Motor control device

Abstract

A motor control device controls an alternating-current motor by sensorless control without using a rotor position detector. The motor control device includes an inverter that converts direct current into alternating current based on a pulse width modulation signal; a multilayer printed board having a wiring pattern inserted into a current path connecting the inverter and a winding of the alternating-current motor in an inner layer; a plurality of chip inductors mounted on a main surface of the multilayer printed board so that a winding direction faces a prescribed direction intersecting the wiring pattern and opposes the wiring pattern, the plurality of chip inductors being connected in series to form a series circuit having a midpoint connected to a reference potential; load resistors respectively connected between the midpoint of the series circuit and both ends of the series circuit; a differential amplification circuit having a pair of input terminals connected to the both ends of the series circuit; and a control unit that estimates a position of a rotor of the alternating-current motor using an output of the differential amplification circuit and generates the pulse width modulation signal supplied to the inverter in accordance with the estimated position of the rotor.

Description

[0001] Cross-references to related applications

[0002] This application claims priority based on Japanese Patent Application No. 2020-196802 filed with the Japan Patent Office on November 27, 2020, the contents of which are incorporated herein by reference. Technical Field

[0003] This invention relates to a motor control device for controlling an AC motor by sensorless control without using a rotor position detector. Background Technology

[0004] An AC motor is an electric motor designed to operate by accepting an alternating current supply. This includes brushless DC motors, induction motors, stepper motors, and so on. In short, any motor other than one that accepts a direct current supply and uses rectifiers to change the direction of the winding current is included in the category of AC motors.

[0005] A typical motor control device for an AC motor includes an inverter that converts DC to AC and uses this inverter to supply AC current to the motor. To properly control the inverter, information about the rotor position is required. Therefore, the output of a rotor position detector, which detects the rotor's rotational position, is used to control the inverter.

[0006] As an alternative to using a rotor position detector, a method is known that estimates the rotor position and controls the inverter to drive the AC motor based on the estimated rotor position. This control method is called "sensorless control," or simply "sensorless control." By eliminating the rotor position detector, there is no need to consider the installation accuracy of the rotor position detector or the wiring associated with it. Moreover, sensorless control has the advantage of being applicable to motors where rotor position detectors cannot be physically installed, or to motors for which rotor position detectors are not tolerant of the operating environment.

[0007] A typical method for estimating rotor position in sensorless control is the induced voltage method. The induced voltage method involves using voltage commands and current detection values ​​to calculate the induced voltage based on a motor model, and then using this induced voltage to estimate the rotor position.

[0008] However, in the low-speed region where the induced voltage is small, it is difficult to detect the rotor position due to errors in the actual applied voltage relative to the voltage command, errors in current detection, and limitations in current detection resolution.

[0009] Patent document 1 proposes a method for detecting minute induced voltages during low-speed rotation. This method utilizes the differential value of the winding current during a zero-voltage vector period when no voltage is applied between the windings.

[0010] However, in the extremely low-speed region, which includes zero velocity, position estimation cannot be performed using induced voltage. In such a low-speed region, the methods disclosed in Patent Documents 2 and 3 and Non-Patent Documents 1 and 2 can be used. That is, the rotor position can be estimated by utilizing the phenomenon that the winding inductance caused by salient polarity changes with the rotor position. The winding inductance can be calculated based on the differential value of the current when a known voltage is applied.

[0011] Existing technical documents

[0012] Patent documents

[0013] Patent Document 1: International Publication No. 2012 / 153794

[0014] Patent Document 2: International Publication No. 2014 / 128947

[0015] Patent Document 3: Japanese Patent Application Publication No. 2011-176975

[0016] Non-patent literature

[0017] Non-Patent Literature 1: JBBartolo, C.S. C.S. Tanies, and C. Caruana, “An Investigation on the Performance of Current Derivative Sensors for the Sensorless Control of AC drives,” 2008 4th IET Conference on Power Electronics, Machines and Drives, York, 2008, pp. 532-536, DOI:10.1049 / cp:20080578.

[0018] Non-Patent Literature 2: S. Bolognani, S. Calligaro, R. Petrella, M. Sterrpellone, "Sensorless control for IPMSM using PWM excitation: Analytical developments and implementation issues," 2011 Symposium on Sensorless Control for Electrical Drives, Birmingham, 2011, pp. 64-73, DOI:10.1109 / SLED.2011.6051546. Summary of the Invention

[0019] The technical problem that the invention aims to solve

[0020] In sensorless control, the accuracy and speed of rotor position estimation significantly affect control characteristics. The accuracy and speed of current differential detection used to estimate rotor position are crucial factors directly influencing control characteristics.

[0021] Methods for detecting current differentials can be broadly categorized into those that calculate based on current detection values, as described in Patent Documents 1 and 2, and those that use dedicated current differential detectors, as described in Patent Document 3 and Non-Patent Documents 1 and 2.

[0022] In Patent Document 1, the current value is sampled at least twice during the zero-voltage period of the PWM program, and the change in current value is divided by the sampling time interval to calculate the differential value of the current. This method requires high-speed A / D conversion to achieve multiple samplings in a short time, which directly leads to increased costs.

[0023] In general, in methods that sample current values ​​and calculate their derivatives, short sampling intervals result in smaller current changes, leading to greater errors in the derivative due to current detection errors. Conversely, longer sampling intervals increase the time from detecting the current value to obtaining the derivative, negatively impacting controllability.

[0024] Since double sampling is susceptible to noise, methods such as increasing the number of samples and applying filtering are also used. However, this approach has the drawbacks of requiring high-speed A / D conversion and potentially increasing detection time.

[0025] In Patent Document 1, although the differential value of the current is calculated, this value is not used to estimate the rotor position, but rather for vibration suppression control. Therefore, the differential value of the current does not require such high precision. The differential value of the current calculated using the method described in Patent Document 1 is not suitable for estimating the rotor position.

[0026] In Patent Document 2, an analog circuit is used to convert the current detection signal into a current differential value. Specifically, it is configured to include a differential amplifier circuit that takes the current detection signal as input, and an integrating circuit that integrates the output of the differential amplifier circuit. The output of the integrating circuit is returned to the differential amplifier circuit, thereby inputting the differential amplified value between the integrated value and the current detection signal into the integrating circuit. This differential amplified value, which is the input value of the integrating circuit, is equivalent to the current differential value. Thus, the output of the integrating circuit becomes the current detection signal after filtering out the high-frequency components generated by the PWM signal used to control the inverter. In Patent Document 2, for a switched reluctance motor (SRM) with a high salient pole ratio and large inductance variation, the current switching timing is determined by comparing the current differential value with a threshold.

[0027] This method can obtain the current derivative value through a single sampling. However, it requires designing an integrator circuit corresponding to the PWM frequency, thus limiting the responsiveness of the current derivative value detection. Moreover, since the method is based on the current detection value to derive the current derivative value, it is directly affected by noise and circuit accuracy, thus presenting an inherent problem of difficulty in obtaining high-precision current derivative values.

[0028] Current detectors typically employ an analog sensor structure to detect current, thus exhibiting an error exceeding 1% of full scale. Therefore, it is crucial to select a current detector with a full-scale range that provides a margin of error for estimating the maximum current flowing through the motor windings. However, the current variation equivalent to the differential current value is relatively small, only a few percent of the detector's full-scale current. Consequently, to detect changes in winding inductance, it is necessary to read the change of approximately a few percent of the differential current value. Therefore, it is difficult to detect high-precision differential current values ​​based on the output of a current detector using an analog sensor with an inherent full-scale error exceeding 1%. Considering the influence of noise, detecting high-precision differential current values ​​becomes even more challenging.

[0029] The method of calculating the differential value of current based on the current detection value does not require the use of a dedicated detector, which is advantageous in terms of cost and space. However, in terms of detection accuracy and speed, the method of using a dedicated current differential detector is more advantageous.

[0030] Patent document 3 and non-patent documents 1 and 2 describe sensorless control using a dedicated current differential detector. Although the methods differ, they all operate based on the principle of a current transformer, where the voltage corresponding to the change in magnetic flux caused by the current in the primary coil is detected at the secondary coil terminal. That is, the differential value of the primary current can be directly detected in the secondary coil. Because the differential current value is directly detected, a better signal is more easily obtained compared to indirect detection based on the current detection value.

[0031] Patent document 3 Figure 2 The diagram illustrates a structure in which a secondary coil is added to the core of a current detector using a Hall element, thereby enabling current detection and current differential detection to share a common coil.

[0032] However, in this structure, the influence of the current flux in the secondary coil causes a change in the core flux, which may lead to inaccurate current detection. The detection principle of the current transformer is to have current flowing in the secondary coil in the direction that cancels out the primary coil flux, and to detect the secondary current based on the voltage drop across the load resistor connected to the coil terminals of the secondary coil. While it is not impossible to obtain a suitable output through the design of the load resistor and the coil, it is still difficult to satisfy the characteristics of both detectors with a single core.

[0033] Furthermore, when driving a motor with high voltage, the potential of the primary coil becomes high. Therefore, according to safety standards, a voltage-appropriate insulation distance must be maintained between the primary and secondary coils. The coating of the magnetic wire used in the windings cannot be considered an insulator according to safety standards; therefore, other means are needed to ensure insulation. Consequently, miniaturization of the detector is difficult.

[0034] Non-patent literature 1 describes the characteristics of current differential sensors for sensorless control, employing the most commonly used loop coil structure and a structure using coaxial cable as the winding. The loop coil has the characteristic of detecting only the current flux flowing within the loop, thus being unaffected by external magnetic flux. This literature... Figure 6 In the structure shown, only the secondary coil is a winding, and the current-carrying lead passes through the ring and is regarded as a single-turn coil on the primary side.

[0035] In current differentiators based on the current transformer principle, using magnetic materials for the core makes it easier to obtain a larger output voltage, but it is susceptible to magnetic saturation and high-frequency characteristics of the magnetic material. Furthermore, its responsiveness is worse than that of an air-core coil. Non-patent literature 1 shows that... Figure 5 The conclusion shown is that the hollow coaxial cable coil has better responsiveness.

[0036] A coaxial cable coil is formed by winding a coaxial cable into a coil shape. One conductor of the coaxial cable is used to provide power, and the other conductor is used for sensing. The conductor providing power carries a large current and therefore must be very thick. Under high voltage, a large insulation distance is required between the conductors. Therefore, because the coaxial conductor itself is very thick, it cannot be wound multiple times. Consequently, it is difficult to obtain a large output and also difficult to achieve miniaturization.

[0037] Non-Patent Document 2 describes a current differential sensor with a hollow ring structure called a Rogowski coil. Since the core does not use a magnetic material, magnetic saturation does not occur, resulting in a highly responsive output. Because it is hollow, even with a large number of turns in the secondary coil, the output voltage is very small. To reduce the effort of winding multiple windings on the ring-shaped core, the windings are wound on a tubular object, and then the two ends of the tubular object are connected to form a ring (see this document). Figure 5 In Non-Patent Document 2, three Rogowski coils were used, but because their outputs were different, a signal conditioning circuit was used to make the characteristics consistent.

[0038] Therefore, current differential detectors are currently handcrafted for research purposes, and there are no commercially available current differential detectors for commercial use. Current differential detectors using magnetic cores suffer from magnetic saturation and responsiveness issues. While air-core structures do not have these problems, the secondary winding needs to be wound multiple times. Especially in manufacturing toroidal windings, mechanization is not feasible, requiring manual labor and significant time investment. This increases costs. Furthermore, it is difficult to manufacture without deviation, necessitating adjustments to ensure consistent characteristics. Additionally, miniaturization is difficult, especially for high-voltage applications where insulation between the primary and secondary sides is required, thus increasing the overall size.

[0039] The aforementioned limitations of current differential detectors mean that it is practically impossible to provide motor drive devices that can achieve a level of control for AC motors without sensors, starting from extremely low speeds.

[0040] One embodiment of the present invention provides a motor control device that helps to overcome the above-mentioned problems.

[0041] Technical means for solving technical problems

[0042] One embodiment of the present invention provides a motor control device for controlling an AC motor by sensorless control without using a rotor position detector. The motor control device includes: an inverter that converts DC to AC based on a pulse width modulation signal; a multilayer printed circuit board having wiring patterns in its inner layers inserted into current lines connecting the inverter and the windings of the AC motor; a plurality (preferably an even number) of surface-mount inductors mounted on the main surface of the multilayer printed circuit board such that the winding direction is oriented in a predetermined direction intersecting with and opposite to the wiring pattern, the plurality of surface-mount inductors being connected in series to form a series circuit having a midpoint connected to a reference potential; a load resistor connected between the midpoint of the series circuit and the two ends of the series circuit; a differential amplifier circuit with a pair of input terminals connected to the two ends of the series circuit; and a control unit that uses the output of the differential amplifier circuit to estimate the rotor position of the AC motor and generates a pulse width modulation signal provided to the inverter based on the estimated rotor position.

[0043] According to this structure, a wiring pattern of a multilayer printed circuit board (PCB) is inserted into the current path of the winding connecting the inverter and the AC motor. This wiring pattern is formed in the inner layer of the PCB, thus ensuring good insulation between it and the main surface of the PCB. A surface mount inductor is mounted on the main surface of the PCB, opposite the wiring pattern. The surface mount inductor is configured such that its winding direction faces a predetermined direction intersecting the wiring pattern. That is, the wiring pattern formed in the inner layer of the PCB and the surface mount inductor mounted on the main surface of the PCB are electrically insulated from each other by the insulating material of the PCB, and the wiring pattern intersects the winding direction of the surface mount inductor. Therefore, the magnetic flux generated by the current flowing through the wiring pattern links with the winding of the surface mount inductor. When the current flowing through the wiring pattern changes, causing a change in the magnetic flux, the surface mount inductor generates an electromotive force that prevents this change in magnetic flux, resulting in a corresponding voltage between the two electrodes of the surface mount inductor. This voltage can be processed as a signal representing the time variation of the current flowing through the wiring pattern, in other words, representing the derivative of the current. Therefore, the surface mount inductor functions as a sensor that directly detects the differential current, thus eliminating the need for complex and time-consuming computational processing to detect the differential current value.

[0044] Multiple surface-mount inductors of this type are mounted on the main surface of a multilayer printed circuit board and connected in series. The midpoint of this series circuit is connected to a reference potential, and the two ends of the series circuit are respectively connected to a pair of input terminals of a differential amplifier circuit. Load resistors are connected between the two ends of the series circuit and the midpoint. The electromotive force generated by the surface-mount inductor causes current to flow through the load resistor and generates a voltage drop, and the corresponding signal is input to the differential amplifier circuit. By connecting the midpoint of the series circuit to the reference potential, the potential at the midpoint does not change even if the potential of the wiring pattern changes significantly due to switching in the inverter. Therefore, the effects of switching can be suppressed, and a stable signal can be input to the differential amplifier circuit.

[0045] A differential amplifier circuit differentially amplifies the signal input to a pair of input terminals, thus removing the in-phase component and amplifying the out-of-phase components. Since noise components are in-phase, the differential amplifier circuit can amplify and output the noise-removed signal component. Therefore, even if the differential current signal output from the surface-mount inductor is small, it can be detected with a good signal-to-noise ratio.

[0046] Therefore, the current supplied to the AC motor from the inverter can be detected directly (and thus at high speed) using a surface-mount inductor, and a good signal representing the current derivative can be obtained. Consequently, the control unit can quickly and accurately estimate the rotor position of the AC motor, thus enabling highly responsive and accurate motor control.

[0047] Furthermore, industrially produced surface mount inductors exhibit very small performance deviations, thus eliminating the need for individual adjustments even when using multiple surface mount inductors. Additionally, the tiny size of surface mount inductors allows for the use of very compact structures for detecting current differentials.

[0048] For example, not only surface-mount inductors can be mounted on multilayer printed circuit boards (PCBs), but also some or all of the load resistors, differential amplifier circuits, inverters, and control units can be mounted on the PCB. This enables the overall miniaturization of the motor control device. In other words, it provides a structure that can both suppress or prevent the enlargement of the motor control device and directly and accurately detect the differential current value, thereby achieving highly responsive and accurate motor control.

[0049] In one embodiment of the invention, the plurality of surface-mount inductors are connected in series so that the direction of the electromotive force induced in each surface-mount inductor due to the change in magnetic flux caused by the current flowing through the wiring pattern is consistent. With this structure, the sum of the electromotive forces generated by the plurality of surface-mount inductors can be amplified using a differential amplifier circuit, thus obtaining a larger signal representing the current derivative. Furthermore, the deviations in the characteristics of each surface-mount inductor are averaged, enabling more accurate detection of the current derivative value.

[0050] In one embodiment of the present invention, the total number of the plurality of surface mount inductors is even. With this structure, the series circuit of the plurality of surface mount inductors can easily form a symmetrical structure centered on the midpoint, thus easily achieving input balance to a pair of input terminals of the differential amplifier circuit.

[0051] In one embodiment of the invention, the control unit is configured to process the output of the differential amplifier circuit as a value corresponding to the time derivative (current derivative) of the winding current of the AC motor to estimate the rotor position. If the time derivative (current derivative) of the winding current can be obtained, the winding inductance can be calculated, for example, based on this time derivative. Since the winding inductance changes periodically with the rotor position, the rotor position can be estimated based on the winding inductance.

[0052] In one embodiment of the present invention, the plurality of surface mount inductors are mounted in the same number on two opposite main surfaces of the multilayer printed circuit board.

[0053] By mounting the same number of surface-mount inductors on one main surface and the other main surface of a multilayer printed circuit board, the series circuit can easily form a symmetrical structure with the midpoint as the center. Therefore, the inputs of a pair of input terminals of the dynamic amplifier circuit can easily reach a balance.

[0054] Furthermore, by separately mounting multiple surface mount inductors on one main surface and another main surface of a multilayer printed circuit board, surface mount inductors can be configured in three dimensions, thus enabling further miniaturization of the motor control device.

[0055] Furthermore, the direction of the magnetic flux generated by the current flowing through the wiring pattern is opposite on one main surface and the other main surface of the multilayer printed circuit board. Conversely, the magnetic flux generated externally, i.e., not caused by the current flowing through the wiring pattern, is in the same direction and has the same magnitude on one main surface and the other main surface of the multilayer printed circuit board. As described above, it is preferable to connect multiple surface mount inductors in series so that the direction of the electromotive force induced in each surface mount inductor due to the change in the magnetic flux generated by the current flowing through the wiring pattern is consistent. In this case, the voltage appearing across the series circuit of the multiple surface mount inductors becomes a value that is superimposed on the electromotive force generated in each surface mount inductor according to the change in the current flowing through the wiring pattern, and cancels out the electromotive force caused by the externally generated magnetic flux. Thus, the influence of externally generated magnetic flux can be suppressed or prevented to detect the current differential.

[0056] In one embodiment of the present invention, the plurality of surface mount inductors are arranged in a quantity of 1 on one main surface of the multilayer printed circuit board and in a quantity of 1 on another main surface opposite to the one main surface.

[0057] In this case, it is preferable to make a surface-mount inductor on one main facet side and a surface-mount inductor on the other main facet side geometrically symmetrical with respect to the wiring pattern through which the winding current flows. In other words, it is preferable to design the distance from the wiring pattern through which the winding current flows to a surface-mount inductor on one main facet side (the sum of distances in the case of multiple wiring patterns, the same below) to the distance to a surface-mount inductor on the other main facet side to be equal to each other. Thus, the inputs to a pair of input terminals of the differential amplifier circuit can be easily balanced.

[0058] In one embodiment of the present invention, the plurality of surface mount inductors are arranged in a quantity of 2 on one main surface of the multilayer printed circuit board and in a quantity of 2 on another main surface opposite to the one main surface.

[0059] In this case, it is preferable to connect one surface-mount inductor on one main surface of the multilayer printed circuit board in series with a surface-mount inductor on another main surface and configure it on one side of the midpoint, and connect the remaining two surface-mount inductors in series on the other side of the midpoint, thereby connecting four surface-mount inductors in series. Thus, the geometric configuration of the surface-mount inductors relative to the wiring pattern through which the winding current flows (more specifically, the distance from the wiring pattern to the surface-mount inductor) is equivalent (symmetrical) on both sides of the midpoint of the series circuit. Such a connection (configuration) is particularly effective when the surface-mount inductors mounted on one main surface and the surface-mount inductors mounted on the other main surface are not equivalent (symmetrical) relative to the geometric configuration of the wiring pattern (more specifically, the distance from the wiring pattern to the surface-mount inductor).

[0060] In one embodiment of the present invention, the surface mount inductor is an air-core coil and is unshielded. By using an air-core coil type surface mount inductor, current differentials can be detected without being affected by magnetic saturation. Furthermore, by using an unshielded surface mount inductor, the magnetic flux formed by the current flowing through the wiring pattern can be detected with high sensitivity.

[0061] In one embodiment of the invention, the plurality of surface mount inductors are of identical specifications. By using surface mount inductors of identical specifications, it is easy to form a series circuit with a structure symmetrical about the midpoint. Industrially produced surface mount inductors of the same specifications have identical performance, therefore no substantial adjustments are required during use.

[0062] Invention Effects

[0063] According to the present invention, the current derivative of the winding current can be detected quickly and accurately, and the current derivative can be detected with a small structure, thereby providing a small motor control device that can achieve excellent motor control response. Attached Figure Description

[0064] Figure 1A This is a block diagram illustrating the structure of a motor control device according to one embodiment of the present invention.

[0065] Figure 1B This is a block diagram illustrating the functional structure of the controller in the electric motor control device.

[0066] Figure 2 This is a block diagram showing a specific example of the detailed structure associated with a current controller.

[0067] Figure 3 This is a circuit diagram used to illustrate an example of the inverter's structure.

[0068] Figure 4A and Figure 4B This represents the voltage vector corresponding to the eight states of the inverter.

[0069] Figure 5 This diagram illustrates the principle of position detection based on the differential value of current.

[0070] Figure 6 This is a three-dimensional diagram illustrating the construction of the current differential detector in the first specific example.

[0071] Figure 7A This is a top view of the current differential detector. Figure 7B This is a cross-sectional view of the current differential detector.

[0072] Figure 8 This is a circuit diagram illustrating an example of the structure of the current differential detector.

[0073] Figure 9 This is a three-dimensional diagram illustrating the construction of the current differential detector in the second specific example.

[0074] Figure 10A This is a top view of the current differential detector. Figure 10B This is a cross-sectional view of the current differential detector.

[0075] Figure 11 This is a circuit diagram illustrating an example of the structure of the current differential detector.

[0076] Figure 11A This is a circuit diagram illustrating another structural example of the current differential detector.

[0077] Figure 12 An example of a waveform diagram showing the PWM control signal, etc., of an AC motor M rotating at low speed.

[0078] Figure 13A , Figure 13B and Figure 13C This represents the differential current detection voltage obtained by applying test pulses at various rotor electrical angles while simultaneously detecting the rotor electrical angle using an encoder. Detailed Implementation

[0079] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0080] Figure 1A This is a block diagram illustrating the structure of a motor control device according to one embodiment of the present invention. The motor control device 100 is a device for driving an AC motor M. More specifically, the motor control device 100 drives the AC motor M through so-called sensorless control, which controls the AC motor M without using a rotor position detector to detect the position of the rotor. The AC motor M can be a surface magnet synchronous motor (SPMSM). The AC motor M is, for example, a three-phase AC motor having a U-phase winding 5u, a V-phase winding 5v, and a W-phase winding 5w. Hereinafter, these windings will be collectively referred to as "winding 5uvw".

[0081] In this example, the motor control device 100 has a feedback system including a position control loop, a speed control loop, and a current control loop, configured as a position servo control to control the rotor position of the AC motor M according to position commands. Vector control is used for current control.

[0082] Regarding rotor position, a rotor position detector is not used; instead, a signal obtained from a current differential detector is used to estimate the position using a position estimator. More specifically, based on the current differential value, the inductance of each phase winding of the AC motor M is estimated, and the rotor position is estimated based on this inductance. Surface magnet synchronous motors do not inherently possess salient polarity; therefore, inductance changes cannot be used for magnetic pole detection. However, when using strong magnets such as neodymium magnets, the inductance will change somewhat due to the magnetic saturation of the iron core.

[0083] In terms of specific structure, the motor control device 100 includes a controller 1 as a control unit, an inverter 2, current detectors 3u, 3v, 3w, and current differential detectors 4u, 4v, 4w. The inverter 2 converts the DC current supplied by the DC voltage 7 into AC current and supplies it to the winding 5uvw of the AC motor M. The inverter 2 is connected to the AC motor M via three current lines 9u, 9v, 9w (hereinafter collectively referred to as "current lines 9uvw") corresponding to phases U, V, and W. These current lines 9uvw are equipped with current detectors 3u, 3v, 3w, and current differential detectors 4u, 4v, 4w, respectively. The current detectors 3u, 3v, 3w (hereinafter collectively referred to as "current detectors 3uvw") detect the phase current flowing through the corresponding phase current line 9uvw, that is, they detect the U-phase current Iu, V-phase current Iv, and W-phase current Iw (hereinafter collectively referred to as "phase current Iuvw"), respectively. The current differential detectors 4u, 4v, and 4w (hereinafter collectively referred to as "current differential detector 4uvw") detect the time change of the phase current flowing through the current line 9uvw of the corresponding phase, that is, detect the current differential values ​​dIu, dIv, and dIw of phase U, phase V, and phase W (hereinafter collectively referred to as "current differential value dIuvw").

[0084] Controller 1 controls inverter 2 based on position command θcmd. Controller 1 is in the form of a computer, including processor (CPU) 1a and memory 1b. Memory 1b serves as a recording medium to record the program executed by processor 1a.

[0085] Figure 1B This is a block diagram illustrating the functional structure of controller 1. Controller 1 is configured to execute a program via processor 1a to implement the functions of multiple functional processing units. The multiple functional processing units include a position controller 11, a speed controller 12, a current controller 13, a PWM generator 14, a position estimator 15, and a speed estimator 16.

[0086] The position estimator 15 uses the signal output by the current differential detector 4uvw, i.e., the current differential value dIuvw, to calculate and estimate the rotor position of the AC motor M, and feeds back the estimated position θfb to the position controller 11. Based on the estimated position θfb, the position controller 11 generates a speed command ωcmd that makes the rotor position consistent with the position command θcmd, and provides it to the speed controller 12. Thus, a position control loop is formed.

[0087] The estimated rotor position θfb is also provided to the speed estimator 16. The speed estimator 16 calculates the time change of the estimated position θfb and performs calculations to estimate the rotor speed, providing the estimated speed ωfb to the speed controller 12. Based on the estimated speed ωfb, the speed controller 12 generates current commands Idcmd and Iqcmd to make the rotor speed consistent with the speed command ωcmd, and provides them to the current controller 13. Thus, a speed control loop is formed.

[0088] The current controller 13 receives the phase current Iuvw detected by the current detector 3uvw (more precisely, the detected value of the phase current Iuvw). The current controller 13 generates U-phase voltage commands Vu, V-phase voltage commands Vv, and W-phase voltage commands Vw (hereinafter collectively referred to as "voltage commands Vuvw") to match the phase current Iuvw with the current commands Idcmd and Iqcmd, and provides them to the PWM generator 14. This constitutes the current control loop.

[0089] PWM generator 14 generates a PWM control signal (pulse width modulation signal) corresponding to the voltage command Vuvw and provides it to inverter 2. As a result, the voltage corresponding to the voltage command Vuvw is applied between the windings 5uvw of AC motor M via current line 9uvw.

[0090] Figure 2 This is a block diagram illustrating a specific example of the detailed structure associated with the current controller 13. The speed controller 12 generates d-axis current commands Idcmd and q-axis current commands Iqcmd according to the dq rotating coordinate system and provides them to the current controller 13. The dq rotating coordinate system is a rotating coordinate system that defines the magnetic flux direction of the rotor of the AC motor M as the d-axis and the direction orthogonal to it as the q-axis, rotating according to the rotor's rotation angle (electric angle). The current controller 13 includes a dq current controller 131, an inverse dq converter 132, a two-phase to three-phase converter 133, a three-phase to two-phase converter 134, and a dq converter 135. The three-phase to two-phase converter 134 converts the three-phase phase currents Iuvw detected by the current detector 3uvw into two-phase current values ​​I in the two-phase fixed coordinate system, i.e., the αβ coordinate system. α I β The two-phase current values ​​I of the DQ converter 135 in the αβ coordinate system.α I β A coordinate transformation is performed, converting the current values ​​Id and Iq in the dq rotating coordinate system. These current values ​​Id and Iq are provided to the dq current controller 131. The dq current controller 131 generates voltage commands in the dq rotating coordinate system, namely the d-axis voltage command Vdcmd and the q-axis voltage command Vqcmd, so that the d-axis current value Id and the q-axis current value Iq are consistent with the d-axis current command Idcmd and the q-axis current command Iqcmd, respectively. These voltage commands Vdcmd and Vqcmd are then converted into voltage commands Vαcmd and Vβcmd in the αβ coordinate system in the inverse dq converter 132. These αβ coordinate system voltage commands Vαcmd and Vβcmd are then converted into a three-phase voltage command Vuvw by the two-phase to three-phase converter 133. This three-phase voltage command Vuvw is provided to the PWM generator 14.

[0091] Position estimator 15 calculates the rotor angle in the αβ coordinate system and provides it as the estimated position θfb to the inverse dq converter 132 and the dq converter 135. The estimated position θfb is used for coordinate transformation between the dq rotating coordinate system and the αβ coordinate system, and is also used for velocity estimation in the velocity estimator 16.

[0092] Figure 3 This is a circuit diagram illustrating an example of the structure of inverter 2. A three-phase bridge circuit 20u, 20v, and 20w is connected in parallel between a pair of power supply lines 8A and 8B connected to the DC power supply 7. A capacitor 26 for filtering is also connected between the pair of power supply lines 8A and 8B.

[0093] Each bridging circuit 20u, 20v, 20w (hereinafter collectively referred to as "bridging circuit 20uvw") is composed of a series circuit of upper arm switching elements 21u, 21v, 21w (hereinafter collectively referred to as "upper arm switching element 21uvw") and lower arm switching elements 22u, 22v, 22w (hereinafter collectively referred to as "lower arm switching element 22uvw"). In each bridging circuit 20uvw, a current line 9uvw for connecting to the corresponding winding 5uvw of the AC motor M is connected at the midpoint 23u, 23v, 23w between the upper arm switching element 21uvw and the lower arm switching element 22uvw.

[0094] The switching elements 21uvw and 22uvw are typically power MOS transistors, which have built-in parasitic diodes 24u, 24v, 24w, 25u, 25v, and 25w that are reverse-connected to the DC power supply 7.

[0095] The current differential detector 4uvw is configured to detect the time differential value of the phase current Iuvw flowing through the current circuit 9uvw of each phase, which is the current differential value dIuvw.

[0096] The PWM control signal provided by controller 1 is input to the gates of switching elements 21uvw and 22uvw, thereby turning the switching elements 21uvw and 22uvw on / off. The upper arm switching element 21uvw and lower arm switching element 22uvw of each bridge circuit 20uvw are paired, controlled such that when one is on, the other is off. The PWM control signal value controlling the state where the upper arm switching element 21uvw is on and the lower arm switching element 22uvw is off is defined as "1", and the PWM control signal value controlling the state where the upper arm switching element 21uvw is off and the lower arm switching element 22uvw is on is defined as "0". In this way, the PWM control signal can take on 8 modes (states) expressed by a three-dimensional vector. These 8 modes (states) can be represented by components as (1,0,0), (1,1,0), (0,1,0), (0,1,1), (0,0,1), (1,0,1), (0,0,0), (1,1,1). The first six modes (1,0,0), (1,1,0), (0,1,0), (0,1,1), (0,0,1), and (1,0,1) correspond to the state where voltage is applied between the 5uvw windings of the AC motor M. The remaining two modes (0,0,0) and (1,1,1) correspond to the state where no voltage is applied between the 5uvw windings.

[0097] Figure 4A The voltage vectors V0 to V7 correspond to the eight modes (states) mentioned above. The voltage vectors V1(1,0,0), V2(1,1,0), V3(0,1,0), V4(0,1,1), V5(0,0,1), and V6(1,0,1) corresponding to the six modes of applying voltage between windings are shown below. Figure 4B As shown, this can be expressed by six voltage vectors that divide the 360-degree electrical angle into six equal parts. Voltage vectors V0(0,0,0) and V7(1,1,1) are zero voltage vectors when no voltage is applied between the windings 5uvw.

[0098] Figure 5 This diagram illustrates the position detection principle based on the differential current value dIuvw. The relationship between the differential current value dIuvw and the inductances Lu, Lv, and Lw of the windings 5uvw in each phase is shown in the following equation.

[0099] Vu=Lu·dIu(1)

[0100] Vv=Lv·dIv(2)

[0101] Vw=Lw·dIw(3)

[0102] Therefore, the inductances Lu, Lv, and Lw of each phase winding 5uvw can be calculated based on the voltage command Vuvw of each phase and the differential current value dIuvw of each phase.

[0103] On the other hand, the inductances Lu, Lv, and Lw of each phase are known as follows: Figure 5 The inductance of each phase, Lu, Lv, and Lw, varies periodically with a period of half the electrical angular period of the rotor.

[0104] Lu=L0-L1cos (2θ) (4)

[0105] Lv=L0-L1cos (2 (θ-2π / 3)) (5)

[0106] Lw=L0-L1cos (2 (θ+2π / 3)) (6)

[0107] Where L0 is the fixed component of the inductance, L1 represents the amplitude of the variable component of the inductance, and θ represents the electrical angular position of the rotor.

[0108] Therefore, by calculating the inductances Lu, Lv, and Lw of each phase, the electrical angle θ of the rotor can be estimated.

[0109] Figure 6 This is a three-dimensional diagram illustrating the construction of the current differential detector 4uvw in the first specific example. Figure 7A This is a top view of the 4uvw current differential detector. Figure 7B This is a cross-sectional view of the current differentiating detector 4uvw. The structure of the current differentiating detector 4uvw is identical in all phases. Figure 6 , Figure 7A , Figure 7B And the following Figure 8 The diagram shows the structure of a single-phase current differential detector 4uvw. That is, for each phase, there is a... Figure 6 , Figure 7A , Figure 7B And the following Figure 8 The structure shown is described above. Preferably, the printed circuit board 40 is shared by the U phase, V phase, and W phase.

[0110] The current differential detector 4uvw includes a printed circuit board 40 and multiple surface mount inductors L1, L2. The printed circuit board 40 is a multilayer printed wiring board. More specifically, the printed circuit board 40 has a multilayer wiring structure in which insulating substrates are used to insulate between the multilayer printed wiring layers. More specifically, in this example, a multilayer printed wiring board having four printed wiring layers 43-46 is used. The four printed wiring layers include: a pair of outer printed wiring layers 43, 44 formed on a pair of main surfaces 41, 42 of the printed circuit board 40; and a pair of inner printed wiring layers 45, 46 sandwiching insulating layers 47, 48 (insulating substrates) formed inside the pair of outer printed wiring layers 43, 44. Another insulating layer 49 (insulating substrate) is also disposed between the pair of inner printed wiring layers 45, 46.

[0111] Current patterns 51 and 52 are formed on a pair of inner printed wiring layers 45 and 46, respectively. These current patterns 51 and 52 constitute part of a current line 9uvw connected to a motor winding 5uvw. These current patterns 51 and 52 are short-circuited at both ends, forming a current path that branches into two paths at the middle of the current line 9uvw and merges at other locations. The two current patterns 51 and 52 are opposite to the directions perpendicular to the main surfaces 41 and 42 of the printed circuit board 40, and are formed as parallel strips (e.g., straight strips) sandwiching an insulating layer 49 (insulating substrate) and facing each other.

[0112] The printed circuit board 40 is, for example, a four-layer substrate with an overall thickness of 1.6 mm. The current patterns 51 and 52 of the inner printed wiring layers 45 and 46 of the printed circuit board 40 have different wiring layers, but their width, thickness, and position when viewed from above are the same. Furthermore, their ends are short-circuited, allowing substantially equal current to flow. The inner printed wiring layers 45 and 46 are located, for example, 0.2 mm inside the main surfaces 41 and 42 (substrate surfaces) of the printed circuit board 40.

[0113] On a pair of main surfaces 41, 42 of a printed circuit board 40, a pair of surface mount inductors L1, L2 are mounted at positions opposite to current patterns 51, 52, respectively. These surface mount inductors L1, L2 are identical in size. The pair of surface mount inductors L1, L2 are mounted on each main surface with their windings oriented in a predetermined direction 53, intersecting with the current patterns 51, 52, and more specifically, orthogonally (orthogonally in plan view). The surface mount inductors L1, L2 are typically small cuboids, for example, with plan view dimensions of 2.5 mm × 1.8 mm. A pair of electrodes 54 are provided at each end of the winding direction (e.g., along the long side). These electrodes 54 are connected to the ends of the coils embedded in the surface mount inductors L1, L2. The surface mount inductors L1, L2 are air-wound and are not magnetically shielded. The winding direction is the inter-electrode direction. The winding direction refers to the direction of the winding center axis of the coil, which is the direction of magnetic flux generated when current flows through the coil. A pair of electrodes 54 of the surface mount inductors L1 and L2 are bonded to the outer printed wiring layers 43 and 44 formed on the main surfaces 41 and 42 of the printed circuit board 40 using a bonding material such as solder (not shown). In this embodiment, the pair of surface mount inductors L1 and L2, respectively mounted on a pair of main surfaces 41 and 42 of the printed circuit board 40, are arranged so that they coincide when viewed from a direction perpendicular to the main surfaces 41 and 42 of the printed circuit board 40. In other words, the pair of surface mount inductors L1 and L2 are arranged parallel to each other, sandwiching current patterns 51 and 52.

[0114] When current flows through current patterns 51 and 52, the current generates magnetic flux surrounding the current patterns 51 and 52. The direction of this magnetic flux is opposite to that on one main surface 41 and the other main surface 42 of the printed circuit board 40, and is parallel to the winding direction (defined direction 53) of the surface mount inductors L1 and L2. Therefore, the magnetic flux generated by the current flowing through current patterns 51 and 52 links with the surface mount inductors L1 and L2, respectively. As the magnetic flux increases, an electromotive force is generated in the surface mount inductors L1 and L2, thereby allowing current to flow that inhibits the increase of the magnetic flux. For example, when the current flowing through current patterns 51 and 52 is along arrow 50 (refer to...) Figure 7A When the direction of the magnetic flux increases, in order to suppress the resulting change in magnetic flux, the surface mount inductors L1 and L2 generate arrows 55 and 56 respectively (refer to...). Figure 7BThe electromotive force (EMF) in the direction of the magnetic flux decreases. Similarly, during the decrease of magnetic flux, an EMF is generated in the surface mount inductors L1 and L2, thereby allowing current to flow that inhibits the decrease of magnetic flux. Therefore, the EMF generated in the surface mount inductors L1 and L2 is equivalent to the time derivative of the current flowing through the current patterns 51 and 52. Since the surface mount inductors L1 and L2 are geometrically symmetrical with respect to the current patterns 51 and 52, the EMFs generated by the surface mount inductors L1 and L2 are substantially equal. Geometric symmetry means that the distances from the two current patterns 51 and 52 to the surface mount inductors L1 and L2 are substantially equal to each other. That is, the sum of the distances from the two current patterns 51 and 52 to the surface mount inductor L1 is substantially equal to the sum of the distances from the two current patterns 51 and 52 to the surface mount inductor L2.

[0115] like Figure 6 As shown, a pair of load resistors R1 and R2 are mounted on a pair of main surfaces 41 and 42 of the printed circuit board 40, and are respectively connected to surface mount inductors L1 and L2 mounted on the same main surfaces 41 and 42. The load resistors R1 and R2 are, for example, surface mount resistors and have equal resistance values. The electrodes of the load resistors R1 and R2 are connected to the electrodes 54 of the surface mount inductors L1 and L2 via external printed wiring layers 43 and 44.

[0116] Figure 8 This is a circuit diagram illustrating a structural example of a current differential detector 4uvw. A surface mount inductor L1 mounted on one main surface of the printed circuit board 40 and a surface mount inductor L2 mounted on the other main surface of the printed circuit board 40 are connected in series to form a series circuit 60. Furthermore, each surface mount inductor L1, L2 is connected in parallel with load resistors R1, R2. In other words, a parallel circuit 57 consisting of a surface mount inductor L1 mounted on one main surface 41 of the printed circuit board 40 and a load resistor R1, and a parallel circuit 58 consisting of a surface mount inductor L2 mounted on the other main surface 42 of the printed circuit board 40, are connected in series.

[0117] Two surface-mount inductors, L1 and L2, are connected to form a series circuit 60 so that the electromotive forces caused by the changes in current flowing through current patterns 51 and 52 are superimposed, i.e., they do not cancel each other out. In other words, the two surface-mount inductors L1 and L2 are connected in series so that the direction of the electromotive forces of the two surface-mount inductors L1 and L2 is the same from one end of the series circuit 60 to the other end (this direction is opposite when the current flowing through current patterns 51 and 52 increases and decreases).

[0118] The connection point 59 of the two surface-mount inductors L1 and L2 is connected to a stable reference potential, i.e., ground potential (0V). The two ends of the series circuit 60 of the two surface-mount inductors L1 and L2 are connected to a differential amplifier circuit 70. The differential amplifier circuit 70 includes an operational amplifier 71 and four resistors 74-77. The four resistors 74-77 include: resistor 74 connected between the output terminal and the inverting input terminal 72 of the operational amplifier 71; resistor 75 connected between the non-inverting input terminal 73 of the operational amplifier 71 and ground potential (0V); and resistors 76 and 77 respectively connected to the inverting input terminal 72 and the non-inverting input terminal 73 of the operational amplifier 71. One end of the series circuit 60 of the two surface-mount inductors L1 and L2 is connected to one input terminal 70b of the differential amplifier circuit 70, and is connected to the inverting input terminal 72 of the operational amplifier 71 via resistor 76. The other end of the series circuit 60 is connected to another input terminal 70a of the differential amplifier circuit 70, and is connected to the non-inverting input terminal 73 of the operational amplifier 71 via resistor 77.

[0119] The electrical / electronic components constituting the differential amplifier circuit 70 are preferably mounted on the printed circuit board 40. Additionally, although not shown, it is preferable to mount the components constituting... Figure 1A and Figure 1B Some or all of the electrical / electronic components of the motor control device 100 shown are also mounted on the printed circuit board 40.

[0120] When the current flowing through current patterns 51 and 52 changes, a voltage V proportional to the time change dΦ / dt of the magnetic flux Φ is generated between the terminals of each surface-mount inductor L1 and L2 due to electromagnetic induction. L1 V L2 (V L1 =V L2 =V L The voltage uses a proportionality constant K and is expressed by the following formula.

[0121] V L =V L1 =V L2 =K·dΦ / dt (7)

[0122] Since the magnitude of the magnetic flux Φ is proportional to the current I (phase current Iuvw), it can be rewritten as follows, thus yielding a voltage output proportional to the differential value of the current dI / dt. K' is a proportionality constant.

[0123] V L =K′·dI / dt (8)

[0124] In the circuit structure described above, surface mount inductors L1 and L2 are connected in series. Therefore, the output V0 of the differential amplifier circuit 70 is expressed using its gain G and the following formula. The output V0 is a signal representing the differential value of the current dIuvw.

[0125] V O =2·G·V L (9)

[0126] The current patterns 51 and 52 passing through the inner printed wiring layers 45 and 46 of the printed circuit board 40 act as single-turn primary windings, while the surface mount inductors L1 and L2 mounted on the main surfaces 41 and 42 of the printed circuit board 40 act as secondary windings, thus forming a transformer. In principle, the differential current can be detected by differentially amplifying the voltage between the electrodes of a single surface mount inductor. However, the signal voltage obtained from a small air-core surface mount inductor is a weak signal of about a few mV. On the other hand, the inverter 2, which controls the motor current, generates significant noise due to switching. Therefore, it is necessary to make it less susceptible to noise. For this reason, in this embodiment, multiple (specifically two) surface mount inductors L1 and L2 are used.

[0127] If the voltage across a surface mount inductor (only one of surface mount inductors L1 and L2) is differentially amplified, the following problem exists.

[0128] The surface mount inductor has a high impedance relative to ground potential (0V), causing its potential to fluctuate. The surface mount inductor is positioned on current patterns 51 and 52, with an insulation layer of, for example, 0.2 mm between it and the current patterns 51 and 52, resulting in parasitic capacitance. The potential of the current patterns 51 and 52 fluctuates between ground potential (0V) and the supply voltage Vdc as the inverter 2 is switched. The potential of the surface mount inductor, affected by this parasitic capacitance, also changes accordingly, causing the voltage across the terminals of the surface mount inductor to fluctuate in phase.

[0129] The differential amplifier circuit 70 can eliminate the in-phase variation when the two input signals vary in phase. However, the operational amplifier 71 has a limited input voltage range; therefore, input voltages exceeding its limits can cause damage or improper output. Although it is possible to reduce the input voltage through resistor division, the signal components are also divided, resulting in a smaller signal-to-noise ratio.

[0130] Reducing the impedance of the two terminals of a surface-mount inductor can suppress fluctuations, but the impedance of the signal source is high, which can lead to problems such as signal attenuation.

[0131] To suppress in-phase voltage fluctuations, it is considered to connect one terminal of the surface-mount inductor to a stable potential such as ground (0V). However, in the differential amplifier circuit 70, the imbalance of signal impedance can cause noise. Specifically, the terminal connected to ground has a lower impedance, resulting in almost no voltage fluctuation due to switching, while the other terminal has a higher impedance, causing potential fluctuations that cannot be eliminated, leading to noise output.

[0132] Therefore, in this specific example, two surface-mount inductors L1 and L2 are connected in series to form a series circuit 60. The midpoint 59 is connected to ground (0V), and load resistors R1 and R2 are connected between the midpoint 59 and the two ends of the series circuit 60. The two ends of the series circuit 60 are then connected to the two input terminals 70a and 70b of the differential amplifier circuit 70. This suppresses voltage fluctuations under common-mode conditions and eliminates impedance mismatch, thus removing in-phase noise.

[0133] Furthermore, in this specific example, two surface mount inductors L1 and L2 are separately mounted on the two main surfaces 41 and 42 of the printed circuit board 40. The two surface mount inductors L1 and L2 are connected in series so that they are linked with the magnetic fluxes generated in opposite directions on the two main surfaces 41 and 42 of the printed circuit board 40 by the currents flowing through the current patterns 51 and 52, and the electromotive forces generated according to the changes in these magnetic fluxes are superimposed. Therefore, even when there are external magnetic fluxes in the same direction on the two main surfaces 41 and 42 of the printed circuit board 40, the electromotive forces generated by the changes in these magnetic fluxes can be canceled out.

[0134] Figure 9 This is a three-dimensional diagram illustrating the construction of the current differential detector 4uvw in the second specific example. Figure 10A This is a top view of the 4uvw current differential detector. Figure 10B This is a cross-sectional view of the 4uvw current differential detector. Figure 11 This is a circuit diagram illustrating a structural example of a 4uvw current differential detector. Figure 9 , Figure 10A and Figure 10B and Figure 11 The diagram shows the structure of a single-phase current differential detector 4uvw. That is, for each phase, there is a... Figure 9 , Figure 10A , Figure 10B as well as Figure 11 The structure shown is described above. Preferably, the printed circuit board 40 is shared by the U phase, V phase, and W phase.

[0135] Similar to the first specific example, the current differential detector 4uvw includes a printed circuit board 40 ( Figure 9(Represented by double-dotted lines) and multiple surface-mount inductors L1 to L4. The printed circuit board 40 is the same multilayer printed wiring board as in the first embodiment. However, in this embodiment, only one of the pair of inner printed wiring layers 45 and 46 has a current pattern 52 formed, which constitutes part of a current line 9uvw connected to a motor winding 5uvw. The current pattern 52 is formed in a strip shape (e.g., a straight strip). The current pattern 52 (inner printed wiring layer 46) is located, for example, 0.2 mm inside one main surface 42 (substrate surface) of the printed circuit board 40, and, for example, 1.4 mm inside the other main surface 41.

[0136] Two surface mount inductors L1 and L4 are mounted on one main surface 41 of the printed circuit board 40, facing the current pattern 52. Similarly, two surface mount inductors L2 and L3 are mounted on the other main surface 42, also facing the current pattern 52. In this specific example, these four surface mount inductors L1 to L4 are identical in specifications. The four surface mount inductors L1 to L4 are mounted on the main surfaces 41 and 42 of the printed circuit board 40 with their windings oriented in a predetermined direction 53 intersecting the current pattern 52, or more specifically, orthogonal (orthogonal when viewed from above).

[0137] Similar to the first example, the surface mount inductors L1 to L4 are typically small cuboids, for example, with top-view dimensions of 2.5 mm × 1.8 mm. A pair of electrodes 54 are provided at each end of the winding direction (e.g., along the long side). These electrodes 54 are connected to the ends of the coils embedded in the surface mount inductors L1 to L4. The surface mount inductors L1 to L4 are air-wound type and are not magnetically shielded. The winding direction is the inter-electrode direction.

[0138] Although detailed illustrations are omitted, the pair of electrodes 54 of the surface mount inductors L1 to L4 are bonded to the external printed wiring layers 43 and 44 formed on the main surfaces 41 and 42 of the printed circuit board 40 using solder or other bonding materials. In this embodiment, the pair of surface mount inductors L1 and L2, respectively mounted on the pair of main surfaces 41 and 42 of the printed circuit board 40, are arranged so that they coincide when viewed from a direction perpendicular to the main surfaces of the printed circuit board 40. Similarly, the other pair of surface mount inductors L3 and L4, respectively mounted on the pair of main surfaces 41 and 42 of the printed circuit board 40, are also arranged so that they coincide when viewed from a direction perpendicular to the main surfaces of the printed circuit board 40. In other words, the pair of surface mount inductors L1 and L2 are arranged in parallel with the printed circuit board 40 (more specifically, the current pattern 52) facing each other, and the other pair of surface mount inductors L3 and L4 are arranged in parallel with the printed circuit board 40 (more specifically, the current pattern 52) facing each other. The specifications of the surface mount inductors L1 to L4 can be different, but it is preferred that a pair of surface mount inductors L1 and L4 disposed on one main surface 41 of the printed circuit board 40 have the same specifications, and a pair of surface mount inductors L2 and L3 disposed on another main surface 42 have the same specifications.

[0139] A pair of surface-mount inductors L1 and L2, sandwiched between each other on a printed circuit board 40, are connected in series via wiring layers on the printed circuit board 40 to form a series circuit 61. A load resistor R1 (see reference 40) is connected between the two ends of this series circuit 61 via wiring layers on the printed circuit board 40. Figure 11 A pair of surface-mount inductors L3 and L4, sandwiched between each other on the printed circuit board 40, are connected in series via wiring layers provided on the printed circuit board 40 to form a series circuit 62. A load resistor R2 (see reference 40) is connected between the two ends of this series circuit 62 via wiring layers provided on the printed circuit board 40. Figure 11 The load resistors R1 and R2 are, for example, surface mount resistors. Figure 9 , Figure 10A and Figure 10B The diagrams of load resistors R1 and R2 are omitted in the text.

[0140] A series circuit 61 consisting of a pair of surface mount inductors L1 and L2 sandwiching the printed circuit board 40 and a series circuit 62 consisting of another pair of surface mount inductors L3 and L4 sandwiching the printed circuit board 40 are further connected in series to form a series circuit 60. The four surface mount inductors L1 to L4 are connected to form the series circuit 60 so that the electromotive forces caused by the changes in the current flowing through the current pattern 52 are superimposed, i.e., they do not cancel each other out. In other words, the four surface mount inductors L1 to L4 are connected in series so that the direction of the electromotive force of each surface mount inductor L1 to L4 is the same direction from one end of the series circuit 60 to the other end (this direction is opposite when the current flowing through the current pattern 52 increases and decreases).

[0141] The connection point 59, which is the midpoint between two series circuits 61 and 62, each containing a pair of surface-mount inductors L1, L2 and L3, L4 respectively, is connected to a stable reference potential, i.e., ground potential (0V). The two ends of the series circuit 60 containing the four surface-mount inductors L1 to L4 are connected to the two input terminals 70a and 70b of the differential amplifier circuit 70, respectively. The structure of the differential amplifier circuit 70 is the same as in the first specific example, so its description is omitted.

[0142] When current flows through current pattern 52, the current generates a magnetic flux surrounding current pattern 52. The direction of this magnetic flux is opposite to that on one main surface 41 side and the other main surface 42 side of the printed circuit board 40, and is parallel to the winding direction (defined direction 53) of the surface mount inductors L1 to L4. Therefore, the magnetic flux generated by the current flowing through current pattern 52 links with surface mount inductors L1 to L4 respectively. As this magnetic flux increases, an electromotive force is generated in surface mount inductors L1 to L4, thereby allowing current to flow that inhibits the increase of the magnetic flux. For example, when the current flowing through current pattern 52 is along arrow 50 (refer to...) Figure 10A When the direction of the magnetic flux increases, in order to suppress the resulting change in magnetic flux, the surface mount inductors L1, L4 and L2, L3 generate arrows 55 and 56 respectively (refer to...). Figure 10B The electromotive force (EMF) is generated in the direction of the magnetic flux decreases. Similarly, during the process of decreasing magnetic flux, an EMF is generated in the surface mount inductors L1 to L4, thereby allowing a current to flow that inhibits the decrease in magnetic flux. Therefore, the EMF generated in the surface mount inductors L1 to L4 is equivalent to the time derivative of the current flowing through the current pattern 52.

[0143] In this specific example, the current pattern 52 within the printed circuit board 40 is formed only in an inner printed wiring layer 46 disposed near one main surface 42. Therefore, the distance from the current pattern 52 to the surface mount inductors L1 and L4 mounted on one main surface 41 is different from the distance from the current pattern 52 to the surface mount inductors L2 and L3 mounted on the other main surface 42. That is, the distance to the surface mount inductors L1 and L4 on one main surface 41 is greater than the distance to the surface mount inductors L2 and L3 on the other main surface 42. Correspondingly, the voltages induced in the surface mount inductors L1 to L4 are also different. Specifically, the electromotive force generated by the surface mount inductors L2 and L3 is greater than the electromotive force generated by the surface mount inductors L1 and L4.

[0144] Since the distances from the current pattern 52 to the surface mount inductors L1 to L4 are not the same, in the first specific example of a structure where only one surface mount inductor L1 and L2 are provided on one main surface 41 and the other main surface 42, the voltage from the midpoint 59 of the series circuit 60 of the surface mount inductors L1 and L2 to its two ends is unbalanced.

[0145] Therefore, in this second specific example, two surface mount inductors L1, L4 and L2, L3 are respectively provided on one main surface 41 and the other main surface 42 of the printed circuit board 40. Thus, the surface mount inductors L1, L4 on one main surface 41 and L2, L3 on the other main surface 42 are connected in series to form two series circuits 61, 62, with load resistors R1, R2 connected in parallel across the two ends of these series circuits 61, 62. These two series circuits 61, 62 are connected in series to form a series circuit 60. Therefore, the two sides of the midpoint 59 of this series circuit 60 can be balanced. That is, the output voltage across the series circuit 60 of the surface mount inductors L1 to L4 is symmetrical with respect to the midpoint 59. As a result, by connecting the two ends of the series circuit 60 of the four surface mount inductors L1 to L4 to the input terminals 70a and 70b of the differential amplifier circuit 70, the same output as in the first specific example can be obtained from the differential amplifier circuit 70.

[0146] The input to the differential amplifier circuit 70 is the sum of the output voltages of the four surface-mount inductors L1 to L4, regardless of the series connection order. If the connection order is changed, connecting a series circuit formed by connecting two surface-mount inductors L1 and L4 on one main surface in series with a series circuit formed by connecting two surface-mount inductors L2 and L3 on another main surface in series, the symmetry of the output voltages across the series circuit with respect to the midpoint 59 of the surface-mount inductors L1 to L4 is disrupted. This structure can still detect current differentials. However, in the differential amplifier circuit 70 operating at high speeds with small voltages, ensuring the symmetry of the voltages across the circuit with respect to the midpoint 59 of the series circuit with the surface-mount inductors L1 to L4 makes it easier to guarantee signal quality and is therefore preferred.

[0147] like Figure 11A As shown, load resistor R1 can be divided into load resistors R11 and R12 connected between the terminals of the two surface mount inductors L1 and L2 respectively. Similarly, load resistor R2 can also be divided into load resistors R21 and R22 connected between the terminals of the two surface mount inductors L3 and L4 respectively. In this case, the two load resistors R11 and R12 are connected in series to form load resistor R1, and the two load resistors R21 and R22 are connected in series to form load resistor R2.

[0148] Figure 12 An example of a waveform diagram showing the PWM control signal, etc., of an AC motor M rotating at low speed (including when it is stopped). Figure 12 (a) shows the waveform of the U-phase upper arm gate signal applied to the gate of the upper arm switching element 21u of the U-phase bridge circuit 20u of inverter 2. The U-phase lower arm gate signal (the signal applied to the gate of the lower arm switching element 22u) is the waveform after the signal is inverted. Figure 12(b) shows the waveform of the upper arm gate signal of the V phase 20V bridge circuit 20V of the inverter 2, which is applied to the gate of the upper arm switching element 21V. The lower arm gate signal of the V phase (the signal applied to the gate of the lower arm switching element 22V) is the waveform after the signal is inverted. Figure 12 (c) shows the waveform of the upper arm gate signal of phase W applied to the gate of the upper arm switching element 21w of the phase W bridge circuit 20w of inverter 2. The lower arm gate signal of phase W (the signal applied to the gate of the lower arm switching element 22w) is the waveform after inverting this signal. Furthermore, Figure 12 (d) represents the change in the U-phase current Iu output by the U-phase current detector 3u. Figure 12 (e) represents the change in the time derivative of the U-phase current, i.e., the U-phase current derivative dIu, which is equivalent to the output of the U-phase current derivative detector 4u.

[0149] like Figure 3 As shown, inverter 2 is a three-phase inverter composed of six switching elements 21uvw and 22uvw. The terminals of the three windings 5uvw of the U-phase, V-phase, and W-phase of the AC motor M are connected to either the power supply voltage Vdc or the ground potential (0V). As described above, the state connected to the power supply voltage Vdc (the state where the upper arm switching element 21uvw is on) is recorded as "1", and the state connected to 0V (the state where the upper arm switching element 21uvw is off) is recorded as "0". Thus, the generated voltage vector is as follows: Figure 4A As shown, there are 8 types of voltage vectors, from V0(0,0,0) to V7(1,1,1). Among them, V0(0,0,0) and V7(1,1,1) are zero-voltage vectors, where all winding terminals are at the same potential, resulting in zero voltage applied between windings 5uvw. The remaining 6 voltage vectors, V1 to V6, are non-zero voltage vectors that apply voltage between windings 5uvw.

[0150] The PWM generator 14 generates PWM control signals that turn on / off the switching elements 21uvw and 22uvw of the inverter 2 by comparing the phase voltage commands Vuvw output from the current controller 13 with a triangular wave carrier signal. For example, the PWM frequency (the frequency of the triangular wave carrier signal) is 14kHz, equivalent to a period of 70 microseconds. At low speeds, the phase voltage commands Vuvw are lower, therefore, the period of zero-voltage vectors V0 and V7, where no voltage is applied between the windings 5uvw, becomes longer. Figure 12 The diagram shows the waveforms of the state where the AC motor M is stopped, with the periods T0 of the zero voltage vector V0 and T7 of the zero voltage vector V7 being approximately half of the PWM cycle.

[0151] In addition to generating PWM control signals, the PWM generator 14 also applies a test pulse 121 for detecting rotor position during the period of the zero voltage vector V0 or V7. The test pulse 121 refers to the voltage vector used for position detection. The application time of the test pulse 121 is sufficiently short compared to the PWM period (e.g., approximately 70 microseconds), and much shorter than half the PWM period. More specifically, the application time of the test pulse 121 is preferably less than 10% of the PWM period, more preferably less than 5%. For example, if the application time of the test pulse 121 is set to 3 microseconds, it is approximately 4.2% of the PWM period when the PWM period is 70 microseconds.

[0152] To minimize the impact of the test pulse 121, it is preferable to immediately apply a cancelling pulse 122, defined by the voltage vector in the opposite direction of the test pulse 121, for the same duration as the test pulse 121, thereby canceling the current generated by the test pulse 121. In this case, the time for applying voltage to detect position is twice the application time of the test pulse 121. For example, if the application time of the test pulse 121 is set to 3 microseconds and the application time of the cancelling pulse 122 is set to 3 microseconds, then 6 microseconds, or 8.5%, of the 70-microsecond PWM cycle is used for applying voltage to detect position, while the remaining 64 microseconds, or 91.5%, are used for normal motor control.

[0153] Furthermore, in order to sequentially apply test pulse 121 and cancelling pulse 122 to phases U, V, and W in each PWM cycle, three voltage vectors are used for the test pulse 121, and three voltage vectors are used for the corresponding cancelling pulse 122. Thus, the effect of applying test pulse 121 for position detection is equal in all three phases.

[0154] Figure 12 In the example, the test pulse 121 applied to phase U is represented by voltage vector V1(1,0,0), and the cancellation pulse 122 applied to phase U is represented by voltage vector V4(0,1,1). The test pulse 121 applied to phase V is represented by voltage vector V3(0,1,0), and the cancellation pulse 122 applied to phase V is represented by voltage vector V6(1,0,1). The test pulse 121 applied to phase W is represented by voltage vector V5(0,0,1), and the cancellation pulse 122 applied to phase W is represented by voltage vector V2(1,1,0).

[0155] like Figure 12 (d) and Figure 12As shown in (e), the U-phase current changes and the U-phase current differential detection voltage changes upon the application of test pulse 121 and cancellation pulse 122. Since not only the current but also the differential value of the current is directly detected, it can be seen that the U-phase current differential detection voltage rises instantaneously when test pulse 121 is applied. Therefore, the differential value of the current can be detected substantially within the application time of test pulse 121 (e.g., 3 microseconds). The timing corresponding to the application of test pulse 121 becomes the differential detection point 123 where the differential value of the current should be sampled.

[0156] Figure 13A This represents the differential current detection voltage obtained by applying test pulses of voltage vector V1 under various rotor electrical angles while simultaneously detecting the rotor electrical angle using an encoder. Figure 13B Similarly, this represents the differential current detection voltage obtained by applying a test pulse with voltage vector V3. Figure 13C Similarly, this represents the current differential detection voltage obtained by applying a test pulse with voltage vector V5. A / D conversion is performed at the end of the test pulse, after the test pulse is applied and before the cancellation pulse is applied, to obtain the current differential detection voltage. The figures show the detection voltages for the U-phase current differential diU, V-phase current differential diV, and W-phase current differential diW. The actual measurement voltage range is 0–5V, centered at 2.5V, corresponding to a current differential value of 0.

[0157] For the test pulse of voltage vector V1, such as Figure 13A As shown, the detection voltage of the U-phase current derivative diU varies periodically around -1V relative to the center value of 2.5V (or around 1.5V if it is the measurement voltage), and the detection voltages of the V-phase current derivative diV and the W-phase current derivative diW vary periodically around +0.5V relative to the center value of 2.5V (or around 3.0V if it is the measurement voltage).

[0158] For the test pulse of voltage vector V3, such as Figure 13B As shown, the detection voltage of the V-phase current differential diV varies periodically around -1V relative to the center value of 2.5V (or around 1.5V if it is the measurement voltage), and the detection voltages of the U-phase current differential diU and the W-phase current differential diW vary periodically around +0.5V relative to the center value of 2.5V (or around 3.0V if it is the measurement voltage).

[0159] For the test pulse of voltage vector V5, such as Figure 13CAs shown, the detection voltage of the W-phase current differential diW varies periodically around -1V relative to the center value of 2.5V (or around 1.5V if it is the measurement voltage), and the detection voltages of the U-phase current differential diU and the V-phase current differential diV vary periodically around +0.5V relative to the center value of 2.5V (or around 3.0V if it is the measurement voltage).

[0160] When voltage vectors V1, V3, and V5 are applied, one phase is connected to the power supply voltage Vdc, and the other two phases are connected to 0V (ground potential). The direction of the applied voltage is opposite to that of the other two phases. Furthermore, since it is a three-phase system, the total current is zero, and the total differential current is also zero.

[0161] like Figure 13A , Figure 13B and Figure 13C As shown, although the amplitude is small, a three-phase sinusoidal signal with a phase difference of 120 degrees can be obtained for one cycle of the rotor electrical angle, thus enabling the determination of the rotor position. In this specific example, the rotor position is updated every PWM cycle (70 microseconds), with a detection accuracy of approximately ±1 degree of mechanical angle. Therefore, according to this embodiment, even for SPMSMs with low salient polarity and difficult sensorless control in low-speed regions, position servo control requiring accurate and rapid position feedback control can be achieved.

[0162] In this embodiment, three voltage vectors V1, V3, and V5 are used as test pulses to detect the differential values ​​of the three-phase current. However, even if only one voltage vector is used as a test pulse to detect the differential values ​​of the three-phase current, the rotor position can be estimated.

[0163] As described above, according to this embodiment, a motor control device 100 can be provided that controls an AC motor M through sensorless control without using a rotor position detector. This motor control device 100 is capable of detecting the current differential of the winding current of the AC motor M at high speed and with high accuracy, and can detect the current differential with a compact structure. Therefore, a motor control device 100 with a compact structure that can achieve highly responsive and accurate motor control can be provided.

[0164] Specifically, in this embodiment, current patterns 51 and 52, formed by wiring patterns of a printed circuit board 40 (multilayer printed circuit board), are inserted into the current line 9uvw of the winding 5uvw connecting the inverter 2 and the AC motor M. These current patterns 51 and 52 are formed in the inner printed wiring layers 45 and 46 of the printed circuit board 40, thus ensuring insulation from the main surfaces 41 and 42 of the printed circuit board 40. Furthermore, surface mount inductors L1, L2, L3, and L4 are mounted on the main surfaces 41 and 42 of the printed circuit board 40, opposite to the current patterns 51 and 52. The surface mount inductors L1, L2, L3, and L4 are configured such that their winding direction is oriented towards a predetermined direction 53 intersecting with the current patterns 51 and 52. That is, the current patterns 51 and 52 formed on the inner printed wiring layers 45 and 46 of the printed circuit board 40 and the surface mount inductors L1, L2, L3, and L4 mounted on the main surfaces 41 and 42 of the printed circuit board 40 are opposite each other in a state of electrical insulation through the insulating material (insulating substrate) of the printed circuit board 40, and the current patterns 51 and 52 intersect the winding directions of the surface mount inductors L1, L2, L3, and L4. Therefore, the magnetic flux formed by the current flowing in the current patterns 51 and 52 is linked with the windings of the surface mount inductors L1, L2, L3, and L4.

[0165] When the current flowing through current patterns 51 and 52 changes, causing a corresponding change in magnetic flux, the surface mount inductors L1, L2, L3, and L4 generate an electromotive force that suppresses the change in magnetic flux. A corresponding voltage appears between the two electrodes of the surface mount inductors L1, L2, L3, and L4. This voltage can be processed as a signal representing the change in current flowing through current patterns 51 and 52, in other words, representing the differential value of the current. Therefore, the surface mount inductors L1, L2, L3, and L4 function as sensors for directly detecting the differential value of the current, thus enabling high-speed detection of the differential current value without complex and time-consuming computational processing.

[0166] Multiple surface-mount inductors L1, L2, L3, and L4 are mounted on the main surfaces 41 and 42 of the printed circuit board 40 and are connected in series to form a series circuit 60. The midpoint 59 of this series circuit 60 is connected to a reference potential, i.e., ground potential, and the two ends of the series circuit 60 are connected to a pair of input terminals 70a and 70b of a differential amplifier circuit 70. A pair of load resistors R1 and R2 are connected between the two ends of the series circuit 60 and the midpoint 59, respectively.

[0167] The electromotive force generated by the surface-mount inductors L1, L2, L3, and L4 causes current to flow through the load resistors R1 and R2, resulting in a voltage drop. The corresponding signal is input to the differential amplifier circuit 70. By connecting the midpoint 59 of the series circuit 60 to ground (reference potential), the potential of the midpoint 59 remains unchanged even if the potential of the current patterns 51 and 52 changes significantly due to switching in the inverter 2. This suppresses the effects of switching and ensures a stable signal is input to the differential amplifier circuit 70.

[0168] The differential amplifier circuit 70 differentially amplifies the signals input to a pair of input terminals 70a and 70b, thus removing the in-phase components and amplifying the out-of-phase components. Since the noise component is in-phase, the differential amplifier circuit 70 can amplify and output the signal component with the noise component removed. Therefore, even if the differential current signals output from the surface mount inductors L1, L2, L3, and L4 are very small, the current differential can be detected with a good signal-to-noise ratio.

[0169] Therefore, the current supplied to the AC motor M from the inverter 2 can be detected directly (and thus at high speed) using a surface-mount inductor, and a signal that accurately represents the current derivative can be obtained. Consequently, the controller 1 can quickly and accurately estimate the rotor position of the AC motor M, thus achieving highly responsive and accurate motor control.

[0170] Furthermore, industrially produced surface mount inductors exhibit very small performance deviations, thus eliminating the need for individual adjustments even when using multiple surface mount inductors. Additionally, the extremely small size of surface mount inductors allows for the use of very compact structures for detecting current differentials.

[0171] The printed circuit board 40 can not only mount surface-mount inductors L1, L2, L3, and L4, but also some or all of the load resistors R1 and R2, differential amplifier circuit 70, inverter 2, and controller 1. This allows for the overall miniaturization of the motor control device 100. In other words, it can have a structure that both suppresses or prevents the motor control device 100 from becoming too large and can directly and accurately detect the differential current value.

[0172] Multiple surface-mount inductors L1, L2, L3, and L4 are connected in series, ensuring that the magnetic flux changes caused by the current flowing through current patterns 51 and 52 result in a consistent direction of the electromotive force induced in each inductor L1, L2, L3, and L4. Therefore, the sum of the electromotive forces generated by the multiple inductors L1, L2, L3, and L4 can be amplified by the differential amplifier circuit 70, thus obtaining a larger signal representing the current differential. Furthermore, because the characteristic deviations of each inductor L1, L2, L3, and L4 are averaged, the current differential value can be detected more accurately.

[0173] Furthermore, in this embodiment, the number of surface mount inductors L1, L2, L3, and L4 is even (2 in the first specific example and 4 in the second specific example). Therefore, the series circuit 60 of the surface mount inductors L1, L2, L3, and L4 can easily form a structure symmetrical about the midpoint 59, thus facilitating a balance of inputs to the pair of input terminals 70a and 70b of the differential amplifier circuit 70.

[0174] The controller 1 processes the output of the differential amplifier circuit 70 as the time derivative (current derivative) of the winding current of the AC motor M to estimate the rotor position. Specifically, the controller 1 calculates the inductance of each phase winding based on the time derivative (current derivative) of the winding current. The inductance of each phase winding changes periodically with the rotor position; therefore, the controller 1 can estimate the rotor position based on the inductance of each phase winding.

[0175] In the above embodiment, the same number of surface mount inductors L1, L2, L3, and L4 are mounted on two opposite main surfaces 41 and 42 of the printed circuit board 40. By mounting the same number of surface mount inductors L1, L2, L3, and L4 on one main surface 41 and the other main surface 42 of the printed circuit board 40, their series circuit 60 can easily form a structure symmetrical about the midpoint 59. Therefore, the input to the pair of input terminals 70a and 70b of the differential amplifier circuit 70 can easily be balanced.

[0176] Furthermore, by separately mounting multiple surface mount inductors L1, L2, L3, and L4 on one main surface 41 and another main surface 42 of the printed circuit board 40, the surface mount inductors can be configured in three dimensions, thereby enabling further miniaturization of the motor control device 100.

[0177] Furthermore, the magnetic flux generated by the currents flowing through current patterns 51 and 52 is in opposite directions on one main surface 41 and the other main surface 42 of the printed circuit board 40. Conversely, the magnetic flux generated externally, i.e., not caused by the currents flowing through wiring patterns 51 and 52, is in the same direction and has the same magnitude on one main surface 41 and the other main surface 42 of the printed circuit board 40. As described above, multiple surface mount inductors L1, L2, L3, and L4 are connected in series such that the direction of the electromotive force induced in each surface mount inductor L1, L2, L3, and L4 due to the change in magnetic flux generated by the currents flowing through current patterns 51 and 52 is consistent with that of the currents. In this case, the voltage appearing across the series circuit 60 of multiple surface mount inductors L1, L2, L3, and L4 is a value that superimposes the electromotive force generated in each surface mount inductor L1, L2, L3, and L4 according to the change in currents flowing through current patterns 51 and 52, and cancels out the electromotive force caused by the externally generated magnetic flux. Therefore, it is possible to suppress or prevent the influence of externally generated magnetic flux to detect the current differential.

[0178] In the first specific example described above, the number of surface mount inductors L1 and L2 arranged on one main surface 41 of the printed circuit board 40 is one, and the number arranged on the other main surface 42 is one. Furthermore, the surface mount inductor L1 on one main surface 41 and the surface mount inductor L2 on the other main surface 42 are geometrically symmetrically arranged with respect to the current patterns 51 and 52 through which the winding current flows. In other words, the distance from the current patterns 51 and 52 through which the winding current flows to the surface mount inductor L1 on one main surface 41 and the distance to the surface mount inductor L2 on the other main surface 42 are designed to be equal. Therefore, the input to the pair of input terminals 70a and 70b of the differential amplifier circuit 70 is easily balanced.

[0179] In the second specific example described above, two of the multiple surface mount inductors L1, L2, L3, and L4 are arranged on one main surface 41 of the printed circuit board 40, and two are arranged on the other main surface 42. Furthermore, one surface mount inductor L1 on one main surface 41 and one surface mount inductor L2 on the other main surface 42 are connected in series and positioned on one side of the midpoint 59, while the remaining two surface mount inductors L3 and L4 are connected in series and positioned on the other side of the midpoint 59, thereby connecting the four surface mount inductors L1, L2, L3, and L4 in series. Thus, the geometric arrangement of the surface mount inductors relative to the current pattern 52 through which the winding current flows (more specifically, the distance from the current pattern 52 to the surface mount inductors L1, L2, L3, and L4) is identical (symmetrical) on both sides of the midpoint 59 of the series circuit. Such a connection (configuration) is particularly effective when the surface mount inductors L1, L4 mounted on one main surface 41 and the surface mount inductors L2, L3 mounted on another main surface 42 are not equivalent (symmetrical) relative to the geometric configuration of the current pattern 52 (more specifically, the distance from the current pattern 52 to the surface mount inductors L1, L4; L2, L3 on each main surface).

[0180] In the above embodiment, the surface mount inductors L1, L2, L3, and L4 are air-core coils and are not shielded. By using air-core coil type surface mount inductors, current differentials can be detected without being affected by magnetic saturation. In addition, by using surface mount inductors with an unshielded structure, the magnetic flux formed by the current flowing through the wiring pattern can be detected with high sensitivity.

[0181] In the above embodiment, the multiple surface mount inductors L1, L2, L3, and L4 are of the same specification. By using surface mount inductors of the same specification, it is easy to form a series circuit 60 with a symmetrical structure centered on the midpoint 59. Industrially produced surface mount inductors of the same specification have the same performance, so no substantial adjustments are required during use.

[0182] The above describes one embodiment of the present invention, but the present invention can also be implemented in other ways, and various design changes can be made within the scope of the claims.

[0183] For example, in the above embodiments, a first example using two surface mount inductors L1 and L2, and a second example using four surface mount inductors L1, L2, L3, and L4, were described as the structure of the current differential detector 4uvw. However, the number of surface mount inductors used for detecting current differentials is not limited to these. As mentioned above, the number of surface mount inductors is preferably even. Furthermore, it is preferable that the even number of surface mount inductors are arranged in the same number on the two main surfaces 41 and 42 of the printed circuit board 40.

[0184] Furthermore, in the above embodiment, an example is shown where the surface mount inductors disposed on the two main surfaces of the printed circuit board 40 are arranged in pairs and opposite to each other. However, the surface mount inductors only need to be opposite to the current patterns 51 and 52, and the surface mount inductors disposed on the two main surfaces 41 and 42 of the printed circuit board 40 can also be staggered when viewed perpendicular to the main surfaces 41 and 42.

[0185] Furthermore, in the above embodiments, a first example was described in which current patterns 51 and 52 are formed in two inner printed wiring layers 45 and 46 of the printed circuit board 40, and a second example was described in which current patterns are formed in one inner printed wiring layer 46 of the printed circuit board 40. However, a multilayer printed circuit board with more printed wiring layers may also be used, and current patterns may be arranged in three or more inner printed wiring layers. The current pattern does not necessarily have to be a straight strip; it may also be a shape that includes curved portions or bends.

[0186] Label Explanation

[0187] 1: Controller

[0188] 2: Inverter

[0189] 3u, 3v, 3w: Current detector

[0190] 4u, 4v, 4w: Current Differential Detector

[0191] 5u, 5v, 5w: windings

[0192] 9u, 9v, 9w: Current circuit

[0193] 11: Position Controller

[0194] 12: Speed ​​Controller

[0195] 13: Current Controller

[0196] 14: PWM Generator

[0197] 15: Position estimator

[0198] 16: Velocity estimator

[0199] 40: Printed substrate

[0200] 41, 42: Main side

[0201] 43, 44: Outer printed wiring layer

[0202] 45, 46: Inner printed wiring layer

[0203] 47, 48, 49: Insulation layer

[0204] 51, 52: Current Patterns

[0205] 53: Prescribed direction

[0206] 60: Series circuit

[0207] 70: Differential amplifier circuit

[0208] 70a, 70b: Input terminals

[0209] 100: Electric motor control device

[0210] 121: Test Pulse

[0211] 122: Cancellation Pulse

[0212] L1~L4: Surface mount inductors

[0213] M: AC motor

[0214] R1, R11, R12: Load resistors

[0215] R2, R21, R22: Load resistors.

Claims

1. A motor control device for controlling an AC motor by sensorless control without using a rotor position detector, characterized in that, include: An inverter that converts DC to AC based on pulse width modulation signals; A multilayer printed circuit board having a wiring pattern in the inner layer that is inserted into current lines connecting the windings of the inverter and the AC motor. Multiple surface mount inductors are mounted on the main surface of the multilayer printed circuit board such that the winding direction is oriented toward a predetermined direction intersecting with and opposite to the wiring pattern, and the multiple surface mount inductors are connected in series to form a series circuit having a midpoint connected to a reference potential. The load resistor is connected between the midpoint of the series circuit and the two ends of the series circuit. A differential amplifier circuit, wherein a pair of input terminals of the differential amplifier circuit are connected to the two ends of the series circuit; as well as The control unit uses the output of the differential amplifier circuit to estimate the position of the rotor of the AC motor, and generates a pulse width modulation signal for the inverter based on the estimated rotor position.

2. The motor control device as described in claim 1, characterized in that, The multiple surface mount inductors are connected in series so that the direction of the electromotive force induced in each surface mount inductor due to the change in magnetic flux caused by the current flowing through the wiring pattern is consistent.

3. The motor control device as described in claim 1 or 2, characterized in that, The total number of the plurality of surface mount inductors is an even number.

4. The motor control device as described in claim 1 or 2, characterized in that, The control unit is configured to process the output of the differential amplifier circuit as a value equivalent to the time derivative of the winding current of the AC motor to estimate the position of the rotor.

5. The motor control device as described in claim 1 or 2, characterized in that, The plurality of surface mount inductors are mounted in the same number on two opposite main surfaces of the multilayer printed circuit board.

6. The motor control device as described in claim 1 or 2, characterized in that, The plurality of surface mount inductors are configured in a quantity of 1 on one main surface of the multilayer printed circuit board and in a quantity of 1 on another main surface opposite to the one main surface.

7. The motor control device as described in claim 6, characterized in that, The distance from the wiring pattern to one of the surface mount inductors on one main side of the multilayer printed circuit board and the distance from the wiring pattern to another surface mount inductor on the other main side are designed to be equal to each other.

8. The motor control device as described in claim 1 or 2, characterized in that, The plurality of surface mount inductors are arranged in a quantity of 2 on one main surface of the multilayer printed circuit board and in a quantity of 2 on another main surface opposite to the one main surface.

9. The motor control device as described in claim 8, characterized in that, One of the surface mount inductors on one main surface of the multilayer printed circuit board is connected in series with one of the surface mount inductors on another main surface and is positioned on one side of the midpoint. The other two surface mount inductors are connected in series and positioned on the other side of the midpoint, thereby forming a series circuit of four surface mount inductors.

10. The motor control device as described in claim 1 or 2, characterized in that, The surface mount inductor is an air-core coil and is not shielded.

11. The motor control device as described in claim 1 or 2, characterized in that, The multiple surface mount inductors have the same specifications.

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