JP2019030081A - Power conversion apparatus and failure diagnosis method - Google Patents

Abstract

To provide a power conversion apparatus capable of discovering at least which fails among a plurality of switching elements connected with each other in parallel in a switching circuit in which the plurality of switching elements are connected in parallel, and a failure diagnosis method.SOLUTION: A power conversion apparatus includes a switching circuit 21 in which a plurality of switching elements 21a and 21b are connected in parallel, being provided with: an inverter circuit 2 for converting DC power to AC power; a voltage sensor for detecting an inter-terminal voltage V1 of a switching circuit 21; a drive unit 51 capable of inputting an ON signal for making the respective switching elements 21a and 21b an ON state to the respective plurality of switching elements 21a and 21b; and a diagnosis unit 52 for diagnosing open-circuit failure of at least one of the plurality of switching elements 21a and 21b in a case where the inter-terminal voltage V1 is equal to or larger than an open determination threshold value when the ON signal is input into the respective plurality of switching elements 21a and 21b.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a power conversion device including a switching circuit in which a plurality of switching elements are connected in parallel, and a failure diagnosis method.

  In a power conversion device that converts input power into predetermined output power, a plurality of switching elements are used. As an example of such a power conversion device, an inverter device that converts DC power into AC power is known. Patent Document 1 discloses a conventional inverter device.

  FIG. 7 is a diagram illustrating an example of a conventional inverter device. The conventional inverter device includes an inverter circuit 2 'and a control circuit 5'. The conventional inverter device converts the DC power input from the DC power source 1 into AC power and supplies it to the load L. As shown in FIG. 7, the inverter circuit 2 ′ has a plurality of switching circuits 21 ′ to 24 ′, and these are connected by a full bridge. In each of the switching circuits 21 ′ to 24 ′, two switching elements are connected in parallel. The control circuit 5 ′ generates a signal for switching between the on state and the off state of each switching element, and inputs this signal to the gate terminal of each switching element.

  In the conventional inverter device configured as described above, the control circuit 5 ′ alternately performs switching operations of the switching elements in the switching circuits 21 ′ and 24 ′ and the switching elements in the switching circuits 22 ′ and 23 ′. As a result, the inverter circuit 2 'converts the DC power into AC power.

JP 2013-55781 A

  As shown in FIG. 7, two switching elements are connected in parallel in each of the switching circuits 21 ′ to 24 ′. For this reason, the current flowing through each of the switching circuits 21 ′ to 24 ′ is divided into two switching elements that constitute the switching circuits 21 ′ to 24 ′. However, for example, in one of the switching circuits 21 ′ to 24 ′, when one switching element has an open failure and the other switching element has not failed, all currents input to the switching circuit are failed. It flows to the switching element that is not. For this reason, in the inverter circuit 2 ′, even if one of the switching elements fails to open, conversion from DC power to AC power is performed. Therefore, the user may not be aware that the switching element has an open failure. However, since one switching element has an open failure, the other switching element is burdened. If the use is continued in this state, the switching element that has not failed also fails, causing damage to other components. Such a problem is not limited to a case where a plurality of switching circuits are connected by a full bridge.

  Accordingly, the present invention has been created in view of the above problems, and its object is to provide at least one of a plurality of switching elements connected in parallel to each other in a switching circuit in which a plurality of switching elements are connected in parallel. It is an object of the present invention to provide a power conversion device and a failure diagnosis method that can detect that a failure occurs.

  The power conversion device provided by the first aspect of the present invention includes a switching circuit in which a plurality of switching elements are connected in parallel to each other, and converts a power input from a power source into a predetermined output power. Voltage detecting means for detecting a voltage between terminals of the switching circuit; signal input means capable of inputting an on signal for turning on each switching element to each of the plurality of switching elements; and the plurality of switching elements Diagnostic means for diagnosing that at least one of the plurality of switching elements has an open failure when the voltage between the terminals when the ON signal is input to each of the elements is equal to or higher than an open determination threshold; It is characterized by providing. According to this configuration, by comparing the voltage between the terminals when the ON signal is input to each of the plurality of switching elements and a predetermined open determination threshold, at least one of the plurality of switching elements is It is possible to diagnose whether an open failure has occurred. Therefore, it can be found that at least one of the plurality of switching elements connected in parallel with each other has an open failure.

  In a preferred embodiment of the power conversion device, the diagnostic means includes the plurality of the plurality of switching elements when the voltage between the terminals when the ON signal is not input to each of the plurality of switching elements is equal to or less than a short circuit determination threshold. The switching element is diagnosed as having a short circuit failure. According to this configuration, any of the plurality of switching elements is short-circuited by comparing the voltage between the terminals when the ON signal is not input to each of the plurality of switching elements and a predetermined short-circuit determination threshold value. You can diagnose whether or not. Therefore, it is possible to discover that any of the plurality of switching elements connected in parallel to each other has an open fault, and it is also possible to discover that a short circuit has occurred.

  In a preferred embodiment of the power conversion device, the power source is a direct current power source, and the main circuit is connected to the high potential side switching terminal connected to the high potential side output terminal of the direct current power source. A first arm and a second arm connected in series to a low potential side switching circuit connected to a low potential side output terminal of the DC power supply, the first arm and the second arm, Is an inverter circuit connected in parallel. According to this configuration, the main circuit is a full bridge type inverter circuit, and a failure of a plurality of switching elements in the inverter circuit can be diagnosed.

  In a preferred embodiment of the power conversion device, the voltage detecting means includes a first terminal voltage in the high potential side switching circuit of the first arm and a switching circuit on the low potential side of the second arm. A voltage between the plurality of switching elements in the switching circuit on the high potential side of the first arm and the low potential side of the second arm. The ON signal is input to the plurality of switching elements in the switching circuit, and the switching elements in the low potential side switching circuit of the first arm and the high potential side of the second arm When the ON signal is not input to the plurality of switching elements in the switching circuit, When a current is output from the inverter circuit, the first inter-terminal voltage and the second inter-terminal voltage are compared, and if they are different, the switching circuit on the high potential side of the first arm Or any one of the plurality of switching elements in the switching circuit on the low potential side of the second arm is diagnosed as having an open failure. According to this configuration, by comparing the first inter-terminal voltage and the second inter-terminal voltage, any one of the plurality of switching elements in the high-potential side switching circuit of the first arm, or the It can be found that any of the plurality of switching elements in the switching circuit on the low potential side of the second arm has an open failure.

  In a preferred embodiment of the power conversion device, the diagnostic means is configured such that the signal input means has the plurality of switching elements in the high-potential side switching circuit of the first arm and the low potential of the second arm. The ON signal is input to the plurality of switching elements in the switching circuit on the side, and the high potential side of the plurality of switching elements and the second arm in the switching circuit on the low potential side of the first arm When the ON signal is not input to the plurality of switching elements in the switching circuit, and no current is output from the inverter circuit, the switching in the switching circuit on the high potential side of the first arm Both of the elements or the low potential side of the second arm Both of the plurality of switching elements in the switching circuit is diagnosed as open-circuit failure. According to this configuration, both of the plurality of switching elements in the switching circuit on the high potential side of the first arm or both of the plurality of switching elements in the switching circuit on the low potential side of the second arm are opened. You can discover that it is out of order.

  In a preferred embodiment of the power conversion device, the signal input means inputs the ON signal that causes the switching elements to operate in an active region. According to this configuration, when each of the switching elements is operated in an active region, at least one of the plurality of switching elements of the switching circuit has an open failure and a case where none has failed. Thus, the difference in the voltage between the terminals detected by the voltage detecting means increases. Therefore, misdiagnosis can be suppressed in the diagnosis of whether or not at least one of the plurality of switching elements connected in parallel to each other has an open failure.

  In a preferred embodiment of the power conversion device, the signal input means can input the ON signal only to any one of the plurality of switching elements in the switching circuit. According to this configuration, when the switching circuit is diagnosed as having an open failure or a short-circuit failure, the signal input means is provided only to any one of the switching elements in the switching circuit. An ON signal can be input, and the ON signal is not input to the remaining switching elements. Thereby, it can be specified which switching element of the plurality of switching elements in the switching circuit has an open fault or a short-circuit fault.

  A failure diagnosis method provided by the second aspect of the present invention includes a switching circuit in which a plurality of switching elements are connected in parallel to each other, and a failure of a main circuit that converts input power from a power source into predetermined output power A diagnostic method, comprising: inputting a turn-on signal for turning on each switching element to each of the plurality of switching elements; detecting a voltage between terminals of the switching circuit; A step of diagnosing that at least one of the plurality of switching elements has an open failure when the voltage between the terminals when the ON signal is input to each of the switching elements is equal to or higher than an open determination threshold; It is characterized by having. According to this configuration, by comparing the voltage between the terminals when the ON signal is input to each of the plurality of switching elements and a predetermined open determination threshold, at least one of the plurality of switching elements is It is possible to diagnose whether an open failure has occurred. Therefore, it can be found that at least one of the plurality of switching elements connected in parallel with each other has an open failure.

  According to the present invention, in a switching circuit in which a plurality of switching elements are connected in parallel, it can be found that at least one of the plurality of switching elements connected in parallel with each other has failed.

It is a figure showing the whole inverter device composition concerning one embodiment. It is a figure which shows the detailed structure of the inverter circuit and control circuit in the inverter apparatus shown in FIG. It is a figure which shows the collector-emitter saturation voltage characteristic in each switching element. It is a flowchart (the 1) of the failure diagnosis processing concerning one embodiment. It is a flowchart (the 2) of the failure diagnosis processing concerning one embodiment. It is a figure which shows an example of the switching circuit which concerns on a modification. It is a figure which shows the structure of the conventional inverter apparatus.

  Preferred embodiments of the present invention will be described below with reference to the drawings. The case where it uses for the inverter apparatus which converts direct-current power into alternating current power as a power converter device of this invention is demonstrated.

  FIG. 1 shows an example of the overall configuration of the inverter device. As shown in the figure, the inverter device includes an inverter circuit 2, a plurality of voltage sensors 31 to 34, a current sensor 41, and a control circuit 5. FIG. 2 shows an example of a detailed configuration of the inverter circuit 2 and the control circuit 5. The inverter device converts DC power input from the DC power source 1 into AC power and supplies the AC power to the load L. Inverter devices include, for example, motor drive control devices and lighting control devices such as light sources, induction heating devices that perform heating using electromagnetic induction, power conditioners, plasma generators, non-contact power supply devices, welding power supply devices, DC Used in various devices such as DC / DC converters. The usage form of the inverter device is not limited to the above. A combination of the inverter circuit 2 and the control circuit 5 corresponds to the “power converter” of the present invention.

  The DC power source 1 outputs DC power. For example, a rectifier circuit for rectifying an alternating current input from the power system and a smoothing capacitor for smoothing are provided. Note that the DC power source 1 is not limited to one that converts an alternating current into a direct current and outputs it, and may be any one that outputs a direct current (DC power). Examples of such a DC power source 1 include a fuel cell, a storage battery, and a solar cell. The DC power source 1 corresponds to the “power source” of the present invention.

  The inverter circuit 2 converts input power into predetermined output power. In the present embodiment, the inverter circuit 2 converts DC power from the DC power source 1 into AC power and outputs the AC power to the load L. The inverter circuit 2 corresponds to the “main circuit” of the present invention.

  The inverter circuit 2 includes four switching circuits 21 to 24, and these four switching circuits 21 to 24 are connected in a full bridge. That is, the inverter circuit 2 is a full bridge type inverter circuit. Specifically, the switching circuit 21 and the switching circuit 22 are connected in series between the connection line on the high potential side and the connection line on the low potential side of the DC power supply 1 to form a bridge structure. A bridge structure formed by the switching circuit 21 and the switching circuit 22 is referred to as an arm 20A. In the arm 20 </ b> A, the switching circuit 21 is connected to the output terminal on the high potential side of the DC power supply 1, and the switching circuit 22 is connected to the output terminal on the low potential side of the DC power supply 1. Further, the switching circuit 23 and the switching circuit 24 are connected in series between the connection line on the high potential side and the connection line on the low potential side of the DC power supply 1 to form a bridge structure. A bridge structure formed by the switching circuit 23 and the switching circuit 24 is referred to as an arm 20B. In the arm 20B, the switching circuit 23 is connected to the output terminal on the high potential side of the DC power supply 1, and the switching circuit 24 is connected to the output terminal on the low potential side of the DC power supply 1. The arm 20A and the arm 20B are connected in parallel as shown in FIG. When the arm 20A is the “first arm” of the present invention, the arm 20B corresponds to the “second arm” of the present invention, and when the arm 20B is the “first arm” of the present invention, the arm 20A is the “first arm” of the present invention. It corresponds to “second arm”.

  An output line is connected to a connection point a between the switching circuit 21 and the switching circuit 22 of the arm 20A, and an output line is also connected to a connection point b between the switching circuit 23 and the switching circuit 24 of the arm 20B. A load L is connected between these output lines.

  As shown in FIG. 2, the switching circuit 21 includes a pair of switching elements 21a and 21b connected in parallel to each other. In the present embodiment, the switching elements 21a and 21b are both IGBTs (Insulated Gate Bipolar Transistors). In both switching elements 21a and 21b, the collector terminal is connected to the high potential side of the DC power supply 1, and the emitter terminal is connected to the connection point a. In addition, the switching elements 21a and 21b have gate terminals connected to the control circuit 5, and are switched between an on state and an off state in accordance with signals (an on signal and an off signal described later) input from the control circuit 5. . When the switching elements 21a and 21b are both in the off state, the switching circuit 21 is cut off. In other cases, that is, when one or both of the switching elements 21a and 21b are in the on state, the switching circuit 21 is It becomes a conductive state.

  As shown in FIG. 2, the switching circuit 22 includes a pair of switching elements 22a and 22b connected in parallel to each other. In the present embodiment, the switching elements 22a and 22b are both IGBTs. In both switching elements 22 a and 22 b, the collector terminal is connected to the connection point a, and the emitter terminal is connected to the low potential side of the DC power supply 1. In addition, the switching elements 22a and 22b have gate terminals connected to the control circuit 5, and are switched between an on state and an off state in accordance with signals (an on signal and an off signal described later) input from the control circuit 5. . When the switching elements 22a and 22b are both in the off state, the switching circuit 22 is in the cut-off state. In other cases, that is, when one or both of the switching elements 22a and 22b are in the on state, It becomes a conductive state.

  As shown in FIG. 2, the switching circuit 23 includes a pair of switching elements 23a and 23b connected in parallel to each other. In the present embodiment, the switching elements 23a and 23b are both IGBTs. In both switching elements 23a and 23b, the collector terminal is connected to the high potential side of the DC power supply 1, and the emitter terminal is connected to the connection point b. In addition, both of the switching elements 23a and 23b have gate terminals connected to the control circuit 5, and are switched between an on state and an off state in accordance with signals (an on signal and an off signal described later) input from the control circuit 5. . When both of the switching elements 23a and 23b are in the off state, the switching circuit 23 is in the cut-off state. In other cases, that is, when one or both of the switching elements 23a and 23b are in the on state, It becomes a conductive state.

  As shown in FIG. 2, the switching circuit 24 includes a pair of switching elements 24a and 24b connected in parallel to each other. In the present embodiment, the switching elements 24a and 24b are both IGBTs. In both switching elements 24 a and 24 b, the collector terminal is connected to the connection point b, and the emitter terminal is connected to the low potential side of the DC power supply 1. The switching elements 24a and 24b have gate terminals connected to the control circuit 5, and switch between an on state and an off state in accordance with signals (an on signal and an off signal described later) input from the control circuit 5. . When both of the switching elements 24a and 24b are in the off state, the switching circuit 24 is in the cut-off state. In other cases, that is, when one or both of the switching elements 24a and 24b are in the on state, It becomes a conductive state.

  If each of the switching elements 21a to 24a and 21b to 24b operates normally, the on state and the off state are switched according to the input signals (on signal and off signal). However, if there is an open failure, it is always off, and if there is a short circuit failure, it is always on.

  In the present embodiment, a case where all the switching elements 21a to 24a and 21b to 24b are IGBTs will be described. However, the present invention is not limited to this, and other semiconductor switching elements may be used. Examples of such other semiconductor switching elements include MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) and bipolar transistors. Moreover, in this embodiment, as shown in FIG. 2, the flywheel diode is connected in antiparallel to each of the switching elements 21a to 24a and 21b to 24b. Further, a snubber capacitor or the like may be connected in parallel. In addition, a flywheel diode or a snubber capacitor may be connected to each of the switching circuits 21 to 24 instead of each of the switching elements 21a to 24a and 21b to 24b.

  Each voltage sensor 31-34 detects the voltage between the terminals of the switching circuits 21-24, respectively. The voltage sensors 31 to 34 output the detected voltages V1 to V4 between the switching circuits 21 to 24 to the control circuit 5, respectively.

  In this embodiment, although each voltage sensor 31-34 demonstrates the case where the voltage between terminals of the switching circuits 21-24 is detected, respectively, it is not limited to this. For example, the voltage sensor 31 may detect not the voltage between the terminals of the switching circuit 21 but the voltage between the collector and the emitter of one of the pair of switching elements 21a and 21b. Since the pair of switching elements 21a and 21b are connected in parallel to each other, the voltages applied to them have the same value. Further, it corresponds to the voltage between the terminals of the switching circuit 21. The same applies to the other voltage sensors 32-34. Therefore, even if the voltage sensor 31 (32 to 34) detects the collector-emitter voltage of one of the pair of switching elements 21a (22a to 24a) and 21b (22b to 24b), the switching circuit 21 (22 ˜24) is the same as detecting the inter-terminal voltage.

  The current sensor 41 detects the output current of the inverter circuit 2. The current sensor 41 outputs the detected output current Iout to the control circuit 5. The current sensor 41 may be provided on any terminal side of the load L.

  The control circuit 5 performs various controls of the inverter device. The control circuit 5 is realized by, for example, a microcomputer. In the present embodiment, the control circuit 5 mainly performs power conversion control and failure diagnosis processing. In the power conversion control, the control circuit 5 controls the output of the inverter circuit 2 so that the output of the inverter circuit 2 becomes a set value. In the failure diagnosis process, the control circuit 5 diagnoses whether the inverter circuit 2 is normal. As shown in FIG. 2, the control circuit 5 includes a drive unit 51 and a diagnosis unit 52 as functional blocks for performing failure diagnosis processing. In the present embodiment, the control circuit 5 performs both power conversion control and failure diagnosis processing. However, these controls may be performed as separate circuits.

  The drive unit 51 turns on each of the switching elements 21a to 24a and 21b to 24b to turn on (for example, a high level signal) and turn off to turn off (for example, a low level signal). Can be entered. In the present embodiment, there are two states, an on signal and an off signal, and the off signal is a signal in a state where no on signal is input. Moreover, since each switching element 21a-24a, 21b-24b is IGBT, an ON signal and an OFF signal are voltage signals.

  In the power conversion control, the driving unit 51 generates a pulse signal in which an ON signal and an OFF signal are alternately repeated, and inputs this to the switching elements 21a to 24a and 21b to 24b as a driving signal. Thereby, the ON state and the OFF state of the switching elements 21a to 24a and 21b to 24b are switched. And the conduction | electrical_connection state and interruption | blocking state of each switching circuit 21-24 switch. In this power conversion control, the drive unit 51 receives a pulse signal (drive signal) that is inverted by the switching elements 21a, 21b, 24a, and 24b and the switching elements 22a, 22b, 23a, and 23b, so that the inverter circuit 2. DC power is converted into AC power. In the power conversion control, the drive unit 51 generates an on signal and an off signal (drive signal) so that the switching elements 21a to 24a and 21b to 24b are switched between the saturation region and the cutoff region.

  In the failure diagnosis process, the drive unit 51 inputs an on signal to the switching elements 21a and 21b and the switching elements 24a and 24b, and inputs an off signal to the switching elements 22a and 22b and the switching elements 23a and 23b. To do. In the following description, the state in which the drive unit 51 inputs the on signal and the off signal in this way is referred to as a “first signal input state”. The drive unit 51 inputs an off signal to the switching elements 21a and 21b and the switching elements 24a and 24b, and inputs an on signal to the switching elements 22a and 22b and the switching elements 23a and 23b. In the following description, the state in which the drive unit 51 inputs the ON signal and the OFF signal in this way is referred to as a “second signal input state”. In the failure diagnosis process, the drive unit 51 generates an ON signal so that the switching elements 21a to 24a and 21b to 24b operate in the active region. That is, an on signal and an off signal are generated so that each switching element 21a to 24a and 21b to 24b is switched between the active region and the cutoff region. The drive unit 51 corresponds to the “signal input unit” of the present invention. It can be said that the drive unit 51 performs power conversion control by alternately repeating the first signal input state and the second signal input state at a predetermined interval.

  In the present embodiment, four signal lines 511 to 514 are connected to the drive unit 51 and branched. The signal line 511 is branched and then connected to the switching elements 21a and 21b. That is, the same signal is input to the switching elements 21a and 21b. Similarly, the signal line 512 is branched and then connected to the switching elements 22a and 22b. That is, the same signal is input to the switching elements 22a and 22b. The signal line 513 is branched and then connected to the switching elements 23a and 23b. That is, the same signal is input to the switching elements 23a and 23b. The signal line 514 is branched and then connected to the switching elements 24a and 24b. That is, the same signal is input to the switching elements 24a and 24b.

  The diagnosis unit 52 is based on detection values (voltages V1 to V4 between terminals) and detection values (output current Iout) of the current sensor 41 in the first signal input state and the second signal input state. Thus, it is diagnosed whether each of the switching circuits 21 to 24 is normal. Specifically, the diagnosis unit 52 determines whether at least one of the pair of switching elements 21a (22a to 24a) and 21b (22b to 24b) in the switching circuit 21 (22 to 24) has an open failure or a short circuit failure. Diagnose whether or not.

  In the present embodiment, the diagnosis unit 52 is in the first signal input state and when the current is output from the inverter circuit 2, the terminal voltage V1 (V4) and a preset open determination. The threshold value Vop is compared. Then, based on the comparison result, it is diagnosed whether one of the pair of switching elements 21a and 21b (24a and 24b) in the switching circuit 21 (24) has an open failure. Details of the opening determination threshold Vop will be described later. However, even if the current is output from the inverter circuit 2 when the diagnosis unit 52 is in the first signal input state, the direction of the current is assumed (from the connection point a through the load L to the connection point b If the flow is in the opposite direction, the diagnosis is as follows. That is, both of the pair of switching elements 21a and 21b in the switching circuit 21 have an open failure, and both of the pair of switching elements 24a and 24b in the switching circuit 24 have an open failure, and in the switching circuit 22 It is diagnosed that at least one of the pair of switching elements 22a and 22b has a short circuit failure and that at least one of the pair of switching elements 23a and 23b in the switching circuit 23 has a short circuit failure.

  The diagnosis unit 52 compares the inter-terminal voltage V2 (V3) when the current is output from the inverter circuit 2 with the second signal input state, and the open determination threshold value Vop. Then, based on the comparison result, it is diagnosed whether one of the pair of switching elements 22a and 22b (23a and 23b) in the switching circuit 22 (23) has an open failure. However, even if the current is output from the inverter circuit 2 when the diagnosis unit 52 is in the second signal input state, the direction of the current is assumed (from the connection point b through the load L to the connection point a If the flow is in the opposite direction, the diagnosis is as follows. That is, both of the pair of switching elements 22a and 22b in the switching circuit 22 have an open failure, and both of the pair of switching elements 23a and 23b in the switching circuit 23 have an open failure, and in the switching circuit 21 It is diagnosed that at least one of the pair of switching elements 21a and 21b has a short circuit failure and that at least one of the pair of switching elements 24a and 24b in the switching circuit 24 has a short circuit failure.

  Further, the diagnosis unit 52 calculates the inter-terminal voltage V2 (V3) when the first signal is input and no current is output from the inverter circuit 2, and the preset short-circuit determination threshold Vsht. Compare. Based on the comparison result, it is diagnosed whether at least one of the pair of switching elements 22a and 22b (23a and 23b) in the switching circuit 22 (23) is short-circuited. The details of the short circuit determination threshold value Vsht will be described later. When it is diagnosed that none of the switching elements 22a, 22b, 23a, and 23b has a short-circuit failure even though the first signal is input and no current is output from the inverter circuit 2. Diagnoses that both of the pair of switching elements 21a and 21b in the switching circuit 21 have an open failure, or that both of the pair of switching elements 24a and 24b in the switching circuit 24 have an open failure.

  The diagnosis unit 52 compares the inter-terminal voltage V1 (V4) when the second signal is input and no current is output from the inverter circuit 2 with the short-circuit determination threshold Vsht. Based on the comparison result, whether or not at least one of the pair of switching elements 21a and 21b (24a and 24b) in the switching circuit 21 (24) is short-circuited is diagnosed. When it is diagnosed that none of the switching elements 21a, 21b, 24a, and 24b has a short-circuit fault although the second signal is input and no current is output from the inverter circuit 2. Diagnoses that both of the pair of switching elements 22a and 22b in the switching circuit 22 have an open failure, or that both of the pair of switching elements 23a and 23b in the switching circuit 23 have an open failure.

  Next, the setting value of the open determination threshold value Vop will be described. In the present embodiment, the open determination threshold value Vop is set based on the collector-emitter saturation voltage characteristics of the switching elements 21a to 24a and 21b to 24b shown in FIG. In the present embodiment, it is assumed that the plurality of switching elements 21a to 24a and 21b to 24b all have the same collector-emitter saturation voltage characteristics. In FIG. 3, the horizontal axis represents the gate-emitter voltage, and the vertical axis represents the collector-emitter saturation voltage. Each of the switching elements 21a to 24a and 21b to 24b operates in the active region when the gate-emitter voltage is Va [V]. The collector-emitter saturation voltage characteristic shown in FIG. 3 is that the collector-emitter voltage is different between the switching elements 21a-24a and 21b-24b as long as the collector current Ic is different even if the gate-emitter voltage is the same. It is a characteristic that the saturation voltage changes.

  In the inverter apparatus shown in FIG. 1 and FIG. 2, it is assumed that the output current of the DC power supply 1 is Ia [A], and the drive unit 51 is in the first signal input state. At this time, in the switching circuit 21, when both of the pair of switching elements 21a and 21b are operating normally, both are turned on. That is, the switching circuit 21 becomes conductive. Further, the output current Ia [A] of the DC power supply 1 is input to the switching circuit 21 and is shunted to each of the switching elements 21a and 21b. Therefore, since the current of Ia / 2 [A] flows through each switching element 21a, 21b, these collector currents are Ia / 2 [A], respectively. Also, assuming that an ON signal is input to the gate terminals of the switching elements 21a and 21b so that the gate-emitter voltages of the switching elements 21a and 21b are both Va [V], as shown in FIG. The saturation voltage between the collector and emitter of each switching element 21a, 21b is Vx [V].

  However, for example, when the switching element 21a has an open failure and the switching element 21b is normal, no current flows through the switching element 21a, so that a current Ia [A] flows through the switching element 21b. That is, the collector current of the switching element 21a is 0 [A], and the collector current of the switching element 21b is Ia [A]. Therefore, if the ON signal is input to the gate terminals of the switching elements 21a and 21b so that the gate-emitter voltages of the switching elements 21a and 21b are both Va [V], as shown in FIG. The saturation voltage between the collector and the emitter of the switching element 21b is Vy [V]. As described above, since the voltage between the terminals of the switching circuit 21 is the same as the collector-emitter saturation voltage of the switching element 21b, the detection value of the voltage sensor 31 is Vy [V]. On the other hand, the same applies to the case where the switching element 21a is normal and the switching element 21b has an open failure. Therefore, when both the pair of switching elements 21a and 21b are normal, the voltage V1 between the terminals detected by the voltage sensor 31 is Vx [V], but one of the pair of switching elements 21a and 21b is an open failure. In this case, the inter-terminal voltage V1 rises to Vy [V].

  In the present embodiment, based on such a change, the open determination threshold Vop is set to a value that is larger than Vx [V] and less than or equal to Vy [V]. The diagnosis unit 52 diagnoses that at least one of the pair of switching elements 21a and 21b has an open failure when the detected inter-terminal voltage V1 is equal to or higher than the open determination threshold Vop. That is, in the present embodiment, it is diagnosed that at least one of the switching elements 21a and 21b has an open failure by utilizing the property that the collector-emitter saturation voltage varies depending on the collector current. In the above example, the switching circuit 21 has been described, but the same applies to the switching circuit 24. Moreover, although the case where the drive unit 51 is in the first signal input state has been described, the same applies to the case where the drive unit 51 is in the second signal input state. That is, the same can be said in the switching circuits 22 and 23 when the drive unit 51 is in the second signal input state.

  Next, the setting value of the short circuit determination threshold Vsht will be described.

  In the inverter apparatus shown in FIG. 1 and FIG. 2, it is assumed that the output current of the DC power supply 1 is Ia [A], and the drive unit 51 is in the first signal input state. At this time, if both of the pair of switching elements 22a and 22b are operating normally in the switching circuit 22, they are both turned off. That is, the switching circuit 22 is cut off and no current flows. Therefore, the power supply voltage of the DC power supply 1 is applied between the terminals of the switching circuit 22.

  However, for example, when the switching element 22a is short-circuited and the switching element 22b is normal, a current flows through the switching element 22a, so that the switching circuit 22 becomes conductive. As a result, the output current of the DC power supply 1 is not output to the load L and returns to the DC power supply 1 via the switching circuits 21 and 22. Therefore, the output current Iout of the inverter circuit 2 becomes zero. Further, since the switching circuit 22 is in a conductive state, the voltage V2 between the terminals of the switching circuit 22 is close to zero. The same applies to the case where the switching element 22a is normal and the switching element 22b is short-circuited. Therefore, when the switching elements 22a and 22b are both normal, the voltage V2 between the terminals detected by the voltage sensor 32 has the same value as the power supply voltage, but one of the pair of switching elements 22a and 22b is short-circuited. In this case, the output current Iout detected by the current sensor 41 becomes zero, and the inter-terminal voltage V2 decreases to zero [V].

  In the present embodiment, based on such a change, the short circuit determination threshold Vsht is set to a value that is greater than 0 [V] and less than the predetermined value Vs [V] shown below. The predetermined value Vs is, for example, the value of the collector-emitter saturation voltage (Vx [V]) when the switching elements 21a to 24a and 21b to 24b are normal, or the value of the power supply voltage. Then, the diagnosis unit 52 diagnoses that at least one of the pair of switching elements 22a and 22b has a short-circuit fault when the detected inter-terminal voltage V2 is equal to or less than the short-circuit determination threshold Vsht. In the above example, the switching circuit 22 has been described, but the same applies to the switching circuit 23. Moreover, although the case where the drive unit 51 is in the first signal input state has been described, the same applies to the case where the drive unit 51 is in the second signal input state. That is, the same can be said in the switching circuits 21 and 24 when the drive unit 51 is in the second signal input state.

  The diagnosis unit 52 compares the inter-terminal voltages V1 to V4 input from the voltage sensors 31 to 34 with the open determination threshold value Vop and the short circuit determination threshold value Vsht set as described above, whereby the switching circuits 21 to 24 are compared. It is diagnosed whether at least any one of the pair of switching elements 21a to 24a and 21b to 24b in FIG.

  Next, a failure diagnosis method in the inverter device according to this embodiment will be described.

  4 and 5 show an example of failure diagnosis processing performed by the control circuit 5. FIG. 4 and 5, the switching element is described as “SW”. The failure diagnosis processing is performed, for example, when an operation for starting diagnosis is input to the operation unit of the inverter device or when the inverter device is activated. Note that the timing at which the control circuit 5 performs the failure diagnosis process is not limited to the above. For example, it may be performed constantly while the inverter device is being driven (during power conversion control). Further, in the failure diagnosis process, the load L may be connected to the output line of the inverter circuit 2, or the load L may be short-circuited without being connected, or a diagnostic load may be connected.

  First, the control circuit 5 executes various processes according to the flow shown in FIG. Specifically, the drive unit 51 inputs an on signal to the switching elements 21a and 21b and the switching elements 24a and 24b, and inputs an off signal to the switching elements 22a and 22b and the switching elements 23a and 23b. (S101). That is, the drive unit 51 enters the first signal input state.

  Next, the diagnosis unit 52 determines whether or not a current is output from the inverter circuit 2 in spite of the first signal input state. Specifically, the diagnosis unit 52 determines whether or not the detection value (output current Iout) of the current sensor 41 is zero (S102). If it is determined in step S102 that no current is output from the inverter circuit 2 (the output current Iout is zero) (S102: YES), the diagnosis unit 52 determines that the voltage V2 between the terminals is a short circuit. It is determined whether or not it is equal to or less than a threshold value Vsht (S103).

  When it is determined in step S103 that the inter-terminal voltage V2 is equal to or lower than the short circuit determination threshold Vsht (S103: YES), the diagnosis unit 52 shorts at least one of the pair of switching elements 22a and 22b in the switching circuit 22. Diagnose that there is a failure (S104). On the other hand, when it is determined that the inter-terminal voltage V2 is not less than or equal to the short circuit determination threshold Vsht (S103: NO), the diagnosis unit 52 subsequently determines whether or not the inter-terminal voltage V3 is less than or equal to the short circuit determination threshold Vsht. (S105).

  When it is determined in step S105 that the inter-terminal voltage V3 is equal to or lower than the short circuit determination threshold Vsht (S105: YES), the diagnosis unit 52 shorts at least one of the pair of switching elements 23a and 23b in the switching circuit 23. Diagnose that there is a failure (S106). On the other hand, when it is determined that the inter-terminal voltage V3 is not equal to or less than the short-circuit determination threshold Vsht (S105: NO), the diagnosis unit 52 determines whether both of the pair of switching elements 21a and 21b in the switching circuit 21 or the switching circuit 24 It is diagnosed that both of the pair of switching elements 24a and 24b have an open failure (S107).

  On the other hand, when it is determined in step S102 that a current is being output from the inverter circuit 2 (the output current Iout is not zero) (S102: NO), the diagnosis unit 52 is subsequently output from the inverter circuit 2. It is determined whether or not the current flows in the direction opposite to the direction assumed in the first signal input state (the direction from the connection point a through the load L toward the connection point b). In the present embodiment, since the direction from the connection point a to the connection point b through the load L is the positive direction, it is determined whether or not the output current Iout is smaller than zero (S108).

  In step S108, when the current output from the inverter circuit 2 is flowing in the opposite direction (the output current Iout is smaller than zero) (S108: YES), the diagnosis unit 52 includes the pair of switching elements 21a in the switching circuit 21. , 21b both fail open, both the pair of switching elements 24a, 24b in the switching circuit 24 fail open, and at least one of the pair of switching elements 22a, 22b in the switching circuit 22 fails. In addition, it is diagnosed that at least one of the pair of switching elements 23a and 23b in the switching circuit 23 is short-circuited (S109). On the other hand, when the output current is flowing in the expected direction (the output current Iout is greater than zero) (S108: NO), the diagnosis unit 52 subsequently determines that the inter-terminal voltage V1 is equal to or greater than the open determination threshold Vop. It is determined whether or not (S110).

  When it is determined in step S110 that the inter-terminal voltage V1 is equal to or greater than the open determination threshold Vop (S110: YES), the diagnosis unit 52 determines that at least one of the pair of switching elements 21a and 21b in the switching circuit 21 is It is diagnosed that an open failure has occurred (S111). On the other hand, when it is determined that the inter-terminal voltage V1 is not equal to or higher than the open determination threshold Vop (S110: NO), the diagnosis unit 52 subsequently determines whether or not the inter-terminal voltage V4 is equal to or higher than the open determination threshold Vop. (S112).

  If it is determined in step S112 that the inter-terminal voltage V4 is greater than or equal to the open determination threshold Vop (S112: YES), the diagnosis unit 52 determines that at least one of the pair of switching elements 24a and 24b in the switching circuit 24 is It is diagnosed that an open failure has occurred (S113). On the other hand, when it is determined that the inter-terminal voltage V4 is not equal to or higher than the open determination threshold Vop (S112: NO), the diagnosis unit 52 determines that each of the switching circuits 21-24 when the drive unit 51 is in the first signal input state. Is diagnosed as operating normally (S114). That is, the pair of switching elements 21a and 21b in the switching circuit 21 and the pair of switching elements 24a and 24b in the switching circuit 24 have no open failure, and the pair of switching elements 22a and 22b in the switching circuit 22 and the pair of switching in the switching circuit 23 It is diagnosed that there is no short circuit failure in the elements 23a and 23b.

  Subsequently, the control circuit 5 executes various processes according to the flow shown in FIG. Specifically, the drive unit 51 inputs an off signal to the switching elements 21a and 21b and the switching elements 24a and 24b, and inputs an on signal to the switching elements 22a and 22b and the switching elements 23a and 23b. (S201). That is, the drive unit 51 enters the second signal input state.

  Next, the diagnosis unit 52 determines whether a current is not output from the inverter circuit 2 in spite of being in the second signal input state. Specifically, the diagnosis unit 52 determines whether or not the detection value (output current Iout) of the current sensor 41 is zero (S202). When it is determined in step S202 that no current is output from the inverter circuit 2 (the output current Iout is zero) (S202: YES), the diagnostic unit 52 determines that the voltage V1 between the terminals is a short circuit. It is determined whether or not it is equal to or less than a threshold value Vsht (S203).

  If it is determined in step S203 that the inter-terminal voltage V1 is equal to or less than the short circuit determination threshold Vsht (S203: YES), the diagnosis unit 52 shorts at least one of the pair of switching elements 21a and 21b in the switching circuit 21. Diagnose a failure (S204). Conversely, when it is determined that the inter-terminal voltage V1 is not less than or equal to the short circuit determination threshold Vsht (S203: NO), the diagnosis unit 52 subsequently determines whether or not the inter-terminal voltage V4 is less than or equal to the short circuit determination threshold Vsht. (S205).

  When it is determined in step S205 that the inter-terminal voltage V4 is equal to or lower than the short circuit determination threshold Vsht (S205: YES), the diagnosis unit 52 shorts at least one of the pair of switching elements 24a and 24b in the switching circuit 24. Diagnose that there is a failure (S206). On the other hand, when it is determined that the inter-terminal voltage V4 is not less than or equal to the short circuit determination threshold Vsht (S205: NO), the diagnosis unit 52 determines whether both of the pair of switching elements 22a and 22b in the switching circuit 22 or the switching circuit 23 It is diagnosed that both of the pair of switching elements 23a and 23b have an open failure (S207).

  On the other hand, when it is determined in step S202 that a current is output from the inverter circuit 2 (the output current Iout is not zero) (S202: NO), the diagnosis unit 52 is subsequently output from the inverter circuit 2. It is determined whether or not the current is flowing in the direction opposite to the direction assumed in the second signal input state (the direction from the connection point b through the load L toward the connection point a). In the present embodiment, since the direction from the connection point a through the load L to the connection point b is the positive direction, it is determined whether or not the output current Iout is greater than zero (S208).

  In step S208, when the current output from the inverter circuit 2 is flowing in the opposite direction (the output current Iout is greater than zero) (S208: YES), the diagnosis unit 52 includes the pair of switching elements 22a in the switching circuit 22. , 22b both have an open fault, both the pair of switching elements 23a, 23b in the switching circuit 23 have an open fault, and at least one of the pair of switching elements 21a, 21b in the switching circuit 21 has a short circuit fault. In addition, it is diagnosed that at least one of the pair of switching elements 24a and 24b in the switching circuit 24 is short-circuited (S209). On the contrary, when the current output from the inverter circuit 2 is flowing in the assumed direction (the output current Iout is smaller than zero) (S208: NO), the diagnosis unit 52 then determines that the inter-terminal voltage V2 is It is determined whether or not it is equal to or greater than the opening determination threshold Vop (S210).

  When it is determined in step S210 that the inter-terminal voltage V2 is equal to or higher than the open determination threshold Vop (S210: YES), the diagnosis unit 52 opens at least one of the pair of switching elements 22a and 22b in the switching circuit 22. It is determined that a failure has occurred (S211). On the other hand, when it is determined that the inter-terminal voltage V2 is not equal to or higher than the open determination threshold Vop (S210: NO), the diagnosis unit 52 subsequently determines whether or not the inter-terminal voltage V3 is equal to or higher than the open determination threshold Vop. (S212).

  When it is determined in step S212 that the inter-terminal voltage V3 is greater than or equal to the open determination threshold Vop (S212: YES), the diagnosis unit 52 opens at least one of the pair of switching elements 23a and 23b in the switching circuit 23. Diagnose that there is a failure (S213). On the other hand, when it is determined that the inter-terminal voltage V3 is not equal to or higher than the open determination threshold Vop (S212: NO), the diagnosis unit 52 determines that each of the switching circuits 21-24 when the drive unit 51 is in the second signal input state. Is diagnosed as operating normally (S214). That is, the pair of switching elements 22a and 22b in the switching circuit 22 and the pair of switching elements 23a and 23b in the switching circuit 23 have no open failure, and the pair of switching elements 21a and 21b in the switching circuit 21 and the pair of switching in the switching circuit 24 It is diagnosed that there is no short circuit failure in the elements 24a and 24b.

  As described above, the control circuit 5 executes the failure diagnosis process, whereby the failure diagnosis of the inverter circuit 2 is performed. After the failure diagnosis, the control circuit 5 notifies the diagnosis result by, for example, displaying on a display unit (not shown) or outputting sound through a speaker. In addition, about the diagnosis result (step S114) that it is operating normally in the first signal input state and the diagnosis result (step S214) that it is operating normally in the second signal input state, the diagnosis result is Notification may be performed or may not be performed. In addition, instead of notifying the diagnosis result, it may be stored in a storage unit (not shown) or transmitted to another communication device via a communication unit (not shown). In addition, the utilization method of a diagnostic result is not limited to what was mentioned above.

  Note that the failure diagnosis processing shown in the flowcharts of FIGS. 4 and 5 is an example, and is not limited to the above. For example, after completing the flowchart shown in FIG. 4, the control circuit 5 determines whether or not there is an open failure of the switching elements 21 a and 21 b in the switching circuit 21 and the switching elements 24 a and 24 b in the switching circuit 24, and the switching element 22 a in the switching circuit 22. , 22b and switching circuit 23 may be notified of the presence or absence of a short circuit failure in switching elements 23a, 23b. After the completion of the flowchart shown in FIG. 5, the control circuit 5 determines whether or not the switching elements 22 a and 22 b in the switching circuit 22 and the switching elements 23 a and 23 b in the switching circuit 23 have an open failure, and the switching element 21 a in the switching circuit 21. 21b and the switching element 24 in the switching circuit 24 may be notified of the presence or absence of a short circuit failure. That is, the control circuit 5 may notify the diagnosis result every time the flowchart shown in FIG. 4 and the flowchart shown in FIG. 5 are completed. Further, when it is diagnosed in step S104, S106, S107, S109, S111, S113, S204, S206, S207, S209, S211, or S213 that an open failure or a short-circuit failure has occurred, the diagnosis result is notified. Then, the remaining processing (each step) may be continued, or the failure diagnosis processing may be terminated without performing the remaining processing.

  Next, the operation and effect of the inverter device according to the present embodiment and the failure diagnosis method in the inverter device will be described.

  According to the present embodiment, in the switching circuit 21 (22-24) in which the plurality of switching elements 21a (22a-24a) and 21b (22b-24b) are connected in parallel, the pair of switching elements 21a (22a-24a) , 21b (22b-24b) can be diagnosed as to whether or not an open failure has occurred. Accordingly, since any one of the switching elements 21a (22a to 24a) and 21b (22b to 24b) can be found to be in an open failure, the inverter circuit 2 converts the DC power into AC power. Even if it exists, it can discover that the switching circuit 21 (22-24) is not normal. As a result, for example, parts can be replaced based on the diagnosis result, so that both of the switching elements 21a (22a to 24a) and 21b (22b to 24b) are prevented from being opened and damaged to other parts. it can.

  According to this embodiment, the control circuit 5 operates each switching element 21a-24a, 21b-24b using the active area | region in failure diagnosis processing. As shown in FIG. 3, the difference between the collector-emitter saturation voltages Vx and Vy when the active region is used is larger than the difference between the collector-emitter saturation voltages Vx 'and Vy' when the saturation region is used. When the gate-emitter voltage Vb [V] in FIG. 3 is used, the switching elements 21a to 24a and 21b to 24b operate in the saturation region. Therefore, when the operation is performed using the active region, when one of the pair of switching elements 21a (22a to 24a) and 21b (22b to 24b) has an open failure, both of them have failed. The difference between the detected terminal voltages V1 (V2 to V4) appears greatly depending on whether the voltage is not applied. Thereby, it is possible to suppress misdiagnosis in the diagnosis of whether one of the pair of switching elements 21a (22a to 24a) and 21b (22b to 24b) has an open failure.

  According to the present embodiment, in the switching circuit 21 (22-24) in which the plurality of switching elements 21a (22a-24a) and 21b (22b-24b) are connected in parallel, the pair of switching elements 21a (22a-24a) , 21b (22b to 24b) can be diagnosed as to whether or not a short circuit has occurred. Therefore, it is possible to diagnose not only an open fault but also a short-circuit fault.

  In the embodiment described above, the diagnosis unit 52 compares the inter-terminal voltage V1 (V2 to V4) with the open determination threshold value Vop, so that the pair of switching elements 21a (22a to 24a) and 21b (22b to 24b). It has been determined whether or not one of these has an open failure, but the following determination method may be used instead of or in addition to this. In the case of replacement, the following processing is performed in place of steps S110 and S112 (S210 and S212). In the case of addition, the following processing is performed between steps S108 (S208) and S110 (S210). What is necessary is just to add the process shown in. For example, the diagnosis unit 52 compares the inter-terminal voltage V1 and the inter-terminal voltage V4 when the driving unit 51 is in the first signal input state. When these differences are equal to or greater than a predetermined value, it may be diagnosed that either one of the pair of switching elements 21a and 21b or one of the pair of switching elements 24a and 24b has an open failure. In this case, the inter-terminal voltage V1 corresponds to the “first inter-terminal voltage” of the present invention, and the inter-terminal voltage V4 corresponds to the “second inter-terminal voltage” of the present invention. From this comparison result, the higher value is specified by the inter-terminal voltage V1 and the inter-terminal voltage V4, and one of the pair of switching elements in the larger switching circuit is diagnosed as having an open failure. Also good. Similarly, the diagnosis unit 52 compares the inter-terminal voltage V2 and the inter-terminal voltage V3 when the driving unit 51 is in the second signal input state, so that any of the pair of switching elements 22a and 22b is similarly detected. It may be diagnosed that either one or one of the pair of switching elements 23a and 23b has an open failure.

  In the modification, the inter-terminal voltage V1 and the inter-terminal voltage V4 are compared when the driving unit 51 is in the first signal input state, and the inter-terminal voltage is compared when the driving unit 51 is in the second signal input state. Although the case where the voltage V2 and the inter-terminal voltage V3 are compared has been described, the inter-terminal voltages V1 to V4 may be compared. Specifically, the diagnosis unit 52 includes the inter-terminal voltages V1 and V4 when the driving unit 51 is in the first signal input state, and the inter-terminal voltages V2 and V3 when the driving unit 51 is in the second signal input state. May be recorded, and the recorded inter-terminal voltages V1 to V4 may be compared. At this time, when the four inter-terminal voltages V1 to V4 are all the same, it can be diagnosed that the plurality of switching elements 21a to 24a and 21b to 24b are all normal. On the other hand, when at least one of the four terminal voltages V1 to V4 has a different value, it can be diagnosed that at least one of the plurality of switching elements 21a to 24a and 21b to 24b has an open failure. In this case as well, even if one of the four inter-terminal voltages V1 to V4 having a large value is specified and one of the pair of switching elements in the switching circuit having the large value is diagnosed as having an open failure, Good.

  In the said embodiment, although the case where the open fault and the short circuit fault were diagnosed was demonstrated to the example in at least any one of several switching element 21a-24a, 21b-24b, it is not necessary to diagnose a short circuit fault. For example, it is realized by omitting the processes of steps S103, S105, S203, and S205 in the fault diagnosis process (see FIGS. 4 and 5) performed by the control circuit 5. In this case, if it is determined in step S102 (S202) that the output current is zero, the diagnosis in step S107 (S207) may be performed. That is, it is diagnosed that both of the pair of switching elements 21a and 21b in the switching circuit 21 or both of the pair of switching elements 24a and 24b in the switching circuit 24 have an open failure (a pair of switching elements 22a in the switching circuit 22). , 22b, or both of the pair of switching elements 23a, 23b in the switching circuit 23 may be diagnosed).

  In the above embodiment, the diagnosis unit 52 determines whether or not the current output from the inverter circuit 2 flows in the direction opposite to the direction assumed in each of the first signal input state and the second signal input state. (See steps S108 and S208), the determination may not be performed. In this case, steps S108, S109, S208, and S209 may be omitted.

  In the above-described embodiment, the drive unit 51 has been described with respect to the case where the switching elements 21a to 24a and 21b to 24b are operated in the active region in the failure diagnosis process. However, the present invention is not limited to this. For example, the diagnosis can be performed as described above even when the operation is performed in the saturation region instead of the active region. However, for accurate diagnosis, it is better to operate the switching elements 21a to 24a and 21b to 24b in the active region as in the above embodiment. Whether the operation is performed in the active region or the saturation region may be performed by adjusting the ON signal input to each of the switching elements 21a to 24a and 21b to 24b and changing the gate-emitter voltage.

  In the above embodiment, the case where two switching elements are connected in parallel in each of the switching circuits 21 to 24 has been described, but three or more switching elements may be connected in parallel. In this case as well, it is possible to diagnose whether at least one of the plurality of switching elements connected in parallel in each of the switching circuits 21 to 24 has an open failure or a short-circuit failure. For example, the case where three switching elements are connected in parallel in each switching circuit will be described.

  FIG. 6 shows a switching circuit 29 in which three switching elements 29a to 29c are connected in parallel. For example, it is assumed that an ON signal is input to the three switching elements 29a to 29c illustrated in FIG. The gate-emitter voltages at this time are assumed to be Va [V], respectively. Further, the input current to the switching circuit 29 is Ia [A].

  When the three switching elements 29a to 29c are operating normally (on state) under the above conditions, the input current Ia [A] to the switching circuit 29 is divided into three, and each switching element 29a to 29c A current of Ia / 3 [A] flows in each of 29c. At this time, as shown in FIG. 3, the collector-emitter saturation voltage is Vz [V]. That is, the voltage between the terminals of the switching circuit 29 is Vz [V]. However, when any one of the three switching elements 29a to 29c (for example, the switching element 29c) has an open failure, each of the remaining two switching elements (switching elements 29a and 29b) A current of Ia / 2 [A] flows. At this time, as shown in FIG. 3, the collector-emitter saturation voltage is Vx [V]. That is, the voltage between the terminals of the switching circuit 29 is Vx [V]. Further, when any two switching elements (for example, the switching elements 29b and 29c) of the three switching elements 29a to 29c are in an open failure, the remaining one switching element (switching element 29a) has Ia [ A] current flows. At this time, as shown in FIG. 3, the collector-emitter saturation voltage is Vy [V]. That is, the voltage between the terminals of the switching circuit 29 is Vy [V].

  Based on such changes, the two open determination thresholds are set, and the diagnosis unit 52 compares the two open determination thresholds with the voltage between the terminals of the switching circuit 29 to thereby switch the three switching elements 29a to 29a. It is possible to diagnose whether at least one of 29c has an open failure. Specifically, the first opening determination threshold value Vop1 is set to a value not less than Vx and not more than Vy, and the second opening determination threshold value Vop2 is set to not less than Vz and less than Vx. If the voltage between the terminals of the switching circuit 29 when the ON signal is input to the three switching elements 29a to 29c is equal to or higher than the first open determination threshold Vop1, the diagnosis unit 52 includes the three switching elements 29a. It can be determined that two of ˜29c have an open failure. Further, if it is less than the first opening determination threshold value Vop1 and not less than the second opening determination threshold value Vop2, the diagnosis unit 52 determines that one of the three switching elements 29a to 29c has an open failure. it can. Furthermore, if it is less than the second opening determination threshold value Vop2, the diagnosis unit 52 can determine that all the three switching elements 29a to 29c are normal. Note that when all of the three switching elements 29a to 29c have an open failure, no current flows through the switching circuit 29 (the output current becomes zero), so the diagnosis unit 52 is based on the detection value of the current sensor 41. You can judge. Whether at least any one of the three switching elements 29a to 29c is short-circuited or not is compared with the voltage between the terminals of the switching circuit 29 when the OFF signal is input to these and the short-circuit determination threshold value. Therefore, it is sufficient to make a judgment. What is necessary is just to set the short circuit determination threshold value at this time to 0 or more and less than Vz, for example.

  From the above, in a switching circuit in which three or more switching elements are connected in parallel, a plurality of open determinations are made based on the electrical characteristics (collector-emitter saturation voltage characteristics) of the three or more switching elements. A threshold is set. Then, the diagnosis unit 52 compares the plurality of open determination threshold values with the voltage across the terminals of the switching circuit. Thereby, the diagnosis part 52 can diagnose how many switching elements of the three or more switching elements have an open failure based on the comparison result. In addition, a short circuit failure can be diagnosed as described above.

  In the above embodiment, the case where the four signal lines 511 to 514 are connected to the control circuit 5 and branched to input to the switching elements 21a to 24a and 21b to 24b has been described. However, the present invention is not limited to this. For example, eight signal lines may be connected to the control circuit 5 and connected to the gate terminals of the switching elements 21a to 24a and 21b to 24b, respectively. By doing in this way, the drive part 51 can input either an ON signal or an OFF signal for each switching element 21a-24a, 21b-24b, respectively. Thereby, for example, the diagnosis unit 52 determines which one of the pair of switching elements 21a (22a to 24a) and 21b (22b to 24b) diagnosed as one of the open failure or the short circuit failure in the failure diagnosis process. It is possible to specify whether an open fault or a short-circuit fault has occurred. Specifically, when the diagnosis unit 52 diagnoses that any one of the pair of switching elements 21a (22a to 24a) and 21b (22b to 24b) has an open failure or a short circuit failure, the drive unit 51 However, an ON signal is input into one of a pair of switching elements 21a (22a-24a) and 21b (22b-24b), and an OFF signal is input into the other. Then, based on the inter-terminal voltage V1 (V2 to V4) and the output current Iout at this time, which of the pair of switching elements 21a (22a to 24a) and 21b (22b to 24b) has an open failure or a short circuit failure You can identify whether you are doing. For example, when the switching element 21a has an open failure and the switching element 21b is normal, when it is diagnosed that one of the switching elements 21a and 21b has an open failure, the drive unit 51 An ON signal is input to 21a, and an OFF signal is input to the switching element 21b. Then, since the switching circuit 21 is cut off, no current is output from the inverter circuit 2 (the output current Iout becomes zero). On the other hand, an OFF signal is input to the switching element 21a, and an ON signal is input to the switching element 21b. Then, since the switching circuit 21 is turned on, a current is output from the inverter circuit 2. Therefore, it can be diagnosed that the switching element 21a has an open failure. As described above, in the switching circuit 21 (22 to 24), the diagnosis unit 52 causes one of the pair of switching elements 21a (22a to 24a) and 21b (22b to 24b) to be open or short-circuited. Can be specified.

  In the said embodiment, although the case where the inverter circuit 2 was a full bridge type inverter circuit using the four switching circuits 21-24 was demonstrated, it is not limited to this. For example, a half-bridge type inverter circuit using two switching circuits may be used. Further, any circuit that converts input power into predetermined output power by switching between a conduction state and a cutoff state of one or more switching circuits can be applied as appropriate. Examples of such a circuit include a chopper circuit, a converter circuit, and an amplifier circuit. Even in such cases, the inter-terminal voltage and output current of the switching circuit are detected, and based on these, it is determined whether or not at least one of the plurality of switching elements in the switching circuit has an open fault or a short-circuit fault. Can be diagnosed. In these cases, the circuit described above corresponds to the “main circuit” of the present invention.

  The power converter and the failure diagnosis method according to the present invention are not limited to the above-described embodiments. The specific configuration of each part of the power conversion device of the present invention and the specific processing of each step of the failure diagnosis method can be varied in design in various ways.

1: DC power supply (power source)
2: Inverter circuit (main circuit, power converter)
20A: Arm 20B: Arms 21-24, 29: Switching circuits 21a-24a, 21b-24b, 29a-29c: Switching elements 31-34: Voltage sensors (voltage detection means)
41: Current sensor 5: Control circuit (power converter)
51: Drive unit (signal input means)
52: Diagnostic unit (diagnostic means)
L: Load

Claims (8)

A main circuit including a switching circuit in which a plurality of switching elements are connected in parallel with each other, and converting input power from a power source into predetermined output power;
Voltage detecting means for detecting a voltage between terminals of the switching circuit;
A signal input means capable of inputting an on signal for turning on each of the switching elements to each of the plurality of switching elements;
Diagnosing that at least one of the plurality of switching elements has an open failure when the voltage between the terminals when the ON signal is input to each of the plurality of switching elements is greater than or equal to an open determination threshold value Means,
A power conversion device comprising: The diagnostic means has a short circuit failure in any of the plurality of switching elements when the voltage between the terminals when the ON signal is not input to each of the plurality of switching elements is equal to or less than a short circuit determination threshold. To diagnose,
The power conversion device according to claim 1. The power source is a DC power source;
The main circuit includes the switching circuit on the high potential side connected to the output terminal on the high potential side of the DC power supply and the switching on the low potential side connected to the output terminal on the low potential side of the DC power supply. An inverter circuit having a first arm and a second arm connected in series with the circuit, wherein the first arm and the second arm are connected in parallel;
The power converter device of Claim 1 or Claim 2. The voltage detection means detects a first terminal voltage in the high-potential side switching circuit of the first arm and a second terminal voltage in the low-potential side switching circuit of the second arm,
The diagnostic means includes the signal input means connected to the plurality of switching elements in the switching circuit on the high potential side of the first arm and the switching elements in the switching circuit on the low potential side of the second arm. An ON signal is input, and the on-state is applied to the plurality of switching elements in the low-potential side switching circuit of the first arm and the plurality of switching elements in the high-potential side switching circuit of the second arm. When a current is output from the inverter circuit when no signal is input, the first inter-terminal voltage and the second inter-terminal voltage are compared. One of the plurality of switching elements in the high-potential side switching circuit of one arm, or , It is diagnosed that one of the plurality of switching elements in the switching circuit of the low-potential side of the second arm is open fault,
The power conversion device according to claim 3. The diagnostic means includes the signal input means connected to the plurality of switching elements in the switching circuit on the high potential side of the first arm and the switching elements in the switching circuit on the low potential side of the second arm. An ON signal is input, and the on-state is applied to the plurality of switching elements in the low-potential side switching circuit of the first arm and the plurality of switching elements in the high-potential side switching circuit of the second arm. When no signal is input and no current is output from the inverter circuit, both of the plurality of switching elements in the high-potential side switching circuit of the first arm, or the second arm The plurality of switchings in the switching circuit on the low potential side It is diagnosed that both of the child is open-circuit failure,
The power converter device of Claim 3 or Claim 4. The signal input means inputs the ON signal for operating each switching element in an active region.
The power converter device as described in any one of Claims 1 thru | or 5. The signal input means can input the ON signal only to any one of the plurality of switching elements in the switching circuit.
The power converter according to any one of claims 1 to 6. A failure diagnosis method for a main circuit, which includes a switching circuit in which a plurality of switching elements are connected in parallel to each other, and converts input power from a power source into predetermined output power,
Inputting an on signal for turning on each switching element to each of the plurality of switching elements;
Detecting a voltage between terminals of the switching circuit;
A step of diagnosing that at least one of the plurality of switching elements has an open failure when the voltage between the terminals when the ON signal is input to each of the plurality of switching elements is equal to or higher than an open determination threshold value. When,
A failure diagnosis method comprising:

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