Motor control device

Abstract

To reduce the number of connection lines for voltage detection while enabling detection of both end voltages of all switching elements of an inverter circuit for driving a three phase motor.SOLUTION: At least one of the high-potential-side connection line 30 and the low-potential-side connection line 32 is shared for detecting the voltages across the plurality of high-potential-side switching elements 24HU, 24HV, and 24HW and / or the plurality of low-potential-side switching elements 24LU, 24LV, and 24LW. Then, when the voltage corresponding to the voltage across the high-potential-side switching element and / or the low-potential-side switching element detected using the shared high-potential-side connection line 30 and / or low-potential-side connection line 32 deviates from the voltage across the high-potential-side switching element and / or the low-potential-side switching element, the voltage correcting unit 46 corrects the corresponding voltage to the voltage corresponding to the voltage across the high-potential-side switching element and / or the low-potential-side switching element.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a motor control device that controls the driving of a three-phase motor via an inverter circuit. [Background technology]

[0002] For example, Patent Document 1 describes a motor drive circuit that uses the on-resistance of a switching element used in an inverter circuit as an alternative to a current sensor to detect the current flowing through the switching element.

[0003] In the motor drive circuit of Patent Document 1, the drain and source sides of each switching element are connected to an amplifier via connection lines, and the voltages amplified by the amplifier are sampled by a sample-and-hold circuit at the timing when a forward voltage occurs when a freewheeling current flows through the freewheeling diode and when a voltage drop occurs due to the on-resistance of the switching element. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-50711 Summary of the Invention [Problem to be solved by the invention]

[0005] If the configuration described in Patent Document 1 is used to detect voltage drops due to on-resistance for all switching elements of an inverter circuit that drives a three-phase motor, two connection wires are required for each switching element, resulting in a large number of connection wires. As a result, the routing of the connection wires becomes complicated, and if the connection wires are wired on a wiring board, this may increase the design cost of the board and the size of the board.

[0006] The present disclosure has been made in consideration of the above points, and aims to provide a motor control device that is capable of detecting the voltages across all switching elements of an inverter circuit that drives a three-phase motor, while reducing the number of connection lines for voltage detection. [Means for solving the problem]

[0007] In order to achieve the above object, a motor control device (100) according to the present disclosure is a motor control device that controls driving of a three-phase motor (50) via an inverter circuit (20), The inverter circuit has upper and lower arm circuits (22U, 22V, 22W) for three phases, each of which is connected in series with an upper arm circuit (22HU, 22HV, 22HW) including high-potential side switching elements (24HU, 24HV, 24HW) and high-potential side freewheel diodes (26HU, 26HV, 26HW), and a lower arm circuit (22LU, 22LV, 22LW) including low-potential side switching elements (24LU, 24LV, 24LW) and low-potential side freewheel diodes (26LU, 26LV, 26LW), corresponding to each phase of the three-phase motor; a voltage detection unit (44) for detecting voltages corresponding to the voltages across each of the high-potential side switching element and the low-potential side switching element; a high potential side connection line (30) that connects the high potential side of each high potential side switching element of the three phase upper arm circuits to a voltage detection unit; a low potential side connection line (32) that connects the low potential side of each low potential side switching element of the three phase lower arm circuits to the voltage detection unit; and opposite-side connection lines (34U, 34V, 34W) that connect the opposite side of the high potential side of the high potential side switching element and the opposite side of the low potential side of the low potential side switching element of each of the upper and lower arm circuits for three phases to the voltage detection unit, the voltage detection unit detects a voltage corresponding to the voltage across the high potential side switching element from a potential difference between the potential of the high potential side connecting line and the potential of the opposite side connecting line, and detects a voltage corresponding to the voltage across the low potential side switching element from a potential difference between the potential of the low potential side connecting line and the potential of the opposite side connecting line; At least one of the high potential side connecting line and the low potential side connecting line is shared for detecting voltages across the multiple high potential side switching elements and / or the multiple low potential side switching elements, The inverter further includes a voltage correction unit (46) that corrects a voltage corresponding to the voltage across the high-potential side switching element and / or the low-potential side switching element, detected using the shared high-potential side connecting line and / or the low-potential side connecting line, to a voltage equivalent to the voltage across the high-potential side switching element and / or the low-potential side switching element, depending on the connection positions of the shared high-potential side connecting line and / or the low-potential side connecting line to the plurality of high-potential side switching elements and / or the plurality of low-potential side switching elements and the paths through which the motor current and the return current flow in the upper and lower arm circuits for three phases.

[0008] As described above, in the motor control device according to the present disclosure, at least one of the high-side connection line and the low-side connection line is shared for detecting the voltages across multiple high-side switching elements and / or multiple low-side switching elements, which makes it possible to detect the voltages across all switching elements included in the inverter circuit while reducing the number of connection lines connecting to the voltage detection unit.

[0009] Here, when at least one of the high-potential side connecting line and the low-potential side connecting line is shared for detecting the voltages across multiple high-potential side switching elements and / or multiple low-potential side switching elements, depending on the connection positions of the shared high-potential side connecting line and / or low-potential side connecting line to the multiple high-potential side switching elements and / or multiple low-potential side switching elements and the paths through which the motor current and the return current flow in the three-phase upper and lower arm circuits, it is possible that the voltage corresponding to the voltages across the high-potential side switching elements and / or low-potential side switching elements detected using the shared high-potential side connecting line and / or low-potential side connecting line may deviate from the voltages across the high-potential side switching elements and / or low-potential side switching elements.

[0010] In this regard, the motor control device according to the present disclosure includes a voltage correction unit, and when a voltage corresponding to the voltage across a high-side switching element and / or a low-side switching element detected using a shared high-side connecting line and / or a low-side connecting line deviates from the voltage across the high-side switching element and / or the low-side switching element, the voltage correction unit corrects the corresponding voltage to a voltage equivalent to the voltage across the high-side switching element and / or the low-side switching element. This makes it possible to accurately detect the voltage across the high-side switching element and / or the low-side switching element even when at least one of the high-side connecting line and the low-side connecting line is shared for detecting the voltage across multiple high-side switching elements and / or multiple low-side switching elements.

[0011] The reference numbers in parentheses above merely indicate an example of a correspondence with specific configurations in the embodiments described below, in order to facilitate understanding of the present disclosure, and are not intended to limit the scope of the present disclosure in any way.

[0012] Furthermore, the technical features of the present disclosure other than those described above will become apparent from the following description of the embodiments and the accompanying drawings. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a configuration diagram showing an example of the configuration of a motor control device according to an embodiment; [Figure 2] 10 is an explanatory diagram for explaining why the voltage detected using the shared high-potential side connecting line and low-potential side connecting line deviates from the voltage across the high-potential side switching element and the low-potential side switching element. FIG. [Figure 3] 10 is a diagram showing a first case in which the voltage detected using the shared high potential side connecting line and low potential side connecting line deviates from the voltage across the high potential side switching element and the low potential side switching element. FIG. [Figure 4]10 is a diagram showing a second case in which the voltage detected using the shared high potential side connecting line and low potential side connecting line deviates from the voltage across the high potential side switching element and the low potential side switching element. FIG. [Figure 5] FIG. 10 is a diagram showing a third case in which the voltage detected using the shared high-potential side connecting line and low-potential side connecting line does not deviate from the voltage across the high-potential side switching element and the low-potential side switching element. [Figure 6] 10 is a diagram showing a fourth case in which the voltage detected using the shared high potential side connecting line and low potential side connecting line deviates from the voltage across the high potential side switching element and the low potential side switching element. FIG. [Figure 7] FIG. 10 is a diagram showing a fifth case in which the voltage detected using the shared high potential side connecting line and low potential side connecting line deviates from the voltage across the high potential side switching element and the low potential side switching element. [Figure 8] FIG. 10 is a diagram showing a sixth case in which the voltage detected using the shared high potential side connecting line and low potential side connecting line does not deviate from the voltage across the high potential side switching element and the low potential side switching element. [Figure 9] FIG. 10 is a diagram showing a state in which only the UV-phase motor current flows through the inverter circuit after the reflux current has disappeared. [Figure 10] FIG. 10 is a diagram for explaining an example of a method for determining whether or not a reflux current is occurring. [Figure 11] 11 is a diagram for explaining, together with FIG. 10, an example of a method for determining whether or not a reflux current is occurring. [Figure 12] 10 is a flowchart illustrating an example of a process executed by a microcomputer to calculate a current value from a voltage across each switching element. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of a motor control device according to the present disclosure will be described with reference to the drawings. However, the present disclosure is not limited to the following embodiments, and various modifications described below are also included within the technical scope of the present disclosure. Furthermore, in addition to the following, various modifications can be implemented without departing from the spirit of the present disclosure. The embodiments and various modifications can be implemented in appropriate combinations as long as no technical contradictions arise. In the following description, identical or similar components may be assigned the same reference numerals across multiple drawings, and their description may be omitted. Furthermore, when only a portion of a component is mentioned, the description provided elsewhere may apply to the other components.

[0015] (First embodiment) Fig. 1 is a diagram showing an example of the configuration of a motor control device 100 according to this embodiment. As shown in Fig. 1, the motor control device 100 includes an inverter circuit 20, a microcomputer 40, etc. The motor control device 100 controls the driving of a three-phase motor 50 via the inverter circuit 20.

[0016] The three-phase motor 50 to be controlled by the motor control device 100 is, for example, a three-phase brushless motor. The three-phase brushless motor includes a stator having three-phase (U, V, and W) windings connected in a Y-connection, and a rotor to which a permanent magnet is attached. The three-phase windings of the three-phase brushless motor may be connected in a delta-connection instead of a Y-connection. The three-phase motor 50 is provided with a rotational position sensor using, for example, a Hall element or a resolver to detect the rotational position of the rotor. However, the rotational position of the rotor may also be detected based on an induced voltage induced in a winding of a non-energized phase among the three-phase windings.

[0017] The inverter circuit 20 is supplied with a DC power supply voltage from a DC power supply 10. The inverter circuit 20 is a DC-AC conversion circuit. The inverter circuit 20 converts the DC voltage into a three-phase AC voltage by turning on and off the switching elements 24HU, 24HV, 24HW, 24LU, 24LV, and 24LW in accordance with switching control (e.g., PWM control) by an energization control unit 42 of a microcomputer 40. The converted AC voltage is output to a three-phase motor 50. This drives and rotates the three-phase motor 50.

[0018] The inverter circuit 20 includes upper and lower arm circuits 22U, 22V, and 22W for three phases. Each of the upper and lower arm circuits 22U, 22V, and 22W includes upper arm circuits 22HU, 22HV, and 22HW and lower arm circuits 22LU, 22LV, and 22LW. The upper arm circuits 22HU, 22HV, and 22HW and the lower arm circuits 22LU, 22LV, and 22LW are connected in series between the high potential line 12 and the low potential line 14, with the upper arm circuits 22HU, 22HV, and 22HW on the high potential line 12 side and the lower arm circuits 22LU, 22LV, and 22LW on the low potential line 14 side.

[0019] The upper arm circuits 22HU, 22HV, and 22HW each include a high-side switching element 24HU, 24HV, or 24HW and a high-side freewheeling diode 26HU, 26HV, or 26HW. The lower arm circuits 22LU, 22LV, and 22LW each include a low-side switching element 24LU, 24LV, or 24LW and a low-side freewheeling diode 26LU, 26LV, or 26LW. The number of high-side switching elements 24HU, 24HV, or 24HW and low-side switching elements 24LU, 24LV, or 24LW in each of the upper arm circuits 22HU, 22HV, or 22HW and the lower arm circuits 22LU, 22LV, or 22LW is not particularly limited and may be one or more. When multiple switching elements are provided, the multiple switching elements may be connected in parallel with each other. The plurality of switching elements connected in parallel can be turned on and off at the same timing by a common gate drive signal.

[0020] The high-side switching elements 24HU, 24HV, and 24HW and the low-side switching elements 24LU, 24LV, and 24LW illustrated in Fig. 1 are all n-channel MOSFETs. MOSFET is an abbreviation for Metal Oxide Semiconductor Field Effect Transistor. As shown in Fig. 1, the drains of the MOSFETs in the upper arm circuits 22HU, 22HV, and 22HW are connected to a high-potential line 12. The sources of the MOSFETs in the lower arm circuits 22LU, 22LV, and 22LW are connected to a low-potential line 14. The sources of the MOSFETs in the upper arm circuits 22HU, 22HV, and 22HW and the drains of the MOSFETs in the lower arm circuits 22LU, 22LV, and 22LW are connected to each other.

[0021] The high-side freewheeling diodes 26HU, 26HV, and 26HW are connected in anti-parallel to the MOSFETs that are the high-side switching elements 24HU, 24HV, and 24HW. That is, the anodes of the high-side freewheeling diodes 26HU, 26HV, and 26HW are connected to the sources of the corresponding high-side switching elements 24HU, 24HV, and 24HW, and the cathodes are connected to the drains. The low-side freewheeling diodes 26LU, 26LV, and 26LW are also connected in anti-parallel to the MOSFETs that are the low-side switching elements 24LU, 24LV, and 24LW. The high-side freewheeling diodes 26HU, 26HV, and 26HW and the low-side freewheeling diodes 26LU, 26LV, and 26LW may be parasitic diodes (body diodes) of the MOSFETs or external diodes.

[0022] The high-side switching elements 24HU, 24HV, and 24HW and the low-side switching elements 24LU, 24LV, and 24LW are not limited to MOSFETs. For example, IGBTs may be used as the high-side switching elements 24HU, 24HV, and 24HW and the low-side switching elements 24LU, 24LV, and 24LW. IGBT stands for Insulated Gate Bipolar Transistor. Even when IGBTs are used, freewheeling diodes are connected in anti-parallel to the high-side switching elements 24HU, 24HV, and 24HW and the low-side switching elements 24LU, 24LV, and 24LW, respectively.

[0023] In each of the upper and lower arm circuits 22U, 22V, and 22W, the connection points between the upper arm circuits 22HU, 22HV, and 22HW and the lower arm circuits 22LU, 22LV, and 22LW, i.e., the midpoints of the upper and lower arm circuits 22U, 22V, and 22W, are connected to the corresponding phase windings of the motor 50 via output lines 28U, 28V, and 28W, respectively. More specifically, of the upper and lower arm circuits 22U, 22V, and 22W, the midpoint of the upper and lower arm circuit 22U corresponding to the U phase of the three-phase motor 50 is connected to the U phase winding of the three-phase motor 50 via output line 28U. The midpoint of the upper and lower arm circuit 22V corresponding to the V phase of the three-phase motor 50 is connected to the V phase winding of the three-phase motor 50 via output line 28V. The midpoint of the upper and lower arm circuit 22W corresponding to the W phase of the three-phase motor 50 is connected to the W phase winding of the three-phase motor 50 via output line 28W.

[0024] The high-side switching elements 24HU, 24HV, and 24HW, the high-side freewheeling diodes 26HU, 26HV, and 26HW, the low-side switching elements 24LU, 24LV, and 24LW, and the low-side freewheeling diodes 26LU, 26LV, and 26LW of the upper and lower arm circuits 22U, 22V, and 22W constituting the inverter circuit 20 described above may be mounted on a common substrate. In this case, the high-side line 12, the low-side line 14, and the output lines 28U, 28V, and 28W are wired to the substrate. Furthermore, drive signal transmission lines for transmitting drive signals from the microcomputer 40 to the high-side switching elements 24HU, 24HV, and 24HW and the low-side switching elements 24LU, 24LV, and 24LW are wired to the substrate. Additionally, the substrate is provided with a high-potential-side connection line 30 that connects the high-potential sides of the high-potential-side switching elements 24HU, 24HV, 24HW of the upper arm circuits 22HU, 22HV, 22HW to a voltage detection unit 44 (described later), and a low-potential-side connection line 32 that connects the low-potential sides of the low-potential-side switching elements 24LU, 24LV, 24LW of the lower arm circuits 22LU, 22LV, 22LW to the voltage detection unit 44. Additionally, the substrate is provided with opposite-side connection lines 34U, 34V, 34W that connect the sides opposite the high-potential sides of the high-potential-side switching elements 24HU, 24HV, 24HW of the upper and lower arm circuits 22U, 22V, 22W and the sides opposite the low-potential sides of the low-potential-side switching elements 24LU, 24LV, 24LW, i.e., the midpoints of the upper and lower arm circuits 22U, 22V, 22W to the voltage detection unit 44. In this way, a large number of lines and connecting wires are wired on the board, and therefore, the greater the number of connecting wires, the greater the risk of increased board design costs and larger board sizes.

[0025] The microcomputer 40 may be configured, for example, by a computer having a processor and memory. The microcomputer 40 performs various functions by the processor executing programs stored in the memory. The microcomputer 40 also has hardware such as an amplifier, an AD converter, and an I / F circuit. Figure 1 shows various functional units configured in the microcomputer 40 by software and / or hardware.

[0026] As shown in FIG. 1 , the microcomputer 40 includes, as functional units, a conduction control unit 42, a voltage detection unit 44, a voltage correction unit 46, and a current calculation unit 48. The conduction control unit 42 controls the on / off states of the high-side switching elements 24HU, 24HV, and 24HW and the low-side switching elements 24LU, 24LV, and 24LW of the inverter circuit 20. The conduction control unit 42 includes a drive circuit that outputs drive signals to the high-side switching elements 24HU, 24HV, and 24HW and the low-side switching elements 24LU, 24LV, and 24LW of the inverter circuit 20. The conduction control unit 42 outputs, for example, a PWM signal as the drive signal. The high-side switching elements 24HU, 24HV, and 24HW and the low-side switching elements 24LU, 24LV, and 24LW of the inverter circuit 20 are turned on or off in response to the drive signals output from the conduction control unit 42.

[0027] The current control unit 42 generates and outputs drive signals for the plurality of high-potential side switching elements 24HU, 24HV, 24HW and the plurality of low-potential side switching elements 24LU, 24LV, 24LW of the inverter circuit 20, based on, for example, a target torque or a target rotation speed input from a higher-level ECU (not shown) and detection signals detected by various sensors. The various sensors include the rotation position sensor described above.

[0028] The current control unit 42 also has an overcurrent protection function that stops switching control of the inverter circuit 20 when the value of the current flowing through each of the high potential side switching elements 24HU, 24HV, 24HW and each of the low potential side switching elements 24LU, 24LV, 24LW of the inverter circuit 20, calculated by the current calculation unit 48, exceeds a predetermined value. When the switching control is stopped by the overcurrent protection function, each of the high potential side switching elements 24HU, 24HV, 24HW and each of the low potential side switching elements 24LU, 24LV, 24LW of the inverter circuit 20 is turned off.

[0029] The voltage detection unit 44 detects voltages corresponding to the voltages across each of the high potential side switching elements 24HU, 24HV, 24HW and each of the low potential side switching elements 24LU, 24LV, 24LW of the inverter circuit 20. The voltage detection unit 44 is configured to include, for example, a plurality of differential amplifiers. The plurality of differential amplifiers are provided individually for the plurality of high potential side switching elements 24HU, 24HV, 24HW and the plurality of low potential side switching elements 24LU, 24LV, 24LW.

[0030] The potential of the high potential side connecting line 30 and the potential of the opposite side connecting lines 34U, 34V, and 34W are input to the differential amplifiers provided for the multiple high potential side switching elements 24HU, 24HV, and 24HW, respectively. As a result, each differential amplifier provided for the multiple high potential side switching elements 24HU, 24HV, and 24HW outputs a voltage corresponding to the potential difference between the potential of the high potential side connecting line 30 and the potential of each of the opposite side connecting lines 34U, 34V, and 34W. In addition, the potential of the low potential side connecting line 32 and the potential of the opposite side connecting lines 34U, 34V, and 34W are input to the differential amplifiers provided for the multiple low potential side switching elements 24LU, 24LV, and 24LW, respectively. As a result, each differential amplifier provided for the plurality of low potential side switching elements 24LU, 24LV, 24LW outputs a voltage corresponding to the potential difference between the potential of the low potential side connection line 32 and the potential of each of the opposite side connection lines 34U, 34V, 34W.

[0031] As described above, in the motor control device 100 according to this embodiment, rather than individually connecting the drain and source sides of the high-side switching elements 24HU, 24HV, and 24HW and the low-side switching elements 24LU, 24LV, and 24LW of the inverter circuit 20 to the voltage detection unit 44, the drain sides (high potential sides) of the three high-side switching elements 24HU, 24HV, and 24HW are connected to the voltage detection unit 44 using a common high-side connecting line 30. Furthermore, in the motor control device 100 according to this embodiment, the source sides (low potential sides) of the three low-side switching elements 24LU, 24LV, and 24LW are connected to the voltage detection unit 44 using a common low-side connecting line 32. In other words, in the motor control device 100 according to this embodiment, the high-side connecting line 30 and the low-side connecting line 32 are shared for detecting the voltages across the multiple high-side switching elements 24HU, 24HV, and 24HW and the multiple low-side switching elements 24LU, 24LV, and 24LW. Therefore, it is possible to detect the voltages across all of the high-side switching elements 24HU, 24HV, 24HW and low-side switching elements 24LU, 24LV, 24LW included in the inverter circuit 20, while reducing the number of connection lines connecting to the voltage detection unit 44.

[0032] Furthermore, in the motor control device 100 according to this embodiment, the opposite-side connecting wires 34U, 34V, 34W are shared for detecting the voltages across the high-potential side switching elements 24HU, 24HV, 24HW and the low-potential side switching elements 24LU, 24LV, 24LW in each of the upper and lower arm circuits 22U, 22V, 22W, thereby further reducing the number of connecting wires connecting to the voltage detection unit 44.

[0033] Here, when the high potential side connection line 30 and the low potential side connection line 32 are shared to detect the voltages across the multiple high potential side switching elements 24HU, 24HV, 24HW and the multiple low potential side switching elements 24LU, 24LV, 24LW, the connection positions of the shared high potential side connection line 30 and the low potential side connection line 32 to the multiple high potential side switching elements 24HU, 24HV, 24HW and the multiple low potential side switching elements 24LU, 24LV, 24LW and the upper and lower terminals of the inverter circuit 20 for three phases are Depending on the paths through which the motor current and the return current flow in the arm circuits 22U, 22V, 22W, the voltages corresponding to the voltages across the high-side switching elements 24HU, 24HV, 24HW and the low-side switching elements 24LU, 24LV, 24LW detected using the shared high-side connecting line 30 and low-side connecting line 32 may deviate from the voltages across the high-side switching elements 24HU, 24HV, 24HW and the low-side switching elements 24LU, 24LV, 24LW.

[0034] Below, we will explain in detail with reference to the drawings why the voltage detected using the shared high-potential side connecting line 30 and low-potential side connecting line 32 deviates from the voltage across the high-potential side switching elements 24HU, 24HV, 24HW and the low-potential side switching elements 24LU, 24LV, 24LW.

[0035] 2 shows a state in which motor current flows through U-phase high potential side switching element 24HU, the U-phase winding of three-phase motor 50, the V-phase winding of three-phase motor 50, and V-phase low potential side switching element 24LV, and reflux current flows through the V-phase winding of three-phase motor 50, the V-phase low potential side switching element 24LV, the W-phase low potential side reflux diode 26LW, and the W-phase winding of three-phase motor 50. This state may occur immediately after energization of three-phase motor 50 is switched from WV-phase energization to UV-phase energization. In the example shown in FIG. 2, the connection position of low potential side connecting wire 32 is the source side (low potential side) of low potential side switching element 24LW of W-phase lower arm circuit 22LW.

[0036] 2, the differential amplifier corresponding to the V-phase low potential side switching element 24LV of the voltage detection unit 44 outputs a voltage corresponding to the potential difference between the low potential side connecting wire 32 and the V-phase opposite connecting wire 34V. However, as shown in FIG. 2, a return current path through which a return current flows but no motor current flows is included between the connection point of the V-phase low potential side switching element 24LV and the low potential side connecting wire 32. Therefore, the voltage output by the differential amplifier corresponding to the V-phase low potential side switching element 24LV includes not only the voltage across both ends generated by the on resistance of the V-phase low potential side switching element 24LV due to the motor current and return current flowing through the V-phase low potential side switching element 24LV, but also a voltage corresponding to a voltage drop generated by the wiring resistance of the return current path due to the return current flowing through the return current path (the excess voltage in FIG. 2).

[0037] In other words, if a return current path through which a return current flows but no motor current flows is included between the connection position of the high-side switching elements 24HU, 24HV, 24HW or low-side switching elements 24LU, 24LV, 24LW, whose end-to-end voltage is to be detected, and the connection position of the shared high-side connecting line 30 or low-side connecting line 32, the voltage output by the differential amplifier corresponding to the high-side switching elements 24HU, 24HV, 24HW or low-side switching elements 24LU, 24LV, 24LW, whose end-to-end voltage is to be detected, will deviate from the end-to-end voltage of the high-side switching elements 24HU, 24HV, 24HW or low-side switching elements 24LU, 24LV, 24LW, whose end-to-end voltage is to be detected, by the voltage drop caused by the wiring resistance of the return current path.

[0038] Such a deviation between the voltage output by the differential amplifier and the voltage across the high-side switching elements 24HU, 24HV, 24HW or the low-side switching elements 24LU, 24LV, 24LW, the voltages of which are the detection targets, may or may not occur depending on the connection positions of the shared high-side connecting line 30 and the low-side connecting line 32 relative to the multiple high-side switching elements 24HU, 24HV, 24HW and the multiple low-side switching elements 24LU, 24LV, 24LW, and the paths of the motor current and the return current in the three-phase upper and lower arm circuits 22U, 22V, 22W of the inverter circuit 20. Below, using a case where a three-phase motor 50 is energized with a 120-degree rectangular wave as an example, cases where a deviation occurs and cases where a deviation does not occur between the voltage output by the corresponding differential amplifier and the voltage across the high-side switching elements 24HU, 24HV, 24HW or the low-side switching elements 24LU, 24LV, 24LW, the voltages of which are the detection targets, will be described. The motor control device 100 of this embodiment is not limited to 120-degree rectangular wave energization, and can also energize the three-phase motor 50 using other energization methods. Examples of other energization methods include rectangular wave energization with overlapping energization that energizes multiple phases before and after switching the energized phase when the energized phase is switched, and 180-degree sine wave energization. In short, the motor control device 100 of this embodiment can employ any energization method that can generate a reflux current.

[0039] 3 shows a state in which the energization of the three-phase motor 50 is switched from WV-phase energization to UV-phase energization. In this first case, as described above, a return current path through which a return current flows but no motor current flows is included between the V-phase low potential side switching element 24LV and the connection position of the low potential side connecting wire 32. For this reason, in the first case of FIG. 3, a discrepancy occurs between the voltage output by the differential amplifier corresponding to the V-phase low potential side switching element 24LV and the voltage across the V-phase low potential side switching element 24LV.

[0040] 4 shows a state in which the energization of the three-phase motor 50 is switched from UV-phase energization to UW-phase energization. In this second case, motor current flows through the U-phase high potential side switching element 24HU, the U-phase winding of the three-phase motor 50, the W-phase winding of the three-phase motor 50, and the W-phase low potential side switching element 24LW. Furthermore, freewheeling current flows through the V-phase winding of the three-phase motor 50, the V-phase high potential side freewheeling diode 26HV, the U-phase high potential side switching element 24HU, and the U-phase winding of the three-phase motor 50. Furthermore, in the example shown in FIG. 4, the connection position of the high potential side connecting wire 30 is the drain side (high potential side) of the high potential side switching element 24HW of the W-phase upper arm circuit 22HW.

[0041] In the second case of Fig. 4, a return current flows in high potential line 12 between V-phase upper arm circuit 22HV and U-phase upper arm circuit 22HU, but no motor current flows. Therefore, also in the case of Fig. 4, a return current path through which no motor current flows but a return current flows is included between U-phase high potential side switching element 24HU and the connection position of high potential side connecting wire 30. As a result, also in the second case of Fig. 4, a discrepancy occurs between the voltage output by the differential amplifier corresponding to U-phase high potential side switching element 24HU and the voltage across U-phase high potential side switching element 24HU.

[0042] 5 shows a state in which the energization of the three-phase motor 50 is switched from UW-phase energization to VW-phase energization. In this case, motor current flows through the V-phase high potential side switching element 24HV, the V-phase winding of the three-phase motor 50, the W-phase winding of the three-phase motor 50, and the W-phase low potential side switching element 24LW. Also, freewheeling current flows through the W-phase winding of the three-phase motor 50, the W-phase low potential side switching element 24LW, the U-phase low potential side freewheeling diode 26LU, and the U-phase winding of the three-phase motor 50.

[0043] 5, both the motor current and the return current flow through the path from the source side of the W-phase low potential side switching element 24LW to the connection position of the low potential side connecting wire 32. Therefore, in the third case of Fig. 5, no motor current flows between the W-phase low potential side switching element 24LW and the connection position of the low potential side connecting wire 32, and no return current path through which return current flows is included. Therefore, in the third case of Fig. 5, no deviation occurs between the voltage output by the differential amplifier corresponding to the W-phase low potential side switching element 24LW and the voltage across the W-phase low potential side switching element 24LW.

[0044] 6 shows a state in which the energization of the three-phase motor 50 is switched from VW-phase energization to VU-phase energization. In this fourth case, motor current flows through the V-phase high potential side switching element 24HV, the V-phase winding of the three-phase motor 50, the U-phase winding of the three-phase motor 50, and the U-phase low potential side switching element 24LU. Also, freewheeling current flows through the W-phase winding of the three-phase motor 50, the W-phase high potential side freewheeling diode 26HW, the V-phase high potential side switching element 24HV, and the V-phase winding of the three-phase motor 50.

[0045] In the fourth case of Fig. 6, a return current flows in the high potential line 12 between the W-phase upper arm circuit 22HW and the V-phase upper arm circuit 22HV, but no motor current flows. Therefore, in the case of Fig. 6, a return current path through which a return current flows but no motor current flows is included between the V-phase high potential side switching element 24HV and the connection position of the high potential side connecting wire 30. As a result, in the fourth case of Fig. 6, a discrepancy occurs between the voltage output by the differential amplifier corresponding to the V-phase high potential side switching element 24HV and the voltage across the V-phase high potential side switching element 24HV.

[0046] 7 shows a state in which the energization of the three-phase motor 50 is switched from VU-phase energization to WU-phase energization. In this fifth case, motor current flows through the W-phase high potential side switching element 24HW, the W-phase winding of the three-phase motor 50, the U-phase winding of the three-phase motor 50, and the U-phase low potential side switching element 24LU. Also, freewheeling current flows through the U-phase winding of the three-phase motor 50, the U-phase low potential side switching element 24LU, the V-phase low potential side freewheeling diode 26LV, and the V-phase winding of the three-phase motor 50.

[0047] In the fifth case of Fig. 7, a return current flows in low potential line 14 between U-phase lower arm circuit 22LU and V-phase lower arm circuit 22LV, but no motor current flows. Therefore, also in the case of Fig. 7, a return current path through which no motor current flows but a return current flows is included between U-phase low potential side switching element 24LU and the connection position of low potential side connecting line 32. As a result, also in the fifth case of Fig. 7, a deviation occurs between the voltage output by the differential amplifier corresponding to U-phase low potential side switching element 24LU and the voltage across U-phase low potential side switching element 24LU.

[0048] 8 shows a state in which the energization of the three-phase motor 50 is switched from WU-phase energization to WV-phase energization. In this case, motor current flows through the W-phase high potential side switching element 24HW, the W-phase winding of the three-phase motor 50, the V-phase winding of the three-phase motor 50, and the V-phase low potential side switching element 24LV. Also, freewheeling current flows through the U-phase winding of the three-phase motor 50, the U-phase high potential side freewheeling diode 26HU, the W-phase high potential side switching element 24HW, and the W-phase winding of the three-phase motor 50.

[0049] In the sixth case of Fig. 8, both the motor current and the return current flow through the path from the drain side of the W-phase high potential side switching element 24HW to the connection position of the high potential side connecting wire 30. Therefore, in the sixth case of Fig. 8, no motor current flows between the W-phase high potential side switching element 24HW and the connection position of the high potential side connecting wire 30, and no return current path through which return current flows is included. Therefore, in the sixth case of Fig. 8, no deviation occurs between the voltage output by the differential amplifier corresponding to the W-phase high potential side switching element 24HW and the voltage across the W-phase high potential side switching element 24HW.

[0050] 3 to 8, cases where a deviation occurs and cases where a deviation does not occur between the voltage output by the corresponding differential amplifier and the voltage across the high-potential-side switching elements 24HU, 24HV, 24HW or the low-potential-side switching elements 24LU, 24LV, 24LW to be detected. However, these are merely examples, and the switching elements 24HU, 24HV, 24HW, 24LU, 24LV, 24LW where a deviation occurs may vary depending on, for example, the order in which current is applied to the three-phase windings of the three-phase motor 50. Furthermore, the switching elements 24HU, 24HV, 24HW, 24LU, 24LV, 24LW where a deviation occurs may also vary depending on the position at which the high-potential-side connecting wire 30 and / or the low-potential-side connecting wire 32 is drawn out.

[0051] As described above, if the voltage detected using the shared high-potential side connecting line 30 and low-potential side connecting line 32 deviates from the voltages across the high-potential side switching elements 24HU, 24HV, 24HW and the low-potential side switching elements 24LU, 24LV, 24LW, the deviation must be corrected. For this reason, the motor control device 100 according to this embodiment includes a voltage correction unit 46.

[0052] The voltage corrector 46 acquires, from the energization controller 42, the energization state information of the inverter circuit 20, as described with reference to FIGS. 3 to 8. Based on the acquired energization state information, the voltage corrector 46 determines that there is a discrepancy between the voltages output by the differential amplifiers corresponding to the high-side switching elements 24HU, 24HV, 24HW and / or the low-side switching elements 24LU, 24LV, and 24LW whose end-to-end voltages are to be detected and the voltages across the high-side switching elements 24HU, 24HV, 24HW and / or the low-side switching elements 24LU, 24LV, and 24LW whose end-to-end voltages are to be detected. If the voltage corrector 46 determines that there is a discrepancy between the voltages output by the differential amplifiers corresponding to the high-side switching elements 24HU, 24HV, 24HW and / or the low-side switching elements 24LU, 24LV, and 24LW whose end-to-end voltages are to be detected, the voltage corrector 46 corrects the voltages output by the differential amplifiers. This correction is performed by subtracting a voltage drop due to the wiring resistance of the return current path and the return current from the voltages output by the differential amplifiers (i.e., the voltages corresponding to the voltages across the high-side switching elements 24HU, 24HV, 24HW and / or the low-side switching elements 24LU, 24LV, and 24LW).

[0053] That is, when a return current path through which a return current flows but no motor current flows is included between the connection position of the high-side switching elements 24HU, 24HV, 24HW and / or low-side switching elements 24LU, 24LV, 24LW, the voltage of which is to be detected, and the shared high-side connecting line 30 and / or low-side connecting line 32, the voltage correction unit 46 performs a correction to a voltage equivalent to the end-to-end voltage by subtracting the voltage drop due to the wiring resistance of the return current path and the return current from the voltage corresponding to the end-to-end voltage of the high-side switching elements 24HU, 24HV, 24HW and / or low-side switching elements 24LU, 24LV, 24LW. As a result, even if the high potential side connecting line 30 is shared for detecting the voltages across multiple high potential side switching elements 24HU, 24HV, 24HW and the low potential side connecting line 32 is shared for detecting the voltages across multiple low potential side switching elements 24LU, 24LV, 24LW, it becomes possible to accurately detect the voltages across the high potential side switching elements 24HU, 24HV, 24HW and / or the low potential side switching elements 24LU, 24LV, 24LW.

[0054] The microcomputer 40 uses a voltage detection unit 44 and a voltage correction unit 46 to detect the voltages across the high-side switching elements 24HU, 24HV, 24HW and low-side switching elements 24LU, 24LV, 24LW through which the motor current flows, and the voltages corresponding to the voltages across the high-side freewheel diodes 26HU, 26HV, 26HW or low-side freewheel diodes 26LU, 26LV, 26LW through which the freewheel current flows, and makes corrections as necessary.

[0055] Here, the reflux current is generated immediately after the energization phase of the three-phase motor 50 is switched, attenuates over time, and eventually disappears. For example, as shown in FIGS. 2 and 3 , immediately after the energization of the three-phase motor 50 is switched from the WV-phase energization to the UV-phase energization, a reflux current flows through the V-phase winding of the three-phase motor 50, the V-phase low-potential side switching element 24LV, the W-phase low-potential side reflux diode 26LW, and the W-phase winding of the three-phase motor 50, along with the motor current flowing through the UV phase. However, as the reflux current disappears over time, only the UV-phase motor current flows through the inverter circuit 20, as shown in FIG. 9 . Therefore, the voltage correction unit 46 only needs to perform correction when it detects a voltage corresponding to the aforementioned voltage across the three terminals during the period in which the reflux current is generated.

[0056] Whether or not a freewheeling current is flowing in the inverter circuit 20 can be determined, for example, from the voltage across the high-side freewheeling diodes 26HU, 26HV, and 26HW or the low-side freewheeling diodes 26LU, 26LV, and 26LW through which the freewheeling current flows. Hereinafter, an example of a method for determining whether or not a freewheeling current is occurring will be described with reference to Figures 10 and 11.

[0057] 10 shows an enlarged view of a portion of the waveform of the terminal voltage of each phase of the three-phase motor 50 when the energization phase of the three-phase motor 50 is switched, and the W-phase terminal voltage when the energization of the three-phase motor 50 is switched from WV-phase energization to UV-phase energization. When the energization of the three-phase motor 50 is switched from WV-phase energization to UV-phase energization, as described with reference to FIGS. 2 and 3, a reflux current flows through the V-phase winding of the three-phase motor 50, the V-phase low-potential-side switching element 24LV, the W-phase low-potential-side reflux diode 26LW, and the W-phase winding of the three-phase motor 50. Therefore, as shown in the enlarged view of FIG. 10, the W-phase terminal voltage of the three-phase motor 50 drops below the ground voltage by the forward voltage Vf of the low-potential-side reflux diode 26LW. After the return current disappears, the W-phase terminal voltage of the three-phase motor 50 rises to a voltage value corresponding to the induced voltage, and then decreases as the induced voltage decreases.

[0058] 11 also shows an enlarged view of a portion of the waveform of the terminal voltage of each phase of the three-phase motor 50 when the energization phase of the three-phase motor 50 is switched, and the W-phase terminal voltage when the energization of the three-phase motor 50 is switched from VW-phase energization to VU-phase energization. When the energization of the three-phase motor 50 is switched from VW-phase energization to VU-phase energization, as shown in FIG. 6, a freewheeling current flows through the W-phase winding of the three-phase motor 50, the W-phase high-potential side freewheeling diode 26HW, the V-phase high-potential side switching element 24HV, and the V-phase winding of the three-phase motor 50. Therefore, as shown in the enlarged view of FIG. 11, the W-phase terminal voltage of the three-phase motor 50 rises above the power supply voltage by the forward voltage Vf of the high-potential side freewheeling diode 26HW. After the return current disappears, the W-phase terminal voltage of the three-phase motor 50 drops to a voltage value corresponding to the induced voltage, and then rises as the induced voltage rises.

[0059] Therefore, whether or not a freewheeling current is flowing in the inverter circuit 20 can be determined, for example, based on whether the voltage across the high-side freewheeling diodes 26HU, 26HV, 26HW or the low-side freewheeling diodes 26LU, 26LV, 26LW through which the freewheeling current flows is a voltage equivalent to the forward voltage Vf. Alternatively, whether or not a freewheeling current is flowing in the inverter circuit 20 can be determined based on whether or not the potential on the anode side of the high-side freewheeling diodes 26HU, 26HV, 26HW through which the freewheeling current flows is higher than the power supply voltage, or whether or not the potential on the cathode side of the low-side freewheeling diodes 26LU, 26LV, 26LW is lower than the ground potential.

[0060] When it is determined that a reflux current is occurring, the voltage correction unit 46 corrects the voltage corresponding to the voltage across the high-potential side switching elements 24HU, 24HV, 24HW and / or the low-potential side switching elements 24LU, 24LV, 24LW by subtracting the voltage drop due to the wiring resistance of the reflux current path and the reflux current from the voltage. The microcomputer 40 can calculate the reflux current using various methods described below.

[0061] For example, the microcomputer 40 can calculate the freewheeling current from the voltage-current characteristics of the high-side freewheeling diodes 26HU, 26HV, and 26HW of the upper arm circuits 22HU, 22HV, and 22HW through which the freewheeling current flows or the low-side freewheeling diodes 26LU, 26LV, and 26LW of the lower arm circuits 22LU, 22LV, and 22LW, because there is a correlation between the forward voltage Vf of each of the freewheeling diodes 26HU, 26HV, 26HW, 26LU, 26LV, and 26LW and the magnitude of the freewheeling current flowing in the forward direction.

[0062] The voltage-current characteristics of each of the free wheel diodes 26HU, 26HV, 26HW, 26LU, 26LV, and 26LW change with temperature. Therefore, it is preferable that the voltage-current characteristics of the high-side free wheel diodes 26HU, 26HV, and 26HW and the low-side free wheel diodes 26LU, 26LV, and 26LW be corrected based on temperatures detected by temperature detection elements disposed near the high-side free wheel diodes 26HU, 26HV, and 26HW and the low-side free wheel diodes 26LU, 26LV, and 26LW, respectively. By "nearby," we mean a distance that allows the temperature detection elements to accurately detect the temperatures of the high-side free wheel diodes 26HU, 26HV, and 26HW and the low-side free wheel diodes 26LU, 26LV, and 26LW.

[0063] Alternatively, to calculate the reflux current, the microcomputer 40 may turn on high-side switching elements 24HU, 24HV, 24HW of upper arm circuits 22HU, 22HV, 22HW through which no motor current flows but reflux current flows, or low-side switching elements 24LU, 24LV, 24LW of lower arm circuits 22LU, 22LV, 22LW. This allows the microcomputer 40 to calculate the reflux current from the voltages across and on-resistances of the high-side switching elements 24HU, 24HV, 24HW or low-side switching elements 24LU, 24LV, 24LW.

[0064] The on-resistance of each of the switching elements 24HU, 24HV, 24HW, 24LU, 24LV, and 24LW also changes depending on the temperature. Therefore, it is preferable that the on-resistance of each of the switching elements 24HU, 24HV, 24HW, 24LU, 24LV, and 24LW be corrected based on the temperature detected by a temperature detection element disposed near each of the switching elements 24HU, 24HV, 24HW, 24LU, 24LV, and 24LW.

[0065] Furthermore, the microcomputer 40 may calculate the return current based on the value of the current flowing through the high-potential side switching elements 24HU, 24HV, and 24HW or the low-potential side switching elements 24LU, 24LV, and 24LW immediately after the conduction phase of the three-phase motor 50 is switched, through which no motor current flows but a return current flows. This is because the return current initially matches the value of the current flowing immediately before the conduction phase is switched. However, as described above, the return current decays over time. Therefore, the current value immediately before the conduction phase is switched may be corrected using a time constant corresponding to the decay of the return current depending on the elapsed time from the conduction phase switch to the detection of the voltage across both ends.

[0066] The current calculation unit 48 calculates the value of the current flowing through each of the high potential side switching elements 24HU, 24HV, 24HW and the low potential side switching elements 24LU, 24LV, 24LW based on the voltages across the high potential side switching elements 24HU, 24HV, 24HW and the low potential side switching elements 24LU, 24LV, 24LW and the on resistances thereof detected by the voltage detection unit 44 or corrected by the voltage correction unit 46. As described above, the current calculation unit 48 also preferably calculates the value of the current flowing through each of the switching elements 24HU, 24HV, 24HW, 24LU, 24LV, 24LW after correcting the on resistances based on temperatures detected by temperature detection elements disposed near the switching elements 24HU, 24HV, 24HW, 24LU, 24LV, 24LW.

[0067] In this embodiment, if excessive current exceeding a predetermined value flows through the high-side switching elements 24HU, 24HV, and 24HW and the low-side switching elements 24LU, 24LV, and 24LW, the current control unit 42 stops switching control of the inverter circuit 20 using an overcurrent protection function. Excessive current may occur due to an ON failure of the switching elements 24HU, 24HV, 24HW, 24LU, 24LV, and 24LW or a short circuit failure of the wiring to the power supply or ground. Therefore, the motor control device 100 according to this embodiment is configured to detect the voltages across the high-side switching elements 24HU, 24HV, and 24HW and the low-side switching elements 24LU, 24LV, and 24LW through which the motor current flows, at predetermined intervals, including immediately after switching the conduction phase of the three-phase motor 50, as shown in the enlarged view of FIG. 10 , and calculate the current value based on the detected voltages across the high-side switching elements 24HU, 24HV, and 24HW and the low-side switching elements 24LU, 24LV, and 24LW.

[0068] Next, an example of a process executed by the microcomputer 40 to calculate a current value from the voltage across each of the switching elements 24HU, 24HV, 24HW, 24LU, 24LV, and 24LW will be described with reference to the flowchart of Fig. 12. The process shown in the flowchart of Fig. 12 is repeatedly executed at predetermined time intervals after switching of the energized phase. The process shown in the flowchart of Fig. 12 is also executed for each of the switching elements 24HU, 24HV, 24HW, 24LU, 24LV, and 24LW whose voltages are to be detected.

[0069] In step S100, the microcomputer 40 acquires voltages output by differential amplifiers corresponding to the high-side switching elements 24HU, 24HV, 24HW and the low-side switching elements 24LU, 24LV, 24LW that are the targets of voltage detection. As described above, the corresponding differential amplifiers output voltages corresponding to the voltages across the high-side switching elements 24HU, 24HV, 24HW and the low-side switching elements 24LU, 24LV, 24LW that are the targets of voltage detection.

[0070] In step S110, the microcomputer 40 determines whether the acquired voltages are different from the voltages across the switching elements 24HU, 24HV, 24HW, 24LU, 24LV, and 24LW to be detected, and whether correction is necessary, based on the current-carrying state information of the inverter circuit 20. If it is determined that correction is necessary, the microcomputer 40 proceeds to processing of step S120. On the other hand, if it is determined that correction is not necessary, the microcomputer 40 proceeds to processing of step S150.

[0071] In step S120, the microcomputer 40 determines whether a return current is occurring, and if it is determined that a return current is occurring, it detects the return current. In step S130, the microcomputer 40 determines whether a return current is flowing in the inverter circuit 20 based on the determination result in step S120. If it is determined that a return current is flowing, the microcomputer 40 proceeds to processing in step S140. On the other hand, if it is determined that a return current is not flowing, the microcomputer 40 proceeds to processing in step S150. Note that step S120 may be limited to merely determining whether a return current is occurring, and the return current may be detected after it is determined in step S130 that a return current is flowing.

[0072] In step S140, the microcomputer 40 corrects the acquired voltage by subtracting from it a voltage drop due to the wiring resistance of the return current path and the return current, so that the corrected voltage corresponds to the voltage across each of the switching elements 24HU, 24HV, 24HW, 24LU, 24LV, and 24LW to be detected.

[0073] In step S150, the microcontroller 40 calculates the value of the current flowing through each of the switching elements 24HU, 24HV, 24HW, 24LU, 24LV, and 24LW based on the voltage acquired in step S100 or the voltage corrected in step S140 and the on-resistance of each of the switching elements 24HU, 24HV, 24HW, 24LU, 24LV, and 24LW to be detected.

[0074] The calculated current value is provided to the current control unit 42 of the microcomputer 40. If the received current value exceeds a predetermined value, the current control unit 42 stops the switching control of the inverter circuit 20. This prevents excessive current from flowing through the switching elements 24HU, 24HV, 24HW, 24LU, 24LV, and 24LW and the three-phase motor 50.

[0075] The above describes preferred embodiments of the present disclosure, but the present disclosure is not limited to the above-described embodiments and can be implemented in various modified forms within the scope of the gist of the present disclosure.

[0076] For example, in the above-described embodiment, an example has been described in which the three high potential side switching elements 24HU, 24HV, and 24HW share the high potential side connection line 30. However, the number of high potential side switching elements 24HU, 24HV, and 24HW that share the high potential side connection line 30 does not have to be three, and may be two.

[0077] Similarly, in the above-described embodiment, an example has been described in which the three low potential side switching elements 24LU, 24LV, and 24LW share the low potential side connecting line 32. However, the number of low potential side switching elements 24LU, 24LV, and 24LW that share the low potential side connecting line 32 does not have to be three, and may be two.

[0078] In the above-described embodiment, the opposite-side connecting wires 34U, 34V, and 34W are shared by the pairs of high-side switching elements 24HU, 24HV, and 24HW and low-side switching elements 24LU, 24LV, and 24LW for the U, V, and W phases, respectively. However, the number of pairs of high-side switching elements 24HU, 24HV, and 24HW and low-side switching elements 24LU, 24LV, and 24LW that share the opposite-side connecting wires 34U, 34V, and 34W may be two pairs instead of three pairs. Furthermore, the opposite-side connecting wires 34U, 34V, and 34W do not have to be shared by any of the pairs of high-side switching elements 24HU, 24HV, and 24HW and low-side switching elements 24LU, 24LV, and 24LW for the U, V, and W phases.

[0079] In the above-described embodiment, an example has been described in which the voltage-current characteristics of the high-side freewheeling diodes 26HU, 26HV, and 26HW and the low-side freewheeling diodes 26LU, 26LV, and 26LW are corrected based on temperatures detected by temperature detection elements disposed near the high-side freewheeling diodes 26HU, 26HV, and 26HW and the low-side freewheeling diodes 26LU, 26LV, and 26LW, respectively. However, instead of providing a temperature detection element for each of the freewheeling diodes 26HU, 26HV, 26HW, 26LU, 26LV, and 26LW, a temperature detection element may be provided near at least one of the freewheeling diodes 26HU, 26HV, 26HW, 26LU, 26LV, and 26LW. In this case, the voltage-current characteristics of the freewheeling diodes 26HU, 26HV, 26HW, 26LU, 26LV, and 26LW that are not provided with a temperature detection element nearby may be corrected based on the corrected voltage-current characteristics of another freewheeling diode that is located adjacent to them, because the adjacent freewheeling diodes can be considered to undergo similar temperature changes.

[0080] Similarly, when the reflux current is detected based on the on-resistance of the switching elements, a temperature detection element need not be provided for each of the switching elements 24HU, 24HV, 24HW, 24LU, 24LV, and 24LW, but may be provided near at least one of the switching elements 24HU, 24HV, 24HW, 24LU, 24LV, and 24LW. In this case, the on-resistance of the switching elements 24HU, 24HV, 24HW, 24LU, 24LV, and 24LW that are not provided near a temperature detection element may be corrected based on the corrected on-resistance of another switching element disposed adjacent to them. [Explanation of symbols]

[0081] 10: DC power supply, 12: high-potential line, 14: low-potential line, 20: inverter circuit, 22HU, 22HV, 22HW: upper arm circuit, 22LU, 22LV, 22LW: lower arm circuit, 22U, 22V, 22W: upper and lower arm circuits, 24HU, 24HV, 24HW: high-potential side switching elements, 24LU, 24LV, 24LW: low-potential side switching elements, 26HU, 26HV , 26HW: High potential side freewheel diode, 26LU, 26LV, 26LW: Low potential side freewheel diode, 28U, 28V, 28W: Output line, 30: High potential side connecting line, 32: Low potential side connecting line, 34U, 34V, 34W: Opposite side connecting line, 40: Microcomputer, 42: Current control unit, 44: Voltage detection unit, 46: Voltage correction unit, 48: Current calculation unit, 50: Three-phase motor, 100: Motor control device

Claims

1. A motor control device that controls the driving of a three-phase motor (50) via an inverter circuit (20), The inverter circuit has upper and lower arm circuits (22U, 22V, 22W) for three phases, each of which is connected in series with an upper arm circuit (22HU, 22HV, 22HW) including high potential side switching elements (24HU, 24HV, 24HW) and high potential side free wheel diodes (26HU, 26HV, 26HW), and a lower arm circuit (22LU, 22LV, 22LW) including low potential side switching elements (24LU, 24LV, 24LW) and low potential side free wheel diodes (26LU, 26LV, 26LW), corresponding to each phase of the three-phase motor; a voltage detection unit (44) for detecting voltages corresponding to both end voltages of the high potential side switching element and the low potential side switching element; a high potential side connection line (30) that connects the high potential side of the high potential side switching element of each of the upper arm circuits for three phases to the voltage detection unit; a low potential side connection line (32) that connects the low potential side of each of the low potential side switching elements of the three phase lower arm circuits to the voltage detection unit; and opposite-side connection lines (34U, 34V, 34W) connecting the opposite side of the high potential side of the high potential side switching element and the opposite side of the low potential side of the low potential side switching element of each of the upper and lower arm circuits for three phases to the voltage detection unit, the voltage detection unit detects a voltage corresponding to a voltage across the high potential side switching element from a potential difference between a potential of the high potential side connecting line and a potential of the opposite side connecting line, and detects a voltage corresponding to a voltage across the low potential side switching element from a potential difference between a potential of the low potential side connecting line and a potential of the opposite side connecting line; At least one of the high potential side connecting line and the low potential side connecting line is shared for detecting voltages across a plurality of the high potential side switching elements and / or a plurality of the low potential side switching elements, The motor control device further includes a voltage correction unit (46) that corrects a voltage corresponding to the voltage across the high-potential side switching element and / or the low-potential side switching element, detected using the shared high-potential side connecting line and / or the low-potential side connecting line, to a voltage equivalent to the voltage across the high-potential side switching element and / or the low-potential side switching element, depending on connection positions of the shared high-potential side connecting line and / or the low-potential side connecting line to the plurality of high-potential side switching elements and / or the plurality of low-potential side switching elements and paths through which motor current and return current flow in the upper and lower arm circuits for three phases.

2. 2. The motor control device according to claim 1, further comprising a current calculation unit (48) that calculates values ​​of currents flowing through the high potential side switching element and the low potential side switching element based on voltages across the high potential side switching element and the low potential side switching element.

3. 3. The motor control device according to claim 1, wherein the opposite-side connection line is shared for detecting voltages across the high-potential side switching element and the low-potential side switching element in at least one of the upper and lower arm circuits for three phases.

4. 2. The motor control device according to claim 1, wherein the voltage correction unit determines whether the return current is generated based on a voltage across the upper arm circuit and / or the lower arm circuit through which the motor current does not flow and the return current flows, or a potential on the anode side of the high potential side return diode of the upper arm circuit and / or the low potential side return diode of the lower arm circuit, and when it determines that the return current is generated, corrects a voltage corresponding to the voltage across the high potential side switching element and / or the low potential side switching element to a voltage equivalent to the voltage across the high potential side switching element and / or the low potential side switching element.

5. 5. The motor control device according to claim 4, wherein, when it is determined that the return current has occurred, if a return current path through which the return current flows but the motor current does not flow is included between the high-potential side switching element and / or the low-potential side switching element, the high-potential side voltage detection target, and the connection position of the shared high-potential side connecting line and / or the low-potential side connecting line, the voltage correction unit performs a correction to a voltage equivalent to the end-to-end voltage by subtracting a voltage drop due to the return current and the wiring resistance of the return current path from the voltage corresponding to the end-to-end voltage of the high-potential side switching element and / or the low-potential side switching element.

6. 6. The motor control device according to claim 4, wherein the freewheeling current is calculated from the voltage-current characteristics of the high-side freewheeling diode of the upper arm circuit and / or the low-side freewheeling diode of the lower arm circuit through which the freewheeling current flows.

7. 7. The motor control device according to claim 6, wherein the voltage-current characteristics of the high potential side free wheel diode and / or the low potential side free wheel diode are corrected based on a temperature detected by a temperature detection element disposed near the high potential side free wheel diode and / or the low potential side free wheel diode.

8. 8. The motor control device according to claim 7, wherein the voltage-current characteristics of the high potential side free wheel diode and / or the low potential side free wheel diode are corrected based on the corrected voltage-current characteristics of another high potential side free wheel diode and / or the low potential side free wheel diode arranged adjacent to the high potential side free wheel diode and / or the low potential side free wheel diode.

9. 6. The motor control device according to claim 4, wherein the return current is calculated from the voltage across the high potential side switching element and / or the low potential side switching element of the upper arm circuit and / or the low potential side switching element of the lower arm circuit and turned on when the motor current does not flow and the return current flows.

10. 10. The motor control device according to claim 9, wherein the on-resistance of the high potential side switching element and / or the low potential side switching element is corrected based on a temperature detected by a temperature detection element arranged near the high potential side switching element and / or the low potential side switching element.

11. 11. The motor control device according to claim 10, wherein the on-resistance of the high potential side switching element and / or the low potential side switching element is corrected based on the corrected on-resistance of another high potential side switching element and / or the low potential side switching element arranged adjacent to the high potential side switching element and / or the low potential side switching element.

12. 6. The motor control device according to claim 4, wherein the return current is calculated based on a value of a current that was flowing in the high-potential side switching element and / or the low-potential side switching element through which the motor current does not flow and the return current flows immediately after switching of the current-carrying phase of the three-phase motor, just before switching of the current-carrying phase of the three-phase motor.

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