Power conversion device

Abstract

This power conversion device (300) receives, as input, input power from a power supply (100), subjects the received input power to a power conversion, and outputs an output power to a load (200). The power conversion device (300) comprises: a power conversion circuit (10) equipped with semiconductor switching element groups (14u), (15u), (14v), (15v), (14w), and (15w) each having a control terminal and having a plurality of semiconductor switching elements connected in parallel; and a control circuit unit (30) that outputs, to the control terminals of the plurality of semiconductor switching elements in the semiconductor switching element groups (14u), (15u), (14v), (15v), (14w), and (15w), control signals for controlling on / off of the plurality of semiconductor switching elements in the semiconductor switching element groups (14u), (15u), (14v), (15v), (14w), and (15w) by changing the switching times of the plurality of semiconductor switching elements in the semiconductor switching element groups in accordance with an input voltage input into the power conversion circuit (10).

Description

Power Conversion Device

[0001] The present disclosure relates to a power conversion device such as an inverter or converter in the field of power electronics.

[0002] In recent years, power conversion devices for electric powertrains of hybrid vehicles, electric vehicles, and the like have used semiconductor switching elements such as IGBTs (Insulated Gate Bipolar Transistors) or MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) as switching elements, and in order to process large amounts of power, switching elements in which multiple semiconductor switching elements are connected in parallel are used.

[0003] Patent Document 1 discloses an example in which two semiconductor switching elements connected in parallel as switching elements of a voltage converter in a power converter are assembled into a semiconductor module to suppress gate oscillation. The semiconductor module disclosed in Patent Document 1 includes a pair of metal plates and two transistor chips. The transistor chips are sandwiched between the pair of metal plates and sealed in a resin package. The emitter electrodes of the transistor chips are electrically connected to the other metal plate. Two collector terminals extend from one metal plate inside the resin package, and one emitter terminal extends from the other metal plate. The emitter terminal extends from between the two collector terminals on the side of the package to the outside. The emitter terminal extends from the other metal plate at a position equidistant from the emitter electrodes of the two transistor chips.

[0004] Japanese Patent Application Laid-Open No. 2018-67657

[0005] The inventors varied the voltage applied between the drain and source of a switching element in which two semiconductor switching elements that are turned on and off at the same timing are connected in parallel, that is, the voltage equivalent to the input voltage input to a power conversion circuit of a power conversion device such as an inverter or converter, and found the following problems.

[0006] That is, in a range where the voltage applied between the drain and source is high, the semiconductor switching element has a small surge tolerance value relative to its withstand voltage, so the switching time for controlling the on / off of the semiconductor switching element is lengthened. In a range where the voltage applied between the drain and source is low, if the semiconductor switching element is controlled on / off using the same switching time as in a range where the voltage applied between the drain and source is high, gate oscillation is likely to have a large amplitude, and if large-amplitude gate oscillation occurs, there is a risk of the switching element malfunctioning or being destroyed due to the semiconductor switching element exceeding its withstand voltage.

[0007] The parasitic capacitance between the drain and source of a semiconductor switching element increases as the voltage applied between the drain and source decreases, and the larger the parasitic capacitance between the drain and source, the larger the amount of current flowing between the two semiconductor switching elements, which causes gate oscillation to tend to have a large amplitude.

[0008] On the other hand, in the range where the voltage applied between the drain and source is low, the switching time is short enough so that the amplitude of the gate oscillation does not cause the switching element to malfunction or exceed the withstand voltage of the semiconductor switching element.In the range where the voltage applied between the drain and source is high, if the semiconductor switching element is controlled to be on and off using the same switching time as in the range where the voltage applied between the drain and source is low, the withstand voltage will be exceeded due to a surge.

[0009] The present disclosure has been made in consideration of the above points, and aims to provide a power conversion device that suppresses gate oscillation that occurs in a semiconductor switching element group having a plurality of semiconductor switching elements connected in parallel, which is provided in a power conversion circuit.

[0010] The power conversion device according to the present disclosure is a power conversion device that receives input power from a power source, converts the input power, and outputs output power to a load, and includes a power conversion circuit having a semiconductor switching element group having a plurality of semiconductor switching elements connected in parallel, each having a control terminal, and a control circuit unit that outputs control signals to the control terminals of the plurality of semiconductor switch elements in the semiconductor switching element group to control the on / off of the plurality of semiconductor switch elements in the semiconductor switching element group by changing the switching times of the plurality of semiconductor switch elements in the semiconductor switching element group in accordance with the input voltage input to the power conversion circuit.

[0011] According to the present disclosure, the switching times of multiple semiconductor switching elements in a semiconductor switching element group are changed in accordance with the input voltage input to the power conversion circuit, thereby simultaneously controlling the on / off of multiple semiconductor switching elements in the semiconductor switching element group, thereby suppressing gate oscillation that occurs in the semiconductor switching element group.

[0012] FIG. 1 is a schematic configuration diagram showing a power conversion device according to a first embodiment. FIG. 2 is a schematic configuration diagram mainly showing a half-bridge circuit, which is a one-phase bridge rectifier circuit of a three-phase bridge rectifier circuit in the power conversion device according to the first embodiment, and a part of a control circuit controlling the half-bridge circuit. FIG. 3 is a configuration diagram showing a short-circuit detection unit in the power conversion device according to the first embodiment. FIG. 4 is a conceptual diagram of main waveforms when a low-side arm switching element is in a non-conductive state and a high-side arm switching element is in a conductive state in a half-bridge circuit in the power conversion device according to the first embodiment, and the low-side arm switching element is falsely turned on. FIG. 5 is a conceptual diagram of main reference waveforms when the switching times of the low-side arm and high-side arm switching elements are not changed in a half-bridge circuit. FIG. 6 is a conceptual diagram of main reference waveforms when a low-side arm switching element is in a non-conductive state and a high-side arm switching element is in a conductive state in a half-bridge circuit, and the low-side arm switching element is falsely turned on. 1 is a schematic configuration diagram mainly showing a half-bridge circuit which is a one-phase bridge rectifier circuit in a three-phase bridge rectifier circuit in a power conversion device according to embodiment 2, and a part of a control circuit which controls the half-bridge circuit. 2 is a schematic configuration diagram mainly showing a half-bridge circuit which is a one-phase bridge rectifier circuit in a three-phase bridge rectifier circuit in a power conversion device according to embodiment 3, and a part of a control circuit which controls the half-bridge circuit.

[0013] Embodiment 1. A power conversion device according to embodiment 1 will be described with reference to Figures 1 to 4. A power conversion device 300 according to embodiment 1 is a power conversion device that receives input power from a power source, converts the input power, and outputs output power to a load. Specifically, the power conversion device 300 according to embodiment 1 includes a power conversion circuit 10 that is a three-phase inverter circuit that converts DC power from a DC power source 100 that serves as a power source into three-phase AC power, and supplies the three-phase AC power to a load 200. The following description will mainly focus on a specific example that includes a power conversion circuit 10 that is a three-phase inverter circuit.

[0014] When the power conversion device 300 is applied to an electric vehicle or a hybrid vehicle, the DC power supply 100 is a battery formed of a secondary battery such as a nickel-metal hydride battery or a lithium-ion battery. The DC power supply 100 is a battery used with a rated voltage ranging from about 1000 V to 200 V, for example. The DC power supply 100 is intended to support a particularly high voltage, that is, a maximum voltage of about 1000 V. In the following description, the maximum voltage of about 1000 V within the rated voltage of the DC power supply 100 is referred to as the set voltage.

[0015] In DC power supply 100, a positive electrode is electrically connected to a positive input terminal 1P of power conversion device 300, and a negative electrode is electrically connected to a negative input terminal 1N of power conversion device 300, and DC power supply 100 supplies DC power to power conversion device 300. When power conversion device 300 is applied to an electric vehicle or a hybrid vehicle, load 200 is, for example, a three-phase motor that is an electric motor that drives the drive wheels of the electric vehicle or hybrid vehicle.

[0016] In load 200, the U-phase input terminal is electrically connected to u-phase output terminal 2U of power conversion device 300, the V-phase input terminal is electrically connected to v-phase output terminal 2V of power conversion device 300, and the W-phase input terminal is electrically connected to w-phase output terminal 2W of power conversion device 300, and load 200 is supplied with three-phase AC power from power conversion device 300.

[0017] 1 , the power conversion device 300 according to the first embodiment includes a power conversion circuit 10, a smoothing capacitor 20, a control circuit unit 30, and a voltage sensor circuit 40. One electrode of the smoothing capacitor 20 is connected to a positive power supply wiring 50P that electrically connects a positive input terminal 1P of the power conversion device 300 to a positive input terminal 11P of the power conversion circuit 10, and the other electrode of the smoothing capacitor 20 is connected to a negative power supply wiring 50N that electrically connects a negative input terminal 1N of the power conversion device 300 to a negative input terminal 11N of the power conversion circuit 10. The smoothing capacitor 20 is a smoothing capacitor element for removing voltage ripple and noise in the positive power supply wiring 50P and the negative power supply wiring 50N.

[0018] The power conversion circuit 10 is a switching circuit having switching elements for controlling power. In the first embodiment, the power conversion circuit 10 is a three-phase inverter circuit using a three-phase bridge rectifier circuit (three-phase full-wave rectifier circuit) configured with switching elements 14u, 15u, 14v, 15v, 14w, and 15w.

[0019] The switching elements 14u, 15u, 14v, 15v, 14w, and 15w are semiconductor switching element groups each having a pair of main terminals and a control terminal, and including a plurality of semiconductor switching elements connected in parallel. In the first embodiment, the pair of main terminals is a drain terminal and a source terminal, and the control terminal is a gate terminal. Each semiconductor switching element group is composed of two semiconductor switching elements connected in parallel that are controlled to be turned on and off at the same timing by the same control signal.

[0020] The semiconductor switching elements are turned on when an H-level potential, which is an on-drive voltage, is applied to the gate electrode, i.e., the drain electrode and the source electrode are brought into a conductive state, and are turned off when an L-level potential, which is an off-drive voltage, is applied to the gate electrode, i.e., the drain electrode and the source electrode are brought into a non-conductive state. Each semiconductor switching element group may be composed of three or more semiconductor switching elements connected in parallel and controlled to be turned on and off at the same time in order to output large power.

[0021] The switching elements 14u and 15u constitute a u-phase inverter unit in the three-phase inverter circuit. The switching elements 14u and 15u are connected in series between the positive input terminal 11P and the negative input terminal 11N, and form a half-bridge circuit 13u, which is a u-phase bridge rectifier circuit, with the junction of the switching elements 14u and 15u serving as a u-phase output node 16u.

[0022] The switching elements 14v and 15v constitute a v-phase inverter unit in the three-phase inverter circuit. The switching elements 14v and 15v are connected in series between the positive input terminal 11P and the negative input terminal 11N, and constitute a half-bridge circuit 13v, which is a v-phase bridge rectifier circuit, with the connection point between the switching elements 14v and 15v serving as a v-phase output node 16v.

[0023] Switching elements 14w and 15w constitute a w-phase inverter unit in a three-phase inverter circuit. Switching elements 14w and 15w are connected in series between positive input terminal 11P and negative input terminal 11N, and constitute half-bridge circuit 13w, a w-phase bridge rectifier circuit, in which a connection point between switching elements 14w and 15w becomes w-phase output node 16w.

[0024] Note that the u-phase, v-phase, and w-phase half-bridge circuits 13u, 13v, and 13w in the three-phase inverter circuit that constitutes the power conversion circuit 10 each have the same configuration, and so Fig. 2 shows the half-bridge circuits 13u, 13v, and 13w for one phase and the control signal generating units 31u, 31v, and 31w for one phase of the control circuit unit 30 that control the half-bridge circuits 13u, 13v, and 13w for one phase. Therefore, in the following description, the u-phase, v-phase, and w-phase half-bridge circuits 13u, 13v, and 13w and the control signal generating units 31u, 31v, and 31w will be described using Fig. 2.

[0025] The switching element 14u is a group of semiconductor switching elements arranged as a high-side arm in the u-phase half-bridge circuit 13u, and is electrically connected between the positive input terminal 11P and a u-phase output node 16u. The u-phase output node 16u is electrically connected to a u-phase output terminal 12u of the power conversion circuit 10 via a u-phase power supply wiring. The u-phase output terminal 12u is electrically connected to a u-phase output terminal 2U of the power conversion device 300 via a u-phase power supply wiring. The u-phase output terminal 2U is connected to a U-phase input terminal of the three-phase motor.

[0026] As shown in FIG. 2, the switching element 14u includes a semiconductor switching element 14u1 consisting of a transistor element Tr operating as a semiconductor switching element and a free wheel diode D connected in anti-parallel to the transistor element Tr, and a semiconductor switching element 14u2 consisting of a transistor element Tr operating as a semiconductor switching element and a free wheel diode D connected in anti-parallel to the transistor element Tr and connected in parallel to the semiconductor switching element 14u1.

[0027] The transistor element Tr of the semiconductor switching element 14u1 and the transistor element Tr of the semiconductor switching element 14u2 are turned on and off at the same timing by a control signal for the u-phase high-side arm from the control circuit 30. In the switching element 14u, the drain electrodes of the two transistor elements Tr are electrically connected to the positive input terminal 11P, the source electrodes of the two transistor elements Tr are electrically connected to the u-phase output node 16u, and the gate electrodes of the two transistor elements Tr are electrically connected to an output node 34u of a control signal generating unit 32u for the high-side arm of a control signal generating unit 31u in the control circuit 30.

[0028] The switching element 15u is a semiconductor switching element group arranged as a low-side arm in the u-phase half-bridge circuit 13u, and is electrically connected between the u-phase output node 16u and the negative input terminal 11N. As shown in Figure 2, the switching element 15u includes a semiconductor switching element 15u1 consisting of a transistor element Tr operating as a semiconductor switching element and a diode element D connected in anti-parallel to the transistor element Tr and operating as a free-wheeling diode, and a semiconductor switching element 15u2 consisting of a transistor element Tr operating as a semiconductor switching element and a diode element D connected in anti-parallel to the transistor element Tr and operating as a free-wheeling diode, and connected in parallel to the semiconductor switching element 15u1.

[0029] The transistor element Tr of the semiconductor switching element 15u1 and the transistor element Tr of the semiconductor switching element 15u2 are turned on and off at the same timing by a control signal for the u-phase low-side arm from the control circuit 30. In the switching element 15u, the drain electrodes of the two transistor elements Tr are electrically connected to the u-phase output node 16u, the source electrodes of the two transistor elements Tr are electrically connected to the negative input terminal 11N, and the gate electrodes of the two transistor elements Tr are electrically connected to an output node 35u of a control signal generating unit 33u for the low-side arm of the control signal generating unit 31u in the control circuit 30.

[0030] The two semiconductor switching elements 14u1 and 14u2 that make up the switching element 14u and the two semiconductor switching elements 15u1 and 15u2 that make up the switching element 15u are sealed in the same package with molded resin to form a 2-in-1 power module. Sealing with gel may be used instead of sealing with molded resin.

[0031] The u-phase half-bridge circuit (inverter unit) 13u having a power module structure has a gate terminal, a drain terminal, and a source terminal for a low-side arm, and a gate terminal, a drain terminal, and a source terminal for a high-side arm. The source terminal of the switching element 14u arranged in the high-side arm is located equidistant from the source electrodes of the two transistor elements Tr, and the source terminal of the switching element 15u arranged in the low-side arm is located equidistant from the source electrodes of the two transistor elements Tr.

[0032] Note that, as shown in Patent Document 1, each of switching element 14u and switching element 15u may be configured by a semiconductor module of two semiconductor switching elements. Even in this case, the source terminal of switching element 14u is located at a position equidistant from the source electrodes of the two transistor elements Tr, and the source terminal of switching element 15u is located at a position equidistant from the source electrodes of the two transistor elements Tr.

[0033] Furthermore, when the switching element 14u and the switching element 15u are each configured with three or more semiconductor switching elements to output large power, a configuration may be adopted in which multiple power modules configured with the semiconductor switching elements of the switching element 14u and the semiconductor switching elements of the switching element 15u are connected in parallel.

[0034] Furthermore, when the switching element 14u and the switching element 15u are each configured with three or more semiconductor switching elements to output large power, the switching elements 14u may be configured with a power module in which multiple switching elements are connected in parallel, and the switching elements 15u may be configured with a power module in which multiple switching elements are connected in parallel.

[0035] Switching element 14v is a group of semiconductor switching elements arranged as a high-side arm in v-phase half-bridge circuit 13v, and is electrically connected between positive input terminal 11P and v-phase output node 16v. V-phase output node 16v is electrically connected to v-phase output terminal 12v of power conversion circuit 10 via v-phase power supply wiring. V-phase output terminal 12v is electrically connected to v-phase output terminal 2V of power conversion device 300 via v-phase power supply wiring. V-phase output terminal 2V is connected to the V-phase input terminal of the three-phase motor.

[0036] As shown in FIG. 2, the switching element 14v includes a semiconductor switching element 14v1 consisting of a transistor element Tr operating as a semiconductor switching element and a diode element D connected in anti-parallel to the transistor element Tr and operating as a free-wheeling diode, and a semiconductor switching element 14v2 consisting of a transistor element Tr operating as a semiconductor switching element and a diode element D connected in anti-parallel to the transistor element Tr and operating as a free-wheeling diode, and connected in parallel to the semiconductor switching element 14v1.

[0037] The transistor element Tr of the semiconductor switching element 14v1 and the transistor element Tr of the semiconductor switching element 14v2 are turned on and off at the same timing by a control signal for the v-phase high-side arm from the control circuit 30. In the switching element 14v, the drain electrodes of the two transistor elements Tr are electrically connected to the positive input terminal 11P, the source electrodes of the two transistor elements Tr are electrically connected to the v-phase output node 16v, and the gate electrodes of the two transistor elements Tr are electrically connected to an output node 34v of a control signal generating unit 32v for the high-side arm of the control signal generating unit 31v in the control circuit 30.

[0038] The switching element 15v is a group of semiconductor switching elements arranged as a low-side arm in the v-phase half-bridge circuit 13v, and is electrically connected between the v-phase output node 16v and the negative-side input terminal 11N. As shown in Fig. 2, the switching element 15v includes a semiconductor switching element 15v1 consisting of a transistor element Tr operating as a semiconductor switching element and a diode element D connected in anti-parallel to the transistor element Tr and operating as a free-wheeling diode, and a semiconductor switching element 15v2 consisting of a transistor element Tr operating as a semiconductor switching element and a diode element D connected in anti-parallel to the transistor element Tr and operating as a free-wheeling diode, and connected in parallel to the semiconductor switching element 15v1.

[0039] The transistor element Tr of semiconductor switching element 15v1 and the transistor element Tr of semiconductor switching element 15v2 are turned on and off at the same timing by a control signal for the v-phase low-side arm from control circuit 30. In switching element 15v, the drain electrodes of two transistor elements Tr are electrically connected to v-phase output node 16v, the source electrodes of two transistor elements Tr are electrically connected to negative input terminal 11N, and the gate electrodes of two transistor elements Tr are electrically connected to output node 35v of control signal generator 33v for the low-side arm of control signal generator 31v in control circuit 30.

[0040] The two semiconductor switching elements 14v1 and 14v2 that make up the switching element 14v and the two semiconductor switching elements 15v1 and 15v2 that make up the switching element 15v are sealed in the same package with molded resin to form a 2-in-1 power module structure. Sealing with gel may be used instead of sealing with molded resin.

[0041] The v-phase half-bridge circuit (inverter unit) 13v having a power module structure has a gate terminal, a drain terminal, and a source terminal for a low-side arm, and a gate terminal, a drain terminal, and a source terminal for a high-side arm. The source terminal of the switching element 14v arranged in the high-side arm is located equidistant from the source electrodes of the two transistor elements Tr, and the source terminal of the switching element 15v arranged in the low-side arm is located equidistant from the source electrodes of the two transistor elements Tr.

[0042] In addition, switching element 14v and switching element 15v may each be configured by a semiconductor module of two semiconductor switching elements, similar to switching element 14. Even in this case, the source terminal of switching element 14v is located equidistant from the source electrodes of each of the two transistor elements Tr, and the source terminal of switching element 15v is located equidistant from the source electrodes of each of the two transistor elements Tr.

[0043] Furthermore, when switching element 14v and switching element 15v are each configured with three or more semiconductor switching elements to output large power, multiple power modules configured with the semiconductor switching elements of switching element 14v and the semiconductor switching elements of switching element 15v may be connected in parallel.

[0044] Furthermore, when switching element 14v and switching element 15v are each configured with three or more semiconductor switching elements to output large power, switching element 14v may be configured with a power module in which multiple switching elements are connected in parallel, and switching element 15v may be configured with a power module in which multiple switching elements are connected in parallel.

[0045] Switching element 14w is a group of semiconductor switching elements arranged as a high-side arm in w-phase half-bridge circuit 13w, and is electrically connected between positive input terminal 11P and w-phase output node 16w. W-phase output node 16w is electrically connected to w-phase output terminal 12w of power conversion circuit 10 via w-phase power supply wiring. W-phase output terminal 12w is electrically connected to w-phase output terminal 2W of power conversion device 300 via w-phase power supply wiring. W-phase output terminal 2W is connected to a W-phase input terminal of the three-phase motor.

[0046] As shown in FIG. 2, the switching element 14w includes a semiconductor switching element 14w1 consisting of a transistor element Tr operating as a semiconductor switching element and a diode element D connected in anti-parallel to the transistor element Tr and operating as a free-wheeling diode, and a semiconductor switching element 14w2 consisting of a transistor element Tr operating as a semiconductor switching element and a diode element D connected in anti-parallel to the transistor element Tr and operating as a free-wheeling diode, and connected in parallel to the semiconductor switching element 14w1.

[0047] The transistor element Tr of semiconductor switching element 14w1 and the transistor element Tr of semiconductor switching element 14w2 are turned on and off at the same timing by a control signal for the w-phase high-side arm from control circuit 30. In switching element 14w, the drain electrodes of two transistor elements Tr are electrically connected to positive input terminal 11P, the source electrodes of two transistor elements Tr are electrically connected to w-phase output node 16w, and the gate electrodes of two transistor elements Tr are electrically connected to output node 34w of control signal generator 32w for the high-side arm of control signal generator 31w in control circuit 30.

[0048] The switching element 15w is a semiconductor switching element group arranged as a low-side arm in the w-phase half-bridge circuit 13w, and is electrically connected between the w-phase output node 16w and the negative input terminal 11N. As shown in Fig. 2, the switching element 15w includes a semiconductor switching element 15w1 consisting of a transistor element Tr operating as a semiconductor switching element and a diode element D connected in anti-parallel to the transistor element Tr and operating as a free-wheeling diode, and a semiconductor switching element 15w2 consisting of a transistor element Tr operating as a semiconductor switching element and a diode element D connected in anti-parallel to the transistor element Tr and operating as a free-wheeling diode, and connected in parallel to the semiconductor switching element 15w1.

[0049] The transistor element Tr of semiconductor switching element 15w1 and the transistor element Tr of semiconductor switching element 15w2 are turned on and off at the same timing by a control signal for the w-phase low-side arm from control circuit 30. In switching element 15w, the drain electrodes of two transistor elements Tr are electrically connected to w-phase output node 16w, the source electrodes of two transistor elements Tr are electrically connected to negative input terminal 11N, and the gate electrodes of two transistor elements Tr are electrically connected to output node 35w of control signal generating unit 33w for the low-side arm of control signal generating unit 31w in control circuit 30.

[0050] The two semiconductor switching elements 14w1 and 14w2 that make up the switching element 14w and the two semiconductor switching elements 15w1 and 15w2 that make up the switching element 15w are sealed in the same package with molding resin to form a 2-in-1 power module. Sealing with gel may be used instead of sealing with molding resin.

[0051] A w-phase half-bridge circuit (inverter unit) 13w having a power module structure has a gate terminal, a drain terminal, and a source terminal for a low-side arm and a gate terminal, a drain terminal, and a source terminal for a high-side arm. The source terminal of switching element 14w arranged in the high-side arm is positioned equidistant from the source electrodes of two transistor elements Tr, and the source terminal of switching element 15w arranged in the low-side arm is positioned equidistant from the source electrodes of two transistor elements Tr.

[0052] In addition, switching element 14w and switching element 15w may each be configured by a semiconductor module of two semiconductor switching elements, similar to switching element 14. Even in this case, the source terminal of switching element 14w is located at a position equidistant from the source electrodes of each of the two transistor elements Tr, and the source terminal of switching element 15w is located at a position equidistant from the source electrodes of each of the two transistor elements Tr.

[0053] Furthermore, when switching element 14w and switching element 15w are each configured with three or more semiconductor switching elements to output large power, multiple power modules configured with the semiconductor switching elements of switching element 14w and the semiconductor switching elements of switching element 15w may be connected in parallel.

[0054] Furthermore, when switching element 14w and switching element 15w are each configured with three or more semiconductor switching elements to output large power, switching element 14w may be configured with a power module in which multiple switching elements are connected in parallel, and switching element 15w may be configured with a power module in which multiple switching elements are connected in parallel.

[0055] The transistor elements Tr of the plurality of semiconductor switching elements in the semiconductor switching element group constituting switching element 14u, the transistor elements Tr of the plurality of semiconductor switching elements in the semiconductor switching element group constituting switching element 15u, the transistor elements Tr of the plurality of semiconductor switching elements in the semiconductor switching element group constituting switching element 14v, the transistor elements Tr of the plurality of semiconductor switching elements in the semiconductor switching element group constituting switching element 15v, the transistor elements Tr of the plurality of semiconductor switching elements in the semiconductor switching element group constituting switching element 14w, and the transistor elements Tr of the plurality of semiconductor switching elements in the semiconductor switching element group constituting switching element 15w are each wide bandgap semiconductor elements formed on a semiconductor substrate made of a material such as silicon, silicon carbide, or gallium nitride, and using a wide bandgap semiconductor having a bandgap wider than that of silicon, such as silicon carbide or gallium nitride.

[0056] In the first embodiment, semiconductor switching elements 14u1, 15u1, 14v1, 15v1, 14w1, 15w1 and semiconductor switching elements 14u2, 15u2, 14v2, 15v2, 14w2, 15w2 are power control semiconductor switching elements that are wide bandgap metal oxide semiconductor field effect transistors (MOSFETs). When wide bandgap MOSFETs are used as the above-described semiconductor switching elements, diode element D, which is connected in antiparallel to transistor element Tr and operates as a free wheeling diode, is not configured separately from transistor element Tr, but rather the parasitic diode of the MOSFET serving as transistor element Tr functions as the free wheeling diode.

[0057] It should be noted that each of the above-mentioned semiconductor switching elements may be a power control semiconductor switching element that is a wide bandgap insulated gate bipolar transistor (IGBT). When a wide bandgap IGBT is used, each semiconductor switching element has an IGBT that operates as a transistor element Tr and a wide bandgap diode element that functions as a freewheeling diode D. It is also possible to use other power control semiconductor switching elements such as bipolar transistors for each of the above-mentioned transistor elements Tr.

[0058] When wide band gap semiconductor elements are used as each of the above-mentioned semiconductor switching elements, the wide band gap semiconductor elements have high dielectric breakdown strength and are therefore suitable for a three-phase inverter circuit that constitutes the power conversion circuit 10 that processes high voltage input voltages of up to approximately 1000 V.

[0059] The control circuit 30 acquires information about the input voltage in the power conversion device 300 from the voltage sensor circuit 40, and outputs control signals to control terminals of the semiconductor switching elements in the semiconductor switching element groups to control the on / off of the semiconductor switching elements 14u1 and 14u2, 15u1 and 15u2, 14v1 and 14v2, 15v1 and 15v2, 14w1 and 14w2, and 15w1 and 15w2 in the semiconductor switching element groups constituting each of the switching elements 14u, 15u, 14v, 15v, 14w, and 15w, respectively, in accordance with the input voltage input to the power conversion circuit 10. To avoid complicating the explanation below, the reference numerals of the semiconductor switching elements in the semiconductor switching element groups will be omitted unless a distinction is required.

[0060] In the first embodiment, the control circuit unit 30 outputs a control signal for the low-side arm and a control signal for the high-side arm of the u-phase, a control signal for the low-side arm and a control signal for the high-side arm of the v-phase, and a control signal for the low-side arm and a control signal for the high-side arm of the w-phase, in response to gate terminals which are control terminals corresponding to the groups of semiconductor switching elements arranged in the low-side arm and the high-side arm of the u-phase half-bridge circuit (inverter unit) 13u, the low-side arm and the high-side arm of the v-phase half-bridge circuit (inverter unit) 13v, and the low-side arm and the high-side arm of the w-phase half-bridge circuit (inverter unit) 13w.

[0061] The control circuit unit 30 shortens the switching time when the input voltage input to the power conversion circuit 10 is low. The switching time is the time required to turn on and off a plurality of semiconductor switching elements 14u1 and 14u2, 15u1 and 15u2, 14v1 and 14v2, 15v1 and 15v2, 14w1 and 14w2, and 15w1 and 15w2 in the semiconductor switching element groups that make up each of the switching elements 14u, 15u, 14v, 15v, 14w, and 15w.

[0062] In the first embodiment, the control circuit unit 30 sets the input voltage input to the power conversion circuit 10 to 1000 V, which is the maximum voltage of the DC power supply 100, sets a switching time to suppress the occurrence of surges due to the input voltage so that the withstand voltage of the semiconductor switching element at the set voltage does not exceed, and outputs a control signal to the gate terminal of the semiconductor switching element when the input voltage input to the power conversion circuit 10 is lower than the set voltage, making the switching time shorter than the switching time for the set voltage.

[0063] In embodiment 1, when an input voltage is lower than a set voltage, the power conversion circuit 10 changes the control signal to one that shortens the switching time compared to the control signal that controls the on / off of the semiconductor switching element using the same control signal as the control signal that controls the on / off of the semiconductor switching element based on the switching time for the set voltage.

[0064] For example, when the input voltage to the power conversion circuit 10 is 400 V or less, the switching time is shortened by 15% or more compared to the switching time for the set voltage. The reason why the threshold for switching the switching time is set at 400 V is that the parasitic capacitance Cds between the drain and source of the semiconductor switching element fluctuates greatly, that is, becomes large, when the drain-source voltage reaches about 400 V.

[0065] Although the switching time is switched between two stages, one for a range above 400 V and one below 400 V, the input voltage input to the power conversion circuit 10 may be divided into three or more stages, and the switching time may be shortened toward a range where the input voltage decreases. That is, the voltage range of the input voltage input to the power conversion circuit 10 may be divided into multiple stages, and multiple stages of switching time may be shortened toward a range where the input voltage decreases corresponding to the multiple stages. Furthermore, the switching time may be continuously shortened as the input voltage decreases from the switching time for a set voltage according to the input voltage.

[0066] If the input voltage to the power conversion circuit 10 is lower than the set voltage, that is, if the drain-source voltage of the semiconductor switching element is low, the drain-source parasitic capacitance Cds increases, the drain-source current of the semiconductor switching element increases, and the current flowing through the gate electrode of the semiconductor switching element increases. Because the fluctuation in the gate-source voltage of the semiconductor switching element increases, the amount of change in the gate-source current also increases.

[0067] On the other hand, if there is a variation in characteristics among the parallel-connected semiconductor switching elements that make up a switching element, a deviation may occur in the switching timing of the parallel-connected semiconductor switching elements. When a deviation in switching timing occurs, a potential difference occurs between the potentials of the drain electrodes or the potentials of the source electrodes of the parallel-connected semiconductor switching elements, current flows through the drain-source parasitic capacitance Cds of the parallel-connected semiconductor switching elements, and part of the current flows into the gate electrode via the gate-drain parasitic capacitance Cgd and gate-source parasitic capacitance Cgs of the semiconductor switching element, causing a current to flow between the gate electrodes of the parallel-connected semiconductor switching elements.

[0068] When a current flows between the gate electrodes of semiconductor switching elements connected in parallel, the gate-source voltage of one of the semiconductor switching elements drops, causing a decrease in the drain-source current. The gate electrode voltage of the other semiconductor switching element rises, and the drain-source current increases, driven by the gate-source voltage. This creates a new potential difference between the drain electrodes or source electrodes of the parallel-connected semiconductor switching elements, causing the potential differences of the parallel-connected semiconductor switching elements to alternately reverse, resulting in gate oscillation.

[0069] When the drain-source voltage of the semiconductor switching element is low, the drain-source parasitic capacitance Cds increases, the drain-source current of the semiconductor switching element increases, and the current flowing through the gate electrode of the semiconductor switching element increases, so the amplitude of the gate oscillation tends to increase. In other words, gate oscillation becomes more noticeable when the drain-source voltage of the semiconductor switching elements connected in parallel is low.

[0070] In the first embodiment, when the input voltage input to the power conversion circuit 10 is lower than a set voltage, the switching time is changed to be shorter than the switching time for the set voltage, so that the state in which gate oscillation occurring in the parallel-connected semiconductor switching elements constituting the switching element is prone to oscillation, i.e., the switching operation, can be escaped before it reaches a large amplitude. That is, the semiconductor switching elements are turned on in a short switching time, and the drain-source of the semiconductor switching elements are brought into a conductive state, so that the impedance of the channel portion of the semiconductor switching element is lower than the parasitic capacitance Cds between the drain and source of the semiconductor switching element, and therefore, the exchange of charge via the parasitic capacitance Cds between the drain and source of the parallel-connected semiconductor switching elements does not occur, and the gate oscillation converges.

[0071] Therefore, even when the input voltage input to the power conversion circuit 10 is lower than the set voltage, by shortening the switching time, it is possible to suppress gate oscillation in the switching element, preventing malfunction of the switching element due to gate oscillation or destruction of the semiconductor switching elements that make up the switching element due to exceeding the withstand voltage, and preventing loss of control of the power conversion circuit 10. Furthermore, when the input voltage input to the power conversion circuit 10 is lower than the set voltage, the tolerance for surges relative to the withstand voltage of the semiconductor switching elements is high, so even if the switching time is shortened, the withstand voltage will not be exceeded due to surges.

[0072] In particular, when wide bandgap semiconductor elements having high dielectric breakdown strength against high voltages such as an input voltage of 1000 V are used as the semiconductor switching elements that constitute each of switching elements 14u, 15u, 14v, 15v, 14w, and 15w, wide bandgap semiconductors have high transconductance and are generally prone to oscillation phenomena.

[0073] However, in the first embodiment, when the input voltage to the power conversion circuit 10 is lower than the set voltage, the switching time is changed to be shorter than the switching time for the set voltage, so that the switching operation can be terminated before the gate oscillation reaches a large amplitude, thereby preventing the occurrence of breakdown due to the semiconductor switching element exceeding the withstand voltage. In other words, this is suitable for a power conversion circuit 10 that uses wide bandgap semiconductor elements as the semiconductor switching elements.

[0074] The control circuit unit 30 has a u-phase control signal generating unit 31u, a v-phase control signal generating unit 31v, and a w-phase control signal generating unit 31w. The u-phase, v-phase, and w-phase control signal generating units 31u, 31v, and 31w each have high-side arm control signal generating units 32u, 32v, and 32w, low-side arm control signal generating units 33u, 33v, and 33w, u-phase, v-phase, and w-phase high-side arm short-circuit detecting units 36u, 36v, and 36w, and u-phase, v-phase, and w-phase low-side arm short-circuit detecting units 37u, 37v, and 37w.

[0075] The u-phase, v-phase, and w-phase control signal generating units 31u, 31v, and 31w each have the same configuration, and so Fig. 2 shows only one phase's worth of control signal generating units. In the following explanation, to avoid complexity, the subscripts u, v, and w of the reference symbols are omitted, but the explanation will be of the configuration of each of the u-phase control signal generating unit 31u, the v-phase control signal generating unit 31v, and the w-phase control signal generating unit 31w.

[0076] Control signal generating unit 31 has a high-side arm control signal generating unit 32, a low-side arm control signal generating unit 33, a high-side arm short-circuit detecting unit 36, and a low-side arm short-circuit detecting unit 37. High-side arm control signal generating unit 32 has a high-side arm drive voltage generating unit 321, an on / off command signal generating unit 322, a gate driver 323, and a gate resistor 324.

[0077] The driving voltage generating unit 321 generates the driving voltage of the semiconductor switching element 14 connected in parallel. １ , 14 ２and a drive voltage for turning on the semiconductor switching element 14, which is a high-level potential for turning on the semiconductor switching element 14. １ , 14 ２ The drive voltage generating unit 321 generates an OFF drive voltage, which is an L level potential for turning off the semiconductor switching element 14. １ , 14 ２ The semiconductor switching element 14 １ , 14 ２ The H level potential and the L level potential are set within a range that does not affect the reliability of the gate structure.

[0078] For example, the semiconductor switching element 14 １ , 14 ２ When a wide bandgap MOSFET is used as the switching gate, the relative magnitude of the switching drive voltage is several volts, and the absolute value of the switching drive voltage is on the order of several tens of volts. In addition, by setting the off drive voltage to a negative voltage whose potential direction is opposite to that of the on drive voltage, false firing of the wide bandgap MOSFET can be prevented.

[0079] The on / off command signal generator 322 generates an on / off command signal for the semiconductor switching elements 14 connected in parallel. １ , 14 ２ the on-timing at which the on-operation is started for the semiconductor switching element 14 １ , 14 ２ The ON / OFF command signal is generated to instruct the OFF timing at which the OFF operation should be started.

[0080] The gate driver 323 outputs a control signal for the high-side arm, which is an on-off pulse consisting of an H-level potential that is the on-drive voltage and an L-level potential that is the off-drive voltage from the drive voltage generation unit 321, based on the on-drive voltage and off-drive voltage from the drive voltage generation unit 321 and the on-off command signal from the on-off command signal generation unit 322, between the voltage output node OUT and a reference potential node RP. The reference potential node RP is electrically connected to the source terminal of the switching element 14.

[0081] The gate resistor 324 controls the voltage of the semiconductor switching element 14 by its resistance value. １ , 14 ２ The time required to turn on and off the semiconductor switching element 14, i.e., the switching time, is specified. １ , 14 ２ is turned on and off by a control signal for the high side arm from a gate driver 323 whose switching time is determined by a gate resistor 324.

[0082] One terminal of the gate resistor 324 is electrically connected to the voltage output node OUT of the gate driver 323, and the other terminal is connected to the semiconductor switching element 14 connected in parallel to the switching element 14 via the output node 34 of the control signal generating unit 32. １ , 14 ２ When the input voltage to the power conversion circuit 10 is lower than the set voltage, the resistance value of the gate resistor 324 is lower than the resistance value for the set voltage. The gate resistor 324 switches its resistance value in response to the output signal of the voltage sensor circuit 40.

[0083] When the input voltage input to the power conversion circuit 10 is a set voltage, which is 1000 V in the first embodiment, the resistance value of the gate resistor 324 is set to a set value by an output signal indicating the set voltage of the voltage sensor circuit 40, and the semiconductor switching element 14 １ , 14 ２ The switching time is set as a set time, and when the input voltage input to the power conversion circuit 10 is a voltage lower than the set voltage, 400 V or less in the first embodiment, the resistance value is switched to a resistance value lower than the set value by an output signal indicating a voltage lower than the set voltage of the voltage sensor circuit 40, and the semiconductor switching element 14 １ , 14 ２ The switching time is set to a time shorter than the set time.

[0084] That is, when the input voltage is lower than the set voltage and the resistance value is switched to a resistance value lower than the set value, the resistance value of the semiconductor switching element 14 when the resistance value is the set value is １ , 14 ２ A control signal that results in a switching time shorter than the switching time of the gate resistor 324 is input from the other terminal of the gate resistor 324 to the semiconductor switching element 14１ , 14 ２ The output is then sent to the gate electrode of the

[0085] The low-side arm control signal generating unit 33 includes a low-side arm drive voltage generating unit 331, an ON / OFF command signal generating unit 332, a gate driver 333, and a gate resistor 334. The drive voltage generating unit 331 generates a drive voltage for the low-side arm, and a drive voltage for the semiconductor switching element 15 connected in parallel with the switching element 15. １ , 15 ２ and a drive voltage for turning on the semiconductor switching element 15, which is a high-level potential for turning on the semiconductor switching element 15. １ , 15 ２ The transistor generates an OFF drive voltage, which is an L level potential for turning the transistor into an OFF state.

[0086] The drive voltage generating unit 331 generates a drive voltage for the semiconductor switching element 15 １ , 15 ２ The semiconductor switching element 15 １ , 15 ２ For example, the value of the gate resistance is set within a range that does not affect the reliability of the gate structure of the semiconductor switching element 15. １ , 15 ２ When a wide bandgap MOSFET is used as the switching gate, the relative magnitude of the switching drive voltage is several volts, and the absolute value of the switching drive voltage is on the order of several tens of volts. In addition, by setting the off drive voltage to a negative voltage whose potential direction is opposite to that of the on drive voltage, false firing of the wide bandgap MOSFET can be prevented.

[0087] The on / off command signal generator 332 generates the on / off command signal for the semiconductor switching elements 15 connected in parallel to the switching elements 15. １ , 15 ２ the on-timing for starting the on-operation for the semiconductor switching element 15 １ , 15 ２ The ON / OFF command signal is generated to instruct the OFF timing at which the OFF operation should be started.

[0088] The gate driver 333 outputs a control signal for the low-side arm, which is an on / off pulse consisting of an H-level potential that is the on drive voltage from the drive voltage generation unit 331 and an L-level potential that is the off drive voltage, based on the on drive voltage and off drive voltage from the drive voltage generation unit 331 and the on / off command signal from the on / off command signal generation unit 332, between the voltage output node OUT and the reference potential node RP. The reference potential node RP is electrically connected to the source terminal of the switching element 15.

[0089] The gate resistor 334 controls the semiconductor switching element 15 by its resistance value. １ , 15 ２ The time required to turn on and off the semiconductor switching element 15, i.e., the switching time, is specified. １ , 15 ２ is turned on and off by a control signal for the low-side arm from a gate driver 333 whose switching time is determined by a gate resistor 334.

[0090] One terminal of the gate resistor 334 is electrically connected to the voltage output node OUT of the gate driver 333, and the other terminal is connected to the semiconductor switching element 15 connected in parallel to the switching element 15 via the output node 35 of the control signal generating unit 33. １ , 15 ２ When the input voltage to the power conversion circuit 10 is lower than the set voltage, the resistance value of the gate resistor 334 is lower than the resistance value for the set voltage. The gate resistor 334 switches its resistance value in response to the output signal of the voltage sensor circuit 40.

[0091] When the input voltage input to the power conversion circuit 10 is a set voltage, which is 1000 V in the first embodiment, the resistance value of the gate resistor 334 is set to a set value by an output signal indicating the set voltage of the voltage sensor circuit 40, and the semiconductor switching element 15 １ , 15 ２The switching time is set as a set time, and when the input voltage input to the power conversion circuit 10 is a voltage lower than the set voltage, 400 V or less in the first embodiment, the resistance value is switched to a resistance value lower than the set value by an output signal indicating a voltage lower than the set voltage of the voltage sensor circuit 40, and the semiconductor switching element 15 １ , 15 ２ The switching time is set to a time shorter than the set time.

[0092] That is, when the input voltage is lower than the set voltage and the resistance value is switched to a resistance value lower than the set value, the resistance value of the semiconductor switching element 15 when the resistance value is the set value is １ , 15 ２ A control signal that results in a switching time shorter than the switching time of the gate resistor 334 is input from the other terminal of the gate resistor 334 to the semiconductor switching element 15 １ , 15 ２ The output is then sent to the gate electrode of the

[0093] The high-side short-circuit detection unit 36 ​​detects a short circuit when the switching elements 14 and 15 connected in series in the half-bridge circuit 13 simultaneously become conductive due to erroneous firing of the switching element 15, resulting in a short-circuit, and outputs an OFF command to the ON / OFF command signal generation unit 322.

[0094] Upon receiving the OFF command, the ON / OFF command signal generator 322 causes the gate driver 323 to output an L-level potential, which is an OFF drive voltage, to the voltage output node OUT, forcibly changing the switching element 14 from a conductive state to a non-conductive state. １ , 14 ２ is turned off, the short-circuit current is cut off, and the switching elements 14 and 15 are protected from short circuits.

[0095] The low-side short-circuit detection unit 37 detects a short circuit when the switching elements 14 and 15 connected in series in the half-bridge circuit 13 simultaneously become conductive due to erroneous firing of the switching element 14, resulting in a short-circuit state, and outputs an OFF command to the ON / OFF command signal generation unit 332.

[0096] Upon receiving the OFF command, the ON / OFF command signal generator 332 causes the gate driver 333 to output an L-level potential, which is an OFF drive voltage, to the voltage output node OUT, forcibly changing the switching element 15 from a conductive state to a non-conductive state. １ , 15 ２ is turned off, the short-circuit current is cut off, and the switching elements 14 and 15 are protected from short circuits.

[0097] The short circuit detection unit 36 ​​is configured using the DESAT method, which is a mechanism for monitoring the drain-source voltage of the switching element 14 to determine whether the switching element 14 and the switching element 15 are in a short-circuited state, and if it determines that a short-circuited state exists, outputting an OFF command signal to the ON / OFF command signal generation unit 322. The short circuit detection unit 37 is configured using the DESAT method, which is a mechanism for monitoring the drain-source voltage of the switching element 15 to determine whether the switching element 14 and the switching element 15 are in a short-circuited state, and if it determines that a short-circuited state exists, outputting an OFF command signal to the ON / OFF command signal generation unit 332.

[0098] By using the DESAT method for the short circuit detection units 36 and 37, a wide band gap semiconductor element that is required to maximize the area that can be used as a switching element without forming a current sense cell on the element is used as the semiconductor switching element 14. １ , 14 ２ and semiconductor switching element 15 １ , 15 ２ Even when used as a short circuit protection device, it is possible to provide short circuit protection at low cost.

[0099] 3, each is configured by a DESAT type circuit having comparators 361, 371, threshold generation sources 362, 372, resistors 363, 373, diodes 364, 374, constant current sources 365, 375, switches 366, 376, and capacitors 367, 377. In explaining the components of short circuit detection units 36 and 37, reference numerals are used to avoid duplication of explanation, with 36* indicating the components of short circuit detection unit 36 ​​and 37* indicating the components of short circuit detection unit 37.

[0100] The comparators 361, 371 have one input terminal electrically connected to the short circuit detection nodes 368, 378, the other input terminal electrically connected to the threshold generation sources 362, 372, and the output terminals electrically connected to the ON / OFF command signal generation units 322, 332. If the potential appearing at the short circuit detection nodes 368, 378 is greater than the threshold value set by the threshold generation sources 362, 372, the comparators 361, 371 determine that the switching elements 14, 15 are in a short circuit state, and output an OFF command signal to the output terminal.

[0101] The series circuits of resistors 363, 373 and diodes 364, 374 are electrically connected between short circuit detection nodes 368, 378 and the drain electrodes of switching elements 14, 15 so that the anode electrodes of diodes 364, 374 are located on the short circuit detection nodes 368, 378 side. Constant current sources 365, 375 are electrically connected to short circuit detection nodes 368, 378 via switches 366, 376.

[0102] Switches 366, 376 receive a mask time designation signal, are off when the mask time designation signal indicates the mask time, and are on when the mask time designation signal indicates the lapse of the mask time. When switches 366, 376 are on, constant current sources 365, 375 supply constant current to short circuit detection nodes 368, 378. Capacitors 367, 377 are electrically connected between short circuit detection nodes 368, 378 and the source electrodes of switching elements 14, 15.

[0103] During normal operation when the switching element 14 and the switching element 15 are not short-circuited, the short-circuit detection unit 36 ​​detects that when the switching element 14 is turned on and the switching element 15 is turned off, the drain-source voltage of the switching element 14 becomes lower than the threshold value set by the threshold generating source 362 after the short-circuit detection time has elapsed.

[0104] The mask time designation signal indicates the elapse of the mask time, and after the mask time has elapsed, capacitor 367 begins to be charged by the constant current from constant current source 365. However, since the amount of current discharged to the drain terminal of switching element 14 via the series combination of resistor 363 and diode 364 is set to be greater than the amount of current charged to capacitor 367, the potential of short circuit detection node 368 does not exceed the threshold value after the short circuit detection time has elapsed. As a result, no off command signal is output from comparator 361.

[0105] On the other hand, when switching element 14 and switching element 15 are short-circuited, that is, when switching element 14 is in a conductive state and switching element 15 begins to turn on due to erroneous firing or the like, even after the short-circuit detection time has elapsed, switching element 14 is in a conductive state and switching element 15 is in a conductive state due to erroneous firing or the like, so the drain-source voltage of switching element 14 is higher than the threshold value set by threshold generation source 362.

[0106] When the mask time designation signal indicates the lapse of the mask time and the capacitor 367 starts to be charged by the constant current from the constant current source 365, the potential of the short circuit detection node 368 exceeds the threshold value after the short circuit detection time has elapsed, since the capacitor 367 is not discharged to the drain terminal of the switching element 14 via the series combination of the resistor 363 and the diode 364. As a result, the comparator 361 outputs an OFF command signal, and the control signal generating unit 32, which has received the OFF command signal, turns on the semiconductor switching element 14 constituting the switching element 14. １ , 14 ２ is forcibly changed from a conducting state to an off state, the short-circuit current is cut off, and the switching elements 14 and 15 are protected from short circuits.

[0107] During normal operation when the switching element 14 and the switching element 15 are not short-circuited, the short-circuit detection unit 37 turns on the switching element 15 and turns off the switching element 14, and after the short-circuit detection time has elapsed, the voltage between the drain and source of the switching element 15 becomes lower than the threshold value set by the threshold generation source 372.

[0108] The mask time designation signal indicates the elapse of the mask time, and after the mask time has elapsed, capacitor 377 begins to be charged by the constant current from constant current source 375. However, since the amount of current discharged to the drain terminal of switching element 15 via the series combination of resistor 373 and diode 374 is set to be greater than the amount of current charged to capacitor 377, the potential of short circuit detection node 378 does not exceed the threshold value after the short circuit detection time has elapsed. As a result, no off command signal is output from comparator 371.

[0109] On the other hand, when switching element 14 and switching element 15 are short-circuited, that is, when switching element 15 is in a conductive state and switching element 14 begins to turn on due to erroneous firing or the like, even after the short-circuit detection time has elapsed, switching element 15 is in a conductive state and switching element 14 is in a conductive state due to erroneous firing or the like, so the drain-source voltage of switching element 15 is higher than the threshold value set by threshold generation source 372.

[0110] When the mask time designation signal indicates the lapse of the mask time and the capacitor 377 starts to be charged by the constant current from the constant current source 375, the potential of the short circuit detection node 378 exceeds the threshold value after the short circuit detection time has elapsed, since the capacitor 377 is not discharged to the drain terminal of the switching element 15 via the series combination of the resistor 373 and the diode 374. As a result, the comparator 371 outputs an OFF command signal, and the control signal generating unit 33, which has received the OFF command signal, turns on the semiconductor switching element 15 constituting the switching element 15. １ , 15 ２ is forcibly changed from a conducting state to an off state, the short-circuit current is cut off, and the switching elements 14 and 15 are protected from short circuits.

[0111] The short circuit detection time is a time range set starting from the time when the gate potential of the switching elements 14 and 15 rises, that is, the time when the gate-source voltage starts to rise, and in the first embodiment, it is the sum of the mask time and the time until the capacitors 367 and 377 are charged by the constant current from the constant current sources 365 and 375 in the normal state and the potential of the short circuit detection nodes 368 and 378 reaches the threshold value. The short circuit detection time should be as short as possible so that a short circuit can be detected as quickly as possible. The short circuit detection time is linked to the switching time of the switching elements 14 and 15.

[0112] The short circuit detection time is set as the time from when the switching elements 14, 15 start to turn on until the drain-source voltage has sufficiently dropped during normal operation when the input voltage input to the power conversion circuit 10 is a set voltage and the switching elements 14, 15 are not in a short circuit state, in order to prevent erroneous detection when the drain-source voltage has not sufficiently dropped while the switching elements 14, 15 are turning on, and the short circuit detection units 36, 37 do not perform short circuit detection until the set time has elapsed.

[0113] In the first embodiment, the switches 366 and 376 are kept off by a mask time designation signal until the mask time has elapsed, and after the mask time has elapsed, the switches 366 and 376 are turned on by the mask time designation signal, and the short-circuit state of the switching elements 14 and 15 is determined by the comparators 361 and 371 during the short-circuit detection time (= mask time + charging time of the capacitors 367 and 377 up to the threshold).

[0114] The voltage sensor circuit 40 is connected between the positive power supply wiring 50P and the negative power supply wiring 50N, detects the input voltage input to the power conversion circuit 10, and outputs an output signal according to the detected input voltage to the control circuit unit 30. The control circuit unit 30 outputs a control signal according to the output signal of the voltage sensor circuit 40 to the switching elements 14 and 15 in the power conversion circuit 10.

[0115] The gate resistor 324 of the control signal generating unit 32 for the high side arm and the gate resistor 334 of the control signal generating unit 33 for the low side arm in the control circuit unit 30 that receives the output signal from the voltage sensor circuit 40 have their resistance values ​​changed in accordance with the output signal from the voltage sensor circuit 40.

[0116] In the first embodiment, the output signal from voltage sensor circuit 40 consists of a signal indicating a high voltage in the range of 1000 V, which is the set voltage, when the input voltage input to power conversion circuit 10 exceeds 400 V, and a signal indicating a low voltage of 400 V or less. Gate resistors 324 and 334 are set to a resistance value for the set voltage when the output signal from voltage sensor circuit 40 is a signal indicating a high voltage, and are switched to a resistance value lower than the resistance value for the set voltage when the output signal is a signal indicating a low voltage.

[0117] When the input voltage is high and the resistance values ​​of gate resistors 324 and 334 are the resistance values ​​for the set voltage, if one of switching elements 14 and 15 is turned on and the other is turned off, the drain-source voltage of switching element 14 or 15 that turns on at the end of the short circuit detection time will be less than the short circuit detection threshold, and short circuit detection units 36 and 37 will not detect a short circuit. In other words, the resistance values ​​of gate resistors 324 and 334 for the set voltage are set to values ​​that result in a control signal that provides a switching time when the drain-source voltage of switching elements 14 and 15 becomes less than the short circuit detection threshold at the end of the short circuit detection time when the input voltage is high.

[0118] On the other hand, if the input voltage is low and gate resistors 324 and 334 have resistance values ​​lower than the resistance value for the set voltage, when one of switching elements 14 and 15 is turned on and the other is turned off, the switching time of switching elements 14 and 15 that turn on is shorter than the switching time of switching elements 14 and 15 that turn on when gate resistors 324 and 334 have resistance values ​​for the set voltage, and the state in which gate oscillation occurs in switching elements 14 and 15 that turn on, i.e., the switching operation can be escaped before gate oscillation occurs at the switching elements 14 and 15 reaches a large amplitude. In other words, the resistance values ​​of gate resistors 324 and 334 for the set voltage are set to values ​​that provide control signals with switching times that suppress gate oscillation when the input voltage is low.

[0119] In short, in the power conversion device 300 according to embodiment 1, when the input voltage input to the power conversion circuit 10 is a set voltage, control signals are output from the control circuit unit 30 control signal generating units 32 and 33 such that the switching times of the switching elements 14 and 15 that are turned on are set to a switching time that will not result in false short circuit detection at the end of the short circuit detection time, and when the input voltage input to the power conversion circuit 10 is a low voltage that is less than the set voltage, control signals are output from the control circuit unit 30 control signal generating units 32 and 33 such that the switching times of the switching elements 14 and 15 that are turned on are changed to a switching time that suppresses gate oscillation.

[0120] For reference, the operation during normal operation when gate oscillation is suppressed at low voltages without changing the switching time in response to the input voltage will now be described with reference to Fig. 5. That is, it is assumed that when the input voltage is low, the resistance values ​​of gate resistors 324 and 334 are set to low values, and control signals for switching times that suppress gate oscillation are output from control signal generators 32 and 33 in control circuit 30, and that even when the input voltage is high, control signals with the same resistance values ​​of gate resistors 324 and 334 as when the input voltage is low are output from control signal generators 32 and 33 in control circuit 30.

[0121] In FIG. 5, the horizontal axis represents time, the solid line represents the waveform when the input voltage is high, 1000 V in the first embodiment, and the dashed line represents the waveform when the input voltage is low, 400 V in the first embodiment. In addition, in Figure 5, t0 is the time when switching element 15 (low-side arm) starts to turn on, and is the time when current starts to flow between the drain and source of switching element 15; t1 is the time when the drain-source voltage of switching element 15 becomes zero (end of mirror time) when the input voltage is low; t1' is the time when the drain-source voltage of switching element 15 becomes zero (end of mirror time) when the input voltage is high; t2 is the time when switching element 15 starts to turn off, and is the time when the drain-source voltage of switching element 15 starts to rise (start of mirror time); t3 is the time when switching element 15 completes turning off when the input voltage is low, and is the time when the drain-source current of switching element 15 becomes zero; and t3' is the time when switching element 15 completes turning off when the input voltage is high, and is the time when the drain-source current of switching element 15 becomes zero.

[0122] In the case of switching element 15, when the input voltage is low, the switching time of switching element 15 is the time from time t0 to time t1 when it changes from off to on, and the time from time t2 to time t3 when it changes from on to off. In addition, in the case of switching element 15, when the input voltage is high, the switching time of switching element 15 is the time from time t0 to time t1' when it changes from off to on, and the time from time t2 to time t3' when it changes from on to off.

[0123] When a MOSFET is used as a semiconductor switching element, due to a phenomenon called the Miller effect of the MOSFET, when the input voltage is high, the Miller time, which is the transition time of the voltage between the drain and source when the semiconductor switching element is switched, becomes longer depending on the input voltage compared to when the input voltage is low, and the switching time of the switching element 15 when the input voltage is high becomes longer than the switching time of the switching element 15 when the input voltage is low.

[0124] Therefore, if a control signal that sets a switching time that suppresses gate oscillation when the input voltage is low is input to switching element 15 when the switching element 15 is turned on even when the input voltage is high, the switching time of switching element 15 is long as shown in Figure 5, so the on operation is not completed even at the end of the short circuit detection time, and the voltage between the drain and source of switching element 15 exceeds the short circuit detection threshold, resulting in a false detection of a short circuit.

[0125] The short circuit detection time is shortened to enable quick detection of a short circuit when the input voltage is low, and is also shortened when the input voltage is high because the same short circuit detection time is normally used as when the input voltage is low. The same is true when the switching element 14 is turned on, and false detection of a short circuit occurs when the input voltage is high.

[0126] In contrast to this, in the power conversion device 300 according to embodiment 1, when the input voltage is high, the control signal generating unit 33 in the control circuit unit 30 outputs to the switching element 15 a control signal that sets a switching time at which the drain-source voltage of the switching element 15 becomes less than the short circuit detection threshold at the end of the short circuit detection time when the switching element 15 is turned on, and when the input voltage is low, the control signal from the control signal generating unit 33 in the control circuit unit 30 is changed to output to the switching element 15 a control signal that sets a switching time at which gate oscillation is suppressed when the switching element 15 is turned on.

[0127] As a result, the power conversion device according to the first embodiment prevents the occurrence of a surge in the switching element 15 that exceeds the withstand voltage when the input voltage is high, eliminating false detection of a short circuit, and also prevents the switching element 15 from malfunctioning or exceeding the withstand voltage when the input voltage is low due to gate oscillation. The same applies when the switching element 14 is turned on.

[0128] Next, a case where switching element 14 and switching element 15 are simultaneously brought into a conductive state and short-circuited due to erroneous firing of switching element 14 or switching element 15 or the like in the power conversion device according to embodiment 1 will be described with reference to Fig. 4. Fig. 4 shows waveforms of an operation in which, when switching element 14 (high-side arm) is in a conductive state and switching element 15 (low-side arm) is in a non-conductive state, switching element 15 erroneously turns on for some reason, high-side short-circuit detection unit 36 ​​detects that switching element 14 and switching element 15 are short-circuited, outputs an off command signal to high-side on / off command signal generation unit 322, and control signal generation unit 32 turns off switching element 14 for short-circuit protection.

[0129] In Fig. 4, the horizontal axis represents time, the solid line represents the waveform when the input voltage is high, 1000 V in embodiment 1, and the dashed line represents the waveform when the input voltage is low, 400 V in embodiment 1. Note that, because Fig. 4 is a diagram for explaining a phenomenon that occurs due to differences in switching time, the vertical axis direction is the same for both high and low input voltages.

[0130] The switching element 15 is turned on at time t 00In other words, the voltage between the gate and source of switching element 15 starts to rise. The short circuit detection time starts from the time when switching element 15 starts to turn on. When the input voltage is high, the resistance value of gate resistor 334 in low-side arm control signal generator 33 is high and a control signal that results in a long switching time is input to the gate electrode of switching element 15. Therefore, the voltage between the gate and source of switching element 15 rises gradually, and the state in which the resistance value between the drain and source of switching element 15 is high continues.

[0131] When the input voltage is high, the drain-source voltage of switching element 15 remains high, and therefore the drain-source resistance of switching element 15 changes slowly until the short-circuit current flowing through switching elements 14 and 15 reaches its peak, and then decreases toward zero from the peak of the short-circuit current.

[0132] On the other hand, the drain-source voltage of switching element 14 is determined by the drain-source voltage of switching element 15 when switching element 14 and switching element 15 are short-circuited, and changes slowly when the input voltage is high because the drain-source resistance of switching element 15 remains high. If the drain-source voltage of switching element 14 exceeds the short-circuit detection threshold when the short-circuit detection time has elapsed, short-circuit detection unit 36 ​​detects a short circuit.

[0133] When short circuit detection unit 36 ​​detects a short circuit, control signal generation unit 32 starts to gate off switching element 14. The voltage between the drain and source of switching element 14 changes slowly until the short circuit current flowing through switching elements 14 and 15 reaches its peak, and then rises toward the input voltage from the time the short circuit current reaches its peak.

[0134] When the input voltage is high, the resistance value of gate resistor 324 in high-side arm control signal generating unit 32 is high, and a control signal that has a long switching time is input to the gate electrode of switching element 14, so it takes a long time for switching element 14 to turn off. The switching time of switching element 15 at this time is the time it takes for switching element 15 to turn on from off, and the switching time of switching element 14 is the time it takes for switching element 15 to turn off from on, and the switching times of switching elements 14 and 15 correspond to the time from the point when a short-circuit current (through current) that flows through switching elements 14 and 15 starts to flow and the point when it ends to flow.

[0135] When the input voltage is high, switching element 15 repeats gate oscillation many times, but the drain-source voltage of switching element 15 is high, the switching time is long, and the rise in the gate-source voltage of switching element 15 is gradual, so even if switching element 14 and switching element 15 are simultaneously brought into a conductive state and a short-circuit state occurs due to, for example, erroneous firing of switching element 15, it is possible to prevent the occurrence of exceeding the withstand voltage due to a surge. The same is true when switching element 14 and switching element 15 are simultaneously brought into a conductive state and a short-circuit state occurs due to, for example, erroneous firing of switching element 14.

[0136] Furthermore, when the input voltage is low, the resistance value of the gate resistor 334 in the control signal generating unit 33 for the low-side arm is changed to a low value, and therefore a control signal that results in a shorter switching time is input to the gate electrode of the switching element 15, resulting in a faster rise time and a shorter time until the switching element 15 is turned on.

[0137] When the input voltage is low, the switching time of switching element 15 is shorter, so the resistance value between the drain and source of switching element 15 decreases quickly and the voltage between the drain and source of switching element 15 falls quickly. Because the resistance value between the drain and source of switching element 15 decreases quickly, when switching element 14 and switching element 15 are short-circuited, the drain-source voltage of switching element 14, which is determined by the voltage between the drain and source of switching element 15, changes, that is, falls quickly, when the input voltage is low.

[0138] If the drain-source voltage of the switching element 14 exceeds the short circuit detection threshold when the short circuit detection time has elapsed, the short circuit detection unit 36 ​​detects a short circuit. When the short circuit detection unit 36 ​​detects a short circuit, the control signal generation unit 32 starts to gate off the switching element 14.

[0139] When the input voltage is low, the resistance value of gate resistor 324 in high-side arm control signal generator 32 is low, and a control signal that results in a shorter switching time is input to the gate electrode of switching element 14, so the time until switching element 14 is turned off is short. In other words, the time required to cut off the short-circuit current of switching elements 14 and 15 is shorter.

[0140] At this time, the switching time of switching element 15 is the time it takes for switching element 15 to go from off to on, and the switching time of switching element 14 is the time it takes for switching element 14 to go from on to off. The switching times of switching elements 14 and 15 correspond to the time from the point at which the short-circuit current flowing through switching elements 14 and 15 begins to flow as the start point to the point at which the flow ends as the end point.

[0141] When the input voltage is low, the number of times that gate oscillation is repeated in switching element 15 is small, and the switching operation of switching element 15 can be completed before the vibration due to gate oscillation becomes significant, and even if switching element 14 and switching element 15 are simultaneously brought into a conductive state and short-circuited due to erroneous firing of switching element 15 or the like, gate oscillation of switching element 15 is suppressed. The same is true when switching element 14 and switching element 15 are simultaneously brought into a conductive state and short-circuited due to erroneous firing of switching element 14 or the like.

[0142] In short, in the power conversion device 300 according to embodiment 1, even if switching elements 14 and 15 are simultaneously brought into a conductive state and a short-circuit state occurs due to erroneous firing of switching element 14 or switching element 15, if the input voltage input to power conversion circuit 10 is a set voltage, the switching times of switching elements 14 and 15 are set to a switching time that will not cause erroneous short-circuit detection at the end of the short-circuit detection time, and as a result, control signals are output from control signal generating units 32 and 33 in control circuit unit 30 to a time that starts when short-circuit current flows through switching elements 14 and 15 and ends when the flow ends; and if the input voltage input to power conversion circuit 10 is a low voltage that is less than the set voltage, the switching times of switching elements 14 and 15 are changed to a switching time that suppresses gate oscillation, and as a result, control signals are output from control signal generating units 32 and 33 in control circuit unit 30 to a time that starts when short-circuit current flows through switching elements 14 and 15 and ends when the flow ends.

[0143] Now, for reference, the operation when the switching time is not changed in accordance with the input voltage and the occurrence of exceeding the withstand voltage due to a surge at a high voltage is prevented, and the switching elements 14 and 15 are simultaneously brought into a conductive state due to erroneous firing of the switching element 15 or the like, resulting in a short-circuit state, will be described with reference to FIG. 6.

[0144] 6, the horizontal axis represents time, the solid line represents the waveform when the input voltage is high, 1000 V in the first embodiment, and the dashed line represents the waveform when the input voltage is low, 400 V in the first embodiment. t00 is the time when the short-circuit current starts to flow through switching elements 14 and 15, and t01 is the time when the short-circuit current becomes zero. The time from time t00 to time t01 corresponds to the switching time of switching elements 14 and 15.

[0145] When the input voltage is high, the operation is the same as that described in Fig. 4, so a description thereof will be omitted. Below, a description will be given of the case when the input voltage is low. As in the case when the input voltage is high, the gate-source voltage of switching element 15 rises gradually because the resistance value of gate resistor 334 in low-side arm control signal generator 33 is high and a control signal that results in a long switching time is input to the gate electrode of switching element 15, and the state in which the drain-source resistance value of switching element 15 is high continues.

[0146] As in the case where the input voltage is high, the drain-source voltage of switching element 15 remains in a state where the resistance value between the drain and source of switching element 15 is high, so that the voltage changes slowly until the short-circuit current flowing through switching elements 14 and 15 reaches its peak, and then decreases toward zero from the peak of the short-circuit current.

[0147] On the other hand, when switching element 14 and switching element 15 are short-circuited, the drain-source voltage of switching element 14 is determined by the drain-source voltage of switching element 15, and changes slowly because the drain-source resistance of switching element 15 remains high, just as in the case where the input voltage is high. If the drain-source voltage of switching element 14 exceeds the short-circuit detection threshold when the short-circuit detection time has elapsed, short-circuit detection unit 36 ​​detects a short circuit.

[0148] When the short circuit detection unit 36 ​​detects a short circuit, the control signal generation unit 32 starts to gate off the switching element 14. The voltage between the drain and source of the switching element 14 changes slowly until the short circuit current flowing through the switching elements 14 and 15 reaches its peak, and then rises toward the input voltage from the time the short circuit current reaches its peak.

[0149] As with the case where the input voltage is high, the gate-source voltage of the switching element 14 is high because the resistance value of the gate resistor 324 in the control signal generating unit 32 for the high-side arm is high and a control signal that results in a long switching time is input to the gate electrode of the switching element 14, so it takes a long time for the switching element 14 to turn off.

[0150] Since the voltage between the drain and source of the switching element 15 is maintained at a low voltage for a long time, when the switching element 15 reaches a short-circuit state, gate oscillation is repeated many times, and the vibration due to gate oscillation becomes significant, which may cause the switching element to malfunction or the semiconductor switching element to be destroyed due to exceeding its withstand voltage.

[0151] In contrast to this, in the power conversion device 300 according to embodiment 1, when the input voltage is high, the control signal generating unit 33 in the control circuit unit 30 outputs to the switching element 15 a control signal that sets a switching time at which the drain-source voltage of the switching element 15 becomes less than the short circuit detection threshold at the end of the short circuit detection time when the switching element 15 is turned on, and when the input voltage is low, the control signal from the control signal generating unit 33 in the control circuit unit 30 is changed to output to the switching element 15 a control signal that sets a switching time at which gate oscillation is suppressed when the switching element 15 is turned on.

[0152] As a result, the power conversion device according to the first embodiment prevents the occurrence of a surge in the switching element 15 that exceeds the withstand voltage when the input voltage is high, eliminating false detection of a short circuit, and also prevents the switching element 15 from malfunctioning or exceeding the withstand voltage when the input voltage is low due to gate oscillation. The same applies when the switching element 14 is turned on.

[0153] As described above, in the power conversion device 300 according to the first embodiment, when the input voltage input to the power conversion circuit 10 is a set voltage, for example, a voltage lower than 1000 V, for example, 400 V, the resistance values ​​of the gate resistor 324 of the control signal generating unit 32 for the high side arm and the gate resistor 334 of the control signal generating unit 33 for the low side arm in the control circuit unit 30 of the power conversion circuit 10 are switched to resistance values ​​lower than the set value, and .... １ , 14 ２ , 15 １ , 15 ２ Since the switching time of the plurality of semiconductor switching elements 14 is set to be shorter than the set time, when the input voltage input to the power conversion circuit 10 is the set voltage, １ , 14 ２ , 15 １ , 15 ２ When the input voltage to the power conversion circuit 10 is lower than the set voltage, the plurality of semiconductor switching elements 14 are prevented from being destroyed. １ , 14 ２ , 15 １ , 15 ２ This can suppress gate oscillation when the transistor is turned on.

[0154] However, the power conversion device 300 according to the first embodiment is not limited to a power conversion device having a three-phase inverter circuit that converts DC to three-phase AC, but may also be a power conversion device having a single-phase inverter circuit that converts DC to single-phase AC, a power conversion device having a converter circuit that converts AC to DC, or a power conversion device having a DC-DC converter circuit that transforms voltage. Note that the term "power conversion circuit" includes any of a three-phase inverter circuit, a single-phase inverter circuit, a converter circuit, and a DC-DC converter circuit.

[0155] Second Embodiment A power conversion device according to the second embodiment will be described with reference to Fig. 7 . The power conversion device 300 according to the first embodiment adjusts the switching time in accordance with the input voltage input to the power conversion circuit 10 by changing the resistance values ​​of gate resistor 324 of high-side arm control signal generating unit 32 and gate resistor 334 of low-side arm control signal generating unit 33 in the control circuit unit 30. The power conversion device 300 according to the second embodiment adjusts the switching time in accordance with the input voltage input to the power conversion circuit 10 by changing at least one of the drive voltages for the ON gate and the OFF gate of the semiconductor switching elements in drive voltage generating unit 321 of high-side arm control signal generating unit 32 and drive voltage generating unit 331 of low-side arm control signal generating unit 33 in the control circuit unit 30. The power conversion device 300 according to the second embodiment is otherwise the same as the power conversion device 300 according to the first embodiment. The resistance values ​​of gate resistor 324 and gate resistor 334 are the same regardless of the input voltage input to the power conversion circuit 10. 7, the same reference numerals as those in FIGS. 1 to 3 denote the same or corresponding parts.

[0156] That is, when the input voltage input to the power conversion circuit 10 is lower than the set voltage, the power conversion device 300 according to the second embodiment changes the ON drive voltage to a voltage higher than the ON drive voltage for the set voltage, changes the OFF drive voltage to a voltage lower than the OFF drive voltage for the set voltage, and switches the absolute value of the OFF drive voltage to a larger value. When the ON drive voltage is high, the rise rate of the gate-source voltage of the semiconductor switching element becomes faster, and when the OFF drive voltage is low, the fall rate of the gate-source voltage of the semiconductor switching element becomes faster, and as a result, the switching time of the semiconductor switching element can be shortened.

[0157] As shown in FIG. 7, the drive voltage generating unit 321 sets the ON drive voltage and the OFF drive voltage to the set values ​​in response to an output signal indicating a set voltage that indicates a high voltage from the voltage sensor circuit 40, and １ , 14 ２The switching time is set as a set time, and when the input voltage input to the power conversion circuit 10 is lower than the set voltage, the voltage sensor circuit 40 outputs a signal indicating a voltage lower than the set voltage, so that the ON drive voltage is switched to a drive voltage higher than the set value, and the OFF drive voltage is switched to a drive voltage lower than the set value. As a result, the semiconductor switching element 14 １ , 14 ２ The switching time is set to a time shorter than the set time.

[0158] As shown in FIG. 7, the drive voltage generating unit 331 sets the ON drive voltage and the OFF drive voltage to the set values ​​in response to an output signal indicating a set voltage that indicates a high voltage from the voltage sensor circuit 40, and controls the semiconductor switching element 15 １ , 15 ２ The switching time is set as a set time, and when the input voltage input to the power conversion circuit 10 is lower than the set voltage, the voltage sensor circuit 40 outputs a signal indicating a voltage lower than the set voltage, so that the ON drive voltage is switched to a drive voltage higher than the set value, and the OFF drive voltage is switched to a drive voltage lower than the set value. As a result, the semiconductor switching element 15 １ , 15 ２ The switching time is set to a time shorter than the set time.

[0159] Semiconductor switching element 14 １ , 14 ２ When a wide bandgap MOSFET is used as a MOSFET, the MOSFET performs high-speed switching, and therefore the drain-source voltage transition speed dv / dt during switching is large. The current flowing through the MOSFET gate, generated by the parasitic capacitance Cdg × dv / dt, charges the parasitic capacitance Cgs, raising the gate-source voltage and making it prone to false firing. However, by setting the off drive voltage to a negative voltage whose potential direction is opposite to that of the on drive voltage, and by switching the off drive voltage to a significantly lower drive voltage when the input voltage input to the power conversion circuit 10 is lower than the set voltage, the MOSFET can be prevented from false firing and the switching time can be made shorter than the set time.

[0160] In the power conversion device 300 according to the second embodiment, the ON drive voltage of the semiconductor switching elements in the drive voltage generating unit 321 of the control signal generating unit 32 for the high side arm and the drive voltage generating unit 331 of the control circuit unit 30 for the low side arm in the power conversion circuit 10 is changed to be higher than the ON gate set voltage, or the OFF drive voltage is changed to be lower than the OFF gate set voltage, or the ON drive voltage is switched to be higher and the OFF drive voltage is switched to be lower, based on an output signal indicating that the input voltage input to the power conversion circuit 10 is lower than the set voltage. １ , 14 ２ , 15 １ , 15 ２ Since the switching time of the plurality of semiconductor switching elements 14 is changed to a time shorter than the set time, when the input voltage input to the power conversion circuit 10 is the set voltage, １ , 14 ２ , 15 １ , 15 ２ When the input voltage to the power conversion circuit 10 is lower than the set voltage, the plurality of semiconductor switching elements 14 are prevented from being destroyed. １ , 14 ２ , 15 １ , 15 ２ This can suppress gate oscillation when the transistor is turned on.

[0161] When the power conversion device 300 according to the second embodiment is used as a power conversion device for an electric powertrain of a hybrid vehicle, an electric vehicle, or the like, a lead-acid battery, which is a DC power source for operating auxiliary devices of the hybrid vehicle or the electric vehicle, may be used as the DC power source 100, and a flyback power supply that receives as input a voltage supplied from the lead-acid battery as a drive power source for the control circuit unit 30 may be used as the drive voltage generation unit 321 and the drive voltage generation unit 331. By using the flyback power supplies as the drive voltage generation unit 321 and the drive voltage generation unit 331 in this manner, it is possible to change the duty ratio of the flyback power supply in accordance with the output signal from the voltage sensor circuit 40, thereby achieving a change in the drive voltage.

[0162] Third Embodiment A power conversion device according to a third embodiment will be described with reference to Fig. 8. The power conversion device 300 according to the third embodiment differs from the power conversion device according to the first embodiment in that the short circuit detection times in the high-side short circuit detection unit 36 ​​and the low-side short circuit detection unit 37 are changed in accordance with the input voltage input to the power conversion circuit 10, but is otherwise the same as the power conversion device 300 according to the first embodiment. Note that in Fig. 8, the same reference numerals as those in Figs. 1 to 3 indicate the same or corresponding parts.

[0163] That is, in the power conversion device 300 according to embodiment 3, when the input voltage input to the power conversion circuit 10 is lower than the set voltage, the short circuit detection time in the short circuit detection units 36 and 37 is switched to be shorter. Therefore, when the input voltage is lower than the set voltage, shortening the short circuit detection time shortens the short circuit time between the switching elements 14 and 15, so that the number of times gate oscillation is repeated is reduced and the switching operation of the switching element 15 can be completed before the vibration due to the gate oscillation becomes noticeable.

[0164] In the short circuit detection units 36 and 37 of the power conversion device 300 according to the third embodiment, for example, when the input voltage is high, the short circuit detection time is set to a time at which short circuit detection is possible when a short circuit is detected (gate resistance: large), and when the input voltage is low, the short circuit detection time is set to a time at which short circuit detection is possible when a short circuit is detected (gate resistance: large). Both short circuit detection times are times at which false short circuit detection does not occur when the switching elements 14 and 15 are operating normally. In other words, when the switching elements 14 and 15 are turned on through normal operation, the drain-source voltage of the switching element 14 and the drain-source voltage of the switching element 15 become lower than the threshold voltage when the short circuit detection time has elapsed.

[0165] On the other hand, when the input voltage is low and switching element 14 is in a conducting state and switching element 15 is in a non-conducting state, if switching element 15 erroneously turns on for some reason, after a shorter short-circuit detection time has elapsed, high-side short-circuit detection unit 36 ​​determines that switching element 14 and switching element 15 are in a short-circuit state and outputs an off command signal to high-side on / off command signal generation unit 322, causing control signal generation unit 32 to start operating to turn off switching element 14 for short-circuit protection.

[0166] Therefore, since the switching element 14 starts the turn-off operation earlier, the short-circuit time between the switching element 14 and the switching element 15 is shortened, and the switching operation of the switching element 15 can be completed before the vibration due to the gate oscillation becomes noticeable. The same applies when the switching element 14 is turned on by mistake.

[0167] In the power conversion device 300 according to the third embodiment, the switching time of switching element 15 is the time it takes for switching element 15 to go from off to on, and the switching time of switching element 14 is the time it takes for switching element 15 to go from on to off. The switching times of switching elements 14 and 15 correspond to the time from the point at which the short-circuit current (through current) flowing through switching elements 14 and 15 begins to flow as the starting point to the point at which the flow ends as the ending point.

[0168] 3 , similarly to the first embodiment, short circuit detection units 36 and 37 are configured by DESAT type circuits, and at least one of the mask time of the mask time designation signal, the current value of constant current sources 365 and 375, the threshold value of threshold generation sources 362 and 372, the capacitance value of capacitors 367 and 377, and the resistance value of resistors 363 and 373 is variable. Switching to shorten the short circuit detection time is performed by shortening the mask time of the mask time designation signal input to switches 366 and 396, increasing the current value of constant current sources 365 and 375, lowering the threshold value of threshold generation sources 362 and 372, reducing the capacitance of capacitors 367 and 377, and increasing the resistance value of resistors 363 and 373, or by any combination thereof.

[0169] In short, in the power conversion device 300 according to the third embodiment, when the input voltage input to the power conversion circuit 10 is lower than the set voltage, the short circuit detection time until the short circuit detection unit 36 ​​outputs an OFF command signal is shortened in response to an output signal indicating that the input voltage input to the power conversion circuit 10 is lower than the set voltage. In the event of a short circuit between the switching elements 14 and 15, the short circuit time between the switching elements 14 and 15 is shortened, and the plurality of semiconductor switching elements 14 are more reliably turned off. １ , 14 ２ , 15 １ , 15 ２ This can suppress gate oscillation during erroneous turn-on of the transistor.

[0170] In the power conversion device according to the second embodiment, the short circuit detection times in the high-side short circuit detection unit 36 ​​and the low-side short circuit detection unit 37 may be changed in accordance with the input voltage input to the power conversion circuit 10, as in the third embodiment. １ , 14 ２ , 15 １ , 15 ２ This can suppress gate oscillation during erroneous turn-on of the transistor.

[0171] It should be noted that the embodiments may be freely combined, any of the components of the embodiments may be modified, or any of the components of the embodiments may be omitted.

[0172] The power conversion device according to the present disclosure is suitable for use in a power conversion device for an electric powertrain such as a hybrid vehicle or an electric vehicle, for example, as a high-power inverter or converter.

[0173] 100 power supply, 200 load, 300 power conversion device, 10 power conversion circuit, 14u, 15u, 14v, 15v, 14w, 15w semiconductor switching element group, 20 smoothing capacitor, 30 control circuit unit, 31u u-phase control signal generating unit, 31v v-phase control signal generating unit, 31w w-phase control signal generating unit, 32u, 32v, 32w high-side arm control signal generating unit, 33u, 33v, 33w low-side arm control signal generating unit, 36u, 36v, 36w u-phase, v-phase, w-phase high-side arm short-circuit detection unit, 37u, 37v, 37w u-phase, v-phase, w-phase low-side arm short-circuit detection unit, 40 voltage sensor circuit.

Claims

1. A power conversion device that receives input power from a power source, converts the input power, and outputs output power to a load, comprising: a power conversion circuit including a semiconductor switching element group having a plurality of semiconductor switching elements connected in parallel, each having a control terminal; and a control circuit unit that outputs control signals to the control terminals of the plurality of semiconductor switching elements in the semiconductor switching element group by changing the switching times of the plurality of semiconductor switching elements in the semiconductor switching element group in accordance with an input voltage input to the power conversion circuit, for controlling the on / off of the plurality of semiconductor switching elements in the semiconductor switching element group.

2. The power conversion device according to claim 1, wherein the power conversion circuit includes a half-bridge circuit having a low-side arm and a high-side arm, a group of semiconductor switching elements in the power conversion circuit are disposed in the low-side arm and the high-side arm of the half-bridge circuit, and the control signals output from the control circuit section are a control signal for the low-side arm and a control signal for the high-side arm disposed in the low-side arm and the high-side arm of the half-bridge circuit, respectively.

3. The power supply is a DC power supply consisting of a secondary battery, the power conversion circuit is a three-phase inverter circuit having a u-phase inverter section, a v-phase inverter section, and a w-phase inverter section, the u-phase inverter section, the v-phase inverter section, and the w-phase inverter section each having a low-side arm and a high-side arm, the semiconductor switching element groups in the power conversion circuit are arranged in the low-side arm and high-side arm of the u-phase inverter section, the low-side arm and high-side arm of the v-phase inverter section, and the low-side arm and high-side arm of the w-phase inverter section, respectively, and the control signals output from the control circuit section are a control signal for the low-side arm and a control signal for the high-side arm of the u-phase, a control signal for the low-side arm and a control signal for the high-side arm of the v-phase, and a control signal for the low-side arm and a control signal for the high-side arm of the w-phase, respectively, corresponding to the semiconductor switching element groups arranged in the low-side arm and high-side arm of the u-phase inverter section, the low-side arm and high-side arm of the v-phase inverter section, and the low-side arm and high-side arm of the w-phase inverter section, The power conversion device according to claim 1 .

4. The u-phase inverter unit has a power module structure in which a group of semiconductor switching elements arranged in a low side arm and a group of semiconductor switching elements arranged in a high side arm are molded into the same package, and has a gate terminal for the low side arm to which the gate electrodes of a plurality of semiconductor switching elements in the group of semiconductor switching elements arranged in the low side arm are connected, a drain terminal for the low side arm to which the drain electrodes are connected, and a source terminal for the low side arm to which the source electrodes are connected, and has a gate terminal for the high side arm to which the gate electrodes of a plurality of semiconductor switching elements in the group of semiconductor switching elements arranged in the high side arm are connected, a drain terminal for the high side arm to which the drain electrodes are connected, and a source terminal for the high side arm to which the source electrodes are connected, The v-phase inverter unit has a power module structure in which a semiconductor switching element group arranged in a low side arm and a semiconductor switching element group arranged in a high side arm are molded into the same package, and has a gate terminal for the low side arm to which a gate electrode is connected, a drain terminal for the low side arm to which a drain electrode is connected, and a source terminal for the low side arm to which a source electrode is connected, of a plurality of semiconductor switching elements in the semiconductor switching element group arranged in the low side arm, and has a gate terminal for the high side arm to which a gate electrode is connected, a drain terminal for the high side arm to which a drain electrode is connected, and a source terminal for the high side arm to which a source electrode is connected, of a plurality of semiconductor switching elements in the semiconductor switching element group arranged in the high side arm,4. The power conversion device according to claim 3, wherein the w-phase inverter unit has a power module structure in which a semiconductor switching element group arranged in a low-side arm and a semiconductor switching element group arranged in a high-side arm are molded into the same package, and has a gate terminal for the low-side arm to which a gate electrode is connected, a drain terminal for the low-side arm to which a drain electrode is connected, and a source terminal for the low-side arm to which a source electrode is connected, of a plurality of semiconductor switching elements in the semiconductor switching element group arranged in the low-side arm, and has a gate terminal for the high-side arm to which a gate electrode is connected, a drain terminal for the high-side arm to which a drain electrode is connected, and a source terminal for the high-side arm to which a source electrode is connected, of a plurality of semiconductor switching elements in the semiconductor switching element group arranged in the high-side arm.

5. A power conversion device according to any one of claims 1 to 4, wherein each of the plurality of semiconductor switching elements in the group of semiconductor switching elements is a wide band gap semiconductor element.

6. A power conversion device according to any one of claims 1 to 4, wherein each of the plurality of semiconductor switching elements in the semiconductor switching element group is a wide band gap metal oxide field effect transistor.

7. A power conversion device as claimed in any one of claims 1 to 4, wherein the change in switching time due to the control signal output from the control circuit section is a change that shortens the switching time when the input voltage input to the power conversion circuit is lower than a set voltage.

8. A power conversion device as claimed in any one of claims 1 to 4, wherein the change in switching time due to the control signal output from the control circuit section is a change that shortens the switching time in multiple steps toward a range where the input voltage input to the power conversion circuit becomes lower in response to a voltage range divided into multiple steps.

9. The power conversion device according to claim 7, wherein each of the plurality of semiconductor switching elements in the group of semiconductor switching elements is a wide band gap semiconductor element.

10. A power conversion device as described in claim 7, wherein the change in switching time due to the control signal output from the control circuit section is achieved by changing the resistance value of a gate resistor whose resistance value is changed according to the input voltage input to the power conversion circuit and which determines the switching time of a plurality of semiconductor switching elements in the semiconductor switching element group.

11. The power conversion device as claimed in claim 6, wherein the control circuit section comprises: a gate driver having a voltage output node and a reference potential node electrically connected to source electrodes of a plurality of semiconductor switching elements in the semiconductor switching element group, and outputting a control signal consisting of an H level potential and an L level potential; and a gate resistor having one terminal electrically connected to the voltage output node of the gate driver and the other terminal electrically connected to control terminals of the plurality of semiconductor switching elements in the semiconductor switching element group, and having a resistance value changed to a resistance value lower than the resistance value for a set voltage when an input voltage input to the power conversion circuit is lower than a set voltage.

12. A power conversion device as described in claim 7, wherein the change in switching time due to the control signal output from the control circuit section is performed by changing the voltage value of the gate drive voltage for turning on the multiple semiconductor switching elements in the semiconductor switching element group, which is generated by a drive voltage generating section, in accordance with the input voltage input to the power conversion circuit.

13. A power conversion device as described in claim 7, wherein the change in switching time due to the control signal output from the control circuit section is performed by changing the voltage value of the gate drive voltage for turning off the multiple semiconductor switching elements in the semiconductor switching element group, which is generated by a drive voltage generating section, in accordance with the input voltage input to the power conversion circuit.

14. The power conversion device according to claim 1, wherein the power source is a DC power source consisting of a secondary battery, the power conversion circuit is an inverter circuit having an inverter unit, the inverter unit has a low side arm and a high side arm, a group of semiconductor switching elements in the power conversion circuit are arranged in the low side arm and the high side arm of the inverter unit, the control circuit unit has a short circuit detection unit that monitors the drain-source voltage of the group of semiconductor switching elements arranged in the low side arm to determine whether or not the group of semiconductor switching elements arranged in the low side arm is in a short-circuited state and outputs an off command signal to turn off the group of semiconductor switching elements arranged in the high side arm if it is determined that the group is in a short-circuited state, and the short circuit detection unit changes a short circuit detection time until it outputs an off command signal depending on an input voltage input to the power conversion circuit.

15. A power conversion device that receives input power from a power source, converts the input power, and outputs output power to a load, comprising: a power conversion circuit including a semiconductor switching element group having a plurality of semiconductor switching elements connected in parallel, each having a control terminal; and a control circuit unit that outputs a control signal for controlling on / off of the plurality of semiconductor switching elements in the semiconductor switching element group to the control terminals of the plurality of semiconductor switching elements in the semiconductor switching element group, wherein the control circuit unit has: a gate driver having a voltage output node and a reference potential node electrically connected to source electrodes of the plurality of semiconductor switching elements in the semiconductor switching element group, and outputting a control signal consisting of an H level potential and an L level potential; and a gate resistor having one terminal electrically connected to the voltage output node of the gate driver and the other terminal electrically connected to the control terminals of the plurality of semiconductor switching elements in the semiconductor switching element group, and having a resistance value lower than the resistance value for a set voltage when the input voltage input to the power conversion circuit is lower than a set voltage.

16. A power conversion device that receives input power from a power source, converts the input power, and outputs output power to a load, comprising: a power conversion circuit including a semiconductor switching element group having a plurality of semiconductor switching elements connected in parallel, each having a control terminal; and a control circuit unit that outputs a control signal for controlling the on / off of the plurality of semiconductor switching elements in the semiconductor switching element group to the control terminals of the plurality of semiconductor switching elements in the semiconductor switching element group, wherein the control circuit unit comprises: a drive voltage generation unit that generates an on-gate drive voltage which is an H level potential of the plurality of semiconductor switching elements in the semiconductor switching element group and an off-gate drive voltage which is an L level potential of the plurality of semiconductor switching elements in the semiconductor switching element group, and changes at least one of the on-gate drive voltage or the off-gate drive voltage when the input voltage input to the power conversion circuit is lower than a set voltage; a gate driver having a voltage output node and a reference potential node electrically connected to source electrodes of a plurality of semiconductor switching elements in the semiconductor switching element group, receiving an on-gate drive voltage and an off-gate drive voltage from the drive voltage generating unit, and outputting a control signal consisting of an H-level potential and an L-level potential; and a gate resistor having one terminal electrically connected to the voltage output node of the gate driver and the other terminal electrically connected to control terminals of the plurality of semiconductor switching elements in the semiconductor switching element group.

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