Power conversion device

Abstract

To provide a power conversion device having an overcurrent protection circuit unit that rapidly detects an overcurrent and protects a semiconductor switching element.SOLUTION: In a power conversion device, an overcurrent protection circuit unit (41) includes a detection signal adjusting means (60) that outputs an adjusted detection signal (I-sens-aj) having a gain adjusted according to a detection signal (I_sens) of a current sensor (21) that detects a phase current and a comparator (61) that compares the adjusted detection signal with an overcurrent threshold (I_thres) to determine an overcurrent and provide an overcurrent stop signal (51) to a drive circuit unit (40).SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to a power conversion device. [Background technology]

[0002] In recent years, power semiconductor switching elements such as IGBTs (Insulated Gate Bipolar Transistors) and MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) have been widely used in power conversion devices used in electric powertrains of hybrid vehicles, electric vehicles, etc. Typically, a power semiconductor module is formed by one power semiconductor switching element or by a parallel connection of multiple power semiconductor switching elements, and the power conversion device is configured by the power semiconductor module.

[0003] In recent years, silicon carbide semiconductor switching elements (hereinafter referred to as SiC semiconductor switching elements), which are characterized by low loss and high speed operation, have been used as power semiconductor switching elements to improve the performance of power conversion devices. SiC semiconductor switching elements are characterized by a wide band gap, which is the region in which electrons cannot exist, and a dielectric breakdown voltage that is about 10 times higher than that of silicon semiconductor switching elements (hereinafter referred to as Si semiconductor switching elements).

[0004] Therefore, when the dielectric breakdown voltages of the SiC semiconductor switching element and the Si semiconductor switching element are designed to be equal, the thickness of the semiconductor layer that becomes the current path in the SiC semiconductor switching element can be made thinner than that of the Si semiconductor switching element. Therefore, the on-resistance value of the SiC semiconductor switching element when it is conductive can be made much smaller than the on-resistance value of the Si semiconductor switching element when it is conductive. Furthermore, when the SiC semiconductor switching element and the Si semiconductor switching element are compared under the same withstand voltage conditions, the width of the depletion layer of the SiC semiconductor switching element is about 1 / 10 of the width of the depletion layer of the Si semiconductor switching element, and the shortening effect of the carrier travel length enables the SiC semiconductor switching element to perform high-speed switching about 10 times faster than the Si semiconductor switching element.

[0005] By applying SiC semiconductor switching elements to a power conversion device that operates as an inverter for driving an electric motor, it is possible to reduce the loss of the power conversion device while the vehicle is running, leading to improvements in the power consumption rate or fuel consumption rate of the vehicle. In the case of an inverter, since the loss of the power semiconductor switching elements is directly linked to the loss of the entire inverter, reducing the loss of the power conversion device as an inverter is essential to obtain an electric vehicle that has a small environmental impact and is competitive in the market.

[0006] Semiconductor switching elements have an overload capacity for voltage and current, and if a voltage exceeding the overload capacity is applied or a current exceeding the overload capacity flows, the semiconductor switching elements may be destroyed. For this reason, power conversion devices are provided with a current sensor that detects the value of the current flowing through a conductive path including the semiconductor switching elements, and when the current sensor detects that an excessive current, that is, an overcurrent, flows, the current flowing through the semiconductor switching elements is stopped, thereby protecting the semiconductor switching elements from overcurrent.

[0007] In general, the switching speed (di / dt) of a power semiconductor switching element is designed so that a surge voltage exceeding the withstand voltage or rated voltage of the power semiconductor switching element is not applied to the power semiconductor switching element during its switching operation.

[0008] In addition, since the turn-on switching speed and gate constant of the power semiconductor switching element are determined so that the surge voltage is equal to or lower than the withstand voltage of the power semiconductor switching element even when an overcurrent occurs, which is the condition that causes the surge voltage to be the largest, if the overcurrent value is large, the gate constant must be increased to suppress the switching speed, and therefore, switching loss worsens even in the steady state region, which is the normal current region. Therefore, in order to improve the efficiency of the power conversion device, it is necessary to reduce the value of the current that becomes an overcurrent as much as possible.

[0009] A typical overcurrent protection circuit in a power conversion device is configured to input a detection signal corresponding to a current detected by a current sensor to a comparator, constantly compare the value of the detection signal with an overcurrent threshold set as an overcurrent value, and stop the power conversion device when the value of the detection signal from the current sensor exceeds the overcurrent threshold. Such a conventional overcurrent protection circuit can be configured with a relatively simple circuit, but the IC (Integrated Circuit) commonly used as a current sensor is a type of current sensor that uses the Hall effect, and this type of current sensor has a problem with responsiveness. When a current change occurs due to a sudden overload fluctuation, the current sensor's response is delayed, and the power conversion device may stop after the current value reaches a value larger than the expected overcurrent value.

[0010] In addition, the conventional overcurrent protection circuit disclosed in Patent Document 1 is configured to place an inductor with an open magnetic path near the negative or positive electrode of a semiconductor switching element, or near the wiring connected to the negative or positive electrode of the semiconductor switching element, and to set the direction in which the magnetic path of the inductor opens to the direction of the magnetic flux generated by the current flowing through the semiconductor switching element, and to turn off the switching element when the induced electromotive force generated in the inductor exceeds a predetermined value.

[0011] According to Patent Document 1, an inductor is used instead of a normal current sensor, and it is said that excessive current flowing through a semiconductor switching element can be quickly detected and cut off, thereby preventing damage to the semiconductor switching element. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Patent Publication No. 2017-99083 Summary of the Invention [Problem to be solved by the invention]

[0013] The conventional overcurrent protection circuit disclosed in Patent Document 1 has layout restrictions because it is necessary to arrange the inductor so that the release direction of the magnetic path is in the direction of the magnetic flux generated by the current flowing through the semiconductor switching element. Therefore, it cannot be used in devices that do not have an electric path through which current flows on the board, such as devices that handle large currents such as inverters. In addition, the shape and arrangement of the pattern of the electric path provided on the board to form a magnetic path are limited, which causes a problem of large circuit size.

[0014] One method of improving the responsiveness of overcurrent detection is to use a shunt resistor, which is known to have good responsiveness and accuracy to changes in current, to detect overcurrent. However, in the case of devices handling large currents, there is an issue that this increases power loss in the circuit.

[0015] The present disclosure discloses technology for solving the problems described above, and aims to provide a power conversion device having an overcurrent protection circuit unit that can quickly detect overcurrent and protect semiconductor switching elements. [Means for solving the problem]

[0016] The power conversion device disclosed in the present application is A power conversion device having a power conversion unit having a plurality of semiconductor switching elements and a control unit that controls the power conversion unit, and converts DC power to AC power or AC power to DC power, a current sensor that detects a current of the power conversion unit and outputs a detection signal corresponding to the current; The control unit is a drive circuit unit that outputs a drive signal for controlling switching of the semiconductor switching element; an overcurrent protection circuit unit that, when it is determined that an overcurrent flows in the power conversion unit, inputs an overcurrent stop signal to the drive circuit unit and causes the drive circuit unit to output a drive signal that switches the semiconductor switching element from an on state to an off state; Equipped with The overcurrent protection circuit unit includes: a detection signal adjusting unit that receives the detection signal output by the current sensor, adjusts a gain according to a value of the input detection signal, and outputs an adjusted detection signal based on the adjusted gain; a comparator that performs the determination based on a comparison between the value of the adjusted detection signal output by the detection signal adjustment means and an overcurrent threshold value, and inputs the overcurrent stop signal to the drive circuit unit; Equipped with It is characterized by:

[0017] In addition, the power conversion device disclosed in the present application is A power conversion device having a power conversion unit having a plurality of semiconductor switching elements and a control unit that controls the power conversion unit, and converts DC power to AC power or AC power to DC power, a current sensor that detects a current of the power conversion unit and outputs a detection signal corresponding to the current; The control unit is a drive circuit unit that outputs a drive signal for controlling switching of the semiconductor switching element; an overcurrent protection circuit unit that, when it is determined that an overcurrent flows in the power conversion unit, inputs an overcurrent stop signal to the drive circuit unit and causes the drive circuit unit to output a drive signal that switches the semiconductor switching element from an on state to an off state; Equipped with The overcurrent protection circuit unit includes: a comparator that performs the determination based on a comparison between the detection signal output by the current sensor and an overcurrent threshold value and inputs the overcurrent stop signal to the drive circuit unit; a switching circuit unit that switches the overcurrent threshold from one of a first overcurrent threshold and a second overcurrent threshold that is smaller than the first overcurrent threshold to the other; Equipped with The switching circuit unit is and when the detection signal output by the current sensor is equal to or greater than a predetermined value, the overcurrent threshold value to be compared with the detection signal is switched from the first overcurrent threshold value to the second overcurrent threshold value. It is characterized by:

[0018] Furthermore, the power conversion device disclosed in the present application is A power conversion device having a power conversion unit having a plurality of semiconductor switching elements and a control unit that controls the power conversion unit, and converts DC power to AC power or AC power to DC power, a current sensor that detects a current of the power conversion unit and outputs a detection signal corresponding to the current; The control unit is a drive circuit unit that outputs a drive signal for controlling switching of the semiconductor switching element; an overcurrent protection circuit unit that, when it is determined that an overcurrent flows in the power conversion unit, inputs an overcurrent stop signal to the drive circuit unit and causes the drive circuit unit to output a drive signal that switches the semiconductor switching element from an on state to an off state; Equipped with The overcurrent protection circuit unit includes: a switch means which is turned on when the value of the detection signal outputted by the current sensor is equal to or greater than a predetermined value; a differentiation circuit that increases a gain in accordance with a slope of an increase in the detection signal when the switch means is on; an adder that adds the detection signal output by the current sensor and an output of the differentiation circuit, and outputs a signal based on the addition as an adjusted detection signal; a comparator that performs the determination based on a comparison between the adjusted detection signal output by the adder and an overcurrent threshold and inputs the overcurrent stop signal to the drive circuit unit; a switching circuit unit that switches the overcurrent threshold from one of a first overcurrent threshold and a second overcurrent threshold that is smaller than the first overcurrent threshold to the other; Equipped with The switching circuit unit is and when the detection signal output by the current sensor is equal to or greater than the predetermined value, the overcurrent threshold value to be compared with the adjusted detection signal output by the adder is switched from the first overcurrent threshold value to the second overcurrent threshold value. It is characterized by: Effect of the Invention

[0019] According to the power conversion device disclosed in the present application, it is possible to obtain a power conversion device having an overcurrent protection circuit unit that can quickly detect overcurrent flowing in the power conversion device and protect semiconductor switching elements with a simple and inexpensive configuration. [Brief description of the drawings]

[0020] [Figure 1] 1 is a schematic configuration diagram showing a power conversion device according to a first embodiment. [Figure 2A] FIG. 2 is an explanatory diagram showing a state when an overcurrent occurs in a power conversion device. [Figure 2B] 1 is an explanatory diagram illustrating a waveform of a phase current when an overcurrent occurs in a power conversion device. FIG. [Diagram 3] FIG. 4 is an explanatory diagram illustrating an output characteristic of a current sensor. [Figure 4] 2 is a schematic configuration diagram showing the configuration of an overcurrent protection circuit unit in the power conversion device according to the first embodiment. FIG. [Diagram 5] 4 is an explanatory diagram for illustrating a schematic relationship between the output characteristic of the detection signal adjustment means and the gain and current in the power conversion device according to the first embodiment. FIG. [Figure 6] 4 is an explanatory diagram illustrating an operation of an overcurrent protection circuit unit when an overcurrent occurs in the power conversion device according to the first embodiment. FIG. [Figure 7] 11 is a schematic configuration diagram showing the configuration of an overcurrent protection circuit unit in a power conversion device according to a second embodiment. FIG. [Figure 8] 10 is an explanatory diagram for explaining the operation of a detection signal adjusting means in a power conversion device according to a second embodiment. FIG. [Figure 9] 11 is a schematic configuration diagram showing the configuration of an overcurrent protection circuit unit in a power conversion device according to a third embodiment. FIG. [Figure 10] 13 is an explanatory diagram illustrating an operation of an overcurrent protection circuit unit in a power conversion device according to a third embodiment. FIG. [Figure 11] FIG. 11 is a schematic configuration diagram showing an overcurrent protection circuit unit in a power conversion device according to a fourth embodiment. [Figure 12] FIG. 13 is a schematic configuration diagram showing an overcurrent protection circuit unit in a power conversion device according to a fifth embodiment. [Figure 13] FIG. 13 is a schematic configuration diagram showing a specific configuration of an overcurrent protection circuit unit in a power conversion device according to a fifth embodiment. [Figure 14] FIG. 13 is a schematic configuration diagram showing an overcurrent protection circuit unit in a power conversion device according to a sixth embodiment. [Figure 15]FIG. 13 is a schematic configuration diagram showing an overcurrent protection circuit unit in a power conversion device according to a seventh embodiment. [Figure 16] FIG. 23 is a schematic configuration diagram showing an overcurrent protection circuit unit in a power conversion device according to an eighth embodiment. [Figure 17] 11 is an explanatory diagram illustrating an operation of an overcurrent protection circuit unit in the power conversion device according to the sixth to eighth embodiments. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, a power conversion device according to the present disclosure will be described with reference to the drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals.

[0022] Embodiment 1 Fig. 1 is a schematic configuration diagram showing a power conversion device according to embodiment 1. In Fig. 1, the power conversion device 100 includes a power conversion circuit unit 30, a control unit 10, and a current sensor 21. The power conversion device 100 is connected between a DC power source 1 such as an on-board battery and an AC rotating electric machine 9 such as a three-phase synchronous rotating electric machine.

[0023] When the power conversion device 100 operates as a three-phase inverter, it converts DC power input from the DC power source 1 into three-phase AC power and supplies it to the armature windings of the AC rotating electric machine 9, and when it operates as a three-phase converter, it converts the three-phase AC power induced in the armature windings of the AC rotating electric machine 9 into DC power and supplies it to the DC power source 1. For convenience of explanation, the following description will be given assuming that the power conversion device 100 operates as a three-phase inverter and the AC rotating electric machine 9 operates as a three-phase synchronous motor (hereinafter simply referred to as a motor).

[0024] When the power conversion device 100 according to the first embodiment is applied to an electric vehicle or a hybrid vehicle, the DC power supply 1 is typically constituted by a secondary battery such as a nickel-metal hydride battery or a lithium-ion battery.

[0025] Power conversion circuit unit 30 is configured by a three-phase bridge circuit, and includes a U-phase upper arm semiconductor switching element 3, a U-phase lower arm semiconductor switching element 4, a V-phase upper arm semiconductor switching element 5, a V-phase lower arm semiconductor switching element 6, a W-phase upper arm semiconductor switching element 7, and a W-phase lower arm semiconductor switching element 8. Although these semiconductor switching elements are MOSFETs in the first embodiment, they may be configured by, for example, IGBTs and Di (diodes), or may be configured by SiC elements or the like.

[0026] A U-phase AC side terminal 30U derived from the series connection portion of the U-phase upper arm semiconductor switching element 3 and the U-phase lower arm semiconductor switching element 4 is connected to a U-phase armature winding terminal 9U of the motor 9. A V-phase AC side terminal 30V derived from the series connection portion of the V-phase upper arm semiconductor switching element 5 and the V-phase lower arm semiconductor switching element 6 is connected to a V-phase armature winding terminal 9V of the motor 9. A W-phase AC side terminal 30W derived from the series connection portion of the W-phase upper arm semiconductor switching element 7 and the W-phase lower arm semiconductor switching element 8 is connected to a W-phase armature winding terminal 9W of the motor 9.

[0027] The positive DC terminal 30P of the power conversion circuit unit 30 is connected to the positive electrode of the DC power supply 1, and the negative DC terminal 30N is connected to the negative electrode of the DC power supply 1. In addition, a smoothing capacitor 2 is connected between the positive DC terminal 30P and the negative DC terminal 30N.

[0028] The voltage sensor 20 is connected in parallel with the smoothing capacitor 2 between the positive DC terminal 30P and the negative DC terminal 30N of the power conversion circuit unit 30, detects the DC side voltage V2 of the power conversion circuit unit 30, and inputs a detection signal V2_sens corresponding to the detected DC voltage to the control unit 10 via a signal line 31a. The rotation sensor 11 detects a rotation angle θm of the rotor of the electric motor 9, and inputs a detection signal θm_sens corresponding to the detected rotation angle to the control unit 10 via a signal line 31e. The rotation sensor 11 is composed of, for example, a magnetic body provided on a rotating disk that rotates together with the rotor of the electric motor 9, and a Hall element that generates an output in response to the magnetic flux of the magnetic body.

[0029] The current sensor 21 is composed of a U-phase current sensor 21a, a V-phase current sensor 21b, and a W-phase current sensor 21c. The U-phase current sensor 21a is connected to a U-phase AC side terminal 30U of the power conversion circuit unit 30, detects a U-phase current Iu of the power conversion circuit unit 30, and inputs a detection signal Iu_sens corresponding to the value of the detected U-phase current to the control unit 10 via a signal line 31b. The V-phase current sensor 21b is connected to a V-phase AC side terminal 30V of the power conversion circuit unit 30, detects a V-phase current Iv of the power conversion circuit unit 30, and inputs a detection signal Iv_sens corresponding to the detected V-phase current to the control unit 10 via a signal line 31c. The W-phase current sensor 21c is connected to the W-phase AC side terminal 30W of the power conversion circuit unit 30, detects the W-phase current Iw of the power conversion circuit unit 30, and inputs a detection signal Iw_sens corresponding to the detected W-phase current to the control unit 10 via a signal line 31d.

[0030] At least the calculation unit (not shown) of the control unit 10 is configured by an ECU (Electronic Control Unit), and includes a processor (not shown) such as a microcomputer and a storage device (not shown). The storage device includes a volatile storage device such as a random access memory, and a non-volatile auxiliary storage device such as a flash memory. Also, an auxiliary storage device such as a hard disk may be included instead of the flash memory. The processor executes a program input from the storage device. In this case, the program is input from the auxiliary storage device to the processor via the volatile storage device. Also, the processor may output data such as a calculation result to a volatile storage device of the storage device, or may store the data in the auxiliary storage device via the volatile storage device.

[0031] The control unit 10 includes a drive circuit unit 40 serving as a gate drive circuit, and an overcurrent protection circuit unit 41. The control unit 10 receives the detection signal V2_sens corresponding to the DC voltage, the detection signal Iu_sens corresponding to the U-phase current, the detection signal Iv_sens corresponding to the V-phase current, the detection signal Iw_sens corresponding to the W-phase current, and the detection signal θm_sens corresponding to the rotation angle of the rotor, and also receives a torque command value Trq* for the electric motor 9 and a DC voltage command value V2* from the outside.

[0032] The control unit 10 calculates a drive signal 50 for driving each semiconductor switching element of the power conversion circuit unit 30 based on the above-mentioned input detection signals and command values, and causes the drive circuit unit 40 to generate the calculated drive signal 50 at a timing based on the calculation. The drive circuit unit 40 provides the generated drive signal to the gate of each semiconductor switching element.

[0033] That is, the drive circuit unit 40 in the control unit 10 provides a U-phase upper arm drive signal Gu1 to the gate of the U-phase upper arm semiconductor switching element 3 via control line 32a, a V-phase upper arm drive signal Gv1 to the gate of the V-phase upper arm semiconductor switching element 5 via control line 32c, and a W-phase upper arm drive signal Gw1 to the gate of the W-phase upper arm semiconductor switching element 7 via control line 32e.

[0034] In addition, the drive circuit unit 40 in the control unit 10 provides a U-phase lower arm drive signal Gu2 to the gate of the U-phase lower arm semiconductor switching element 4 via control line 32b, a V-phase lower arm drive signal Gv2 to the gate of the V-phase lower arm semiconductor switching element 6 via control line 32d, and a W-phase lower arm drive signal Gw2 to the gate of the W-phase lower arm semiconductor switching element 8 via control line 32f.

[0035] Each semiconductor switching element performs a switching operation based on a given drive signal, so that the power conversion circuit unit 30 operates as an inverter device, converts the DC power supplied from the DC power source 1 into three-phase AC power, supplies it to the electric motor 9, and drives the electric motor 9 to generate a desired rotation speed and torque.

[0036] The overcurrent protection circuit unit 41 provided in the control unit 10 includes a comparator that monitors the detection signal output by the current sensor 21 and determines whether or not the current flowing through the power conversion device 100 is an overcurrent. A detection signal corresponding to the current detected by the current sensor 21 is input to one input terminal of the comparator. A preset overcurrent threshold is input to the other input terminal of the comparator. When the voltage value of the input detection signal is equal to or greater than the voltage value of the overcurrent threshold, the comparator determines that the current flowing through the power conversion device 100 is an overcurrent, and inputs an overcurrent stop signal 51 to the drive circuit unit 40.

[0037] When the drive circuit unit 40 receives an overcurrent stop signal 51 from the comparator in the overcurrent protection circuit unit 41, it provides a drive signal to the semiconductor switching element to change the semiconductor switching element from an on state to an off state, thereby cutting off the overcurrent.

[0038] In the power conversion device 100 operating as described above, when the control unit 10 is controlling the switching operation of each semiconductor switching element to control the electric motor 9, if the on-duty range of any of the semiconductor switching elements widens and / or the element temporarily becomes stuck on due to a control abnormality in the microprocessor or the like, an overcurrent will flow from the power conversion device 100 to the electric motor 9 via that semiconductor switching element.

[0039] Here, a situation in which an overcurrent flows through the semiconductor switching elements of the power conversion device will be described. Fig. 2A is an explanatory diagram showing a state when an overcurrent occurs in the power conversion device. In Fig. 2A, it is now assumed that the U-phase upper arm semiconductor switching element 3, the V-phase lower arm semiconductor switching element 6, and the W-phase lower arm semiconductor switching element 8 are stuck on. In this case, the DC voltage of the DC power supply 1 continues to be applied to the motor 9 via the semiconductor switching elements that are stuck on, and the U-phase current Iu, the V-phase current Iv, and the W-phase current Iw flow as shown by the dashed lines in Fig. 2A.

[0040] Incidentally, the overcurrent protection circuit unit 41 can perform the same operation regardless of whether an overcurrent is detected among the U-phase current Iu, the V-phase current Iv, or the W-phase current Iw of the power conversion device. Therefore, in the description of the power conversion device in all of the embodiments described below, the current sensor of each phase will be simply referred to as a current sensor, the semiconductor switching element of each phase will be simply referred to as a semiconductor switching element, and the current of each phase will be simply referred to as a phase current.

[0041] 2B is an explanatory diagram showing a waveform of a phase current when an overcurrent occurs in a power conversion device, with the vertical axis representing the phase current [A] and the horizontal axis representing time. In FIG. 2B, from time t0 to just before time t1, the semiconductor switching elements perform a normal switching operation, and the phase current I flows normally at the rated current value I_ret including the allowable ripple current value I_lip, as shown in the figure.

[0042] If the on-duty range of the semiconductor switching element widens just before time t1 due to a control abnormality in the microprocessor or the like, and the semiconductor switching element is stuck on at time t1, the phase current I starts to increase just before time t1 and increases rapidly from time t1.

[0043] As shown in FIG. 1, the current sensor 21 monitors the phase current I and inputs a detection signal corresponding to the phase current I to the control unit 10 via a signal line. Here, attention is focused on the responsiveness of the current sensor 21. For example, in a magnetic field detection type current sensor using a Hall element, a magnetic core detects the magnetic field generated by the current flowing through the bus bar or the board wiring, and converts the magnetic flux density into a voltage. At this time, a delay occurs when converting from current to voltage. In other words, when the current changes abruptly, the output of the current sensor changes with a slight delay.

[0044] 2B, even if the phase current I reaches the overcurrent threshold I_thres at time t2, a delay time T_lag is required for the detection signal I_sens (not shown) output by the current sensor 21 to reach the overcurrent threshold I_thres, and at time t3, which is the time delay time T_lag after time t2, the detection signal I_sens reaches the overcurrent threshold I_thres and the overcurrent is cut off. As a result, the actual cutoff current value I_trp cut off at time t3 becomes a value that is greater than the overcurrent threshold I_thres, as shown in FIG. 2B.

[0045] As a result, semiconductor switching elements are at risk of failure due to excessive current and surge voltage when switching off, or it may be necessary to increase the gate constant and suppress the switching speed in order to suppress the surge voltage, resulting in increased switching losses.

[0046] Fig. 3 is an explanatory diagram showing the output characteristics of a current sensor, with the vertical axis showing current [A] and voltage [V], and the horizontal axis showing time. In Fig. 3, the phase current I to be detected increases rapidly from time t0, reaches the overcurrent threshold I_thres at time t1, and remains at a constant value after time t11. As described above, in the case of a magnetic field detection type current sensor using a general Hall element, a delay time T_lag occurs from when an overcurrent flows until the current sensor detects the current and outputs the current detection value I_sense.

[0047] For this reason, although the actual phase current I has reached the overcurrent threshold I_thres at time t1, the detection signal I_sens output by the current sensor is a voltage with a value corresponding to the phase current I being equal to or less than the overcurrent threshold I_thres at time t1. Then, at time t2 after the delay time ΔT based on the delay time from time t1, the detection signal I_sens of the phase current I reaches the overcurrent threshold I_thres.

[0048] As a countermeasure against the response delay of the current sensor, there is generally a current monitor using a shunt resistor, but in a power conversion device such as an inverter through which a large current flows, the shunt resistor becomes large, so it is difficult to adopt this as an effective countermeasure in reality. In addition, it is possible to simply lower the overcurrent threshold, but there is a risk of false detection of an overcurrent during normal operation, making it difficult to adopt this as a countermeasure against the detection delay of the current sensor.

[0049] The power conversion device according to the first embodiment has an overcurrent protection circuit unit capable of solving the problem caused by the response delay of the current sensor. Next, the overcurrent protection circuit unit in the power conversion device according to the first embodiment will be described. Fig. 4 is a schematic diagram showing the configuration of the overcurrent protection circuit unit in the power conversion device according to the first embodiment.

[0050] 4, overcurrent protection circuit unit 41 provided in control unit 10 includes detection signal adjustment means 60 which receives the detection signal output from current sensor 21 as input and outputs an adjusted detection signal with an adjusted gain [dB] (hereinafter, units will be omitted), and comparator 61 which compares the adjusted detection signal from detection signal adjustment means 60 with an overcurrent threshold and generates overcurrent stop signal 51 when the value of the adjusted detection signal is equal to or greater than the overcurrent threshold. Here, comparator 61 is provided corresponding only to the positive current of the phase current.

[0051] In the overcurrent protection circuit unit 41 configured as described above, the detection signal I_sens output from the current sensor 21 is input to the detection signal adjustment means 60. The detection signal adjustment means 60 adjusts the gain according to the input detection signal I_sens, and inputs an adjusted detection signal I_sens-aj based on the adjusted gain to an inverting input terminal a of a comparator 61. An overcurrent threshold I_thres is input to a non-inverting input terminal b of the comparator 61. The overcurrent threshold I_thres is generated by dividing the power supply voltage E by voltage dividing resistors r1 and r2.

[0052] The comparator 61 compares the input adjustment detection signal I_sens_aj with the overcurrent threshold I_thres, and outputs an overcurrent stop signal 51 to the drive circuit unit 40 of the control unit 10 when the adjustment detection signal I_sens_aj is equal to or greater than the overcurrent threshold I_thres (I_sens_aj≧I_thres).

[0053] When the overcurrent stop signal 51 is input from the overcurrent protection circuit 41, the drive circuit 40 provides a drive signal to the gate of the semiconductor switching element to turn off the semiconductor switching element, thereby changing the state from on to off. As a result, the overcurrent flowing between the power conversion device 100 and the motor 9 is interrupted.

[0054] Next, the detection signal adjustment means 60 will be described. Fig. 5 is an explanatory diagram for typically explaining the relationship between the output characteristics of the detection signal adjustment means and the gain and current in the power conversion device according to the first embodiment, where (a) is a graph showing the input / output characteristics of the detection signal adjustment means 60, and (b) is a graph showing the relationship between the gain of the detection signal adjustment means 60 and the detection signal that is the output of the current sensor 21. The vertical axis of (a) in Fig. 5 indicates the voltage [V] of the adjusted detection signal that is the output of the detection signal adjustment means 60, and the horizontal axis indicates the voltage [V] of the detection signal input to the detection signal adjustment means 60. The vertical axis of (b) in Fig. 5 indicates the gain, and the horizontal axis indicates the voltage [V] of the detection signal input to the detection signal adjustment means 60.

[0055] As shown in Fig. 5(b), the detection signal adjusting means 60 in the power conversion device according to embodiment 1 has a constant gain in steady-state region A, which is the rated current region of the power conversion device 100, but has a characteristic in which the gain increases curvilinearly in the overcurrent region B. Therefore, as shown in Fig. 5(a), in the steady-state region A of the power conversion device 100, the adjusted detection signal I_sens_aj, which is the output of the detection signal adjusting means 60, has output characteristics indicated by X1, but in the overcurrent region B, it has output characteristics indicated by X2.

[0056] That is, the detection signal adjusting means 60 is configured to suppress the gain to a constant value in the steady-state region A, and to increase the gain in the overcurrent region B according to the value of the input detection signal.

[0057] FIG. 6 is an explanatory diagram showing a schematic diagram of the operation of the overcurrent protection circuit unit when an overcurrent occurs in the power conversion device according to embodiment 1, where the vertical axis represents current [A] and voltage [V], and the horizontal axis represents time.

[0058] As described above, the gain of the detection signal adjusting means 60 is suppressed to a constant value in the steady region A until time t2 is reached, but increases rapidly from time t2 onwards in the overcurrent region B. Therefore, as shown in Fig. 6, the adjusted detection signal I_sens_aj as the output of the detection signal adjusting means 60 increases rapidly from time t2, reaches the overcurrent threshold I_thres at time t3 and is cut off at the overcurrent value I2.

[0059] If the gain of the detection signal adjusting means 60 were not adjusted, the detection signal I_sens would reach the overcurrent threshold I_thres at time t4 and would be cut off at the overcurrent value I1.

[0060] Therefore, in the power conversion device according to the first embodiment, the adjusted detection signal I_sens_aj increases rapidly in the overcurrent region B by adjusting the gain using the detection signal adjusting means 60, and as a result, the overcurrent can be cut off earlier than before by the time [t4-t3], and moreover, the overcurrent can be cut off at a current value smaller than before by the current value [I1-I2], and the surge voltage can be suppressed. As a result, the switching speed of the semiconductor switching elements is improved, and the efficiency of the power conversion device is improved.

[0061] Furthermore, according to the detection signal adjustment means 60 in the power conversion device of embodiment 1, the gain is not increased in the steady-state region A of the power conversion device, thereby avoiding the risk of malfunction in which an overcurrent threshold is reached in the steady-state region A and the power conversion device is stopped.

[0062] Embodiment 2 Next, a power conversion device according to a second embodiment will be described. In an actual power conversion device that operates as an inverter device or the like, positive and negative currents flow in each phase, so it is desirable to set the overcurrent threshold value on the positive side and the negative side. In the power conversion device according to the second embodiment, the overcurrent threshold value is set on the positive side and the negative side for each phase of the power conversion device.

[0063] Fig. 7 is a schematic diagram showing the configuration of an overcurrent protection circuit unit in a power conversion device according to embodiment 2. As shown in Fig. 7, overcurrent protection circuit unit 41 of the power conversion device according to embodiment 2 includes a positive side comparator 611 and a negative side comparator 612 as comparators.

[0064] The detection signal adjustment means 60 adjusts the gain according to the detection signal I_sens input from the current sensor 21, and inputs the adjusted detection signal I_sens-aj based on the adjusted gain to the inverting input terminal a of the positive side comparator 611 and the inverting input terminal a of the negative side comparator 612.

[0065] 8 is an explanatory diagram for typically explaining the operation of the detection signal adjusting means in the power conversion device according to the second embodiment, where (a) is a graph showing the output characteristics of the current sensor, and (b) is a graph showing the relationship between the adjusted detection signal as the output of the detection signal adjusting means and the detection signal as the output of the current sensor. The vertical axis of (a) in Fig. 8 indicates voltage [V], and the horizontal axis indicates current [A]. The vertical axis of (b) in Fig. 8 indicates voltage [V], and the horizontal axis indicates voltage [V].

[0066] 8(a), the current sensor 21 generates a detection signal I_sens proportional to the value of the phase current I of the power conversion device 100. Here, the phase current I (not shown) is divided into a steady region A spanning the positive and negative sides with 0 [A] of the phase current I as the center, a positive-side overcurrent region B, and a negative-side overcurrent region C, and the detection signal I_sens is similarly divided accordingly.

[0067] The detection signal adjustment means 60 has a characteristic that its gain changes according to the value of the detection signal I_sens input from the current sensor 21, and as shown in (b) of Figure 8, in the steady region A of the phase current I, it has a relatively small, constant gain as shown in (b) of Figure 5, and has a gain that increases rapidly in the overcurrent region B on the positive side of the phase current I.In addition, although not shown in (b) of Figure 5, the detection signal adjustment means 60 in the power conversion device 100 according to embodiment 2 also has a gain that increases rapidly in the overcurrent region C on the negative side of the phase current I.

[0068] Therefore, as shown in (b) of Figure 8, the detection signal adjustment means 60 in the power conversion device 100 according to embodiment 2 has output characteristics indicated by X1 in the steady-state region A, output characteristics indicated by X2 in the positive overcurrent region B, and output characteristics indicated by X3 in the negative overcurrent region C.

[0069] 7, the adjusted detection signal I_sens_aj is input to an inverting input terminal a of a positive-side comparator 611, and a positive-side overcurrent threshold Ip_thres is input to a non-inverting terminal b of the positive-side comparator 611. The positive-side overcurrent threshold Ip_thres is generated by dividing the power supply voltage E1 by voltage dividing resistors r1 and r2.

[0070] The adjusted detection signal I_sens_aj is input to an inverting input terminal a of the negative-side comparator 612, and the negative-side overcurrent threshold In_thres is input to a non-inverting terminal b of the negative-side comparator 612. The negative-side overcurrent threshold In_thres is generated by dividing the power supply voltage E2 by voltage dividing resistors r3 and r4.

[0071] The positive side comparator 611 compares the positive side value of the input adjustment detection signal I_sens_aj with the positive side overcurrent threshold Ip_thres, and outputs an overcurrent stop signal 511 to the drive circuit unit 40 of the control unit 10 when the positive side value of the adjustment detection signal I_sens_aj is greater than or equal to the positive side overcurrent threshold Ip_thres.

[0072] The negative side comparator 612 compares the negative side value of the input adjusted detection signal I_sens_aj with the negative side overcurrent threshold In_thres, and when the negative side value of the adjusted detection signal I_sens_aj is greater than or equal to the negative side overcurrent threshold In_thres, it outputs an overcurrent stop signal 512 to the drive circuit unit 40 of the control unit 10.

[0073] Therefore, in the power conversion device according to the second embodiment, the adjusted detection signal I_sens_aj increases rapidly in the positive and negative overcurrent regions by adjusting the gain of the detection signal adjusting means 60, and as a result, the overcurrent can be cut off earlier than before, and moreover, the overcurrent can be cut off at a smaller overcurrent value than before, and the surge voltage can be suppressed. As a result, the switching speed of the semiconductor switching elements is improved, and the efficiency of the power conversion device is improved.

[0074] Furthermore, according to the detection signal adjustment means 60 in the power conversion device of embodiment 2, the gain is not amplified in the steady-state region of the power conversion device, thereby avoiding the risk of malfunction in which an overcurrent threshold is reached in the steady-state region, causing the power conversion device to stop.

[0075] The other configurations and operations are the same as those in the first embodiment.

[0076] Embodiment 3 Next, a description will be given of a power conversion device according to embodiment 3. Fig. 9 is a schematic configuration diagram showing the configuration of an overcurrent protection circuit unit in the power conversion device according to embodiment 3.

[0077] In FIG. 9, the detection signal adjustment means 60 in the power conversion device according to embodiment 3 includes a switch means 70 as a gain switching means that turns on when a voltage equal to or greater than a predetermined value is input, a differentiation circuit 80 whose gain increases according to the slope of increase in the detection signal I_sens as the output voltage of the current sensor 21, and an adder 90 that adds the detection signal I_sens as the output voltage of the current sensor 21 and the output of the differentiation circuit 80.

[0078] In the above-mentioned embodiment 1, in order to deal with the shutdown delay caused by the response delay of the output of the current sensor when an overcurrent occurs, the gain is increased in the overcurrent region to generate an adjusted detection signal, making it easier to reach the overcurrent threshold and reducing the shutdown delay. However, in the power conversion device according to embodiment 3, the detection signal adjustment means 60 is made to have a predetermined gain with respect to the slope (dv / dt) of the change in the detection signal of the current sensor, which is proportional to the rate of change (di / dt) of the phase current of the power conversion device.

[0079] When the rate of change of the phase current of the power conversion device is slower than a predetermined rate of change, the differentiation circuit 80 does not operate, and the detection signal output from the current sensor 21 is input directly to the comparator 61 via the adder 90. In other words, the detection signal adjustment means 60 adjusts the detection signal only when a steeply changing overcurrent occurs. When an overcurrent occurs due to a gradual current increase, there is almost no delay between the actual current value and the output voltage of the current sensor, so there is almost no interruption delay when the overcurrent occurs.

[0080] Here, the switch means 70 shown in Fig. 9 will be described. The switch means 70 is turned on when the voltage of the detection signal I_sens of the current sensor is in a region of current values ​​equal to or greater than a predetermined value, i.e., a value corresponding to overcurrent region B, and the slope of the increase in the voltage of the detection signal I_sens is greater than a predetermined value. This increases the gain of the detection signal adjustment means 60.

[0081] That is, when the detection signal I_sens, which is the output voltage of the current sensor 21, is in the overcurrent region B and the slope of the increase in the detection signal I_sens is greater than a predetermined value, the switch means 70 in the detection signal adjustment means 60 is turned on. This increases the gain of the detection signal adjustment means 60, and the adjusted detection signal I_sens_aj, which is the output voltage, increases more rapidly than in a steady state.

[0082] If the switch means 70 is not provided, the differential circuit 80 will always be active, and when a steep current change occurs even in the steady state, the detection signal of the current sensor will be amplified, and the overcurrent threshold will be instantly reached, causing the power conversion device to stop, resulting in a risk of so-called erroneous detection. For this reason, the power conversion device according to the third embodiment is provided with the switch means 70 as a switching means for increasing the gain in the overcurrent region B. The switch means 70 is formed of, for example, a semiconductor switching element such as a Diac or Triac, or an analog switch.

[0083] When the detection signal I_sens as the output voltage of the current sensor 21 suddenly increases in the above-mentioned overcurrent region B, the switch means 70 turns on and the detection signal I_sens is applied to the inverting input terminal of the differentiation circuit 80. This causes the differentiation circuit 80 to operate and input its output voltage to the adder 90. The adder 90 outputs an adjusted detection signal I_sens_aj as an output voltage obtained by adding the output voltage of the differentiation circuit 80 and the detection signal I_sens, and inputs it to the comparator 61.

[0084] Figure 10 is an explanatory diagram showing the operation of the overcurrent protection circuit unit in the power conversion device according to embodiment 3, where (a) is a graph showing the output characteristics of the current sensor in a steady region where the phase current I of the power conversion device 100 changes with a gradual slope, and (b) is a graph showing the output characteristics of the current sensor in an overcurrent region where the phase current I of the power conversion device 100 changes with a steep slope.

[0085] 10(a), the current sensor 21 detects the phase current I of the power conversion device 100 in both the steady state region A and the overcurrent region B, and outputs the detection signal I_sens with a delay time. When the detection signal I_sens, which is the output of the current sensor 21, enters the overcurrent region B, the switch means 70 shown in FIG 9 turns on at time t1 immediately thereafter.

[0086] As shown in (b) of Figure 10, in steady state A until the switch means 70 turns on at time t1, the gain of the detection signal adjustment means 60 is not increased, so the adjusted detection signal I_sens_aj, which is the output voltage of the detection signal adjustment means 60, is input to the comparator 61 at the same value as the detection signal I_sens. However, at time t1, the switch means 70 turns on, causing the differentiation circuit 80 to operate, and as described above, the adjusted detection signal I_sens_aj, which is the output voltage of the differentiation circuit 80 and the detection signal I_sens added by the adder 90, is input to the inverting input terminal of the comparator 61.

[0087] As a result, the adjusted detection signal I_sens_aj reaches the overcurrent threshold I_thres at a time t2 earlier than in the case of the normal detection signal I_sens, and the overcurrent stop signal 51 can be output.

[0088] Embodiment 4 Next, a power conversion device according to a fourth embodiment will be described. Fig. 11 is a schematic diagram showing an overcurrent protection circuit unit in a power conversion device according to the fourth embodiment. In the power conversion device according to the third embodiment described above, a differentiation circuit is provided that increases the gain with respect to the gradient (di / dt) of the increase in overcurrent in order to improve the delay in shutting off the overcurrent associated with the output delay of the current sensor when an overcurrent occurs suddenly. In the fourth embodiment, however, a high-pass filter circuit is used instead of the differentiation circuit. The other configurations are the same as those of the third embodiment.

[0089] In Fig. 11, a high-pass filter circuit 801 is connected to a switch means 70. The other configurations are the same as those in the third embodiment. When a steep overcurrent occurs, the gradient (dv / dt) of the increase in the detection signal I_sens of the current sensor 21 increases, the switch means 70 turns on, the detection signal I_sens passes through the high-pass filter circuit 801, and is added to the original detection signal I_sens by the adder 90. This allows the same operation as in the third embodiment to be performed.

[0090] Embodiment 5. Next, a power converter according to a fifth embodiment will be described. Fig. 12 is a schematic diagram showing an overcurrent protection circuit unit in a power converter according to the fifth embodiment. As shown in Fig. 12, the detection signal adjusting means 60 of the overcurrent protection circuit unit 41 in the power converter according to the fifth embodiment is provided with a switch means 85, for example a transistor, for switching the voltage of the overcurrent threshold of the comparator 61 in a region equal to or higher than a predetermined voltage, i.e., in an overcurrent region, in addition to adjusting the detection signal I_sens which is the output of the current sensor 21. The other configurations are the same as those of the third embodiment shown in Fig. 9.

[0091] 13 is a schematic diagram showing a specific configuration of an overcurrent protection circuit unit in a power conversion device according to embodiment 5. The base of a transistor which is switch means 85 is connected to the output side of switch means 70 of detection signal adjustment means 60. Therefore, when switch means 70 is turned on, the transistor becomes conductive and shorts out resistor r5 of the voltage divider circuit. This causes the voltage of the overcurrent threshold I_thres to decrease.

[0092] That is, the overcurrent protection circuit unit of the power conversion device according to the fifth embodiment includes a switch means 70 that is turned on when the value of the detection signal I_sens output by the current sensor 21 is equal to or greater than a predetermined value, a differentiation circuit 80 that increases a gain in accordance with the slope of the increase in the detection signal I_sens when the switch means 70 is on, an adder 90 that adds the detection signal I_sens output by the current sensor 21 and the output of the differentiation circuit 80 and outputs a signal based on the addition as an adjusted detection signal I_sens_aj, and a comparison between the adjusted detection signal I_sens_aj output by the adder 90 and an overcurrent threshold I_thres. The device is equipped with a comparator 61 that determines an overcurrent based on the above and inputs an overcurrent stop signal 51 to the drive circuit unit 40, and a switch means 85 as a switching circuit unit that switches the overcurrent threshold I_thres from one of the first overcurrent threshold and a second overcurrent threshold smaller than the first overcurrent threshold to the other, and the switching circuit unit is configured to switch the overcurrent threshold I_thres to be compared with the adjusted detection signal I_sens_aj output by the adder 90 from the first overcurrent threshold to the second overcurrent threshold when the detection signal I_sens output by the current sensor 21 is equal to or greater than a predetermined value.

[0093] Therefore, in the overcurrent region, the switch means 85 turns on, the voltage of the overcurrent threshold I_thres drops, and the output voltage of the current sensor 21, and therefore the adjusted detection signal I_sens_aj which is the output of the detection signal adjustment means 60, easily reaches the overcurrent threshold. Therefore, an overcurrent is detected immediately when it occurs, and a cut-off delay is suppressed.

[0094] Embodiment 6 Next, a power conversion device according to the sixth embodiment will be described. Fig. 14 is a schematic configuration diagram showing an overcurrent protection circuit unit in the power conversion device according to the sixth embodiment. As shown in Fig. 14, the overcurrent protection circuit unit 41 according to the sixth embodiment does not include the detection signal adjustment means 60 provided in the fifth embodiment. The other configurations are the same as those of the fifth embodiment.

[0095] That is, as shown in FIG. 14, the overcurrent protection circuit unit 41 in the power conversion device according to embodiment 6 includes a comparator 61 that determines an overcurrent based on a comparison between the detection signal I_sens output by the current sensor 21 and an overcurrent threshold I_thres and inputs an overcurrent stop signal 51 to the drive circuit unit 40, and a switch means 85 as a switching circuit unit that switches the overcurrent threshold I_thres from one of a first overcurrent threshold and a second overcurrent threshold smaller than the first overcurrent threshold to the other, and the switching circuit unit is configured to switch the overcurrent threshold I_thres to be compared with the detection signal I_sens from the first overcurrent threshold to the second overcurrent threshold when the detection signal I_sens output by the current sensor 21 is equal to or greater than a predetermined value.

[0096] Fig. 17 is an explanatory diagram showing a schematic operation of the overcurrent protection circuit unit in the power conversion device according to the sixth to ninth embodiments, with the vertical axis showing voltage [V] and current [A] and the horizontal axis showing time. As shown in Fig. 17, the phase current I of the power conversion device 100 increases abruptly in the overcurrent region, and the detection signal I_sens, which is the output of the current sensor 21, increases with a time delay, but at time t1, the switch means 85 serving as the switching circuit unit turns on, and the overcurrent threshold is switched from the first overcurrent threshold I_thres1 to the second overcurrent threshold I_thres2.

[0097] This enables the detection signal I_sens to reach the second overcurrent threshold I_thres2 at time t2 earlier than normal, thereby suppressing a delay in cutting off the overcurrent.

[0098] Embodiment 7 Next, a power conversion device according to embodiment 7 will be described. Fig. 15 is a schematic configuration diagram showing an overcurrent protection circuit unit in the power conversion device according to embodiment 7. In the power conversion device according to embodiment 6 described above, even when the overcurrent increases relatively slowly, the overcurrent threshold is switched to a small value, so there is a slight risk of erroneous detection of a steady current near the overcurrent threshold.

[0099] 15, in the power conversion device according to the seventh embodiment, in order to take into account not only the value of the phase current but also the gradient of its change (increase), a differentiation circuit 80 is connected to the output side of the switch means 70. This operates to switch the overcurrent threshold only in response to a steep increase in the overcurrent (large di / dt).

[0100] That is, as shown in Fig. 17, at time t1, the switch means 85 serving as a switching circuit unit is turned on, and the overcurrent threshold is switched from the first overcurrent threshold I_thres1 to the second overcurrent threshold I_thres2. This allows the detection signal I_sens to reach the second overcurrent threshold I_thres2 at time t2, which is earlier than usual, and thus makes it possible to suppress a delay in shutting off the overcurrent. According to the seventh embodiment, it is possible to prevent shutoff due to erroneous detection of an overcurrent in the steady state region.

[0101] Embodiment 8 Next, a power conversion device according to the eighth embodiment will be described. Fig. 16 is a schematic configuration diagram showing an overcurrent protection circuit unit in a power conversion device according to the eighth embodiment. In the eighth embodiment, a high-pass filter circuit 801 is provided instead of the differentiation circuit 80 of the overcurrent protection circuit unit 41 according to the seventh embodiment. The other configurations are the same as those of the seventh embodiment.

[0102] The high-pass filter circuit 801 is connected to the switch means 70. When a steep overcurrent occurs, the gradient (dv / dt) of the increase in the detection signal I_sens of the current sensor 21 becomes large, the switch means 70 turns on, the detection signal I_sens passes through the high-pass filter circuit 801, and is added to the original detection signal I_sens by the adder 90. This allows the same operation as in the seventh embodiment to be performed.

[0103] In the power conversion devices of the above-described embodiments, the power conversion device has been described as an inverter device, but the power conversion device is not limited to this and may be a converter device.

[0104] Of the above-described embodiments, except for the second embodiment, a configuration having positive and negative overcurrent thresholds may be used, similarly to the second embodiment.

[0105] In addition, in each of the above-described embodiments, if an element with low switching loss, such as a SiC element which is a wide band gap semiconductor element, is used as the semiconductor switching element, the switching loss due to the switching speed at turn-on can be further reduced.

[0106] In the disclosure of the present application, by adjusting the current sensor output value in accordance with the magnitude and rate of change of the current flowing through the power conversion device, it is possible to suppress erroneous detections while quickly detecting and cutting off any sudden excessive current.

[0107] Furthermore, the control unit of each power conversion device individually adjusts the overcurrent threshold of the comparator according to the amount of variation in the comparator (including gain, offset, and temperature characteristics), improving the current accuracy when detecting and cutting off an overcurrent, thereby making it possible to prevent the semiconductor switching element from cutting off due to excessive current and breaking down due to a surge, or to prevent the gate constant from being increased to prevent breakdown due to a surge, thereby increasing switching losses.

[0108] Although various exemplary embodiments and examples are described in this application, various features, aspects, and functions described in one or more embodiments are not limited to the application of a specific embodiment, but can be applied to the embodiments alone or in various combinations. Therefore, countless modifications not illustrated are expected within the scope of the technology disclosed in this application. For example, the modification, addition, or omission of at least one component, and the extraction and combination of at least one component with components of other embodiments are included.

[0109] Next, aspects of the power conversion device disclosed in the present application will be described below as supplementary notes. (Appendix 1) A power conversion device having a power conversion unit having a plurality of semiconductor switching elements and a control unit that controls the power conversion unit, and converts DC power to AC power or AC power to DC power, a current sensor that detects a current of the power conversion unit and outputs a detection signal corresponding to the current; The control unit is a drive circuit unit that outputs a drive signal for controlling switching of the semiconductor switching element; an overcurrent protection circuit unit that, when it is determined that an overcurrent flows in the power conversion unit, inputs an overcurrent stop signal to the drive circuit unit and causes the drive circuit unit to output a drive signal that switches the semiconductor switching element from an on state to an off state; Equipped with The overcurrent protection circuit unit includes: a detection signal adjusting unit that receives the detection signal output by the current sensor, adjusts a gain according to a value of the input detection signal, and outputs an adjusted detection signal based on the adjusted gain; a comparator that performs the determination based on a comparison between the value of the adjusted detection signal output by the detection signal adjustment means and an overcurrent threshold value, and inputs the overcurrent stop signal to the drive circuit unit; Equipped with A power conversion device comprising: (Appendix 2) The detection signal adjusting means is configured to increase the gain when the detection signal output by the current sensor is equal to or greater than a predetermined value. 2. A power conversion device according to claim 1. (Appendix 3) The detection signal adjusting means includes: a switch means which is turned on when the value of the detection signal outputted by the current sensor is equal to or greater than a predetermined value; a differentiation circuit that differentiates the detection signal when the switch means is on; an adder that adds the detection signal output by the current sensor and an output of the differentiation circuit, and outputs a signal based on the addition as the adjusted detection signal; Equipped with 3. The power conversion device according to claim 1 or 2. (Appendix 4) The detection signal adjusting means includes: a switch means which is turned on when the value of the detection signal outputted by the current sensor is equal to or greater than a predetermined value; a high-pass filter circuit for filtering the detection signal when the switch means is on; an adder that adds the detection signal output by the current sensor and an output of the high-pass filter circuit, and outputs a signal based on the addition as the adjusted detection signal; Equipped with 3. The power conversion device according to claim 1 or 2. (Appendix 5) A power conversion device having a power conversion unit having a plurality of semiconductor switching elements and a control unit that controls the power conversion unit, and converts DC power to AC power or AC power to DC power, a current sensor that detects a current of the power conversion unit and outputs a detection signal corresponding to the current; The control unit is a drive circuit unit that outputs a drive signal for controlling switching of the semiconductor switching element; an overcurrent protection circuit unit that, when it is determined that an overcurrent flows in the power conversion unit, inputs an overcurrent stop signal to the drive circuit unit and causes the drive circuit unit to output a drive signal that switches the semiconductor switching element from an on state to an off state; Equipped with The overcurrent protection circuit unit includes: a comparator that performs the determination based on a comparison between the detection signal output by the current sensor and an overcurrent threshold value and inputs the overcurrent stop signal to the drive circuit unit; a switching circuit unit that switches the overcurrent threshold from one of a first overcurrent threshold and a second overcurrent threshold that is smaller than the first overcurrent threshold to the other; Equipped with The switching circuit unit is and when the detection signal output by the current sensor is equal to or greater than a predetermined value, the overcurrent threshold value to be compared with the detection signal is switched from the first overcurrent threshold value to the second overcurrent threshold value. A power conversion device comprising: (Appendix 6) The overcurrent protection circuit unit includes: a switch means which is turned on when the value of the detection signal outputted by the current sensor is equal to or greater than a predetermined value; a differentiation circuit that increases a gain in accordance with a slope of an increase in the detection signal when the switch means is on; Equipped with The switching circuitry is configured to switch from the first overcurrent threshold to the second overcurrent threshold based on an output of the differentiation circuit. 6. The power conversion device according to claim 5, (Appendix 7) The overcurrent protection circuit unit includes: a switch means which is turned on when the value of the detection signal outputted by the current sensor is equal to or greater than a predetermined value; a high-pass filter circuit for filtering the detection signal when the switch means is on; Equipped with The switching circuitry is configured to switch from a first overcurrent threshold to the second overcurrent threshold based on an output of the high-pass filter circuit. 6. The power conversion device according to claim 5, (Appendix 8) A power conversion device having a power conversion unit having a plurality of semiconductor switching elements and a control unit that controls the power conversion unit, and converts DC power to AC power or AC power to DC power, a current sensor that detects a current of the power conversion unit and outputs a detection signal corresponding to the current; The control unit is a drive circuit unit that outputs a drive signal for controlling switching of the semiconductor switching element; an overcurrent protection circuit unit that, when it is determined that an overcurrent flows in the power conversion unit, inputs an overcurrent stop signal to the drive circuit unit and causes the drive circuit unit to output a drive signal that switches the semiconductor switching element from an on state to an off state; Equipped with The overcurrent protection circuit unit includes: a switch means which is turned on when the value of the detection signal outputted by the current sensor is equal to or greater than a predetermined value; a differentiation circuit that increases a gain in accordance with a slope of an increase in the detection signal when the switch means is on; an adder that adds the detection signal output by the current sensor and an output of the differentiation circuit, and outputs a signal based on the addition as an adjusted detection signal; a comparator that performs the determination based on a comparison between the adjusted detection signal output by the adder and an overcurrent threshold and inputs the overcurrent stop signal to the drive circuit unit; a switching circuit unit that switches the overcurrent threshold from one of a first overcurrent threshold and a second overcurrent threshold that is smaller than the first overcurrent threshold to the other; Equipped with The switching circuit unit is and when the detection signal output by the current sensor is equal to or greater than the predetermined value, the overcurrent threshold value to be compared with the adjusted detection signal output by the adder is switched from the first overcurrent threshold value to the second overcurrent threshold value. A power conversion device comprising: (Appendix 9) The predetermined value of the detection signal is a value corresponding to a current value equal to or greater than a rated current value of the power conversion device. 9. The power conversion device according to claim 2, wherein (Appendix 10) The semiconductor switching element is formed of a wide band gap semiconductor element. 10. A power conversion device according to any one of claims 1 to 9. [Explanation of symbols]

[0110] 100 Power conversion device, 1 DC power supply, 2 Smoothing capacitor, 3 U-phase upper arm semiconductor switching element, 4 U-phase lower arm semiconductor switching element, 5 V-phase upper arm semiconductor switching element, 6 V-phase lower arm semiconductor switching element, 7 W-phase upper arm semiconductor switching element, 8 W-phase lower arm semiconductor switching element, 9 AC rotating electrical machine, 9U U phase armature winding terminal, 9V V phase armature winding terminal, 9W W-phase armature winding terminal, 10 control unit, 11 rotation sensor, 20 voltage sensor, 21 current sensor, 21a U phase current sensor, 21b V phase current sensor, 21c W-phase current sensor, 30 power conversion circuit unit, 30U U-phase AC side terminal, 30V V-phase AC side terminal, 30W W-phase AC side terminal, 30P positive side DC terminal, 30N Negative DC terminal. 31a, 31b, 31c, 31d. 31e signal line, 32a, 32b, 32c, 32d, 32e, 32f control lines, 40 drive circuit unit, 41 overcurrent protection circuit unit, 50 drive signal, 51, 511, 512 overcurrent stop signal, 60 detection signal adjustment means, 61 comparator, 611 positive side comparator, 612 negative comparator, 70, 85 switch means, 80 differentiation circuit, 90 Adder

Claims

1. A power conversion device having a power conversion unit having a plurality of semiconductor switching elements and a control unit that controls the power conversion unit, and converts DC power to AC power or AC power to DC power, a current sensor that detects a current of the power conversion unit and outputs a detection signal corresponding to the current; The control unit is a drive circuit unit that outputs a drive signal for controlling switching of the semiconductor switching element; an overcurrent protection circuit unit that, when it is determined that an overcurrent flows in the power conversion unit, inputs an overcurrent stop signal to the drive circuit unit and causes the drive circuit unit to output a drive signal that switches the semiconductor switching element from an on state to an off state; Equipped with The overcurrent protection circuit unit includes: a detection signal adjusting unit that receives the detection signal output by the current sensor, adjusts a gain according to a value of the input detection signal, and outputs an adjusted detection signal based on the adjusted gain; a comparator that performs the determination based on a comparison between the value of the adjusted detection signal output by the detection signal adjustment means and an overcurrent threshold value, and inputs the overcurrent stop signal to the drive circuit unit; Equipped with A power conversion device comprising:

2. The detection signal adjusting means is configured to increase the gain when the detection signal output by the current sensor is equal to or greater than a predetermined value.

2. The power conversion device according to claim 1 .

3. The detection signal adjusting means includes: a switch means which is turned on when the value of the detection signal outputted by the current sensor is equal to or greater than a predetermined value; a differentiation circuit that differentiates the detection signal when the switch means is on; an adder that adds the detection signal output by the current sensor and an output of the differentiation circuit, and outputs a signal based on the addition as the adjusted detection signal; Equipped with 3. The power conversion device according to claim 1 or 2.

4. The detection signal adjusting means includes: a switch means which is turned on when the value of the detection signal outputted by the current sensor is equal to or greater than a predetermined value; a high-pass filter circuit for filtering the detection signal when the switch means is on; an adder that adds the detection signal output by the current sensor and an output of the high-pass filter circuit, and outputs a signal based on the addition as the adjusted detection signal; Equipped with 3. The power conversion device according to claim 1 or 2.

5. A power conversion device having a power conversion unit having a plurality of semiconductor switching elements and a control unit that controls the power conversion unit, and converts DC power to AC power or AC power to DC power, a current sensor that detects a current of the power conversion unit and outputs a detection signal corresponding to the current; The control unit is a drive circuit unit that outputs a drive signal for controlling switching of the semiconductor switching element; an overcurrent protection circuit unit that, when it is determined that an overcurrent flows in the power conversion unit, inputs an overcurrent stop signal to the drive circuit unit and causes the drive circuit unit to output a drive signal that switches the semiconductor switching element from an on state to an off state; Equipped with The overcurrent protection circuit unit includes: a comparator that performs the determination based on a comparison between the detection signal output by the current sensor and an overcurrent threshold value and inputs the overcurrent stop signal to the drive circuit unit; a switching circuit unit that switches the overcurrent threshold from one of a first overcurrent threshold and a second overcurrent threshold that is smaller than the first overcurrent threshold to the other; Equipped with The switching circuit unit is When the detection signal output by the current sensor is equal to or greater than a predetermined value, the overcurrent threshold value to be compared with the detection signal is switched from the first overcurrent threshold value to the second overcurrent threshold value. A power conversion device comprising:

6. The overcurrent protection circuit unit includes: a switch means which is turned on when the value of the detection signal outputted by the current sensor is equal to or greater than a predetermined value; a differentiation circuit that increases a gain in accordance with a slope of an increase in the detection signal when the switch means is on; Equipped with The switching circuitry is configured to switch from the first overcurrent threshold to the second overcurrent threshold based on an output of the differentiating circuit.

6. The power conversion device according to claim 5.

7. The overcurrent protection circuit unit includes: a switch means which is turned on when the value of the detection signal outputted by the current sensor is equal to or greater than a predetermined value; a high-pass filter circuit for filtering the detection signal when the switch means is on; Equipped with The switching circuitry is configured to switch from the first overcurrent threshold to the second overcurrent threshold based on an output of the high-pass filter circuit.

6. The power conversion device according to claim 5.

8. A power conversion device having a power conversion unit having a plurality of semiconductor switching elements and a control unit that controls the power conversion unit, and converts DC power to AC power or AC power to DC power, a current sensor that detects a current of the power conversion unit and outputs a detection signal corresponding to the current; The control unit is a drive circuit unit that outputs a drive signal for controlling switching of the semiconductor switching element; an overcurrent protection circuit unit that, when it is determined that an overcurrent flows in the power conversion unit, inputs an overcurrent stop signal to the drive circuit unit and causes the drive circuit unit to output a drive signal that switches the semiconductor switching element from an on state to an off state; Equipped with The overcurrent protection circuit unit includes: a switch means which is turned on when the value of the detection signal outputted by the current sensor is equal to or greater than a predetermined value; a differentiation circuit that increases a gain in accordance with a slope of an increase in the detection signal when the switch means is on; an adder that adds the detection signal output by the current sensor and an output of the differentiation circuit, and outputs a signal based on the addition as an adjusted detection signal; a comparator that performs the determination based on a comparison between the adjusted detection signal output by the adder and an overcurrent threshold and inputs the overcurrent stop signal to the drive circuit unit; a switching circuit unit that switches the overcurrent threshold from one of a first overcurrent threshold and a second overcurrent threshold that is smaller than the first overcurrent threshold to the other; Equipped with The switching circuit unit is and when the detection signal output by the current sensor is equal to or greater than the predetermined value, the overcurrent threshold value to be compared with the adjusted detection signal output by the adder is switched from the first overcurrent threshold value to the second overcurrent threshold value. A power conversion device comprising:

9. The predetermined value of the detection signal is a value corresponding to a current value equal to or greater than a rated current value of the power conversion device.

9. The power conversion device according to claim 2, 5, 6, 7, or 8, characterized in that

10. The semiconductor switching element is formed of a wide band gap semiconductor switching element.

9. The power conversion device according to claim 1, 2, 5, 6, 7, or 8.

11. The semiconductor switching element is formed of a wide band gap semiconductor switching element.

4. The power conversion device according to claim 3.

12. The semiconductor switching element is formed of a wide band gap semiconductor switching element.

5. The power conversion device according to claim 4.

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