Short-circuit protection device for a power conversion device

Abstract

To reduce the increase in cost and size of a power conversion device caused by short-circuit protection when a plurality of switching elements are connected in parallel.SOLUTION: A short-circuit protection device 50 of a power conversion device 100 is provided that supplies power to a load via a plurality of switching element units 20_1 to 20_3 connected in parallel. The short-circuit protection device 50 includes a short-circuit determination unit 23 that determines that there is short-circuit fault in the plurality of switching element units by Rogowski coils 21_1, 21_2, and 21 _3 that detect a sum of a current flowing through two or more switching element units in the plurality of switching element units to output detection signals Vi1, Vi2, and Vi3 indicating detection results, and outputs a cutoff instruction signal Fx for stopping on / off drive of the plurality of switching element units. In the short-circuit protection device 50, distance between return lines of adjacent Rogowski coils is adapted to be longer.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a short-circuit protection device for a power conversion device.

Background Art

[0002] In a power conversion device that drives a load such as a motor, an excessive current may flow through a semiconductor switching element that constitutes the power conversion device. If such an excessive current flows over a long period of time, the semiconductor switching element may be damaged. Therefore, a short-circuit protection device that detects an excessive current flowing through the semiconductor switching element and stops the power conversion device is provided in the power conversion device.

[0003] In the technology disclosed in Patent Document 1, for each of a plurality of arms each including a voltage-driven semiconductor element, a current detector that detects the current flowing through each arm is provided, and when the arm current of the voltage-driven semiconductor element that each drives exceeds a predetermined value, short-circuit protection is performed by turning off the gate pulse output by the gate drive means.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, in a power conversion device, in order to increase the capacity, a plurality of switching elements may be connected in parallel to form each arm. In this case, since a current detector is required for each switching element, there is a concern that it may lead to an increase in cost and a larger size of the device.

[0006] This invention has been made in view of the problems described above, and an object thereof is to reduce an increase in the cost of a power conversion device and an increase in the size of the device that occur for short-circuit protection when a plurality of switching elements are connected in parallel.

Means for Solving the Problems

[0007] The short-circuit protection device for a power conversion device according to the present invention is a short-circuit protection device for a power conversion device that supplies power to a load through a plurality of switching element units connected in parallel. It includes Ma = M - 1 current detectors, which is one less than the number M of the plurality of switching element units, and each of the Ma current detectors includes a Rogowski coil that surrounds the current paths of two or more switching element units among the plurality of switching element units. Based on the detection signals obtained from the Ma current detectors, a short-circuit determination unit determines that there is a short-circuit fault in the plurality of switching element units and outputs a cutoff instruction signal to stop the on / off drive of the plurality of switching element units. The Nth (where N is an integer from 1 to Ma) current detector among the Ma current detectors detects the sum of the currents flowing through all the switching element units except the Nth switching element unit among the switching element units from the 1st to the Mth. When all the current detection values by the Ma current detectors exceed a threshold value, the short-circuit determination unit determines that there is a short-circuit fault in the Mth switching element unit. When the current detection value of one of the Ma current detectors does not exceed the threshold value and the current detection values of the other Ma - 1 current detectors exceed the threshold value, it is determined that there is a short-circuit fault in the switching element unit that is not the current detection target in the one current detector. Ma is 3 or more. The Ma Rogowski coils are mounted on a multilayer printed circuit board. The multilayer printed circuit board has an overlapping portion where the Ma Rogowski coils are arranged in the depth direction. By positioning the return wire of the Rogowski coil on the outermost layer side of the multilayer printed circuit board on the outermost layer side with respect to the central axis of the Rogowski coil and positioning the return wire of the Rogowski coil on the innermost layer side of the multilayer printed circuit board on the innermost layer side with respect to the central axis of the Rogowski coil, a region where the distance between the return wires of the adjacent Rogowski coils in the depth direction is longer than the distance between the central axes of the adjacent Rogowski coils is formed in the overlapping portion.

Effect of the Invention

[0008] According to the present invention, a short-circuit failure of a current detector can be detected by a smaller number of current detectors than the number of switching element units, and the switching element unit in which the short-circuit failure has occurred can be specified. When a plurality of switching element units are connected in parallel, an increase in the cost of the power conversion device and an increase in the size of the device that occur for short-circuit protection can be reduced. Further, in an overlapping portion where Ma Rogowski coils are arranged in the depth direction, a region where the distance between return lines of adjacent Rogowski coils in the depth direction is longer than the distance between the central axes of the adjacent Rogowski coils is formed in the overlapping portion. Therefore, when a current flows through one return line, the influence of the current on other return lines adjacent to the return line can be reduced, and the accuracy of current measurement can be improved.

Brief Description of the Drawings

[0009]

Figure 1

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Embodiment for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram showing the configuration of a power conversion device 100 provided with a short-circuit protection device 50 which is an embodiment of this invention. The power conversion device 100 includes a control unit 1 that controls each part of the power conversion device 100 according to a command from a higher-level device 200, and drive units 2a and 2b that convert power.

[0011] In the present embodiment, the power conversion device 100 is a device corresponding to one phase of an inverter. In FIG. 1, drive units 2a and 2b for one phase in this inverter are shown. The drive unit 2a is connected between a high-potential power line 101 connected to the positive electrode of a DC power supply (not shown) and an output terminal 103 connected to a load (not shown). Also, the drive unit 2b is connected between a low-potential power line 102 connected to the negative electrode of the same DC power supply and the same output terminal 103. Note that the power conversion device 100 constitutes an inverter by parallel-connecting drive units 2a and 2b for a plurality of phases between the high-potential power line 101 and the low-potential power line 102.

[0012] Hereinafter, the internal configuration of the drive unit 2a will be described. Since the internal configuration of the drive unit 2b is basically the same as that of the drive unit 2a, its description will be omitted.

[0013] The drive unit 2a includes a plurality of 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.

[0014] Each of the switching element units 20_1, 20_2, 20_3, and 20_4 includes a power switching element 27. This power switching element 27 is a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), and is composed of a wide-gap semiconductor element such as SiC or GaN. A diode 28 is connected in anti-parallel to the power switching element 27. The drive unit 2b also includes a plurality of switching element units connected in parallel, similar to the drive unit 2a. The power conversion device 100 supplies power to a load connected to the output terminal 103 via the plurality of switching element units connected in parallel in each of these drive units 2a and 2b.

[0015] Based on the control signal Sm1 supplied from the control unit 1, the drive control unit 24 outputs a drive signal Son / off for switching the power switching elements 27 of the switching element units 20_1, 20_2, 20_3, and 20_4 from off to on or from on to off. Also, when a cutoff instruction signal Fx is output from the short-circuit protection device 50, the drive control unit 24 outputs a drive signal Son / off for turning off the power switching elements 27 of the switching element units 20_1, 20_2, 20_3, and 20_4.

[0016] The short-circuit protection device 50 is a device that detects the occurrence of a short-circuit fault in the switching element units 20_1, 20_2, 20_3, and 20_4 connected in parallel and protects the switching element units 20_1, 20_2, 20_3, and 20_4 from the short-circuit fault. As shown in FIG. 1, 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 determination unit 23. The short-circuit faults in the switching element unit 20_1 or the like may include an accidental turn-on or short-circuit fault of the power switching element 27 and a short-circuit fault of the diode 28.

[0017] The Rogowski coils 21_1, 21_2, and 21_3 are Ma number of current detectors that are one less than the number M (M = 4 in this example) of a plurality of switching element sections connected in parallel. Specifically, Ma = M - 1 = 3 current detectors that detect the sum of currents flowing through two or more switching element sections among the plurality of switching element sections and output a detection signal indicating the detection result. The Ma Rogowski coils of the Ma current detectors each surround the current paths of two or more switching element sections in the M switching element sections. In the present embodiment, the Rogowski coils 21_1, 21_2, and 21_3 are provided in the current paths on the source side of the power switching elements 27 of the switching element sections 20_1, 20_2, 20_3, and 20_4.

[0018] In the present embodiment, the Nth (N is an integer from 1 to Ma) current detector among the Ma current detectors detects the sum of currents flowing through all the switching element sections other than the Nth switching element section among the switching element sections from the 1st to the Mth.

[0019] Specifically, in the present embodiment, the 1st switching element section is the switching element section 20_1, the 2nd switching element section is the switching element section 20_2, the 3rd switching element section is the switching element section 20_3, and the 4th switching element section is the switching element section 20_4. And the 1st current detector is the Rogowski coil 21_1, the 2nd current detector is the Rogowski coil 21_2, and the 3rd current detector is the Rogowski coil 21_3.

[0020] The Rogowski coil 21_1, which is 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 10_1, detects the sum of the currents flowing through these current paths, and outputs a detection signal Vi1 indicating the detection result to the integrator 22_1. This detection signal Vi1 indicates 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 generates a current detection value Si1 indicating the sum of the currents flowing through the switching element sections 20_2, 20_3, and 20_4 by integrating the detection signal Vi1, and outputs it to the short-circuit determination section 23.

[0021] The Rogowski coil 21_2, which is 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, detects the sum of the currents flowing through these current paths, and outputs a detection signal Vi2 indicating the detection result to the integrator 22_2. This detection signal Vi2 indicates 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 generates a current detection value Si2 indicating the sum of the currents flowing through the switching element sections 20_1, 20_3, and 20_4 by integrating the detection signal Vi2, and outputs it to the short-circuit determination section 23.

[0022] The Rogowski coil 21_3, which is 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, detects the sum of the currents flowing through these current paths, and outputs a detection signal Vi3 indicating the detection result to the integrator 22_3. This detection signal Vi3 indicates 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 generates a current detection value Si3 indicating the sum of the currents flowing through the switching element sections 20_1, 20_2, and 20_4 by integrating the detection signal Vi3, and outputs it to the short-circuit determination section 23.

[0023] The short-circuit determination unit 23 determines whether there is a short-circuit failure in the switching element units 20_1, 20_2, 20_3, and 20_4 based on the current detection values Si1, Si2, and Si3. When the short-circuit determination unit 23 determines that a short-circuit failure has occurred in the switching element unit 20_1, it outputs a short-circuit failure signal F1. When it determines that a short-circuit failure has occurred in the switching element unit 20_2, it outputs a short-circuit failure signal F2. When it determines that a short-circuit failure has occurred in the switching element unit 20_3, it outputs a short-circuit failure signal F3. When it determines that a short-circuit failure has occurred in the switching element unit 20_4, it outputs a short-circuit failure signal F4 to the control unit 1. The control unit 1 transmits this short-circuit failure signal F1, F2, F3, or F4 to the host device 200. As a result, the host device 200 performs processing such as displaying information identifying the switching element unit 20_1, 20_2, 20_3, or 20_4 in which the short-circuit failure has occurred on, for example, a display unit. Further, when the short-circuit determination unit 23 determines that a short-circuit failure has occurred in any of the switching element units 20_1, 20_2, 20_3, or 20_4, it outputs a cut-off instruction signal Fx to the drive control unit 24. Thereby, the drive control unit 24 stops the on / off drive of the power switching elements 27 of the switching element units 20_1, 20_2, 20_3, and 20_4.

[0024] FIG. 2 is a block diagram showing a configuration example of the short-circuit determination unit 23. As shown in FIG. 2, the short-circuit determination 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 an OR operator 340. The on-delay operators 331, 332, 333, and 334 are operators that delay the change of the input signal from the non-active level to the active level by a predetermined time and output it, and play a role in stabilizing the operation of the short-circuit determination unit 23.

[0025] When the current detection value Si1 indicating the sum of the currents of the switching element units 20_2, 20_3, and 20_4 does not exceed the short-circuit current determination threshold th, the comparator 301 sets the output signal to the non-active level, and when it exceeds, sets it to the active level. When the current detection value Si2 indicating the sum of the currents of the switching element units 20_1, 20_3, and 20_4 does not exceed the short-circuit current determination threshold th, the comparator 302 sets the output signal to the non-active level, and when it exceeds, sets it to the active level. When the current detection value Si3 indicating the sum of the currents of the switching element units 20_1, 20_2, and 20_4 does not exceed the short-circuit current determination threshold th, the comparator 303 sets the output signal to the non-active level, and when it exceeds, sets it to the active level. In this case, the short-circuit current determination threshold th may be, for example, 300% of the rated power switching element current or the like.

[0026] The NOT operator 311 inverts and outputs the level of the output signal of the comparator 301. The NOT operator 312 inverts and outputs the level of the output signal of the comparator 302. The NOT operator 313 inverts and outputs the level of the output signal of the comparator 303.

[0027] When at least one of the output signals of the comparators 301, 302, and 303 is at the active level, that is, when at least one of the sum of the currents of the switching element units 20_2, 20_3, and 20_4, the sum of the currents of the switching element units 20_1, 20_3, and 20_4, and the sum of the currents of the switching element units 20_1, 20_2, and 20_4 exceeds the short-circuit current determination threshold th, it is determined that a short-circuit fault has occurred in any one of the switching element units 20_1, 20_2, 20_3, or 20_4, and the cut-off instruction signal Fx is output to the drive control unit 24.

[0028] The AND operator 321 determines that a short - circuit fault has occurred in the switching element section 20_1 when the output signal of the NOT operator 311 is at the active level and the output signals of the comparators 302 and 303 are at the active level, that is, when the sum of the currents of the switching element sections 20_2, 20_3, and 20_4 does not exceed the short - circuit current determination threshold th, and when both the sum of the currents of the switching element sections 20_1, 20_3, and 20_4 and the sum of the currents of the switching element sections 20_1, 20_2, and 20_4 exceed the short - circuit current determination threshold th. Then, it outputs a short - circuit fault signal F1 to the control unit 1 via the on - delay operator 331. In this way, 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 in one current detector when the current detection value of one of the Ma current detectors (in this example, the current detection value Si1 obtained by the Rogowski coil 21_1) does not exceed the threshold value and the current detection values of the other Ma - 1 current detectors (in this example, the current detection values Si2 and Si3 obtained by the Rogowski coils 21_2 and 21_3) exceed the threshold value.

[0029] The AND operator 322 determines that a short-circuit fault has occurred in the switching element section 20_2 when the output signal of the NOT operator 312 is at the active level and the output signals of the comparators 301 and 303 are at the active level, that is, when the sum of the currents in the switching element sections 20_1, 20_3, and 20_4 does not exceed the short-circuit current determination threshold th, and when both the sum of the currents in the switching element sections 20_2, 20_3, and 20_4 and the sum of the currents in the switching element sections 20_1, 20_2, and 20_4 exceed the short-circuit current determination threshold th. Then, the AND operator 322 outputs a short-circuit fault signal F2 to the control unit 1 via the on-delay operator 332. In this way, when the current detection value of one of the Ma current detectors (in this example, the current detection value Si2 obtained by the Rogowski coil 21_2) does not exceed the threshold value and the current detection values of the other Ma - 1 current detectors (in this example, the current detection values Si1 and Si3 obtained by the Rogowski coils 21_1 and 21_3) exceed the threshold value, 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 target of current detection in the one current detector.

[0030] The AND operator 323 determines that a short - circuit fault has occurred in the switching element section 20_3 when the output signal of the NOT operator 313 is at the active level and the output signals of the comparators 301 and 302 are at the active level, that is, when the sum of the currents of the switching element sections 20_1, 20_2, and 20_4 does not exceed the short - circuit current determination threshold th, and both the sum of the currents of the switching element sections 20_2, 20_3, and 20_4 and the sum of the currents of the switching element sections 20_1, 20_3, and 20_4 exceed the short - circuit current determination threshold th. Then, it outputs a short - circuit fault signal F3 to the control unit 1 via the on - delay operator 333. In this way, when the current detection value of one of the Ma current detectors (in this example, the current detection value Si3 obtained by the Rogowski coil 21_3) does not exceed the threshold value and the current detection values of the other Ma - 1 current detectors (in this example, the current detection values Si1 and Si2 obtained by the Rogowski coils 21_1 and 21_2) exceed the threshold value, 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 in the one current detector.

[0031] The AND operator 324 determines that a short - circuit fault has occurred in the switching element section 20_4 when the output signals of all of the comparators 301, 302, and 303 are at the active level, that is, when all of the sum of the currents of the switching element sections 20_2, 20_3, and 20_4, the sum of the currents of the switching element sections 20_1, 20_3, and 20_4, and the sum of the currents of the switching element sections 20_1, 20_2, and 20_4 exceed the short - circuit current determination threshold th. Then, it outputs a short - circuit fault signal F4 to the control unit 1 via the on - delay operator 334. In this way, when all of the current detection values (in this example, the current detection values Si1, Si2, and Si3 obtained by the Rogowski coils 21_1, 20_2, and 21_3) by the Ma current detectors exceed the threshold value th, the AND operator 324 determines that there is a short - circuit fault in the M - th switching element section (in this example, the switching element section 20_4).

[0032] Figures 3 to 6 are waveform diagrams showing operation examples at the time of short-circuit fault detection in each embodiment. Hereinafter, the operation of this embodiment will be described with reference to these figures.

[0033] In the operation example shown in FIG. 3, a short-circuit fault occurs in the switching element unit 20_1. Before this short-circuit fault occurs, during normal operation, the current detection value Si1 indicating the sum of the currents of the switching element units 20_2, 20_3, and 20_4 is lower than the short-circuit current determination threshold th. Also, the current detection value Si2 indicating the sum of the currents of the switching element units 20_1, 20_3, and 20_4 is also lower than the short-circuit current determination threshold th. Further, the current detection value Si3 indicating the sum of the currents of the switching element units 20_1, 20_2, and 20_4 is also lower than the short-circuit current determination threshold th.

[0034] When a short-circuit fault occurs in the switching element unit 20_1, the current flowing through the switching element unit 20_1 becomes larger than during normal operation. In this case, the current detection value Si2 indicating the sum of the currents of the switching element units 20_1, 20_3, and 20_4 and the current detection value Si3 indicating the sum of the currents of the switching element units 20_1, 20_2, and 20_4 exceed the short-circuit current determination threshold th, and the current detection value Si1 indicating the sum of the currents of the switching element units 20_2, 20_3, and 20_4 does not exceed the short-circuit current determination threshold th. For this reason, the cutoff instruction signal Fx and the short-circuit fault signal F1 specifying the switching element unit 20_1 as the short-circuit fault location become active levels.

[0035] In the operation example shown in FIG. 4, a short-circuit fault occurs in the switching element unit 20_2. The normal operation before this short-circuit fault occurs is the same as the operation example in FIG. 3.

[0036] When a short - circuit fault occurs in the switching element section 20_2, the current flowing through the switching element section 20_2 becomes larger than normal. In this case, the current detection value Si1 indicating the sum of the currents of the switching element sections 20_2, 20_3, and 20_4 and the current detection value Si3 indicating the sum of the currents of the switching element sections 20_1, 20_2, and 20_4 exceed the short - circuit current determination threshold value th, and the current detection value Si2 indicating the sum of the currents of the switching element sections 20_1, 20_3, and 20_4 does not exceed the short - circuit current determination threshold value th. Therefore, the cutoff instruction signal Fx and the short - circuit fault signal F2 identifying the switching element section 20_2 as the short - circuit fault location become active levels.

[0037] In the operation example shown in FIG. 5, a short - circuit fault occurs in the switching element section 20_3. The normal operation before this short - circuit fault occurs is the same as the operation example in FIG. 3.

[0038] When a short - circuit fault occurs in the switching element section 20_3, the current flowing through the switching element section 20_3 becomes larger than normal. In this case, the current detection value Si1 indicating the sum of the currents of the switching element sections 20_2, 20_3, and 20_4 and the current detection value Si2 indicating the sum of the currents of the switching element sections 20_1, 20_3, and 20_4 exceed the short - circuit current determination threshold value th, and the current detection value Si3 indicating the sum of the currents of the switching element sections 20_1, 20_2, and 20_4 does not exceed the short - circuit current determination threshold value th. Therefore, the cutoff instruction signal Fx and the short - circuit fault signal F3 identifying the switching element section 20_3 as the short - circuit fault location become active levels.

[0039] In the operation example shown in FIG. 6, a short - circuit fault occurs in the switching element section 20_4. The normal operation before this short - circuit fault occurs is the same as the operation example in FIG. 3.

[0040] When a short-circuit fault occurs in the switching element unit 20_4, the current flowing through the switching element unit 20_4 becomes larger than that in the normal state. In this case, all of the current detection value Si1 indicating the sum of the currents of the switching element units 20_2, 20_3, and 20_4, the current detection value Si2 indicating the sum of the currents of the switching element units 20_1, 20_3, and 20_4, and the current detection value Si3 indicating the sum of the currents of the switching element units 20_1, 20_2, and 20_4 exceed the short-circuit current determination threshold th. Therefore, the cutoff instruction signal Fx and the short-circuit fault signal F4 specifying the switching element unit 20_4 as the short-circuit fault location become active levels.

[0041] As described above, according to the present embodiment, the short-circuit faults of each switching element unit are detected by three Rogowski coils 21_1, 21_2, and 21_3, which are one less than the number of parallel switching element units 20_1, 20_2, 20_3, and 20_4, i.e., four, to stop the driving of the switching element units 20_1, 20_2, 20_3, and 20_4, and the switching element unit that is the short-circuit fault location can be specified. Therefore, when a plurality of switching element units are connected in parallel, an increase in the cost of the power conversion device 100 and an increase in the size of the device that occur for short-circuit protection can be reduced. Further, in the present embodiment, the three Rogowski coils 21_1, 21_2, and 21_3 all detect the sum of the currents of the three switching element units. Therefore, the current detection accuracy of each Rogowski coil can be made the same, and the short-circuit faults of each switching element unit can be accurately determined.

[0042] Next, an example of a Rogowski coil suitable for the present embodiment will be described. FIG. 7 is a perspective view illustrating the Rogowski coils 21_1, 21_2, and 21_3 mounted on the substrate 400. In this example, the Rogowski coils 21_1, 21_2, and 21_3 are mounted on the substrate 400 in a state where they overlap at the overlapping portion OV.

[0043] In this substrate 400, the current path 20_1a of the switching element section 20_1 is inserted into the region surrounded by the Rogowski coils 21_2 and 20_3 and not surrounded by the Rogowski coil 21_1. Also, in the substrate 400, the current path 20_2a of the switching element section 20_2 is inserted into the region surrounded by the Rogowski coils 21_1 and 21_3 and not surrounded by the Rogowski coil 21_2. Also, in the substrate 400, the current path 20_3a of the switching element section 20_3 is inserted into the region surrounded by the Rogowski coils 21_1 and 21_2 and not surrounded by the Rogowski coil 21_3. Also, in the substrate 400, the current path 20_4a of the switching element section 20_4 is inserted into the region surrounded by all of the Rogowski coils 21_1, 21_2, and 21_3. In this case, an overlapping portion OV where the three Rogowski coils 21_1, 21_2, and 21_3 overlap in the depth direction of the substrate 400 is generated below the current paths 20_2a, 20_3a, and 20_4a, to the right of the current path 20_4a, and above the current path 20_4a in FIG. 7.

[0044] The Rogowski coil 21_1 surrounds the current paths 20_2a, 20_3a, and 20_4a and detects the sum of the currents of the switching element sections 20_2, 20_3, and 20_4 flowing through these current paths. Also, the Rogowski coil 21_2 surrounds the current paths 20_1a, 20_3a, and 20_4a and detects the sum of the currents of the switching element sections 20_1, 20_3, and 20_4 flowing through these current paths. Also, the Rogowski coil 21_3 surrounds the current paths 20_1a, 20_2a, and 20_4a and detects the sum of the currents of the switching element sections 20_1, 20_2, and 20_4 flowing through these current paths.

[0045] FIG. 8 is a plan view illustrating the Rogowski coil 21_1. As shown in FIG. 8, the Rogowski coil 21_1 has a coil 21_1_C extending in a spiral shape and a return line 21_1_R that returns from the end point to the start point of the coil 21_1_C inside the coil. Although not shown, the Rogowski coils 21_2 and 21_3 also have the same configuration as the Rogowski coil 21_1.

[0046] FIG. 9 is a perspective view showing an implementation example of the Rogowski coils 21_1, 21_2, and 21_3 in the overlapping portion OV of FIG. 7. In FIG. 9, the Rogowski coils 21_1, 21_2, and 21_3 are mounted on a multilayer printed circuit board 400a.

[0047] On the first layer L1 of the multilayer printed circuit board 400a, a lower horizontal portion of the coil 21_3_C of the Rogowski coil 21_3 is formed. On the second layer L2 above the first layer L1, the return line 21_3_R of the Rogowski coil 21_3 is formed. On the third layer L3 above the second layer L2, an upper horizontal portion of the coil 21_3_C of the Rogowski coil 21_3 is formed. Then, a vertical portion connecting the upper horizontal portion and the lower horizontal portion of the coil 21_3_C is formed using a through hole TH3-1 connecting the third layer L3 and the first layer L1.

[0048] On the fourth layer L4 above the third layer L3, a lower horizontal portion of the coil 21_2_C of the Rogowski coil 21_2 is formed. On the fifth layer L5 above the fourth layer L4, the return line 21_2_R of the Rogowski coil 21_2 is formed. On the sixth layer L6 above the fifth layer L5, an upper horizontal portion of the coil 21_2_C of the Rogowski coil 21_2 is formed. Then, a vertical portion connecting the upper horizontal portion and the lower horizontal portion of the coil 21_2_C is formed using a through hole TH6-4 connecting the sixth layer L6 and the fourth layer L4.

[0049] On the seventh layer L7 above the sixth layer L6, a lower horizontal portion of the coil 21_1_C of the logos key coil 21_1 is formed. On the eighth layer L8 above the seventh layer L7, a return wire 21_1_R of the logos key coil 21_1 is formed. On the ninth layer L9 above the eighth layer L8, an upper horizontal portion of the coil 21_1_C of the logos key coil 21_1 is formed. Then, a vertical portion connecting the upper horizontal portion and the lower horizontal portion of the coil 21_1_C is formed using a through hole TH9-7 connecting the ninth layer L9 and the seventh layer L7.

[0050] Figure 10 is a diagram abstractly showing the logos key coils 21_1, 21_2, and 21_3 shown in Figure 9. In each layer of the multilayer printed circuit board 400a shown in Figure 9, the ninth layer L9 is the outermost layer side, and the first layer L1 is the innermost layer side. Therefore, in the logos key coils 21_1, 21_2, and 21_3 shown in Figure 10, the logos key coil 21_1 is the outermost layer side logos key coil, the logos key coil 21_3 is the innermost layer side logos key coil, and the logos key coil 21_2 is the logos key coil of the intermediate layer between the outermost layer and the innermost layer.

[0051] In this implementation example, the logos key coils 21_1, 21_2, and 21_3 have the same size in the depth direction (the vertical direction in Figure 10). Also, the distance d between the central axis M1 of the logos key coil 21_1 and the central axis M2 of the logos key coil 21_2 is the same as the distance d between the central axis M2 of the logos key coil 21_2 and the central axis M3 of the logos key coil 21_3.

[0052] And in this implementation example, the return wire 21_1_R of the outermost layer logo ski coil 21_1 is positioned on the outermost layer side with respect to the central axis M1 of the logo ski coil 21_1, and the return wire 21_3_R of the innermost layer logo ski coil 21_3 is positioned on the innermost layer side with respect to the central axis M3 of the logo ski coil 21_3. By doing so, a region where the distance between the return wires of adjacent logo ski coils is longer than the distance between the central axes of the logo ski coils is formed as the overlapping portion OV. Specifically, in this implementation example, the return wire 21_2_R of the middle layer logo ski coil 21_2 is positioned on the central axis M2 of the logo ski coil 21_2, and the distances between the return wires 21_1_R and 21_2_R of adjacent logo ski coils and between the return wires 21_2_R and 21_3_R of adjacent logo ski coils are made longer than the distance d between the central axes of adjacent logo ski coils.

[0053] In this implementation example, the return wire 21_1_R of the logo ski coil 21_1, the return wire 21_2_R of the logo ski coil 21_2, and the return wire 21_3_R of the logo ski coil 21_3 extend in parallel over the entire length of the overlapping portion OV. Therefore, when the return wires 21_1_R and 21_2_R approach each other and the return wires 21_2_R and 21_3_R approach each other, if a current flows through one of these return wires and a magnetic field is generated around the return wire, a current that generates a magnetic field canceling this magnetic field is induced in the adjacent other return wire, which may interfere with current measurement. However, in this implementation example, the return wires 21_1_R and 21_2_R are far apart from each other, and the return wires 21_2_R and 21_3_R are also far apart from each other, and each return wire is less likely to be affected by the current flowing through the adjacent other return wire. For this reason, highly accurate current measurement by the logo ski coils 21_1, 21_2, and 21_3 is possible.

[0054] In the embodiment described above, the number M of the switching element portions connected in parallel was 4, and the number Ma of the logos key coils, where Ma = M - 1, was 3. In the embodiment to be described below, the number M of the switching element portions connected in parallel is 5, and the number Ma of the logos key coils, where Ma = M - 1, is 4. FIG. 11 is a plan view illustrating the logos key coils 21_1, 21_2, 21_3, and 21_4 mounted on the multilayer printed circuit board 400A in this embodiment.

[0055] In the multilayer printed circuit board 400A, the current path 20_1a of the first switching element portion is inserted into the region surrounded by the logos key coils 21_2, 21_3, and 20_4 and not surrounded by the logos key coil 21_1. Also, in the multilayer printed circuit board 400A, the current path 20_2a of the second switching element portion is inserted into the region surrounded by the logos key coils 21_1, 21_3, and 21_4 and not surrounded by the logos key coil 21_2. Also, in the multilayer printed circuit board 400A, the current path 20_3a of the third switching element portion is inserted into the region surrounded by the logos key coils 21_1, 21_2, and 21_4 and not surrounded by the logos key coil 21_3. Also, in the multilayer printed circuit board 400A, the current path 20_4a of the fourth switching element portion is inserted into the region surrounded by the logos key coils 21_1, 21_2, and 21_3 and not surrounded by the logos key coil 21_4. Also, in the multilayer printed circuit board 400A, the current path 20_5a of the fifth switching element portion is inserted into the region surrounded by all of the logos key coils 21_1, 21_2, 21_3, and 21_4. In this case, an overlapping portion OV in which the four logos key coils 21_1, 21_2, 21_3, and 21_4 are arranged in the depth direction of the multilayer printed circuit board 400A is generated above the current paths 20_2a, 20_3a, 20_4a, and 20_5, to the right of the current path 20_5a, and below the current path 20_5a in FIG. 11.

[0056] The Rogowski coil 21_1 surrounds the current paths 20_2a, 20_3a, 20_4a, and 20_5a, and detects the sum of the currents flowing through these current paths. Also, the Rogowski coil 21_2 surrounds the current paths 20_1a, 20_3a, 20_4a, and 20_5a, and detects the sum of the currents flowing through these current paths. Also, the Rogowski coil 21_3 surrounds the current paths 20_1a, 20_2a, 20_4a, and 20_5a, and detects the sum of the currents flowing through these current paths. Also, the Rogowski coil 21_4 surrounds the current paths 20_1a, 20_2a, 20_3a, and 20_5a, and detects the sum of the currents flowing through these current paths.

[0057] In this embodiment, two modes can be considered as the mounting modes of the Rogowski coils 21_1, 21_2, 21_3, and 21_4. FIG. 12 is a diagram abstractly showing 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 mode.

[0058] In the Rogowski coils 21_1, 21_2, 21_3, and 21_4 shown in FIG. 12, the Rogowski coil 21_1 is the Rogowski coil on the outermost layer side, the Rogowski coil 21_4 is the Rogowski coil on the innermost layer side, and the Rogowski coils 21_2 and 21_3 are the Rogowski coils in the intermediate layer between the outermost layer and the innermost layer.

[0059] Even in this mode, the Rogowski coils 21_1, 21_2, 21_3, and 21_4 have the same size in the depth direction (the vertical direction in FIG. 12). Also, the distance d between the central axis M1 of the Rogowski coil 21_1 and the central axis M2 of the Rogowski coil 21_2, the distance d between the central axis M2 of the Rogowski coil 21_2 and the central axis M3 of the Rogowski coil 21_3, and the distance d between the central axis M3 of the Rogowski coil 21_3 and the central axis M4 of the Rogowski coil 21_4 are the same.

[0060] Also, in the first aspect, the return wire 21_1_R of the outermost-layer logo ski coil 21_1 is positioned on the outermost-layer side with respect to the central axis M1 of the logo ski coil 21_1, and the return wire 21_4_R of the innermost-layer logo ski coil 21_4 is positioned on the innermost-layer side with respect to the central axis M4 of the logo ski coil 21_4. By doing so, a region where the distance between the return wires of adjacent logo ski coils is longer than the distance d between the central axes of adjacent logo ski coils is formed as the overlapping portion OV. Specifically, in this aspect, the return wire 21_2_R of the intermediate-layer logo ski coil 21_2 is positioned on the central axis M2 of the logo ski coil 21_2, and the return wire 21_3_R of the intermediate-layer logo ski coil 21_3 is positioned on the central axis M3 of the logo ski coil 21_3, and the distance between the return wires 21_1_R and 21_2_R of adjacent logo ski coils and the distance between the return wires 21_3_R and 21_4_R of adjacent logo ski coils are made longer than the distance d between the central axes of adjacent logo ski coils. Therefore, according to this aspect, between the return wires 21_1_R and 21_2_R and between the return wires 21_3_R and 21_4_R, the influence of the current flowing through one return wire on the other return wire can be reduced, and the accuracy of current measurement can be improved.

[0061] FIG. 13 is a diagram schematically showing the logo ski 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 aspect.

[0062] Also in FIG. 13, the logo ski coil 21_1 is the outermost-layer logo ski coil, the logo ski coil 21_4 is the innermost-layer logo ski coil, and the logo ski coils 21_2 and 21_3 are the intermediate-layer logo ski coils between the outermost layer and the innermost layer. Also, each logo ski coil has the same size in the depth direction, and the distance d between the central axis M1 of the logo ski coil 21_1 and the central axis M2 of the logo ski coil 21_2, the distance d between the central axis M2 of the logo ski coil 21_2 and the central axis M3 of the logo ski coil 21_3, and the distance d between the central axis M3 of the logo ski coil 21_3 and the central axis M4 of the logo ski coil 21_4 are the same.

[0063] Also in this second aspect, the return wire 21_1_R of the outermost layer logo ski coil 21_1 is positioned on the outermost layer side with respect to the central axis M1 of the logo ski coil 21_1, and the return wire 21_4_R of the innermost layer logo ski coil 21_4 is positioned on the innermost layer side with respect to the central axis M4 of the logo ski coil 21_4. Further, in the second aspect, the interval D between the return wire 21_4_R of the innermost layer logo ski coil 21_4 and the return wire 21_4_R of the innermost layer logo ski coil 21_4 is equally divided into Ma - 1 parts, that is, two positions that equally divide it into three parts, and the return wire 21_2_R of the intermediate layer logo ski coil 21_2 and the return wire 21_3_R of the intermediate layer logo ski coil 21_3 are respectively positioned. According to this aspect, all of the distances between adjacent return wires 21_1_R and 21_2_R, between adjacent return wires 21_2_R and 21_3_R, and between adjacent return wires 21_3_R and 21_4_R can be extended to the maximum extent and made longer than the distance d between adjacent central axes. Therefore, according to this aspect, between the return wires 21_1_R and 21_2_R, between the return wires 21_2_R and 21_3_R, and between the return wires 21_3_R and 21_4_R, the influence of the current flowing through one return wire on the other return wire can be reduced, and the accuracy of current measurement can be improved. Thus, the accuracy of current measurement by the four logo ski coils can be improved.

[0064] <Other Embodiments> As described above, one embodiment of the present invention has been described, but other embodiments are also conceivable for the present invention. For example, it is as follows.

[0065] (1) In the above embodiment, a logo ski coil is provided in the current path on the source side of the power switching elements connected in parallel, but a logo ski coil may be provided in the current path on the drain side of the power switching elements.

[0066] (2) In the above embodiment, the detection signal obtained from the Rogowski coil is integrated to obtain a current detection value, and a determination regarding a short-circuit fault is made by comparing this current detection value with a threshold value th. However, instead of doing so, a determination regarding a short-circuit fault may be made by comparing the detection signal obtained from the Rogowski coil with a threshold value.

[0067] (3) The present invention may be applied to a power conversion device other than an inverter, such as a DC / DC converter.

[0068] (4) In the above embodiment, a MOSFET is given as an example of the power switching element, but the power switching element is not limited thereto, and other power switching elements such as an IGBT (Insulated Gate Bipolar Transistor) may be used.

Explanation of Reference Numerals

[0069] 100... Power conversion device, 200... Higher-level device, 2a, 2b... Driving 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 wire, 22_1, 22_2, 22_3... Integrator, 23... Short-circuit determination unit, 301, 302, 303... Comparator, 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. In a short-circuit protection device for a power conversion device that supplies power to a load via a plurality of switching element sections connected in parallel, Ma = M - 1 current detectors, which are one less than the number M of the plurality of switching element sections, and Ma current detectors each including Ma Rogowski coils that respectively surround current paths of two or more switching element sections among the plurality of switching element sections, a short-circuit determination unit that determines that a short-circuit fault has occurred in the plurality of switching element sections based on detection signals obtained from the Ma current detectors and outputs a cutoff instruction signal for stopping the on / off driving of the plurality of switching element sections, the Nth (N is an integer from 1 to Ma) current detector among the Ma current detectors detects the sum of currents flowing through all switching element sections other than the Nth switching element section among the first to Mth switching element sections, when all of the current detection values by the Ma current detectors exceed a threshold value, the short-circuit determination unit determines that a short-circuit fault has occurred in the Mth switching element section, and when the current detection value of one of the Ma current detectors does not exceed the threshold value and the current detection values of the other Ma - 1 current detectors exceed the threshold value, it determines that a short-circuit fault has occurred in the switching element section that is not the current detection target in the one current detector, wherein Ma is 3 or more, the Ma Rogowski coils are mounted on a multilayer printed circuit board, the multilayer printed circuit board has an overlapping portion where the Ma Rogowski coils are arranged in the depth direction, the return wire of the Rogowski coil on the outermost layer side of the multilayer printed circuit board is positioned on the outermost layer side with respect to the central axis of the Rogowski coil, and the return wire of the Rogowski coil on the innermost layer side of the multilayer printed circuit board is positioned on the innermost layer side with respect to the central axis of the Rogowski coil, so that a region where the distance between the return wires of the adjacent Rogowski coils in the depth direction is longer than the distance between the central axes of the adjacent Rogowski coils is formed in the overlapping portion. A short-circuit protection device characterized by this.

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

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

4. The short-circuit protection device according to any one of claims 1 to 3, wherein the switching element section includes a wide-gap semiconductor element.

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