2, wherein the current detection unit derives the first current change width based on the first current change rate of the third phase current with respect to the first time width, and derives the second current change width based on the second current change rate of the third phase current with respect to the second time width.

4. The motor control device according to claim 1, wherein the current detection unit derives the current change range based on the rate of change of the third phase current.

5. The system includes a memory for storing the current change range, The motor control device according to claim 1, wherein the current detection unit detects the third phase current flowing during the first energizing period based on the current change range stored in the memory and the second current value.

6. The motor control device according to claim 5, wherein the current change width is measured while the phase of the second phase PWM signal is shifted until it overlaps with the phase of the first phase PWM signal, and the measured current change width is stored in the memory.

7. An inverter circuit that drives a motor based on multiple PWM signals that form a first energizing period in which the first phase is off and the second and third phases are on, and a second energizing period in which the first and second phases are off and the third phase is on, within one cycle. A current detector provided on the DC side of the inverter circuit, A current detection unit detects a plurality of phase currents flowing through the motor based on a first current value detected by the current detector during the first energizing period and a second current value detected by the current detector during the second energizing period. The system comprises a generation unit that generates a plurality of PWM signals based on the detected values ​​of a plurality of phase currents, When the phase current of the third phase flowing through the motor is defined as the third phase current, The motor control device includes a current detection unit which detects the third-phase current flowing during the first energizing period based on the rate of change of the third-phase current with respect to the time width from the first timing in the first energizing period to the second timing in the second energizing period, and the second current value.

8. When the boundary timing between the first energizing period and the second energizing period is defined as the third timing, The motor control device according to claim 7, wherein the current detection unit detects the third phase current flowing during the first energizing period based on a first current change rate of the third phase current with respect to a first time width from the first timing to the third timing, a second current change rate of the third phase current with respect to a second time width from the third timing to the second timing, and the second current value.

9. The motor control device according to claim 8, wherein the current detection unit derives a first current change width in which the third phase current changes over a first time period based on the first current change rate, derives a second current change width in which the third phase current changes over a second time period based on the second current change rate, calculates a current change width in which the third phase current changes over a time period from the first timing to the second timing by adding the first current change width and the second current change width, and detects the third phase current flowing during the first energizing period based on the current change width and the second current value.

10. The system includes a memory for storing the rate of change of current, The motor control device according to claim 7, wherein the current detection unit detects the third-phase current flowing during the first energizing period based on the current change rate stored in the memory and the second current value.

11. The motor control device according to claim 10, wherein the current change rate is measured while the phase of the second phase PWM signal is shifted until it overlaps with the phase of the first phase PWM signal, and the measured current change rate is stored in the memory.

12. The motor control device according to any one of claims 3, 8, or 9, wherein the first rate of change of current is half of the second rate of change of current.

13. The motor control device according to any one of claims 1 to 6, 9, wherein the current detection unit detects the third phase current flowing during the first energizing period by subtracting the current change range from the second current value, or by adding the current change range to the second current value.

14. When the phase current of the second phase flowing through the motor is defined as the second phase current, The motor control device according to any one of claims 1 to 11, wherein the current detection unit detects the second phase current flowing during the first energizing period based on the first current value and the detected value of the third phase current flowing during the first energizing period.

15. The aforementioned cycle includes a first period and a second period. The signal levels of the multiple PWM signals switch at timings corresponding to a set duty cycle during the first period, and switch at different fixed timings during the second period. The motor control device according to any one of claims 1 to 11, wherein the second period includes the first energizing period and the second energizing period.

16. Motor and, An inverter circuit that drives the motor based on a plurality of PWM signals that form a first energizing period in which the first phase is off and the second and third phases are on, and a second energizing period in which the first and second phases are off and the third phase is on, within one cycle, A current detector provided on the DC side of the inverter circuit, A current detection unit detects a plurality of phase currents flowing through the motor based on a first current value detected by the current detector during the first energizing period and a second current value detected by the current detector during the second energizing period. The system comprises a generation unit that generates a plurality of PWM signals based on the detected values ​​of a plurality of phase currents, When the phase current of the third phase flowing through the motor is defined as the third phase current, The motor system includes a current detection unit that detects the third-phase current flowing during the first energizing period based on the current change range over a time period from the first timing within the first energizing period to the second timing within the second energizing period, and the second current value.

17. Motor and, An inverter circuit that drives the motor based on a plurality of PWM signals that form a first energizing period in which the first phase is off and the second and third phases are on, and a second energizing period in which the first and second phases are off and the third phase is on, within one cycle, A current detector provided on the DC side of the inverter circuit, A current detection unit detects a plurality of phase currents flowing through the motor based on a first current value detected by the current detector during the first energizing period and a second current value detected by the current detector during the second energizing period. The system comprises a generation unit that generates a plurality of PWM signals based on the detected values ​​of a plurality of phase currents, When the phase current of the third phase flowing through the motor is defined as the third phase current, The motor system includes a current detection unit that detects the third-phase current flowing during the first energizing period based on the rate of change of the third-phase current with respect to the time width from the first timing in the first energizing period to the second timing in the second energizing period, and the second current value.

18. A current detection method for detecting the third phase current flowing through a motor driven by an inverter circuit, based on a plurality of PWM signals that form a cycle consisting of a first energizing period in which the first phase is off and the second and third phases are on, and a second energizing period in which the first and second phases are off and the third phase is on, wherein the phase current of the third phase flowing through the motor driven by the inverter circuit is defined as the third phase current, and the method for detecting the third phase current flowing through the first energizing period is based on the current change range in which the third phase current changes over a time width from a first timing in the first energizing period to a second timing in the second energizing period, and a second current value detected during the second energizing period by a current detector provided on the DC side of the inverter circuit.

19. A current detection method for detecting the third phase current flowing through a motor driven by an inverter circuit, based on a plurality of PWM signals that form a first energizing period in one cycle in which the first phase is off and the second and third phases are on, and a second energizing period in which the first and second phases are off and the third phase is on, wherein the phase current of the third phase flowing through the motor driven by the inverter circuit is defined as the third phase current, and the current detection method for detecting the third phase current flowing through the first energizing period based on the rate of change of the third phase current with respect to the time width from the first timing in the first energizing period to the second timing in the second energizing period, and a second current value detected during the second energizing period by a current detector provided on the DC side of the inverter circuit.

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