Power module and power conversion device

Abstract

This power module is mounted with: a plurality of switching elements (1)-(4) arranged in parallel to each other in a current path (51); and a control circuit (30) for turning on or off each of the switching elements (1)-(4). The power module comprises: a plurality of sub-modules (10)-(12) configured by grouping the plurality of switching elements (1)-(4) into a plurality of groups; and a short circuit detector (20) disposed in the current path (51) and detecting that a short circuit has occurred in any of the sub-modules (10)-(12). When the short circuit detector (20) detects a short circuit, an ON command is issued within a predetermined ON command issuing time to the switching elements (1)-(4) of the sub-modules (10)-(12) different from the sub-modules (10)-(12) in which the short circuit has occurred.

Description

Power Module and Power Conversion Device

[0001] The present disclosure relates to a power module and a power conversion device.

[0002] As a power conversion device, a power module equipped with a plurality of semiconductor switching elements is used in a converter device, an inverter device, etc. Since a large number of components are packaged in the power module, if a certain switching element short-circuits due to a failure or malfunction among the plurality of switching elements and a current larger than the normal current flows through the short-circuited switching element, causing a temperature rise, it is required to minimize the impact on damage and burnout including the peripheral circuit.

[0003] Therefore, as an in-vehicle converter device, in order to suppress the occurrence of cascade failures when a switching element short-circuits, when it is detected that a short-circuit has occurred in any one of the plurality of switching elements, other switching elements are made conductive to disperse the short-circuit current concentrated on the short-circuited switching element, thereby suppressing failures including the peripheral circuit (see, for example, Patent Document 1). Also, in a semiconductor module, if the switching element melts due to a temperature rise during a short-circuit, it may be destroyed. Therefore, as an explosion-proof structure, it has been proposed to cover the periphery of the semiconductor module with a mechanically or thermally strong ceramic, metal, etc. so that damage does not occur outside the semiconductor module. A technique of performing this explosion-proof treatment on a small semiconductor module and combining a plurality of small semiconductor modules to form a large semiconductor module has been introduced (see, for example, Patent Document 2).

[0004] Japanese Patent Application Laid-Open No. 2020-35661, Japanese Patent Application Laid-Open No. 11-330283

[0005] Power modules are used in consumer, industrial, automotive, power equipment, etc. As the application fields expand, the specifications are diversifying. For example, in the case of a power module that handles high voltage and large current, the number of mounted switching elements tends to increase, and it is required to suppress the occurrence of cascade failures during a short-circuit of the switching element more than before.

[0006] In the technology disclosed in Patent Document 1, the number of switching elements is four, so when distributing the short-circuit current, even if the current from all four elements is concentrated on one temporarily short-circuited switching element, the possibility of the switching element being destroyed is small. However, if the number of switching elements increases, a larger current corresponding to the number of switching elements will be concentrated on the short-circuited switching element, and even if only temporarily, the switching element will heat up to several thousand degrees in a short time, causing melting and arcing, which will destroy not only the short-circuited switching element but also the surrounding circuitry. As a result, the function of distributing the short-circuit current to other switching elements is lost, leading to the problem of the entire device being destroyed.

[0007] Furthermore, the technology disclosed in Patent Document 2 differs from the subject matter of Patent Document 1 in that it tolerates short-circuit failure of switching elements, and even if a short circuit occurs, the explosion-proof structure attempts to contain the damage within the semiconductor module, but this depends on the extent of the failure. Here, too, the number of switching elements mounted on the small semiconductor module is four in each case, so even if a short circuit occurs, the possibility of failure is small. However, if the number of switching elements increases, a larger short-circuit current will flow in proportion to the number of switching elements, and the amount of heat generated in the switching element will increase in proportion to the square of the current strength, so even if explosion-proof treatment is applied, there is a risk of destroying the semiconductor module itself. As a result, the function of the explosion-proof structure to protect other semiconductor modules from that semiconductor module is lost, leading to the problem of the destruction of the entire device.

[0008] This disclosure was made to solve the above-mentioned problems and aims to provide a power module that can suppress short-circuit failure of the entire device even when the number of switching elements increases.

[0009] The power module according to this disclosure is a power module equipped with a plurality of switching elements arranged in parallel with each other in a current path and a control circuit for turning each of the plurality of switching elements on or off, and comprises a plurality of submodules configured by grouping the plurality of switching elements into groups of multiples, and a short-circuit detector arranged in the current path for detecting when a short circuit occurs in any of the submodules, and is characterized in that when the short-circuit detector detects a short circuit, an on command is issued to the switching elements of a submodule different from the submodule in which the short circuit occurred within a predetermined on command issuance time.

[0010] According to this disclosure, by providing multiple submodules, each containing a group of switching elements, and configuring the system so that when a short circuit is detected in one submodule, an ON command is issued to the switching elements of the other submodules within a predetermined ON command issuance time, it is possible to obtain a power module that can suppress short-circuit failure of the entire device even when the number of switching elements increases.

[0011] This is a block diagram showing the circuit configuration of a power module according to Embodiment 1. This is a cross-section of a submodule according to Embodiment 1 to which an explosion-proof structure has been applied. This is a waveform diagram showing the short-circuit current flowing through a short-circuited switching element. This is a diagram showing the highest temperature rise of the short-circuited switching element and the metal in contact with the switching element. This is a waveform diagram showing the short-circuit current when the switching element of a normal submodule is turned on after 1 / 4 cycle of the short-circuit current. This is a diagram showing the highest temperature rise of the short-circuited switching element and the metal in contact with the switching element when the switching element of a normal submodule is turned on after 1 / 4 cycle of the short-circuit current. This is a block diagram showing the circuit configuration of a power module according to Embodiment 2. This is a block diagram showing the system configuration of a power converter according to Embodiment 3.

[0012] This embodiment will be described with reference to the drawings. In each drawing, the same reference numerals indicate the same or corresponding parts. Figures 1 to 8 relate to one embodiment and the present disclosure is not limited by these drawings.

[0013] Embodiment 1. Figure 1 is a block diagram showing the circuit configuration of a power module according to Embodiment 1. In Figure 1, the power module 100 comprises submodules 10, 11, and 12, each composed of 12 switching elements arranged in parallel with each other in a current path and grouped into sets of four switching elements 1, 2, 3, and 4; a short-circuit detector 20 located in the current path that detects when a short circuit occurs in any of the submodules 10 to 12; a control circuit 30 including a gate drive unit that turns on or off the switching elements 1 to 4 of each submodule 10 to 12; and a signal path 40 that transmits on commands from the control circuit 30 to the switching elements 1 to 4. Here, the number of switching elements is set to 12, and submodules 10 to 12 grouped into sets of four switching elements 1 to 4 are shown as an example. However, the number is not limited to this, and in the case of a power module 100 that handles high voltage and high current, the number of switching elements mounted increases to several tens or more, so various combinations of grouping are possible.

[0014] For the sake of explanation, submodule 10 is assumed to be a short-circuited submodule containing the switching element 1 that has experienced a short circuit, while submodules 11 and 12 are assumed to be normal submodules in which no short circuits have occurred in switching elements 1 to 4. Furthermore, known switching elements 1 to 4 include IGBTs (Insulated Gate Bipolar Transistors) made of silicon, MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), and elements made of SiC or GaN. The short-circuit detector 20 may utilize magnetic field measuring elements such as Hall elements or TMR (Tunneling Magneto Resistance) elements, search coils for magnetic field measurement using Rogowski coils, current shunts, or CTs (Current Transformers).

[0015] Furthermore, if the number of switching elements exceeds several dozen, providing a short-circuit detector 20 for each switching element would not only complicate the circuit configuration but also cause a delay in the time it takes for the control circuit 30 to turn on the switching elements. Therefore, in the power module 100 shown in Figure 1, only one short-circuit detector 20 is placed on the input side 50 of the current path, in the current path 51 before it is branched in parallel to the multiple submodules 10 to 12, or only one on the output side 52 of the current path, in the current path 53 after the parallel branching of the multiple submodules 10 to 12 has been integrated. This configuration simplifies the circuit configuration of the short-circuit detector 20, enabling faster detection of short-circuit current and on-commands to the switching elements. When the short-circuit detector 20 detects that a short circuit has occurred in any of the submodules 10 to 12, it will issue on-commands to the switching elements 1 to 4 of all submodules 10 to 12, including the short-circuited submodule 10.

[0016] Alternatively, instead of providing a short-circuit detector 20 for each switching element, it is also possible to place a short-circuit detector 20 in each submodule 10 to 12, thereby reducing the complexity of the circuit configuration while relatively speeding up the detection of short-circuit current and the on-command to the switching elements. For example, if a short-circuit detector 20 is placed in the current path of submodule 10, it will identify that a short circuit has occurred in submodule 10 and issue on-commands to the switching elements 1 to 4 of the normal submodules 11 and 12, which are different from submodule 10. However, in order to speed up the detection of short-circuit current and the on-command to the switching elements, it is desirable to minimize the number of short-circuit detectors 20.

[0017] According to the power module 100 of Embodiment 1, by providing multiple submodules 10 to 12, each containing multiple switching elements in groups, and by configuring the system to quickly issue ON commands to at least the switching elements 1 to 4 of the normal submodules 11 and 12 when a short circuit occurs in any of the submodules 10 to 12, for example, if a short circuit occurs in submodule 10, then a power module capable of suppressing short-circuit failure of the entire device can be obtained even if the number of switching elements increases. In other words, even if the short-circuit current concentrates on the short-circuited switching element 1, the short-circuit current immediately after the short circuit is relatively small, and the amount of heat generated only in that submodule 10 is also small. Therefore, by grouping into multiple submodules, the impact from submodule 10 immediately after the short circuit on the normal submodules 11 and 12, as well as the peripheral circuits such as the control circuit 30 and signal path 40, is limited, and the short-circuit current can be distributed before a large current flows.

[0018] Furthermore, in order to further limit the impact of a short-circuited submodule 10, it is also effective to apply explosion-proof treatment by covering the area around submodules 10 to 12 with a mechanically or thermally strong ceramic, metal, or the like. Figure 2 shows a cross-section of a submodule according to Embodiment 1 to which an explosion-proof structure has been applied. In Figure 2, the switching elements 1 and 2 and the switching elements 3 and 4 (not shown) hidden behind them are stacked on a base substrate 5, separated by explosion-proof walls 6 for each submodule 10 to 12, and pressed against electrodes 8 via contacts 7 with built-in springs. The entire structure is covered with an insulating cover 9 and mechanically fixed to the substrate 5. With this configuration, if a switching element 1 of submodule 10 is short-circuited, even if the short-circuited submodule 10 is destroyed, the explosion-proof structure allows for a more limited impact on the outside.

[0019] As mentioned above, in the case of a power module 100 that handles high voltage and high current, the number of switching elements increases to several tens or more. Therefore, compared to the case with only a few elements, several tens to 100 times more heat will be generated in the short-circuited submodule 10. However, if multiple switching elements are grouped into multiple submodules of several elements each, and each submodule is treated with explosion-proofing, the other submodules 11 and 12, as well as the peripheral circuit's control circuit 30 and signal path 40, will remain normal until the short-circuited submodule 10 is destroyed. In this case, the short-circuit current can be distributed until then. If a short circuit occurs in submodule 10, there is a possibility that malfunctions will also occur in the peripheral circuit and the switching elements 1 to 4 of the other submodules 11 and 12. However, if even some of them can be turned on, the heat generated in the short-circuited submodule 10 can be distributed and reduced. Also, immediately after a short circuit, some switching elements in the short-circuited submodule 10 may still be surviving. Therefore, when a short circuit is detected, it is effective to quickly issue an ON command from the control circuit 30 to all switching elements 1 to 4 of submodules 10 to 12.

[0020] Next, coupled analysis of electromagnetic field analysis and temperature analysis is used to determine the on-command issuance time required from the start of a short circuit until a normal switching element is turned on. Figure 3 is a waveform diagram showing the short-circuit current flowing through the short-circuited switching element, and Figure 4 is a diagram showing the highest temperature rise of the short-circuited switching element and the metal in contact with the switching element. As a premise for the numerical analysis, a power module handling high voltage and high current is assumed, and 30 switching elements are grouped into three submodules of 10 each. The waveform diagrams in Figures 3 and 4 show the current value and temperature normalized to their peak values, and each shows the time dependence.

[0021] Here, the switching element is, for example, a silicon IGBT, and metals with a coefficient of thermal expansion relatively close to that of silicon, such as molybdenum, are placed in the upper and lower layers of the chip. This reduces mechanical stress due to temperature changes and improves the reliability of the chip. Furthermore, copper, which is used for busbars, is placed outside the molybdenum. In addition to molybdenum, other metals or multiple metals may also be placed. In this configuration, Figure 4 shows the temperature dependence of molybdenum, which is placed in the upper and lower layers of the chip, among the short-circuited switching element and the metal in contact with the switching element. As the temperature rises, the resistance of the silicon element decreases, but the resistance of the metal in contact with the switching element increases, so generally, the metal in contact with the switching element reaches the highest temperature.

[0022] From the analysis results in Figures 3 and 4, it can be seen that before the waveform of the short-circuit current reaches one cycle from the time of the short circuit, the temperature of either the short-circuited switching element or the metal in contact with the switching element exceeds 1, which corresponds to the melting point, causing it to melt. When the melting point is exceeded, an arc is generated, and because the arc is hot, it further melts and vaporizes the metal in contact with the switching element, and the expansion force of vaporization destroys the structure inside the short-circuited submodule. Furthermore, according to the analysis results in Figures 3 and 4, after the short circuit occurs, the temperature rises sharply from around 3 / 4 of the time when the waveform of the short-circuit current has passed, the resistance value of the metal in contact with the short-circuited switching element increases rapidly, and the calculation of the short-circuit current stops midway.

[0023] In other words, while it is desirable to issue an ON command to a normal switching element as quickly as possible after detecting a short-circuit current, if the system is configured to issue an ON command to at least the other switching elements within the shortest time between the occurrence of the short-circuit and the melting point of the material constituting the short-circuited switching element or any part of the metal in contact with the switching element, then even if the inside of the short-circuited submodule is destroyed, its explosion-proof function is likely to remain effective, and the surrounding circuits and other normal submodules are likely to maintain a normal state. According to the power module 100 of Embodiment 1, if a plurality of submodules 10 to 12 are provided, each containing a plurality of switching elements, and for example, when a short-circuited submodule 10 is detected, the system is configured to issue an ON command to the switching elements 1 to 4 of the other submodules 11 and 12 within a predetermined ON command issuance time, that is, within the shortest time between the occurrence of the short-circuited switching element 1 or any part of the metal in contact with the switching element 1 and the melting point of the material constituting the short-circuited switching element, then a power module capable of suppressing short-circuit destruction of the entire device can be obtained even if the number of switching elements increases.

[0024] Furthermore, we will explain the analysis results of issuing ON commands to normal switching elements at a predetermined ON command issuance time. Figure 5 is a waveform diagram showing the short-circuit current when the switching elements of a normal submodule are turned on after 1 / 4 cycle of the short-circuit current, and Figure 6 is a diagram showing the highest temperature rise of the short-circuited switching element and the metal in contact with the switching element when the switching elements of a normal submodule are turned on after 1 / 4 cycle of the short-circuit current. The waveform diagrams in Figures 5 and 6 also show time dependence, but the difference from the waveform diagrams in Figures 3 and 4 is that all the switching elements of the normal submodule were turned on near 1 / 4 cycle of the short-circuit current after the short circuit occurred. For the analysis, it was assumed that all the switching elements of the short-circuited submodule were destroyed and were not turned on.

[0025] From the analysis results in Figures 5 and 6, it can be seen that if the system is configured to issue an ON command to a normal switching element before the short-circuit current waveform reaches 1 / 4 of a cycle from the time of the short circuit, the short-circuited submodule will not reach its melting point, and its temperature will only rise to about half of its melting point. Furthermore, the temperature rise peaks around the third cycle of the short-circuit current and gradually decreases. In the analysis in Figure 3, the resistance of the metal in contact with the switching element increased rapidly, causing the calculation of the short-circuit current to stop midway, but in the analysis in Figure 5, the calculation does not stop midway, and the short-circuit current is gradually reduced by a finite resistance component. Based on the electromagnetic field analysis and temperature analysis so far, if the system is configured to detect the short-circuit current in the initial period after a short circuit occurs, that is, within a predetermined ON command issuance time, and to issue an ON command to the switching element of a normal submodule, it may be effective in suppressing short-circuit failure even in submodules that have not been treated with explosion-proofing.

[0026] In the analysis of Figures 5 and 6, the switching elements of the submodule were configured to turn on near 1 / 4 of the short-circuit current cycle. However, if the melting point at which arc generation begins is considered the limit of temperature rise, then if the short-circuit current is 1 / 2 of a cycle (double the 1 / 4 cycle), twice the energy will be supplied, and the maximum temperature of the metal in contact with the switching elements will be approximately at the melting point. In other words, if the system is configured to issue an ON command to a normal switching element before the short-circuit current waveform reaches 1 / 2 of a cycle, the temperature rise can be kept below the melting point. Note that the ON command issuance time required to turn on a normal switching element varies depending on the power module configuration and operating conditions. For example, if the total number of switching elements, the number of submodules grouped together, and the busbars connected to the capacitors when the power module is used as a power converter, the predetermined ON command issuance time will also differ.

[0027] Therefore, according to the power module 100 of Embodiment 1, if the predetermined ON command issuance time is set to allow for twice the time margin of the 1 / 2 period, and if the short-circuit current contains an AC component, the time is set to one period of the lowest-order AC component, an energy dispersion effect can be obtained, and short-circuit failure can be avoided. Next, the time it takes for the waveform of the short-circuit current to reach one period (reciprocal of the frequency) from the time of the short circuit is evaluated. When the power module is used in a power converter, if the capacitance of the capacitor is C and the inductance of the system such as the busbar is L, the angular frequency of the current value is ω = √(1 / (LC)). The relationship between frequency f and angular frequency is ω = 2πf, so the time of one period can be calculated from the reciprocal of frequency f, 1 / f. In other words, with respect to the power module 100 of Embodiment 1, the circuit can be designed so that the timing of turning on the switching element in advance falls within the predetermined ON command issuance time, without having to conduct short-circuit failure experiments. For example, as mentioned above, by simplifying the circuit configuration by placing only one short-circuit detector 20 in either the current path 51 or the current path 53, it becomes possible to detect short-circuit currents and speed up the ON command to the switching element.

[0028] Embodiment 2. Embodiment 2 will be described focusing on the parts that differ from Embodiment 1. Figure 7 is a block diagram showing the circuit configuration of the power module according to Embodiment 2. The power module 101 is further equipped with a signal strength converter 60 and a signal path 70 that directly transmits the ON command from the signal strength converter 60 to the switching elements 1 to 4 in order to further speed up the ON of the switching elements. Generally, the output voltage of the short circuit detector 20 is different from the drive voltage that turns on the switching elements 1 to 4. Therefore, when the output voltage of the short circuit detector 20 exceeds a certain threshold, it is converted to a drive voltage that turns on the switching elements. If this signal strength converter 60 is configured using analog circuits such as a resistor voltage divider and an operational amplifier, without using a digital circuit that requires A / D conversion, the switching elements 1 to 4 can be turned on at high speed with almost no processing time delay.

[0029] According to the power module 101 of the second embodiment, a signal strength converter 60 and a signal path 70 are added, and the signal path 70 from the signal strength converter 60 to the submodules 10 to 12 is provided independently of the signal path 40 from the control circuit 30 to the switching elements 1 to 4 of the submodules 10 to 12. As a result, the signal processing time required by the control circuit 30 can be omitted, and the ON command for a normal switching element from the detection of a short circuit current can be further accelerated. By combining the additional installation of the signal strength converter 60 with the placement of one short circuit detector 20, it becomes possible to more effectively shorten the predetermined ON command issuance time.

[0030] Embodiment 3. Embodiment 3 applies the power modules according to Embodiments 1 and 2 described above to a power converter. This disclosure is not limited to a specific power converter, but the case in which it is applied to a three-phase inverter device will be described. Figure 8 is a block diagram showing the system configuration of a power converter according to Embodiment 3. In Figure 8, the power conversion system includes a DC power supply 200, a power converter 300, and a load 400. The DC power supply 200 supplies DC power to the power converter 300 and is composed of a DC grid, solar cells, a storage battery, etc., but may also be composed of a rectifier circuit connected to an AC grid, an AC / DC converter device, etc. Alternatively, the DC power supply 200 can be composed of a DC / DC converter device that converts the DC power output from the DC grid into a predetermined power.

[0031] The power converter 300 is a three-phase inverter device connected between the DC power supply 200 and the load 400, and converts the DC power supplied from the DC power supply 200 into AC power and supplies it to the load 400. The power converter 300 includes a main conversion circuit 301 that converts DC power into AC power and outputs it, and a main control circuit 302 that controls the power conversion of the main conversion circuit 301. The load 400 is a three-phase motor driven by AC power supplied from the power converter 300, and is not limited to any particular application. For example, it is used as a motor mounted on various electrical equipment, such as in hybrid cars, electric cars, railway vehicles, elevators, and air conditioning equipment. The main conversion circuit 301 includes a capacitor (not shown) connected between the electrodes of the DC power supply 200, and a plurality of submodules connected in parallel with the capacitor, each of which is connected in series with the current path of the capacitor, and comprises a plurality of power modules 303, 304, and the outputs from the plurality of power modules 303, 304 are connected to the load 400.

[0032] Here, multiple power modules 303 and 304 are provided, but they may be integrated into a single package to form a single power module. In the three-phase inverter device, when a charge is applied to a capacitor to which a DC power supply 200 is applied, and each of the multiple switching elements configured in the submodule is turned on, current flows from the capacitor to the switching elements, and the voltage across these switching elements becomes almost zero, equivalent to a short circuit. On the other hand, when each of the multiple switching elements configured in the submodule is turned off, no current flows from the capacitor, and a voltage is generated across these switching elements. In this way, the power converter 300 converts external DC power into AC power and outputs it to the load 400 by repeatedly turning on and off the multiple switching elements configured in the submodule.

[0033] In this case, if all switching elements are turned on simultaneously, the current is distributed to all switching elements, resulting in less heat generation in the switching elements. On the other hand, when parallel switching elements are in the off state, a short circuit occurs in one switching element, causing it to turn on and forming a current path. In this case, all the current concentrates in the short-circuited switching element, resulting in a large current flow. However, the power modules 303 and 304 are configured to detect a short circuit in a submodule and issue an on command to the switching elements of other submodules within a predetermined on command issuance time, thereby suppressing short-circuit failure of the entire device. As described above, the power converter 300 according to Embodiment 3 is configured with power modules 303 and 304 that can suppress short-circuit failure, similar to Embodiments 1 and 2, thus realizing a highly reliable power converter. Although examples of applying the power modules according to Embodiments 1 and 2 to a three-phase inverter device have been described, they can also be applied to devices that have the function of turning large currents on or off, such as semiconductor circuit breakers and semiconductor transformers.

[0034] Furthermore, when applying high-current power modules to high-voltage converter / inverter devices, even more power modules are arranged in series. This configuration makes it possible to increase the voltage across the converter / inverter device. In this operation, more power modules are initially installed than the number of power modules that will be used. If a short-circuit failure occurs in a power module, after recovery from the short-circuit failure, the switching elements of the surviving, functioning sub-modules of the power module that experienced the short-circuit failure will remain constantly on. Although it is not possible to turn these switching elements on and off, because more power modules than the number required are initially installed, the current can be turned on or off using the other functioning power modules that did not experience the short-circuit failure, allowing the device to function as a high-voltage converter / inverter.

[0035] Furthermore, if all the switching elements in a power module are destroyed and all turn off, it becomes impossible to conduct any current. In other words, because many power modules are arranged in series, if current cannot be conducted, it becomes impossible to use it as a high-voltage converter / inverter device. Therefore, when using many power modules arranged in series, even if the destruction of a short-circuited submodule is tolerable, it is important that the other submodules that are not short-circuited remain in a normal state, that is, in a state where they can be turned on.

[0036] While this disclosure describes various exemplary embodiments and examples, the various features, aspects, and functions described in one or more embodiments are not limited to the application of a particular embodiment, but are applicable individually or in various combinations to the embodiments. Accordingly, countless variations not illustrated are envisioned within the scope of the art disclosed in this specification. For example, these include modifying, adding or omitting at least one component, or even extracting at least one component and combining it with a component from another embodiment.

[0037] 1, 2, 3, 4: Switching elements, 5: Substrate, 6: Explosion-proof wall, 7: Contact, 8: Electrode, 9: Cover, 10, 11, 12: Submodule, 20: Short-circuit detector, 30: Control circuit, 40, 70: Signal path, 50: Input side of current path, 51, 53: Current path, 52: Output side of current path, 60: Signal strength converter, 100, 101, 303, 304: Power module, 200: DC power supply, 300: Power converter, 301: Main conversion circuit, 302: Main control circuit, 400: Load.

Claims

1. A power module equipped with a plurality of switching elements arranged in parallel with each other in an electric current path, and a control circuit for turning each of the plurality of switching elements on or off, comprising a plurality of submodules formed by grouping the plurality of switching elements into groups of multiples, and a short-circuit detector arranged in the electric current path for detecting when a short circuit occurs in any of the submodules, wherein when the short-circuit detector detects a short circuit, an on command is issued to the switching elements of a submodule different from the submodule in which the short circuit occurred, within a predetermined on command issuance time.

2. The power module according to claim 1, characterized in that the ON command issuance time is the shortest time from the time the short circuit occurs until the temperature of either the switching element of the submodule where the short circuit occurred or the metal in contact with the switching element reaches the melting point of the material constituting the part.

3. The power module according to claim 1 or 2, characterized in that, if the short-circuit current flowing through the switching element of the submodule where the short circuit occurred includes an AC component, the ON command issuance time is one period of the lowest-order AC component among the AC components.

4. The power module according to claim 3, characterized in that the ON command issuance time is half the period of the lowest-order AC component.

5. The power module according to any one of claims 1 to 4, characterized in that at least one short-circuit detector is provided for each of the multiple submodules on the input side or output side of the current path.

6. The power module according to claim 5, characterized in that one short-circuit detector is placed on the input side of the current path before it is branched in parallel to the plurality of submodules, or one short-circuit detector is placed on the output side of the current path after it has been integrated from the parallel branching of the plurality of submodules.

7. The power module according to claim 6, characterized in that when the short-circuit detector detects a short circuit, an ON command is issued to the switching elements of all the submodules, including the submodule where the short circuit occurred.

8. The power module according to any one of claims 1 to 7, comprising a signal strength converter that generates the ON command based on a detection signal from the short-circuit detector, wherein the signal path from the signal strength converter to the submodule is provided independently of the signal path from the control circuit to the switching element.

9. The power module according to any one of claims 1 to 8, characterized in that the plurality of submodules are configured with an explosion-proof structure.

10. A power conversion device comprising a power module according to any one of claims 1 to 9, a main conversion circuit that converts and outputs power input from an external source, and a main control circuit that controls the power conversion of the main conversion circuit.

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