Power conversion device

Abstract

To provide a power conversion device capable of easily inspecting conduction states of a switching element and a diode.SOLUTION: A power conversion device 6 comprises: an IGBT 24; a diode 34 which is electrically connected to the IGBT 24; a first switch 52 of which one terminal is electrically connected to an anode of the diode 34; a second switch 54 of which one terminal is electrically connected to an emitter terminal 24e of the IGBT 24; a third switch 56 of which one terminal is electrically connected to a connection point 62 of the IGBT 24 and the diode 34; a DC power source 58 of which one electrode is electrically connected to the other terminal of the third switch 56 and the other electrode is electrically connected to the other terminals of the first switch 52 and the second switch 54; a light-emitting element 60 for reporting short-circuiting or disconnection of the IGBT 24 and the diode 34; and a changeover section 50 for changing over ON and OFF of the first switch 52, the second switch 54 and the third switch 56.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a power conversion device including a switching element and a diode electrically connected in series with each other. [Background technology]

[0002] An induction heating device for induction heating an object to be heated is known (see, for example, Patent Document 1). A conventional induction heating device includes a power converter, a matching circuit, and an induction coil. The power converter is an inverter circuit having multiple switching elements, and generates a high-frequency current by turning the multiple switching elements on and off at high speed. Each of the multiple switching elements is electrically connected in series with multiple diodes to prevent backflow. The matching circuit is a parallel resonant circuit electrically connected between the power converter and the induction coil. The induction coil is arranged to surround the object to be heated.

[0003] High-frequency current from the power converter is supplied to the induction coil via a matching circuit. The alternating magnetic flux generated by this high-frequency current penetrates the inside of the object to be heated, causing eddy currents to flow inside the object. The Joule heat generated by these eddy currents induces heating of the object. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-217805 Summary of the Invention [Problem to be solved by the invention]

[0005] In the conventional induction heating device described above, when the power conversion device fails, at least one of the multiple switching elements and multiple diodes is often short-circuited or open-circuited. Therefore, an operator or the like uses a tester to check the continuity of each of the multiple switching elements and multiple diodes one by one. However, such testing using a tester is cumbersome and time-consuming.

[0006] The present invention is intended to solve the above-mentioned problems, and has as its object to provide a power conversion device that can easily test the conduction state of each of the switching elements and diodes. [Means for solving the problem]

[0007] (Technology 1) a switching element having a first terminal, a second terminal, and a third terminal, and in which conduction between the first terminal and the second terminal is controlled in accordance with a voltage or current input to the third terminal; a diode having one terminal electrically connected to the first terminal of the switching element; a first switch having one terminal electrically connected to the other terminal of the diode; a second switch having one terminal electrically connected to the second terminal of the switching element; a third switch having one terminal electrically connected to a connection point between the first terminal of the switching element and the one terminal of the diode; a power supply electrically connected to the other terminal of the first switch and having its other pole electrically connected to each of the other terminals of the first switch and the second switch; an alarm element for alarming a short circuit or an open circuit of the switching element and the diode, the alarm element being electrically connected to at least one of (i) between the other terminal of the diode and the other pole of the power supply, (ii) between the second terminal of the switching element and the other pole of the power supply, and (iii) between the connection point and the one pole of the power supply; and a switching unit for switching on and off each of the first switch, the second switch, and the third switch.

[0008] According to Technology 1, when a failure occurs in the power conversion device, the switching unit switches the first switch, the second switch, and the third switch on and off, and the notification element notifies the short circuit or open circuit of the switching element and the diode, thereby allowing an operator or the like to easily check the continuity state of each of the switching element and the diode.

[0009] (Technology 2) The power conversion device according to technology 1, wherein the power source is a DC power source for supplying DC power, and the notification element is a light-emitting element electrically connected between the connection point and the one pole of the power source.

[0010] According to Technology 2, an operator can easily inspect the conduction state of each of the switching elements and diodes based on the lighting state of the light-emitting element when the first switch, the second switch, and the third switch are switched on and off by the switching unit.

[0011] (Technology 3) The power supply is an AC power supply for supplying AC power, and the notification element includes a first light-emitting element and a second light-emitting element electrically connected in parallel between the other terminal of the diode and the other pole of the power supply, a third light-emitting element and a fourth light-emitting element electrically connected in parallel between the second terminal of the switching element and the other pole of the power supply, a first diode electrically connected in series to the first light-emitting element, a second diode electrically connected in series to the second light-emitting element, a third diode electrically connected in series to the third light-emitting element, and a fourth diode electrically connected in series to the fourth light-emitting element.

[0012] According to Technology 3, an operator or the like can easily inspect the conduction state of each of the switching elements and diodes based on the lighting states of the first light-emitting element, the second light-emitting element, the third light-emitting element, and the fourth light-emitting element when the first switch, the second switch, and the third switch are switched on and off by the switching unit.

[0013] (Technology 4) The power conversion device according to technology 1, wherein the power source is a DC power source for supplying DC power, and the notification element is a relay coil electrically connected between the connection point and the one pole of the power source.

[0014] According to Technology 4, an operator can easily inspect the conduction state of each of the switching elements and diodes based on the output of the relay coil when the first switch, the second switch, and the third switch are switched on and off by the switching unit.

[0015] These comprehensive or specific aspects may be realized as a system, a method, an integrated circuit, a computer program, or a computer-readable recording medium such as a CD-ROM, or may be realized as any combination of a system, a method, an integrated circuit, a computer program, and a recording medium. [Effects of the Invention]

[0016] According to the power conversion device according to one aspect of the present invention, the conduction states of the switching elements and diodes can be easily inspected. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a diagram showing a circuit configuration of an induction heating device according to a first embodiment. [Figure 2] FIG. 3 is a diagram illustrating an example of a switching unit according to the first embodiment. [Figure 3] 2 is a diagram showing the circuit configuration of each of a first detection circuit and a second detection circuit according to the first embodiment; FIG. [Figure 4] FIG. 4 is a diagram for explaining the operation of the first detection circuit according to the first embodiment. [Figure 5] FIG. 4 is a diagram for explaining the operation of the first detection circuit according to the first embodiment. [Figure 6] FIG. 10 is a diagram showing a circuit configuration of a first detection circuit according to a second embodiment. [Figure 7] FIG. 10 is a diagram for explaining the operation of the first detection circuit according to the second embodiment. [Figure 8] FIG. 10 is a diagram for explaining the operation of the first detection circuit according to the second embodiment. [Figure 9] FIG. 10 is a diagram for explaining the operation of the first detection circuit according to the second embodiment. [Figure 10] FIG. 10 is a diagram showing a circuit configuration of a first detection circuit according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, the embodiments will be specifically described with reference to the drawings.

[0019] The embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, component placement and connection configurations, steps, and step order shown in the following embodiments are merely examples and are not intended to limit the scope of the claims. Furthermore, among the components in the following embodiments, components that are not described in the independent claims that represent the highest concepts are described as optional components.

[0020] In addition, the drawings are not necessarily strict illustrations, and the same reference numerals are used to designate substantially the same components in the drawings, and redundant explanations are omitted or simplified.

[0021] (Embodiment 1) [1-1. Circuit configuration of induction heating device] First, the circuit configuration of an induction heating device 2 according to embodiment 1 will be described with reference to Fig. 1 and Fig. 2. Fig. 1 is a diagram showing the circuit configuration of an induction heating device 2 according to embodiment 1. Fig. 2 is a diagram showing an example of a switching unit 50 according to embodiment 1.

[0022] As shown in Fig. 1, induction heating device 2 is a device for induction heating (so-called induction hardening) an object 4 to be heated with a high frequency of, for example, several kHz to several hundred kHz. Note that induction hardening is a heat treatment in which high frequency electromagnetic induction is generated to heat and harden each surface of object 4 to be heated. Object 4 to be heated is, for example, a tubular metal part used in a vehicle, machine tool, or the like.

[0023] As shown in FIG. 1, the induction heating device 2 includes a power conversion device 6, a matching circuit 8, and an induction coil .

[0024] The power conversion device 6 is an oscillator for outputting a high-frequency current of a predetermined frequency, and includes a rectifier circuit 12, choke coils 14 and 16, and an inverter circuit .

[0025] The rectifier circuit 12 is, for example, a full-wave rectifier circuit using six thyristors 20, and converts AC power from a commercial power supply 22 into DC power. The commercial power supply 22 is, for example, a three-phase AC power supply, and supplies three-phase 60 Hz (or 50 Hz) AC power.

[0026] The choke coils 14 and 16 are electrically connected to the anode and cathode sides of the output side (DC side) of the rectifier circuit 12, respectively, and smooth the DC power from the rectifier circuit 12.

[0027] The inverter circuit 18 is electrically connected to the output side of the rectifier circuit 12 via the choke coils 14 and 16. The inverter circuit 18 is a single-phase full-bridge inverter circuit using, for example, four IGBTs 24 (an example of switching elements), and converts smoothed DC power into single-phase high-frequency power by turning the four IGBTs 24 on and off at high speed. This allows the power conversion device 6 to generate a high-frequency current of a predetermined frequency.

[0028] The inverter circuit 18 has a first switching unit 26, a second switching unit 28, a third switching unit 30, and a fourth switching unit 32. The first switching unit 26 and the second switching unit 28 are electrically connected in series. The third switching unit 30 and the fourth switching unit 32 are electrically connected in series. Furthermore, the first switching unit 26 and the second switching unit 28 are electrically connected in parallel with the third switching unit 30 and the fourth switching unit 32.

[0029] The first switching unit 26 and the third switching unit 30 have the same configuration, and the second switching unit 28 and the fourth switching unit 32 have the same configuration. Therefore, only the configurations of the first switching unit 26 and the second switching unit 28 will be described below.

[0030] The first switching section 26 includes the IGBT 24, a diode 34, and a reverse conducting diode 36.

[0031] The IGBT 24 of the first switching unit 26 has a collector terminal 24c (an example of a first terminal), an emitter terminal 24e (an example of a second terminal), and a gate terminal 24g (an example of a third terminal), and conduction between the collector terminal 24c and the emitter terminal 24e is controlled according to the voltage input to the gate terminal 24g.

[0032] The diode 34 of the first switching unit 26 is a diode for preventing reverse current. The cathode (an example of one terminal) of the diode 34 is electrically connected to the collector terminal 24c of the IGBT 24. The anode (an example of the other terminal) of the diode 34 is electrically connected to the choke coil 14.

[0033] The reverse conducting diode 36 of the first switching unit 26 is electrically connected between the collector terminal 24c and the emitter terminal 24e of the IGBT 24. Specifically, the cathode of the reverse conducting diode 36 is electrically connected to the collector terminal 24c of the IGBT 24, and the anode of the reverse conducting diode 36 is electrically connected to the emitter terminal 24e of the IGBT 24. The reverse conducting diode 36 is incorporated into a package together with the IGBT 24, for example.

[0034] Similar to the first switching unit 26, the second switching unit 28 includes an IGBT 24, a diode 34, and a reverse conducting diode 36. However, in the second switching unit 28, the connection relationship between the IGBT 24 and the diode 34 differs from that in the first switching unit 26.

[0035] The IGBT 24 of the second switching unit 28 has a collector terminal 24c (an example of a second terminal), an emitter terminal 24e (an example of a first terminal), and a gate terminal 24g (an example of a third terminal), and conduction between the collector terminal 24c and the emitter terminal 24e is controlled according to the voltage input to the gate terminal 24g. The collector terminal 24c of the IGBT 24 of the second switching unit 28 is electrically connected to the emitter terminal 24e of the IGBT 24 of the first switching unit 26.

[0036] The diode 34 of the second switching unit 28 is a diode for preventing reverse current. The anode (an example of one terminal) of the diode 34 is electrically connected to the emitter terminal 24e of the IGBT 24. The cathode (an example of the other terminal) of the diode 34 is electrically connected to the choke coil 16.

[0037] The reverse conducting diode 36 of the second switching unit 28 is electrically connected between the collector terminal 24c and the emitter terminal 24e of the IGBT 24. Specifically, the cathode of the reverse conducting diode 36 is electrically connected to the collector terminal 24c of the IGBT 24, and the anode of the reverse conducting diode 36 is electrically connected to the emitter terminal 24e of the IGBT 24. The reverse conducting diode 36 is incorporated into a package together with the IGBT 24, for example.

[0038] In this embodiment, the IGBT 24 is used as the switching element, but the present invention is not limited thereto. For example, a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) or a bipolar transistor may be used. The MOSFET has a drain terminal (an example of a first terminal or a second terminal), a source terminal (an example of a second terminal or a first terminal), and a gate terminal (an example of a third terminal), and conduction between the drain terminal and the source terminal is controlled according to a voltage input to the gate terminal. The bipolar transistor has a collector terminal (an example of a first terminal or a second terminal), an emitter terminal (an example of a second terminal or a first terminal), and a base terminal (an example of a third terminal), and conduction between the collector terminal and the emitter terminal is controlled according to a current input to the base terminal.

[0039] The matching circuit 8 is for supplying the active power generated by the power conversion device 6 to the induction coil 10 with high efficiency. The input side of the matching circuit 8 is electrically connected to the AC side of the inverter circuit 18. The matching circuit 8 is a parallel resonant circuit configured with a capacitor 38 and a matching transformer 40.

[0040] The induction coil 10 is electrically connected to the output side of the matching circuit 8. The induction coil 10 is used to inductively heat the object 4, and is arranged to surround the object 4. When a high-frequency current from the power conversion device 6 is supplied to the induction coil 10 via the matching circuit 8, the object 4 is inductively heated.

[0041] The inverter circuit 18 is controlled by a controller (not shown) so as to be switched between a first state and a second state at high frequency. In the first state, the IGBTs 24 in the first switching unit 26 and the fourth switching unit 32 are turned on, and the IGBTs 24 in the second switching unit 28 and the third switching unit 30 are turned off. As a result, as shown by the black arrow P in FIG. 1 , a current flows in the following order: diode 34 in the first switching unit 26 → IGBT 24 in the first switching unit 26 → matching circuit 8 → induction coil 10 → matching circuit 8 → IGBT 24 in the fourth switching unit 32 → diode 34 in the fourth switching unit 32.

[0042] On the other hand, in the second state, the IGBTs 24 in the second switching unit 28 and the third switching unit 30 are turned on, and the IGBTs 24 in the first switching unit 26 and the fourth switching unit 32 are turned off. As a result, as shown by the outlined arrow Q in Fig. 1, current flows in the following order: diode 34 in the third switching unit 30 → IGBT 24 in the third switching unit 30 → matching circuit 8 → induction coil 10 → matching circuit 8 → IGBT 24 in the second switching unit 28 → diode 34 in the second switching unit 28.

[0043] The induction heating device 2 further includes a first detection circuit 42, a second detection circuit 44, a third detection circuit 46, a fourth detection circuit 48, and a switching unit 50.

[0044] The first detection circuit 42, the second detection circuit 44, the third detection circuit 46, and the fourth detection circuit 48 are provided corresponding to the first switching unit 26, the second switching unit 28, the third switching unit 30, and the fourth switching unit 32, respectively. The first detection circuit 42 and the third detection circuit 46 have the same configuration, and the second detection circuit 44 and the fourth detection circuit 48 have the same configuration. Therefore, only the configuration of the first detection circuit 42 and the second detection circuit 44 will be described below.

[0045] The first detection circuit 42, the second detection circuit 44, the third detection circuit 46 and the fourth detection circuit 48 may be, for example, pre-installed inside the housing (not shown) of the induction heating device 2, or may be later attached to the power conversion device 6 of the induction heating device 2 as an inspection jig.

[0046] The switching unit 50 switches on (conducting) and off (disconnecting) each of the switches (described later) of the first detection circuit 42, the second detection circuit 44, the third detection circuit 46, and the fourth detection circuit 48. The switching unit 50 is, for example, a rotary switch as shown in FIG. 2. When an operator or the like rotates the switching unit 50 to a position marked "run," the switching unit 50 simultaneously turns off each of the switches of the first detection circuit 42, the second detection circuit 44, the third detection circuit 46, and the fourth detection circuit 48. On the other hand, when an operator or the like rotates the switching unit 50 to a position marked "check," the switching unit 50 simultaneously turns on each of the switches of the first detection circuit 42, the second detection circuit 44, the third detection circuit 46, and the fourth detection circuit 48.

[0047] The switching unit 50 may be arranged in advance on a control panel or the like on the front surface of the housing of the induction heating device 2, or may be attached to the power converter 6 of the induction heating device 2 later as an inspection jig.

[0048] Furthermore, in the present embodiment, one switching unit 50 is provided for the first detection circuit 42, the second detection circuit 44, the third detection circuit 46, and the fourth detection circuit 48, but this is not limiting, and a first switching unit, a second switching unit, a third switching unit, and a fourth switching unit may be provided for the first detection circuit 42, the second detection circuit 44, the third detection circuit 46, and the fourth detection circuit 48, respectively. This allows the switches of the first detection circuit 42, the second detection circuit 44, the third detection circuit 46, and the fourth detection circuit 48 to be switched on and off independently.

[0049] [1-2. Circuit configuration of the first detection circuit] The circuit configuration of the first detection circuit 42 will be described with reference to Fig. 3. Fig. 3 is a diagram showing the circuit configurations of the first detection circuit 42 and the second detection circuit 44 according to the first embodiment.

[0050] As shown in FIG. 3, the first detection circuit 42 has a first switch 52, a second switch 54, a third switch 56, a DC power supply 58 (an example of a power supply), and a light-emitting element 60 (an example of an alarm element).

[0051] The first switch 52 is, for example, a contact a switch that can be switched on and off. The first switch 52 is electrically connected between the diode 34 and the DC power supply 58. Specifically, one terminal of the first switch 52 is electrically connected to the anode of the diode 34. The other terminal of the first switch 52 is electrically connected to the cathode (an example of the other pole) of the DC power supply 58.

[0052] The second switch 54 is, for example, a contact a switch that can be switched on and off. The second switch 54 is electrically connected between the IGBT 24 and the DC power supply 58. Specifically, one terminal of the second switch 54 is electrically connected to the emitter terminal 24e of the IGBT 24. The other terminal of the second switch 54 is electrically connected to the cathode of the DC power supply 58.

[0053] The third switch 56 is, for example, a contact a switch that can be switched on and off. The third switch 56 is electrically connected between a connection point 62 of the IGBT 24 and the diode 34 and a DC power supply 58. Specifically, one terminal of the third switch 56 is electrically connected to the connection point 62 between the collector terminal 24c of the IGBT 24 and the cathode of the diode 34. The other terminal of the third switch 56 is electrically connected to the anode (an example of one pole) of the DC power supply 58 via the light-emitting element 60.

[0054] The DC power supply 58 is a power supply circuit for supplying DC power. An anode of the DC power supply 58 is electrically connected to the other terminal of the third switch 56 via the light-emitting element 60. A cathode of the DC power supply 58 is electrically connected to the other terminal of the first switch 52 and the other terminal of the second switch 54.

[0055] The light-emitting element 60 is an element, such as a light-emitting diode, for reporting a short circuit between the IGBT 24 and the diode 34. The light-emitting element 60 is electrically connected between a connection point 62 between the IGBT 24 and the diode 34 and the anode of the DC power supply 58. Specifically, one terminal of the light-emitting element 60 is electrically connected to the connection point 62 between the collector terminal 24c of the IGBT 24 and the cathode of the diode 34 via the third switch 56. The other terminal of the light-emitting element 60 is electrically connected to the anode of the DC power supply 58.

[0056] [1-3. Circuit configuration of the second detection circuit] Next, the circuit configuration of the second detection circuit 44 will be described with reference to Fig. 3. As shown in Fig. 3, the second detection circuit 44, like the first detection circuit 42, has a first switch 52, a second switch 54, a third switch 56, a DC power supply 58, and a light-emitting element 60.

[0057] The first switch 52 is, for example, a contact a switch that can be switched on and off. The first switch 52 is electrically connected between the diode 34 and the DC power supply 58. Specifically, one terminal of the first switch 52 is electrically connected to the cathode of the diode 34. The other terminal of the first switch 52 is electrically connected to the anode (an example of the other pole) of the DC power supply 58.

[0058] The second switch 54 is, for example, a contact a switch that can be switched on and off. The second switch 54 is electrically connected between the IGBT 24 and a DC power supply 58. Specifically, one terminal of the second switch 54 is electrically connected to the collector terminal 24c of the IGBT 24. The other terminal of the second switch 54 is electrically connected to the anode of the DC power supply 58.

[0059] The third switch 56 is, for example, a contact a switch that can be switched on and off. The third switch 56 is electrically connected between a connection point 64 of the IGBT 24 and the diode 34 and a DC power supply 58. Specifically, one terminal of the third switch 56 is electrically connected to the connection point 64 between the emitter terminal 24e of the IGBT 24 and the anode of the diode 34. The other terminal of the third switch 56 is electrically connected to the cathode (an example of one pole) of the DC power supply 58 via the light-emitting element 60.

[0060] The DC power supply 58 is a power supply circuit for supplying DC power. The cathode of the DC power supply 58 is electrically connected to the other terminal of the third switch 56 via the light-emitting element 60. The anode of the DC power supply 58 is electrically connected to the other terminal of the first switch 52 and the other terminal of the second switch 54.

[0061] The light-emitting element 60 is an element, such as a light-emitting diode, for reporting a short circuit between the IGBT 24 and the diode 34. The light-emitting element 60 is electrically connected between a connection point 64 between the IGBT 24 and the diode 34 and the cathode of the DC power supply 58. Specifically, one terminal of the light-emitting element 60 is electrically connected to the connection point 64 between the emitter terminal 24e of the IGBT 24 and the anode of the diode 34 via the third switch 56. The other terminal of the light-emitting element 60 is electrically connected to the cathode of the DC power supply 58.

[0062] [1-4. Operation of the first detection circuit] The operation of the first detection circuit 42 will be described with reference to Figures 4 and 5. Figures 4 and 5 are diagrams for explaining the operation of the first detection circuit 42 according to the first embodiment.

[0063] Since the operation of the first detection circuit 42 and the operation of the second detection circuit are similar, a description of the operation of the second detection circuit will be omitted.

[0064] First, the operation of the first detection circuit 42 when the IGBT 24 and the diode 34 are both normal (i.e., not short-circuited) will be described with reference to Fig. 4. In this case, it is assumed that there is no electrical continuity between the collector terminal 24c and the emitter terminal 24e of the IGBT 24.

[0065] For example, when an operator or the like turns the switching unit 50 to the position marked "Run" (see FIG. 2), as shown in FIG. 4(a), the switching unit 50 simultaneously turns off the first switch 52, the second switch 54, and the third switch 56. In this state, the current from the DC power supply 58 is cut off by the first switch 52, the second switch 54, and the third switch 56. Therefore, no current flows through the light-emitting element 60, and the light-emitting element 60 is turned off.

[0066] Furthermore, for example, when an operator or the like turns the switching unit 50 to the position marked "check" (see FIG. 2), the switching unit 50 simultaneously turns on the first switch 52, the second switch 54, and the third switch 56, as shown in FIG. 4(b). In this state, current from the DC power supply 58 does not flow through the reverse diode 34, nor does it flow through the non-conducting IGBT 24. Therefore, no current flows through the light-emitting element 60, and the light-emitting element 60 remains off.

[0067] In this way, if the light-emitting element 60 remains off even when the worker rotates the switching unit 50 to the position marked "check," the worker can determine that both the IGBT 24 and the diode 34 are normal.

[0068] Next, the operation of the first detection circuit 42 when the IGBT 24 is normal but the diode 34 is short-circuited will be described with reference to Fig. 5. In this case, it is assumed that there is no electrical continuity between the collector terminal 24c and the emitter terminal 24e of the IGBT 24.

[0069] For example, when an operator or the like turns the switching unit 50 to the position marked "Run," the switching unit 50 simultaneously turns off the first switch 52, the second switch 54, and the third switch 56, as shown in (a) of FIG. 5. In this state, the current from the DC power supply 58 is cut off by the first switch 52, the second switch 54, and the third switch 56. Therefore, no current flows through the light-emitting element 60, and the light-emitting element 60 is turned off.

[0070] Furthermore, for example, when an operator or the like rotates the switching unit 50 to the position marked "check," the switching unit 50 simultaneously turns on the first switch 52, the second switch 54, and the third switch 56, as shown in FIG. 5(b). In this state, current from the DC power supply 58 does not flow through the non-conducting IGBT 24, but does flow through the short-circuited diode 34. As a result, current flows through the light-emitting element 60, causing the light-emitting element 60 to light up.

[0071] Although not shown, when at least one of the IGBT 24, the diode 34, and the reverse conducting diode 36 is short-circuited, the switching unit 50 simultaneously turns on the first switch 52, the second switch 54, and the third switch 56, and the current from the DC power supply 58 flows through at least one of the short-circuited IGBT 24, the diode 34, and the reverse conducting diode 36. Therefore, in this case as well, a current flows through the light-emitting element 60, and the light-emitting element 60 lights up.

[0072] In this way, when the worker rotates the switching unit 50 to the position marked "check" and the light-emitting element 60 lights up, the worker can determine that at least one of the IGBT 24, the diode 34, and the reverse conducting diode 36 is short-circuited.

[0073] In the present embodiment, the switching unit 50 simultaneously turns on or off the first switch 52, the second switch 54, and the third switch 56, but this is not limiting. For example, when an operator or the like rotates the switching unit 50 to a position marked "Check 1," the switching unit 50 may simultaneously turn on the first switch 52 and the third switch 56 and turn off the second switch 54. Furthermore, when an operator or the like rotates the switching unit 50 to a position marked "Check 2," the switching unit 50 may simultaneously turn on the second switch 54 and the third switch 56 and turn off the first switch 52.

[0074] As a result, if the light-emitting element 60 lights up when the switching unit 50 is rotated to the position marked "Check 1," the worker can determine that the diode 34 is short-circuited, and if the light-emitting element 60 lights up when the switching unit 50 is rotated to the position marked "Check 2," the worker can determine that the IGBT 24 is short-circuited.

[0075] [1-5.Effects] In this embodiment, if the inverter circuit 18 fails, an operator can easily check the conduction state (i.e., whether they are normal or short-circuited) of the IGBT 24 and the diode 34 by operating the switching unit 50 based on the lighting state (on or off) of the light-emitting element 60.

[0076] (Embodiment 2) [2-1. Circuit configuration of the first detection circuit] The circuit configuration of the first detection circuit 42A according to the second embodiment will be described with reference to Fig. 6. Fig. 6 is a diagram showing the circuit configuration of the first detection circuit 42A according to the second embodiment. Note that in the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and descriptions thereof will be omitted.

[0077] 6, the first detection circuit 42A has a first switch 52, a second switch 54, a third switch 56, and an AC power supply 66 (an example of a power supply). The first detection circuit 42A further has, as notification elements, a first light-emitting element 68, a second light-emitting element 70, a third light-emitting element 72, a fourth light-emitting element 74, a first diode 76, a second diode 78, a third diode 80, and a fourth diode 82.

[0078] One terminal of the first switch 52 is electrically connected to the anode of the diode 34. The other terminal of the first switch 52 is electrically connected to the other pole of the AC power supply 66 via the first light-emitting element 68, the second light-emitting element 70, the first diode 76, and the second diode 78.

[0079] One terminal of the second switch 54 is electrically connected to the emitter terminal 24e of the IGBT 24. The other terminal of the second switch 54 is electrically connected to the other pole of the AC power supply 66 via the third light-emitting element 72, the fourth light-emitting element 74, the third diode 80, and the fourth diode 82.

[0080] The third switch 56 is electrically connected between a connection point 62 of the IGBT 24 and the diode 34 and an AC power supply 66. Specifically, one terminal of the third switch 56 is electrically connected to the connection point 62 between the collector terminal 24c of the IGBT 24 and the cathode of the diode 34. The other terminal of the third switch 56 is electrically connected to one pole of the AC power supply 66.

[0081] The AC power supply 66 is a power supply for supplying AC power. One pole of the AC power supply 66 is electrically connected to the other terminal of the third switch 56. The other pole of the AC power supply 66 is electrically connected to the other terminal of the first switch 52 via a first light-emitting element 68, a second light-emitting element 70, a first diode 76, and a second diode 78. The other pole of the AC power supply 66 is electrically connected to the other terminal of the second switch 54 via a third light-emitting element 72, a fourth light-emitting element 74, a third diode 80, and a fourth diode 82.

[0082] The first light-emitting element 68 and the second light-emitting element 70 are elements, such as light-emitting diodes, for notifying of a short circuit or an open circuit of the diode 34. The first light-emitting element 68 and the second light-emitting element 70 are electrically connected in parallel between the anode of the diode 34 and the other pole of the AC power supply 66.

[0083] The first diode 76 is electrically connected in series to the first light-emitting element 68. Specifically, the anode of the first diode 76 is electrically connected to one terminal of the first light-emitting element 68. In addition, the cathode of the first diode 76 is electrically connected to the other terminal of the first switch 52.

[0084] The second diode 78 is electrically connected in series to the second light-emitting element 70. Specifically, the anode of the second diode 78 is electrically connected to one terminal of the second light-emitting element 70. In addition, the cathode of the second diode 78 is electrically connected to the other pole of the AC power supply 66.

[0085] The third light-emitting element 72 and the fourth light-emitting element 74 are elements, such as light-emitting diodes, for notifying of a short circuit or an open circuit of the IGBT 24. The third light-emitting element 72 and the fourth light-emitting element 74 are electrically connected in parallel between the emitter terminal 24e of the IGBT 24 and the other pole of the AC power supply 66.

[0086] The third diode 80 is electrically connected in series to the third light-emitting element 72. Specifically, the anode of the third diode 80 is electrically connected to one terminal of the third light-emitting element 72. In addition, the cathode of the third diode 80 is electrically connected to the other terminal of the second switch 54.

[0087] The fourth diode 82 is electrically connected in series to the fourth light-emitting element 74. Specifically, the anode of the fourth diode 82 is electrically connected to one terminal of the fourth light-emitting element 74. In addition, the cathode of the fourth diode 82 is electrically connected to the other pole of the AC power supply 66.

[0088] [2-2. Operation of the first detection circuit] The operation of the first detection circuit 42A will be described with reference to Figures 7 to 9. Figures 7 to 9 are diagrams for explaining the operation of the first detection circuit 42A according to the second embodiment.

[0089] First, the operation of the first detection circuit 42A when the IGBT 24 and the diode 34 are both normal (i.e., neither short-circuited nor open), will be described with reference to Fig. 7. In this case, it is assumed that there is no electrical continuity between the collector terminal 24c and the emitter terminal 24e of the IGBT 24.

[0090] For example, when an operator rotates the switching unit 50 (see FIG. 2) to the position marked "check," the switching unit 50 simultaneously turns on the first switch 52, the second switch 54, and the third switch 56.

[0091] 7(a), during a period when one pole of the AC power supply 66 is switched to a cathode and the other pole to an anode, current from the AC power supply 66 flows through the first light-emitting element 68, the first diode 76, the first switch 52, the diode 34, and the third switch 56. As a result, current flows through the first light-emitting element 68, causing the first light-emitting element 68 to light up. Note that the current from the AC power supply 66 does not flow through the second diode 78 in the opposite direction, and therefore no current flows through the second light-emitting element 70 electrically connected in series with the second diode 78, and the second light-emitting element 70 remains unlit.

[0092] Furthermore, current from the AC power supply 66 flows through the third light-emitting element 72, the third diode 80, the second switch 54, the reverse conducting diode 36, and the third switch 56. As a result, current flows through the third light-emitting element 72, causing the third light-emitting element 72 to light up. Note that the current from the AC power supply 66 does not flow through the fourth diode 82 in the reverse direction, and therefore no current flows through the fourth light-emitting element 74 electrically connected in series with the fourth diode 82, and the fourth light-emitting element 74 remains unlit.

[0093] 7(b), during the period when one pole of the AC power supply 66 is switched to the anode and the other pole to the cathode, the current from the AC power supply 66 does not flow through the reverse diode 34, nor does it flow through the non-conducting IGBT 24. Therefore, no current flows through any of the first light-emitting element 68, the second light-emitting element 70, the third light-emitting element 72, and the fourth light-emitting element 74, and the first light-emitting element 68, the second light-emitting element 70, the third light-emitting element 72, and the fourth light-emitting element 74 are all turned off.

[0094] In this way, when an operator rotates the switching unit 50 to the position marked "check," the first light-emitting element 68 and the third light-emitting element 72 repeatedly flash, and the second light-emitting element 70 and the fourth light-emitting element 74 remain off, the operator can determine that both the IGBT 24 and the diode 34 are normal.

[0095] Next, the operation of the first detection circuit 42A when both the IGBT 24 and the diode 34 are short-circuited will be described with reference to Fig. 8. Note that the operation of the first detection circuit 42A when the reverse conducting diode 36 is short-circuited is the same as the operation of the first detection circuit 42A when the IGBT 24 is short-circuited, and therefore a description thereof will be omitted.

[0096] For example, when an operator or the like rotates the switching unit 50 to a position marked "check," the switching unit 50 simultaneously turns on the first switch 52, the second switch 54, and the third switch 56.

[0097] 8(a), during a period when one pole of the AC power supply 66 is switched to a cathode and the other pole to an anode, current from the AC power supply 66 flows through the first light-emitting element 68, the first diode 76, the first switch 52, the short-circuited diode 34, and the third switch 56. As a result, current flows through the first light-emitting element 68, causing the first light-emitting element 68 to light up. Note that the current from the AC power supply 66 does not flow through the second diode 78 in the opposite direction, and therefore no current flows through the second light-emitting element 70 electrically connected in series with the second diode 78, and the second light-emitting element 70 remains unlit.

[0098] Furthermore, current from the AC power supply 66 flows through the third light-emitting element 72, the third diode 80, the second switch 54, the short-circuited IGBT 24, and the third switch 56. As a result, current flows through the third light-emitting element 72, causing the third light-emitting element 72 to light up. Note that the current from the AC power supply 66 does not flow through the fourth diode 82 in the opposite direction, and therefore no current flows through the fourth light-emitting element 74 electrically connected in series with the fourth diode 82, and the fourth light-emitting element 74 remains unlit.

[0099] 8(b), during the period when one pole of the AC power supply 66 is switched to the anode and the other pole to the cathode, current from the AC power supply 66 flows through the third switch 56, the short-circuited diode 34, the first switch 52, the second light-emitting element 70, and the second diode 78, turning on the second light-emitting element 70. Note that the current from the AC power supply 66 does not flow through the first diode 76 in the reverse direction, and therefore no current flows through the first light-emitting element 68 electrically connected in series to the first diode 76, and the first light-emitting element 68 turns off.

[0100] Furthermore, current from the AC power supply 66 flows through the third switch 56, the short-circuited IGBT 24, the second switch 54, the fourth light-emitting element 74, and the fourth diode 82, turning on the fourth light-emitting element 74. Note that the current from the AC power supply 66 does not flow through the third diode 80 in the reverse direction, and therefore no current flows through the third light-emitting element 72 electrically connected in series to the third diode 80, and the third light-emitting element 72 turns off.

[0101] In this way, when an operator rotates the switching unit 50 to the position marked "check," and the first light-emitting element 68, the second light-emitting element 70, the third light-emitting element 72, and the fourth light-emitting element 74 all repeatedly flash, the operator can determine that the IGBT 24 and the diode 34 are both short-circuited.

[0102] Furthermore, when an operator rotates the switching unit 50 to the position marked "check," if (a) the first light-emitting element 68 repeatedly flashes, (b) the second light-emitting element 70 repeatedly flashes, (b) the third light-emitting element 72 repeatedly flashes, and (c) the fourth light-emitting element 74 remains off, the operator can determine that the diode 34 is short-circuited and that the IGBT 24 is normal.

[0103] Furthermore, when an operator rotates the switching unit 50 to the position marked "check," if (a) the first light-emitting element 68 repeatedly flashes, and (b) the second light-emitting element 70 remains off, and (c) the third light-emitting element 72 repeatedly flashes, and (d) the fourth light-emitting element 74 repeatedly flashes, the operator can determine that the IGBT 24 is short-circuited and the diode 34 is normal.

[0104] Next, the operation of the first detection circuit 42A when both the IGBT 24 and the diode 34 are open will be described with reference to Fig. 9. It is assumed that the IGBT 24 is open together with the reverse conducting diode 36.

[0105] For example, when an operator or the like rotates the switching unit 50 to a position marked "check," the switching unit 50 simultaneously turns on the first switch 52, the second switch 54, and the third switch 56.

[0106] 9(a), during the period when one pole of the AC power supply 66 is switched to the cathode and the other pole to the anode, current from the AC power supply 66 does not flow through the open-circuited diode 34 or IGBT 24. Therefore, no current flows through any of the first light-emitting element 68, the second light-emitting element 70, the third light-emitting element 72, and the fourth light-emitting element 74, and all of the first light-emitting element 68, the second light-emitting element 70, the third light-emitting element 72, and the fourth light-emitting element 74 are turned off.

[0107] 9(b), during the period when one pole of the AC power supply 66 is switched to the anode and the other pole to the cathode, no current from the AC power supply 66 flows through the open-circuited diode 34 or IGBT 24. Therefore, no current flows through any of the first light-emitting element 68, the second light-emitting element 70, the third light-emitting element 72, and the fourth light-emitting element 74, and all of the first light-emitting element 68, the second light-emitting element 70, the third light-emitting element 72, and the fourth light-emitting element 74 remain turned off.

[0108] In this way, when an operator rotates the switching unit 50 to the position marked "check," if the first light-emitting element 68, the second light-emitting element 70, the third light-emitting element 72, and the fourth light-emitting element 74 all remain off, the operator can determine that the IGBT 24 and the diode 34 are both open-circuited.

[0109] Furthermore, if an operator rotates the switching unit 50 to the position marked "check" and only the first light-emitting element 68 and the second light-emitting element 70 remain off, the operator can determine that the diode 34 is broken.

[0110] Furthermore, when an operator rotates the switching unit 50 to the position marked "check," if only the third light-emitting element 72 and the fourth light-emitting element 74 remain off, the operator can determine that the IGBT 24 is broken.

[0111] As in the first embodiment, for example, when an operator or the like rotates the switching unit 50 to a position marked "Check 1," the switching unit 50 may simultaneously turn on the first switch 52 and the third switch 56 and turn off the second switch 54. Alternatively, for example, when an operator or the like rotates the switching unit 50 to a position marked "Check 2," the switching unit 50 may simultaneously turn on the second switch 54 and the third switch 56 and turn off the first switch 52.

[0112] [2-3. Effects] In this embodiment, if the inverter circuit 18 (see Figure 1) fails, an operator or the like can easily check the conduction state of the IGBT 24 and the diode 34 (i.e., whether they are normal, short-circuited, or open) by operating the switching unit 50 based on the lighting state (flashing or off) of the first light-emitting element 68, the second light-emitting element 70, the third light-emitting element 72, and the fourth light-emitting element 74.

[0113] (Embodiment 3) The circuit configuration of the first detection circuit 42B according to the third embodiment will be described with reference to Fig. 10. Fig. 10 is a diagram showing the circuit configuration of the first detection circuit 42B according to the third embodiment. Note that in the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and descriptions thereof will be omitted.

[0114] 10, the first detection circuit 42B has a first switch 52, a second switch 54, a third switch 56, a DC power supply 58, and a relay coil 84 (an example of an alarm element). That is, the first detection circuit 42B has the relay coil 84 instead of the light-emitting element 60 of the first detection circuit 42 according to the first embodiment.

[0115] The relay coil 84 is an element for notifying of a short circuit of the IGBT 24 and the diode 34. The relay coil 84 is electrically connected between a connection point 62 of the IGBT 24 and the diode 34 and the anode of the DC power supply 58. Specifically, one terminal of the relay coil 84 is electrically connected to the connection point 62 between the collector terminal 24c of the IGBT 24 and the cathode of the diode 34 via the third switch 56. The other terminal of the relay coil 84 is electrically connected to the anode of the DC power supply 58. When a current flows through the relay coil 84, a signal is output from the relay coil 84.

[0116] The signal output from the relay coil 84 is transmitted to an external device such as a PLC (Programmable Logic Controller). Upon receiving the signal, the external device notifies an operator or the like that the inverter circuit 18 (see FIG. 1) has failed.

[0117] If the IGBT 24 and the diode 34 are both normal, for example, when an operator or the like rotates the switching unit 50 (see FIG. 2) to the position marked "check," the switching unit 50 simultaneously turns on the first switch 52, the second switch 54, and the third switch 56. In this state, current from the DC power supply 58 does not flow through the diode 34 in the reverse direction, and does not flow through the non-conducting IGBT 24. Therefore, no current flows through the relay coil 84, and no signal is output from the relay coil 84.

[0118] In this way, if an operator rotates the switching unit 50 to the position marked "check" and no signal is output from the relay coil 84, the operator can determine that both the IGBT 24 and the diode 34 are normal.

[0119] On the other hand, if at least one of the IGBT 24 and the diode 34 is short-circuited, for example, when an operator or the like rotates the switching unit 50 to the position marked "check," the switching unit 50 simultaneously turns on the first switch 52, the second switch 54, and the third switch 56. In this state, current from the DC power supply 58 flows through at least one of the IGBT 24 and the diode 34. As a result, current flows through the relay coil 84, and a signal is output from the relay coil 84.

[0120] In this way, when an operator rotates the switching unit 50 to the position marked "check" and a signal is output from the relay coil 84, the operator can determine that at least one of the IGBT 24 and the diode 34 is short-circuited.

[0121] Therefore, in this embodiment as well, if the inverter circuit 18 fails, an operator or the like can easily check the continuity state of the IGBT 24 and the diode 34 (i.e., whether they are normal or short-circuited) by operating the switching unit 50 based on whether or not a signal is output from the relay coil 84.

[0122] As in the first embodiment, for example, when an operator or the like rotates the switching unit 50 to a position marked "Check 1," the switching unit 50 may simultaneously turn on the first switch 52 and the third switch 56 and turn off the second switch 54. Alternatively, for example, when an operator or the like rotates the switching unit 50 to a position marked "Check 2," the switching unit 50 may simultaneously turn on the second switch 54 and the third switch 56 and turn off the first switch 52.

[0123] Furthermore, the operation of the first detection circuit 42B when the reverse conducting diode 36 is short-circuited is similar to the operation of the first detection circuit 42B when the IGBT 24 is short-circuited, and therefore a description thereof will be omitted.

[0124] (Variations, etc.) Although the power conversion device according to one or more aspects of the present invention has been described based on the above-mentioned embodiments, the present invention is not limited to the above-mentioned embodiments. As long as it does not deviate from the spirit of the present invention, various modifications conceivable by a person skilled in the art to the present embodiments, or configurations constructed by combining components of different embodiments, may also be included within the scope of one or more aspects of the present invention.

[0125] In the above-described embodiments, the power conversion device 6 is mounted on the induction heating device 2, but the present invention is not limited to this and may be mounted on various devices such as industrial machinery or home appliances.

[0126] In addition, in each of the above-described embodiments, the continuity states of the IGBT 24 and the diode 34 are inspected by manually operating the switching unit 50 by an operator or the like, but this is not limiting. For example, the continuity states of the IGBT 24 and the diode 34 may be inspected automatically by remote control while the inverter circuit 18 is on standby, or the continuity states of the IGBT 24 and the diode 34 may be inspected automatically when the main power supply of the induction heating device 2 is turned on.

[0127] Another aspect of the present invention may be not only such a power conversion device, but also a method in which characteristic components included in the power conversion device are included as steps. Another aspect of the present invention may be a computer program that causes a computer to execute each characteristic step included in the method. Another aspect of the present invention may be a computer-readable non-transitory recording medium on which such a computer program is recorded. [Industrial Applicability]

[0128] The power conversion device according to the present invention can be mounted on, for example, an induction heating device for high-frequency hardening of metal parts. [Explanation of symbols]

[0129] 2 Induction heating device 4 Object to be heated 6 Power conversion equipment 8 matching circuit 10 induction coil 12 Rectifier circuit 14,16 Choke coil 18 Inverter circuit 20 Thyristor 22 Commercial power supply 24 IGBT 24c Collector terminal 24e Emitter terminal 24g Gate terminal 26 First switching section 28 Second switching section 30 Third Switching Section 32 Fourth Switching Section 34 Diode 36 Reverse conducting diode 38 Capacitors 40 Matching transformer 42, 42A, 42B First detection circuit 44 Second detection circuit 46 Third detection circuit 48 Fourth detection circuit 50 Switching section 52 First Switch 54 Second Switch 56 The Third Switch 58 DC power supply 60 Light-emitting element 62,64 connection points 66 AC power supply 68 First light-emitting element 70 Second light-emitting element 72 Third light-emitting element 74 Fourth light-emitting element 76 First Diode 78 Second Diode 80 Third Diode 82 Fourth Diode 84 Relay Coil

Claims

1. a switching element having a first terminal, a second terminal, and a third terminal, and in which conduction between the first terminal and the second terminal is controlled in accordance with a voltage or a current input to the third terminal; a diode having one terminal electrically connected to the first terminal of the switching element; a first switch having one terminal electrically connected to the other terminal of the diode; a second switch having one terminal electrically connected to the second terminal of the switching element; a third switch having one terminal electrically connected to a connection point between the first terminal of the switching element and the one terminal of the diode; a power supply for supplying power, one pole of which is electrically connected to the other terminal of the third switch, and the other pole of which is electrically connected to each of the other terminals of the first switch and the second switch; an alarm element for notifying a short circuit or an open circuit of the switching element and the diode, the alarm element being electrically connected to at least one of: (i) between the other terminal of the diode and the other pole of the power supply; (ii) between the second terminal of the switching element and the other pole of the power supply; and (iii) between the connection point and the one pole of the power supply; a switching unit that switches on and off each of the first switch, the second switch, and the third switch. Power conversion device.

2. the power supply is a DC power supply for supplying DC power, The notification element is a light-emitting element electrically connected between the connection point and the one pole of the power source. The power conversion device according to claim 1 .

3. the power supply is an AC power supply for supplying AC power, The notification element is a first light-emitting element and a second light-emitting element electrically connected in parallel between the other terminal of the diode and the other pole of the power supply; a third light-emitting element and a fourth light-emitting element electrically connected in parallel between the second terminal of the switching element and the other pole of the power supply; a first diode electrically connected in series to the first light emitting element; a second diode electrically connected in series to the second light emitting element; a third diode electrically connected in series to the third light emitting element; a fourth diode electrically connected in series to the fourth light-emitting element. The power conversion device according to claim 1 .

4. the power supply is a DC power supply for supplying DC power, The notification element is a relay coil electrically connected between the connection point and the one pole of the power supply. The power conversion device according to claim 1 .

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