Power conversion device

Abstract

Power conversion device (10) with: - a battery (12); - a first capacitor (28) connected in parallel to the battery (12); - a boost converter (14) connected to the battery (12) and the first capacitor (28); - a second capacitor (58) connected in parallel to the boost converter (14); - an inverter (16) connected in parallel to the boost converter (14) and the second capacitor (58); - a load (18) connected to the inverter (16); - a conductor of an electrical reference potential (22) connecting a negative terminal of the battery (12) to the first capacitor (28), the boost converter (14), the second capacitor (58), the inverter (16) and the load (18) in the order of the first capacitor (28), the boost converter (14), the second capacitor (58), the inverter (16) and the load (18); and - a bridging path (72) with which, in the event that a lower arm switching device (44) included in the boost converter (14) has a short-circuit fault, the conduction of an electrical reference potential (22) is interrupted at a first position between the negative terminal of the battery (12) and the first capacitor (28) and at a second position between the boost converter (14) and the second capacitor (58) and a path is formed between the first position and the second position, thereby bridging the lower arm switching device (44) of the boost converter (14) and connecting the negative terminal of the battery (12) to the inverter (16).

Description

BACKGROUND OF THE INVENTION 1. Field of the invention

[0001] The present invention relates to a power conversion device, and in particular to a power conversion device capable of supplying energy from a battery to an inverter via a boost converter. 2. Description of the related technology

[0002] In related technology, a power supply device is known that incorporates a fault or failure protection function against a fault or failure (see, for example, JP 2012-130108A). This power supply device comprises a switch inserted between a battery and a load on a main power line, and a bypass or circumvention path that bridges or circumvents the switch. The switch toggles between a state of connection between the battery and the load via the main power line and a state of disconnection of this connection. The bypass or circumvention path is a power line that bypasses or circumvents the switch and connects the battery and the load when the switch malfunctions. In this power supply device, the bypass or circumvention path connects the battery and the load even when the switch malfunctions.This makes it possible to ensure an energy supply from the battery to the load.

[0003] The publication JP 2011 - 097 721 A1 discloses a drive unit for a vehicle's dynamo-electric machine that prevents overcurrent in a battery or similar DC power supply, even in a fault mode (i.e., short-circuiting a voltage converter), and thus avoids damage to the battery. The drive unit of the dynamo-electric machine controls the drive of a motor via an inverter. The drive unit is equipped with: a rechargeable and dischargeable battery; a boost converter that converts the battery voltage to supply energy to the inverter; and a control unit that manages the power supply to the boost converter from the battery. The power supply to the boost converter is interrupted when the boost converter is short-circuited, thereby preventing damage to the battery.

[0004] Furthermore, another energy supply device is known from publication WO 2014 / 207 812 A1. SUMMARY OF THE INVENTION

[0005] According to the invention, a power conversion device is provided as defined in the independent claim. Further developments of the power conversion device according to the invention are defined in the dependent claims.

[0006] According to one aspect of the present disclosure, a power conversion device comprises: a battery; a first capacitor connected in parallel to the battery; a boost converter connected to the battery and the first capacitor; a second capacitor connected in parallel to the boost converter; an inverter connected in parallel to the boost converter and the second capacitor; a conductor of an electrical reference potential connecting a negative terminal of the battery to the first capacitor, the boost converter, the second capacitor, and the inverter in the order of the first capacitor, the boost converter, the second capacitor, and the inverter;and a bypass path which, if a lower-arm switching device included in the boost converter has a short-circuit fault, is formed as a result of the interruption of the transmission of an electrical reference potential at a position comprising at least one of a first position between the negative-side terminal and the first capacitor and a second position between the boost converter and the second capacitor. The bypass path bypasses the lower-arm switching device of the boost converter and connects the negative-side terminal to the inverter.

[0007] Further tasks, features and advantages of the present invention will become clearer from the following detailed description when read in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 illustrates a configuration of a power conversion device according to an exemplary embodiment; Fig. Figure 2 is a flowchart of a control routine that is performed in the power conversion device; and Fig. Figure 3 partially illustrates a part of a power conversion device according to a modification. DETAILED DESCRIPTION OF THE EXAMPLES OF EXECUTION

[0008] For reasons of expediency, the description of the aforementioned related technology will be continued first.

[0009] As a system that supplies energy from a battery to a load, there is a system that uses a boost converter in which an upper arm switching device and a lower arm switching device are connected in series. Consideration is being given to providing a bypass path in this system that connects the battery to the load or an inverter to ensure a power supply from the battery to the load or inverter even if the lower arm switching device in the boost converter experiences a short circuit. In this case, it is necessary to provide such a transfer point to switch a power line supplying energy from the battery to the load or inverter between the main power line and the bypass path.

[0010] However, once the transfer point is established, an increase in the inductance of the power line inevitably occurs. Therefore, depending on the actual location of the transfer point, a surge voltage can be increased to such an extent that it exceeds the withstand voltage or dielectric strength of the boost converter or inverter. Alternatively, the costs required to prevent such an increase in surge voltage can be increased.

[0011] The embodiments were developed with this point in mind, and one objective of the embodiments is to provide a power conversion device capable of preventing, at low cost, an increase in impulse voltage generated due to the presence of a switching point for switching between a main power line and a bypass or detour path, while ensuring a power supply from a battery to an inverter with the bypass or detour path when a boost converter or step-up converter experiences a short-circuit fault.

[0012] The power conversion devices are described below with reference to the drawings, according to the exemplary embodiments.

[0013] Fig. Figure 1 illustrates the power conversion device 10 according to the present embodiment.

[0014] The power conversion device 10, for example, is a system installed in an electric or hybrid vehicle that increases the output voltage of a vehicle battery to obtain a higher voltage, supplies this higher voltage to a motor powering the vehicle, and drives the motor. It should be noted that the power conversion device 10 can also be configured to additionally supply energy generated by the motor, after reducing the voltage, to the vehicle battery in order to recharge it.

[0015] The power conversion device 10 comprises a battery 12, a boost converter 14, an inverter 16, and a motor 18. The battery 12 is a rechargeable lithium-ion or nickel-metal hydride battery and is a high-voltage battery capable of outputting a DC voltage of, for example, 240 volts. A positive-side current line 20, which serves as a conductor for an electrical reference potential, is connected to the positive terminal of the battery 12. A negative-side current line 22, which serves as another conductor for an electrical reference potential, is connected to the negative terminal of the battery 12.

[0016] A relay switch 24 is inserted on the positive-side power line 20. Another relay switch 26 is also inserted on the negative-side power line 22. The relay switches 24 and 26 allow electrical connection between the battery 12 and the boost converter 14 via the positive-side power line 20 and the negative-side power line 22, as well as interruption of the electrical connection, and they are switched on and off according to instructions from a control unit.

[0017] A capacitor 28 is connected between the positive-side current line 20 and the negative-side current line 22. In other words, the battery 12 has the capacitor 28 connected in parallel. Along current lines 20 and 22, the capacitor 28 is connected to relay switches 24 and 26 on the side of the boost converter 14. The capacitor 28 acts as a switching device that smooths the output voltage of the battery 12 and stabilizes the voltage applied from the battery 12 to the boost converter 14.

[0018] One or more loads, such as a DC-DC converter or inverter 30, an air conditioner 32 and / or the like, can also be connected between the positive-side power line 20 and the negative-side power line 22, as shown in Fig. Figure 1 shows that in this case, one terminal of the DC voltage converter or inverter 30 and the air conditioner 32 is connected to the positive-side power line 20 at a connection point between the relay switch 24 and the capacitor 28, and the other terminal of each of these is connected to the negative-side power line 22 at a connection point between the relay switch 26 and the capacitor 28.

[0019] The DC-DC converter or inverter 30 is connected to a load, such as an auxiliary battery 34 or the like, which supplies energy at a predetermined voltage (for example, 12 volts or the like) to various electrical devices. The DC-DC converter or inverter 30 comprises one or more coils, one or more switching devices, and / or the like. The DC-DC converter or inverter 30 is capable of reducing the output voltage of battery 12 and then supplying the energy to the auxiliary battery 34. The DC-DC converter or inverter 30 operates under the control of the control unit. The air conditioner 32 receives energy supplied by battery 12 and thus operates.

[0020] The boost converter 14 is connected to the battery 12 and the capacitor 28 via the power lines 20 and 22. The boost converter 14 is a circuit that increases the DC voltage supplied by the battery 12 and the capacitor 28 via the power lines 20 and 22 to a predetermined DC voltage (for example, 650 volts or the like). The boost converter 14 comprises a coil 40, an upper arm device 42, and a lower arm device 44.

[0021] The coil 40 is inserted on the positive-side power line 20. One terminal of the coil 40 is connected to the positive-side terminal of the battery 12 (actually one terminal of the capacitor 28 and the relay switch 24). The other terminal of the coil 40 is connected to the junction between the upper arm device 42 and the lower arm device 44. The coil serves to charge or store energy and to discharge or release energy when a voltage conversion is performed between the battery 12 side and the inverter 16 side.

[0022] The upper arm device 42 and the lower arm device 44 constitute a pair of devices connected in series between a high-voltage current line 48 and the negative-voltage current line 22. The upper arm device 42 and the lower arm device 44 each comprise power semiconductor devices. The junction of the upper arm device 42 and the lower arm device 44 is connected to the positive-voltage current line 22 (actually the other terminal of the coil 40).

[0023] The upper arm device 42 comprises an insulated-gate bipolar transistor (IGBT) 50 and a diode 52. The collector of the IGBT 50 is connected to the high-voltage-side current line 48, and its emitter is connected to the junction between the upper arm device 42 and the lower arm device 44, i.e., the other terminal of the coil 40. The IGBT 50 is a switching device that is turned on and off according to instructions from the control unit described below, thereby performing switching operations. The diode 52 is connected in antiparallel between the collector and the emitter of the IGBT 50. The diode 52 allows current to flow only from the emitter to the collector of the IGBT 50.

[0024] The lower arm device 44 comprises an IGBT 54 and a diode 56. The collector of the IGBT 54 is connected to the junction between the upper arm device 42 and the lower arm device 44, i.e., the other terminal of the coil 40, and the emitter of the IGBT 54 is connected to the negative-side current line 22. The IGBT 54 is a switching device that is turned on and off according to instructions from the control unit, thus performing switching operations. The diode 56 is connected in antiparallel between the collector and the emitter of the IGBT 54. The diode 56 allows current to flow only from the emitter to the collector of the IGBT 54.

[0025] A capacitor 58 is connected between the high-voltage line 48 and the negative-voltage line 22. In other words, the capacitor 58 is connected in parallel with the boost converter 14. The capacitor 58 is a switching device that smooths the voltage between the high-voltage line 48 and the negative-voltage line 22, i.e., the output voltage of the boost converter 14, and stabilizes the voltage applied by the boost converter 14 to the inverter 16.

[0026] Inverter 16 is also connected between the high-voltage line 48 and the negative-voltage line 22. Inverter 16 is connected in parallel with the boost converter and the capacitor 58. Inverter 16 is a circuit that converts the high DC voltage between the high-voltage line 48 and the negative-voltage line 22, supplied by the boost converter 14, into an AC voltage.

[0027] Motor 18 is connected to inverter 16. Motor 18 is a three-phase motor that generates drive energy (for example, drive energy that rotates the drive wheels) from the AC voltage energy / power supplied by inverter 16. It should be noted that the motor can, for example, be a motor-generator that generates energy / power as a result of being driven by the drive wheels. Inverter 16 applies the AC voltage obtained from the conversion to motor 18, thus driving motor 18.

[0028] The inverter 16 includes upper arm devices 60 (i.e., 60U, 60V and 60W in Fig. 1, as described below) and lower arm devices 62 (i.e. 62U, 62V and 62W in Fig. 1, as described below). The upper arm devices 60 and the lower arm devices 62 are pairs of devices, each pair being connected in series between the high-voltage-side power line 48 and the negative-side power line 22. The upper arm devices 60 and the lower arm devices 62 correspond to the respective phases of the motor 18 (i.e., the U-phase, the V-phase, and the W-phase). The upper arm devices 60 and the lower arm devices 62 for the respective phases each comprise power semiconductor devices.

[0029] The upper arm device 60 of each phase comprises an IGBT 64 (i.e., 64U, 64V, or 64W in Fig. 1) and a diode 66 (i.e., 66U, 66V or 66W in Fig. 1) The collector of the IGBT 64 is connected to the high-voltage power line 48, and the emitter of the IGBT 64 is connected to the junction between the upper arm device 60 and the lower arm device 62 on the same phase. The IGBT 64 is a switching device that is turned on and off according to instructions from the control unit, thus performing switching operations. The diode 66 is connected in antiparallel between the collector and the emitter of the IGBT 64. The diode 66 allows current to flow only from the emitter to the collector of the IGBT 64.

[0030] The lower arm device 62 of each phase includes an IGBT 68 (i.e., 68U, 68V, or 68W in Fig. 1) and a diode 70 (i.e. 70U, 70V or 70W in Fig. 1) The collector of the IGBT 68 is connected to the junction between the upper arm device 60 and the lower arm device 62 (actually the emitter of the IGBT 64 of the upper arm device 60) on the same phase, and the emitter of the IGBT 68 is connected to the negative-side current line 22. The IGBT 68 is a switching device that is turned on and off according to instructions from the control unit, and thus performs switching operations. The diode 70 is connected antiparallel between the collector and the emitter of the IGBT 68. The diode 70 allows current to flow only from the emitter to the collector of the IGBT 68.

[0031] As explained above, the suffixes "U", "V", and "W" are added to the respective reference numerals of the upper arm devices 60, the lower arm devices 62, the IGBTs 64 and 68, and the diodes 66 and 70, respectively, by the U phase, the V phase, and the W phase. Therefore, in some cases, these devices are referred to as the upper arm devices 60U, 60V, and 60W; the lower arm devices 62U, 62V, and 62W; the IGBTs 64U, 64V, 64W, 68U, 68V, and 68W; and the diodes 66U, 66V, 66W, 70U, 70V, and 70W.

[0032] The negative-side power line 22 is configured to connect the negative terminal of the battery 12 to the relay switch 26, the capacitor 28, the boost converter 14 (actually the emitter of the IGBT 54 of the lower arm device 44), the capacitor 58, and the inverter 16 (actually the emitters of the IGBTs 68 of the lower arm devices 62) in the specified order. It should be noted that the negative-side power line 22 can also be configured to connect the negative terminal of the battery 12 to the DC-DC converter 30 and the air conditioner 32 in the specified order, or in the reverse order between the relay switch 26 and the capacitor 28.

[0033] The power conversion device 10 also includes a bypass path 72. The bypass path 72 bypasses or bypasses a portion of the negative-side current line 22 such that the lower arm device 44 of the boost converter 14 is bypassed or bypassed. The bypass path 72 is constructed by a fixed busbar, current line, or the like, made of copper or the like. It should be noted that, from the perspective of reducing parasitic inductance and / or reducing inductance fluctuations, the bypass path 72 can preferably be constructed by wiring of a design with parallel flat plates, consisting of a fixed busbar.

[0034] One terminal of the bridging path 72 can be connected to the negative-side current line 22 at a connection point α on the primary side, i.e., the side of the battery 12, from the capacitor 28 (actually between the relay switch 26 (which can alternatively be the DC-DC converter or inverter 30 or the air conditioner 32) and the capacitor 28). The other terminal of the bridging path 72 can be connected to the negative-side current line 22 at a connection point β on the secondary side, i.e., the side of the inverter 16, from the boost converter 14, and also on the primary side, i.e., the side of the boost converter 14, from the capacitor 58 (actually between the boost converter 14 and the capacitor 58).

[0035] The power conversion device 10 further comprises two changeover switches 74 and 76. One terminal of changeover switch 74 is connected to connection point α, and changeover switch 74 is located on the negative-side current line 22 on the primary side, i.e., the side of the battery 12, from the capacitor 28 (actually inserted between the relay switch 26 (which can alternatively be the DC-DC converter or inverter 30 or the air conditioner 32) and the capacitor 28). One terminal of changeover switch 76 is connected to connection point β, and changeover switch 76 is located on the negative-side current line 22 on the secondary side, i.e., the side of the inverter 16, from the boost converter 14, and also on the primary side, i.e., the side of the boost converter 14, from the capacitor 58 (actually inserted between the boost converter 14 and the capacitor 58).

[0036] The respective switches 74 and 76 switch such a connection path, which connects the negative terminal of the battery 12 to the inverter 16, between a main path, i.e., a corresponding part of the negative-side current line 22, which is connected to the boost converter 14, and the bypass path 72, which bypasses the boost converter 14. It should be noted that the switches 74 and 76 can be of a relay contact switching type or a mechanical contact switching type. The relays of the relay contact switching type can be of a mechanical type or of a semiconductor type. In this respect, semiconductor relays are advantageous from the point of view of reducing inductance for surge suppression.

[0037] Switches 74 and 76 are each switched on and off according to instructions from the control unit. Specifically, switches 74 and 76 are each switched off to change the connection path to the corresponding part of the negative-side power line 22. Switches 74 and 76 are each switched on to change the connection path to the bypass path 72. Switches 74 and 76 are switched on and off synchronously with each other.

[0038] The power conversion device 10 further comprises the control unit 80. The control unit 80 is connected to the relay switches 24 and 26, the IGBTs 50 and 54 of the boost converter 14, the IGBTs 64U, 64V, 64W, 68U, 68V and 68W of the inverter 16, and the changeover switches 74 and 76. The control unit 80 controls the switching on and off of the relay switches 24 and 26, the IGBTs 50 and 54 of the boost converter 14, the IGBTs 64U, 64V, 64W, 68U, 68V and 68W of the inverter 16, and the changeover switches 74 and 76.

[0039] The control unit 80 determines whether any shutdown factor (for example, high temperature or the like) occurs with respect to the process of converting the output energy / power of the battery 12 and supplying the converted energy / power to the motor 18. If the control unit 80 determines that no shutdown factor occurs, the control unit 80 switches on the relay switches 24 and 26. In this case, the control unit 80 outputs gate signals such that the IGBTs 50 and 54 of the boost converter 14 are driven in a PWM manner, and it also outputs gate signals such that the IGBTs 64U, 64V, 64W, 68U, 68V and 68W of the respective phases of the inverter 16 are driven in a PWM manner.

[0040] The control unit 80 also detects various faults based on different conditions (for example, voltages, currents, and / or the like). In particular, the control unit 80 detects a short-circuit fault (in other words, a short circuit between the collector and the emitter) of the IGBT 54 of the lower arm device 44 in the boost converter 14. It should be noted that a short-circuit fault of the IGBT 54 can be detected based on a comparison between the voltage at the collector and the voltage at the emitter of the IGBT 54. The control unit 80 controls the switching of the changeover switches 74 and 76 based on the determination of whether a short-circuit fault of the IGBT 54 is present.

[0041] The following describes the operating processes of the power conversion device 10 according to the present embodiment.

[0042] For example, if a demand to drive the motor 18 is made by switching on the vehicle's ignition, or the like, the control unit 80 of the power conversion device 10 increases the output voltage of the battery 12 by means of the boost converter 14, converts the DC voltage thus increased into an AC voltage by means of the inverter 16, and supplies the AC power thus obtained to the motor 18. It should be noted that this process may be stopped if the demand to drive the motor 18 is stopped by switching off the vehicle's ignition, or the like.

[0043] In fact, when the voltage from battery 12 is applied to coil 40, a current flows in the following sequence: positive terminal of battery 12 → positive line 20 → coil 40 → diode 52 of the upper arm device 42 of the boost converter 14 → high-voltage line 48 → capacitor 58 and inverter 16 in parallel with capacitor 58, which supplies power to motor 18 → negative line 22 → negative terminal of battery 12. In this case, capacitor 58 is charged, and coil 40 is also charged.

[0044] When the IGBT 54 of the lower arm device 44 of the boost converter 14 is switched on, starting from the aforementioned state of current flow, a current flows in the following sequence: positive terminal of battery 12 → positive line 20 → coil 40 → IGBT 54 of the lower arm device 44 → negative line 22 → negative terminal of battery 12. In this case, the amount of current flowing through the path described above increases linearly over time, and the coil 40 is charged further in conjunction with the increase in current. It should be noted that in this case, the capacitor 58 is discharged. Therefore, the energy supply to the inverter 16 is maintained.

[0045] Next, when the IGBT 54 of the lower arm device 44 is switched off, a current flows in the following sequence: positive terminal of battery 12 → positive line 20 → coil 40 → diode 52 of the upper arm device 42 of the boost converter 14 → high-voltage line 48 → inverter 16, which supplies power to the motor 18, and capacitor 58 in parallel thereto → negative line 22 → negative terminal of battery 12. In this case, the amount of current flowing through the path described above decreases linearly over time, and the coil 40 is discharged along with the decrease in the amount of current.

[0046] Through this process, the output voltage of the boost converter 14 becomes greater than the output voltage of the battery 12, thus performing a voltage boost. The capacitor 58 is charged up to this increased voltage. The energy supply to the inverter 16 is also maintained at this increased voltage. Therefore, the switching on and off of the IGBT 54 of the lower arm device 44 is repeated, thus maintaining a state in which DC energy / power is supplied to the inverter 16, while the boost converter 14 applies a voltage to the inverter 16 that is greater than the output voltage of the battery 12.

[0047] In the inverter 16, the upper and lower arm devices 60 and 62 of the three phases are switched on and off with their respective phase differences of 120°, and the IGBTs 64U, 64V and 64W of the upper arm devices 60U, 60V and 60W, as well as the IGBTs 68U, 68V, and 68W of the lower arm devices 62U, 62V and 62W, are alternately switched on and off. In this way, the inverter 12 converts the DC voltage supplied from the side of the boost converter 14 into an AC voltage, which is then supplied to the motor 18.

[0048] Through this process, energy is supplied from battery 12 to motor 18, while the boost converter 14 applies the higher voltage to motor 18. Thus, motor 18 is driven. Therefore, in the present embodiment, it is possible to drive motor 18 with energy from battery 12, and thus it is possible to ensure that the vehicle is powered by motor 18.

[0049] Fig. Figure 2 is a flowchart of an example of a control routine performed by the power conversion device 10 in the present embodiment. The in Fig. The routine shown in 2 is performed in / after / at each predetermined time interval in the control unit 80 while the motor 18 is driven.

[0050] In the power conversion device 10, the control unit 80 detects faults based on various states. In particular, the control unit 80 determines whether the IGBT 54 of the lower arm device 44 of the boost converter 14 has a short-circuit fault (step 100).

[0051] If, in step 100, the control unit 80 determines that the IGBT 54 does not exhibit a short-circuit fault, the control unit 80 switches off the two changeover switches 74 and 76, thus connecting the negative terminal of the battery 12 to the capacitor 28 and the boost converter 14 via the negative-side power line 22 (step 110). In this case, since the negative terminal of the battery 12 is connected to the capacitor 28 and the boost converter 14 via the negative-side power line 22, the negative terminal of the battery 12 is also connected to the inverter 16 via the capacitor 28, the boost converter 14, and the capacitor 58.

[0052] Through this process, the output voltage of battery 12 is increased to a higher voltage by the boost converter 14, and energy is supplied from battery 12 to inverter 16 and motor 18, while the boost converter 14 applies the higher voltage to inverter 16 and motor 18. Therefore, as a result of the aforementioned process, it is possible to drive motor 18 with the higher voltage, thus enabling the vehicle to operate in its normal state.

[0053] On the other hand, if the control unit 80 determines in step 100 that the IGBT 54 has a short-circuit fault, the control unit 80 switches on the two changeover switches 74 and 76, thus connecting the negative terminal of the battery 12 to the bypass path 72 (step 120). In this case, the negative current line 22 is interrupted (opened) at the position between the relay switch 26 and the capacitor 28 (connection point α) and also at the position between the boost converter 14 and the capacitor 58 (connection point β). The bypass path 72 is also established, connecting the negative terminal of the battery 12 to the inverter 16, bypassing the lower arm device 44 of the boost converter 14.

[0054] This process disconnects the lower arm device 44 (actually the emitter of the IGBT 54 and the anode of the diode 56) of the boost converter 14, in which the IGBT 54 exhibits the short-circuit fault, from the negative-side current line 22, which is connected to the negative terminal of the battery 12, with the corresponding part in the circuit being replaced by the bypass path 72. Thus, even if the IGBT 54 exhibits the short-circuit fault, it is possible to prevent the electrical potential of the connection point between the upper arm device 42 and the lower arm device 44 of the boost converter 14 from constantly matching the electrical potential of the negative-side current line 22 (in other words, the electrical potential of the negative terminal of the battery 12).Even if the IGBT 54 exhibits the short-circuit fault, it is thus possible to prevent a current output from the positive terminal of the battery 12 from flowing through the positive current line 20 and then continuously flowing via the lower arm device 44 of the boost converter 14 into the negative current line 22 to return to the negative terminal of the battery 12.

[0055] The aforementioned process also maintains the connection between the negative terminal of battery 12 and inverter 16 via the bridging path 72. Therefore, even if, as explained above, the lower arm device 44 of the boost converter 14 is disconnected from the negative current line 22 connected to the negative terminal of battery 12, with the corresponding part being replaced by the bridging path 72, it is still possible to ensure the current path for a return from inverter 16 to the negative terminal of battery 12 via the bridging path 72.

[0056] As explained above, when the lower arm device 44 is disconnected from the negative-side current line 22, which is connected to the negative-side terminal of the battery 12, with the corresponding part being replaced by the bypass path 72, the current output from the positive-side terminal of the battery 12 flows in the following sequence: positive-side current line 20 → coil 40 → diode 52 of the upper arm device 42 → high-voltage-side current line 48 → inverter 16, which supplies power to the motor 18, in parallel with the capacitor 58 → negative-side current line 22 → junction β → bypass path 72 → junction α → negative-side current line 22, and thus returns to the negative-side terminal of the battery 12.

[0057] In this case, since it is not possible to increase the output voltage of battery 12 by the boost converter 14, it is not possible to supply energy from battery 12 at the normally higher voltage to inverter 16 and motor 18. However, since it is possible to apply a lower voltage than the output voltage of battery 12 to inverter 16 and motor 18, it is possible to supply energy from battery 12 to inverter 16 and motor 18 at the lower voltage. Therefore, even during the short-circuit fault of the IGBT 54, it is possible to ensure that voltage from battery 12 is supplied to inverter 16 and motor 18, and thus it is possible to continue driving motor 18. This makes it possible to ensure that the vehicle can be driven, albeit in a limited state (i.e., with limited power).(at a lower speed) compared to the normal state.

[0058] In the present embodiment, when the IGBT 54 exhibits the short-circuit fault, one terminal of the bypass path 72 is connected to the negative-side current line 22 at connection point α, and the other terminal of the bypass path 72 is also connected to the negative-side current line 22 at connection point β. This establishes the bypass path 72. In other words, the connection path that connects the negative-side terminal of the battery 12 to the inverter 16 is switched between the corresponding portion of the negative-side current line 22, which represents the main path connected to the boost converter 14 under normal conditions, and the bypass path 72, which bypasses the boost converter 14 when the IGBT 54 exhibits the short-circuit fault.

[0059] The bridging path 72 is connected to the negative-side current line 22 at connection point α and connection point β. Connection point α is located on the primary side, i.e., the side of battery 12, of capacitor 28 (actually between relay switch 26 and capacitor 28). Connection point β is located on the secondary side, i.e., the side of inverter 16, of boost converter 14, and on the primary side, i.e., the side of boost converter 14, of capacitor 58 (actually between boost converter 14 and capacitor 58).

[0060] For comparison purposes, a similar example is assumed in which the connection point β, where the other end of the bypass path 72, which serves as a countermeasure against a short-circuit fault from the IGBT 54, is connected to the negative-side current line 22, is located on the secondary side (the side of the inverter 16) of the capacitor 58. In this example, the connection point β leads to an increase in the inductance in the circuit on the secondary side of the capacitor 58. As a consequence, the surge voltage on the secondary side of the capacitor 58 increases. To prevent the increase in the surge voltage on the secondary side of the capacitor 58, it is necessary to reduce the switching speeds of all switching devices (IGBTs 64 and 68) on the secondary side of the capacitor 58, or to implement a circuit or...Damping circuitry, such as installing a capacitor immediately adjacent to each arm device 60 or 62 on the secondary side of capacitor 58, can dramatically increase the cost of countermeasures against the shock.

[0061] In a configuration such that the connection point β, where the other end of the bypass path 72, which serves as a countermeasure against the short-circuit disturbance of the IGBT 54, is connected to the negative-side current line 22, is located on the secondary side of the boost converter 14 and the primary side of the capacitor 58, as is the case in the present embodiment, the connection point β leads to an increase in the inductance of the circuit on the primary side of the capacitor 58. As a consequence, the surge voltage on the primary side of the capacitor 58 increases. However, it is sufficient to install a circuit or damping circuit, such as a capacitor, on the primary side of the connection point β and the secondary side of the boost converter 14, or to reduce the switching speed of the switching device (the IGBT 50) to prevent the increase in the surge voltage on the primary side of the capacitor 58.

[0062] Therefore, according to the present embodiment, the connection point β, where the other end of the bridging path 72, which serves as a countermeasure against the short-circuit disturbance of the IGBT 54, is connected to the negative-side current line 22, is located on the secondary side of the boost converter 14 and the primary side of the capacitor 58. By determining the position of the connection point β in this way according to the present embodiment, it is possible to reduce the cost of the countermeasure against the shock compared to the comparative example in which the connection point β is located on the secondary side (the side of the inverter 16) of the capacitor 58.

[0063] Furthermore, according to the present embodiment, the connection point α, where one end of the bridging path 72, which serves as a countermeasure against the short-circuit fault of the IGBT 54, is connected to the negative-side current line 22, is located on the primary side, i.e., the side of the battery 12, of the capacitor 28. By determining the position of the connection point α in this way, according to the present embodiment, neither an increase in inductance on the secondary side of the capacitor 58 nor an increase in inductance on the primary side of the capacitor 58 occurs, such as those described above as a consequence of the presence of the connection point α.Therefore, with the position of the connection point α according to the present embodiment, it is possible to prevent the increase of the impulse voltage on the secondary side of the capacitor 58, and it is also possible to prevent the increase of the impulse voltage on the primary side of the capacitor 58.

[0064] Therefore, with the power conversion device 10 according to the present embodiment, it is possible to ensure the power supply from the battery 12 to the inverter 16 by using the bypass path 72, even if the IGBT 54 of the lower arm device 44 of the boost converter 14 exhibits a short-circuit fault. Furthermore, it is possible to prevent the increase in the surge voltage that is generated due to the presence of the connection points α and β, where the negative-side current line 22 is connected to the bypass path 72. It is also possible to prevent the increase in the surge voltage at low cost. Therefore, it is possible to reduce the surge voltage at low cost to such an extent that it is lower than or equal to the withstand voltage or dielectric strength of the inverter 16.

[0065] In the present embodiment, capacitor 28 represents an example of a "first capacitor". Capacitor 58 represents an example of a "second capacitor". Motor 18 represents an example of a "load". The negative-side current line 22 represents an example of an "electrical reference potential line". The IGBT 54 of the lower arm device 54 of the boost converter 14 represents an example of a "lower arm switching device". The position of connection point α represents an example of a "first position". The position of connection point β represents an example of a "second position". Changeover switches 74 and 76 represent examples of a "switching element". When they proceed to step 100 of the routine according to Fig. 2, the control unit 80 represents an example of a "fault detection element". When it performs step 120 of the routine according to Fig. 2, the control unit 80 represents an example of a “switching control element”.

[0066] According to the present embodiment, the other end of the bridging path 72, which serves as a countermeasure against the short-circuit fault of the IGBT 54, is connected to the negative-side current line 22 at the connection point β on the secondary side of the boost converter 14 and the primary side of the capacitor 58 (actually between the boost converter 14 and the capacitor 58). No circuitry or damping circuit is installed as a countermeasure against the increase in surge voltage on the primary side of the capacitor 58 caused by the presence of the connection point β.

[0067] However, it is also possible to use a 90 capacitor, as described in Fig. As shown in Figure 3, the capacitor 90 is installed as a countermeasure against the increase in the surge voltage on the primary side of the capacitor 58, which is generated due to the presence of the connection point β. The capacitor 90 is used as a circuit or damping circuit connected in parallel to the boost converter 14. One terminal of the capacitor 90 is connected to the negative-side current line 22 between the connection point β and the boost converter 14 (actually the emitter of the IGBT 54 of the lower arm device 44), and the other terminal of the capacitor 90 is connected to the high-voltage-side current line 48.

[0068] According to the modification described above using Fig.As described in section 3, it is possible to effectively suppress the increase in the surge voltage on the primary side of capacitor 58 with capacitor 90 as the circuit or damping circuit, even when using the circuit configuration in which the connection point β on the negative-side current line 22 is located on the secondary side of the boost converter 14 and the primary side of capacitor 58. It should be noted that in this modification, capacitor 90 represents an example of a "third capacitor".

[0069] In the aforementioned embodiments, one end of the bypass path 72 is connected to the negative-side current line 22 at connection point α on the primary side of the capacitor 28, and the other end of the bypass path 72 is connected to the negative-side current line 22 at connection point β on the secondary side of the boost converter 14 and the primary side of the capacitor 58. If the IGBT 54 exhibits a short-circuit fault, the negative-side current line 22 is disconnected or interrupted at both connection point α and connection point β. However, the present invention is not limited to this. It is also possible for the bypass path 72 to be connected at points that include at least one of connection point α and connection point β. In this case, if the IGBT 54 exhibits a short-circuit fault, the negative-side current line 22 is disconnected or interrupted at the respective positions.interrupted, which include at least one of the connection point α and the connection point β.

[0070] This means that if the IGBT 54 exhibits a short-circuit fault, it is possible, for example, if the negative-side current line 22 is interrupted at connection point α by the switch 74, for the negative-side current line 22 to be interrupted at another position on the secondary side (the inverter 16 side) by the capacitor 58 by a corresponding switch. Likewise, if the IGBT 54 exhibits a short-circuit fault, it is possible, for example, if the negative-side current line 22 is interrupted at connection point β by the switch 76, for the negative-side current line 22 to be interrupted at another position between the capacitor 28 and the boost converter 14 by a corresponding switch.

[0071] In the aforementioned embodiments, the IGBTs 50, 54, 64, and 68 are used as the switching devices of the upper arm devices 42 and 60 and the lower arm devices 44 and 62 of the boost converter 14 and the inverter 16, which serve as the power semiconductor devices. However, the present invention is not limited to this. Power metal oxide semiconductor field-effect transistors (power MOSFETs) can also be used as these switching devices.

[0072] In the aforementioned embodiments, the power conversion device 10 is installed in an electric vehicle or a hybrid vehicle. However, the present invention is not limited to this. The power conversion device 10 can also be installed in a device other than a vehicle or the like.

[0073] According to the aforementioned embodiments, it is possible to provide a power conversion device that is capable of preventing, at low cost, an increase in a low-level surge voltage caused by providing a switching point for switching between a main power line and a bypass or bypass path, while ensuring a power supply from a battery to an inverter with a bypass or bypass path when a boost converter or step-up converter experiences a short-circuit fault.

[0074] Thus, the power conversion devices 10 have been described according to the exemplary embodiments. However, the present invention is not limited to these exemplary embodiments. Various modifications and / or implementations, such as combinations with part or all of one or more further exemplary embodiments, one or more substitutions with part of one or more further exemplary embodiments, etc., can be made within the scope of the present invention.

[0075] A capacitor is connected in parallel to a battery; a boost converter is connected to the battery and the first capacitor; another capacitor is connected in parallel to the boost converter; an inverter is connected in parallel to the boost converter and the other capacitor; a conductor carrying an electrical reference potential connects a negative terminal of the battery to the capacitor, the boost converter, the other capacitor, and the inverter in the specified order; and a bypass path is formed, if a lower-arm switching device of the boost converter has a short-circuit fault, by interrupting the conductor carrying an electrical reference potential at a position comprising at least one position between the negative terminal and the capacitor and another position between the boost converter and the other capacitor.The bridging path bypasses the lower arm switching device and connects the negative-side terminal to the inverter.

Claims

[1] Power conversion device (10) comprising: - a battery (12); - a first capacitor (28) connected in parallel to the battery (12); - a boost converter (14) connected to the battery (12) and the first capacitor (28); - a second capacitor (58) connected in parallel to the boost converter (14); - an inverter (16) connected in parallel to the boost converter (14) and the second capacitor (58); - a load (18) connected to the inverter (16); - a conductor of an electrical reference potential (22) connecting a negative terminal of the battery (12) to the first capacitor (28), the boost converter (14), the second capacitor (58), the inverter (16) and the load (18) in the order of the first capacitor (28), the boost converter (14), the second capacitor (58), the inverter (16) and the load (18); and - a bridging path (72) with which, in the event that a lower arm switching device (44) included in the boost converter (14) has a short-circuit fault, the transmission of an electrical reference potential (22) is interrupted at a first position between the negative terminal of the battery (12) and the first capacitor (28) and at a second position between the boost converter (14) and the second capacitor (58), and a path is formed between the first position and the second position, thereby bridging the lower arm switching device (44) of the boost converter (14) and connecting the negative terminal of the battery (12) to the inverter (16). [2] Power conversion device (10) according to claim 1, additionally comprising: - a third capacitor (90), wherein one end of the third capacitor (90) is connected between the boost converter (14) and the second position with the line of an electrical reference potential (22), wherein the third capacitor (90) is connected in parallel to the boost converter (14). [3] Power conversion device (10) according to claim 1 or 2, additionally comprising: - a switching element (74, 76) that switches a connection path connecting the negative terminal of the battery (12) to the inverter (16) between the line of an electrical reference potential (22) and the bridging path (72). [4] Power conversion device (10) according to claim 3, additionally comprising: - a fault detection element that determines whether the lower arm switching device (44) has a short-circuit fault; and - a switching control element that sends an instruction to the switching element (74, 76) to switch the connection path to the bridging path (72) when the fault detection element determines that the lower arm switching device (44) has a short-circuit fault.

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