Inverter and control method for an inverter

Abstract

An inverter is specified that includes two switching elements of an inverter circuit connected in series, control devices configured to control each switching element, and protection circuits configured to transmit an output signal from the control device to each of the switching elements via a first resistive element. The protection circuit includes a second resistive element arranged to be electrically connected in parallel with the first resistive element, and a switch configured to toggle between a first state in which the second resistive element is electrically connected in parallel with the first resistive element, and a second state in which the connection is broken.The protection circuit is configured to determine whether a short-circuit current has been generated in a first pattern or a second pattern, and to switch the switch to the first state in the case where it is determined that the short-circuit current of the second pattern has been generated.

Description

Background1. Area

[0001] The present disclosure relates to an inverter and a control method for the inverter. 2. Description of the state of the art

[0002] Japanese Patent Laid-Open No. JP 2019-88084 A discloses an inverter including upper and lower arm switching elements, a soft-cut-off resistor element, and a soft-cut-off switching element. Each switching element has a control terminal and is turned on when a voltage is applied to the control terminal. The soft-cut-off resistor element is connected to the control terminal of the switching element via the soft-cut-off switching element. When a short-circuit fault occurs in one of the upper and lower arm switching elements, the other switching element needs to be protected. Hereinafter, a switching element in which a short-circuit fault occurs is referred to as a short-circuit element, and a switching element that needs to be protected is referred to as a protected element.In the inverter disclosed in the above-described publication, when a short-circuit fault occurs, the soft-shutdown resistance element can be connected to the control terminal of the protected element by turning on the soft-shutdown switching element. This allows the protected element to be protected by reducing the voltage applied to the control terminal.

[0003] The generation pattern of the short-circuit current flowing through the protected element can be classified into two types depending on whether the protected element is off or on at a time when the short-circuit fault occurs in the short-circuit element. One is a generation pattern in a case where the protected element is off at a time when a short-circuit fault occurs in the short-circuit element. In this case, when the protected element is turned on in a state where a short-circuit fault has occurred, the short-circuit current flowing through the protected element gradually increases. The other (the other generation pattern) is a generation pattern in a case where the protected element is on at a time when a short-circuit fault occurs in the short-circuit element.In this case, when a short-circuit fault occurs in the short-circuit element, the short-circuit current flowing through the protected element increases rapidly. The switching element must be properly protected according to the generation pattern of the short-circuit current flowing through the protected element.

[0004] US 10 917 081 B1 discloses a gate driver circuit, wherein a device controls a high-power drive device external to a gate driver circuit package. A first circuit charges a control node over a first period of time in response to a first signal through the first node indicating the absence of a fault condition and a first level of a control signal. A second circuit discharges the control node over a second period of time in response to a second signal through the second node indicating the absence of the fault condition and a second level of a control signal. A third circuit includes a current amplifier and is configured as a soft shutdown path to discharge the control node over a third period of time in response to the first signal through the first node indicating the presence of the fault condition.The third time period is different from the second time period. Summary

[0005] This summary is provided to introduce, in simplified form, a selection of concepts that are described more fully below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to assist in determining the scope of the claimed subject matter.

[0006] An inverter according to one embodiment of the present disclosure includes two switching elements of an inverter circuit, the two switching elements being connected in series with each other, drive devices configured to respectively drive the switching elements, and protection circuits each having a first resistance element. The protection circuit is configured to transmit an output signal of the drive device to each of the switching elements via the first resistance element. One of the two switching elements in which a short-circuit fault occurs is a short-circuit element, and the other of the two switching elements is a protected element.A generation pattern of a short-circuit current flowing through the protected element includes a first pattern in which a short-circuit current flows through the protected element in a case where the protected element is turned on in a state where a short-circuit fault has occurred in the short-circuit element, and a second pattern in which a short-circuit current flows through the protected element in a case where a short-circuit fault occurs in the short-circuit element in a state where the protected element is on.The protection circuit comprises a second resistance element arranged to be electrically connectable in parallel with the first resistance element, and a switch configured to switch between a first state in which an electrical parallel connection of the second resistance element and the first resistance element is enabled, and a second state in which the electrical parallel connection of the second resistance element and the first resistance element is canceled. The protection circuit is further configured to determine whether a short-circuit current of the first pattern or a short-circuit current of the second pattern has been generated, and to switch the switch to the first state if it is determined that the short-circuit current of the second pattern has been generated.

[0007] An inverter according to another embodiment of the present disclosure includes two switching elements of an inverter circuit, the two switching elements being connected in series with each other, drive devices configured to drive the switching elements, respectively, and protection circuits each having a first resistance element. The protection circuit is configured to transmit an output signal of the drive device to each of the switching elements via the first resistance element. One of the two switching elements in which a short-circuit fault occurs is a short-circuit element, and the other of the two switching elements is a protected element.A generation pattern of a short-circuit current flowing through the protected element includes a first pattern in which a short-circuit current flows through the protected element in a case where the protected element is turned on in a state where a short-circuit fault has occurred in the short-circuit element, and a second pattern in which a short-circuit current flows through the protected element in a case where a short-circuit fault occurs in the short-circuit element in a state where the protected element is on.The protection circuit comprises a second resistance element arranged to be electrically connectable in parallel with the first resistance element, and a switch configured to switch between a first state in which an electrical parallel connection of the second resistance element and the first resistance element is enabled, and a second state in which the electrical parallel connection of the second resistance element and the first resistance element is canceled. The protection circuit is further configured to determine whether a short-circuit current of the second pattern has been generated, and to switch the switch to the first state if it is determined that the short-circuit current of the second pattern has been generated.

[0008] According to a further aspect of the present disclosure, a control method for an inverter is provided. The inverter includes two switching elements of an inverter circuit, the two switching elements being connected in series with each other, drive devices configured to respectively drive the switching elements, and protection circuits each having a first resistance element. The protection circuit is configured to transmit an output signal of the drive device to each of the switching elements via the first resistance element. One of the two switching elements in which a short-circuit fault occurs is a short-circuit element, and the other of the two switching elements is a protected element.A generation pattern of a short-circuit current flowing through the protected element includes a first pattern in which a short-circuit current flows through the protected element in a case where the protected element is turned on in a state where a short-circuit fault has occurred in the short-circuit element, and a second pattern in which a short-circuit current flows through the protected element in a case where a short-circuit fault occurs in the short-circuit element in a state where the protected element is on.The protection circuit includes a second resistance element arranged to be electrically connectable in parallel with the first resistance element, and a switch configured to switch between a first state in which an electrical parallel connection of the second resistance element and the first resistance element is enabled, and a second state in which the electrical parallel connection of the second resistance element and the first resistance element is canceled. The control method includes: determining whether a short-circuit current of the second pattern has been generated, and switching the switch to the first state if it is determined that the short-circuit current of the second pattern has been generated.

[0009] Other features and embodiments will become apparent from the following detailed description, drawings and claims. Short description of the drawings Fig. 1 is a schematic diagram illustrating the configuration of a motor driving device. Fig. Fig. 2 is a schematic diagram illustrating the configuration of a driving device and a protection circuit used in an inverter control device of the type shown in Fig. 1 shown motor drive device. Fig. Figure 3 shows a graph illustrating a relationship between time and current flowing through the protected element when a short-circuit fault occurs in the short-circuit element used in the inverter circuit of the device shown in Fig. 1 shown motor drive device.

[0010] Throughout the drawings and detailed description, the same reference numerals refer to the same elements. The drawings may not be to scale, and the relative size, proportions, and representation of elements in the drawings may be exaggerated for clarity, illustration, and simplicity. Detailed description

[0011] This description provides a comprehensive understanding of the methods, devices, and / or systems described. Modifications and equivalents of the methods, devices, and / or systems described will be apparent to those skilled in the art. Sequences of operations are exemplary and may be changed as apparent to those skilled in the art, except for operations that necessarily occur in a certain order. Descriptions of functions and structures commonly known to those skilled in the art may be omitted.

[0012] Example embodiments may take various forms and are not limited to the described examples. However, the described examples are comprehensive and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0013] In this description, “at least one of A and B” should be understood to mean “only A, only B, or both A and B”.

[0014] An example of an inverter is described below.

[0015] With reference to Fig. 1, a motor drive device 10 is used to drive a motor 11. The motor 11 is a three-phase AC motor with three-phase coils U, V, and W. The motor 11 can be mounted on any device. For example, the motor 11 is mounted on a motor-driven compressor, an industrial vehicle, or a passenger vehicle. Motor drive device

[0016] The motor drive device 10 includes a battery BA, a smoothing capacitor C, and an inverter INV. The inverter INV includes an inverter circuit 20 and an inverter control device 12.

[0017] The inverter circuit 20 has legs connected in parallel. Each leg has two switching elements connected in series. In the example shown in the drawing, the inverter circuit 20 has six switching elements Q1, Q2, Q3, Q4, Q5, and Q6, and six diodes D1, D2, D3, D4, D5, and D6. The switching elements Q1 to Q6 are, for example, insulated gate bipolar transistors (IGBTs) or metal-oxide-semiconductor field-effect transistors (MOSFETs). The switching elements Q1 to Q6 each have a first terminal T1, a second terminal T2, a control terminal T3, and a sense terminal T4. If the switching elements Q1 to Q6 are IGBTs, the first terminals T1 are collectors, the second terminals T2 are emitters, and the control terminals T3 are gates.If the switching elements Q1 to Q6 are MOSFETs, the first terminals T1 are drains, the second terminals T2 are sources, and the control terminals T3 are gates.

[0018] The switching elements Q1 and Q2 of the U-phase leg are connected in series. The switching elements Q3 and Q4 of the V-phase leg are connected in series. The switching elements Q5 and Q6 of the W-phase leg are connected in series. The switching elements Q1, Q3, and Q5 are contained in the upper branch of the corresponding leg. The switching elements Q2, Q4, and Q6 are contained in the lower branch of the corresponding leg. The diodes Q1 to Q6 are each connected in parallel with the switching elements D1 to D6.

[0019] Battery BA is connected to switching elements Q1 to Q6 via smoothing capacitor C. Inverter circuit 20 converts DC power input from battery BA into AC power and outputs the AC power to motor 11. This drives rotor 11. The rated voltage of battery BA is, for example, 800 V.

[0020] A connection point between the switching elements Q1 and Q2 is connected to a coil U. A connection point between the switching elements Q3 and Q4 is connected to a coil V. A connection point between the switching elements Q5 and Q6 is connected to a coil W.

[0021] The inverter control device 12 has a control device 13, control devices (drivers) 21 and protection circuits 30.

[0022] The controller 13 outputs a control signal to the drive device 21. The controller 13 includes a processor and a memory. The processor is, for example, a central processing unit (CPU), a graphics processing unit (GPU), or a digital signal processor (DSP). The memory includes random access memory (RAM) and read-only memory (ROM). The memory stores program code or instructions configured to cause the processor to execute processes. The memory or a computer-readable medium includes any type of media accessible by general-purpose computers or special-purpose computers. The controller 13 may include a hardware circuit such as an application-specific integrated circuit (ASIC) or a field-programmable gate array (FPGA).The control device 13, which is a processing circuit, may comprise one or more processors running according to a computer program, one or more hardware circuits (e.g., ASICs or FPGAs), or a combination thereof.

[0023] Each drive device 21 is individually arranged for a corresponding one of the switching elements Q1 to Q6. The hardware configuration of the drive device 21 can be the same as that of the control device 13, for example. In response to a control signal from the control device 13, the drive device 21 performs a switching operation on the one of the switching elements Q1 to Q6 corresponding to the drive device 21.

[0024] As it is in Fig. 2, the control device 21 has a short-circuit detection terminal 22 and a protection terminal 23. protective circuit

[0025] Each protection circuit 30 is individually arranged for a corresponding one of the switching elements Q1 to Q6. The hardware configuration of the protection circuit 30 can, for example, be the same as that of the control device 13. The protection circuit 30 protects the one of the switching elements Q1 to Q6 that corresponds to the protection circuit 30. The protection circuit 30 is located between the control device 21 and the corresponding one of the switching elements Q1 to Q6. The protection circuit 30 includes a first resistance element R1, a second resistance element R2, and a switching circuit 31. The switching circuit 31 includes a shunt resistance element 32, a determination unit 33, a latch circuit 34, a switch 35, and a threshold detection circuit 36.

[0026] The first resistance element R1 connects the control terminal T3 to the protection terminal 23. The first resistance element R1 is connected in series between the control terminal T3 and the protection terminal 23. The control device 21 sends an output signal to the one of the switching elements Q1 to Q6 corresponding to the control device 21 via the first resistance element R1.

[0027] The second resistance element R2 is arranged so that it can be electrically connected (connected) in parallel with the first switching element R1, or is arranged such that it can be connected in parallel with the first switching element R1. The resistance value [Ω] of the second resistance element R2 can be the same as or different from that of the first resistance element R1.

[0028] The shunt resistance element 32 is connected to the detection terminal T4. A small current proportional to the current flowing between the first and second terminals T1 and T2 flows through the detection terminal T4. A voltage drop corresponding to the current flowing between the first and second terminals T1 and T2 occurs in the shunt resistance element 32. The short-circuit detection terminal 22 of the driver 21 is connected to a connection point between the shunt resistance element 32 and the detection terminal T4.

[0029] Based on the magnitude of the voltage drop across the shunt resistance element 32, the driver 21 determines whether the current flowing through one of the switching elements Q1 to Q6 corresponding to the driver 21 is greater than or equal to a short-circuit detection threshold. The short-circuit detection threshold is predetermined. The short-circuit detection threshold is set to be higher than a value in a normal use current range. The current flowing through the switching elements Q1 to Q6 refers to the current flowing between the first terminals T1 and the second terminals T2 of the switching elements Q1 to Q6.When the current flowing through one of the switching elements Q1 to Q6 corresponding to the driver 21 is equal to or greater than the short-circuit detection threshold, the driver 21 determines that a short-circuit fault has occurred in the one of the switching elements Q1 to Q6 connected in series with the corresponding one of the switching elements Q1 to Q6. For example, when detecting that the current flowing through the switching element Q2 is equal to or greater than the short-circuit detection threshold, the driver 21 determines that a short-circuit fault has occurred in the switching element Q1 corresponding to the switching element Q2.

[0030] The one of the switching elements Q1 to Q6 in which a short-circuit fault occurs is called a short-circuit element, and the one of the switching elements Q1 to Q6 connected in series with the short-circuit elements is called a protected element. The determination unit 33 is used to determine the type (kind) of generation pattern of a short-circuit current flowing through the protected element when a short-circuit fault occurs in the short-circuit element. The hardware configuration of the determination unit 33 may be, for example, the same as that of the controller 13. In a first pattern, a short-circuit current flows through the protected element when the protected element is turned on in a state where a short-circuit fault has occurred in the short-circuit element.In a second pattern, a short-circuit current flows through the protected element when a short-circuit fault occurs in the short-circuit element in a state where the protected element is on. The short-circuit current of the first pattern is generated when the switching element Q1 to Q6 of one of the upper and lower arms is turned on in a state where a short-circuit current has occurred in the switching elements Q1 to Q6 of the other arm. The short-circuit current of the second pattern is generated when a short-circuit occurs in the switching elements Q1 to Q6 of one of the upper and lower arms in a state where the switching elements Q1 to Q6 of the other arm are on.

[0031] Fig. 3 shows a case where a short-circuit fault occurs in the short-circuit element at time T11. As indicated by a line L1, in the first pattern, when the protected element is turned on in a state where a short-circuit fault has occurred in the short-circuit element, the short-circuit current flowing through the protected element gradually increases. As indicated by a line L2, in the second pattern, when a short-circuit fault occurs in the short-circuit element when the short-circuit element is on, a short circuit occurs in the leg including the short-circuit element. As a result, the short-circuit current flowing through the protected element increases rapidly.

[0032] As it is in Fig. 2, the determination unit 33 is connected to a connection point between the detection terminal T4 and the shunt resistance element 32. Based on a voltage drop amount in the shunt resistance element 32, the determination unit 33 determines whether an increase amount per unit time in the current flowing through the switching elements Q1 to Q6 is greater than or equal to a first threshold and less than a second threshold. Based on the voltage drop amount in the shunt resistance element 32, the determination unit 33 determines whether the increase amount per unit time in the current flowing through the switching elements Q1 to Q6 is equal to or greater than the second threshold. The increase amount per unit time in the current flowing through the switching elements Q1 to Q6 is represented by an inclination (slope) of current in a case where the vertical axis represents current and the horizontal axis represents time.

[0033] The first threshold is set to determine whether the short-circuit current of the first pattern has been generated. When the short-circuit current of the first pattern is generated, the increase amount per unit time in the current flowing through the protected element is larger than in a case where no short-circuit fault has occurred in the short-circuit element. This allows the determination unit 33 to determine that the short-circuit current of the first pattern has been generated by setting the first threshold to be higher than the increase amount per unit time in the current flowing through the protected element when no short-circuit fault has occurred.Specifically, when the increase amount per unit time in the current flowing through the switching elements Q1 to Q6 is equal to or greater than the first threshold and less than the second threshold, the determination unit 33 determines that the short-circuit current of the first pattern has been generated, that is, that the short-circuit current of the first pattern has flowed through the protected element.

[0034] The second threshold is greater than the first threshold. The second threshold is set to determine whether the short-circuit current of the second pattern has been generated. The increase in the current per unit time is greater when the short-circuit current of the second pattern is generated than when the short-circuit current of the first pattern is generated. This allows the determination unit 33 to determine that the short-circuit current of the second pattern has been generated by setting the second threshold to be higher than the increase in the current per unit time when the short-circuit current of the first pattern is generated. When the increase in the current per unit time flowing through the switching elements Q1 to Q6 is equal to or greater than the second threshold, the determination unit 33 determines that the short-circuit current of the second pattern has been generated, i.e.that the short-circuit current of the second pattern has flowed through the protected element. When the short-circuit current of the second pattern is generated, the determination unit 33 turns on the switch 35. For example, when the short-circuit current of the second pattern flows through the protected element, the determination unit 33 turns on the switch 35 by outputting a high-level signal to the latch circuit 34.

[0035] When the switch 35 is turned on by the determination unit 33, the latch circuit 34 holds the switch 35.

[0036] The switch 35 is connected in series with the second resistance element R2. The switch 35 and the second resistance element R2 are connected in parallel with the first resistance element R1. When the switch 35 is on, the second resistance element R2 is electrically connected in parallel with the first resistance element R1. When the switch 35 is off, the electrical parallel connection of the second resistance element R2 and the first resistance element R1 is canceled. The switch 35 is a switching element such as a transistor. The switch 35 is configured to switch between a first state in which the electrical parallel connection of the second resistance element R2 and the first resistance element R1 is enabled, and a second state in which the electrical parallel connection of the second resistance element R2 and the first resistance element R1 is canceled.

[0037] The threshold detection circuit 36 ​​is connected to a connection point between the detection terminal P4 and the shunt resistance element 32. The threshold detection circuit 36 ​​is connected between the detection terminal T4 and the shunt resistance element 32. Based on the voltage drop across the shunt resistance element 32, the threshold detection circuit 36 ​​determines whether the current flowing through the switching elements Q1 to Q6 is less than a current threshold. The hardware configuration of the threshold detection circuit can be the same as that of the controller 13, for example. When the current flowing through the switching elements Q1 to Q6 becomes less than the current threshold, the threshold detection circuit 36 ​​turns off the switch 35 by controlling the latch circuit 34. The current threshold is predetermined. Operation according to the present embodiment

[0038] The operation of the protection circuit 30 is described below using an example in which a short-circuit fault has occurred in the switching element Q1 of the upper branch among the switching elements Q1 and Q2. In a case where a short-circuit fault has occurred in the switching element Q2 of the lower branch, the protection circuit 30 operates in the same manner. The protection circuits 30 in the switching elements Q3, Q4, Q5, and Q6 function in the same manner.

[0039] When the short-circuit current of the first pattern is generated, the determination unit 33 does not turn on the switch 35. Thus, of the first resistance element R1 and the second resistance element R2, only the first resistance element R1 is electrically connected to the control terminal T3 of the switching element Q2.

[0040] When the current flowing through the switching element Q2 is equal to or greater than the short-circuit detection threshold, the driver 21 turns off the switching element 21 by reducing the voltage applied to the control terminal T3. The voltage applied to the control terminal T3 is reduced by the charge stored in the control terminal T3 flowing to the protection terminal 23. When the short-circuit current of the first pattern is generated, the charge of the control terminal T3 flows to the protection terminal 23 via the first resistance element R1. As shown in Fig. As shown in Figure 3, when the voltage applied to the control terminal T3 begins to decrease at time T2, the current flowing through the switching element Q2 decreases as the switching element Q2 approaches an off state. When the switching element Q2 is turned off, the switching element Q2 is protected from overcurrent.

[0041] When the short-circuit current of the second pattern is generated, the determination unit 33 turns on the switch 35. This electrically connects the control terminal T3 of the switching element Q2 to the first resistance element R1 and the second resistance element R2, which are electrically connected (connected) in parallel with each other.

[0042] When the current flowing through the switching element Q2 is equal to or greater than the short-circuit detection threshold, the driver 21 turns off the switching element Q2 by reducing the voltage applied to the control terminal T3. When the short-circuit current of the second pattern is generated, the charge of the control terminal T3 flows to the protection terminal 23 via the first resistance element R1 and the second resistance element R2. The combined resistance of the first resistance element R1 and the second resistance element R2 is smaller than the resistance of the first resistance element R1. Thus, the voltage applied to the control terminal T3 can be reduced more easily than if only the first resistance element R1 were connected to the control terminal T3.

[0043] When the short-circuit current of the second pattern is generated and the voltage applied to the control terminal T3 begins to decrease at time T12, the voltage applied to the control terminal T3 decreases for a short period of time. This causes the switching element Q2 to be abruptly turned off. If the switching element Q2 is abruptly turned off, the switching element Q2 may be damaged by shock. For this reason, when the current flowing through the switching element Q2 becomes less than the current threshold, the threshold detection circuit 36 ​​turns off the switch 35. Since only the first resistance element R1 is electrically connected to the control terminal T3, the voltage applied to the control terminal T3 is less likely to decrease. That is, the charge of the control terminal T3 is less likely to flow to the protection terminal 23.This prevents the switching element Q2 from turning off abruptly. The current threshold is set so that the switching element Q2 is not damaged by a shock. Advantages of the present embodiment (1) When a short-circuit fault occurs, the protection circuit 30 lowers the voltage applied to the control terminal T3 to turn off the corresponding one of the switching elements Q1 to Q6. Thus, the protection circuit 30 protects the corresponding one of the switching elements Q1 to Q6. The resistance value of the combined resistor in which the first resistance element R1 and the second resistance element R2 are electrically connected in parallel is lower than the resistance value of the first resistance element R1 alone. As the resistance value of the resistance element connected to the control terminal T3 decreases, the voltage applied to the control terminal T3 can be more easily reduced.By switching whether to allow the electrical parallel connection of the second resistance element R2 and the first resistance element R1 according to the generation pattern of the short-circuit element, the corresponding one of the switching elements Q1 to Q6 is protected according to the generation pattern of the short-circuit current. (2) The determination unit 33 determines that the short-circuit current of the second pattern has been generated when the increase amount per unit time in the current flowing through the corresponding one of the switching elements Q1 to Q6 is equal to or greater than the second threshold. This allows the determination unit 33 to correctly determine that the short-circuit current of the second pattern has been generated, and thus enables the second resistance element R2 to be electrically connected in parallel with the first resistance element R1. (3) The threshold detection circuit 36 ​​switches the switch 35 to the second state to enter a state where the second resistance element R2 is not electrically connected in parallel with the first resistance element R1 when the current flowing through the corresponding one of the switching elements Q1 to Q6 is less than the current threshold. Thus, when the short-circuit current of the second pattern is generated, the switching element Q2 is prevented from being abruptly turned off. This prevents damage to the switching element Q2 due to a surge (voltage surge, current surge, overvoltage). (4) According to the present embodiment, it is determined whether the short-circuit current generation pattern is the first pattern or the second pattern. Thus, the switching elements Q1 to Q6 are protected according to the short-circuit current generation pattern using a different method. Specifically, when the short-circuit current generation pattern is the first pattern, only the first resistance element R1 is used to reduce the voltage applied to the control terminal T3. When the short-circuit current generation pattern is the second pattern, the voltage applied to the control terminal T3 is reduced using the first resistance element R1 and the second resistance element R2.

[0044] Regardless of whether the short-circuit current generation pattern is the first pattern or the second pattern, the switching elements Q1 to Q6 could be protected using the same method. For example, regardless of whether the short-circuit current generation pattern is the first pattern or the second pattern, the corresponding one of the switching elements Q1 to Q6 could be turned off using only the first resistance element R1. In this case, protecting the corresponding one of the switching elements Q1 to Q6 against the short-circuit current of the second pattern requires a reduction of the short-circuit detection threshold. In this case, even in the normal use current region, it could be determined that a short-circuit current is flowing through the protected element. Thus, it could be determined that a short-circuit current is being generated even when no short-circuit current is being generated.Furthermore, if the switching elements Q1 to Q6 are also protected from the short-circuit current of the first pattern using a method suitable for the short-circuit current of the second pattern, the switching elements Q1 to Q6 may be damaged by the short-circuit current of the first pattern. Thus, regardless of whether the short-circuit current generation pattern is the first pattern or the second pattern, it is difficult to protect the switching elements Q1 to Q6 using the same method. According to the present embodiment, the switching elements Q1 to Q6 are protected using a different method according to the explanation pattern of the short-circuit current flowing through the protected element. Thus, the switching elements Q1 to Q6 are correctly protected according to the short-circuit current generation pattern. Modifications

[0045] The present embodiment may be modified as described below. The present embodiment and the following modifications may be combined as long as the combined modifications remain technically consistent with each other.

[0046] The switching circuit 31 does not need to include the threshold detection circuit 36. In this case, when the generation pattern of the short-circuit current flowing through the protected element is the second pattern, the switch 35 does not need to be switched to the second state according to the current flowing through the corresponding one of the switching elements Q1 to Q6 to enter a state in which the second resistance element R2 is not electrically connected in parallel with the first resistance element R1.

[0047] The switching circuit 31 can be incorporated (contained) in the control device 21.

[0048] The first resistance element R1 may comprise multiple resistance elements. Similarly, the second resistance element R2 may comprise multiple resistance elements.

[0049] The determination unit 33 only needs to be able to determine whether the short-circuit current generation pattern is the second pattern, and it does not need to be able to determine whether the short-circuit current generation pattern is the first pattern. For example, the determination unit 33 determines that the short-circuit current generation pattern is the second pattern when the increase amount per unit time in the current flowing through the corresponding one of the switching elements Q1 to Q6 is equal to or greater than the second threshold. The determination unit 33 does not need to determine whether the increase amount per unit time in the current flowing through the corresponding one of the switching elements Q1 to Q6 is equal to or greater than the first threshold. When the short-circuit current of the second pattern is generated, the determination unit 33 turns on the switch 35.When the short-circuit current generation pattern is the second pattern, the determination unit 33 turns on the switch 35. Thus, the same advantage as that according to the embodiment is obtained even if it is not determined whether the short-circuit current generation pattern is the first pattern.

[0050] An inverter is specified that comprises two switching elements of an inverter circuit that are connected in series with one another, control devices that are configured to respectively control switching elements, and protection circuits that are each configured to transmit an output signal of the control device to each of the switching elements via a first resistance element. The protection circuit comprises a second resistance element that is arranged to be electrically connected in parallel with the first resistance element, and a switch that is configured to switch between a first state in which an electrical parallel connection of the second resistance element with the first resistance element is enabled, and a second state in which the connection is canceled.The protection circuit is configured to determine whether a short-circuit current has been generated in a first pattern or a second pattern, and to switch the switch to the first state in the case where it is determined that the short-circuit current of the second pattern has been generated.

Claims

[1] Inverter (Inv) with: two switching elements of an inverter circuit (20), wherein the two switching elements (Q1 to Q6) are connected in series with each other, Control devices (21) configured to respectively control the switching elements (Q1 to Q6), and Protection circuits (30) each having a first resistance element (R1), wherein the protection circuit (30) is configured to transmit an output signal of the control device (21) to each of the switching elements (Q1 to Q6) via the first resistance element (R1), wherein one of the two switching elements (Q1 to Q6) in which a short-circuit fault occurs is a short-circuit element and the other of the two switching elements (Q1 to Q6) is a protected element, a generation pattern of a short-circuit current flowing through the protected element: a first pattern in which a short-circuit current flows through the protected element in a case where the protected element is turned on in a state in which a short-circuit fault has occurred in the short-circuit element, and a second pattern in which a short-circuit current flows through the protected element in a case where a short-circuit fault occurs in the short-circuit element in a state in which the protected element is on, wherein the protective circuit (30) comprises: a second resistance element (R2) arranged to be electrically connected in parallel to the first resistance element (R1), and a switch (35) configured to switch between a first state in which an electrical parallel connection of the second resistance element (L2) and the first resistance element (R1) is enabled, and a second state in which the electrical parallel connection of the second resistance element (R2) and the first resistance element (R1) is canceled, and the protective circuit (30) is still configured, to determine whether a short-circuit current of the first pattern or a short-circuit current of the second pattern has been generated, and switching the switch (35) to the first state in case of determining that the short-circuit current of the second pattern has been generated. [2] Inverter (Inv) according to claim 1, wherein the protection circuit (30) is configured in a case where an increase amount per unit time in the current flowing through the switching elements (Q1 to Q6) is equal to or greater than a first threshold and less than a second threshold, to determine that the short-circuit current of the first pattern has been generated, the second threshold being greater than the first threshold, and in a case where the increase amount per unit time in the current flowing through the switching elements (Q1 to Q6) is equal to or greater than the second threshold value, to determine that the short-circuit current of the second pattern has been generated. [3] The inverter (Inv) according to claim 1 or 2, wherein the protection circuit (30) is configured to switch the switch (35) to the second state in a case where the current flowing through the switching elements (Q1 to Q6) is less than a current threshold. [4] The inverter (Inv) according to any one of claims 1 to 3, wherein the protection circuit (30) is configured to switch the switch (35) to the second state in a case where it is determined that the short-circuit current of the first pattern has been generated. [5] Inverter (Inv) with: two switching elements (Q1 to Q6) of an inverter circuit (20), wherein the two switching elements (Q1 to Q6) are connected in series with each other, Control devices (21) configured to respectively control the switching elements (Q1 to Q6), and Protection circuits (30) each having a first resistance element (R1), wherein the protection circuit (30) is configured to transmit an output signal of the control device (21) to each of the switching elements (Q1 to Q6) via the first resistance element (R1), wherein one of the two switching elements (Q1 to Q6) in which a short-circuit fault occurs is a short-circuit element and the other of the two switching elements (Q1 to Q6) is a protected element, a generation pattern of a short-circuit current flowing through the protected element: a first pattern in which a short-circuit current flows through the protected element in a case where the protected element is turned on in a state in which a short-circuit fault has occurred in the short-circuit element, and a second pattern in which a short-circuit current flows through the protected element in a case where a short-circuit fault occurs in the short-circuit element in a state in which the protected element is on, wherein the protective circuit (30) comprises: a second resistance element (R2) arranged to be electrically connected in parallel to the first resistance element (R1), and a switch (35) configured to switch between a first state in which an electrical parallel connection of the second resistance element (L2) and the first resistance element (R1) is enabled, and a second state in which the electrical parallel connection of the second resistance element (R2) and the first resistance element (R1) is canceled, and the protective circuit (30) is still configured, to determine whether a short-circuit current of the second pattern has been generated, and switching the switch (35) to the first state in case of determining that the short-circuit current of the second pattern has been generated. [6] Control method for an inverter (Inv), wherein the inverter (Inv) comprises: two switching elements of an inverter circuit (20), wherein the two switching elements (Q1 to Q6) are connected in series with each other, Control devices (21) configured to respectively control the switching elements (Q1 to Q6), and Protection circuits (30) each having a first resistance element (R1), wherein the protection circuit (30) is configured to transmit an output signal of the control device (21) to each of the switching elements (Q1 to Q6) via the first resistance element (R1), wherein one of the two switching elements (Q1 to Q6) in which a short-circuit fault occurs is a short-circuit element and the other of the two switching elements (Q1 to Q6) is a protected element, a generation pattern of a short-circuit current flowing through the protected element: a first pattern in which a short-circuit current flows through the protected element in a case where the protected element is turned on in a state in which a short-circuit fault has occurred in the short-circuit element, and a second pattern in which a short-circuit current flows through the protected element in a case where a short-circuit fault occurs in the short-circuit element in a state in which the protected element is on, wherein the protective circuit (30) comprises: a second resistance element (R2) arranged to be electrically connected in parallel to the first resistance element (R1), and a switch (35) configured to switch between a first state in which an electrical parallel connection of the second resistance element (L2) and the first resistance element (R1) is enabled, and a second state in which the electrical parallel connection of the second resistance element (R2) and the first resistance element (R1) is canceled, and the control procedure has: Determining whether a short-circuit current of the second pattern has been generated, and Switching the switch (35) to the first state in the case that it is determined that the short-circuit current of the second pattern has been generated.

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