Power conversion device

Abstract

To suppress a gate vibration generated in a semiconductor switching element to which a power conversion circuit is parallely connected.SOLUTION: A power conversion device 300 into which input power from a power supply 100 is input, and which performs a power conversion of the input power to be input, and outputs the input power to a load 200, comprises: a power conversion circuit 10 that includes a control terminal, a plurality of semiconductor switching elements to be parallely connected, and contains semiconductor switching element groups 14u, 15u, 14v, 15v, 14w, and 15w constructing half-bridge circuits 13u, 13v, and 13w; and a control circuit part 30 that changes the switching time of the plurality of semiconductor switching elements in each semiconductor switching element group in accordance with the input voltage of the power conversion circuit 10, and outputs a control signal for performing ON / OFF control of the plurality of semiconductor switching elements in each semiconductor switching element group to the control terminal of the plurality of semiconductor switching elements in each semiconductor switching element group.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] In recent years, in a power conversion device for an electric powertrain such as a hybrid vehicle or an electric vehicle, semiconductor switching elements such as IGBT (Insulated Gate Bipolar Transistor) or MOSFET (Metal Oxide Semiconductor Field Effect Transistor) are used as switching elements, and in order to process large power, switching elements in which a plurality of semiconductor switching elements are connected in parallel are used.

[0003] Patent Document 1 shows an example in which two semiconductor switching elements connected in parallel are used as switching elements of a voltage converter in a power converter and are formed as a semiconductor module in order to suppress gate oscillation. The semiconductor module shown 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 are sealed in a resin package. The emitter electrode of the transistor chip is electrically connected to the other metal plate. Inside the resin package, two collector terminals extend from one metal plate, and one emitter terminal extends from the other metal plate. The emitter terminal extends to the outside from between the two collector terminals on the side surface of the package. The emitter terminal extends from the other metal plate at a position equidistant from the respective emitter electrodes of the two transistor chips.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

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

[0006] That is, in a range where the voltage applied between the drain and source is high, since the allowable value of the surge with respect to the breakdown voltage of the semiconductor switching element is small, 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 turned on and off with the same switching time as in the range where the voltage applied between the drain and source is high, gate oscillation is likely to have a large amplitude. When gate oscillation with a large amplitude occurs, there is a risk of malfunction of the switching element or breakdown due to exceeding the breakdown voltage of the semiconductor switching element.

[0007] The parasitic capacitance between the drain and source of the semiconductor switching element increases as the voltage applied between the drain and source is lower. The larger the parasitic capacitance between the drain and source, the larger the current flowing between the two semiconductor switching elements, which is due to the fact that gate oscillation is likely to have a large amplitude.

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

[0009] The present disclosure has been made in view of the above points, and an object thereof is to obtain a power conversion device that suppresses gate oscillation occurring in a semiconductor switching element group having a plurality of semiconductor switching elements connected in parallel, which is included in a power conversion circuit.

Means for Solving the Problems

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

Effects of the Invention

[0011] According to the present disclosure, since the switching time of a plurality of semiconductor switching elements in the semiconductor switching element group is changed according to an input voltage input to the power conversion circuit to control on / off of the plurality of semiconductor switching elements in the semiconductor switching element group simultaneously, gate oscillation occurring in the semiconductor switching element group can be suppressed.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0013] Embodiment 1. The power conversion device 300 according to Embodiment 1 will be described with reference to FIGS. 1 to 4. The power conversion device 300 according to Embodiment 1 is a power conversion device into which input power from a power source is input, and which converts the input power and outputs output power to a load. The power conversion device 300 according to Embodiment 1 specifically includes a power conversion circuit 10, which is a three-phase inverter circuit that converts DC power from a DC power source 100 serving as a power supply into three-phase AC power, and supplies the three-phase AC power to a load 200. Hereinafter, a specific example including the power conversion circuit 10, which is a three-phase inverter circuit, will be mainly described.

[0014] When the power conversion device 300 is applied to an electric vehicle or a hybrid vehicle, the DC power source 100 is, for example, a battery composed of a secondary battery such as a nickel-metal hydride battery or a lithium-ion battery. The DC power source 100 is a battery used at a rated voltage in the range of about 1000V to 200V, for example. The DC power source 100 assumes a voltage of up to about 1000V, which is particularly compatible with high voltages. In the following description, about 1000V, which is the maximum voltage within the rated voltage of the DC power source 100, is referred to as the set voltage.

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

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

[0017] As shown in FIG. 1, the power conversion device 300 according to Embodiment 1 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 the positive power supply wiring 50P that electrically connects the positive input terminal 1P of the power conversion device 300 and the positive input terminal 11P of the power conversion circuit 10, and the other electrode of the smoothing capacitor 20 is connected to the negative power supply wiring 50N that electrically connects the negative input terminal 1N of the power conversion device 300 and the negative input terminal 11N of the power conversion circuit 10. The smoothing capacitor 20 is a smoothing capacitor element for voltage ripple and noise removal 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 a switching element for controlling power. In the first embodiment, the power conversion circuit 10 is a three-phase inverter circuit formed by a three-phase bridge rectifier circuit (three-phase full-wave rectifier circuit) including switching elements 14u, 15u, 14v, 15v, 14w, and 15w.

[0019] The switching elements 14u, 15u, 14v, 15v, 14w, and 15w are each a semiconductor switching element group 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 are 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 and controlled to be turned on and off at the same timing by the same control signal.

[0020] When a potential of H level, which is a driving voltage for turning on, is applied to the gate electrode of the semiconductor switching element, the element is in an on state, that is, the drain electrode and the source electrode are in a conductive state. When a potential of L level, which is a driving voltage for turning off, is applied to the gate electrode, the element is in an off state, that is, the drain electrode and the source electrode are in a non-conductive state. Each semiconductor switching element group may be composed of three or more semiconductor switching elements that are connected in parallel and controlled to turn on and off at the same timing in order to output a large power.

[0021] The switching element 14u and the switching element 15u constitute the inverter section of the u-phase in the three-phase inverter circuit. The switching element 14u and the switching element 15u are connected in series between the positive input terminal 11P and the negative input terminal 11N, and constitute a half-bridge circuit 13u, which is a bridge rectifier circuit of the u-phase where the connection point of the switching element 14u and the switching element 15u becomes the output node 16u of the u-phase.

[0022] The switching element 14v and the switching element 15v constitute the inverter section of the v-phase in the three-phase inverter circuit. The switching element 14v and the switching element 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 bridge rectifier circuit of the v-phase where the connection point of the switching element 14v and the switching element 15v becomes the output node 16v of the v-phase.

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

[0024] Note that since the half-bridge circuits 13u, 13v, and 13w of the three-phase inverter circuit constituting the power conversion circuit 10 have the same configuration, FIG. 2 shows one-phase half-bridge circuits 13u, 13v, 13w and the control signal generation units 31u, 31v, 31w for one-phase of the control circuit unit 30 that controls the one-phase half-bridge circuits 13u, 13v, 13w. Therefore, in the following description, when explaining each of the half-bridge circuits 13u, 13v, 13w and the control signal generation units 31u, 31v, 31w of the u-phase, v-phase, and w-phase, FIG. 2 is used for the explanation.

[0025] The switching element 14u is a semiconductor switching element group 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 the u-phase output node 16u. The u-phase output node 16u is electrically connected to the u-phase output terminal 12u of the power conversion circuit 10 via the u-phase power supply wiring. The u-phase output terminal 12u is electrically connected to the u-phase output terminal 2U of the power conversion device 300 via the u-phase power supply wiring. The u-phase output terminal 2U is connected to the 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 composed of a transistor element Tr that operates as a semiconductor switching element and a freewheeling diode D connected in anti-parallel with the transistor element Tr, and a semiconductor switching element 14u2 composed of a transistor element Tr that operates as a semiconductor switching element and a freewheeling diode D connected in anti-parallel with the transistor element Tr, and is connected in parallel with the semiconductor switching element 14u1.

[0027] The transistor elements Tr of the semiconductor switching element 14u1 and the semiconductor switching element 14u2 turn on and off at the same timing according to the control signal for the high-side arm of the u-phase from the control circuit unit 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 the output node 34u of the control signal generation unit 32u for the high-side arm of the control signal generation unit 31u in the control circuit unit 30.

[0028] The switching element 15u is a group of semiconductor switching elements arranged as the 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 FIG. 2, the switching element 15u includes a semiconductor switching element 15u1 composed of a transistor element Tr operating as a semiconductor switching element and a diode element D operating as a freewheeling diode, which are connected in anti-parallel to each other, and a semiconductor switching element 15u2 composed of a transistor element Tr operating as a semiconductor switching element and a diode element D operating as a freewheeling diode, which are connected in anti-parallel to each other, and the semiconductor switching element 15u2 is connected in parallel with the semiconductor switching element 15u1.

[0029] The transistor elements Tr of the semiconductor switching element 15u1 and the transistor elements Tr of the semiconductor switching element 15u2 are turned on and off at the same timing by the control signal for the u-phase low-side arm from the control circuit unit 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 the output node 35u of the control signal generation unit 33u for the low-side arm of the control signal generation unit 31u in the control circuit unit 30.

[0030] The two semiconductor switching elements 14u1 and semiconductor switching element 14u2 that make up the switching element 14u and the two semiconductor switching elements 15u1 and semiconductor switching element 15u2 that make up the switching element 15u have a structure of a 2-in-1 power module encapsulated by a molding resin in the same package. Instead of encapsulating with a molding resin, it may be encapsulated with a gel.

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

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

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

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

[0035] The switching element 14v is a group of semiconductor switching elements arranged as a high-side arm in the v-phase half-bridge circuit 13v, and is electrically connected between the positive input terminal 11P and the v-phase output node 16v. The v-phase output node 16v is electrically connected to the v-phase output terminal 12v of the power conversion circuit 10 via a v-phase power supply wiring. The v-phase output terminal 12v is electrically connected to the v-phase output terminal 2V of the power conversion device 300 via a v-phase power supply wiring. The 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 composed of a transistor element Tr operating as a semiconductor switching element and a diode element D operating as a freewheeling diode connected in anti-parallel with the transistor element Tr, and a semiconductor switching element 14v2 composed of a transistor element Tr operating as a semiconductor switching element and a diode element D operating as a freewheeling diode connected in anti-parallel with the transistor element Tr, and the semiconductor switching element 14v2 is connected in parallel with 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 perform on / off operations at the same timing according to a control signal for the v-phase high-side arm from the control circuit unit 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 the output node 34v of the control signal generation unit 32v for the high-side arm of the control signal generation unit 31v in the control circuit unit 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 input terminal 11N. As shown in FIG. 2, the switching element 15v includes a semiconductor switching element 15v1 composed of a transistor element Tr operating as a semiconductor switching element and a diode element D operating as a freewheeling diode, which are connected in anti-parallel with each other, and a semiconductor switching element 15v2 composed of a transistor element Tr operating as a semiconductor switching element and a diode element D operating as a freewheeling diode, which are connected in anti-parallel with each other, and the semiconductor switching element 15v2 is connected in parallel with the semiconductor switching element 15v1.

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

[0040] The two semiconductor switching elements 14v1 and semiconductor switching element 14v2 that make up the switching element 14v and the two semiconductor switching elements 15v1 and semiconductor switching element 15v2 that make up the switching element 15v have a structure of a 2-in-1 power module encapsulated by a molding resin in the same package. Instead of encapsulating with a molding resin, it may be encapsulated with a gel.

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

[0042] Note that the switching element 14v and the switching element 15v may each be composed of two semiconductor switching elements by a semiconductor module in the same manner as the switching element 14. Even in this case, the source terminal of the switching element 14v is at an equal distance from the source electrodes of the two transistor elements Tr respectively, and the source terminal of the switching element 15v is at an equal distance from the source electrodes of the two transistor elements Tr respectively.

[0043] Also, when the switching element 14v and the switching element 15v are each composed of three or more semiconductor switching elements to output high power, a configuration in which a plurality of power modules composed of the semiconductor switching elements of the switching element 14v and the semiconductor switching elements of the switching element 15v are connected in parallel may be adopted.

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

[0045] The switching element 14w is a group of semiconductor switching elements arranged as a high-side arm in the w-phase half-bridge circuit 13w, and is electrically connected between the positive input terminal 11P and the w-phase output node 16w. The w-phase output node 16w is electrically connected to the w-phase output terminal 12w of the power conversion circuit 10 via a w-phase power supply wiring. The w-phase output terminal 12w is electrically connected to the w-phase output terminal 2W of the power conversion device 300 via a w-phase power supply wiring. The w-phase output terminal 2W is connected to the 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 composed of a transistor element Tr operating as a semiconductor switching element and a diode element D operating as a freewheeling diode connected in anti-parallel with the transistor element Tr, and a semiconductor switching element 14w2 composed of a transistor element Tr operating as a semiconductor switching element and a diode element D operating as a freewheeling diode connected in anti-parallel with the transistor element Tr, and the semiconductor switching element 14w2 is connected in parallel with the semiconductor switching element 14w1.

[0047] The transistor element Tr of the semiconductor switching element 14w1 and the transistor element Tr of the semiconductor switching element 14w2 perform an on / off operation at the same timing according to a control signal for the w-phase high-side arm from the control circuit unit 30. In the switching element 14w, 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 w-phase output node 16w, and the gate electrodes of the two transistor elements Tr are electrically connected to the output node 34w of the control signal generation unit 32w for the high-side arm of the control signal generation unit 31w in the control circuit unit 30.

[0048] The switching element 15w is a group of semiconductor switching elements 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 composed of a transistor element Tr that operates as a semiconductor switching element and a diode element D that operates as a freewheeling diode, which are connected in antiparallel, and a semiconductor switching element 15w2 composed of a transistor element Tr that operates as a semiconductor switching element and a diode element D that operates as a freewheeling diode, which are connected in antiparallel, and is connected in parallel with the semiconductor switching element 15w1.

[0049] The transistor elements Tr of the semiconductor switching element 15w1 and the transistor elements Tr of the semiconductor switching element 15w2 perform on / off operations at the same timing according to the control signal for the w-phase low-side arm from the control circuit unit 30. In the switching element 15w, the drain electrodes of the two transistor elements Tr are electrically connected to the w-phase output node 16w, 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 the output node 35w of the control signal generation unit 33w for the low-side arm of the control signal generation unit 31w in the control circuit unit 30.

[0050] The two semiconductor switching elements 14w1 and semiconductor switching element 14w2 that make up the switching element 14w and the two semiconductor switching elements 15w1 and semiconductor switching element 15w2 that make up the switching element 15w take the structure of a 2-in-1 power module encapsulated by a molding resin in the same package. Instead of encapsulating with a molding resin, it may be encapsulated with a gel.

[0051] The w-phase half-bridge circuit (inverter section) 13w having the structure of the power module has a gate terminal, a drain terminal, and a source terminal for the low-side arm, and a gate terminal, a drain terminal, and a source terminal for the high-side arm. The source terminal of the switching element 14w arranged on the high-side arm is at an equal distance from the source electrodes of the two transistor elements Tr respectively, and the source terminal of the switching element 15w arranged on the low-side arm is at an equal distance from the source electrodes of the two transistor elements Tr respectively.

[0052] Note that the switching element 14w and the switching element 15w may each be composed of two semiconductor switching elements by a semiconductor module in the same manner as the switching element 14. Even in this case, the source terminal of the switching element 14w is at an equal distance from the source electrodes of the two transistor elements Tr respectively, and the source terminal of the switching element 15w is at an equal distance from the source electrodes of the two transistor elements Tr respectively.

[0053] Also, when the switching element 14w and the switching element 15w are each composed of three or more semiconductor switching elements to output a large power, a configuration in which a plurality of power modules composed of the semiconductor switching elements of the switching element 14w and the semiconductor switching elements of the switching element 15w are connected in parallel may be adopted.

[0054] Furthermore, when the switching element 14w and the switching element 15w are each composed of a plurality of three or more semiconductor switching elements in order to output a large power, they may be configured by a power module in which a plurality of switching elements 14w are connected in parallel, and configured by a power module in which a plurality of switching elements 15w are connected in parallel.

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

[0056] In Embodiment 1, each of the semiconductor switching elements 14u1, 15u1, 14v1, 15v1, 14w1, 15w1 and the semiconductor switching elements 14u2, 15u2, 14v2, 15v2, 14w2, 15w2 is a semiconductor switching element for power control, which is a wide-bandgap metal oxide semiconductor field effect transistor (MOSFET). When a wide-bandgap MOSFET is used as each of the semiconductor switching elements described above, the diode element D that is connected in antiparallel with the transistor element Tr and operates as a freewheeling diode is not separately configured with respect to the transistor element Tr, and the parasitic diode of the MOSFET as the transistor element Tr functions as a freewheeling diode.

[0057] In addition, a semiconductor switching element for power control that is a wide-bandgap insulated gate bipolar transistor (IGBT: Insulated Gate Bipolar Transistor) may be used as each of the semiconductor switching elements described above. 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. Also, each of the above-described transistor elements Tr may use other semiconductor switching elements for power control such as bipolar transistors.

[0058] When a wide-bandgap semiconductor element is used as each of the semiconductor switching elements described above, since the wide-bandgap semiconductor element has a high breakdown strength, it is suitable for a three-phase inverter circuit that constitutes a power conversion circuit 10 that processes an input voltage of up to about 1000V, which can handle high voltages.

[0059] The control circuit unit 30 acquires information on the input voltage in the power conversion device 300 from the voltage sensor circuit 40, and changes the switching times of a plurality of semiconductor switching elements 14u1 and 14u2, 15u1 and 15u2, 14v1 and 14v2, 15v1 and 15v2, 14w1 and 14w2, 15w1 and 15w2 in the semiconductor switching element groups constituting the switching elements 14u, 15u, 14v, 15v, 14w, 15w respectively according to the input voltage input to the power conversion circuit 10, and outputs control signals for on / off controlling the plurality of semiconductor switching elements in the semiconductor switching element groups to the control terminals of the plurality of semiconductor switching elements in the semiconductor switching element groups. Hereinafter, since the description becomes complicated, the reference signs of the plurality of semiconductor switching elements in the semiconductor switching element group are omitted except when it is necessary to distinguish and describe.

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

[0061] When the input voltage input to the power conversion circuit 10 is low, the control circuit unit 30 changes the switching time to be short. The switching time is the time taken for the on / off operation of a plurality of semiconductor switching elements 14u1 and 14u2, 15u1 and 15u2, 14v1 and 14v2, 15v1 and 15v2, 14w1 and 14w2, 15w1 and 15w2 in the semiconductor switching element groups that respectively constitute the switching elements 14u, 15u, 14v, 15v, 14w, 15w.

[0062] In Embodiment 1, the control circuit unit 30 sets the input voltage input to the power conversion circuit 10 to 1000V, which is the maximum voltage of the DC power supply 100, as the set voltage, and sets the switching time to suppress the generation of surges due to the input voltage so that the breakdown voltage of the semiconductor switching element does not exceed at the set voltage. When the input voltage input to the power conversion circuit 10 is lower than the set voltage, a control signal is output to the gate terminal of the semiconductor switching element to make the switching time shorter than the switching time for the set voltage.

[0063] In Embodiment 1, at an input voltage lower than the set voltage, the power conversion circuit 10 changes to a control signal that makes the switching time shorter than the switching time by the control signal for on / off controlling the semiconductor switching element with the same control signal as the control signal for on / off controlling the semiconductor switching element by the switching time for the set voltage.

[0064] For example, when the input voltage input to the power conversion circuit 10 is 400V or less, the switching time is made 15% or more shorter than the switching time for the set voltage. The boundary for switching the switching time is set to 400V because the parasitic capacitance Cds between the drain and source of the semiconductor switching element varies greatly, that is, has a large dependence, with the voltage between the drain and source as the boundary at about 400V.

[0065] Note that the switching time is switched between two levels: a range where the input voltage applied to the power conversion circuit 10 exceeds 400 V and a range where it is 400 V or less. However, it may be configured to be divided into three or more levels, and the switching time may be changed to be shorter as the input voltage decreases. That is, the voltage range of the input voltage applied to the power conversion circuit 10 may be divided into a plurality of levels, and the switching time may be set to a plurality of short levels corresponding to the plurality of levels as the input voltage decreases. Alternatively, it may be configured such that the switching time is continuously changed to be shorter as the input voltage decreases from the switching time with respect to the set voltage according to the input voltage.

[0066] When the input voltage applied to the power conversion circuit 10 is lower than the set voltage, that is, when the voltage between the drain and source of the semiconductor switching element is low, the parasitic capacitance Cds between the drain and source of the semiconductor switching element increases, the current between the drain and source of the semiconductor switching element increases, and the current flowing through the gate electrode of the semiconductor switching element increases. Since the variation in the voltage between the gate and source of the semiconductor switching element increases, the change amount of the current between the gate and source increases.

[0067] On the other hand, if there are variations in characteristics or the like between the semiconductor switching elements connected in parallel that constitute the switching element, a shift may occur in the switching timing of the semiconductor switching elements connected in parallel. When a shift in the switching timing occurs, a potential difference is generated between the potentials of the drain electrodes or the source electrodes of the semiconductor switching elements connected in parallel, and a current flows through the parasitic capacitance Cds between the drain and source of the semiconductor switching elements connected in parallel. A part of the current flows into the gate electrode through the parasitic capacitance Cgd between the gate and drain and the parasitic capacitance Cgs between the gate and source of the semiconductor switching element, and a current flows between the gate electrodes of the semiconductor switching elements connected in parallel.

[0068] When a current flows between the gate electrodes of the parallel-connected semiconductor switching elements, the voltage between the gate and source of one of the semiconductor switching elements decreases, and the current between the drain and source decreases. The voltage of the gate electrode of the other semiconductor switching element increases, and the current between the drain and source increases in a form driven by the voltage between the gate and source. As a result, a new potential difference occurs between the potentials at the drain electrodes or between the potentials at the source electrodes of the parallel-connected semiconductor switching elements, and the phenomenon in which the potential differences of the parallel-connected semiconductor switching elements alternately reverse is repeated, resulting in gate oscillation.

[0069] This gate oscillation is likely to have a large amplitude because when the voltage between the drain and source of the semiconductor switching element is low, the parasitic capacitance Cds between the drain and source of the semiconductor switching element increases, the current between the drain and source of the semiconductor switching element increases, and the current flowing through the gate electrode of the semiconductor switching element increases. That is, the gate oscillation appears prominently when the voltage between the drain and source of the parallel-connected semiconductor switching elements is low.

[0070] In Embodiment 1, when the input voltage input to the power conversion circuit 10 is lower than the set voltage, the switching time is changed to be shorter than the switching time with respect to the set voltage, so that the gate oscillation generated in the parallel-connected semiconductor switching elements constituting the switching element is likely to oscillate before reaching a large amplitude, that is, it can escape from the switching operation. That is, the semiconductor switching element becomes on state due to a short switching time, and the drain-source of the semiconductor switching element becomes conductive. Therefore, the impedance of the channel portion of the semiconductor switching element becomes lower than the parasitic capacitance Cds between the drain and source of the semiconductor switching element, so that the exchange of charges between the parallel-connected semiconductor switching elements via the parasitic capacitance Cds between the drain and source does not occur, and the gate oscillation converges.

[0071] Therefore, even when the input voltage applied to the power conversion circuit 10 is lower than the set voltage, by changing the switching time to be shorter, gate oscillation in the switching element can be suppressed, and malfunctions of the switching element due to gate oscillation or destruction due to exceeding the breakdown voltage of the semiconductor switching element constituting the switching element can be prevented, and the control of the power conversion circuit 10 will not be lost. Also, when the input voltage applied to the power conversion circuit 10 is lower than the set voltage, since the allowable value of the surge with respect to the breakdown voltage of the semiconductor switching element is large, exceeding the breakdown voltage due to the surge will not occur even if the switching time is shortened.

[0072] In particular, when a wide-bandgap semiconductor element with a high breakdown strength against a high voltage of 1000V is used as the semiconductor switching element constituting each of the switching elements 14u, 15u, 14v, 15v, 14w, and 15w, the wide-bandgap semiconductor has a high transconductance and generally tends to generate an oscillation phenomenon.

[0073] However, in Embodiment 1, since the switching time is changed to be shorter than the switching time with respect to the set voltage for a voltage at which the input voltage applied to the power conversion circuit 10 is lower than the set voltage, it is possible to escape from the switching operation before the gate oscillation reaches a large amplitude, and thus it is possible to prevent the occurrence of destruction due to exceeding the breakdown voltage of the semiconductor switching element. That is, it is suitable for the power conversion circuit 10 using a wide-bandgap semiconductor element as the semiconductor switching element.

[0074] The control circuit unit 30 includes a control signal generation unit 31u for the u-phase, a control signal generation unit 31v for the v-phase, and a control signal generation unit 31w for the w-phase. The control signal generation units 31u, 31v, and 31w for the u-phase, v-phase, and w-phase respectively include the control signal generation units 32u, 32v, and 32w for the high-side arm, the control signal generation units 33u, 33v, and 33w for the low-side arm, the short-circuit detection units 36u, 36v, and 36w for the high-side arm of the u-phase, v-phase, and w-phase, and the short-circuit detection units 37u, 37v, and 37w for the low-side arm of the u-phase, v-phase, and w-phase.

[0075] Since the control signal generation units 31u, 31v, and 31w for the u-phase, v-phase, and w-phase respectively have the same configuration, FIG. 2 shows the control signal generation unit for one phase. In the following description, to avoid complexity, the subscripts u, v, and w of the reference signs are omitted, but the description is for the configurations of the control signal generation unit 31u for the u-phase, the control signal generation unit 31v for the v-phase, and the control signal generation unit 31w for the w-phase respectively.

[0076] The control signal generation unit 31 includes the control signal generation unit 32 for the high-side arm, the control signal generation unit 33 for the low-side arm, the short-circuit detection unit 36 for the high-side arm, and the short-circuit detection unit 37 for the low-side arm. The control signal generation unit 32 for the high-side arm includes a drive voltage generation unit 321 for the high-side arm, an on / off command signal generation unit 322, a gate driver 323, and a gate resistor 324.

[0077] The drive voltage generation unit 321 generates a drive voltage for on, which is an H-level potential for turning on the semiconductor switching elements 14 connected in parallel to the switching element 14 1 , 14 2 , and a drive voltage for off, which is an L-level potential for turning off the semiconductor switching elements 14 1 , 14 2 . The drive voltage generation unit 321 generates the drive voltage for on and the drive voltage for off within the breakdown voltage of the semiconductor switching elements 14 1 , 14 2 . 1 , 14 2The 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, when a wide-bandgap MOSFET is used as the semiconductor switching element 14 1 , 14 2 , the relative amount of the driving voltage for switching is several volts, and the absolute value of the driving voltage after switching is on the order of within several tens of volts. Also, by setting the driving voltage for off to a negative voltage with the opposite potential direction to the driving voltage for on, misfiring arcs of the wide-bandgap MOSFET can be prevented.

[0079] The on / off command signal generation unit 322 generates an on / off command signal that indicates the on-timing to start the on-operation for the semiconductor switching elements 14 1 , 14 2 connected in parallel to the switching element 14 and the off-timing to start the off-operation for the semiconductor switching elements 14 1 , 14 2 .

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

[0081] The gate resistor 324 defines the time taken for the on / off of the semiconductor switching elements 14 1 , 14 2 , that is, the switching time. The semiconductor switching elements 14 1 , 14 2is turned on and off by a control signal for the high side arm from a gate driver 323 whose switching time is regulated 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 parallel-connected semiconductor switching element 14 via the output node 34 of the control signal generating unit 32. 1 , 14 2 When the input voltage input to the power conversion circuit 10 is lower than the set voltage, the resistance value becomes 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, 400V 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 having a switching time shorter than the switching time of the gate resistor 324 is applied from the other terminal of the gate resistor 324 to the semiconductor switching element 14. 1 , 14 2 The gate electrode of the

[0085] The control signal generation unit 33 for the lower side arm includes a drive voltage generation unit 331 for the lower side arm, an on / off command signal generation unit 332, a gate driver 333, and a gate resistor 334. The drive voltage generation unit 331 generates a drive voltage for turning on, which is an H-level potential for turning on the semiconductor switching elements 15 connected in parallel to the switching element 15 1 , 15 2 and a drive voltage for turning off, which is an L-level potential for turning off the semiconductor switching elements 15 1 , 15 2 .

[0086] The drive voltage generation unit 331 is set within a range that does not affect the reliability of the gate structure of the semiconductor switching elements 15 1 , 15 2 within the breakdown voltage of the semiconductor switching elements 15 1 , 15 2 . For example, when wide-bandgap MOSFETs are used as the semiconductor switching elements 15 1 , 15 2 , the relative amount of the drive voltage to be switched is several volts, and the absolute value of the drive voltage after switching is on the order of within several tens of volts. Also, by setting the drive voltage for turning off to a negative voltage with the opposite potential direction to the drive voltage for turning on, misfiring arcs of the wide-bandgap MOSFET can be prevented.

[0087] The on / off command signal generation unit 332 generates an on / off command signal that indicates the on-timing for starting the on-operation and the off-timing for starting the off-operation with respect to the semiconductor switching elements 15 connected in parallel to the switching element 15 1 , 15 2 . 1 , 15 2

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

[0089] The gate resistor 334 defines the time taken for the semiconductor switching element 15 1 , 15 2 to turn on and off, that is, the switching time. The semiconductor switching element 15 1 , 15 2 turns on and off according to the control signal for the low-side arm from the gate driver 333 whose switching time is defined by the 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 electrically connected to the gate electrode of the semiconductor switching element 15, which is connected in parallel to the semiconductor switching element 15 1 , 15 2 via the output node 35 of the control signal generation unit 33. When the input voltage input to the power conversion circuit 10 is lower than the set voltage, the resistance value becomes lower than the resistance value with respect to the set voltage. The gate resistor 334 switches the resistance value according to the output signal of the voltage sensor circuit 40.

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

[0092] That is, when the input voltage applied is lower than the set voltage and the resistance value is switched to a resistance value lower than the set value, a control signal having a switching time shorter than the switching time of the semiconductor switching element 15 1 15 2 at the time when the resistance value is the set value is output from the other terminal of the gate resistor 334 to the gate electrode of the semiconductor switching element 15 1 15 2 .

[0093] The short - circuit detection unit 36 for the high - side detects a short - circuit when the series - connected switching element 14 and the switching element 15 in the half - bridge circuit 13 simultaneously enter the conducting state due to an erroneous arcing of the switching element 15 or the like and enter the short - circuit state, 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 generation unit 322 outputs a potential of the L level, which is a driving voltage for off, to the voltage output node OUT with respect to the gate driver 323, and forcibly changes the switching element 14 from the conducting state to the non - conducting state. The semiconductor switching element 14 1 14 2 constituting the switching element 14 is turned off, the short - circuit current is cut off, and the switching element 14 and the switching element 15 are protected from the short - circuit.

[0095] ​​​​​​​​​​​​​The short - circuit detection unit 37 for the low side detects a short - circuit when the serially - connected switching element 14 and switching element 15 in the half - bridge circuit 13 simultaneously enter a conducting state due to, for example, misfiring of the switching element 14, 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 generation unit 332 outputs a potential of the L level, which is a driving voltage for off, to the voltage output node OUT with respect to the gate driver 333, and forces the switching element 15 from the conducting state to the non - conducting state. The semiconductor switching element 15 that constitutes the switching element 15 1 、15 2 is turned off, the short - circuit current is cut off, and the switching element 14 and the switching element 15 are protected from the short - circuit.

[0097] The short - circuit detection unit 36 monitors the voltage between the drain and source of the switching element 14 to determine whether the switching element 14 and the switching element 15 are in a short - circuit state. When it is determined that they are in a short - circuit state, it outputs an off command signal to the on - off command signal generation unit 322, and adopts a configuration of the DESAT method. The short - circuit detection unit 37 monitors the voltage between the drain and source of the switching element 15 to determine whether the switching element 14 and the switching element 15 are in a short - circuit state. When it is determined that they are in a short - circuit state, it outputs an off command signal to the on - off command signal generation unit 332, and adopts a configuration of the DESAT method.

[0098] By the short - circuit detection unit 36 and the short - circuit detection unit 37 adopting the DESAT method, even when a wide - bandgap semiconductor element, which requires maximizing the area available for use 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 the semiconductor switching element 15 1 、15 2 it is possible to perform short - circuit protection at low cost.

[0099] The short - circuit detection units 36 and 37 have the same configuration. As shown in FIG. 3 respectively, they are each composed of a DESAT - type circuit having a comparator 361, 371, a threshold - value generation source 362, 372, resistors 363, 373, diodes 364, 374, constant - current sources 365, 375, switches 366, 376, and capacitors 367, 377. In the description of the components of the short - circuit detection units 36 and 37, reference numerals are listed to avoid redundant explanations. Here, 36※ represents the components of the short - circuit detection unit 36, and 37※ represents the components of the short - circuit detection unit 37.

[0100] One input terminal of the comparators 361, 371 is electrically connected to the short - circuit detection nodes 368, 378, the other input terminal is electrically connected to the threshold - value generation sources 362, 372, and the output terminal is electrically connected to the on - off command signal generation units 322, 332. When the potential appearing at the short - circuit detection nodes 368, 378 is greater than the threshold value by the threshold - value generation sources 362, 372, it is determined that the switching elements 14, 15 are in a short - circuit state, and an off - command signal is output to the output terminal.

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

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

[0103] During normal operation when the switching elements 14 and 15 are not in a short - circuit state, when the switching element 14 turns on and the switching element 15 turns off, after the short - circuit detection time has elapsed, the voltage between the drain and source of the switching element 14 becomes lower than the threshold value by the threshold value generation source 362.

[0104] The mask time designation signal indicates the elapse of the mask time. Although the capacitor 367 starts to be charged by the constant current from the constant current source 365 after the mask time has elapsed, it is set such that discharging to the drain terminal of the switching element 14 via the series combination of the resistor 363 and the diode 364 discharges more than charging the capacitor 367. Therefore, after the short - circuit detection time has elapsed, the potential of the short - circuit detection node 368 does not exceed the threshold value. As a result, an off command signal is not output from the comparator 361.

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

[0106] The mask time designation signal indicates the elapse of the mask time. When the capacitor 367 starts to be charged by the constant current from the constant current source 365, since there is no discharge to the drain terminal of the switching element 14 via the series combination of the resistor 363 and the diode 364, after the short - circuit detection time has elapsed, the potential of the short - circuit detection node 368 becomes a potential exceeding the threshold value. As a result, an off command signal is output from the comparator 361, and the control signal generation unit 32 that has received the off command signal causes the semiconductor switching element 14 that constitutes the switching element 14 1 , 14 2 to be forcibly turned off from the conducting state, cutting off the short-circuit current and protecting the switching element 14 and the switching element 15 from the short circuit.

[0107] During normal operation when the short-circuit detection unit 37 ensures that the switching element 14 and the switching element 15 do not enter a short-circuit state, when the switching element 15 turns on and the switching element 14 turns off, 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 by the threshold value generation source 372.

[0108] The mask time designation signal indicates the elapse of the mask time. After the mask time has elapsed, the capacitor 377 starts to be charged by the constant current from the constant current source 375. However, it is set such that more charge is discharged to the drain terminal of the switching element 15 through the series combination of the resistor 373 and the diode 374 than the capacitor 377 is charged. Therefore, the potential of the 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 the comparator 371.

[0109] On the other hand, when the switching element 14 and the switching element 15 enter a short-circuit state, that is, when the switching element 15 is in the conducting state and the switching element 14 starts to turn on due to an accidental arc or the like, even after the short-circuit detection time has elapsed, since the switching element 15 is in the conducting state and the switching element 14 is in the conducting state due to an accidental arc or the like, the voltage between the drain and source of the switching element 15 is higher than the threshold value by the threshold value generation source 372.

[0110] When the mask time specifying signal indicates the elapse of the mask time and the capacitor 377 starts to be charged by the constant current from the constant current source 375, since it is not discharged to the drain terminal of the switching element 15 through the series combination of the resistor 373 and the diode 374, after the short - circuit detection time has elapsed, the potential of the short - circuit detection node 378 becomes a potential exceeding the threshold value. As a result, an off command signal is output from the comparator 371, and by the control signal generation unit 33 that has received the off command signal, the semiconductor switching element 15 that constitutes the switching element 15 1 , 15 2 is forcibly turned off from the conductive state, the short - circuit current is interrupted, and the switching element 14 and the switching element 15 are protected from the short - circuit.

[0111] The short - circuit detection time is set with the starting point being the time when the gate potentials of the switching elements 14 and 15 rise, that is, the time when the gate - source voltage starts to rise. 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 currents from the constant current sources 365 and 375 and the potentials of the short - circuit detection nodes 368 and 378 reach the threshold value in the normal state. The short - circuit detection time should be as short as possible so that the short - circuit can be detected promptly. The short - circuit detection time is interlocked with the switching times of the switching elements 14 and 15.

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

[0113] In Embodiment 1, switches 366 and 376 are turned off by a mask time designation signal until the mask time elapses, and when the mask time elapses, switches 366 and 376 are turned on by the mask time designation signal. The comparator 361 and 371 determine the short-circuit state of the switching element 14 and the switching element 15 in a short-circuit detection time (= mask time + charging time of the capacitors 367 and 377 until the threshold value).

[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 to the control circuit unit 30 according to the detected input voltage. The control circuit unit 30 outputs a control signal corresponding 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 resistance 324 of the control signal generation unit 32 for the high-side arm and the gate resistance 334 of the control signal generation unit 33 for the low-side arm in the control circuit unit 30 that receives the output signal from the voltage sensor circuit 40 change their resistance values according to the output signal from the voltage sensor circuit 40.

[0116] In Embodiment 1, the output signal from the voltage sensor circuit 40 consists of a signal indicating a high voltage in the range of 1000V, which is the set voltage, when the input voltage input to the power conversion circuit 10 exceeds 400V, and a signal indicating a low voltage of 400V or less. The gate resistance 324 and the gate resistance 334 are respectively set to a resistance value with respect to the set voltage when the output signal from the voltage sensor circuit 40 is a signal indicating a high voltage, and are switched to a resistance value lower than the resistance value with respect to the set voltage when it 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 with respect to the set voltage, when one of the switching elements 14 and 15 turns on and the other turns off, the voltage between the drain and source of the switching element 14 or 15 that turns on at the end of the short - circuit detection time is less than the short - circuit detection threshold value, and the short - circuit detection units 36 and 37 do not detect a short - circuit. That is, the resistance values of gate resistors 324 and 334 with respect to the set voltage are set to values that become control signals for a switching time when the input voltage is high and the voltage between the drain and source of the switching elements 14 and 15 is less than the short - circuit detection threshold value at the end of the short - circuit detection time.

[0118] On the other hand, when the input voltage is low and the gate resistors 324 and 334 have resistance values lower than the resistance values with respect to the set voltage, when one of the switching elements 14 and 15 turns on and the other turns off, the switching time of the switching element 14 or 15 that turns on is shorter than the switching time of the switching element 14 or 15 that turns on when the gate resistors 324 and 334 have resistance values with respect to the set voltage, and it is in a state where it is easy to oscillate before the gate oscillation generated in the switching element 14 or 15 that turns on reaches a large amplitude, that is, it can escape from the switching operation. That is, the resistance values of gate resistors 324 and 334 with respect to the set voltage are set to values that become control signals for a switching time that suppresses gate oscillation when the input voltage is low.

[0119] In short, when the input voltage applied to the power conversion circuit 10 is the set voltage, a control signal is output from the control signal generation units 32 and 33 in the control circuit unit 30, and the switching times of the switching elements 14 and 15 to be turned on are set to switching times at which false detection of a short circuit does not occur at the end of the short circuit detection time. When the input voltage applied to the power conversion circuit 10 is a low voltage less than the set voltage, a control signal is output from the control signal generation units 32 and 33 in the control circuit unit 30, and the switching times of the switching elements 14 and 15 to be turned on are changed to switching times that suppress gate oscillation.

[0120] Incidentally, without changing the switching time according to the input voltage, the operation during normal operation when gate oscillation is suppressed at a low voltage will be described with reference to FIG. 5. That is, it is assumed that when the input voltage is a low voltage, the resistance values of the gate resistors 324 and 334 are set to low values, respectively, and a control signal that becomes a switching time for suppressing gate oscillation is output from the control signal generation units 32 and 33 in the control circuit unit 30. Also when the input voltage is a high voltage, a control signal with the same resistance values of the gate resistors 324 and 334 as in the case of a low voltage is output from the control signal generation units 32 and 33 in the control circuit unit 30.

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

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

[0123] When a MOSFET is used as the semiconductor switching element, due to the 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 during switching of the semiconductor switching element, becomes longer depending on the input voltage compared to when the input voltage is low. As a result, 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 becomes a switching time for suppressing gate oscillation when the input voltage is at a low voltage is input to the switching element 15 during the ON operation of the switching element 15 even when the input voltage is at a high voltage, as shown in FIG. 5, since the switching time of the switching element 15 is long, the ON operation is not completed even at the end of the short-circuit detection time, the voltage between the drain and source of the switching element 15 exceeds the short-circuit detection threshold value, and false detection of a short circuit occurs.

[0125] Note that the short-circuit detection time is shortened in order to quickly detect a short circuit when the input voltage is at a low voltage, and usually, the same short-circuit detection time as when the input voltage is at a low voltage is used even when the input voltage is at a high voltage, so it becomes shorter. The same applies during the ON operation of the switching element 14, and false detection of a short circuit occurs when the input voltage is at a high voltage.

[0126] On the other hand, in the power conversion device 300 according to the first embodiment, when the input voltage is at a high voltage, during the ON operation of the switching element 15, the control signal generation unit 33 in the control circuit unit 30 outputs a control signal that becomes a switching time at which the voltage between the drain and source of the switching element 15 is less than the short-circuit detection threshold value at the end of the short-circuit detection time, and when the input voltage is at a low voltage, during the ON operation of the switching element 15, the control signal from the control signal generation unit 33 in the control circuit unit 30 is changed, and a control signal that becomes a switching time for suppressing gate oscillation is output to the switching element 15.

[0127] As a result, the power conversion device according to the first embodiment prevents the occurrence of overvoltage due to surge in the switching element 15 when the input voltage is at a high voltage, has no false detection of a short circuit, and can also prevent malfunction of the switching element 15 due to gate oscillation or overvoltage of the switching element 15 when the input voltage is at a low voltage. The same applies during the ON operation of the switching element 14.

[0128] Next, in the power conversion device according to Embodiment 1, when the switching element 14 and the switching element 15 are simultaneously turned on due to an arc fault or the like in the switching element 14 or the switching element 15 and a short-circuit state occurs, this will be described with reference to FIG. 4. FIG. 4 shows the waveforms of the operation in which when the switching element 14 (high-side arm) is in the conducting state and the switching element 15 (low-side arm) is in the non-conducting state, the switching element 15 accidentally turns on due to some factor, the short-circuit detection unit 36 for the high side detects that the switching element 14 and the switching element 15 are in the short-circuit state, outputs an off command signal to the on / off command signal generation unit 322 for the high side, and the control signal generation unit 32 turns off the switching element 14 for short-circuit protection.

[0129] In FIG. 4, the horizontal axis represents time, the solid line shows the waveform when the input voltage is high voltage, which is 1000V in Embodiment 1, and the dashed line shows the waveform when the input voltage is low voltage, which is 400V in Embodiment 1. Note that since FIG. 4 is a diagram for explaining the phenomenon generated due to the difference in switching time, the vertical axis direction is the same for both the case of high input voltage and the case of low input voltage.

[0130] The switching element 15 accidentally starts the on operation at time t 00 That is, the voltage between the gate and source of the switching element 15 starts to rise. The short-circuit detection time starting from the on-operation start time of the switching element 15 begins. When the input voltage is high, the voltage between the gate and source of the switching element 15 is such that the resistance value of the gate resistor 334 in the control signal generation unit 33 for the low-side arm is high, and a control signal with a long switching time is input to the gate electrode of the switching element 15, so the voltage rises gently and the state where the resistance value between the drain and source in the switching element 15 is large continues.

[0131] When the input voltage is high, the voltage between the drain and source of the switching element 15 remains high because the resistance value between the drain and source of the switching element 15 is large. Therefore, the short-circuit current flowing through the switching element 14 and the switching element 15 changes slowly until it reaches its peak, and then decreases from the peak towards zero.

[0132] On the other hand, the voltage between the drain and source of the switching element 14 is determined by the voltage between the drain and source of the switching element 15 when the switching element 14 and the switching element 15 are in a short-circuit state. When the input voltage is high, the voltage between the drain and source of the switching element 15 remains high because the resistance value between the drain and source of the switching element 15 is large, so the change is slow. If the voltage between the drain and source 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.

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

[0134] When the input voltage is high, the resistance value of the gate resistor 324 in the control signal generation unit 32 for the high-side arm is high, and a control signal with a long switching time is input to the gate electrode of the switching element 14. Therefore, the time until the switching element 14 turns off is long. At this time, the switching time of the switching element 15 is the time it takes for the switching element 15 to turn on from off, and the switching time of the switching element 14 is the time it takes for the switching element 14 to turn off from on. The switching times of the switching element 14 and the switching element 15 correspond to the time starting from the point when the short-circuit current (through current) flowing through the switching element 14 and the switching element 15 starts to flow and ending at the point when it stops flowing.

[0135] When the input voltage is high, although the switching element 15 repeats gate oscillation many times, the voltage between the drain and source of the switching element 15 is high, and moreover, the switching time is long, and the rise of the voltage between the gate and source of the switching element 15 is slow. Therefore, even when the switching element 14 and the switching element 15 are simultaneously turned on due to an error arc or the like of the switching element 15 and enter a short-circuit state, it is possible to prevent the occurrence of overvoltage due to a surge. The same applies even when the switching element 14 and the switching element 15 are simultaneously turned on due to an error arc or the like of the switching element 14 and enter a short-circuit state.

[0136] Also, when the input voltage is low, the voltage between the gate and source of the switching element 15 is changed to a lower resistance value of the gate resistor 334 in the control signal generation unit 33 for the low-side arm. Therefore, a control signal with a shorter switching time is input to the gate electrode of the switching element 15, so the rise is fast and the time until the switching element 15 turns on is short.

[0137] The voltage between the drain and source of the switching element 15 is lower earlier because the switching time of the switching element 15 is shorter when the input voltage is low, and the voltage between the drain and source of the switching element 15 drops quickly. Since the resistance value between the drain and source of the switching element 15 becomes low quickly, the voltage between the drain and source of the switching element 14, which is determined by the voltage between the drain and source of the switching element 15 when the switching element 14 and the switching element 15 are in a short-circuit state, changes, that is, drops quickly when the input voltage is low.

[0138] When the voltage between the drain and source of the switching element 14 exceeds the short-circuit detection threshold value 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 switching element 14 starts to turn off by the control signal generation unit 32.

[0139] When the input voltage is low, the resistance value of the gate resistor 324 in the control signal generation unit 32 for the high-side arm is low, and a control signal with a shorter switching time is input to the gate electrode of the switching element 14. Therefore, the time until the switching element 14 turns off is short. That is, the time for interrupting the short-circuit current of the switching element 14 and the switching element 15 becomes shorter.

[0140] At this time, the switching time of the switching element 15 is the time from when the switching element 15 turns off to when it turns on, and the switching time of the switching element 14 is the time from when it turns on to when it turns off. The switching times of the switching element 14 and the switching element 15 correspond to the time starting from the point when the short-circuit current flowing through the switching element 14 and the switching element 15 starts to flow and ending at the point when it stops flowing.

[0141] When the input voltage is low, the switching element 15 can complete the switching operation of the switching element 15 before the number of gate oscillations repeats and the vibration due to the gate oscillation becomes significant. Even when the switching element 14 and the switching element 15 are simultaneously turned on due to an arc error of the switching element 15 or the like and enter a short-circuit state, the gate oscillation of the switching element 15 is suppressed. The same applies even when the switching element 14 and the switching element 15 are simultaneously turned on due to an arc error of the switching element 14 or the like and enter a short-circuit state.

[0142] In short, in the power conversion device 300 according to Embodiment 1, even when the switching elements 14 and 15 are simultaneously turned on and short-circuited due to an arc failure of the switching element 14 or the switching element 15, if the input voltage input to the power conversion circuit 10 is the set voltage, the switching times of the switching elements 14 and 15 are the switching times at which false detection of short-circuit detection does not occur at the end of the short-circuit detection time. As a result, a control signal set to the time starting from the point when the short-circuit current flowing through the switching element 14 and the switching element 15 starts to flow and ending at the point when it stops flowing is output from the control signal generation units 32 and 33 in the control circuit unit 30 and input to the power conversion circuit 10. If the input voltage input to the power conversion circuit 10 is a low voltage less than the set voltage, the switching times of the switching elements 14 and 15 are changed to the switching times that suppress gate oscillation. As a result, a control signal set to the time starting from the point when the short-circuit current flowing through the switching element 14 and the switching element 15 starts to flow and ending at the point when it stops flowing is output from the control signal generation units 32 and 33 in the control circuit unit 30.

[0143] Incidentally, without changing the switching time according to the input voltage, the operation when the switching elements 14 and 15 are simultaneously turned on and short-circuited due to an arc failure of the switching element 15 or the like to prevent the occurrence of breakdown voltage exceeding due to a surge at a high voltage will be described with reference to FIG. 6 for reference.

[0144] In FIG. 6, the horizontal axis represents time. The solid line indicates the waveform when the input voltage is a high voltage, 1000V in Embodiment 1, and the dashed line indicates the waveform when the input voltage is a low voltage, 400V in Embodiment 1. t00 is the time when the short-circuit current flowing through the switching elements 14 and 15 starts to flow, and t01 is the time when the short-circuit current becomes 0. The time from time t00 to time t01 corresponds to the switching times of the switching elements 14 and 15.

[0145] When the input voltage is high, the operation is the same as that described in FIG. 4, so the description is omitted. Hereinafter, the case where the input voltage is low will be described. The voltage between the gate and source of the switching element 15 is the same as in the case where the input voltage is high. Since the resistance value of the gate resistor 334 in the control signal generation unit 33 for the low-side arm is high and a control signal with a long switching time is input to the gate electrode of the switching element 15, it rises gently, and the resistance value between the drain and source in the switching element 15 remains large.

[0146] The voltage between the drain and source of the switching element 15 is the same as in the case where the input voltage is high. Since the resistance value between the drain and source of the switching element 15 remains large, the short-circuit current flowing through the switching element 14 and the switching element 15 changes slowly until it reaches the peak, and the short-circuit current decreases from the peak towards 0.

[0147] On the other hand, the voltage between the drain and source of the switching element 14 is determined by the voltage between the drain and source of the switching element 15 when the switching element 14 and the switching element 15 are in a short-circuit state. The resistance value between the drain and source of the switching element 15 remains large, so the change is slow. When the voltage between the drain and source of the switching element 14 exceeds the short-circuit detection threshold value after the short-circuit detection time has elapsed, the 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 turn 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 element 14 and the switching element 15 reaches the peak, and rises towards the input voltage from the time when the short-circuit current reaches the peak.

[0149] When the input voltage is high, the voltage between the gate and source of the switching element 14 is the same as before. The resistance value of the gate resistor 324 in the control signal generation unit 32 for the high-side arm is high, and a control signal with a long switching time is input to the gate electrode of the switching element 14. Therefore, the time until the switching element 14 turns off is long.

[0150] Since the voltage between the drain and source of the switching element 15 is held at a low voltage for a long time, when a short-circuit state occurs, the number of times of gate oscillation repetition is large, the vibration due to gate oscillation becomes prominent, and there is a risk of malfunction of the switching element or breakdown due to exceeding the withstand voltage of the semiconductor switching element.

[0151] On the other hand, in the power conversion device 300 according to the first embodiment, when the input voltage is high, at the end of the short-circuit detection time during the on-operation of the switching element 15, the control signal generation unit 33 in the control circuit unit 30 outputs a control signal with a switching time such that the voltage between the drain and source of the switching element 15 becomes less than the short-circuit detection threshold value. When the input voltage is low, during the on-operation of the switching element 15, the control signal from the control signal generation unit 33 in the control circuit unit 30 is changed, and a control signal with a switching time that suppresses gate oscillation is output to the switching element 15.

[0152] As a result, the power conversion device according to the first embodiment prevents the occurrence of exceeding the withstand voltage due to surge for the switching element 15 when the input voltage is high, has no false detection of short circuit, and when the input voltage is low, it can also prevent malfunction of the switching element 15 due to gate oscillation or exceeding the withstand voltage of the switching element 15. The same applies during the on-operation of the switching element 14.

[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 1000V, for example, an output signal indicating 400V, the gate resistors 324 of the control signal generation unit 32 for the high-side arm and the gate resistors 334 of the control signal generation unit 33 for the low-side arm in the control circuit unit 30 of the power conversion circuit 10 are switched to a resistance value lower than the set value, and a plurality of semiconductor switching elements 14 in the semiconductor switching element group constituting the switching elements 14 and 15 1 、14 2 、15 1 、15 2 have a switching time shorter than the set time. Therefore, when the input voltage input to the power conversion circuit 10 is the set voltage, destruction due to exceeding the withstand voltage of a plurality of semiconductor switching elements 14 1 、14 2 、15 1 、15 2 is suppressed, and when the input voltage input to the power conversion circuit 10 is a voltage lower than the set voltage, gate oscillation during turn-on of a plurality of semiconductor switching elements 14 1 、14 2 、15 1 、15 2 can be suppressed.

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

[0155] Embodiment 2. The power conversion device according to the second embodiment will be described with reference to FIG. 7. The power conversion device 300 according to Embodiment 2 controls the switching time by changing the resistance values of the gate resistors 324 of the control signal generation unit 32 for the high-side arm and the gate resistors 334 of the control signal generation unit 33 for the low-side arm in the control circuit unit 30 according to the input voltage input to the power conversion circuit 10, whereas the switching time is controlled by changing at least one of the drive voltages for turning on and turning off the semiconductor switching elements in the drive voltage generation unit 321 of the control signal generation unit 32 for the high-side arm and the drive voltage generation unit 331 of the control signal generation unit 33 for the low-side arm in the control circuit unit 30 according to the input voltage input to the power conversion circuit 10. Other aspects are the same as those of the power conversion device 300 according to Embodiment 1. Note that the resistance values of the gate resistor 324 and the gate resistor 334 are the same regardless of the input voltage input to the power conversion circuit 10. Also, in FIG. 7, the same reference numerals as those attached to FIGS. 1 to 3 indicate 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 Embodiment 2 changes the on-drive voltage to a value higher than the on-drive voltage for the set voltage, changes the off-drive voltage to a value lower than the off-drive voltage for the set voltage, and significantly switches the absolute value of the off-drive voltage. When the on-drive voltage is high, the rising speed of the gate-source voltage of the semiconductor switching element increases, and when the off-drive voltage is low, the falling speed of the gate-source voltage of the semiconductor switching element increases. As a result, the switching time for the semiconductor switching element can be shortened.

[0157] As shown in FIG. 7, the drive voltage generation unit 321 sets the on-drive voltage and the off-drive voltage to set values based on the output signal indicating the set voltage indicating the high voltage from the voltage sensor circuit 40, and the semiconductor switching element 14 1 , 14 2Set the switching time of [semiconductor switching element 14] as the set time. When the input voltage applied to the power conversion circuit 10 is lower than the set voltage, an output signal indicating a voltage lower than the set voltage from the voltage sensor circuit 40 causes the drive voltage for turning on to be switched to a drive voltage higher than the set value, and the drive voltage for turning off to be switched to a drive voltage lower than the set value. As a result, the switching time of the semiconductor switching element 14 1 、14 2 is set to a time shorter than the set time.

[0158] As shown in FIG. 7, the drive voltage generation unit 331 sets the drive voltage for turning on and the drive voltage for turning off to the set values by an output signal indicating the set voltage indicating a high voltage from the voltage sensor circuit 40, and the semiconductor switching element 15 1 、15 2 has its switching time set to the set time. When the input voltage applied to the power conversion circuit 10 is lower than the set voltage, an output signal indicating a voltage lower than the set voltage from the voltage sensor circuit 40 causes the drive voltage for turning on to be switched to a drive voltage higher than the set value, and the drive voltage for turning off to be switched to a drive voltage lower than the set value. As a result, the switching time of the semiconductor switching element 15 1 、15 2 is set to a time shorter than the set time.

[0159] When a wide-bandgap MOSFET is used as the semiconductor switching element 14 1 、14 2 , the MOSFET performs a high-speed switching operation. Therefore, the transition speed dv / dt of the voltage between the drain and source during switching is large, and the parasitic capacitance Cgs is charged by the current flowing through the gate of the MOSFET generated by the parasitic capacitance Cdg×dv / dt, causing the voltage between the gate and source to rise and making it easy to cause false arcing. However, when the drive voltage for turning off is a negative voltage with the opposite potential direction to the drive voltage for turning on, and when the input voltage applied to the power conversion circuit 10 is lower than the set voltage, the drive voltage for turning off is switched to a much lower drive voltage, so that the MOSFET can have a switching time shorter than the set time without generating false arcing.

[0160] In the power conversion device 300 according to Embodiment 2, an output signal indicating that the input voltage input to the power conversion circuit 10 is lower than the set voltage causes the drive voltage generation unit 321 of the control signal generation unit 32 for the high-side arm and the drive voltage generation unit 331 of the control signal generation unit 33 for the low-side arm in the control circuit unit 30 of the power conversion circuit 10 to change the on-drive voltage of the semiconductor switching element to be higher than the set voltage of the on-gate, or change the off-drive voltage to be lower than the set voltage of the off-gate, or switch the on-drive voltage to be higher and the off-drive voltage to be lower. A plurality of semiconductor switching elements 14 in the semiconductor switching element group constituting the switching elements 14 and 15 1 、14 2 、15 1 、15 2 The switching time of is changed to be shorter than the set time. When the input voltage input to the power conversion circuit 10 is at the set voltage, a plurality of semiconductor switching elements 14 1 、14 2 、15 1 、15 2 、15 1 、14 2 、15 1 、15 2 The occurrence of breakdown due to exceeding the withstand voltage is suppressed, and gate oscillation during turn-on of a plurality of semiconductor switching elements 14

[0161] Note that when the power conversion device 300 according to Embodiment 2 is used as a power conversion device for an electric power train such as a hybrid vehicle or an electric vehicle, a lead-acid battery that is a DC power source for operating auxiliary devices of the hybrid vehicle or the electric vehicle is used as the DC power source 100, and a flyback power supply with the voltage supplied from the lead-acid battery as the input as the drive power source of the control circuit unit 30 may be used as the drive voltage generation unit 321 and the drive voltage generation unit 331. By using flyback power supplies as the drive voltage generation unit 321 and the drive voltage generation unit 331 in this way, it is possible to change the drive voltage by changing the duty ratio of the flyback power supply according to the output signal from the voltage sensor circuit 40.

[0162] Embodiment 3. The power conversion device according to Embodiment 3 will be described with reference to FIG. 8. The power conversion device 300 according to Embodiment 3 is different from the power conversion device according to Embodiment 1 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 according to the input voltage input to the power conversion circuit 10, and the other points are the same as those of the power conversion device 300 according to Embodiment 1. In FIG. 8, the same reference numerals as those attached to FIGS. 1 to 3 indicate the same or corresponding parts.

[0163] 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 Embodiment 3 switches the short-circuit detection times in the short-circuit detection unit 36 and the short-circuit detection unit 37 to be shorter. When the input voltage is lower than the set voltage and the short-circuit detection time is shortened, the short-circuit time between the switching element 14 and the switching element 15 becomes shorter, so the number of times of repeating the gate oscillation is small and the switching operation of the switching element 15 can be completed before the vibration due to the gate oscillation becomes significant.

[0164] In the short-circuit detection unit 36 and the short-circuit detection unit 37 in the power conversion device 300 according to Embodiment 3, for example, when the input voltage is a high voltage, it is set to the short-circuit detection time at which short-circuit detection can be performed at the time indicated by short-circuit detection (gate resistance: large), and when the input voltage is a low voltage, it is set to the short-circuit detection time at which short-circuit detection can be performed at the time indicated by short-circuit detection (gate resistance: large). Both short-circuit detection times are times when no false short-circuit detection occurs when the switching element 14 and the switching element 15 are operating normally. That is, when the switching element 14 and the switching element 15 are turned on by normal operation, the voltage between the drain and source of the switching element 14 and the voltage between the drain and source 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, if the switching element 14 is in a conductive state and the switching element 15 is in a non-conductive state, and if the switching element 15 accidentally turns on due to some factor, the short-circuit detection unit 36 for the high side determines that the switching element 14 and the switching element 15 are in a short-circuit state and outputs an off command signal to the on / off command signal generation unit 322 for the high side when a shorter short-circuit detection time has elapsed, and the control signal generation unit 32 starts an operation to turn off the switching element 14 for short-circuit protection.

[0166] Therefore, since the switching element 14 starts the off operation earlier, the short-circuit time between the switching element 14 and the switching element 15 becomes shorter, and the switching operation of the switching element 15 can be completed before the vibration due to gate oscillation becomes significant. The same applies when the switching element 14 accidentally turns on.

[0167] Also in the power conversion device 300 according to the third embodiment, the switching time of the switching element 15 is the time taken for the switching element 15 to turn on from off, the switching time of the switching element 14 is the time taken for the switching element 14 to turn off from on, and the switching times of the switching element 14 and the switching element 15 correspond to the time with the start point being the time when the short-circuit current (through current) flowing through the switching element 14 and the switching element 15 starts to flow and the end point being the time when it stops flowing.

[0168] Similar to Embodiment 1, as shown in FIG. 3, the short-circuit detection units 36 and 37 are configured by a DESAT method circuit, and at least one of the mask time of the mask time designation signal, the current values of the constant current sources 365 and 375, the threshold values by the threshold value generation sources 362 and 372, the capacitance values of the capacitors 367 and 377, and the resistance values of the resistors 363 and 373 is variable. The switching for shortening the short-circuit detection time is to shorten the mask time of the mask time designation signal input to the switches 366 and 396, increase the current values of the constant current sources 365 and 375, lower the threshold values by the threshold value generation sources 362 and 372, reduce the capacitance of the capacitors 367 and 377, or increase the resistance values of the resistors 363 and 373, or any combination thereof.

[0169] In short, when the input voltage input to the power conversion circuit 10 is lower than the set voltage, the power conversion device 300 according to Embodiment 3 uses an output signal indicating a voltage lower than the set voltage of the input voltage input to the power conversion circuit 10 to switch the short-circuit detection time until the short-circuit detection unit 36 outputs an off command signal to be shorter. When there is a short circuit between the switching element 14 and the switching element 15, the short-circuit time between the switching element 14 and the switching element 15 is shortened, and more reliably, a plurality of semiconductor switching elements 14 1 、14 2 、15 1 、15 2 The gate oscillation during incorrect turn-on can be suppressed.

[0170] Note that, similar to that shown in Embodiment 3, for the power conversion device according to Embodiment 2, 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 according to the input voltage input to the power conversion circuit 10. Even in the power conversion device configured as described above, more reliably, a plurality of semiconductor switching elements 14 1 、14 2 、15 1 、15 2 The gate oscillation during incorrect turn-on can be suppressed.

[0171] In addition, free combinations of each embodiment, modifications of any component of each embodiment, or omissions of any component of each embodiment are possible.

Industrial Applicability

[0172] The power conversion device according to the present disclosure is preferably applied to a power conversion device for an electric power train such as a hybrid vehicle or an electric vehicle, for example, an inverter or a converter for high power.

Explanation of Signs

[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 section, 31u u-phase control signal generation section, 31v v-phase control signal generation section, 31w w-phase control signal generation section, 32u, 32v, 32w Control signal generation section for high-side arm, 33u, 33v, 33w Control signal generation section for low-side arm, 36u, 36v, 36w Short-circuit detection section for high-side arm of u-phase, v-phase, w-phase, 37u, 37v, 37w Short-circuit detection section for low-side arm of u-phase, v-phase, w-phase, 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 having a semiconductor switching element group in which each has a control terminal and a plurality of semiconductor switching elements are connected in parallel; a control circuit unit that changes the switching times of a plurality of semiconductor switching elements in the semiconductor switching element group according to an input voltage input to the power conversion circuit, and outputs a control signal for on / off controlling 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; A power conversion device comprising the above.

2. The power conversion circuit includes a half-bridge circuit having a low-side arm and a high-side arm, the semiconductor switching element group in the power conversion circuit is arranged in each of the low-side arm and the high-side arm in the half-bridge circuit, the control signal output from the control circuit unit is a control signal for the low-side arm and a control signal for the high-side arm arranged in each of the low-side arm and the high-side arm in the half-bridge circuit, The power conversion device according to Claim 1.

3. The power source is a DC power source composed 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 have a low-side arm and a high-side arm, the semiconductor switching element group in the power conversion circuit is arranged in each of the low-side arm and the high-side arm in the u-phase inverter section, the low-side arm and the high-side arm in the v-phase inverter section, and the low-side arm and the high-side arm in the w-phase inverter section; The control signal output from the control circuit unit is a control signal for the low-side arm and a control signal for the high-side arm for the u-phase, a control signal for the low-side arm and a control signal for the high-side arm for the v-phase, and a control signal for the low-side arm and a control signal for the high-side arm for the w-phase, corresponding to each of the groups of semiconductor switching elements arranged in the low-side arm and the high-side arm of the inverter unit for each of the u-phase, v-phase, and w-phase, respectively. The power conversion device according to claim 1.

4. The inverter unit for the u-phase has a structure of a power module in which a group of semiconductor switching elements arranged in the low-side arm and a group of semiconductor switching elements arranged in the high-side arm are molded in the same package. The group of semiconductor switching elements arranged in the low-side arm has a gate terminal for the low-side arm to which the gate electrodes 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. The group of semiconductor switching elements arranged in the high-side arm has a gate terminal for the high-side arm to which the gate electrodes 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 inverter section of the V-phase has a structure of a power module in which a group of semiconductor switching elements arranged on the low-side arm and a group of semiconductor switching elements arranged on the high-side arm are molded in the same package. The group of semiconductor switching elements arranged on the low-side arm has a gate terminal for the low-side arm to which the gate electrodes of the plurality of semiconductor switching elements 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. The group of semiconductor switching elements arranged on the high-side arm has a gate terminal for the high-side arm to which the gate electrodes of the plurality of semiconductor switching elements 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 inverter section of the W-phase has a structure of a power module in which a group of semiconductor switching elements arranged on the low-side arm and a group of semiconductor switching elements arranged on the high-side arm are molded in the same package. The group of semiconductor switching elements arranged on the low-side arm has a gate terminal for the low-side arm to which the gate electrodes of the plurality of semiconductor switching elements 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. The group of semiconductor switching elements arranged on the high-side arm has a gate terminal for the high-side arm to which the gate electrodes of the plurality of semiconductor switching elements 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 power conversion device according to claim 3.

5. The 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-bandgap semiconductor element.

6. The 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-bandgap metal oxide semiconductor field effect transistor.

7. The change in the switching time by the control signal output from the control circuit unit is a change that shortens the switching time when the input voltage input to the power conversion circuit is lower than the set voltage. The power conversion device according to any one of claims 1 to 4.

8. The change in the switching time by the control signal output from the control circuit unit is a change that shortens the switching time in multiple steps toward the range where the input voltage becomes lower corresponding to the voltage range in which the input voltage input to the power conversion circuit is divided into multiple steps. The power conversion device according to any one of claims 1 to 4.

9. Each of the plurality of semiconductor switching elements in the semiconductor switching element group is a wide bandgap semiconductor element. The power conversion device according to claim 7.

10. The change in the switching time by the control signal output from the control circuit unit is performed by changing the resistance value according to the input voltage input to the power conversion circuit, and changing the resistance value of the gate resistance that defines the switching time of the plurality of semiconductor switching elements in the semiconductor switching element group. The power conversion device according to claim 7.

11. The control circuit unit has a voltage output node and a reference potential node electrically connected to the source electrodes of the plurality of semiconductor switching elements in the semiconductor switching element group, and a gate driver that outputs a control signal composed of a potential of H level and a potential of L level; 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 changed to a resistance value lower than the resistance value with respect to the set voltage when the input voltage input to the power conversion circuit is lower than the set voltage. The power conversion device according to claim 6.

12. The change in the switching time by the control signal output from the control circuit unit is performed by changing the voltage value of the drive voltage for the on-gate of the plurality of semiconductor switching elements in the semiconductor switching element group generated by the drive voltage generation unit according to the input voltage input to the power conversion circuit. The power conversion device according to claim 7.

13. The change in the switching time by the control signal output from the control circuit unit is performed by changing the voltage value of the drive voltage of the gates for turning off a plurality of semiconductor switching elements in the semiconductor switching element group generated by the drive voltage generation unit according to the input voltage input to the power conversion circuit. The power conversion device according to claim 7.

14. The power supply is a DC power supply composed of a secondary battery, The power conversion circuit is an inverter circuit having an inverter section, The inverter section has a low side arm and a high side arm, The semiconductor switching element group in the power conversion circuit is arranged in each of the low side arm and the high side arm in the inverter section, The control circuit unit monitors the voltage between the drain and source of the semiconductor switching element group arranged in the low side arm to determine whether the semiconductor switching element group arranged in the low side arm is in a short-circuit state, and when it is determined that it is in a short-circuit state, outputs an off command signal for turning off the semiconductor switching element group arranged in the high side arm. It has a short-circuit detection unit, The short-circuit detection unit changes the short-circuit detection time until an off command signal is output according to the input voltage input to the power conversion circuit. The power conversion device according to claim 1.

15. A power conversion device that receives input power from a power supply, converts the input input power, and outputs output power to a load, A power conversion circuit including a semiconductor switching element group having a plurality of semiconductor switching elements each having a control terminal and connected in parallel, A control circuit unit that outputs a control signal for on / off controlling a 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, The control circuit unit, Has a voltage output node and a reference potential node electrically connected to the source electrodes of a plurality of semiconductor switching elements in the semiconductor switching element group, and a gate driver that outputs a control signal composed of a potential of H level and a potential of L level, One terminal is electrically connected to the voltage output node of the gate driver, and the other terminal is electrically connected to the control terminals of a plurality of semiconductor switching elements in the semiconductor switching element group. It has a gate resistor whose resistance value becomes lower than the resistance value with respect to the set voltage when the input voltage input to the power conversion circuit is lower than the set voltage. Power conversion device.

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

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