Short-circuit protection device for power conversion devices

Abstract

The present application relates to a short-circuit protection device of a power conversion device. To reduce an increase in cost and a large size of the power conversion device due to short-circuit protection in a case where a plurality of switching elements are connected in parallel. A short-circuit protection device of a power conversion device that supplies power to a load via a plurality of switching element sections connected in parallel is provided. The short-circuit protection device has a short-circuit determination section that outputs a cutoff instruction signal for stopping on-off driving of the plurality of switching element sections in a case where it is determined that there is a short-circuit failure in the plurality of switching element sections using a Rogowski coil that outputs a detection signal indicating a detection result using a sum of currents detected flowing through two or more of the plurality of switching element sections. In the short-circuit protection device, a distance between return lines of adjacent Rogowski coils is long.

Description

Technical Field

[0001] This invention relates to a short-circuit protection device for power conversion equipment. Background Technology

[0002] In power conversion devices that drive loads such as motors, excessive current sometimes flows through the semiconductor switching elements that constitute the power conversion device. If such excessive current flows for an extended period, it may damage the semiconductor switching elements. Therefore, a short-circuit protection device is installed in the power conversion device to detect excessive current flowing through the semiconductor switching elements and stop the power conversion device.

[0003] In the technology disclosed in Patent Document 1, a voltage-driven semiconductor element is provided in each of the multiple arms. Furthermore, a current detector is provided in each of the multiple arms to detect the current flowing through the arm. When the arm current flowing through the voltage-driven semiconductor element of a certain arm exceeds a predetermined value, the gating pulse output by the gate drive unit corresponding to that voltage-driven semiconductor element is switched off, thereby achieving short-circuit protection for that arm.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2008-236907 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] However, in power conversion devices, to achieve higher capacity, multiple switching elements are sometimes connected in parallel to form each arm. In this case, each switching element requires a current detector, which may lead to increased costs and a larger device size.

[0009] The present invention was made in view of the problems described above, and its object is to reduce the increase in cost of power conversion devices for short-circuit protection when multiple switching elements are connected in parallel, and to reduce the size of the device.

[0010] Solution for solving the problem

[0011] The short-circuit protection device of the power conversion device of the present invention is a short-circuit protection device for a power conversion device that supplies power to a load via M switching element sections connected in parallel. The short-circuit protection device is characterized by having: Ma current detectors, where Ma is 1 less than M (i.e., Ma = M-1), and Ma is an integer greater than or equal to 3; Ma Rogowski coils, each of which surrounds the current path of at least two of the M switching element sections; and a short-circuit determination unit, which, based on the detection signals obtained from each of the Ma current detectors, determines that a short-circuit fault exists in the M switching element sections, and outputs a cut-off indication signal to stop the on / off driving of each of the M switching element sections. The Nth current detector among the Ma current detectors detects the sum of the currents flowing through all switching element sections from the 1st to the Mth switching element sections, excluding the Nth switching element section, where N is an integer from 1 to Ma. The short-circuit determination unit determines the short-circuit protection device when all current detection values ​​obtained from the Ma current detectors exceed a threshold value. In the case where a short circuit fault is determined to exist in the Mth switching element section, and the current detection value obtained from one of the Ma current detectors does not exceed the threshold, but the current detection value obtained from the other Ma-1 current detectors exceeds the threshold, it is determined that a short circuit fault exists in the switching element section that is not the current detection target of that current detector. The Ma Rogowski coils are mounted on a multilayer printed circuit board, and there is an overlapping portion formed by the Ma Rogowski coils arranged in the depth direction on the multilayer printed circuit board. The return line of the Rogowski coil located on the outermost side of the multilayer printed circuit board is located closer to the outermost side than the central axis of the Rogowski coil. The return line of the Rogowski coil located on the innermost side of the multilayer printed circuit board is located closer to the innermost side than the central axis of the Rogowski coil. The overlapping portion is located in a region where the distance between the return lines of adjacent Rogowski coils in the depth direction is longer than the distance between the central axes of the adjacent Rogowski coils.

[0012] The effects of the invention

[0013] According to the present invention, short-circuit faults in switching elements can be detected using a smaller number of current detectors than the number of switching elements, and the switching element in which the short-circuit fault occurred can be identified. This reduces the increased cost of power conversion devices for short-circuit protection when multiple switching elements are connected in parallel, and also reduces the need for larger devices. Furthermore, regarding the overlapping portion formed by Ma Rogowski coils arranged in the depth direction, a region is formed at the overlapping portion where the distance between the return lines of adjacent Rogowski coils in the depth direction is longer than the distance between the central axes of those adjacent Rogowski coils. Therefore, the influence of current flowing in one return line on other return lines adjacent to that return line can be reduced, improving the accuracy of current measurement. Attached Figure Description

[0014] Figure 1 This is a circuit diagram showing the structure of a power conversion device having a short-circuit protection device as one embodiment of the present invention.

[0015] Figure 2 This is a block diagram showing an example of the structure of the short-circuit detection section of the short-circuit protection device.

[0016] Figure 3 This is a waveform diagram illustrating an example of the operation of this embodiment.

[0017] Figure 4 This is a waveform diagram illustrating an example of the operation of this embodiment.

[0018] Figure 5 This is a waveform diagram illustrating an example of the operation of this embodiment.

[0019] Figure 6 This is a waveform diagram illustrating an example of the operation of this embodiment.

[0020] Figure 7 This is a perspective view showing an example of the installation of three Rogowski coils in the short-circuit protection device.

[0021] Figure 8 This is a top view showing an example of the structure of the Rogowski coil.

[0022] Figure 9 This is a perspective view showing an example of the overlapping portion of the three Rogowski coils.

[0023] Figure 10 This is a diagram that abstractly illustrates the installation example.

[0024] Figure 11 This is a top view showing an example of the installation of four Rogowski coils in the short-circuit protection device.

[0025] Figure 12This is a diagram that abstractly illustrates the first method of representing the four Rogowski coils.

[0026] Figure 13 This is a diagram that abstractly illustrates the second method of using the four Rogowski coils. Detailed Implementation

[0027] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0028] Figure 1 This is a circuit diagram showing the structure of a power conversion device 100 equipped with a short-circuit protection device 50 as an embodiment of the present invention. The power conversion device 100 includes a control unit 1 that controls each part of the power conversion device 100 according to instructions from a host device 200, and drive units 2a and 2b that convert power.

[0029] In this embodiment, the power conversion device 100 is a device equivalent to one phase of an inverter. Figure 1 The diagram shows the drive units 2a and 2b of phase 1 of the inverter. Drive unit 2a is connected between the high-potential power line 101 and the output terminal 103. The high-potential power line 101 is connected to the positive terminal of a DC power supply (not shown), and the output terminal 103 is connected to a load (not shown). Drive unit 2b is connected between the low-potential power line 102 and the output terminal 103. The low-potential power line 102 is connected to the negative terminal of the DC power supply. In practice, the power conversion device 100 is configured as an inverter by connecting the multi-phase drive units 2a and 2b in parallel between the high-potential power line 101 and the low-potential power line 102.

[0030] The internal structure of the drive unit 2a will be described below. The internal structure of the drive unit 2b is basically the same as that of the drive unit 2a, therefore its description is omitted.

[0031] The drive unit 2a includes multiple switching element units 20_1, 20_2, 20_3 and 20_4 connected in parallel, a drive control unit 24, and a short-circuit protection device 50.

[0032] Switching element sections 20_1, 20_2, 20_3, and 20_4 each include a power switching element 27. This power switching element 27 is a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), constructed from wide-bandgap semiconductor elements such as SiC or GaN. A diode 28 is connected in reverse parallel with the power switching element 27. Driving section 2b, like driving section 2a, also includes multiple switching element sections connected in parallel. The power conversion device 100 supplies power to the load connected to the output terminal 103 via these multiple switching element sections connected in parallel in each of the driving sections 2a and 2b.

[0033] Based on the control signal Sm1 supplied from the control unit 1, the drive control unit 24 outputs a drive signal Son / off to switch the power switching element 27 of each of the switching element units 20_1, 20_2, 20_3, and 20_4 from off to on or from on to off. Additionally, when the short-circuit protection device 50 outputs a cut-off indication signal Fx, the drive control unit 24 outputs a drive signal Son / off to switch the power switching element 27 of each of the switching element units 20_1, 20_2, 20_3, and 20_4 from on to off.

[0034] The short-circuit protection device 50 is a device that detects the occurrence of short-circuit faults in the parallel-connected switching elements 20_1, 20_2, 20_3, and 20_4 to protect the switching elements 20_1, 20_2, 20_3, and 20_4 from the effects of short-circuit faults. For example... Figure 1 As shown, the short-circuit protection device 50 includes Rogowski coils 21_1, 21_2, and 21_3, integrators 22_1, 22_2, and 22_3, and a short-circuit detection unit 23. Short-circuit faults in the switching element unit 20_1, etc., may include erroneous connection of the power switching element 27, short-circuit faults, and short-circuit faults of the diode 28.

[0035] Rogowski coils 21_1, 21_2, and 21_3 are Ma current detectors, where Ma is one less than the number M of the multiple switching elements connected in parallel (M = 4 in this example), specifically Ma = M - 1 = 3. Each Rogowski coil of 21_1, 21_2, and 21_3 detects the sum of the currents flowing through two or more of the M switching elements and outputs a detection signal indicating the detection result. Each of the Ma Rogowski coils surrounds the current path of two or more of the M switching elements. In this embodiment, Rogowski coils 21_1, 21_2, and 21_3 are disposed on the current path of the source side of the power switching element 27 in each of the switching elements 20_1, 20_2, 20_3, and 20_4.

[0036] In this embodiment, the Nth current detector (N is an integer from 1 to Ma) among the Ma current detectors detects the sum of the currents flowing through all the switching element sections from the first to the Mth switching element sections, excluding the Nth switching element section.

[0037] Specifically, in this embodiment, the first switching element section is switching element section 20_1, the second switching element section is switching element section 20_2, the third switching element section is switching element section 20_3, and the fourth switching element section is switching element section 20_4. Furthermore, the first current detector is a Rogowski coil 21_1, the second current detector is a Rogowski coil 21_2, and the third current detector is a Rogowski coil 21_3.

[0038] The Rogowski coil 21_1, acting as the first current detector, surrounds the current paths 20_2a, 20_3a, and 20_4a of the other switching element sections 20_2, 20_3, and 20_4, excluding the first switching element section 20_1. It detects the sum of the currents flowing through these current paths and outputs a detection signal Vi1, representing the detection result, to the integrator 22_1. This detection signal Vi1 represents the time derivative of the sum of the currents flowing through the switching element sections 20_2, 20_3, and 20_4. The integrator 22_1 integrates the detection signal Vi1 to generate a current detection value Si1, representing the sum of the currents flowing through the switching element sections 20_2, 20_3, and 20_4, and outputs the current detection value Si1 to the short-circuit detection unit 23.

[0039] The Rogowski coil 21_2, acting as the second current detector, surrounds the current paths 20_1a, 20_3a, and 20_4a of the other switching element sections 20_1, 20_3, and 20_4, excluding the second switching element section 20_2. It detects the sum of the currents flowing through these current paths and outputs a detection signal Vi2, representing the detection result, to the integrator 22_2. This detection signal Vi2 represents the time derivative of the sum of the currents flowing through the switching element sections 20_1, 20_3, and 20_4. The integrator 22_2 integrates the detection signal Vi2 to generate a current detection value Si2, representing the sum of the currents flowing through the switching element sections 20_1, 20_3, and 20_4, and outputs the current detection value Si2 to the short-circuit detection unit 23.

[0040] The Rogowski coil 21_3, acting as the third current detector, surrounds the current paths 20_1a, 20_2a, and 20_4a of the other switching element sections 20_1, 20_2, and 20_4, excluding the third switching element section 20_3. It detects the sum of the currents flowing through these current paths and outputs a detection signal Vi3, representing the detection result, to the integrator 22_3. This detection signal Vi3 represents the time derivative of the sum of the currents flowing through the switching element sections 20_1, 20_2, and 20_4. The integrator 22_3 integrates the detection signal Vi3 to generate a current detection value Si3, representing the sum of the currents flowing through the switching element sections 20_1, 20_2, and 20_4, and outputs the current detection value Si3 to the short-circuit detection unit 23.

[0041] The short-circuit detection unit 23 makes a judgment related to short-circuit faults in the switching element units 20_1, 20_2, 20_3, and 20_4 based on the current detection values ​​Si1, Si2, and Si3. Furthermore, if the short-circuit detection unit 23 determines that a short-circuit fault has occurred in the switching element unit 20_1, it outputs a short-circuit fault signal F1 to the control unit 1; if it determines that a short-circuit fault has occurred in the switching element unit 20_2, it outputs a short-circuit fault signal F2 to the control unit 1; if it determines that a short-circuit fault has occurred in the switching element unit 20_3, it outputs a short-circuit fault signal F3 to the control unit 1; and if it determines that a short-circuit fault has occurred in the switching element unit 20_4, it outputs a short-circuit fault signal F4 to the control unit 1. The control unit 1 then sends the short-circuit fault signal F1, F2, F3, or F4 to the host device 200. When the host device 200 receives any short-circuit fault signal, it displays information on a display device to determine which of the switching element sections 20_1, 20_2, 20_3, or 20_4 has experienced a short-circuit fault. Furthermore, if the short-circuit judgment unit 23 determines that a short-circuit fault has occurred in any of the switching element sections 20_1, 20_2, 20_3, or 20_4, it outputs a cut-off indication signal Fx to the drive control unit 24. Upon receiving the cut-off indication signal Fx, the drive control unit 24 stops the on / off driving of the power switching elements 27 of the switching element sections 20_1, 20_2, 20_3, and 20_4.

[0042] Figure 2 This is a block diagram showing an example of the structure of the short-circuit detection unit 23. For example... Figure 2 As shown, the short-circuit detection unit 23 includes comparators 301, 302, and 303, NOT operators 311, 312, and 313, AND operators 321, 322, 323, and 324, on-delay operators 331, 332, 333, and 334, and OR operator 340. The on-delay operators 331, 332, 333, and 334 are operators that delay the change of the input signal from an inactive level to an active level by a predetermined time before outputting, thus stabilizing the operation of the short-circuit detection unit 23.

[0043] Comparator 301 sets its output signal to an inactive level when the current detection value Si1, representing the sum of the currents of switching elements 20_2, 20_3, and 20_4, does not exceed the short-circuit current determination threshold th; otherwise, it sets the output signal to an active level. Comparator 302 sets its output signal to an inactive level when the current detection value Si2, representing the sum of the currents of switching elements 20_1, 20_3, and 20_4, does not exceed the short-circuit current determination threshold th; otherwise, it sets the output signal to an active level. Comparator 303 sets its output signal to an inactive level when the current detection value Si3, representing the sum of the currents of switching elements 20_1, 20_2, and 20_4, does not exceed the short-circuit current determination threshold th; otherwise, it sets the output signal to an active level. In this case, the short-circuit current determination threshold th can, for example, be set to 300% of the rated power switching element current.

[0044] NOT operator 311 inverts the level of the output signal of comparator 301 and outputs it. NOT operator 312 inverts the level of the output signal of comparator 302 and outputs it. NOT operator 313 inverts the level of the output signal of comparator 303 and outputs it.

[0045] If at least one of the output signals of comparators 301, 302, and 303 is at an active level, that is, if at least one of the sum of the currents of switching element sections 20_2, 20_3, and 20_4, the sum of the currents of switching element sections 20_1, 20_3, and 20_4, and the sum of the currents of switching element sections 20_1, 20_2, and 20_4 exceeds the short-circuit current determination threshold th, the OR operator 340 determines that a short-circuit fault has occurred in one of the switching element sections 20_1, 20_2, 20_3, and 20_4, and outputs the cut-off indication signal Fx to the drive control section 24.

[0046] When the output signal of NOT operator 311 is at an active level and the output signals of comparators 302 and 303 are at an active level, that is, when the sum of the currents of switching elements 20_2, 20_3 and 20_4 does not exceed the short-circuit current determination threshold th, and the sum of the currents of switching elements 20_1, 20_3 and 20_4 and the sum of the currents of switching elements 20_1, 20_2 and 20_4 both exceed the short-circuit current determination threshold th, AND operator 321 determines that a short-circuit fault has occurred in switching element 20_1, and outputs a short-circuit fault signal F1 to control unit 1 via turn-on delay operator 331. Thus, if the current detection value obtained from one of the Ma current detectors (in this example, the current detection value Si1 obtained from Rogowski coil 21_1) does not exceed the threshold, but the current detection values ​​obtained from the other Ma-1 current detectors (in this example, the current detection values ​​Si2 and Si3 obtained from Rogowski coils 21_2 and 21_3) exceed the threshold, the AND operator 321 determines that there is a short circuit fault in the switching element section (in this example, the switching element section 20_1) that is not the current detection target of that current detector.

[0047] When the output signal of NOT operator 312 is at an active level and the output signals of comparators 301 and 303 are at active levels, that is, when the sum of the currents of switching elements 20_1, 20_3 and 20_4 does not exceed the short-circuit current determination threshold th, and the sum of the currents of switching elements 20_2, 20_3 and 20_4 and the sum of the currents of switching elements 20_1, 20_2 and 20_4 both exceed the short-circuit current determination threshold th, AND operator 322 determines that a short-circuit fault has occurred in switching element 20_2, and outputs a short-circuit fault signal F2 to control unit 1 via turn-on delay operator 332. Thus, if the current detection value obtained from one of the Ma current detectors (in this example, the current detection value Si2 obtained from Rogowski coil 21_2) does not exceed the threshold, but the current detection values ​​obtained from the other Ma-1 current detectors (in this example, the current detection values ​​Si1 and Si3 obtained from Rogowski coils 21_1 and 21_3) exceed the threshold, the AND operator 322 determines that there is a short circuit fault in the switching element section (in this example, the switching element section 20_2) that is not the current detection target of that current detector.

[0048] When the output signal of NOT operator 313 is at an active level and the output signals of comparators 301 and 302 are at an active level, that is, when the sum of the currents of switching element sections 20_1, 20_2 and 20_4 does not exceed the short-circuit current determination threshold th, and the sum of the currents of switching element sections 20_2, 20_3 and 20_4 and the sum of the currents of switching element sections 20_1, 20_3 and 20_4 both exceed the short-circuit current determination threshold th, AND operator 323 determines that a short-circuit fault has occurred in switching element section 20_3, and outputs a short-circuit fault signal F3 to control section 1 via turn-on delay operator 333. Thus, if the current detection value of one of the Ma current detectors (in this example, the current detection value Si3 obtained from Rogowski coil 21_3) does not exceed the threshold, but the current detection values ​​obtained from the other Ma-1 current detectors (in this example, the current detection values ​​Si1 and Si2 obtained from Rogowski coils 21_1 and 21_2) exceed the threshold, the AND operator 323 determines that there is a short circuit fault in the switching element section (in this example, the switching element section 20_3) that is not the current detection target of that current detector.

[0049] When all output signals of comparators 301, 302, and 303 are at active levels, i.e., when the sum of the currents in switching elements 20_2, 20_3, and 20_4, the sum of the currents in switching elements 20_1, 20_3, and 20_4, and the sum of the currents in switching elements 20_1, 20_2, and 20_4 all exceed the short-circuit current determination threshold th, the AND operator 324 determines that a short-circuit fault has occurred in switching element 20_4 and outputs a short-circuit fault signal F4 to control unit 1 via the turn-on delay operator 334. Thus, when the current detection values ​​of Ma current detectors (in this example, the current detection values ​​Si1, Si2, and Si3 obtained from Rogowski coils 21_1, 20_2, and 21_3 in this example) all exceed the threshold th, the AND operator 324 determines that a short-circuit fault exists in the Mth switching element (in this example, switching element 20_4).

[0050] Figures 3-6 These are waveform diagrams illustrating an example of short-circuit fault detection in this embodiment. The operation of this embodiment will be explained below with reference to these diagrams.

[0051] exist Figure 3In the illustrated operating example, a short-circuit fault occurs in the switching element section 20_1. Under normal conditions prior to this short-circuit fault, the current detection value Si1, representing the sum of the currents in switching elements 20_2, 20_3, and 20_4, is lower than the short-circuit current determination threshold th. Furthermore, the current detection value Si2, representing the sum of the currents in switching elements 20_1, 20_3, and 20_4, is also lower than the short-circuit current determination threshold th. Additionally, the current detection value Si3, representing the sum of the currents in switching elements 20_1, 20_2, and 20_4, is also lower than the short-circuit current determination threshold th.

[0052] When a short-circuit fault occurs in the switching element section 20_1, the current flowing through the switching element section 20_1 is greater than the normal current. In this case, the current detection value Si2, which represents the sum of the currents in switching element sections 20_1, 20_3, and 20_4, and the current detection value Si3, which represents the sum of the currents in switching element sections 20_1, 20_2, and 20_4, exceed the short-circuit current determination threshold th, while the current detection value Si1, which represents the sum of the currents in switching element sections 20_2, 20_3, and 20_4, does not exceed the short-circuit current determination threshold th. Therefore, the cut-off indication signal Fx and the short-circuit fault signal F1, which is used to determine that the switching element section 20_1 is a short-circuit fault location, change to an active level.

[0053] exist Figure 4 In the illustrated operating example, a short-circuit fault occurs in the switching element section 20_2. The normal operation before this short-circuit fault and... Figure 3 The actions are the same.

[0054] When a short-circuit fault occurs in the switching element section 20_2, the current flowing through the switching element section 20_2 is greater than the normal current. In this case, the current detection value Si1, which represents the sum of the currents in switching elements 20_2, 20_3, and 20_4, and the current detection value Si3, which represents the sum of the currents in switching elements 20_1, 20_2, and 20_4, exceed the short-circuit current determination threshold th, while the current detection value Si2, which represents the sum of the currents in switching elements 20_1, 20_3, and 20_4, does not exceed the short-circuit current determination threshold th. Therefore, the cut-off indication signal Fx and the short-circuit fault signal F2, which is used to determine that the switching element section 20_2 is a short-circuit fault location, change to an active level.

[0055] exist Figure 5 In the illustrated operating example, a short-circuit fault occurs in the switching element section 20_3. The normal operation before this short-circuit fault and... Figure 3 The actions are the same.

[0056] When a short-circuit fault occurs in the switching element section 20_3, the current flowing through the switching element section 20_3 is greater than the normal current. In this case, the current detection value Si1, which represents the sum of the currents in switching elements 20_2, 20_3, and 20_4, and the current detection value Si2, which represents the sum of the currents in switching elements 20_1, 20_3, and 20_4, exceed the short-circuit current determination threshold th, while the current detection value Si3, which represents the sum of the currents in switching elements 20_1, 20_2, and 20_4, does not exceed the short-circuit current determination threshold th. Therefore, the cut-off indication signal Fx and the short-circuit fault signal F3, which is used to determine that the switching element section 20_3 is a short-circuit fault location, change to an active level.

[0057] exist Figure 6 In the illustrated operating example, a short-circuit fault occurs in the switching element section 20_4. The normal operation before this short-circuit fault and... Figure 3 The actions are the same.

[0058] When a short-circuit fault occurs in the switching element section 20_4, the current flowing through the switching element section 20_4 is greater than the normal current. In this case, the current detection value Si1, representing the sum of the currents in switching elements 20_2, 20_3, and 20_4; the current detection value Si2, representing the sum of the currents in switching elements 20_1, 20_3, and 20_4; and the current detection value Si3, representing the sum of the currents in switching elements 20_1, 20_2, and 20_4, all exceed the short-circuit current determination threshold th. Therefore, the cut-off indication signal Fx and the short-circuit fault signal F4, used to determine that the switching element section 20_4 is a short-circuit fault location, are at active levels.

[0059] As described above, according to this embodiment, three Rogowski coils 21_1, 21_2, and 21_3 are provided, one less than the number of parallel connections of switching element sections 20_1, 20_2, 20_3, and 20_4. These three Rogowski coils are used to detect short-circuit faults in each switching element section. As a result of the detection, the driving of switching element sections 20_1, 20_2, 20_3, and 20_4 is stopped, and the switching element section where a short-circuit fault has occurred is identified. Therefore, the increased cost of the power conversion device 100 for short-circuit protection when multiple switching element sections are connected in parallel, as well as the increase in device size, can be reduced. Furthermore, in this embodiment, each of the three Rogowski coils 21_1, 21_2, and 21_3 detects the sum of the currents of the three switching element sections. Therefore, the current detection accuracy of each Rogowski coil can be made the same, and short-circuit faults in each switching element section can be accurately determined.

[0060] Next, an example of the preferred Rogowski coil in this embodiment will be described. Figure 7This is a perspective view illustrating Rogowski coils 21_1, 21_2, and 21_3 mounted on substrate 400. In this example, Rogowski coils 21_1, 21_2, and 21_3 are mounted on substrate 400 in an overlapping state at the overlap portion OV.

[0061] In this substrate 400, the current path 20_1a of the switching element section 20_1 is inserted into a region surrounded by Rogowski coils 21_2 and 21_3 but not surrounded by Rogowski coil 21_1. Similarly, in the substrate 400, the current path 20_2a of the switching element section 20_2 is inserted into a region surrounded by Rogowski coils 21_1 and 21_3 but not surrounded by Rogowski coil 21_2. Furthermore, in the substrate 400, the current path 20_3a of the switching element section 20_3 is inserted into a region surrounded by Rogowski coils 21_1 and 21_2 but not surrounded by Rogowski coil 21_3. Additionally, in the substrate 400, the current path 20_4a of the switching element section 20_4 is inserted into a region completely surrounded by Rogowski coils 21_1, 21_2, and 21_3. In this case, Figure 7 In the middle, the overlapping part OV formed by the three Rogowski coils 21_1, 21_2 and 21_3 overlapping each other in the depth direction of the substrate 400 is generated on the lower side, the right side and the upper side of the current path 20_2a, 20_3a and 20_4a.

[0062] Rogowski coil 21_1 surrounds current paths 20_2a, 20_3a, and 20_4a, and is used to detect the sum of the currents flowing through the switching elements 20_2, 20_3, and 20_4. Similarly, Rogowski coil 21_2 surrounds current paths 20_1a, 20_3a, and 20_4a, and is used to detect the sum of the currents flowing through the switching elements 20_1, 20_3, and 20_4. Finally, Rogowski coil 21_3 surrounds current paths 20_1a, 20_2a, and 20_4a, and is used to detect the sum of the currents flowing through the switching elements 20_1, 20_2, and 20_4.

[0063] Figure 8 This is a top view illustrating the Rogowski coil 21_1. (See attached image.) Figure 8 As shown, the Rogowski coil 21_1 has a coil 21_1_C extending in a spiral shape and a return line 21_1_R within the coil 21_1_C returning from the end point of the coil 21_1_C to the beginning point. Although the illustration is omitted, Rogowski coils 21_2 and 21_3 also have the same structure as Rogowski coil 21_1.

[0064] Figure 9 It is shown Figure 7 A perspective view of the mounting example of Rogowski coils 21_1, 21_2, and 21_3 at the overlapping portion OV. Figure 9 In this process, Rogowski coils 21_1, 21_2 and 21_3 are mounted on a multilayer printed circuit board 400a.

[0065] The lower horizontal portion of the coil 21_3_C of the Rogowski coil 21_3 is formed on the first layer L1 of the multilayer printed circuit board 400a. The return line 21_3_R of the Rogowski coil 21_3 is formed on the second layer L2 above the first layer L1. The upper horizontal portion of the coil 21_3_C of the Rogowski coil 21_3 is formed on the third layer L3 above the second layer L2. Furthermore, a vertical portion connecting the upper and lower horizontal portions of the coil 21_3_C is formed using a through-hole TH3-1 that connects the third layer L3 to the first layer L1.

[0066] The lower horizontal portion of the Rogowski coil 21_2_C is formed on the fourth layer (L4) above the third layer (L3). The return line 21_2_R of the Rogowski coil 21_2 is formed on the fifth layer (L5) above the fourth layer (L4). The upper horizontal portion of the Rogowski coil 21_2_C is formed on the sixth layer (L6) above the fifth layer (L5). Furthermore, a vertical portion connecting the upper and lower horizontal portions of the coil 21_2_C is formed using a through-hole TH6-4 that connects the sixth layer (L6) to the fourth layer (L4).

[0067] The lower horizontal portion of coil 21_1_C of Rogowski coil 21_1 is formed on layer 7, above layer 6 (L6). The return line 21_1_R of Rogowski coil 21_1 is formed on layer 8, above layer 7 (L7). The upper horizontal portion of coil 21_1_C of Rogowski coil 21_1 is formed on layer 9, above layer 8 (L8). Furthermore, a vertical portion connecting the upper and lower horizontal portions of coil 21_1_C is formed using through-hole TH9-7, which connects layer 9 (L9) and layer 7 (L7).

[0068] Figure 10 It is Figure 9 The diagram shown is an abstract representation of Rogowski coils 21_1, 21_2, and 21_3. Figure 9 In the multilayer printed circuit board 400a shown, layer 9 (L9) is the outermost layer, and layer 1 (L1) is the innermost layer. Therefore, in Figure 10Of the Rogowski coils 21_1, 21_2, and 21_3 shown, Rogowski coil 21_1 is the outermost Rogowski coil, Rogowski coil 21_3 is the innermost Rogowski coil, and Rogowski coil 21_2 is the middle layer Rogowski coil located between the outermost and innermost layers.

[0069] In this installation example, the depth directions of Rogowski coils 21_1, 21_2, and 21_3 ( Figure 10 The dimensions in the vertical direction are the same. Furthermore, the distance d between the central axis M1 of Rogowski coil 21_1 and the central axis M2 of Rogowski coil 21_2 is the same as the distance d between the central axis M2 of Rogowski coil 21_2 and the central axis M3 of Rogowski coil 21_3.

[0070] Furthermore, in this installation example, the return line 21_1_R of the outermost Rogowski coil 21_1 is located closer to the outermost side than the central axis M1 of the Rogowski coil 21_1, and the return line 21_3_R of the innermost Rogowski coil 21_3 is located closer to the innermost side than the central axis M3 of the Rogowski coil 21_3. Accordingly, the overlapping portion OV is formed in the region where the distance between the return lines of adjacent Rogowski coils is longer than the distance between the central axes of the Rogowski coils. Specifically, in this installation example, the return line 21_2_R of the middle layer Rogowski coil 21_2 is located on the central axis M2 of the Rogowski coil 21_2. Furthermore, the distance between the return lines 21_1_R and 21_2_R of adjacent Rogowski coils and the distance between the return lines 21_2_R and 21_3_R of adjacent Rogowski coils are longer than the distance d between the central axes of adjacent Rogowski coils.

[0071] In this installation example, the return lines 21_1_R of Rogowski coil 21_1, 21_2_R of Rogowski coil 21_2, and 21_3_R of Rogowski coil 21_3 extend parallel to each other across the overall length of the overlapping portion OV. Therefore, when return lines 21_1_R and 21_2_R are close together, and return lines 21_2_R and 21_3_R are close together, current flows through one of the return lines. As a result, if a magnetic field is generated around this return line, currents are induced in adjacent return lines to generate a magnetic field that cancels out the magnetic field, potentially hindering current measurement. However, in this installation example, return lines 21_1_R and 21_2_R are far apart from each other, and return lines 21_2_R and 21_3_R are also far apart from each other, so that each return line is less susceptible to the influence of currents flowing in adjacent return lines. Therefore, high-precision current measurement can be performed using Rogowski coils 21_1, 21_2 and 21_3.

[0072] In the embodiments described above, the number M of the parallel-connected switching elements is 4, and the number Ma of the Rogowski coils is M-1, which is 3. In the embodiments described below, the number M of the parallel-connected switching elements is 5, and the number Ma of the Rogowski coils is M-1, which is 4. Figure 11 This is a top view illustrating the Rogowski coils 21_1, 21_2, 21_3 and 21_4 mounted on the multilayer printed circuit board 400A in this embodiment.

[0073] In the multilayer printed circuit board 400A, the current path 20_1a of the first switching element is inserted into the region surrounded by Rogowski coils 21_2, 21_3, and 21_4 but not surrounded by Rogowski coil 21_1. Furthermore, in the multilayer printed circuit board 400A, the current path 20_2a of the second switching element is inserted into the region surrounded by Rogowski coils 21_1, 21_3, and 21_4 but not surrounded by Rogowski coil 21_2. Additionally, in the multilayer printed circuit board 400A, the current path 20_3a of the third switching element is inserted into the region surrounded by Rogowski coils 21_1, 21_2, and 21_4 but not surrounded by Rogowski coil 21_3. Furthermore, in the multilayer printed circuit board 400A, the current path 20_4a of the fourth switching element is inserted into the region surrounded by Rogowski coils 21_1, 21_2, and 21_3 but not by Rogowski coil 21_4. Additionally, in the multilayer printed circuit board 400A, the current path 20_5a of the fifth switching element is inserted into the region completely surrounded by Rogowski coils 21_1, 21_2, 21_3, and 21_4. In this case, Figure 11In the middle, the overlapping portion OV formed by the four Rogowski coils 21_1, 21_2, 21_3 and 21_4 arranged in the depth direction of the multilayer printed circuit board 400A is generated on the upper side, the right side and the lower side of the current path 20_2a, 20_3a, 20_4a and 20_5a.

[0074] Rogowski coil 21_1 surrounds current paths 20_2a, 20_3a, 20_4a, and 20_5a, and is used to detect the sum of the currents flowing through these current paths. Similarly, Rogowski coil 21_2 surrounds current paths 20_1a, 20_3a, 20_4a, and 20_5a, and is used to detect the sum of the currents flowing through these current paths. Rogowski coil 21_3 surrounds current paths 20_1a, 20_2a, 20_4a, and 20_5a, and is used to detect the sum of the currents flowing through these current paths. Finally, Rogowski coil 21_4 surrounds current paths 20_1a, 20_2a, 20_3a, and 20_5a, and is used to detect the sum of the currents flowing through these current paths.

[0075] In this embodiment, two methods are considered as the installation methods for Rogowski coils 21_1, 21_2, 21_3 and 21_4. Figure 12 The diagram is an abstract representation of the Rogowski coils 21_1, 21_2, 21_3 and 21_4 arranged in the depth direction of the multilayer printed circuit board 400A in the first method.

[0076] exist Figure 12 Of the Rogowski coils 21_1, 21_2, 21_3 and 21_4 shown, Rogowski coil 21_1 is the outermost Rogowski coil, Rogowski coil 21_4 is the innermost Rogowski coil, and Rogowski coils 21_2 and 21_3 are the middle Rogowski coils between the outermost and innermost layers.

[0077] In this method, the depth directions of Rogowski coils 21_1, 21_2, 21_3, and 21_4 are also... Figure 12 The dimensions in the vertical direction are the same. Furthermore, the distances d between the central axis M1 of Rogowski coil 21_1 and the central axis M2 of Rogowski coil 21_2, the distances d between the central axis M2 of Rogowski coil 21_2 and the central axis M3 of Rogowski coil 21_3, and the distances d between the central axis M3 of Rogowski coil 21_3 and the central axis M4 of Rogowski coil 21_4 are the same.

[0078] Furthermore, in the first embodiment, the return line 21_1_R of the outermost Rogowski coil 21_1 is located closer to the outermost side than the central axis M1 of the Rogowski coil 21_1, and the return line 21_4_R of the innermost Rogowski coil 21_4 is located closer to the innermost side than the central axis M4 of the Rogowski coil 21_4. Accordingly, a region is formed at the overlapping portion OV where the distance between the return lines of adjacent Rogowski coils is longer than the distance d between the central axes of adjacent Rogowski coils. Specifically, in this embodiment, the return line 21_2_R of the middle layer Rogowski coil 21_2 is located on the central axis M2 of the Rogowski coil 21_2, and the return line 21_3_R of the middle layer Rogowski coil 21_3 is located on the central axis M3 of the Rogowski coil 21_3. Accordingly, the distance between the return lines 21_1_R and 21_2_R of adjacent Rogowski coils, and the distance between the return lines 21_3_R and 21_4_R of adjacent Rogowski coils, is longer than the distance d between the central axes of adjacent Rogowski coils. Therefore, according to this method, the influence of the current flowing through one return line on the other return line can be reduced between return lines 21_1_R and 21_2_R, and between return lines 21_3_R and 21_4_R, thereby improving the accuracy of current measurement.

[0079] Figure 13 The diagram is an abstract representation of the Rogowski coils 21_1, 21_2, 21_3 and 21_4 arranged in the depth direction of the multilayer printed circuit board 400A in the second method.

[0080] exist Figure 13 Similarly, Rogowski coil 21_1 is the outermost Rogowski coil, Rogowski coil 21_4 is the innermost Rogowski coil, and Rogowski coils 21_2 and 21_3 are the intermediate Rogowski coils located between the outermost and innermost layers. Furthermore, all Rogowski coils have the same dimensions in the depth direction, and the distances d between the central axis M1 of Rogowski coil 21_1 and the central axis M2 of Rogowski coil 21_2, the central axis M2 of Rogowski coil 21_2 and the central axis M3 of Rogowski coil 21_3, and the central axis M3 of Rogowski coil 21_3 and the central axis M4 of Rogowski coil 21_4 are the same.

[0081] In this second method, the return line 21_1_R of the outermost Rogowski coil 21_1 is located closer to the outermost side than the central axis M1 of the Rogowski coil 21_1, and the return line 21_4_R of the innermost Rogowski coil 21_4 is located closer to the innermost side than the central axis M4 of the Rogowski coil 21_4. Furthermore, in this second method, the return lines 21_2_R and 21_3_R of the middle Rogowski coil 21_2 and 21_3_R of the middle Rogowski coil 21_3 are located at two positions where the interval D between the outermost Rogowski coil 21_1_R and the innermost Rogowski coil 21_4_R is divided into three equal parts (Ma-1). According to this method, the distances between adjacent return lines 21_1_R and 21_2_R, between adjacent return lines 21_2_R and 21_3_R, and between adjacent return lines 21_3_R and 21_4_R can all be extended to the maximum extent, making these distances longer than the distance d between adjacent central axes. Therefore, according to this method, the influence of current flowing through one return line on the other return line can be reduced between return lines 21_1_R and 21_2_R, between return lines 21_2_R and 21_3_R, and between return lines 21_3_R and 21_4_R, thereby improving the accuracy of current measurement. Thus, the accuracy of current measurement performed by four Rogowski coils can be improved.

[0082] <Other Implementation Methods>

[0083] The above description describes one embodiment of the present invention, but other embodiments are also contemplated in this invention. For example, they are described below.

[0084] (1) In the above embodiment, a Rogowski coil is provided in the current path on the source side of the power switching element connected in parallel, but a Rogowski coil can also be provided in the current path on the drain side of the power switching element.

[0085] (2) In the above embodiment, the current detection value is obtained by integrating the detection signal obtained from the Rogowski coil, and the determination of whether it is related to a short circuit fault is made by comparing the current detection value with a threshold th. However, it is also possible to make the determination of whether it is related to a short circuit fault by comparing the detection signal obtained from the Rogowski coil with a threshold instead.

[0086] (3) This invention can also be applied to power conversion devices other than inverters such as DC / DC converters.

[0087] (4) In the above embodiments, MOSFET is used as an example of power switching element, but the power switching element is not limited to this. For example, it can also be other power switching elements such as IGBT (Insulated Gate Bipolar Transistor).

[0088] Explanation of reference numerals in the attached figures

[0089] 100: Power conversion device; 200: Host device; 2a, 2b: Drive unit; 1: Control unit; 20_1, 20_2, 20_3, 20_4: Switching element unit; 27: Power switching element; 28: Diode; 24: Drive control unit; 50: Short circuit protection device; 21_1, 21_2, 21_3, 21_4: Rogowski coil; 21_1_C, 21_2_C, 21_3_C: Coil; 21_1_R, 21_2_R, 21_3_R 21_4_R: Return line; 22_1, 22_2, 22_3: Integrators; 23: Short circuit detection unit; 301, 302, 303: Comparators; 340: OR operator; 311, 312, 313, 314: NOT operator; 321, 322, 323, 324: AND operator; 331, 332, 333, 334: On-delay operator; 400: Substrate; 400a: Multilayer printed circuit board; M1, M2, M3, M4: Central axis.

Claims

1. A short-circuit protection device, which is a short-circuit protection device for a power conversion device that supplies power to a load via M switching elements connected in parallel, characterized in that it has: There are Ma current detectors, where Ma is 1 less than M, i.e., Ma = M-1. Ma is an integer greater than or equal to 3; Ma Rogowski coils, wherein the Ma Rogowski coils respectively surround the current path of two or more of the M switching element sections; as well as The short-circuit detection unit, upon determining, based on the detection signals obtained from each of the Ma current detectors, that a short-circuit fault exists in the M switching element sections, outputs a cut-off indication signal to stop the on-drive of each of the M switching element sections. Among the Ma current detectors, the Nth current detector detects the sum of the currents flowing through all switching element sections from the 1st to the Mth switching element sections, excluding the Nth switching element section, where N is an integer from 1 to Ma. If the short-circuit detection unit determines that a short-circuit fault exists in the Mth switching element section when all detection signals obtained from the Ma current detectors exceed the threshold, and if the detection signal obtained from one of the Ma current detectors does not exceed the threshold, but the detection signals obtained from the other Ma-1 current detectors exceed the threshold, it determines that a short-circuit fault exists in the switching element section that is not the current detection target of that particular current detector. The Ma Rogowski coils are mounted on a multilayer printed circuit board. The multilayer printed circuit board contains overlapping portions formed by the arrangement of the Ma Rogowski coils in the depth direction. The return line of the Rogowski coil located on the outermost side of the multilayer printed circuit board among the Ma Rogowski coils is located closer to the outermost side than the central axis of the outermost Rogowski coil. The return line of the Rogowski coil located on the innermost layer side of the multilayer printed circuit board among the Ma Rogowski coils is located closer to the innermost layer side than the central axis of the innermost Rogowski coil. The overlapping portion is formed in a region where the distance between the return lines of adjacent Rogowski coils in the depth direction is greater than the distance between the central axes of the adjacent Rogowski coils.

2. The short-circuit protection device according to claim 1, characterized in that, The return line of the Rogowski coil in the intermediate layer located between the outermost and innermost layers is located at the same position as the central axis of the Rogowski coil in the intermediate layer.

3. The short-circuit protection device according to claim 1, characterized in that, The return line of the Rogowski coil in the intermediate layer between the outermost and innermost layers is located at a position that divides the interval between the return lines of the Rogowski coils on the outermost and innermost layers into Ma-1 equal parts.

4. The short-circuit protection device according to any one of claims 1 to 3, characterized in that, Each of the M switching element sections includes a wide-bandgap semiconductor element.

5. A short-circuit protection device, which is a short-circuit protection device for a power conversion device that supplies power to a load via M switching elements connected in parallel, characterized in that it has: There are Ma current detectors, where Ma is 1 less than M, i.e., Ma = M-1. Ma is an integer greater than or equal to 3; Ma Rogowski coils, wherein the Ma Rogowski coils respectively surround the current path of two or more of the M switching element sections; as well as The short-circuit detection unit, upon determining that a short-circuit fault exists in the M switching element sections based on the current detection values ​​obtained from each of the Ma current detectors, outputs a cut-off indication signal to stop the on-drive of each of the M switching element sections. Among the Ma current detectors, the Nth current detector detects the sum of the currents flowing through all switching element sections from the 1st to the Mth switching element sections, excluding the Nth switching element section, where N is an integer from 1 to Ma. If the short-circuit detection unit determines that a short-circuit fault exists in the Mth switching element section when all current detection values ​​obtained from the Ma current detectors exceed the threshold, and if the current detection value obtained from one of the Ma current detectors does not exceed the threshold, but the current detection values ​​obtained from the other Ma-1 current detectors exceed the threshold, it determines that a short-circuit fault exists in the switching element section that is not the current detection target of that particular current detector. The Ma Rogowski coils are mounted on a multilayer printed circuit board. The multilayer printed circuit board contains overlapping portions formed by the arrangement of the Ma Rogowski coils in the depth direction. The return line of the Rogowski coil located on the outermost side of the multilayer printed circuit board among the Ma Rogowski coils is located closer to the outermost side than the central axis of the outermost Rogowski coil. The return line of the Rogowski coil located on the innermost layer side of the multilayer printed circuit board among the Ma Rogowski coils is located closer to the innermost layer side than the central axis of the innermost Rogowski coil. The overlapping portion is formed in a region where the distance between the return lines of adjacent Rogowski coils in the depth direction is greater than the distance between the central axes of the adjacent Rogowski coils.

6. The short-circuit protection device according to claim 5, characterized in that, The return line of the Rogowski coil in the intermediate layer located between the outermost and innermost layers is located at the same position as the central axis of the Rogowski coil in the intermediate layer.

7. The short-circuit protection device according to claim 5, characterized in that, The return line of the Rogowski coil in the intermediate layer between the outermost and innermost layers is located at a position that divides the interval between the return lines of the Rogowski coils on the outermost and innermost layers into Ma-1 equal parts.

8. The short-circuit protection device according to any one of claims 5 to 7, characterized in that, Each of the M switching element sections includes a wide-bandgap semiconductor element.

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