semiconductor device

Abstract

A semiconductor device used in a three-point voltage type inverter, comprising: a first IGBT (11) to which a diode (12) is connected in antiparallel and which has a collector connected to a positive terminal (17; C1) of a DC circuit; a second IGBT (13) to which a diode (14) is connected in antiparallel and which has an emitter connected to a negative terminal (19; E2) of the DC circuit; and an AC switch (15) connected between a connection point between an emitter of the first IGBT (11) and a collector of the second IGBT (13) from a neutral terminal (18; M) between the positive terminal (17; C1) and the negative terminal (19; E2) of the DC circuit, wherein the first IGBT (11), the second IGBT (13) and the AC switch (15) are housed in a housing, the AC switch (15) is formed by connecting a collector of a third IGBT (41), to which a diode (43) is connected in antiparallel, and a collector of a fourth IGBT (42), to which a diode (44) is connected in antiparallel, an intermediate connection (5) is provided between the collector of the third IGBT (41) and the collector of the fourth IGBT (42), wherein each of the first to fourth IGBTs (11, 13, 41, 42) has a terminal of an auxiliary emitter (6a; 6b; 6c), and wherein the collector of the first IGBT (11), the emitter of the second IGBT (13) and the neutral terminal (M) are main terminals, and the intermediate terminal (5) and the gates and the auxiliary emitters of the first to fourth IGBTs (11, 13, 41, 42) are terminals that are smaller than the main terminals, and wherein the intermediate terminal (5) is arranged below the main terminal and the terminals of the gates and the auxiliary emitters.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention

[0001] The present invention relates to a semiconductor device of a three-point power conversion circuit used for a three-point inverter or a resonance inverter. 2. Description of related technology

[0002] Fig. Figure 4 shows a circuit example of a three-level three-phase inverter that converts direct current (DC) to alternating current (AC) according to the related art. DC power supplies 1 and 2 are connected in series, in which a positive potential is P, a negative potential is N, and a neutral potential is M. When a DC power supply is configured as an AC power supply system, it can generally be realized using a structure in which a diode rectifier (not shown) is used to full-wave rectify the AC current and a large-capacity electrolytic capacitor is used to smooth the rectified current.

[0003] Series circuits corresponding to three phases and configured by connecting IGBTs to which diodes are connected in series in antiparallel are connected between the positive potential P and the negative potential N. That is, a series circuit 60 for a U phase is configured by connecting in series an upper arm including an IGBT 11 and a diode 12 connected in antiparallel to the IGBT 11, and a lower arm including an IGBT 13 and a diode 14 connected in antiparallel to the IGBT 13. A series-connected circuit 61 for a V phase is configured by connecting in series an upper arm including an IGBT 21 and a diode 22 connected in antiparallel to the IGBT 21, and a lower arm including an IGBT 23 and a diode 24 connected in antiparallel to the IGBT 23.A series-connected circuit 62 for a W phase is configured by connecting in series an upper arm including an IGBT 31 and a diode 32 connected in antiparallel to the IGBT 31, and a lower arm including an IGBT 33 and a diode 34 connected in antiparallel to the IGBT 33.

[0004] An AC switch configured by connecting IGBTs to which diodes are connected in antiparallel in series is connected between a series connection point between the upper arm and the lower arm of the series-connected circuit for each phase and a neutral DC potential M. That is, an AC circuit in which the emitter of a semiconductor device 63 including an IGBT 81 and a diode 82 connected in antiparallel to the IGBT 81 is connected to the emitter of a semiconductor device 64 including an IGBT 83 and a diode 84 connected in antiparallel to the IGBT 83 is connected between the series connection point of the series-connected circuit 60 for the U phase and the neutral point M of the DC power supply.In addition, an AC circuit in which the emitter of a semiconductor device 65 including an IGBT 85 and a diode 86 connected in anti-parallel with the IGBT 85 is connected to the emitter of a semiconductor device 66 including an IGBT 87 and a diode 88 connected in anti-parallel with the IGBT 87 is connected between the series connection point of the series-connected circuit 61 for the V phase and the neutral point M of the DC power supply. An AC circuit in which the emitter of a semiconductor device 67 including an IGBT 89 and a diode 90 connected in anti-parallel with the IGBT 89 is connected to the emitter of a semiconductor device 68 including an IGBT 91 and a diode 92 connected in anti-parallel with the IGBT 91 is connected between the series connection point of the series-connected circuit 62 for the W phase and the neutral point M of the DC power supply.The series connection points of the series-connected circuits 60, 61, and 62 are AC outputs of the U-phase, the V-phase, and the W-phase, and are connected to a load 74 through choke coils 71, 72, and 73, each serving as a filter.

[0005] In the three-phase circuit configuration, the series connection points of the series-connected circuits 60, 61, and 62 can output the positive potential P, the negative potential N, and the neutral potential M, respectively. Therefore, a three-level inverter output is obtained. The three-phase circuit configuration is characterized by outputting an AC voltage with three voltage levels and a low number of harmonic components compared to a two-level inverter. It is possible to reduce the sizes of the output filters 71 to 73.

[0006] A semiconductor device has been manufactured in which the circuits comprising three Fig. 4 are integrated into a module, or a semiconductor device in which a circuit corresponding to a phase is integrated into a module. When a circuit corresponding to a phase is integrated into a module to form a semiconductor device, the semiconductor device can be used for a single phase. In addition, multiple semiconductor devices can be used to form the circuit shown in Fig. 4 to form the three-phase inverter shown. Fig. 5A and Fig. 5B show a semiconductor device that uses the Fig. 4, which corresponds to one phase. Fig. 5A shows the external appearance of a semiconductor module and Fig. Figure 5B shows the internal circuit structure. The semiconductor module includes IGBTs 11 and 13, diodes 12 and 14, and an AC switch 15 as semiconductor elements. Terminal 17 is a C1 terminal connected to the positive potential P of the DC power supply. Terminal 18 is an M terminal connected to the neutral potential M of the DC power supply. Terminal 19 is an E2 terminal connected to the negative potential N of the DC power supply. Terminal 16 is an E1C2 terminal connected to a load. Fig. 5A shows a metal base substrate 3, which allows a semiconductor element or a wiring element to be provided thereon so as to be insulated, and an insulating casing 4 of the module. The base substrate 3 also has a function of transferring heat generated from the interior of the module to a fan. For example, any of the following substrates can be used as the base substrate 3: an aluminum insulating substrate having an insulating layer formed on an aluminum plate; and a substrate in which, for example, an alumina or aluminum nitride ceramic substrate with a metal film, such as a copper film, bonded thereto is mounted on a copper or alloy plate. In recent years, a ceramic substrate to which a metal film is bonded without a copper or alloy plate has been used as the base substrate 3.In all substrates, metal is exposed from the back of the base substrate 3, and the semiconductor elements provided in the insulating housing 4 are insulated from the metal by an insulator. In . Fig. 5A, the terminals C1, M and E2 are arranged in a row on the module. Fig. 6A to 6C show examples of the structure of the Fig. 5 used AC switch 15. In the Fig. 6A and Fig. In the examples shown in Figure 6B, since a general IGBT has a very low reverse blocking voltage capability, the IGBT and the diode are connected in series to ensure reverse voltage resistance. Fig. Figure 6A shows the circuit structure of an AC switch formed by connecting the emitter of an IGBT 41, to which a diode 43 is connected in antiparallel, and the emitter of an IGBT 42, to which a diode 44 is connected in antiparallel. When a current flows from a terminal K to a terminal L, the IGBT 41 is turned on, and the current flows through a path from the IGBT 41 to the diode 44. When a current flows from the terminal L to the terminal K, the IGBT 42 is turned on, and the current flows through a path from the IGBT 42 to the diode 43.

[0007] Fig. Figure 6B shows the circuit structure of an AC switch formed by connecting the collector of IGBT 41, to which diode 43 is connected in antiparallel, and the collector of IGBT 42, to which diode 44 is connected in antiparallel. When a current flows from terminal K to terminal L, IGBT 42 is turned on, and the current flows through a path from diode 43 to IGBT 42. When a current flows from terminal L to terminal K, IGBT 41 is turned on, and the current flows through a path from diode 44 to IGBT 41.

[0008] Fig. Figure 6C shows the structure of an AC switch formed by connecting reverse-blocking IGBTs 45 and 46, which are IGBTs with reverse blocking capability, in antiparallel to each other. When a current flows from terminal K to terminal L, reverse-blocking IGBT 45 turns on. When a current flows from terminal L to terminal K, reverse-blocking IGBT 46 turns on (see, for example, JP-A-2008-193779).

[0009] A circuit in which the IGBTs are connected in antiparallel, or a circuit in which the reverse-blocking IGBTs are connected in antiparallel, is given as an example of the AC switch. However, a combination of a diode bridge circuit and IGBTs or other types of semiconductor switching elements can be used.

[0010] The one in the Fig. 5A and Fig. 5B using the circuit structure shown in Fig. 6A, in which the emitters of the IGBTs are connected to each other as the AC switch 15, requires a total of four driving power supplies, that is, two driving power supplies for driving the IGBT 11 and the IGBT 13 and two driving power supplies for driving the IGBT 41 and the IGBT 42.

[0011] In the Fig. 5A and Fig. 5B using the circuit configuration shown in Fig. 6B, in which the collectors of the IGBTs are connected to each other as the AC switch 15, the emitter of the IGBT 11 is connected to the emitter of the IGBT 42, and the emitter potentials are equal to each other. Therefore, the IGBT 11 and the IGBT 42 can share one driving power supply, and the number of driving power supplies for driving the IGBTs can be reduced to three, that is, one driving power supply for driving the IGBT 11 and the IGBT 42, and two driving power supplies for driving the IGBT 13 and the IGBT 41. Since the number of driving IGBTs is reduced, the size and cost of an inverter can be reduced.

[0012] However, the Fig. 5A and Fig. 5B using the circuit configuration shown in Fig. 6B, in which the collectors of the IGBTs are connected to each other as the AC switch 15, the number of driving power supplies is reduced, but the AC switch 15 has the following problems.

[0013] That is, in the case of a semiconductor device in which the Fig. 4, corresponding to three phases, are integrated in one module, or a semiconductor device in which a circuit corresponding to one phase is integrated in one module, the insulation test of such a semiconductor is performed upon completion of production. In the insulation test, main terminals of the module and other terminals, such as control terminals, projecting to the outside of the module are connected to one terminal of an AC power supply, and metal exposed from the back of the base substrate 3 is connected to the other terminal of the AC power supply. Then, a voltage of, for example, 3.0 kV is applied to test the electrical insulation between the semiconductor element in the module and the metal on the back of the base substrate 3. The insulation test will be described with reference to Fig. 7A and Fig. 7B. Fig. 7A and Fig. 7B show an example in which a ceramic substrate 7 on a copper base 8 is used as the base substrate. As in Fig. 7A, when an AC power supply 9 supplies a current I and a positive voltage is applied to the terminal, a charge is stored between a circuit pattern (not shown) on the ceramic substrate 7 (shown by a dotted line) and the copper base 8 on the back of the ceramic substrate 7. In this case, the following three charges are stored between the circuit pattern of the ceramic substrate 7 and the copper base 8 in the AC switch: a charge Q1 generated by a charging current I 11 , a part of a current I1 is stored in a capacitive component C1 between the emitter of the IGBT 41 and the copper base; a charge Q2, which is supplied by a charging current I 21, a portion of a current I2, is stored in a capacitive component C2 between the emitter of the IGBT 42 and the copper base; and a charge Q3, which is stored in a capacitive component C3 between the cathode and the copper base by a charging current I3 + I4, which is generated by a current I3 flowing through the diode 43 and a current I4 flowing through the diode 44.

[0014] Then, as in Fig. As shown in Figure 7B, when the voltage applied by the AC power supply 9 is reduced, the charge stored in the ceramic substrate 7 is discharged. At this time, the discharge currents I 11 and I 21, generated by the charges Q1 and Q2 stored in the capacitive elements C1 and C2 between the emitters of the IGBTs 41 and 42 and the copper base, to the AC power supply. However, the discharge current I3 + I4 generated by the charge Q3 stored in the capacitive element C3 between the collector and the copper base is prevented from flowing by the diode and remains without being discharged. Therefore, there is a large potential difference between the collector and the emitter of the IGBTs 41 and 42 due to the charge Q3 remaining in the capacitive element C3 between the collector and the copper base. Therefore, the IGBTs 41 and 42 are likely to be damaged.

[0015] In the Fig. 7A and Fig. In the AC switch shown in Figure 7B, auxiliary emitters 6c and 6d are provided at both ends of the AC switch because the collector is shared between the IGBT 41 and the IGBT 42. Therefore, when the auxiliary emitters 6c and 6d are also used to evaluate a single element, the overall characteristics of the IGBTs and diodes, such as the IGBT 41 and the diode 44, and the IGBT 42 and the diode 43, are measured. Therefore, it is difficult to evaluate the individual element.

[0016] Document US 2010 / 0 039 843 A1 discloses a series circuit of IGBTs and an AC switch contained within a housing. The series circuit is connected between the positive and negative poles of a DC power source, and the AC switch is connected between the neutral point of the DC power source and a series connection point between the IGBTs. Straight conductors can be used to connect the terminals of the housing to the DC power source.

[0017] JP 2003-333826 A discloses a power semiconductor module in which semiconductor devices equipped with a pair of diodes capable of self-arc extinguishing are connected in reverse parallel. To transmit power in both directions, an anode terminal of the diode and an output terminal of the semiconductor device are connected to a first terminal and a second terminal of the power semiconductor module. All cathode terminals of the diode and the input terminals of the semiconductor device are connected to a third terminal. SUMMARY OF THE INVENTION

[0018] The invention has been made to solve the above-mentioned problems of the related art, and it is an object of the invention to prevent damage to a semiconductor device during insulation test and to evaluate elements in the semiconductor device individually.

[0019] Embodiments of the present invention are defined in the independent claims. Additional features of embodiments of the invention are set forth in the dependent claims. In the following, portions of the description and drawings relating to prior embodiments, which do not necessarily include all features for implementing embodiments of the claimed invention, are not presented as embodiments of the invention, but as examples useful for understanding embodiments of the invention. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a circuit diagram illustrating a semiconductor device according to a first embodiment; Fig. 2A and Fig. 2B are circuit diagrams illustrating the test state of the semiconductor device according to the first embodiment; Fig. 3 is a side view illustrating the semiconductor device according to the first embodiment; Fig. 4 is a circuit diagram illustrating a three-level inverter according to the related art; Fig. 5A and Fig. 5B are diagrams illustrating the structure of a semiconductor device according to the related art; Fig. Fig. 5A is a perspective view illustrating the external appearance of the semiconductor device, and Fig. 5B is a circuit diagram illustrating the semiconductor device. Fig. 6A to 6C are circuit diagrams illustrating an AC switch according to the related art; and Fig. 7A and Fig. 7B are circuit diagrams illustrating the insulation test according to the related art. DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Semiconductor devices according to exemplary embodiments of the invention will be described in detail below with reference to the accompanying drawings. In the following embodiments and drawings, like components are designated by like reference numerals, and their descriptions will not be repeated. (First embodiment)

[0021] Fig. 1 is a circuit diagram illustrating a semiconductor device according to a first embodiment, and corresponds Fig. 5B. The Fig. 1 is different from the semiconductor device shown in Fig. 5B, by configuring an AC switch 15 by connecting a collector of an IGBT 41 to which a diode 43 is connected in antiparallel and a collector of an IGBT 42 to which a diode 44 is connected in antiparallel, and providing an intermediate terminal 5 between the collector of the IGBT 41 and the collector of the IGBT 42. When a current flows from a terminal M to a terminal E1C2, the IGBT 42 is turned on, and the current flows through a path from the diode 43 to the IGBT 42. When a current flows from the terminal E1C2 to the terminal M, the IGBT 41 is turned on, and the current flows through a path from the diode 44 to the IGBT 41. A process for the current to flow is the same as that in the circuit diagram of the Fig. 5B. An IGBT 11, an IGBT 13 and the IGBT 41 have the auxiliary emitters 6a, 6b and 6c, respectively. The auxiliary emitter of the IGBT 42 is not provided, since the auxiliary emitter 6a of the IGBT 11 also serves as the auxiliary emitter of the IGBT 42. A semiconductor device can be formed by Fig. 1 is integrated into a module corresponding to one phase. In addition, a semiconductor device can be formed by integrating a plurality of Fig. 1, each corresponding to one phase, can be integrated, for example, into a module corresponding to three phases.

[0022] Next, an insulation test performed upon completion of the semiconductor device is described. Fig. 2A and Fig. 2B are circuit diagrams illustrating a portion of the test for checking the electrical insulation between a semiconductor element in a module and the metal on the back of a base substrate 3. In the test, the main terminal of the module and terminals, such as control terminals, that protrude outside the module are connected to one terminal of an AC power supply 9, and the metal exposed on the back of the base substrate 3 is connected to the other terminal of the AC power supply. Then, a voltage of, for example, 3.0 kV is applied to check the electrical insulation between the semiconductor element in the module and the metal on the back of the base substrate. Fig. 2A and Fig. 2B show only the IGBT 41, the IGBT 42, the diode 43 and the diode 44, which form the AC switch in the Fig. 1. However, the test is equally performed on the IGBT 11, the IGBT 13, the diode 12 and the diode 14. The insulation test is carried out with reference to Fig. 2A and Fig. 2B. Fig. 2A and Fig. 2B show an example in which a ceramic substrate 7 on a copper base 8 is used as the base substrate. As in Fig. As shown in Figure 2A, when the AC power supply 9 supplies a current I and a positive voltage is applied to the terminal, a charge is stored between a circuit pattern (not shown) on the ceramic substrate 7 (indicated by a dotted line) and the copper base 8 on the back of the ceramic substrate 7. In this case, the following three charges are stored between the circuit pattern of the ceramic substrate 7 and the copper base 8. A charge Q1 generated by a charging current I 11, a part of a current I1, is stored in a capacitive component C1 between the emitter of the IGBT 41 and the copper base; a charge Q2, which is generated by a charging current I 21 , a portion of a current I2, stored in a capacitive component C2 between the emitter of the IGBT 42 and the copper base; and a charge Q3 stored in a capacitive component C2 between the cathode and the copper base by a charging current I3 + I4 + I5 obtained by a current I3 flowing through the diode 43, a current I4 flowing through the diode 44, and a current I5 flowing through the intermediate terminal 5.

[0023] Then, as in Fig. 2B, when the voltage applied by the AC power supply 9 is reduced, the charge stored in the ceramic substrate 7 is discharged. At this time, the discharge currents I 11 and I 21, generated by the charges Q1 and Q2 stored in the capacitive components C1 and C2 between the emitters of the IGBTs 41 and 42 and the copper base, flows to the AC power supply. In addition, the discharge current I3 + I4 + I5 generated by the charge Q3 stored in the capacitive component C3 between the collector and the copper base flows through the intermediate terminal 5 to the AC power supply. As such, the charge Q3 stored in the capacitive component C3 between the collector and the copper base is completely discharged. Therefore, there is no large potential gradient between the collector and the emitter of the IGBTs 41 and 42. As a result, damage to the IGBTs 41 and 42 is prevented.

[0024] Since in Fig. 1 The intermediate connection 5 is provided between the collector of the IGBT 41 and the collector of the IGBT 42, making it possible to individually measure the element properties of the IGBT 41, the diode 44, the IGBT 42, and the diode 43. Therefore, it is possible to evaluate the individual elements and determine the cause of a fault.

[0025] Fig. 3 is a cross-sectional view illustrating the state of the semiconductor device when the semiconductor device is used as an inverter. In Fig.3, a metal base substrate 3 allows a semiconductor element or a wiring element to be placed thereon so as to be insulated. The metal base substrate 3 also has the function of transferring heat generated from the interior to a fan. As the base substrate 3, for example, any of the following substrates can be used: an aluminum insulating substrate having an insulating layer formed on an aluminum plate; a substrate in which, for example, an alumina or aluminum nitride ceramic substrate to which a metal film, such as a copper film, is bonded is mounted on a copper or alloy plate; and a ceramic substrate to which a metal film is bonded without a copper or alloy plate.A U terminal 16, which is the E1C2 terminal serving as the main terminal for a U phase, an N terminal 19, which is the main terminal E2 at a negative potential N, an M terminal 18, which is the main terminal M at a neutral potential M, and a P terminal 17, which is the main terminal C1 at a positive potential P, are arranged in a line in this order on the top surface of an insulating case 4 of the module. The auxiliary emitter and gate terminals 20 are provided on one side of the P terminal 17 of the insulating case 4. A wiring substrate 10 is used to connect, for example, a control circuit. A bus bar or an electric wire other than the wiring substrate 10 can be used to connect the control circuit. The intermediate terminal 5 is arranged below the main terminal and terminal 20 on the other side of the insulating case 4.When the terminals of the semiconductor device are arranged in this way, the following effects are achieved. First, since the N terminal 19, the M terminal 18, and the P terminal 17 are arranged in this order, it is easy to connect capacitors between the N terminal 19 and the M terminal 18, and the M terminal 18 and the P terminal 17. Since the U terminal 16 is separated from the terminal 20, it is possible to reduce the influence of the main current flowing through the output terminal on the terminal 20. Since the intermediate terminal 5 is arranged below the main terminals and the terminal 20, it does not interfere with the connection in the wiring substrate 10. In addition, the main terminals, the terminal 20, and the intermediate terminal 5 satisfy an insulation distance from the ground defined by an insulation standard, and the terminal 20 and the intermediate terminal 5 are smaller than the main terminals.

[0026] As described above, the semiconductor device according to the embodiment of the invention is configured by integrating a series-connected circuit and an AC switch into one module. The series-connected circuit is formed by connecting two IGBTs to which diodes are connected in antiparallel in series. The AC switch is formed by connecting two IGBTs to which diodes are connected in antiparallel in series such that the two IGBTs share the collector. Therefore, the semiconductor device can be applied to, for example, a three-point inverter circuit, a three-point converter circuit, and a resonant circuit.

[0027] Features, components, and specific details of the structures of the above-described embodiments can be exchanged or combined to form further embodiments optimized for the respective application. To the extent that such modifications are readily apparent to a person skilled in the art, they are intended to be implicitly disclosed by the above description for the sake of brevity and conciseness of the present description, without explicitly detailing every possible combination.

Claims

[1] A semiconductor device used in a three-point voltage type inverter, comprising: a first IGBT (11) to which a diode (12) is connected in antiparallel and which has a collector connected to a positive terminal (17; C1) of a DC circuit; a second IGBT (13) to which a diode (14) is connected in antiparallel and which has an emitter connected to a negative terminal (19; E2) of the DC circuit; and an AC switch (15) connected between a connection point between an emitter of the first IGBT (11) and a collector of the second IGBT (13) from a neutral terminal (18; M) between the positive terminal (17; C1) and the negative terminal (19; E2) of the DC circuit, wherein the first IGBT (11), the second IGBT (13) and the AC switch (15) are housed in a housing, the AC switch (15) is formed by connecting a collector of a third IGBT (41), to which a diode (43) is connected in antiparallel, and a collector of a fourth IGBT (42), to which a diode (44) is connected in antiparallel, an intermediate connection (5) is provided between the collector of the third IGBT (41) and the collector of the fourth IGBT (42), wherein each of the first to fourth IGBTs (11, 13, 41, 42) has a terminal of an auxiliary emitter (6a; 6b; 6c), and wherein the collector of the first IGBT (11), the emitter of the second IGBT (13) and the neutral terminal (M) are main terminals, and the intermediate terminal (5) and the gates and the auxiliary emitters of the first to fourth IGBTs (11, 13, 41, 42) are terminals that are smaller than the main terminals, and wherein the intermediate terminal (5) is arranged below the main terminal and the terminals of the gates and the auxiliary emitters. [2] A semiconductor device according to claim 1, wherein the first to fourth IGBTs (11, 13, 41, 42), each of which has one of the diodes connected antiparallel to it, form a circuit corresponding to one phase, and several of the circuits, each corresponding to a phase, are housed in one housing. [3] A semiconductor device according to claim 1 or 2, wherein among the first to fourth IGBTs (11, 13, 41, 42), those IGBTs having the emitters of the same potential share the terminal of the auxiliary emitter.

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