Power conversion device

Abstract

To reduce overcurrent that flows in a power semiconductor element in overcurrent protection operation of the power semiconductor element.SOLUTION: A power conversion device 100 comprises a control unit 10 for controlling a drive circuit 14 including an overcurrent protection circuit 41 and an element drive circuit 40 for outputting an element drive signal sd to power semiconductor elements 3a to 3f. The control unit 10 outputs a correction command signal sc generated on the basis of previously stored voltage correction amounts 86a, 86b or voltage correction amounts 86a, 86b calculated from previously stored voltage correction amount data 55 to the overcurrent protection circuit 41. When overcurrent flows, the overcurrent protection circuit 41 compares overcurrent threshold voltage Vthp, Vthn generated on the basis of the correction command signal sc with detection voltage Viu, Viv, Viw output by current sensors 21a, 21b, 21c to generate an overcurrent stop signal st.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] In recent years, power semiconductor 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, and the like. The power semiconductor element is mounted on a power semiconductor module, either as a single element or as a configuration in which multiple elements are connected in parallel. Such a power semiconductor module is mounted on a power conversion device.

[0003] Power semiconductor elements generally have a tolerance for voltage and current, and may be destroyed if the voltage and current exceed the allowable limits. For this reason, power conversion devices are equipped with current sensors that detect the value of the current flowing through the paths, and can protect the power semiconductor elements from overcurrent by detecting excessive current and stopping the current flowing through the power semiconductor elements.

[0004] In general, the switching speed (di / dt) of a power semiconductor element is designed not to exceed the breakdown voltage (voltage tolerance) of the power semiconductor element. Usually, when an overcurrent occurs, which is the condition for the largest surge, the control circuit of a power semiconductor element, for example, whose control terminal is a gate terminal, has control parameters set such as the turn-on switching speed, drive voltage value, and control terminal resistance value so that the surge voltage is equal to or lower than the breakdown voltage. For example, in a power semiconductor element whose control terminal is a gate terminal, the gate resistance value, i.e., the gate constant, is often used as the control parameter. For this reason, when the control circuit of the power semiconductor element sets the tolerance value of the overcurrent to a large value, it is necessary to increase the gate constant and suppress the switching speed. If the gate constant is set to a large value, the switching loss of the power semiconductor element will worsen even in the normal region. For this reason, in order to improve the efficiency of the power conversion device, it is necessary to reduce the current value of the overcurrent itself as much as possible.

[0005] A typical overcurrent protection circuit is one in which the output value detected and output by a current sensor is input to a comparator such as a comparator, which constantly compares the output value of the current sensor with a threshold value set as an overcurrent value, and when the output value of the current sensor exceeds the overcurrent threshold value, the comparator stops the power conversion device. This method can be configured with a relatively simple circuit, but when the output value of the current sensor varies due to variations in the current sensor, temperature characteristics, etc., the power conversion device may stop at a current value larger than the expected overcurrent value, i.e., the preset overcurrent value.

[0006] Patent Document 1 discloses an overcurrent detection circuit including the configuration of a general overcurrent protection circuit. The overcurrent detection circuit of Patent Document 1 includes a series circuit of a current detection MOSFET and a resistor connected in parallel to a drive MOSFET, and compares a detection voltage obtained by detecting the current of the drive MOSFET using the resistor of the series circuit with a threshold voltage obtained by detecting the current of a temperature characteristic correction MOSFET, which has the same temperature characteristic as the drive MOSFET, using a resistor, and outputs an overcurrent detection signal in which a gate control unit stops driving the drive MOSFET when the detection voltage exceeds the threshold voltage. The overcurrent detection circuit of Patent Document 1 improves the detection accuracy of an overcurrent by canceling the temperature characteristic of the detection voltage and the temperature characteristic of the threshold voltage. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2014-154669 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, the overcurrent detection circuit of Patent Document 1 adjusts the variation of the threshold value due to temperature fluctuation by providing a temperature characteristic correction MOSFET having the same temperature characteristic as the driving MOSFET, but in reality, even if MOSFETs of the same size and structure are used, errors occur in the adjusted threshold value due to the variation of each device itself, for example, the variation of the on-resistance. In addition, the overcurrent detection circuit of Patent Document 1 only adjusts the threshold value due to temperature fluctuation, and does not take into account the output variation of the series circuit of the current detection MOSFET and resistor corresponding to the current sensor, for example, gain error, offset error, etc. In addition, in the case of a magnetic field detection type current sensor with a coreless configuration, errors due to dimensional tolerance and arrangement variation are large. For this reason, when detecting an overcurrent using a current sensor, even if the threshold value is temperature corrected, errors due to the output variation of the current sensor cannot be sufficiently absorbed, and an overcurrent exceeding the expected value may flow.

[0009] The technology disclosed in this specification aims to reduce an overcurrent flowing through a power semiconductor element during an overcurrent protection operation of the power semiconductor element. [Means for solving the problem]

[0010] An example of a power conversion device disclosed in the present specification controls a power conversion unit having a plurality of power semiconductor elements to convert DC power into AC power or AC power into DC power. The power conversion unit includes a drive circuit that outputs an element drive signal for driving the plurality of power semiconductor elements, a control unit that controls the drive circuit, and a current sensor that detects the AC current of the power conversion unit. The drive circuit includes an element drive circuit that outputs an element drive signal to the power semiconductor elements, and an overcurrent protection circuit that determines that an overcurrent has flowed through the power semiconductor elements and outputs an overcurrent stop signal to the element drive circuit to cause the element drive circuit to output an element drive signal that changes the power semiconductor elements from an on state to an off state. The overcurrent protection circuit includes a comparator that determines that an overcurrent has flowed through the power semiconductor elements by comparing a detection voltage output by the current sensor with an overcurrent threshold voltage and generates an overcurrent stop signal, a threshold output unit that outputs the overcurrent threshold voltage, and a threshold voltage adjustment unit that generates an adjustment voltage that causes the threshold output unit to output the overcurrent threshold voltage based on a correction command signal output by the control unit, and outputs the adjustment voltage to the threshold output unit. The difference between the first voltage of the current sensor at the time of design and the second voltage of the installed current sensor for a predetermined overcurrent setting value that turns off the power semiconductor element is set as a voltage correction amount, and the control unit generates a correction command signal based on a voltage correction amount that has been stored in advance or a voltage correction amount calculated from pre-stored voltage correction amount data. Effect of the Invention

[0011] In one example of a power conversion device disclosed in the present specification, a control unit outputs a correction command signal generated based on a pre-stored voltage correction amount or a voltage correction amount calculated from pre-stored voltage correction amount data to an overcurrent protection circuit, and when an overcurrent flows, the overcurrent protection circuit generates an overcurrent stop signal by comparing the overcurrent threshold voltage generated based on the correction command signal with the detection voltage output by the current sensor, and changes a power semiconductor element in which it is determined that an overcurrent is flowing from an on state to an off state, thereby making it possible to reduce the overcurrent flowing in the power semiconductor element during the overcurrent protection operation of the power semiconductor element. [Brief description of the drawings]

[0012] [Figure 1] 1 is a diagram showing a schematic configuration of a first power conversion device according to a first embodiment. [Diagram 2] 10A and 10B are diagrams illustrating the operation of a power conversion device of a comparative example when an overcurrent occurs. [Diagram 3] FIG. 4 is a diagram showing a current waveform in a power conversion device of a comparative example. [Figure 4] FIG. 2 is a diagram showing a configuration of a drive circuit in FIG. [Diagram 5] FIG. 5 is a diagram showing a configuration of the protection circuit of FIG. [Figure 6] 2 is a diagram showing a first example of sensor characteristics of the current sensor of FIG. 1. [Figure 7] 1. FIG. 4 is a diagram showing a second example of the sensor characteristics of the current sensor of FIG. [Figure 8] 1. FIG. 4 is a diagram showing a third example of the sensor characteristics of the current sensor of FIG. [Figure 9] 4 is a diagram showing a first correction example of an overcurrent threshold of the overcurrent protection circuit according to the first embodiment; FIG. [Figure 10] 6 is a diagram showing a second correction example of the overcurrent threshold of the overcurrent protection circuit according to the first embodiment; FIG. [Figure 11] 6 is a diagram showing a third correction example of the overcurrent threshold of the overcurrent protection circuit according to the first embodiment; FIG. [Figure 12] 5A to 5C are diagrams illustrating a method for checking the sensor characteristics of the current sensor according to the first embodiment. [Figure 13] 13 is a diagram showing a fourth correction example of the overcurrent threshold of the overcurrent protection circuit according to the first embodiment. FIG. [Figure 14] 4 is a diagram showing a schematic configuration of a second power conversion device according to the first embodiment. FIG. [Figure 15] 13 is a diagram showing a fifth correction example of the overcurrent threshold of the overcurrent protection circuit according to the first embodiment. FIG. [Figure 16] FIG. 11 is a diagram showing a configuration of a drive circuit according to a second embodiment. [Figure 17] FIG. 17 is a diagram showing a configuration of a first protection circuit in FIG. 16. [Figure 18] FIG. 17 is a diagram showing a configuration of a second protection circuit in FIG. 16. [Figure 19] FIG. 13 is a diagram illustrating a duty ratio. [Figure 20] FIG. 19 is a diagram showing an output voltage characteristic of a smoothing circuit that smoothes the pulse signal Vpi of FIGS. 17 and 18. [Figure 21] 19 is a diagram showing an output voltage characteristic of a smoothing circuit that smoothes the pulse signal Vpia of FIG. 18. [Figure 22] 13 is a diagram showing a first example of an overcurrent threshold characteristic of a first protection circuit according to the second embodiment. FIG. [Diagram 23] 13 is a diagram showing a second example of the overcurrent threshold characteristic of the first protection circuit according to the second embodiment. FIG. [Figure 24] 13 is a diagram showing a third example of the overcurrent threshold characteristic of the first protection circuit according to the second embodiment. FIG. [Diagram 25] 13 is a diagram showing a first example of an overcurrent threshold characteristic of a second protection circuit according to the second embodiment. FIG. [Figure 26] 13 is a diagram showing a second example of an overcurrent threshold characteristic of a second protection circuit according to the second embodiment. FIG. [Figure 27] 13 is a diagram showing a third example of the overcurrent threshold characteristic of the second protection circuit according to the second embodiment. FIG. [Figure 28] 13 is a diagram showing a first correction example of an overcurrent threshold of the protection circuit according to the second embodiment; FIG. [Figure 29] 13 is a diagram showing a second correction example of the overcurrent threshold of the protection circuit according to the second embodiment. FIG. [Diagram 30]13 is a diagram showing a second correction example of the overcurrent threshold of the protection circuit according to the second embodiment. FIG. [Diagram 31] 13 is a diagram showing a second correction example of the overcurrent threshold of the protection circuit according to the second embodiment. FIG. [Diagram 32] FIG. 11 is a diagram showing a configuration of a drive circuit according to a third embodiment. [Diagram 33] FIG. 33 is a diagram showing a configuration of a protection circuit in FIG. 32. [Diagram 34] FIG. 34 is a diagram showing a first example of an overcurrent threshold characteristic of the protection circuit of FIG. 33. [Diagram 35] FIG. 34 is a diagram showing a second example of the overcurrent threshold characteristic of the protection circuit of FIG. 33. [Diagram 36] FIG. 34 is a diagram showing a third example of the overcurrent threshold characteristic of the protection circuit of FIG. 33. [Figure 37] FIG. 34 is a diagram showing a fourth example of the overcurrent threshold characteristic of the protection circuit of FIG. 33. [Figure 38] FIG. 34 is a diagram showing a fifth example of the overcurrent threshold characteristic of the protection circuit of FIG. 33. [Figure 39] FIG. 34 is a diagram showing a sixth example of the overcurrent threshold characteristic of the protection circuit of FIG. 33. [Diagram 40] FIG. 13 is a diagram showing a configuration of a first drive circuit according to a fourth embodiment. [Diagram 41] FIG. 41 is a diagram showing a configuration of the overcurrent protection circuit of FIG. 40. [Diagram 42] FIG. 13 is a diagram showing a configuration of a second drive circuit according to the fourth embodiment. [Diagram 43] FIG. 43 is a diagram showing a configuration of the overcurrent protection circuit of FIG. 42. [Diagram 44] 44 is a diagram showing an example of correction of the overcurrent threshold of the overcurrent protection circuit of FIG. 43. [Diagram 45] 42 is a diagram showing an example of correction of an overcurrent threshold of the overcurrent protection circuit of FIG. 41. [Diagram 46] FIG. 13 is a diagram showing a configuration of a first drive circuit according to a fifth embodiment. [Figure 47] FIG. 47 is a diagram showing the configuration of the protection circuit of FIG. 46. [Figure 48] FIG. 13 is a diagram showing a configuration of a second drive circuit according to the fifth embodiment. [Figure 49]FIG. 49 is a diagram showing a configuration of the overcurrent protection circuit of FIG. 48. [Figure 50] FIG. 2 is a diagram illustrating an example of a hardware configuration for implementing the functions of a control unit by digital calculation. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, preferred embodiments of the power conversion device of the present application will be described with reference to the drawings. In each drawing, the same or corresponding parts are designated by the same reference numerals, and duplicated description will be omitted.

[0014] Embodiment 1 FIG. 1 is a diagram showing a schematic configuration of a first power conversion device according to the first embodiment. FIG. 2 is a diagram explaining the operation of a power conversion device of a comparative example when an overcurrent occurs, and FIG. 3 is a diagram showing a current waveform in the power conversion device of the comparative example. FIG. 4 is a diagram showing the configuration of a drive circuit of FIG. 1, and FIG. 5 is a diagram showing the configuration of a protection circuit of FIG. 4. FIG. 6, FIG. 7, and FIG. 8 are diagrams showing a first example, a second example, and a third example of sensor characteristics in the current sensor of FIG. 1, respectively. FIG. 9, FIG. 10, and FIG. 11 are diagrams showing a first example, a second example, and a third example of correction of an overcurrent threshold of an overcurrent protection circuit according to the first embodiment, respectively. FIG. 12 is a diagram explaining a method for checking the sensor characteristics of a current sensor according to the first embodiment, and FIG. 13 is a diagram showing a fourth example of correction of an overcurrent threshold of an overcurrent protection circuit according to the first embodiment. FIG. 14 is a diagram showing a schematic configuration of a second power conversion device according to the first embodiment, and FIG. 15 is a diagram showing a fifth example of correction of an overcurrent threshold of an overcurrent protection circuit according to the first embodiment. The power conversion device 100 of the first embodiment controls a power conversion unit 110 having a plurality of power semiconductor elements 3a, 3b, 3c, 3d, 3e, and 3f to convert DC power into AC power or AC power into DC power. FIG. 1 shows an example of the power conversion device 100 that converts DC power into AC power, that is, an inverter circuit. The power conversion device 100 includes a drive circuit 14 that outputs an element drive signal sd that drives the plurality of power semiconductor elements 3a to 3f, a control unit 10 that controls the drive circuit 14, and current sensors 21a, 21b, and 21c that detect the AC current of the power conversion unit 110. An example in which the power conversion device 100 is an inverter circuit will be mainly described, but an example in which the power conversion device 100 is a converter circuit that converts AC power into DC power will also be described as appropriate.

[0015] In the power conversion device 100, a DC power source 1 is connected to DC terminals 16p and 16n on the input side, and a motor 9 is connected to AC terminals 17u, 17v, and 17w on the output side via AC wiring 19u, 19v, and 19w. The DC power source 1 is, for example, a battery, and outputs DC power, that is, DC voltage and DC current. Here, when the power conversion device 100 of the first embodiment is applied to an automobile equipped with an electric powertrain such as an electric automobile or a hybrid automobile, the DC power source 1 is a secondary battery represented by a nickel-metal hydride battery, a lithium-ion battery, or the like. The motor 9 is, for example, a generator, an electric motor, a generator motor, or the like. When the power conversion device 100 outputs AC power to the motor 9, the motor 9 acts as a load, and when the power conversion device 100 outputs DC power obtained by inputting AC power from the motor 9 and converting it to DC power, the motor 9 acts as a generator.

[0016] Power conversion unit 110 is, for example, a three-phase inverter equipped with a capacitor 2 that removes and smoothes voltage ripple and noise on the DC side, and power semiconductor elements 3a-3f that are semiconductor switching elements, and converts the output power of capacitor 2 into three-phase AC power and outputs it from AC terminals 17u, 17v, and 17w to motor 9. AC terminals 17u, 17v, and 17w of power conversion unit 110 supply the three-phase AC power to motor 9 through AC wiring 19u, 19v, and 19w.

[0017] The control unit 10 and the drive circuit 14 output an element drive signal sd to the power semiconductor elements 3a to 3f, which are switching elements, to control the on and off states of the power semiconductor elements 3a to 3f. The element drive signal sd includes a predetermined dead time to prevent the power semiconductor elements connected in series of the power conversion unit 110 from being simultaneously turned on. The control unit 10 outputs a drive control signal scg to the drive circuit 14 based on a torque command value Trq* of the motor 9 input from the outside, a DC voltage command value Vdc*, a DC voltage Vdc between the high-power side wiring 18p and the low-power side wiring 18s of the power conversion unit 110 detected by a voltage sensor 20, and a rotation angle θm detected by a rotation sensor 25. Furthermore, the control unit 10 generates the correction command signal sc based on pre-stored voltage correction amounts 83a, 83b (see FIGS. 9 to 11) or pre-stored voltage correction amount data, that is, voltage correction amount 86a, 86b (see FIG. 13) calculated from the corrected sensor characteristic 55. Note that the pre-stored voltage correction amount may be the voltage correction amounts 86a, 86b calculated in advance from the corrected sensor characteristic 55 without storing the corrected sensor characteristic 55 in the control unit 10.

[0018] The drive circuit 14 includes an element drive circuit 40 that outputs an element drive signal sd to the power semiconductor elements 3a to 3f, and an overcurrent protection circuit 41 that outputs an overcurrent stop signal st to the element drive circuit 40 to determine that an overcurrent has flowed through the power semiconductor elements 3a to 3f and output an element drive signal sd to turn the power semiconductor elements 3a to 3f from an on state to an off state. The voltage correction amounts 83a and 83b are the difference between the first voltage (positive side overcurrent threshold Vth0p, negative side overcurrent threshold Vth0n) of the current sensor at the time of design and the second voltage (positive side overcurrent threshold Vthap, negative side overcurrent threshold Vthan) of the current sensor mounted, with respect to the predetermined overcurrent setting value (positive side overcurrent setting value Iocp, negative side overcurrent setting value Iocn) that turns the power semiconductor elements 3a to 3f into an off state. The voltage correction amounts 83a, 83b, 86a, and 86b and the terms "positive side" and "negative side" used consecutively in the names will be described later.

[0019] The element drive signal sd is input to the power semiconductor elements 3a to 3f via six signal lines 32a to 32f. The element drive signal sda is input to the power semiconductor element 3a via the signal line 32a, and the element drive signal sdb is input to the power semiconductor element 3b via the signal line 32b. The element drive signal sdc is input to the power semiconductor element 3c via the signal line 32c, and the element drive signal sdd is input to the power semiconductor element 3d via the signal line 32d. The element drive signal sde is input to the power semiconductor element 3e via the signal line 32e, and the element drive signal sdf is input to the power semiconductor element 3f via the signal line 32f. As appropriate, the symbol sd is used collectively for the element drive signals, and sda to sdf are used to distinguish them. The voltage sensor 20 outputs the detected DC voltage Vdc to the control unit 10 via the signal line 31a.

[0020] The current sensors 21a, 21b, and 21c are disposed on the AC wirings 19u, 19v, and 19w, respectively. The AC wirings 19u, 19v, and 19w are AC wirings of U phase, V phase, and W phase, respectively. The current sensor 21a detects the U-phase AC current Iu flowing through the AC wiring 19u, and outputs a detection voltage Viu corresponding to the AC current Iu to the drive circuit 14 via a signal line 31b. Similarly, the current sensor 21b detects the V-phase AC current Iv flowing through the AC wiring 19v, and outputs a detection voltage Viv corresponding to the AC current Iv to the drive circuit 14 via a signal line 31c. The current sensor 21c detects the V-phase AC current Iw flowing through the AC wiring 19w, and outputs a detection voltage Viw corresponding to the AC current Iw to the drive circuit 14 via a signal line 31d.

[0021] The power semiconductor elements 3a to 3f of the power conversion unit 110 form a full bridge circuit. The power semiconductor elements 3a, 3c, and 3e connected to the high-power side wiring 18p form an upper arm, and the power semiconductor elements 3b, 3d, and 3f connected to the low-power side wiring 18s form a lower arm. The legs in which the upper arm and the lower arm are connected in series are a series body in which the power semiconductor element 3a and the power semiconductor element 3b are connected in series, a series body in which the power semiconductor element 3c and the power semiconductor element 3d are connected in series, and a series body in which the power semiconductor element 3e and the power semiconductor element 3f are connected in series. The connection point between the upper arm and the lower arm is connected to an AC terminal. The connection point between the power semiconductor element 3a and the power semiconductor element 3b is connected to an AC terminal 17u. The connection point between the power semiconductor element 3c and the power semiconductor element 3d is connected to an AC terminal 17v, and the connection point between the power semiconductor element 3e and the power semiconductor element 3f is connected to an AC terminal 17w. In FIG. 1, an example of MOSFETs having a transistor Tr and a diode Di is shown as the power semiconductor elements 3a to 3f. The diode Di may be a parasitic diode of a MOSFET or a diode of a separate element. The power semiconductor elements 3a to 3f are not limited to MOSFETs and may be composed of, for example, an IGBT which is a transistor Tr and a diode Di connected in anti-parallel to the IGBT.

[0022] The control unit 10 is a circuit that controls the power conversion unit 110 via the drive circuit 14, and is realized by electronic components including a configuration for executing a program stored in a memory 99 shown in FIG. 50 by a processor 98. FIG. 50 is a diagram showing an example of a hardware configuration for realizing the function of the control unit by digital calculation. The electronic components constituting the control unit 10 are, for example, a microcontroller (microcontroller) and a system LSI (Large Scale Integration). FIG. 50 is a diagram showing an example of a hardware configuration for realizing the function of the control unit 10 by digital calculation. The function realized by the digital calculation of the control unit 10 is realized by the processor 98 and the memory 99. Furthermore, a plurality of processors 98 and a plurality of memories 99 may cooperate to execute each function.

[0023] The control unit 10 and the drive circuit 14 control the power semiconductor elements 3a-3f of the power conversion unit 110 so that the desired power is supplied to the motor 9. Specifically, the control unit 10 calculates the time (on time) for each of the power semiconductor elements 3a-3f of the power conversion unit 110 to be in the on state based on the power to be supplied to the motor 9. For example, the power conversion unit 110 can be controlled by PWM (Pulse Width Modulation) control that modulates the on time of the power semiconductor elements 3a-3f according to the voltage to be output. Then, the control unit 10 outputs a drive control signal scg, which is a control command, to the drive circuit 14 so that an on signal is output to the power semiconductor elements that should be in the on state at each time point, and an off signal is output to the power semiconductor elements that should be in the off state. The drive circuit 14 outputs an on signal or an off signal as an element drive signal sd to the control electrodes of the power semiconductor elements 3a-3f according to the drive control signal scg.

[0024] The upper arm power semiconductor elements 3a, 3c, and 3e connected to the positive side of the DC power source 1 and the high-voltage side wiring 18p, and the lower arm power semiconductor elements 3b, 3d, and 3f connected to the negative side of the DC power source 1 and the low-voltage side wiring 18s are not turned on at the same time due to the dead time described above. The upper arm power semiconductor elements 3a, 3c, and 3e can also be called positive side power semiconductor elements. The lower arm power semiconductor elements 3b, 3d, and 3f can also be called negative side power semiconductor elements. When the power conversion device 100 is an inverter circuit, that is, when the power conversion unit 110 is an inverter, when the upper arm power semiconductor elements 3a, 3c, and 3e are turned on, AC currents Iu, Iv, and Iw flow in the positive direction (the direction of the arrows Iu, Iv, and Iw in FIG. 1) from the AC terminals 17u, 17v, and 17w to the motor 9. When the power semiconductor elements 3b, 3d, and 3f of the lower arm are turned on, AC currents Iu, Iv, and Iw flow from the motor 9 to the AC terminals 17u, 17v, and 17w in the negative direction, which is the opposite direction to the positive direction. When the power conversion device 100 is a converter circuit, i.e., when the power conversion unit 110 is a converter, AC currents Iu, Iv, and Iw flow from the motor 9 to the AC terminals 17u, 17v, and 17w when the power semiconductor elements 3a, 3c, and 3e of the upper arm are turned on. When the power semiconductor elements 3b, 3d, and 3f of the lower arm are turned on, AC currents Iu, Iv, and Iw flow from the AC terminals 17u, 17v, and 17w to the motor 9. The current flows from the side with higher potential to the side with lower potential, so the direction is changed between the inverter and the converter. Here, in cases where the terms differ from the general usage such as the positive and negative sides of DC power supply 1, the term "positive side" used consecutively in the name refers to the power semiconductor elements 3a, 3c, and 3e of the upper arm, and the term "negative side" used consecutively in the name refers to the power semiconductor elements 3b, 3d, and 3f of the lower arm.

[0025] A mechanism of an overcurrent occurring in the power conversion unit 160 of the power conversion device 150 of the comparative example will be described with reference to FIG. 2. The power conversion unit 160 of the comparative example has the same configuration as the power conversion unit 110 of the first embodiment, but the element drive signal sd input when an overcurrent occurs in the power semiconductor elements 3a to 3f is different from that of the power conversion unit 110 of the first embodiment. In FIG. 2, a control unit such as a microcomputer and an element drive unit are omitted. Consider a case in which the pulse width for turning on the power semiconductor elements 3a to 3f in PWM control, i.e., the width of the on-duty, widens due to an abnormality in the control unit or exceeds the control period and temporarily becomes stuck in the on state. FIG. 2 shows a case in which the power semiconductor elements 3a, 3d, and 3f are stuck. A current 91a flows from the upper arm power semiconductor element 3a to the AC wiring 19u, a current 91b flows from the AC wiring 19v to the lower arm power semiconductor element 3d, and a current 91c flows from the AC wiring 19w to the lower arm power semiconductor element 3f.

[0026] At this time, as shown in FIG. 3, the current value goes out of the steady-state operating range and enters the overcurrent region at time t1. The vertical axis of FIG. 3 represents the phase current of each phase, and the horizontal axis represents time. The element drive unit of the comparative example is provided with a comparator for each phase, similar to the overcurrent detection circuit of Patent Document 1. The comparators compare the detection voltages Viu, Viv, and Viw detected by the U-phase current sensor 21a, the V-phase current sensor 21b, and the W-phase current sensor 21c with threshold values. When the detection voltages Viu, Viv, and Viw exceed the threshold values, the comparator for each phase outputs an overcurrent stop signal st to the element drive circuit to shut off the power semiconductor elements 3a to 3f.

[0027] Here, the current sensors 21a, 21b, and 21c have variations. For example, in a magnetic field detection type current sensor, a magnetic field generated from a current flowing through a bus bar connecting the power semiconductor elements 3a to 3f of the power conversion unit 160 and the power conversion unit 110, a board wiring, etc. is picked up by a magnetic core or the like, and the magnetic flux density is converted into a voltage. In this magnetic field detection type current sensor, variations occur in the output voltage output according to the current value due to variations in the Hall element, for example, the influence of the surrounding magnetic flux, and variations in the circuit. In FIG. 3, the period from time t0 to time t1 is the steady operation range, the period from time t1 to time t3 is the overcurrent region, and the period from time t3 to time t4 is the cutoff region. Time t2 is the time when the phase current becomes the overcurrent threshold value Ith in the design, and time t3 is the time when the phase current is actually cut off at the cutoff current value Ioff. The rated current Ira and the current ripple Irp are also shown in FIG. 3.

[0028] As shown in Fig. 3, from the overcurrent threshold Ith (design value) at the time of design until the detection voltages Viu, Viv, and Viw output by the current sensors 21a, 21b, and 21c reach the threshold (from time t2 to time t3), a current greater than expected flows, and the cutoff current value Ioff, which is the current value at the time of cutoff, becomes larger than the overcurrent threshold Ith by a current difference ΔIdt. For example, when detecting an overcurrent at 1000 A, the power semiconductor elements 3a to 3f may not be stopped at the set value due to the variation of the current sensor, and an overcurrent of 1200 to 1300 A may flow through the power semiconductor elements 3a to 3f. Therefore, in the power conversion device 150 of the comparative example, the risk of failure of the power semiconductor elements 3a to 3f due to the excessive current and surge voltage at the time of cutoff increases. Therefore, in the power conversion device 150 of the comparative example, in order to suppress surges due to excessive currents and surge voltages, it is necessary to increase the gate constants, which are control parameters related to the control terminals of the MOSFETs and IGBTs, and it is necessary to suppress the switching speeds of the power semiconductor elements 3a to 3f. As a result, in the power conversion device 150 of the comparative example, the switching losses of the power semiconductor elements 3a to 3f increase.

[0029] The power conversion device 100 of the first embodiment can reduce the current difference ΔIdt, which is the difference between the interruption current value Ioff and the overcurrent threshold Ith described in the comparative example, by correcting the variation in the output values ​​output by the current sensors 21a, 21b, and 21c. That is, the power conversion device 100 of the first embodiment can reduce the overcurrent flowing through the power semiconductor elements 3a to 3f during the overcurrent protection operation of the power semiconductor elements 3a to 3f by correcting the variation in the output values ​​output by the current sensors 21a, 21b, and 21c. Furthermore, the power conversion device 100 of the first embodiment does not need to increase the gate constant of the power semiconductor elements 3a to 3f and does not need to suppress the switching speed of the power semiconductor elements 3a to 3f because the overcurrent during the overcurrent protection operation is reduced. Therefore, the power conversion device 100 of embodiment 1 can improve the switching speed of the power semiconductor elements 3a to 3f and reduce the switching loss of the power semiconductor elements 3a to 3f more than the power conversion device 150 of the comparative example by reducing the overcurrent during overcurrent protection operation.

[0030] The overcurrent protection operation of the power conversion device 100 and the overcurrent protection circuit 41 of the first embodiment will be described. The overcurrent protection circuit 41 shown in FIG. 4 is an example in which a protection circuit 59 is provided for each phase of a three-phase AC. The overcurrent protection circuit 41 of the first embodiment includes a U-phase protection circuit 59u, a V-phase protection circuit 59v, and a W-phase protection circuit 59w. The protection circuits 59u, 59v, and 59w have the configuration shown in FIG. 5. The protection circuits are generally designated by 59 as appropriate, and are designated by 59u, 59v, and 59w when they are to be distinguished from one another. The protection circuit 59 includes a threshold voltage adjustment unit 60 and an overcurrent stop signal output unit 62. The overcurrent stop signal output unit 62 includes a comparator 42p that outputs a positive-side overcurrent stop signal stp to the element drive circuit 40 via an output terminal 47p, and a comparator 42n that outputs a negative-side overcurrent stop signal stn to the element drive circuit 40 via an output terminal 47p. The detection voltage Vi output from the current sensors 21a, 21b, and 21c is input from an input terminal 48 to a negative terminal, which is one end of the comparators 42p and 42n, a positive overcurrent threshold Vthp is input to a positive terminal, which is the other end of the comparator 42p, and a negative overcurrent threshold Vthn is input to a positive terminal, which is the other end of the comparator 42n. The positive overcurrent threshold Vthp and the negative overcurrent threshold Vthn are reference voltages for comparison with the detection voltage Vi in the comparators 42p and 42n, respectively. The positive overcurrent threshold Vthp is a reference voltage for determining whether an overcurrent is flowing through the power semiconductor elements 3a, 3c, and 3e of the upper arm, and the negative overcurrent threshold Vthn is a reference voltage for determining whether an overcurrent is flowing through the power semiconductor elements 3b, 3d, and 3f of the lower arm. As appropriate, the signs of the detected voltages output from the current sensors 21a, 21b, and 21c are collectively referred to as Vi, and when they are to be distinguished, Viu, Viv, and Viw are used.

[0031] When an excessive current flows through the positive-side and negative-side power semiconductor elements, the comparators 42p and 42n of the overcurrent stop signal output unit 62 output an overcurrent stop signal stp and an overcurrent stop signal stn indicating a stop when the detection voltage Vi output from the current sensors 21a, 21b, and 21c exceeds a threshold voltage (positive-side overcurrent threshold Vthp and negative-side overcurrent threshold Vthn). When an overcurrent is not detected, the overcurrent stop signal stp and the overcurrent stop signal stn indicating a non-stop are output. For example, a high-level signal is output when indicating a stop, and a low-level signal is output when indicating a non-stop. When the overcurrent stop signal stp and the overcurrent stop signal stn indicating a stop are input, the element drive circuit 40 operates to turn off the power semiconductor elements 3a to 3f in which it is determined that an overcurrent flows in the power conversion device 100, as described above. The positive overcurrent threshold Vthp is adjusted based on the positive regulated voltage Vap output from the threshold voltage adjustment unit 60 and the threshold output unit 61a. The negative overcurrent threshold Vthn is adjusted based on the negative regulated voltage Van output from the threshold voltage adjustment unit 60 and the threshold output unit 61b. The threshold voltage adjustment unit 60 outputs the positive regulated voltage Vap from the positive output terminal 43p and the negative regulated voltage Van from the negative output terminal 43n based on the positive correction command signal scp input from the positive input terminal 49p and the negative correction command signal scn input from the negative input terminal 49n. The correction command signals scp and scn are command signals output from the control unit 10.

[0032] The threshold output unit 61a is connected to a wiring that connects the output terminal 43p of the threshold voltage adjustment unit 60 and the positive terminal of the comparator 42p, and the threshold output unit 61b is connected to a wiring that connects the output terminal 43n of the threshold voltage adjustment unit 60 and the positive terminal of the comparator 42n. The threshold output unit 61a is a series body in which a plurality of resistors Ra1 and Ra2 are connected in series between the power supply voltage Vpp generated inside the power conversion device 100 and the ground GND, and a connection point na between the resistors Ra1 and Ra2 is connected to the output terminal 43p and the positive terminal of the comparator 42p. The threshold output unit 61b is a series body in which a plurality of resistors Ra3 and Ra4 are connected in series between the power supply voltage Vpp and the ground GND, and a connection point nb between the resistors Ra3 and Ra4 is connected to the output terminal 43n and the positive terminal of the comparator 42n. The ground GND is a reference for the voltage of the overcurrent protection circuit 41. The value of the power supply voltage Vpp is a predetermined constant value. The positive overcurrent threshold Vthp changes according to the value of the positive regulated voltage Vap output from the threshold voltage adjustment unit 60. The negative overcurrent threshold Vthn changes according to the value of the negative regulated voltage Van output from the threshold voltage adjustment unit 60.

[0033] The protection circuit 59 for each phase of the overcurrent protection circuit 41 is outlined below. The protection circuit 59 includes comparators 42p, 42n that determine that an overcurrent has flowed through the corresponding power semiconductor elements 3a-3f by comparing the detection voltage Vi output by the corresponding current sensor 21a, 21b, 21c with overcurrent threshold voltages, i.e., a positive side overcurrent threshold Vthp and a negative side overcurrent threshold Vthn, and generate overcurrent stop signals stp, stn indicating a stop of the power semiconductor elements 3a-3f, threshold output units 61a, 61b that output overcurrent threshold voltages (positive side overcurrent threshold Vthp, negative side overcurrent threshold Vthn), and a threshold voltage adjustment unit 60 that generates adjustment voltages (positive side adjustment voltage Vap, negative side adjustment voltage Van) that cause the threshold output units 61a, 61b to output the overcurrent threshold voltages (positive side overcurrent threshold Vthp, negative side overcurrent threshold Vthn) based on a correction command signal sc output from the control unit 10, and outputs the adjustment voltages (positive side adjustment voltage Vap, negative side adjustment voltage Van) to the threshold output units 61a, 61b.

[0034] In the overview of protection circuits 59 for each phase of overcurrent protection circuit 41 described above, the “positive side” overcurrent threshold voltages, comparators, threshold output units, adjustment voltages, and correction command signals for the upper arm power semiconductor elements 3a, 3c, and 3e and the “negative side” overcurrent threshold voltages, comparators, threshold output units, adjustment voltages, and correction command signals for the lower arm power semiconductor elements 3b, 3d, and 3f are collectively expressed, but if the “positive side” for the upper arm power semiconductor elements 3a, 3c, and 3e and the “negative side” for the lower arm power semiconductor elements 3b, 3d, and 3f are expressed separately, the result is as follows. The protection circuit 59 includes a first comparator 42p that determines that an overcurrent has flowed through the upper arm power semiconductor elements 3a, 3c, 3e by comparing the detection voltage Vi output by the corresponding current sensor 21a, 21b, 21c with a positive overcurrent threshold Vthp that is a positive overcurrent threshold voltage, and generates a positive overcurrent stop signal stp that indicates a stop of the upper arm power semiconductor elements 3a, 3c, 3e by comparing the detection voltage Vi output by the corresponding current sensor 21a, 21b, 21c with a negative overcurrent threshold Vthn that is a negative overcurrent threshold voltage. The power supply circuit 42 includes a second comparator 42n that determines that an overcurrent has flowed through 3f and generates a negative overcurrent stop signal stn indicating a stop, a first threshold output unit 61a that outputs a positive overcurrent threshold Vthp that is a positive overcurrent threshold voltage, a second threshold output unit 61b that outputs a negative overcurrent threshold Vthn that is a negative overcurrent threshold voltage, and a threshold voltage adjustment unit 60 that outputs a positive adjustment voltage Vap that is a first adjustment voltage to the first threshold output unit 61a and a negative adjustment voltage Van that is a second adjustment voltage to the second threshold output unit 61b. The threshold voltage adjustment unit 60 generates the positive adjustment voltage Vap that is a first adjustment voltage based on the first correction command signal scp output from the control unit 10, and generates the negative adjustment voltage Van that is a second adjustment voltage based on the second correction command signal scn output from the control unit 10.

[0035] In addition, when the power semiconductor elements 3a, 3c, and 3e of the upper arm and the power semiconductor elements 3b, 3d, and 3f of the lower arm have different resistance to overcurrent, the power conversion device 100 of embodiment 1 may be configured to perform overcurrent protection operation only on the upper arm or lower arm which has the weaker resistance.

[0036] The overcurrent protection circuit 41 and the element drive signal sd of the first embodiment will be described with reference to FIG. 4. The overcurrent protection circuit 41 of the first embodiment includes a U-phase protection circuit 59u, a V-phase protection circuit 59v, and a W-phase protection circuit 59w. The U-phase element drive signal sda is generated based on the drive control signal scgup output from the output terminal 44 of the control unit 10 and the overcurrent stop signal stup output from the U-phase protection circuit 59u. The U-phase element drive signal sdb is generated based on the drive control signal scgun output from the output terminal 44 of the control unit 10 and the overcurrent stop signal stun output from the U-phase protection circuit 59u. The element drive signals sda and sdb turn on the power semiconductor elements 3a and 3b when they are at a high level, and turn off the power semiconductor elements 3a and 3b when they are at a low level. When an overcurrent flows through the power semiconductor element 3a in the ON state, if the positive overcurrent stop signal stup indicates a stop, the element drive circuit 40 changes the element drive signal sda from high level to low level to turn the power semiconductor element 3a into the OFF state. Also, when an overcurrent flows through the power semiconductor element 3b in the ON state, if the negative overcurrent stop signal stun indicates a stop, the element drive circuit 40 changes the element drive signal sdb from high level to low level to turn the power semiconductor element 3b into the OFF state.

[0037] In the U-phase protection circuit 59u, the detection voltage Viu output from the current sensor 21a is input to an input terminal 48, the correction command signal scup output from the output terminal 45a of the control unit 10 is input to an input terminal 49p, and the correction command signal scun output from the output terminal 45b of the control unit 10 is input to an input terminal 49n. The protection circuit 59u outputs a positive side overcurrent stop signal stup from an output terminal 47p to the element drive circuit 40, and outputs a negative side overcurrent stop signal stun from an output terminal 47n to the element drive circuit 40.

[0038] The V-phase element drive signal sdc is generated based on the drive control signal scgvp output from the output terminal 44 of the control unit 10 and the overcurrent stop signal stvp output from the V-phase protection circuit 59v. The V-phase element drive signal sdd is generated based on the drive control signal scgvn output from the output terminal 44 of the control unit 10 and the overcurrent stop signal stvn output from the V-phase protection circuit 59v. The operation of the element drive circuit 40 for the V phase is the same as the operation of the element drive circuit 40 for the U phase. For example, the element drive signals sdc and sdd turn the power semiconductor elements 3c and 3d on when they are at a high level, and turn the power semiconductor elements 3c and 3d off when they are at a low level. When an overcurrent flows through the power semiconductor element 3c in the on state, if the positive overcurrent stop signal stvp indicates a stop, the element drive circuit 40 changes the element drive signal sdc from a high level to a low level to turn the power semiconductor element 3c off. In addition, when an overcurrent flows through the power semiconductor element 3d in the on state, if the negative overcurrent stop signal stvn indicates a stop, the element drive circuit 40 changes the element drive signal sdd from high level to low level, thereby turning off the power semiconductor element 3d.

[0039] In the V-phase protection circuit 59v, the detection voltage Viv output from the current sensor 21b is input to an input terminal 48, the correction command signal scvp output from the output terminal 45c of the control unit 10 is input to an input terminal 49p, and the correction command signal scvn output from the output terminal 45d of the control unit 10 is input to an input terminal 49n. The protection circuit 59v outputs a positive side overcurrent stop signal stvp from an output terminal 47p to the element drive circuit 40, and outputs a negative side overcurrent stop signal stvn from an output terminal 47n to the element drive circuit 40.

[0040] The W-phase element drive signal sde is generated based on the drive control signal scgwp output from the output terminal 44 of the control unit 10 and the overcurrent stop signal stwp output from the W-phase protection circuit 59w. The W-phase element drive signal sdf is generated based on the drive control signal scgwn output from the output terminal 44 of the control unit 10 and the overcurrent stop signal stwn output from the W-phase protection circuit 59w. The operation of the element drive circuit 40 for the W phase is the same as the operation of the element drive circuit 40 for the U phase. The element drive signals sde and sdf turn the power semiconductor elements 3e and 3f on when they are at a high level, and turn the power semiconductor elements 3e and 3f off when they are at a low level. When an overcurrent flows through the power semiconductor element 3e in the on state, if the positive overcurrent stop signal stwp indicates a stop, the element drive circuit 40 changes the element drive signal sde from a high level to a low level to turn the power semiconductor element 3e off. In addition, when an overcurrent flows through a power semiconductor element 3f in the on state, if the negative overcurrent stop signal stwn indicates a stop, the element drive circuit 40 changes the element drive signal sdf from high level to low level, thereby turning off the power semiconductor element 3f.

[0041] In the W-phase protection circuit 59w, the detection voltage Viw output from the current sensor 21c is input to the input terminal 48, the correction command signal scwp output from the output terminal 45e of the control unit 10 is input to the input terminal 49p, and the correction command signal scwn output from the output terminal 45f of the control unit 10 is input to the input terminal 49n. The protection circuit 59w outputs a positive side overcurrent stop signal stwp from the output terminal 47p to the element drive circuit 40, and outputs a negative side overcurrent stop signal stwn from the output terminal 47n to the element drive circuit 40.

[0042] As appropriate, the symbols of the drive control signals are generally used as scg, and when they are to be distinguished, scgup, scgun, scgvp, scgvn, scgwp, and scgwn are used. The symbols of the correction command signals are generally used as sc, and when they are to be distinguished, scup, scun, scvp, scvn, scwp, scwn, scp, and scn are used. The correction command signal scp is a positive side correction command signal that does not distinguish between the U phase, the V phase, and the W phase, and the correction command signal scn is a negative side correction command signal that does not distinguish between the U phase, the V phase, and the W phase. The symbols of the overcurrent stop signals are generally used as st, and when they are to be distinguished, stup, stun, stvp, stvn, stwp, stwn, stp, and stn are used. The overcurrent stop signal stp is a positive side overcurrent stop signal that does not distinguish between the U phase, the V phase, and the W phase, and the overcurrent stop signal stn is a negative side overcurrent stop signal that does not distinguish between the U phase, the V phase, and the W phase.

[0043] The above-mentioned variation of the current sensor will be specifically described. Three examples of sensor characteristics, which are output characteristics of the current sensors 21a, 21b, and 21c, are shown in Figs. 6 to 8. The current sensors 21a, 21b, and 21c are adjusted so that the current values ​​flowing on the negative side (<0A) and the current values ​​flowing on the positive side (>0A) are output only as positive voltage values, with the arrows of the AC currents Iu, Iv, and Iw shown in Fig. 1 being positive. In Figs. 6 to 8, the horizontal axis is the current, and the vertical axis is the voltage. Note that, regarding the current, an example is shown in which the power conversion unit 110 is an inverter, but even if the power conversion unit 110 is a converter, the current sensors 21a, 21b, and 21c are adjusted so that the current values ​​flowing on the negative side (<0A) and the current values ​​flowing on the positive side (>0A) are output only as positive voltage values. For example, as shown in sensor characteristic 50, the output voltage range of the current sensor is 0 to 5V, and 2.5V in the middle is set as the output voltage when the current value is 0A. Sensor characteristic 50 is the sensor characteristic of current sensors 21a, 21b, and 21c at the time of design. In Figs. 6 to 8, the horizontal axis is current, and the vertical axis is voltage. The variation of the current sensor includes offset variation and gain variation. Sensor characteristic 50a shown in Fig. 6 is an example including offset variation, sensor characteristic 50b shown in Fig. 7 is an example including gain variation, and sensor characteristic 50c shown in Fig. 8 is an example including offset variation and gain variation.

[0044] The offset variation is a variation in which the output voltage is offset by a certain value to the positive side (increase) or negative side (decrease) with respect to the current, as shown in sensor characteristic 50a in FIG. 6, that is, an example of characteristic deviation. FIG. 6 shows an example of an offset to the positive side (increase). The gain variation is a variation in the gain (slope of the sensor characteristic) of the current sensor at the time of design, as shown in sensor characteristic 50b in FIG. 7, that is, an example of characteristic deviation. The current sensor outputs a voltage value that is amplified so that the voltage value for the current value to be detected becomes an appropriate value. FIG. 7 shows an example in which the gain of the current sensor is smaller than the design value. When the offset variation and the gain variation are included, that is, an example in which the offset variation and the gain variation are combined, it becomes as shown in sensor characteristic 50c in FIG. 8.

[0045] In the sensor characteristic 50 at the time of design, when the current to be detected is the positive side overcurrent setting value Iocp, the output voltage of the current sensor becomes the positive side overcurrent threshold value Vthp, and when the current to be detected is the negative side overcurrent setting value Iocn, the output voltage of the current sensor becomes the negative side overcurrent threshold value Vthn. In the sensor characteristic 50a including the offset variation, when the output voltage is the positive side overcurrent threshold value Vthp, the current value is the positive side cutoff current value Iocfp, and when the output voltage is the negative side overcurrent threshold value Vthn, the current value is the negative side cutoff current value Iocfn. In the case of the overcurrent protection circuit 41 using the current sensor whose sensor characteristic is the sensor characteristic 50a, when the current becomes the positive side cutoff current value Iocfp or the negative side cutoff current value Iocfn, the corresponding power semiconductor element of the power semiconductor elements 3a to 3f is turned off.

[0046] As shown in FIG. 6, in the power conversion device 150 of the comparative example using the sensor characteristic 50a in which the sensor characteristic 50 is offset to the positive side, the value of the overcurrent determined by the negative side overcurrent threshold Vthn becomes the negative side overcurrent set value Iocn at the time of design, which is the negative side cutoff current value Iocfn, resulting in a current deviation 80b, and the value of the overcurrent determined by the positive side overcurrent threshold Vthp becomes the positive side cutoff current value Iocfp at the time of design, which is the positive side overcurrent set value Iocp at the time of design, which is the negative side overcurrent set value Iocn, which is the negative side cutoff current value Iocfn, resulting in a current deviation 80a. Therefore, on the negative side of the current, the absolute value of the current increases from the set value to be cut off at the time of design, i.e., the negative side overcurrent set value Iocn, to the negative side cutoff current value Iocfn, which is the negative side cutoff current value, which is the negative side cutoff current value, which is the negative side cutoff current value, which is the negative side cutoff current value, which is the negative side cutoff current value, which is the negative side cutoff current value, which is the positive side of the current, which is the positive side of the current, which is the set value to be cut off at the time of design, i.e., the positive side overcurrent set value Iocp, which is the positive side cutoff current value Iocfp, which is the positive side of the current ...

[0047] As shown in FIG. 7, in the power conversion device 150 of the comparative example using the sensor characteristic 50c in which the gain of the sensor characteristic 50 is smaller than the design value, the value of the overcurrent determined by the negative side overcurrent threshold Vthn becomes the negative side overcurrent set value Iocn at the time of design, which becomes the negative side cutoff current value Iocfn, resulting in a current deviation 81b, and the value of the overcurrent determined by the positive side overcurrent threshold Vthp becomes the positive side overcurrent set value Iocp at the time of design, which becomes the positive side cutoff current value Iocfp, resulting in a current deviation 81a. Therefore, on the negative side of the current, the absolute value of the current increases from the set value to be cut off at the time of design, i.e., the negative side overcurrent set value Iocn, to the negative side cutoff current value Iocfn, which increases the surge at the time of cutoff. Also, on the positive side of the current, the absolute value of the current increases from the set value to be cut off at the time of design, i.e., the positive side overcurrent set value Iocp, to the positive side cutoff current value Iocfp, which increases the surge at the time of cutoff.

[0048] As shown in FIG. 8, in the power conversion device 150 of the comparative example using the sensor characteristic 50b in which the sensor characteristic 50 is offset to the positive side and has a gain smaller than the design value, the value of the overcurrent determined by the negative side overcurrent threshold Vthn becomes the negative side overcurrent set value Iocn at the time of design as the negative side cutoff current value Iocfn, resulting in a current deviation 82b, and the value of the overcurrent determined by the positive side overcurrent threshold Vthp becomes the positive side overcurrent set value Iocp at the time of design as the positive side cutoff current value Iocfp, resulting in a current deviation 82a. Therefore, on the negative side of the current, the absolute value of the current increases from the set value to be cut off at the time of design, i.e., the negative side overcurrent set value Iocn, to the negative side cutoff current value Iocfn, resulting in a large surge at the time of cutoff. Also, on the positive side of the current, the absolute value of the current increases from the set value to be cut off at the time of design, i.e., the positive side overcurrent set value Iocp, to the positive side cutoff current value Iocfp, resulting in a large surge at the time of cutoff.

[0049] Unlike the power conversion device 150 of the comparative example, the power conversion device 100 of the first embodiment generates the positive side regulated voltage Vap and the negative side regulated voltage Van so that the threshold voltage adjustment unit 60 outputs the corrected positive side overcurrent threshold Vthp from the threshold output unit 61a and outputs the corrected negative side overcurrent threshold Vthn from the threshold output unit 61b in accordance with the sensor characteristics of the mounted current sensors 21a to 21c. Examples of correction of the positive side overcurrent threshold Vthp and the negative side overcurrent threshold Vthn of the first embodiment are shown in Figs. 9 to 11. The first correction example of the overcurrent threshold shown in Fig. 9 is a correction example for the sensor characteristic 50a including the offset variation in Fig. 6. The second correction example of the overcurrent threshold shown in Fig. 10 is a correction example for the sensor characteristic 50b including the gain variation in Fig. 7. The third correction example of the overcurrent threshold shown in Fig. 11 is a correction example for the sensor characteristic 50c including the offset variation and the gain variation in Fig. 8.

[0050] In Figs. 9 to 11, the horizontal axis is current and the vertical axis is voltage. The positive side overcurrent threshold and the negative side overcurrent threshold at the time of design are Vth0p and Vth0n, respectively. At the time of design, in the sensor characteristic 50, the positive side overcurrent threshold Vth0p is set for the positive side overcurrent setting value Iocp, and the negative side overcurrent threshold Vth0n is set for the negative side overcurrent setting value Iocn. The initial positive side overcurrent threshold Vth0p is corrected to the positive side overcurrent threshold Vthap by the voltage correction amount 83a, and the initial negative side overcurrent threshold Vth0n is corrected to the negative side overcurrent threshold Vthan by the voltage correction amount 83b. Figs. 9 to 11 will be specifically explained.

[0051] In the first correction example of FIG. 9, the sensor characteristic 50a is offset from the sensor characteristic 50 to the positive side, so the voltage correction amount 83a and the voltage correction amount 83b are the difference voltages from the sensor characteristic 50 to the sensor characteristic 50a at each current value. The voltage correction amount 83a and the voltage correction amount 83b have a positive (+) sign in the case of an increase and a negative (-) sign in the case of a decrease. In FIG. 9, the signs of the voltage correction amount 83a and the voltage correction amount 83b are both positive. The positive side overcurrent threshold Vthp is corrected from the initial positive side overcurrent threshold Vth0p to the positive side overcurrent threshold Vthap, so that the power conversion device 100 of the first embodiment can turn off the target power semiconductor element through which an overcurrent flows at the positive side overcurrent setting value Iocp at the time of design. Similarly, the negative side overcurrent threshold Vthn is corrected from the initial negative side overcurrent threshold Vth0n to the negative side overcurrent threshold Vthan, so that the power conversion device 100 of embodiment 1 can turn off the target power semiconductor element through which an overcurrent is flowing at the negative side overcurrent setting value Iocn at the time of design.

[0052] In the second correction example of FIG. 10, the sensor characteristic 50b has a smaller gain than the sensor characteristic 50, so that the signs of the voltage correction amount 83a and the voltage correction amount 83b are different on the positive side and the negative side of the current. The sign of the voltage correction amount 83a is negative, and the sign of the voltage correction amount 83b is positive. In the second correction example of FIG. 10, as in the first correction example, the positive side overcurrent threshold Vthp is corrected from the initial positive side overcurrent threshold Vth0p to the positive side overcurrent threshold Vthap, so that the power conversion device 100 of the first embodiment can turn off the target power semiconductor element through which an overcurrent flows at the positive side overcurrent setting value Iocp at the time of design. Similarly, the negative side overcurrent threshold Vthn is corrected from the initial negative side overcurrent threshold Vth0n to the negative side overcurrent threshold Vthan, so that the power conversion device 100 of the first embodiment can turn off the target power semiconductor element through which an overcurrent flows at the negative side overcurrent setting value Iocn at the time of design.

[0053] In the third correction example of FIG. 11, the sensor characteristic 50c is offset from the sensor characteristic 50 to the positive side, and the gain is small, so that the signs of the voltage correction amount 83a and the voltage correction amount 83b are different on the positive side and the negative side of the current. The sign of the voltage correction amount 83a is negative, and the sign of the voltage correction amount 83b is positive. In the third correction example of FIG. 11, as in the first and second correction examples, the positive side overcurrent threshold Vthp is corrected from the initial positive side overcurrent threshold Vth0p to the positive side overcurrent threshold Vthap, so that the power conversion device 100 of the first embodiment can turn off the target power semiconductor element through which an overcurrent flows at the positive side overcurrent setting value Iocp at the time of design. Similarly, the negative side overcurrent threshold Vthn is corrected from the initial negative side overcurrent threshold Vth0n to the negative side overcurrent threshold Vthan, so that the power conversion device 100 of the first embodiment can turn off the target power semiconductor element through which an overcurrent flows at the negative side overcurrent setting value Iocn at the time of design.

[0054] The power conversion device 100 of the first embodiment corrects the positive side overcurrent threshold Vthp and the negative side overcurrent threshold Vthn in accordance with the sensor characteristics of the current sensors 21a-21c, and therefore, unlike the power conversion device 150 of the comparative example, it is possible to reduce the overcurrent flowing through the power semiconductor elements 3a-3f during overcurrent protection operation of the power semiconductor elements 3a-3f without greatly exceeding the overcurrent setting value at the time of design. Furthermore, the power conversion device 100 of the first embodiment corrects the positive side overcurrent threshold Vthp and the negative side overcurrent threshold Vthn in accordance with the sensor characteristics of the current sensors 21a-21c, and therefore, unlike the power conversion device 150 of the comparative example, it is possible to prevent the power semiconductor elements 3a-3f from being turned off in the normal operating range during overcurrent protection operation of the power semiconductor elements 3a-3f.

[0055] In the power conversion device 100 of the first embodiment, the threshold voltage adjustment unit 60 of the overcurrent protection circuit 41 receives a correction command signal sc from the control unit 10 and corrects the adjustment voltages (positive side adjustment voltage Vap, negative side adjustment voltage Van) so that the overcurrent thresholds (positive side overcurrent threshold Vthp, negative side overcurrent threshold Vthn) corresponding to the sensor characteristics of each current sensor 21a to 21c are output from the threshold output units 61a and 61b, thereby suppressing the current value during overcurrent protection operation from deviating from the design value, i.e., the set value at the time of design. For this reason, the control unit 10 previously stores voltage correction amounts 83a and 83b (see FIGS. 9 to 11) for correcting the overcurrent thresholds (positive side overcurrent threshold Vthp, negative side overcurrent threshold Vthn) or correction sensor characteristics 55 (see FIG. 13) which are voltage correction amount data.

[0056] A method of checking the sensor characteristics including the variations of the current sensors 21a to 21c will be described. The power conversion device 100 of the first embodiment checks the variations of the sensors in a shipping inspection at the time of shipment. For example, in the case of a current sensor, a predetermined current is applied to each current sensor, or a predetermined current is applied to the wiring to be detected, and the output voltage at that time is recorded. For example, in FIG. 12, the output voltage at about three points of a specified current value (positive side, negative side) including 0 A is recorded, so that a corrected sensor characteristic 55 that is actually measured in advance can be obtained. In FIG. 12, the horizontal axis is current, and the vertical axis is voltage. The corrected current value I1 is a positive side specified current value for calibration, and the corrected current value I2 is a negative side specified current value for calibration. The measurement data 53a, 53b, and 53c are output voltages of the current sensors when the current is the corrected current value I1, 0 A, and the corrected current value I2, respectively. The corrected sensor characteristic 55 can be expressed by the relationship between the voltage V and the current I by the formula V=αI+β. α and β are constants, with constant α corresponding to the gain amount and constant β corresponding to the offset amount when current I is 0 A. Therefore, the gain amount and offset amount can be estimated from corrected sensor characteristic 55. Note that FIG. 12 also shows sensor characteristic 54 at the time of design. In sensor characteristic 54, the relationship between voltage V and current I can be expressed by the equation V=aI+b. a and b are constants, with constant a corresponding to the gain amount and constant b corresponding to the offset amount when current I is 0 A.

[0057] Each of the magnetic field detection type current sensors 21a to 21c is a hardware configuration of a core and a circuit, and it is not realistic to change the constants, parts, etc., individually every time a variation occurs. For this reason, the current sensors 21a to 21c of the power conversion device 100 have characteristics such as the corrected sensor characteristic 55, and by grasping the characteristics in advance, the control unit 10 such as a microcomputer can generate a corrected command signal sc so that the threshold output units 61a and 61b of the overcurrent protection circuit 41 output overcurrent thresholds (positive side overcurrent threshold Vthp, negative side overcurrent threshold Vthn) according to the sensor characteristics of each of the current sensors 21a to 21c. Since the positive side overcurrent set value Iocp and the negative side overcurrent set value Iocn are set in advance, if the corrected sensor characteristic 55, which is the voltage correction amounts 86a and 86b or the voltage correction amount data shown in FIG. 13, is stored, the control unit 10 generates a corrected command signal sc based on the voltage correction amounts 86a and 86b or the voltage correction amount 86a and 86b calculated from the voltage correction amount data. The threshold voltage adjustment unit 60 of the overcurrent protection circuit 41 generates adjustment voltages (positive side adjustment voltage Vap, negative side adjustment voltage Van) based on the corrected command signal sc so that the threshold output units 61a, 61b output overcurrent thresholds (positive side overcurrent threshold Vthp, negative side overcurrent threshold Vthn) according to the sensor characteristics of each of the current sensors 21a to 21c. For example, the threshold voltage adjustment unit 60 generates adjustment voltages (positive side adjustment voltage Vap, negative side adjustment voltage Van) so that the overcurrent thresholds (positive side overcurrent threshold Vthp, negative side overcurrent threshold Vthn) approach the command value of the corrected command signal sc. For example, the threshold voltage adjustment unit 60 includes a DA converter (digital-analog converter) and generates adjustment voltages (positive side adjustment voltage Vap, negative side adjustment voltage Van) based on the input digital corrected command signal sc.

[0058] If the corrected sensor characteristic 55 is stored, the control unit 10 such as a microcomputer can perform AD conversion of the analog voltages of the current sensors 21a to 21c using an AD converter (analog-digital converter) included in the control unit 10, and can correctly estimate the current value. In this case, the control unit 10 can change the drive control signal scg based on signs that an overcurrent is flowing in the AC currents Iu, Iv, and Iw, thereby avoiding or reducing the overcurrent.

[0059] Up to now, the first power conversion device 100 of the first embodiment has been described, but is not limited to this example. In the overcurrent protection operation of the power semiconductor elements 3a to 3f, factors that cause the overcurrent to be larger than the setting include gain variation and offset variation in the output characteristics of the current sensors 21a to 21c, as well as temperature-dependent changes in the output characteristics of the current sensors 21a to 21c. Next, a second power conversion device 100 that takes into account the temperature dependency of the output characteristics of the current sensors 21a to 21c will be described.

[0060] 14 is different from the first power conversion apparatus 100 in that it includes a temperature sensor 22 that detects the temperatures of the current sensors 21a to 21c, and the control unit 10 generates a correction command signal sc based on a temperature detection value Ta that is temperature information detected by the temperature sensor 22. The differences from the first power conversion apparatus 100 will be mainly described.

[0061] The temperature sensor 22 is disposed near the current sensors 21a to 21c. FIG. 14 shows an example in which the temperature sensor 22 is disposed near the current sensor 21c. The AC wiring 19u, the AC wiring 19v, and the AC wiring 19w are usually disposed close to each other, so there is no large difference in temperature between the current sensors 21a to 21c. The temperature sensor 22 outputs a temperature detection value Ta, which is detected temperature information, to the control unit 10 via a signal line 31e. FIG. 15 shows sensor characteristics 56a, 56b, and 56c at a plurality of temperatures. In FIG. 15, the horizontal axis represents current, and the vertical axis represents voltage. For example, the sensor characteristic 56a is a characteristic at room temperature, which is a reference temperature (reference temperature). The sensor characteristic 56b is a characteristic at a temperature indicating a high temperature, for example, 105°C. The sensor characteristic 56c is a characteristic at a temperature indicating a low temperature, for example, -40°C. The room temperature is a standard temperature when measuring the temperature characteristics of the current sensor, and is 5°C to 35°C. This normal temperature range is specified as the standard condition of a test location in the JIS Z8703 of the JIS standard. The sensor characteristic 56a shown in FIG. 15 is, for example, a characteristic at 25° C. Three sensor characteristics 56a, 56b, and 56c constitute a temperature map 75. In other words, the temperature map 75 has a plurality of sensor characteristics 56a, 56b, and 56c. The sensor characteristics 56a, 56b, and 56c are also corrected sensor characteristics 55 at each temperature. The number of sensor characteristics in the temperature map 75 is not limited to three, and may be two or four or more. The reference temperature is not limited to 25° C., and may be another temperature in the normal temperature range.

[0062] The sensor characteristic 56a shown in Fig. 15 indicates a characteristic obtained by correcting the gain variation and offset variation in the output characteristic of the current sensors 21a to 21c. Therefore, the overcurrent threshold voltages at the positive side overcurrent setting value Iocp and the negative side overcurrent setting value Iocn are set to the positive side overcurrent threshold Vthap and the negative side overcurrent threshold Vthan, respectively. At the positive side overcurrent setting value Iocp, the voltage of the sensor characteristic 56a is the positive side overcurrent threshold Vthap, the voltage of the sensor characteristic 56b is the positive side overcurrent threshold Vthap1, and the voltage of the sensor characteristic 56c is the positive side overcurrent threshold Vthap2. When the temperature detection value Ta of the temperature sensor 22 changes from normal temperature to a high temperature, if the positive side overcurrent threshold is corrected to Vthap1, the power semiconductor element can be turned off by the overcurrent of the positive side overcurrent setting value Iocp. When the temperature detection value Ta of the temperature sensor 22 changes from normal temperature to a low temperature, the power semiconductor element can be turned off by the overcurrent of the positive side overcurrent setting value Iocp by correcting the positive side overcurrent threshold to Vthap2.

[0063] At the negative overcurrent setting value Iocn, the voltage of sensor characteristic 56a is the negative overcurrent threshold Vthan, the voltage of sensor characteristic 56b is the negative overcurrent threshold Vthan1, and the voltage of sensor characteristic 56c is the negative overcurrent threshold Vthan2. When the temperature detection value Ta of the temperature sensor 22 changes from normal temperature to high temperature, the power semiconductor element can be turned off with an overcurrent of the negative overcurrent setting value Iocn by correcting the positive overcurrent threshold to Vthan1. When the temperature detection value Ta of the temperature sensor 22 changes from normal temperature to low temperature, the power semiconductor element can be turned off with an overcurrent of the negative overcurrent setting value Iocn by correcting the positive overcurrent threshold to Vthan2.

[0064] When the temperature detection value Ta changes from normal temperature (25°C) to high temperature (105°C), the correction amount of the positive side overcurrent threshold Vthp due to temperature is temperature correction amount 87a, and the correction amount of the negative side overcurrent threshold Vthn due to temperature is temperature correction amount 88a. When the temperature detection value Ta changes from normal temperature (25°C) to low temperature (-40°C), the correction amount of the positive side overcurrent threshold Vthp due to temperature is temperature correction amount 87b, and the correction amount of the negative side overcurrent threshold Vthn due to temperature is temperature correction amount 88b. The temperature correction amount can also be called the voltage correction amount due to temperature.

[0065] The control unit 10 in the second power conversion device 100 includes an internal temperature map 75, estimates output characteristics of the current sensors 21a to 21c at each temperature based on the detected temperature value Ta, and outputs a correction command signal sc to the threshold voltage adjustment unit 60 of the overcurrent protection circuit 41 so as to adjust the overcurrent threshold voltage (positive side overcurrent threshold Vthp, negative side overcurrent threshold Vthn). In this case, the correction command signal sc is generated based on the total correction amount of the difference between the first voltage (positive side overcurrent threshold Vth0p, negative side overcurrent threshold Vth0n) of the current sensors 21a to 21c at the time of design and the second voltage (positive side overcurrent threshold Vthap, negative side overcurrent threshold Vthan) of the mounted current sensors 21a to 21c and the temperature correction amount. The sensor characteristics 56a, 56b, and 56c of the temperature map 75 are the characteristics of each temperature in the corrected sensor characteristic 55 that is actually measured.

[0066] As described above, the second power conversion device 100 of the first embodiment includes, as the temperature map 75, characteristic data (sensor characteristics 56a, 56b, 56c) of the output voltage relative to the current detected by the current sensors 21a to 21c, which are actually measured in advance for each of a plurality of temperatures by the control unit 10, and generates a correction command signal sc based on a total correction amount obtained by adding together the temperature correction amount and the voltage correction amount extracted based on the temperature detection value Ta, which is temperature information detected by the temperature sensor 22, and the temperature map 75. The total correction amount for the positive overcurrent setting value Iocp is the sum of the voltage correction amount 86a and the temperature correction amounts 87a and 87b. The total correction amount for the negative overcurrent setting value Iocn is the sum of the voltage correction amount 86b and the temperature correction amounts 88a and 88b. The temperature correction amount may be the amount of change in the detection voltage output by the current sensors 21a to 21c relative to the overcurrent setting value (positive overcurrent setting value Iocp, negative overcurrent setting value Iocn) based on a preset reference temperature (the normal temperature). The temperature correction amounts for the positive overcurrent setting value Iocp are temperature correction amounts 87a and 87b, and the temperature correction amounts for the negative overcurrent setting value Iocn are temperature correction amounts 88a and 88b. Even if the second power conversion device 100 of the first embodiment is equipped with current sensors 21a to 21c that have large temperature dependency, it is possible to reduce the overcurrent flowing through the power semiconductor elements during the overcurrent protection operation of the power semiconductor elements 3a to 3f.

[0067] The overcurrent detection circuit of Patent Document 1 needs to arrange a temperature characteristic correction MOSFET for each current sensor. Therefore, when a series circuit of a current detection MOSFET and a resistor corresponding to a current sensor is arranged for each of the U-phase, V-phase, and W-phase as in a three-phase inverter, and a comparator is provided for each of the positive-side and negative-side current detection MOSFETs, the circuit scale of the current sensor and the overcurrent detection circuit may become large. In contrast, the power conversion device 100 of the first embodiment can use a threshold voltage adjustment unit 60 having a relatively small circuit scale for the positive-side comparator 42p and the negative-side comparator 42n, unlike the overcurrent detection circuit of Patent Document 1, so that the circuit scale of the overcurrent protection circuit 41 and the current sensors 21a to 21c can be prevented from becoming larger than that of the overcurrent detection circuit and current of Patent Document 1. For example, when a threshold voltage adjustment unit 60 having two resistors R1 and R2 shown in FIG. 33 described later is used and a correction command signal sc, which is an analog signal, is output from the control unit 10 to the threshold voltage adjustment unit 60, the effect of reducing the circuit scale of the overcurrent protection circuit 41 is high.

[0068] As described above, the power conversion device 100 of the first embodiment controls the power conversion unit 110 having the multiple power semiconductor elements 3a, 3b, 3c, 3d, 3e, and 3f to convert DC power into AC power or AC power into DC power. The power conversion device 100 includes a drive circuit 14 that outputs an element drive signal sd for driving the multiple power semiconductor elements 3a to 3f, a control unit 10 that controls the drive circuit 14, and current sensors 21a, 21b, and 21c that detect AC currents Iu, Iv, and Iw of the power conversion unit 110. The drive circuit 14 includes an element drive circuit 40 that outputs the element drive signal sd to the power semiconductor elements 3a to 3f, and an overcurrent protection circuit 41 that determines that an overcurrent has flowed through the power semiconductor elements 3a to 3f and outputs an overcurrent stop signal st to the element drive circuit 40 to output the element drive signal sd that changes the power semiconductor elements from an on state to an off state. The overcurrent protection circuit 41 includes comparators 42p, 42n that determine that an overcurrent has flowed through the power semiconductor elements 3a-3f by comparing the detection voltages Vi (Viu, Viv, Viw) output by the current sensors 21a-21c with overcurrent threshold voltages (positive side overcurrent threshold Vthp, negative side overcurrent threshold Vthn) and generate an overcurrent stop signal st, threshold output units 61a, 61b that output the overcurrent threshold voltages (positive side overcurrent threshold Vthp, negative side overcurrent threshold Vthn), and a threshold voltage adjustment unit 60 that generates adjustment voltages (positive side adjustment voltage Vap, negative side adjustment voltage Van) that cause the threshold output units 61a, 61b to output the overcurrent threshold voltages (positive side overcurrent threshold Vthp, negative side overcurrent threshold Vthn) based on a correction command signal sc output from the control unit 10, and outputs the adjustment voltages (positive side adjustment voltage Vap, negative side adjustment voltage Van) to the threshold output units 61a, 61b.The difference between the first voltage (positive side overcurrent threshold Vth0p, negative side overcurrent threshold Vth0n) of the current sensors 21a to 21c at the time of design and the second voltage (positive side overcurrent threshold Vthap, negative side overcurrent threshold Vthan) of the installed current sensors 21a to 21c for predetermined overcurrent set values ​​(positive side overcurrent set value Iocp, negative side overcurrent set value Iocn) that turn off the power semiconductor elements 3a to 3f is set as voltage correction amounts 86a, 86b, and the control unit 10 generates a correction command signal sc based on the voltage correction amounts 86a, 86b stored in advance or the voltage correction amount 86a, 86b calculated from the voltage correction amount data (correction sensor characteristic 55) stored in advance. With this configuration, the power conversion device 100 of the first embodiment outputs a correction command signal sc generated by the control unit 10 based on the pre-stored voltage correction amounts 86a, 86b or the voltage correction amounts 86a, 86b calculated from the pre-stored voltage correction amount data (corrected sensor characteristic 55) to the overcurrent protection circuit 41, and when an overcurrent flows, the overcurrent protection circuit 41 generates an overcurrent stop signal st by comparing the overcurrent threshold voltages (positive side overcurrent threshold Vthp, negative side overcurrent threshold Vthn) generated based on the correction command signal sc with the detection voltages Viu, Viv, Viw output by the current sensors 21a to 21c, and changes the power semiconductor element in which it is determined that an overcurrent is flowing from the on state to the off state, so that the overcurrent flowing in the power semiconductor elements can be reduced during the overcurrent protection operation of the power semiconductor elements 3a to 3f.

[0069] Embodiment 2 FIG. 16 is a diagram showing a configuration of a drive circuit according to the second embodiment. FIG. 17 is a diagram showing a configuration of a first protection circuit in FIG. 16, and FIG. 18 is a diagram showing a configuration of a second protection circuit in FIG. 16. FIG. 19 is a diagram explaining a duty ratio. FIG. 20 is a diagram showing an output voltage characteristic of a smoothing circuit that smoothes the pulse signal Vpi in FIG. 17 and FIG. 18, and FIG. 21 is a diagram showing an output voltage characteristic of a smoothing circuit that smoothes the pulse signal Vpia in FIG. 18. FIG. 22, FIG. 23, and FIG. 24 are diagrams showing a first example, a second example, and a third example of an overcurrent threshold characteristic of a first protection circuit according to the second embodiment, respectively. FIG. 25, FIG. 26, and FIG. 27 are diagrams showing a first example, a second example, and a third example of an overcurrent threshold characteristic of a second protection circuit according to the second embodiment, respectively. FIG. 28 is a diagram showing a first correction example of an overcurrent threshold of a protection circuit according to the second embodiment. FIG. 29, FIG. 30, and FIG. 31 are diagrams showing a second correction example of an overcurrent threshold of a protection circuit according to the second embodiment, respectively.

[0070] The power conversion device 100 of the second embodiment differs from the power conversion device 100 of the first embodiment in that a positive side overcurrent threshold Vthp and a negative side overcurrent threshold Vthn are output from one threshold output unit 61 to two comparators 42p, 42n, respectively, and in that the number of output terminals for outputting the correction command signal sc of the control unit 10 is reduced. The differences from the power conversion device 100 of the first embodiment will be mainly described.

[0071] The components of the power conversion device 100 of the second embodiment are the same as those of the power conversion device 100 of the first embodiment shown in Figs. 1 and 14. However, the configuration of the protection circuit 59 and the number of output terminals of the control unit 10 are different. In the power conversion device 100 of the first embodiment, the power conversion unit 110 of a three-phase inverter has been described. When blocking a positive overcurrent and a negative overcurrent in the AC current of the U-phase, V-phase, and W-phase of a three-phase AC, six correction command signals sc for correcting the respective overcurrent thresholds are required, and the control unit 10 needs six output terminals 45a to 45f for outputting the six correction command signals sc, respectively. For example, when the control unit 10 is an existing microcomputer, it is considered that the number of output terminals for outputting the correction command signals sc is insufficient. In the second embodiment, an overcurrent protection circuit 41 is described in which the number of output terminals for outputting the correction command signals sc is reduced and multiple threshold voltages can be corrected with one correction command signal sc. Thanks to this overcurrent protection circuit 41, the power conversion device 100 of embodiment 2 has the same effect as the power conversion device 100 of embodiment 1, and can reduce power consumption as the number of output terminals of the control unit 10 is reduced, and the cost of the control unit 10 can also be reduced.

[0072] The control unit 10 and the drive circuit 14 of the second embodiment shown in FIG. 16 will be described below in terms of differences from the control unit 10 and the drive circuit 14 of the first embodiment shown in FIG. 4. The control unit 10 of the second embodiment has three output terminals 45a, 45c, and 45e, and outputs a correction command signal scu to a protection circuit 59u for the U phase from the output terminal 45a, outputs a correction command signal scv to a protection circuit 59v for the V phase from the output terminal 45c, and outputs a correction command signal scw to a protection circuit 59w for the W phase from the output terminal 45e. The input terminals to which the correction command signal sc is input in the protection circuits 59u, 59v, and 59w are changed from two input terminals 49p and 49n to one input terminal 49. As described above, the code of the correction command signal is generally sc. When the correction command signals are to be distinguished from one another, the codes scu, scv, and scw are used for the correction command signals.

[0073] The protection circuit 59u, the protection circuit 59v, and the protection circuit 59w have the configuration shown in FIG. 17 or the configuration shown in FIG. 18. The first protection circuit 59 shown in FIG. 17 is configured in a case where the offset variation of the current sensors 21a to 21c is dominant, and the second protection circuit 59 shown in FIG. 18 is configured in a case where the gain variation of the current sensors 21a to 21c is dominant. First, the first protection circuit 59 shown in FIG. 17 will be described. The threshold voltage adjustment unit 60 includes two smoothing circuits 65a and 65b that smooth the pulse signal Vpi, resistors R1 and R2, an input terminal 49 to which a correction command signal sc is input, an output terminal 43p that outputs a positive side adjustment voltage Vap, and an output terminal 43n that outputs a negative side adjustment voltage Van. The smoothing circuit 65a that outputs the adjustment source voltage Vsp is appropriately referred to as the first smoothing circuit, and the smoothing circuit 65b that outputs the adjustment source voltage Vsn is appropriately referred to as the second smoothing circuit. The correction command signal sc in the second embodiment is a pulse signal Vpi having a duty ratio Du. The duty ratio Du is the ratio of the high period Th of the pulse signal Vpi to the pulse period Tf, ie, it can be expressed as Th / Tf.

[0074] The first smoothing circuit 65a smoothes the pulse signal Vpi to generate an adjustment source voltage Vsp. The second smoothing circuit 65b smoothes the pulse signal Vpi to generate an adjustment source voltage Vsn. The first smoothing circuit 65a and the second smoothing circuit 65b output a voltage from 0V to a maximum voltage value Vsa according to the duty ratio Du of the pulse signal Vpi. In FIG. 17, the first smoothing circuit 65a is an example of an RC filter circuit having a resistor Rb1 and a capacitor C1, and the second smoothing circuit 65b is an example of an RC filter circuit having a resistor Rb2 and a capacitor C2. The number of RC filter circuits is not limited to one, and multiple RC filter circuits may be connected.

[0075] The adjustment source voltages Vsp and Vsn are proportional to the duty ratio Du of the pulse signal Vpi and range from 0V to the maximum voltage value Vsa as shown in output voltage characteristic 67 in Fig. 20. In Fig. 20, the horizontal axis is the duty ratio Du of the pulse signal Vpi, and the vertical axis is the voltage. For example, when the maximum voltage value Vsa is 5V, the adjustment source voltages Vsp and Vsn are 0V when the duty ratio Du is 0, and are 5V when the duty ratio Du is 1.

[0076] One end of the resistor R1 is connected to a connection point n1 between the resistor Rb1 and the capacitor C1, and the other end is connected to the output terminal 43p. One end of the resistor R2 is connected to a connection point n2 between the resistor Rb2 and the capacitor C2, and the other end is connected to the output terminal 43n. The connection point n1 of the first smoothing circuit 65a is an output point that outputs the adjustment source voltage Vsp, and the connection point n2 of the second smoothing circuit 65b is an output point that outputs the adjustment source voltage Vsn. The adjustment source voltage Vsp output from the output point of the first smoothing circuit 65a is output from the output terminal 43p via the resistor R1 as a positive-side adjustment voltage Vap (see FIG. 5). The adjustment source voltage Vsn output from the output point of the second smoothing circuit 65b is output from the output terminal 43n via the resistor R2 as a negative-side adjustment voltage Van (see FIG. 5).

[0077] The overcurrent stop signal output unit 62 includes a comparator 42p that outputs a positive overcurrent stop signal stp to the element drive circuit 40, a comparator 42n that outputs a negative overcurrent stop signal stn to the element drive circuit 40, and a threshold output unit 61 that outputs a positive overcurrent threshold Vthp and a negative overcurrent threshold Vthn based on a positive regulated voltage Vap and a negative regulated voltage Van. The detection voltage Vi output from the current sensors 21a, 21b, and 21c is input from the input terminal 48 to a negative terminal that is one end of the comparators 42p and 42n, a positive overcurrent threshold Vthp is input to a positive terminal that is the other end of the comparator 42p, and a negative overcurrent threshold Vthn is input to a positive terminal that is the other end of the comparator 42n. The threshold output unit 61 is a series body in which a plurality of resistors R3, R4, and R5 are connected in series between a power supply voltage Vpp generated inside the power conversion device 100 and the ground GND. The resistors R3, R4, and R5 of the threshold output unit 61 are a first resistor, a second resistor, and a third resistor, respectively. A connection point n3, which is a first connection point where the first resistor (resistor R3) and the second resistor (resistor R4) on the power supply voltage Vpp side are connected, is connected to an output terminal 43p of the threshold voltage adjustment unit 60 and a positive-side comparator 42p. A connection point n4, which is a second connection point where the third resistor (resistor R5) and the second resistor (resistor R4) on the ground GND side are connected, is connected to an output terminal 43n of the threshold voltage adjustment unit 60 and a negative-side comparator 42n.

[0078] The positive side overcurrent threshold Vthp and the negative side overcurrent threshold Vthn output from the threshold output unit 61 of the first protection circuit 59 shown in Fig. 17 will be described. The positive side overcurrent threshold Vthp and the negative side overcurrent threshold Vthn are generated by the resistors R3, R4, and R5 of the threshold output unit 61, the power supply voltage Vpp of the threshold output unit 61, and the adjustment source voltages Vsp and Vsn. Specifically, the resistors R3, R4, and R5 are connected in series between the power supply voltage Vpp and the ground GND, and the positive side overcurrent threshold Vthp output from the connection point n3 between the resistors R3 and R4 is generated by the resistance voltage division value of the resistors R3, R4, and R5 and the positive side adjustment voltage Vap, which is the adjustment source voltage Vsp based on the duty ratio Du of the pulse signal Vpi output from the control unit 10 and output to the connection point n3 via the resistor R1. Moreover, the negative overcurrent threshold Vthn output from the connection point n4 between the resistors R4 and R5 is generated by the resistor divided value of the resistors R3, R4, and R5 and the negative regulated voltage Van, which is the regulated source voltage Vsn based on the duty ratio Du of the pulse signal Vpi output from the control unit 10 and output to the connection point n4 via the resistor R2. The positive overcurrent threshold Vthp changes in response to the changes in the regulated source voltage Vsp and the positive regulated voltage Vap as the duty ratio Du of the pulse signal Vpi changes. Similarly, the negative overcurrent threshold Vthn changes in response to the changes in the regulated source voltage Vsn and the negative regulated voltage Van as the duty ratio Du of the pulse signal Vpi changes.

[0079] 22 to 24 show first to third examples of the overcurrent threshold characteristic in the first protection circuit 59, respectively. In FIG. 22 to FIG. 24, the horizontal axis is the duty ratio Du of the pulse signal Vpi, and the vertical axis is the voltage. In FIG. 22 to FIG. 24, an example in which the maximum voltage value Vsa is 5.0V is shown. In FIG. 22 to FIG. 24, the resistances R1 and R2 of the threshold voltage adjustment unit 60 and the resistances R3, R4, and R5 of the threshold output unit 61 are different in size. The resistance values ​​of the resistances R1, R2, R3, R4, and R5 are simply represented as R1, R2, R3, R4, and R5 as appropriate. The first example of the overcurrent threshold characteristic in FIG. 22 is a case in which R1=R2 and R1, R2>>R3, R4, and R5 (first resistance condition). A second example of the overcurrent threshold characteristic in Fig. 23 is a case where R1 = R2, and R1, R2 ≈ R3, R4, R5 (second resistance condition). A third example of the overcurrent threshold characteristic in Fig. 24 is a case where R1 >> R3, R4, R5, and R2 ≈ R3, R4, R5 (third resistance condition). The relationship between the positive side overcurrent threshold Vthp and the duty ratio Du is shown as positive side overcurrent threshold characteristics 92a, 92b, and 92c. The relationship between the negative side overcurrent threshold Vthn and the duty ratio Du is shown as negative side overcurrent threshold characteristics 93a, 93b, and 93c.

[0080] 22 to 24, it can be seen that the positive side overcurrent threshold Vthp and the negative side overcurrent threshold Vthn change depending on the values ​​of the resistors R1, R2 of the threshold voltage adjustment unit 60. As shown in Fig. 23, when the values ​​of the resistors R1, R2 of the threshold voltage adjustment unit 60 are equivalent to the values ​​of the resistors R3 to R4 of the threshold output unit 61, the slopes of the positive side overcurrent threshold characteristic 92b and the negative side overcurrent threshold characteristic 93b with respect to the duty ratio Du become larger, and the positive side overcurrent threshold Vthp and the negative side overcurrent threshold Vthn are significantly affected by the adjustment source voltages Vsp, Vsn. In contrast, when the values ​​of resistors R1, R2 of threshold voltage adjustment unit 60 are increased, as shown in FIG. 22, the slopes of positive side overcurrent threshold characteristic 92a and negative side overcurrent threshold characteristic 93a with respect to duty ratio Du become smaller than those of positive side overcurrent threshold characteristic 92b and negative side overcurrent threshold characteristic 93b in FIG. 23, and the positive side overcurrent threshold Vthp and negative side overcurrent threshold Vthn are not significantly affected by the adjustment source voltages Vsp, Vsn, as shown in FIG.

[0081] The positive overcurrent threshold Vthp can be corrected from the initial positive overcurrent threshold Vth0p to the positive overcurrent threshold Vthap by changing the duty ratio Du. Similarly, the negative overcurrent threshold Vthn can be corrected from the initial negative overcurrent threshold Vth0n to the negative overcurrent threshold Vthan by changing the duty ratio Du. In addition, the slopes of the positive overcurrent threshold characteristic and the negative overcurrent threshold characteristic can be adjusted by adjusting the values ​​of the resistors R1 and R2 of the threshold voltage adjustment unit 60. Since the correction command signal sc output from the control unit 10 is a pulse signal Vpi having the duty ratio Du, it is necessary to realize the voltage correction amount 86a (see FIG. 13) of the positive overcurrent threshold Vthp and the voltage correction amount 86b (see FIG. 13) of the negative overcurrent threshold Vthn by only changing the duty ratio Du. By adjusting the values ​​of resistors R1 and R2 of the threshold voltage adjuster 60 in advance for each of the current sensors 21a to 21c, the voltage correction amount 86a for the positive overcurrent threshold Vthp and the voltage correction amount 86b for the negative overcurrent threshold Vthn can be realized by changing the duty ratio Du.

[0082] Next, the second protection circuit 59 shown in FIG. 18 will be described. The second protection circuit 59 shown in FIG. 18 is different from the first protection circuit 59 shown in FIG. 17 in that an inverter 63 is added to the threshold voltage adjustment unit 60, and the smoothing circuit 65b that outputs the negative adjustment source voltage Vsn is changed to a smoothing circuit 66 that outputs the negative adjustment source voltage Vsn by the pulse signal Vpia output from the inverter 63. The smoothing circuit 65a that smoothes the pulse signal Vpi is designated by the reference symbol 65. As appropriate, the smoothing circuit 65 that outputs the adjustment source voltage Vsp is referred to as the first smoothing circuit, and the smoothing circuit 66 that outputs the adjustment source voltage Vsn is referred to as the second smoothing circuit. The differences from the first protection circuit 59 will be mainly described. The first smoothing circuit 65 smoothes the pulse signal Vpi to generate the adjustment source voltage Vsp from the connection point n1, which is the output point. The second smoothing circuit 66 smoothes the pulse signal Vpia inverted by the inverter 63 from the pulse signal Vpi, and generates the adjustment source voltage Vsn from the connection point n2, which is the output point.

[0083] The adjustment source voltage Vsp is a voltage between 0 V and the maximum voltage value Vsa proportional to the duty ratio Du of the pulse signal Vpi as shown in output voltage characteristic 67 in Fig. 20. On the other hand, the adjustment source voltage Vsn generated by the inverter 63 from the pulse signal Vpia, which is an inverted pulse of the pulse signal Vpi, changes like the output voltage characteristic 68 shown in Fig. 21, which is a left-right inversion of the output voltage characteristic 67 in Fig. 20.

[0084] 25 to 27 show first to third examples of the overcurrent threshold characteristic in the second protection circuit 59, respectively. FIGS. 25 to 27 show the same horizontal and vertical axes as FIGS. 22 to 24, and show an example in which the maximum voltage value Vsa is 5.0 V. The first example of the overcurrent threshold characteristic in FIG. 25 is for the same first resistance condition as FIG. 22. The second example of the overcurrent threshold characteristic in FIG. 26 is for the same second resistance condition as FIG. 23. The third example of the overcurrent threshold characteristic in FIG. 27 is for the same third resistance condition as FIG. 24. The relationship between the positive side overcurrent threshold Vthp and the duty ratio Du is shown as positive side overcurrent threshold characteristics 92d, 92e, and 92f. The relationship between the negative side overcurrent threshold Vthn and the duty ratio Du is shown as negative side overcurrent threshold characteristics 93d, 93e, and 93f.

[0085] 22 to 24, Figures 25 to 27 also show that the positive side overcurrent threshold Vthp and the negative side overcurrent threshold Vthn change depending on the values ​​of the resistors R1, R2 of the threshold voltage adjustment unit 60. As shown in Figure 26, when the values ​​of the resistors R1, R2 of the threshold voltage adjustment unit 60 are equivalent to the values ​​of the resistors R3 to R4 of the threshold output unit 61, the slopes of the positive side overcurrent threshold characteristic 92e and the negative side overcurrent threshold characteristic 93e with respect to the duty ratio Du become larger, and the positive side overcurrent threshold Vthp and the negative side overcurrent threshold Vthn are significantly affected by the adjustment source voltages Vsp, Vsn. In contrast, when the values ​​of resistors R1, R2 of threshold voltage adjustment unit 60 are increased, as shown in FIG. 25, the slopes of positive side overcurrent threshold characteristic 92d and negative side overcurrent threshold characteristic 93d with respect to duty ratio Du become smaller than those of positive side overcurrent threshold characteristic 92e and negative side overcurrent threshold characteristic 93e in FIG. 26, and the positive side overcurrent threshold Vthp and negative side overcurrent threshold Vthn are not significantly affected by the adjustment source voltages Vsp, Vsn, as shown in FIG.

[0086] In the second protection circuit 59, similarly to the first protection circuit 59, the positive side overcurrent threshold Vthp can be corrected from the initial positive side overcurrent threshold Vth0p to the positive side overcurrent threshold Vthap by changing the duty ratio Du. Similarly, the negative side overcurrent threshold Vthn can be corrected from the initial negative side overcurrent threshold Vth0n to the negative side overcurrent threshold Vthan by changing the duty ratio Du. In addition, the slopes of the positive side overcurrent threshold characteristic and the negative side overcurrent threshold characteristic can be adjusted by adjusting the values ​​of the resistors R1 and R2 of the threshold voltage adjustment unit 60. In the second protection circuit 59, similarly to the first protection circuit 59, the voltage correction amount 86a of the positive side overcurrent threshold Vthp and the voltage correction amount 86b of the negative side overcurrent threshold Vthn can be realized by changing the duty ratio Du by adjusting in advance the values ​​of the resistors R1 and R2 of the threshold voltage adjustment unit 60 for each of the current sensors 21a to 21c.

[0087] The overcurrent protection circuit 41 of the second embodiment includes a protection circuit 59 corresponding to each phase of the three-phase AC. The protection circuit 59 includes a first comparator 42p that determines that an overcurrent has flowed through the upper arm power semiconductor elements 3a, 3c, and 3e by comparing the detection voltage Vi output by the current sensors 21a to 21c with a positive side overcurrent threshold voltage (positive side overcurrent threshold Vthp) and outputs a positive side overcurrent stop signal stp, a second comparator 42n that determines that an overcurrent has flowed through the lower arm power semiconductor elements 3b, 3d, and 3f by comparing the detection voltage Vi output by the current sensors 21a to 21c with a negative side overcurrent threshold voltage (negative side overcurrent threshold Vthn) and outputs a negative side overcurrent stop signal stn, a threshold output unit 61 that outputs the positive side overcurrent threshold voltage (positive side overcurrent threshold Vthp) and the negative side overcurrent threshold voltage (negative side overcurrent threshold Vthn), and a threshold voltage adjustment unit 60 that outputs a first regulated voltage (positive side regulated voltage Vap) and a second regulated voltage (negative side regulated voltage Van) to the threshold output unit 61. The threshold voltage adjusting unit 60 generates a first regulated voltage (positive-side regulated voltage Vap) and a second regulated voltage (negative-side regulated voltage Van) based on the correction command signal sc output from the control unit 10. In the power conversion device 100 of the second embodiment, the protection circuit 59 can generate two overcurrent stop signals stp, stn based on one correction command signal sc, so that the number of output terminals of the control unit 10 can be reduced, and the power consumption can be reduced with the reduction in the number of output terminals of the control unit 10, and the cost of the control unit 10 can also be reduced.

[0088] A method of correcting the positive side overcurrent threshold Vthp and the negative side overcurrent threshold Vthn in each protection circuit 59 of the overcurrent protection circuit 41 of the second embodiment and the operation of the power conversion device 100 of the second embodiment will be described with reference to Figs. 28 to 31. The method of correcting the positive side overcurrent threshold Vthp and the negative side overcurrent threshold Vthn is the same for both the first protection circuit 59 and the second protection circuit 59, but the second protection circuit 59 will be described as a representative. Figs. 28 to 31 are an example similar to the overcurrent value characteristic of Fig. 26 in the second protection circuit 59, in which gain variation is dominant, the resistors R1 to R5 are in the second resistance condition, and the maximum voltage value Vsa is 5.0V. In Figs. 28 to 31, the horizontal axis represents the duty ratio Du of the pulse signal Vpi, and the vertical axis represents the voltage. 28 to 31, the relationship between the positive overcurrent threshold Vthp and the duty ratio Du is shown as positive overcurrent threshold characteristics 94a and 94b, and the relationship between the negative overcurrent threshold Vthn and the duty ratio Du is shown as negative overcurrent threshold characteristics 95a and 95b.

[0089] Consider a case where the default positive side overcurrent threshold Vthp and negative side overcurrent threshold Vthn input to the comparators 42p and 42n, i.e., the positive side overcurrent threshold Vthp and the negative side overcurrent threshold Vthn at the time of design are the positive side overcurrent threshold Vth0p and the negative side overcurrent threshold Vth0n, and correction is required to set them to the positive side overcurrent threshold Vthap and the negative side overcurrent threshold Vthan. The positive side overcurrent threshold Vthap and the negative side overcurrent threshold Vthan are calculated using the corrected sensor characteristic 55 shown in FIG. 13. Alternatively, as described in the first embodiment, they may be calculated using the voltage correction amounts 86a and 86b that are calculated in advance from the corrected sensor characteristic 55 and stored. The control unit 10 adds the voltage correction amount 86a to the positive side overcurrent threshold Vth0p to calculate the positive side overcurrent threshold Vthap, and subtracts the voltage correction amount 86b from the negative side overcurrent threshold Vth0n to calculate the negative side overcurrent threshold Vthan. First, a first correction example will be described with reference to FIG. 28. To change the positive overcurrent threshold Vth0p to the positive overcurrent threshold Vthap, the positive overcurrent threshold Vthp needs to be lowered by the voltage correction amount 79a, and to change the negative overcurrent threshold Vth0n to the negative overcurrent threshold Vthan, the negative overcurrent threshold Vthn needs to be increased by the voltage correction amount 79b.

[0090] The control unit 10 changes the duty ratio Du from an initial duty ratio value d1 to a duty ratio value d2. The amount of change from the duty ratio value d1 to the duty ratio value d2 is a duty ratio change amount 78. The control unit 10 outputs a pulse signal Vpi having a duty ratio Du equal to the duty ratio value d2 as a correction command signal sc to the protection circuit 59 of the overcurrent protection circuit 41. The duty ratio change amount 78 is set in accordance with each of the current sensors 21a to 21c. The control unit 10 generates a pulse signal Vpi having a duty ratio Du corresponding to each of the current sensors 21a to 21c as the correction command signals scu, scv, and scw, and outputs the correction command signals scu, scv, and scw to the protection circuits 59u, 59v, and 59w, respectively. In this way, even if the power conversion device 100 of embodiment 2 is equipped with current sensors 21a to 21c having variations in sensor characteristics, it can turn off the power semiconductor elements 3a to 3f at predetermined overcurrent set values ​​(positive side overcurrent set value Iocp, negative side overcurrent set value Iocn) during overcurrent protection operation.

[0091] Next, consider a case where the positive side overcurrent threshold Vthap and the negative side overcurrent threshold Vthan cannot be realized with the same duty ratio change amount 78 due to the variation in the sensor characteristics of the current sensor. An example of this case is shown in Figs. 29 to 31. A second correction example will be described with reference to Figs. 29 to 31. Figs. 29 to 31 show an example in which the positive side overcurrent threshold Vthp can only be lowered to the lower limit positive side overcurrent threshold Vthpmin. In the case where the power semiconductor elements 3a to 3f are turned off in the steady operation range when the positive side overcurrent threshold Vthp falls below the lower limit positive side overcurrent threshold Vthpmin, the lower limit positive side overcurrent threshold Vthpmin is set for the positive side overcurrent threshold Vthp. Similarly, in the case where the power semiconductor elements 3a to 3f are turned off in the steady operation range when the negative side overcurrent threshold Vthn increases beyond the upper limit negative side overcurrent threshold Vthnmax, the upper limit negative side overcurrent threshold Vthnmax is set for the negative side overcurrent threshold Vthn. Note that the case where the negative overcurrent threshold Vthn exceeds the upper negative overcurrent threshold Vthnmax is the case where the differential voltage of the negative overcurrent threshold Vthn drops below the limit value when considered in terms of the differential voltage from the median value of 2.5V described in Figures 6 to 8. Therefore, both the lower limit positive overcurrent threshold Vthpmin and the upper limit negative overcurrent threshold Vthnmax are limit values ​​of the overcurrent threshold at which the steady operation of the power conversion device 100 is not hindered.

[0092] 29 to 31 assume a case where the positive side voltage correction amount 83a is smaller than the negative side voltage correction amount 83b as in the example of FIG. 11. In this case, the control unit 10 of the power conversion device 100 of the second embodiment adjusts the value of the duty ratio Du according to the smaller voltage correction amount or the limit value of the overcurrent threshold (positive side overcurrent threshold Vthap, negative side overcurrent threshold Vthan). FIG. 29 to 31 are examples of the overcurrent threshold characteristics of the second protection circuit 59 shown in FIG. 18. The characteristics of the positive side overcurrent threshold Vthp and the negative side overcurrent threshold Vthn are the positive side overcurrent threshold characteristic 94b and the negative side overcurrent threshold characteristic 95b, respectively. The positive side overcurrent threshold Vthp and the negative side overcurrent threshold Vthn set as defaults, that is, the initial positive side overcurrent threshold Vthp0 and the initial negative side overcurrent threshold Vthn0, are set by the correction command signal sc in which the value of the duty ratio Du of the pulse signal Vpi is the duty ratio value d3. That is, the control unit 10 sets the default positive side overcurrent threshold Vthp0 and negative side overcurrent threshold Vthn0 by outputting to the protection circuit 59 a correction command signal sc in which the duty ratio Du of the pulse signal Vpi is the duty ratio value d3.

[0093] The threshold voltage of the lower limit line 35 is the lower limit positive overcurrent threshold Vthpmin, and the threshold voltage of the upper limit line 36 is the upper limit negative overcurrent threshold Vthnmax. The duty ratio value lower limit line 34 is a line where the positive overcurrent threshold characteristic 94b is the lower limit positive overcurrent threshold Vthpmin. The positive side threshold settable range 39a is between the positive side overcurrent threshold Vthp0 and the lower limit positive overcurrent threshold Vthpmin indicated by the lower limit line 35. The negative side threshold settable range 39b is between the negative side overcurrent threshold Vthn0 and the upper limit negative overcurrent threshold Vthnmax indicated by the upper limit line 36. The duty ratio value lower limit line 34 has a duty ratio Du value of d4. The duty ratio Du value at which the negative overcurrent threshold characteristic 95b of the negative overcurrent threshold Vthn intersects with the upper limit line 36 is a duty ratio value d5. The range of duty ratio Du from duty ratio value d3 to duty ratio value d4 is a duty ratio adjustment range 38 in which duty ratio Du can actually be adjusted.

[0094] A positive side overcurrent threshold voltage (positive side overcurrent threshold Vthap) with respect to a duty ratio Du at a positive side overcurrent setting value (positive side overcurrent setting value Iocp) is set as first threshold data (positive side overcurrent threshold characteristic 94b), and a negative side overcurrent threshold voltage (negative side overcurrent threshold Vthan) with respect to a duty ratio Du at a negative side overcurrent setting value (negative side overcurrent setting value Iocn) is set as second threshold data (negative side overcurrent threshold characteristic 95b). The first threshold data and second threshold data are stored in advance in the control unit 10 as voltage correction amount data together with the correction sensor characteristic 55 or the voltage correction amounts 86a and 86b. The control unit 10 calculates a first overcurrent threshold V1, which is a positive side overcurrent threshold voltage (positive side overcurrent threshold Vthp) for a positive side overcurrent setting value (positive side overcurrent setting value Iocp), from the corrected sensor characteristic 55, which is the first characteristic data, within a positive side settable range (threshold settable range 39a), and calculates a second overcurrent threshold V2, which is a negative side overcurrent threshold voltage (negative side overcurrent threshold Vthn) for a negative side overcurrent setting value (negative side overcurrent setting value Iocn), from the corrected sensor characteristic 55, which is the first characteristic data, within a negative side settable range (threshold settable range 39b). Note that the control unit 10 may calculate the first overcurrent threshold V1, which is the positive side overcurrent threshold voltage (positive side overcurrent threshold Vthp), and the second overcurrent threshold V2, which is the negative side overcurrent threshold voltage (negative side overcurrent threshold Vthn), using voltage correction amounts 86a and 86b stored in advance. In this case, the control unit 10 calculates a first overcurrent threshold V1, which is a positive-side overcurrent threshold voltage (positive-side overcurrent threshold Vthp) for a positive-side overcurrent setting value (positive-side overcurrent setting value Iocp) within a positive-side settable range (threshold settable range 39a), and calculates a second overcurrent threshold V2, which is a negative-side overcurrent threshold voltage (negative-side overcurrent threshold Vthn) for a negative-side overcurrent setting value (negative-side overcurrent setting value Iocn) within a negative-side settable range (threshold settable range 39b), using voltage correction amounts 86a and 86b calculated and stored in advance based on the corrected sensor characteristic 55. The first overcurrent threshold V1 is obtained by adding the voltage correction amount 86a to the positive-side overcurrent threshold Vth0p, and the second overcurrent threshold V2 is obtained by subtracting the voltage correction amount 86b from the negative-side overcurrent threshold Vth0n.

[0095] Thereafter, the control unit 10 calculates a first voltage correction amount ΔV1 which is a voltage correction amount for the first overcurrent threshold V1 obtained by calculation, and a second voltage correction amount ΔV2 which is a voltage correction amount for the second overcurrent threshold V2 obtained by calculation. When generating the correction command signal sc, in the case of condition A where a first limit condition in which the first overcurrent threshold V1 is a limit value (lower limit positive overcurrent threshold Vthpmin) of a positive settable range (threshold settable range 39a) or a second limit condition in which the second overcurrent threshold V2 is a limit value (upper limit negative overcurrent threshold Vthnmax) of a negative settable range (threshold settable range 39b) is satisfied, the control unit 10 determines the value of the duty ratio Du of the pulse signal Vpi which is the correction command signal sc to be a selected duty ratio value ds as follows. If only one of the first limit condition and the second limit condition is satisfied, the duty ratio value (duty ratio value d4) derived based on the limit value (lower limit positive overcurrent threshold Vthpmin) and one of the first threshold data (positive overcurrent threshold characteristic 94b) and the second threshold data (negative overcurrent threshold characteristic 95b) corresponding to the limit value (lower limit positive overcurrent threshold Vthpmin) is determined as the selected duty ratio value ds. If the first limit condition and the second limit condition are satisfied, the limit value corresponding to the smaller correction amount out of the first voltage correction amount ΔV1 and the second voltage correction amount ΔV2 is set as the selected limit value, and the duty ratio value derived based on the selected limit value and one of the first threshold data (positive overcurrent threshold characteristic 94b) and the second threshold data (negative overcurrent threshold characteristic 95b) corresponding to the selected limit value is determined as the selected duty ratio value ds.

[0096] The example shown in FIG. 29 shows the case of condition A where the first limit condition is satisfied. When the value of the duty ratio Du becomes smaller than the duty ratio value d4, the positive side overcurrent threshold Vthp becomes lower than the lower limit positive side overcurrent threshold Vthpmin, which is the positive side limit value. In this case, even if the power conversion unit 110 of the power conversion device 100 is operating normally, the overcurrent protection circuit 41 may determine that an overcurrent has flowed through the power semiconductor elements 3a to 3f and turn off the determined power semiconductor elements 3a to 3f. In order to satisfy the desired function of the power conversion device 100, the limit value of the overcurrent threshold is not reduced more than necessary. That is, the lower limit positive side overcurrent threshold Vthpmin, which is the positive side limit value, is not lowered more than necessary, and the upper limit negative side overcurrent threshold Vthnmax, which is the negative side limit value, is not raised more than necessary. In a normal power conversion device (a power conversion device of the comparative example), a large margin is required due to variation in the output characteristics of the current sensors 21a to 21c. However, in the power conversion device 100 of embodiment 2, the positive side overcurrent threshold Vthp and the negative side overcurrent threshold Vthn can be corrected, so that a smaller margin can be provided than in the power conversion device of the comparative example.

[0097] 29, the value of duty ratio Du is selected as duty ratio value d4, and thus the negative overcurrent threshold Vthan that is set becomes the negative overcurrent threshold indicated by dashed line 121 where negative overcurrent threshold characteristic 95b intersects with duty ratio value lower limit line 34. The negative overcurrent threshold Vthan that is set becomes a value smaller than upper limit negative overcurrent threshold Vthnmax, which is the limit value, as indicated by arrow 122, and the overcurrent detected during overcurrent protection operation increases slightly, but this is an improvement over the default setting value of negative overcurrent threshold Vth0n, and therefore the power conversion device 100 of the second embodiment can suppress the surge voltage during overcurrent protection operation to some extent.

[0098] FIG. 29 shows the case of condition A where the first limit condition is satisfied. Next, an example will be described in which the control unit 10 adjusts the value of the duty ratio Du according to the smaller voltage correction amount. FIG. 30 shows the case of condition B where the first voltage correction amount ΔV1 and the second voltage correction amount ΔV2 are different from each other other than condition A, and FIG. 31 shows the case of condition C where the first voltage correction amount ΔV1 and the second voltage correction amount ΔV2 are the same from each other other than condition A and condition B. Although the first voltage correction amount ΔV1 and the second voltage correction amount ΔV2 may be different from each other even in condition A, condition A is a case where the first voltage correction amount ΔV1 and the second voltage correction amount ΔV2 are at the limit values. An example will be described in which condition B except condition A is excluded using FIG. 30. In FIG. 30, the first voltage correction amount ΔV1 of the first overcurrent threshold V1 obtained by calculation is smaller than the second voltage correction amount ΔV2 of the second overcurrent threshold V2 obtained by calculation. The value of the duty ratio Du of the first threshold data (positive side overcurrent threshold characteristic 94b) which becomes the first overcurrent threshold V1 is a duty ratio value d6. The value of the duty ratio Du of the second threshold data (negative side overcurrent threshold characteristic 95b) which becomes the second overcurrent threshold V2 is a duty ratio value d7. In the case of a condition B other than the condition A in which the first voltage correction amount ΔV1 and the second voltage correction amount ΔV2 are different, the control unit 10 sets the smaller correction amount (the first voltage correction amount ΔV1 in FIG. 30) as the selected voltage correction amount ΔVs, and determines the value of the duty ratio Du (duty ratio value d6 in FIG. 30) derived based on the selected voltage correction amount ΔVs and one of the first threshold data (positive side overcurrent threshold characteristic 94b) and the second threshold data (negative side overcurrent threshold characteristic 95b) corresponding to the selected voltage correction amount ΔVs (positive side overcurrent threshold characteristic 94b in FIG. 30).

[0099] An example of the case of condition C excluding conditions A and B will be described with reference to FIG. 31. In FIG. 31, the first voltage correction amount ΔV1 of the first overcurrent threshold V1 obtained by calculation is the same as the second voltage correction amount ΔV2 of the second overcurrent threshold V2 obtained by calculation. The value of the duty ratio Du of the first threshold data (positive side overcurrent threshold characteristic 94b) which becomes the first overcurrent threshold V1 is the first duty ratio value da1. The value of the duty ratio Du of the second threshold data (negative side overcurrent threshold characteristic 95b) which becomes the second overcurrent threshold V2 is the second duty ratio value da2. The voltage correction amount calculated from the voltage value V2a of the second threshold data (negative side overcurrent threshold characteristic 95b) for the first duty ratio value da1 is the third voltage correction amount ΔV3. The voltage correction amount calculated from the voltage value V1a of the first threshold data (positive side overcurrent threshold characteristic 94b) for the second duty ratio value da2 is the fourth voltage correction amount ΔV4. 31, when changing from the first duty ratio value da1 to the second duty ratio value da2, the positive overcurrent threshold Vthap changes from the first overcurrent threshold V1 to a voltage value V1a, and the voltage correction amount increases from the first voltage correction amount ΔV1 to the fourth voltage correction amount ΔV4. When changing from the second duty ratio value da2 to the first duty ratio value da1, the negative overcurrent threshold Vthan changes from the second overcurrent threshold V2 to a voltage value V2a, and the voltage correction amount decreases from the second voltage correction amount ΔV2 to the third voltage correction amount ΔV3. In this case, the control unit 10 determines the first duty ratio value da1, which is the duty ratio value for which the correction amount is decreasing, as the selected duty ratio value ds, and generates a pulse signal Vpi having the determined selected duty ratio value ds as the correction command signal sc.

[0100] In the case of condition C excluding conditions A and B, the control unit 10 determines the selected duty ratio value ds as follows. In the case of condition C other than conditions A and B, in which the first voltage correction amount ΔV1 and the second voltage correction amount ΔV2 are the same, the control unit 10 compares a first duty ratio value da1, which is the value of the duty ratio Du derived based on the first voltage correction amount ΔV1 and the first threshold data (positive-side overcurrent threshold characteristic 94b), with a second duty ratio value da2, which is the value of the duty ratio Du derived based on the second voltage correction amount ΔV2 and the second threshold data (negative-side overcurrent threshold characteristic 95b). If the first duty ratio value da1 and the second duty ratio value da2 are the same, the control unit 10 determines the duty ratio Du of that value as the selected duty ratio value ds. If the first duty ratio value da1 and the second duty ratio value da2 are different, the control unit 10 compares a third voltage correction amount ΔV3, which is a voltage correction amount calculated from the voltage value V2a of the second threshold data (negative side overcurrent threshold characteristic 95b) for the first duty ratio value da1, with a fourth voltage correction amount ΔV4, which is a voltage correction amount calculated from the voltage value V1a of the first threshold data (positive side overcurrent threshold characteristic 94b) for the second duty ratio value da2, and determines the duty ratio value resulting in a smaller correction amount (the first duty ratio value da1 in FIG. 31) as the selected duty ratio value ds.

[0101] Even in the case of condition C, the value of the duty ratio Du with the smaller correction amount is finally used. In the overcurrent protection circuit 41 in the power conversion device 100 of the second embodiment, when the first voltage correction amount ΔV1, which is the calculated positive side correction amount, and the second voltage correction amount ΔV2, which is the calculated negative side correction amount, are different, the value of the duty ratio Du with the smaller correction amount is used. Also, when the first voltage correction amount ΔV1 and the second voltage correction amount ΔV2 are at their limit values, the value of the duty ratio Du of the limit value correction amount is used. As a result, in the case of the examples of Figs. 29 to 31, the values ​​of the duty ratio Du are selected as the duty ratio values ​​d4, d6, and da1, respectively, and therefore, although the negative side overcurrent threshold Vthan to be set increases the overcurrent detected during the overcurrent protection operation to some extent, it is improved from the negative side overcurrent threshold Vth0n of the default setting value, so that the power conversion device 100 of the second embodiment can suppress the surge voltage during the overcurrent protection operation to some extent. Of course, depending on the variation of the current sensors 21a to 21c, it is necessary to select the optimal one from the examples of Fig. 28 to Fig. 31. In the example of Fig. 29, when the value of the duty ratio Du is changed to a smaller value, the positive side overcurrent threshold Vthap reaches the limit value earlier than the negative side overcurrent threshold Vthan.

[0102] Embodiment 3 FIG. 32 is a diagram showing a configuration of a drive circuit according to the third embodiment, and FIG. 33 is a diagram showing a configuration of the protection circuit of FIG. 32. FIGS. 34, 35, 36, 37, 38, and 39 are diagrams showing a first example, a second example, a third example, a fourth example, a fifth example, and a sixth example of the overcurrent threshold characteristic of the protection circuit of FIG. 33, respectively. In the second embodiment, an example of the power conversion device 100 in which the protection circuit 59 of the overcurrent protection circuit 41 generates the adjustment source voltages Vsp and Vsn based on the correction command signal sc is described. In the third embodiment, an example is described in which the voltage values ​​corresponding to the adjustment source voltages Vsp and Vsn of the second embodiment are input to the protection circuit 59 of the overcurrent protection circuit 41 as the correction command signal sc of an analog signal. The power conversion device 100 of the third embodiment differs from the power conversion device 100 of the second embodiment in that a positive side overcurrent threshold Vthp and a negative side overcurrent threshold Vthn are output from one threshold output unit 61 to two comparators 42p, 42n, respectively, based on a correction command signal sc, which is an analog signal output from a control unit 10. The following mainly describes the parts that differ from the power conversion device 100 of the second embodiment.

[0103] The components of the power conversion device 100 of the third embodiment are the same as those of the power conversion device 100 of the first embodiment shown in Figs. 1 and 14. However, the configuration of the protection circuit 59 is different from that of the protection circuit 59 of the first and second embodiments. The control unit 10 of the third embodiment has six output terminals 45a to 45f. The control unit 10 outputs analog correction command signals vsup and vsun from the output terminals 45a and 45b to a U-phase protection circuit 59u, outputs analog correction command signals vsvp and vsvn from the output terminals 45c and 45d to a V-phase protection circuit 59v, and outputs analog correction command signals vswp and vswn from the output terminals 45e and 45f to a W-phase protection circuit 59w. The protection circuits 59u, 59v, and 59w have two input terminals to which the correction command signal sc is input, similarly to the protection circuits 59u, 59v, and 59w of the first embodiment, that is, two input terminals 46p and 46n. As described above, the signs of the correction command signals are generally sc. When the correction command signals are to be distinguished, the signs of the correction command signals are vsup, vsun, vsvp, vsvn, vswp, and vswn. When the U-phase, V-phase, and W-phase are not to be distinguished, the positive side correction command signal of the analog correction command signal sc is the correction command signal vsp, and the negative side correction command signal of the analog correction command signal sc is the correction command signal vsn.

[0104] The protection circuit 59u, the protection circuit 59v, and the protection circuit 59w have the configuration shown in FIG. 33. The protection circuit 59u, the protection circuit 59v, and the protection circuit 59w of the third embodiment are different from the protection circuit 59u, the protection circuit 59v, and the protection circuit 59w of the second embodiment in that they do not have the smoothing circuits 65a, 65b, 65, and 66, and a positive correction command signal vsp of the correction command signal sc of an analog signal is input from the input terminal 46p, and a negative correction command signal vsn of the correction command signal sc of an analog signal is input from the input terminal 46n. The correction command signal vsp corresponds to the adjustment source voltage Vsp of the second embodiment, and the correction command signal vsn corresponds to the adjustment source voltage Vsn of the second embodiment. The threshold voltage adjustment unit 60 of the third embodiment outputs the adjustment source voltage Vsp from the output terminal 43p as a positive side adjustment voltage Vap via a resistor R1, and outputs the adjustment source voltage Vsn from the output terminal 43n as a negative side adjustment voltage Van via a resistor R2. The overcurrent stop signal output unit 62 of the third embodiment is the same as the overcurrent stop signal output unit 62 of the second embodiment.

[0105] 34 to 39 show first to sixth examples of the overcurrent threshold characteristic of the protection circuit 59, respectively. The first to third examples of the overcurrent threshold characteristic correspond to the first to third examples of the overcurrent threshold characteristic in the first protection circuit 59 of the second embodiment. The fourth and fifth examples of the overcurrent threshold characteristic correspond to the first to third examples of the overcurrent threshold characteristic in the second protection circuit 59 of the second embodiment. In FIGS. 34 to 38, the horizontal axis represents the voltage of the correction command signal sc to be input, and the vertical axis represents the voltage of the overcurrent threshold. In FIGS. 34 to 39, an example is shown in which the maximum voltage value Vsa is 5.0 V. In FIGS. 34 to 36, the overcurrent threshold characteristic is shown in a case where the offset variation of the current sensors 21a to 21c is dominant, and the resistors R1 and R2 of the threshold voltage adjustment unit 60 and the resistors R3, R4, and R5 of the threshold output unit 61 have different magnitudes. 37 to 39 show overcurrent threshold characteristics when the gain variation of the current sensors 21a to 21c is dominant, and the resistances R1 and R2 of the threshold voltage adjusting unit 60 and the resistances R3, R4, and R5 of the threshold output unit 61 are different in magnitude. In FIGS. 34 and 37, R1=R2 and R1, R2>>R3, R4, and R5 (first resistance condition). In FIGS. 35 and 38, R1=R2 and R1, R2≈R3, R4, and R5 (second resistance condition). In FIGS. 36 and 39, R1>>R3, R4, and R5 and R2≈R3, R4, and R5 (third resistance condition).

[0106] The relationship between the positive side overcurrent threshold Vthp and the adjustment source voltage Vsp is shown as positive side overcurrent threshold characteristics 96a, 96b, 96c, 96d, 96e, and 96f. The relationship between the negative side overcurrent threshold Vthn and the adjustment source voltage Vsn is shown as negative side overcurrent threshold characteristics 97a, 97b, 97c, 97d, 97e, and 97f. The adjustment source voltage Vsn in Figures 37 to 39 is a voltage obtained by subtracting the adjustment source voltage Vsp from the maximum voltage value Vsa.

[0107] The power conversion device 100 of the third embodiment can reduce the overcurrent flowing through the power semiconductor elements 3a to 3f during overcurrent protection operation of the power semiconductor elements 3a to 3f, similar to the power conversion devices 100 of the first and second embodiments. Moreover, in the power conversion device 100 of the third embodiment, the protection circuit 59 of the overcurrent protection circuit 41 does not include the smoothing circuits 65a, 65b, 65, and 66, so that the overcurrent protection circuit 41 can be made smaller than that of the power conversion device 100 of the second embodiment.

[0108] The correction command signal sc of an analog signal can also be applied to the power conversion device 100 of the first embodiment. In this case, the threshold voltage adjustment unit 60 of the first embodiment shown in FIG. 5 receives a positive correction command signal of the correction command signal sc of an analog signal from an input terminal 49p and a negative correction command signal of the correction command signal sc of an analog signal from an input terminal 49n, similar to the threshold voltage adjustment unit 60 of the third embodiment. The positive correction command signal corresponds to the adjustment source voltage Vsp of the second embodiment, and the negative correction command signal corresponds to the adjustment source voltage Vsn of the second embodiment. The adjustment source voltage Vsp is output from the output terminal 43p as a positive side adjustment voltage Vap via a resistor R1, and the adjustment source voltage Vsn is output from the output terminal 43n as a negative side adjustment voltage Van via a resistor R2.

[0109] Embodiment 4 FIG. 40 is a diagram showing the configuration of a first drive circuit according to the fourth embodiment, and FIG. 41 is a diagram showing the configuration of the overcurrent protection circuit of FIG. 40. FIG. 42 is a diagram showing the configuration of a second drive circuit according to the fourth embodiment, and FIG. 43 is a diagram showing the configuration of the overcurrent protection circuit of FIG. 42. FIG. 44 is a diagram showing an example of correction of the overcurrent threshold of the overcurrent protection circuit of FIG. 43, and FIG. 45 is a diagram showing an example of correction of the overcurrent threshold of the overcurrent protection circuit of FIG. 41. The power conversion device 100 of the second embodiment has been described as an example in which the control unit 10 outputs a correction command signal sc for each phase of the three-phase AC, that is, three correction command signals scu, scv, and scw. The power conversion device 100 of the fourth embodiment is an example in which the number of correction command signals sc of the control unit 10 is reduced compared to the power conversion device 100 of the second embodiment. The power conversion device 100 of the fourth embodiment differs from the power conversion device 100 of the second embodiment in that the overcurrent protection circuit 41 includes six comparators 42a to 42f corresponding to the positive and negative sides of each phase, one threshold output unit 61, and one threshold voltage adjustment unit 60. The differences from the power conversion device 100 of the second embodiment will be mainly described.

[0110] The components of the power conversion device 100 of the fourth embodiment are the same as those of the power conversion device 100 of the first embodiment shown in FIG. 1 and FIG. 14. However, the first drive circuit 14 shows a case where the number of correction command signals sc output from the control unit 10 is one, and the second drive circuit 14 shows a case where the number of correction command signals sc output from the control unit 10 is two. The control unit 10 and the first drive circuit 14 shown in FIG. 40 are an example in which the control unit 10 outputs one correction command signal sc to the first drive circuit 14 from one output terminal 26. The control unit 10 and the second drive circuit 14 shown in FIG. 42 are an example in which the control unit 10 outputs correction command signals scp and scn to the first drive circuit 14 from two output terminals 26a and 26b, respectively. The power conversion device 100 of the fourth embodiment has the same effects as the power conversion devices 100 of the first and second embodiments, and can reduce power consumption due to the reduction in the number of output terminals of the control unit 10, and can also reduce the cost of the control unit 10.

[0111] The overcurrent protection circuit 41 of the first drive circuit 14 includes input terminals 48a, 48b, 48c to which the detection voltages Viu, Viv, Viw of the current sensors 21a to 21c of the respective phases are input, an input terminal 27 to which a correction command signal sc is input, and output terminals 47a to 47f to which six overcurrent stop signals st are output. The output terminals 47a, 47b output the overcurrent stop signals stup, stun of the U phase, the output terminals 47c, 47d output the overcurrent stop signals stvp, stvn of the V phase, and the output terminals 47e, 47f output the overcurrent stop signals stwp, stwn of the W phase. The overcurrent protection circuit 41 of the second drive circuit 14 includes input terminals 48a, 48b, 48c to which the detection voltages Viu, Viv, Viw of the current sensors 21a to 21c of the respective phases are input, input terminals 27a, 27b to which the positive side correction command signal scp and the negative side correction command signal scn are input, and output terminals 47a to 47f to which six overcurrent stop signals st are output. The output terminals 47a, 47b output the overcurrent stop signals stup, stun of the U phase, the output terminals 47c, 47d output the overcurrent stop signals stvp, stvn of the V phase, and the output terminals 47e, 47f output the overcurrent stop signals stwp, stwn of the W phase.

[0112] As shown in FIG. 41, the configuration of the first drive circuit 14 is the same as that of the threshold voltage adjustment unit 60 in the second protection circuit 59 shown in FIG. 18, and the overcurrent stop signal output unit 62 includes six comparators 42a to 42f and one threshold output unit 61. The positive overcurrent threshold Vthp output from the threshold output unit 61 is input to the positive terminals of the comparators 42a to 42f. The detection voltage Viu output from the current sensor 21a is input from the input terminal 48a to the negative terminals of the comparators 42a and 42b. The detection voltage Viv output from the current sensor 21b is input from the input terminal 48b to the negative terminals of the comparators 42c and 42d. The detection voltage Viw output from the current sensor 21c is input from the input terminal 48c to the negative terminals of the comparators 42e and 42f. Since the threshold voltage adjusting section 60 and the threshold output section 61 in the first driving circuit 14 are the same as those in the second protection circuit 59 of the second embodiment shown in FIG. 18, the description thereof will not be repeated.

[0113] As shown in Fig. 43, the second drive circuit 14 has a threshold voltage adjustment unit 60 including two smoothing circuits 65a and 65b similar to the first protection circuit 59 shown in Fig. 17, and the overcurrent stop signal output unit 62 includes six comparators 42a to 42f and two threshold output units 61a and 61b. The smoothing circuits 65a and 65b in the second drive circuit 14 of the fourth embodiment are different from the smoothing circuits 65a and 65b shown in Fig. 17 in that a positive correction command signal scp is input from the input terminal 27a and a negative correction command signal scn is input from the input terminal 27b. The correction command signal scp is a pulse signal Vpi1 having a duty ratio Du, and the correction command signal scn is a pulse signal Vpi2 having a duty ratio Du. Since the duty ratio Du of the pulse signal Vpi1 and the duty ratio Du of the pulse signal Vpi2 can be changed independently, the regulated source voltage Vsp output by the smoothing circuit 65a and the regulated source voltage Vsn output by the smoothing circuit 65b can be independent voltages. The regulated source voltage Vsp output from the output point (connection point n1) of the smoothing circuit 65a is output as a positive-side regulated voltage Vap (see FIG. 5) from the output terminal 43p via a resistor R1. The regulated source voltage Vsn output from the output point of the smoothing circuit 65b (connection point n2) is output as a negative-side regulated voltage Van (see FIG. 5) from the output terminal 43n via a resistor R2.

[0114] The threshold output unit 61a is connected to a wiring that connects the output terminal 43p of the threshold voltage adjustment unit 60 and the positive terminals of the positive side comparators 42a, 42c, and 42e of each phase, and the threshold output unit 61b is connected to a wiring that connects the output terminal 43n of the threshold voltage adjustment unit 60 and the positive terminals of the negative side comparators 42b, 42d, and 42f of each phase. The threshold output unit 61a is a series body in which a plurality of resistors Ra1 and Ra2 are connected in series between a power supply voltage Vpp generated inside the power conversion device 100 and the ground GND, and a connection point na between the resistors Ra1 and Ra2 is connected to the output terminal 43p and the positive side terminals of the positive side comparators 42a, 42c, and 42e of each phase. The threshold output unit 61b is a series body in which a plurality of resistors Ra3 and Ra4 are connected in series between a power supply voltage Vpp generated inside the power conversion device 100 and the ground GND, and a connection point nb between the resistors Ra3 and Ra4 is connected to the output terminal 43n and the positive terminals of the negative comparators 42b, 42d, and 42f. The detection voltage Viu output from the current sensor 21a is input from the input terminal 48a to the negative terminals of the comparators 42a and 42b. The detection voltage Viv output from the current sensor 21b is input from the input terminal 48b to the negative terminals of the comparators 42c and 42d. The detection voltage Viw output from the current sensor 21c is input from the input terminal 48c to the negative terminals of the comparators 42e and 42f. The ground GND is the reference voltage of the overcurrent protection circuit 41. The value of the power supply voltage Vpp is a predetermined constant value. The positive overcurrent threshold Vthp changes according to the value of the positive regulated voltage Vap output from the threshold voltage adjustment unit 60. The negative overcurrent threshold Vthn changes according to the value of the negative regulated voltage Van output from the threshold voltage adjustment unit 60.

[0115] As described above, the variations in the current sensors 21a to 21c can be corrected by one correction command signal sc or two correction command signals sc. In Fig. 41, an example including an inverter 63 is shown as a representative example of the threshold voltage adjusting unit 60, but the threshold voltage adjusting unit 60 of the first protection circuit 59 shown in Fig. 17 may also be used.

[0116] A method of correcting the positive overcurrent threshold Vthp and the negative overcurrent threshold Vthn of the overcurrent protection circuit 41 of the fourth embodiment and the operation of the power conversion device 100 of the fourth embodiment will be described with reference to Figs. 44 and 45. Figs. 44 and 45 show sensor characteristics 57a, 57b, and 57c of the current sensors 21a to 21c. In Figs. 44 and 45, the horizontal axis represents current and the vertical axis represents voltage. The sensor characteristic 57a is the sensor characteristic of the U-phase current sensor 21a, the sensor characteristic 57b is the sensor characteristic of the V-phase current sensor 21b, and the sensor characteristic 57c is the sensor characteristic of the W-phase current sensor 21c. The sensor characteristics 57a, 57b, and 57c have different voltage values ​​at which the positive overcurrent setting value Iocp and the negative overcurrent setting value Iocn are achieved. The sensor characteristics 57a, 57b, and 57c are also the corrected sensor characteristics 55 of each phase. The voltage values ​​of the reference point P1 of the sensor characteristic 57a, the reference point P2 of the sensor characteristic 57b, and the reference point P3 of the sensor characteristic 57c, which are the positive overcurrent setting value Iocp, are the threshold values ​​Vth1, Vth2, and Vth3, respectively. The voltage values ​​of the reference point P4 of the sensor characteristic 57b, the reference point P5 of the sensor characteristic 57a, and the reference point P6 of the sensor characteristic 57c, which are the negative overcurrent setting value Iocn, are the threshold values ​​Vth4, Vth5, and Vth6, respectively. The order of the reference points P1, P2, and P3 is the order in which the voltage values ​​at the positive overcurrent setting value Iocp decrease. The order of the reference points P4, P5, and P6 is the order in which the voltage values ​​at the negative overcurrent setting value Iocn decrease. The positive overcurrent threshold and the negative overcurrent threshold at the time of design are Vth0p and Vth0n, respectively. In the sensor characteristics of the current sensors 21a to 21c of each phase, if an overcurrent is determined using the positive side overcurrent threshold Vth0p and the negative side overcurrent threshold Vth0n at the time of design, the positive side overcurrent is a current that greatly exceeds the positive side overcurrent setting value Iocp, and the negative side overcurrent is a current that greatly exceeds the negative side overcurrent setting value Iocn. Therefore, in order for the positive side overcurrent to be determined using the positive side overcurrent setting value Iocp and the negative side overcurrent to be determined using the negative side overcurrent setting value Iocn, it is necessary to correct the thresholds of the current sensors 21a to 21c.

[0117] The first overcurrent protection circuit 41 of the embodiment 5 shown in FIG. 41 and the second overcurrent protection circuit 41 of the embodiment 5 shown in FIG. 43 judge the positive side overcurrent in each of the current sensors 21a to 21c by a common positive side overcurrent threshold Vthp, and judge the negative side overcurrent in each of the current sensors 21a to 21c by a common negative side overcurrent threshold Vthn. As described in the embodiment 2, for example, it is assumed that the positive side overcurrent threshold Vthap on the positive side of the overcurrent is adjusted to match the V phase or the W phase, not the U phase, which has a small correction amount. In this case, as can be seen from the sensor characteristic 57a of the U phase in FIG. 44, the voltage of the threshold Vth2 or the threshold Vth3 is reached at a current lower than the positive side overcurrent setting value Iocp in the U phase, so that the power semiconductor element 3a of the U phase may stop within the normal operating range. Similarly, it is assumed that the negative side overcurrent threshold Vthan on the negative side of the overcurrent is adjusted to match the U phase or the V phase, not the W phase, which has a small correction amount. At this time, as can be seen from the sensor characteristic 57c of the W phase in FIG. 44, the voltage of the threshold Vth5 or threshold Vth4 is reached at a current lower than the negative overcurrent setting value Iocn in the W phase, so that the power semiconductor element 3a of the U phase may stop within the normal operating range. For this reason, the sensor characteristic of the current sensor with the smallest correction amount is selected for the positive side overcurrent threshold Vthap and the negative side overcurrent threshold Vthan, which are the reference values ​​for overcurrent determination. In the example of FIG. 44, since the U phase has the highest threshold Vth1 in the positive side overcurrent setting value Iocp and the W phase has the lowest threshold Vth6 in the negative side overcurrent setting value Iocn, the positive side overcurrent threshold Vthap is corrected to the threshold Vth1, and the negative side overcurrent threshold Vthan is corrected to the threshold Vth6. In FIG. 44, the voltage correction amount of the positive side overcurrent threshold Vthp is the voltage correction amount 89a, and the voltage correction amount of the negative side overcurrent threshold Vthn is the voltage correction amount 89c. In FIG. 45, the voltage correction amount for the positive overcurrent threshold Vthp is a voltage correction amount 89a, and the voltage correction amount for the negative overcurrent threshold Vthn is a voltage correction amount 89b.

[0118] Fig. 44 corresponds to the correction method in the second overcurrent protection circuit 41 in Fig. 43, and Fig. 45 corresponds to the correction method in the first overcurrent protection circuit 41 in Fig. 41. The difference between Fig. 44 and Fig. 45 is whether the positive side overcurrent threshold Vthp and the negative side overcurrent threshold Vthn are independently adjustable or whether the positive side overcurrent threshold Vthp and the negative side overcurrent threshold Vthn are related to each other, and therefore the voltage correction amount of the positive side overcurrent threshold Vthp and the voltage correction amount of the negative side overcurrent threshold Vthn are different. Fig. 44 shows an example in which the positive side overcurrent threshold Vthp and the negative side overcurrent threshold Vthn are independently adjustable, and therefore the magnitude of the voltage correction amount 89a of the positive side overcurrent threshold Vthp and the magnitude of the voltage correction amount 89c of the negative side overcurrent threshold Vthn are different. In Fig. 45, since the positive side overcurrent threshold Vthp and the negative side overcurrent threshold Vthn are related to each other, an example is shown in which the magnitude of the voltage correction amount 89a of the positive side overcurrent threshold Vthp is the same as the magnitude of the voltage correction amount 89c of the negative side overcurrent threshold Vthn. Note that in Fig. 45, the positive side threshold settable range 39a, the negative side threshold settable range 39b, the lower limit positive side overcurrent threshold Vthpmin, and the upper limit negative side overcurrent threshold Vthnmax are omitted.

[0119] In the power conversion device 100 equipped with the first overcurrent protection circuit 41 of the embodiment 5 shown in Fig. 41, in the case of the sensor characteristics 57a, 57b, and 57c shown in Fig. 44 and Fig. 45, the value of the duty ratio Du of the pulse signal Vpi, which is the correction command signal sc, is adjusted according to the smaller correction amount of the positive side correction amount and the negative side correction amount, or according to the correction amount of the limit value, in the same manner as in the second correction example of the embodiment 2. When applying the method of the second correction example of the embodiment 2, the symbols used in Figs. 29 to 31 are used.

[0120] A generating operation of the correction command signal sc of the power conversion device 100 including the first overcurrent protection circuit 41 of the fifth embodiment shown in Fig. 41 will be described. The control unit 10 stores the following voltage correction amount data. This voltage correction amount data is first characteristic data (sensor characteristics 57a, 57b, 57c) of the output voltage with respect to the current detected by the current sensors 21a to 21c for each phase, which is actually measured in advance, first threshold data (positive side overcurrent threshold characteristic 94b) of the positive side overcurrent threshold voltage (positive side overcurrent threshold Vthap) with respect to the duty ratio Du at the positive side overcurrent setting value (positive side overcurrent setting value Iocp), and second threshold data (negative side overcurrent threshold characteristic 95b) of the negative side overcurrent threshold voltage (negative side overcurrent threshold Vthan) with respect to the duty ratio Du at the negative side overcurrent setting value (negative side overcurrent setting value Iocn).

[0121] The control unit 10 calculates a first overcurrent threshold V1, which is a positive-side overcurrent threshold voltage (positive-side overcurrent threshold Vthp) for a positive-side overcurrent setting value (positive-side overcurrent setting value Iocp) for each phase, from the first characteristic data (sensor characteristics 57a, 57b, 57c) within a positive-side settable range (threshold setting range 39a), and calculates a second overcurrent threshold V2, which is a negative-side overcurrent threshold voltage (negative-side overcurrent threshold Vthn) for a negative-side overcurrent setting value (negative-side overcurrent setting value Iocn) for each phase, from the first characteristic data (sensor characteristics 57a, 57b, 57c) within a negative-side settable range (threshold setting range 39b). The first overcurrent threshold V1 is obtained by adding a voltage correction amount 86a to the positive-side overcurrent threshold Vth0p, and the second overcurrent threshold V2 is obtained by subtracting a voltage correction amount 86b from the negative-side overcurrent threshold Vth0n.

[0122] Thereafter, the control unit 10 calculates a first voltage correction amount ΔV1 which is a voltage correction amount for the first overcurrent threshold V1 obtained by calculation, and a second voltage correction amount ΔV2 which is a voltage correction amount for the second overcurrent threshold V2 obtained by calculation. When generating the correction command signal sc, in the case of condition A where the three (U phase, V phase, W phase) first overcurrent thresholds V1 include a limit value (lower limit positive overcurrent threshold Vthpmin) of a positive side settable range (threshold settable range 39a) or the three (U phase, V phase, W phase) second overcurrent thresholds V2 include a limit value (upper limit negative overcurrent threshold Vthnmax) of a negative side settable range (threshold settable range 39b), the control unit 10 determines the value of the duty ratio Du of the pulse signal Vpi which is the correction command signal sc to be the selected duty ratio value ds as follows.

[0123] If one of the three (U phase, V phase, W phase) first overcurrent thresholds V1 and the three (U phase, V phase, W phase) second overcurrent thresholds V2 is a limit value, the value of the duty ratio Du derived based on the limit value and one of the first threshold data (positive side overcurrent threshold characteristic 94b) and the second threshold data (negative side overcurrent threshold characteristic 95b) corresponding to the limit value is determined as the selected duty ratio value ds. Furthermore, if two or more of the three (U phase, V phase, W phase) first overcurrent thresholds V1 and the three (U phase, V phase, W phase) second overcurrent thresholds V2 are at the limit values, the limit value corresponding to the smallest of the first voltage correction amount ΔV1 or second voltage correction amount ΔV2 corresponding to the candidate limit values ​​is set as the selected limit value, and the value of the duty ratio Du derived based on the selected limit value and one of the first threshold data (positive side overcurrent threshold characteristic 94b) and the second threshold data (negative side overcurrent threshold characteristic 95b) corresponding to the selected limit value is determined as the selected duty ratio value ds.

[0124] In the case of a condition B other than the condition A, in which the first voltage correction amount ΔV1 of the three (U phase, V phase, W phase) and the second voltage correction amount ΔV2 of the three (U phase, V phase, W phase) are not the same, the control unit 10 sets the smallest correction amount (the first voltage correction amount ΔV1 in FIG. 30) as the selected voltage correction amount ΔVs, and determines the value of the duty ratio Du derived based on the selected voltage correction amount ΔVs and one (positive side overcurrent threshold characteristic 94b in FIG. 30) of the first threshold data (positive side overcurrent threshold characteristic 94b) and the second threshold data (negative side overcurrent threshold characteristic 95b) corresponding to the selected voltage correction amount ΔVs as the selected duty ratio value ds.

[0125] In the case of condition C, other than condition A and condition B, in which the first voltage correction amount ΔV1 of the three (U phase, V phase, W phase) and the second voltage correction amount ΔV2 of the three (U phase, V phase, W phase) are the same, the control unit 10 compares a first duty ratio value da1, which is the value of the duty ratio Du derived based on the first voltage correction amount ΔV1 and the first threshold data (positive side overcurrent threshold characteristic 94b), with a second duty ratio value da2, which is the value of the duty ratio Du derived based on the second voltage correction amount ΔV2 and the second threshold data (negative side overcurrent threshold characteristic 95b). If the first duty ratio value da1 and the second duty ratio value da2 are the same, the control unit 10 determines the duty ratio Du of the corresponding value as the selected duty ratio value ds. If the first duty ratio value da1 and the second duty ratio value da2 are different, the control unit 10 compares a third voltage correction amount ΔV3, which is a voltage correction amount calculated from the voltage value V2a of the second threshold data (negative overcurrent threshold characteristic 95b) for the first duty ratio value da1, with a fourth voltage correction amount ΔV4, which is a voltage correction amount calculated from the voltage value of the first threshold data (positive overcurrent threshold characteristic 94b) for the second duty ratio value da2, and determines the duty ratio value with the smaller correction amount (the first duty ratio value da1 in FIG. 31) as the selected duty ratio value ds. The control unit 10 generates a pulse signal Vpi having the determined selected duty ratio value ds as a correction command signal sc.

[0126] A generating operation of the correction command signal sc, i.e., the positive side correction command signal scp and the negative side correction command signal scn, of the power conversion device 100 including the second overcurrent protection circuit 41 of the fifth embodiment shown in FIG. 43 will be described. The control unit 10 stores the following voltage correction amount data. This voltage correction amount data is first characteristic data (sensor characteristics 57a, 57b, 57c) of the output voltage with respect to the current detected by the current sensors 21a to 21c for each phase, which is actually measured in advance, first threshold data (positive side overcurrent threshold characteristic 94b) of the positive side overcurrent threshold voltage (positive side overcurrent threshold Vthap) with respect to the duty ratio Du at the positive side overcurrent setting value (positive side overcurrent setting value Iocp), and second threshold data (negative side overcurrent threshold characteristic 95b) of the negative side overcurrent threshold voltage (negative side overcurrent threshold Vthan) with respect to the duty ratio Du at the negative side overcurrent setting value (negative side overcurrent setting value Iocn). The duty ratio Du of the positive-side correction command signal scp and the duty ratio Du of the negative-side correction command signal scn can be changed independently. The positive-side overcurrent thresholds Vthp of the U-phase, V-phase, and W-phase are set to the same value by the positive-side correction command signal scp, so the first threshold data has one positive-side overcurrent threshold characteristic 94b common to the U-phase, V-phase, and W-phase. Similarly, the negative-side overcurrent thresholds Vthn of the U-phase, V-phase, and W-phase are set to the same value by the negative-side correction command signal scn, so the second threshold data has one negative-side overcurrent threshold characteristic 95b common to the U-phase, V-phase, and W-phase.

[0127] The control unit 10 calculates a first overcurrent threshold V1, which is a positive-side overcurrent threshold voltage (positive-side overcurrent threshold Vthp) for a positive-side overcurrent setting value (positive-side overcurrent setting value Iocp) for each phase, from the first characteristic data (sensor characteristics 57a, 57b, 57c) within a positive-side settable range (threshold setting range 39a), and calculates a second overcurrent threshold V2, which is a negative-side overcurrent threshold voltage (negative-side overcurrent threshold Vthn) for a negative-side overcurrent setting value (negative-side overcurrent setting value Iocn) for each phase, from the first characteristic data (sensor characteristics 57a, 57b, 57c) within a negative-side settable range (threshold setting range 39b). The first overcurrent threshold V1 is obtained by adding a voltage correction amount 86a to the positive-side overcurrent threshold Vth0p, but if it exceeds the limit value of the positive-side settable range (threshold setting range 39a), it is set to a lower limit positive-side overcurrent threshold Vthpmin. Similarly, on the negative side, the second overcurrent threshold V2 is obtained by subtracting the voltage correction amount 86b from the negative overcurrent threshold Vth0n, but if it exceeds the limit value of the negative settable range (threshold settable range 39b), it is set to the upper limit negative overcurrent threshold Vthnmax.

[0128] In the example of Fig. 44, the lower limit positive side overcurrent threshold Vthpmin is between the reference point P2 and the reference point P3, and the positive side threshold settable range 39a is set between the initial positive side overcurrent threshold Vth0p and the lower limit positive side overcurrent threshold Vthpmin. In addition, the upper limit negative side overcurrent threshold Vthnmax is between the reference point P5 and the reference point P6, and the negative side threshold settable range 39b is set between the initial negative side overcurrent threshold Vth0n and the upper limit negative side overcurrent threshold Vthnmax. In the example of Fig. 44, when determining the first overcurrent threshold V1, the control unit 10 sets the first overcurrent threshold V1 of the W phase to the lower limit positive side overcurrent threshold Vthpmin because the reference point P3 of the W phase exceeds the positive side threshold settable range 39a. In addition, when determining the second overcurrent threshold V2, since the U-phase reference point P5 and the V-phase reference point P4 exceed the negative threshold settable range 39b, the control unit 10 sets the second overcurrent threshold V2 of the U-phase and the second overcurrent threshold V2 of the V-phase to the upper limit negative overcurrent threshold Vthnmax.

[0129] The control unit 10 calculates, for each phase, a first voltage correction amount ΔV1 which is a voltage correction amount for the first overcurrent threshold V1 obtained by calculation, and a second voltage correction amount ΔV2 which is a voltage correction amount for the second overcurrent threshold V2 obtained by calculation. In the example of FIG. 44, the first voltage correction amount ΔV1 and the second voltage correction amount ΔV2 are calculated as follows. For the positive side, the control unit 10 calculates the first voltage correction amount ΔV1 of the U phase as Vth0p-Vth1, the first voltage correction amount ΔV1 of the V phase as Vth0p-Vth2, and the first voltage correction amount ΔV1 of the W phase as Vth0p-Vthpmin. For the negative side, the control unit 10 calculates the second voltage correction amount ΔV2 of the U phase and the V phase as |Vth0n-Vthnmax|, and the second voltage correction amount ΔV2 of the W phase as |Vth0n-Vth6|. In addition, in FIG. 44, since the initial negative overcurrent threshold Vth0n is lower than the upper limit negative overcurrent threshold Vthnmax and the threshold Vth6, an absolute value is used in the explanation of the calculation of the second voltage correction amount ΔV2.

[0130] When generating the first correction command signal scp, which is the positive side correction command signal sc, the control unit 10 determines the smallest correction amount among the three first voltage correction amounts ΔV1 as the selected voltage correction amount ΔVs, and determines the value of the duty ratio Du derived based on the selected voltage correction amount ΔVs and the first threshold data (positive side overcurrent threshold characteristic 94b) corresponding to the selected voltage correction amount ΔVs as the first selected duty ratio value (selected duty ratio value ds). In the example of FIG. 44, the positive side selected voltage correction amount ΔVs is the first voltage correction amount ΔV1 of the U phase calculated by Vth0p-Vth1, and is the voltage correction amount 89a. The control unit 10 generates the pulse signal Vpi1 having the determined first selected duty ratio value (selected duty ratio value ds) as the first correction command signal scp.

[0131] When generating the second correction command signal scn, which is the negative correction command signal sc, the control unit 10 determines the smallest correction amount among the three second voltage correction amounts ΔV2 as the selected voltage correction amount ΔVs, and determines the value of the duty ratio Du derived based on the selected voltage correction amount ΔVs and the second threshold data (negative overcurrent threshold characteristic 95b) corresponding to the selected voltage correction amount ΔVs as the second selected duty ratio value (selected duty ratio value ds). In the example of FIG. 44, the negative selected voltage correction amount ΔVs is the second voltage correction amount ΔV2 of the W phase calculated by |Vth0n-Vth6|, and is the voltage correction amount 89c. The control unit 10 generates the pulse signal Vpi2 having the determined second selected duty ratio value (selected duty ratio value ds) as the second correction command signal scn.

[0132] Embodiment 5. FIG. 46 is a diagram showing the configuration of a first drive circuit according to the fifth embodiment, and FIG. 47 is a diagram showing the configuration of the protection circuit of FIG. 46. FIG. 48 is a diagram showing the configuration of a second drive circuit according to the fifth embodiment, and FIG. 49 is a diagram showing the configuration of the overcurrent protection circuit of FIG. 48. Even if there is variation in the current sensors 21a to 21c, the power conversion device 100 according to the first to fourth embodiments can reduce the overcurrent flowing through the power semiconductor elements 3a to 3f during the overcurrent protection operation of the power semiconductor elements 3a to 3f by correcting the overcurrent thresholds (positive side overcurrent threshold Vthp, negative side overcurrent threshold Vthn) for determining the overcurrent and bringing the current flowing during overcurrent protection closer to the design value. However, due to a malfunction of the control unit 10 caused by noise or variation in the internal circuit of the control unit 10, the correction command signal sc output from the control unit 10 may deviate from the set value, have an increased error, or become an unexpected value. In addition, due to variation in the threshold voltage adjustment unit 60, the overcurrent threshold may become a value different from the expected value, that is, a value different from the design value. At this time, if the overcurrent threshold value becomes a value different from the assumption, i.e., a value different from the design value, the effect of the power conversion device 100 of the first to fourth embodiments may be reduced. In the fifth embodiment, an example will be described in which the normal operation of the overcurrent protection circuit 41 is confirmed by detecting the voltages of the overcurrent thresholds (positive side overcurrent threshold Vthp, negative side overcurrent threshold Vthn) and the voltages of the overcurrent thresholds (positive side overcurrent threshold Vthp, negative side overcurrent threshold Vthn) can be maintained within the allowable range.

[0133] The components of the power conversion device 100 of the fifth embodiment are the same as those of the power conversion device 100 of the first embodiment shown in FIG. 1 and FIG. 14. The power conversion device 100 of the fifth embodiment is different from the power conversion devices 100 of the first to fourth embodiments in that the overcurrent protection circuit 41 includes a voltage detection circuit 70 that detects the voltage of at least one overcurrent threshold (positive side overcurrent threshold Vthp, negative side overcurrent threshold Vthn) and the control unit 10 adjusts the correction command signal sc using threshold detection voltage information Vm output from the voltage detection circuit 70. The parts different from the power conversion devices 100 of the first to fourth embodiments will be mainly described. As a representative example, an example in which the correction command signal sc is a pulse signal Vpi having a duty ratio Du will be described. Below, examples of the first drive circuit 14 and the second drive circuit 14 of the fifth embodiment will be described.

[0134] The overcurrent protection circuit 41 in the first drive circuit 14 of the fifth embodiment shown in Figures 46 and 47 includes a U-phase protection circuit 59u, a V-phase protection circuit 59v, and a W-phase protection circuit 59w, similar to the overcurrent protection circuit 41 in the second drive circuit 14 of the fifth embodiment shown in Figures 48 and 49, similar to the overcurrent protection circuit 41 in the fourth embodiment, includes six comparators 42a to 42f, one threshold output unit 61, and one threshold voltage adjustment unit 60 corresponding to the positive and negative sides of each phase.

[0135] First, the first drive circuit 14 of the fifth embodiment will be described. The first drive circuit 14 of the fifth embodiment is an example changed from the drive circuit 14 and the protection circuit 59 shown in FIG. 16 and FIG. 18. The parts different from the drive circuit 14 and the protection circuit 59 shown in FIG. 16 and FIG. 18 will be mainly described. The U-phase protection circuit 59u, the V-phase protection circuit 59v, and the W-phase protection circuit 59w include a voltage detection circuit 70 that outputs a detection voltage Vm0 that detects at least one overcurrent threshold, for example, a positive side overcurrent threshold Vthp, as threshold detection voltage information Vm. The monitor point nm to which the voltage detection circuit 70 is connected is provided on the wiring that connects the connection point n3 of the threshold output unit 61 and the positive terminal of the positive side comparator 42p. For example, the voltage detection circuit 70 is an AD converter. In this case, the voltage detection circuit 70 converts the detection voltage Vm0 of an analog signal into threshold detection voltage information Vm of a digital signal, and outputs the threshold detection voltage information Vm from the output terminal 71 of the protection circuit 59 to the control unit 10. The control unit 10 receives U-phase threshold detection voltage information Vmu from an input terminal 72a, V-phase threshold detection voltage information Vmv from an input terminal 72b, and W-phase threshold detection voltage information Vmw from an input terminal 72c. As appropriate, the symbol for the threshold detection voltage information is generally Vm, and when it is necessary to distinguish between them, Vmu, Vmv, and Vmw are used.

[0136] The control unit 10 corrects the voltage correction amount 86a so as to reduce the difference between the voltage (detection voltage Vm0) indicated by the threshold detection voltage information Vm and the overcurrent threshold voltage (positive overcurrent threshold Vthap) calculated from the voltage correction amount 86a (see FIG. 13), and adjusts the duty ratio Du of the pulse signal Vpi based on the corrected voltage correction amount 86a. The control unit 10 also adjusts the duty ratio Du of the pulse signal Vpi so as to reduce the difference between the positive overcurrent threshold voltage (positive overcurrent threshold Vthap) calculated from the first characteristic data (corrected sensor characteristic 55) (see FIG. 13) and the voltage (detection voltage Vm0) indicated by the threshold detection voltage information Vm, or to fall within a predetermined difference range. The difference range is an allowable difference range.

[0137] In the example of the overcurrent protection circuit 41 in the first drive circuit 14 of embodiment 5, an example has been shown in which the voltage detection circuit 70 detects the voltages of the positive-side overcurrent threshold Vthap of the U phase, V phase, and W phase, but the voltage detection circuit 70 may also detect the voltages of the negative-side overcurrent threshold Vthan of the U phase, V phase, and W phase.

[0138] Next, the second drive circuit 14 of the fifth embodiment will be described. The second drive circuit 14 of the fifth embodiment is an example changed from the drive circuit 14 and the overcurrent protection circuit 41 shown in FIG. 40 and FIG. 41. The parts different from the drive circuit 14 and the overcurrent protection circuit 41 shown in FIG. 40 and FIG. 41 will be mainly described. The overcurrent protection circuit 41 includes a voltage detection circuit 70 that detects, for example, at least one overcurrent threshold, a positive side overcurrent threshold Vthp, and outputs the detection voltage Vm0 as threshold detection voltage information Vm. The monitor point nm to which the voltage detection circuit 70 is connected is provided on the wiring that connects the connection point n3 of the threshold output unit 61 and the positive terminals of the positive side comparators 42a, 42c, and 42e. For example, the voltage detection circuit 70 is an AD converter. In this case, the voltage detection circuit 70 converts the detection voltage Vm0 of an analog signal into threshold detection voltage information Vm of a digital signal, and outputs the threshold detection voltage information Vm from the output terminal 71 of the overcurrent protection circuit 41 to the control unit 10. The control unit 10 receives threshold detection voltage information Vm from an input terminal 72 .

[0139] The control unit 10 corrects a voltage correction amount 89a (see FIG. 44) corresponding to a voltage (detection voltage Vm0) indicated by the threshold detection voltage information Vm and a positive overcurrent threshold voltage (positive overcurrent threshold Vthap) so as to reduce the difference, and adjusts the duty ratio Du of the pulse signal Vpi based on the corrected voltage correction amount 89a. The control unit 10 also adjusts the duty ratio Du of the pulse signal Vpi so as to reduce the difference between a positive overcurrent threshold voltage (positive overcurrent threshold Vthap) determined based on the first characteristic data (sensor characteristics 57a, 57b, 57c) of each phase and the voltage (detection voltage Vm0) indicated by the threshold detection voltage information Vm, or to fall within a predetermined difference range.

[0140] In the example of the overcurrent protection circuit 41 in the second drive circuit 14 of embodiment 5, an example has been shown in which the voltage detection circuit 70 detects the voltage of the positive-side overcurrent threshold Vthap common to the U phase, V phase, and W phase, but the voltage detection circuit 70 may also detect the voltage of the negative-side overcurrent threshold Vthan common to the U phase, V phase, and W phase.

[0141] Conventionally, when the input terminals 72, 72a to 72c for inputting the threshold detection voltage information Vm, Vmu, Vmv, and Vmw are provided in the control unit 10, in the case of an inverter circuit of a full bridge circuit, the input terminals are also provided on the positive and negative sides, so that a large number of input terminals for inputting the threshold detection voltage information Vm are required (conventional example). However, the control unit 10 of the power conversion device 100 of the second and fourth embodiments can reduce the number of output terminals for outputting the correction command signal sc, so that even if the voltage detection circuit 70 described in the power conversion device 100 of the fifth embodiment is provided, the increase in the number of wirings connecting the overcurrent protection circuit 41 and the control unit 10 can be reduced compared to the conventional example in which the number of wirings is the same as the number of input terminals for inputting the threshold detection voltage information, and it is possible to observe whether the function of the overcurrent protection circuit 41 is working normally from the threshold detection voltage information Vm while preventing the circuits of the control unit 10 and the overcurrent protection circuit 41 from becoming large and complicated. As a result, even if the overcurrent threshold deviates due to a deviation in the correction command signal sc of the control unit 10, variations in the threshold voltage adjustment unit 60, etc., the control unit 10 can adjust the duty ratio Du of the pulse signal Vpi so that the overcurrent threshold falls within a predetermined difference range based on the threshold detection voltage information Vm of the voltage detection circuit 70.

[0142] In the power conversion device 100 of the fifth embodiment, the ground GND of the overcurrent protection circuit 41 and the ground GND of the control unit 10 are common, so that an insulating amplifier is not required. Although an example in which the voltage detection circuit 70 is provided in the overcurrent protection circuit 41 has been shown, the control unit 10 may be provided with an AD converter, and the threshold detection voltage information Vm may be generated by the AD converter of the control unit 10. When the control unit 10 is provided with an AD converter, if the ground GND of the overcurrent protection circuit 41 and the ground GND of the control unit 10 are different, the ground GND of the overcurrent protection circuit 41 and the ground GND of the control unit 10 are separated by an insulating amplifier or the like to prevent noise from entering. In addition, if the analog signal line from the monitor point nm to the AD converter of the control unit 10 is long, an RC filter for noise cutting may be provided in the area of ​​the voltage detection circuit 70 shown in Figures 47 and 49.

[0143] In each embodiment, the sensor characteristics of the current sensors 21a to 21c are shown as an example in which the output voltage increases as the current value goes from negative to positive, i.e., the slope of the sensor characteristics is positive, but the present invention is not limited thereto, and the output voltage may increase as the current value goes from positive to negative, i.e., the slope of the sensor characteristics may be negative. Even in this case, the threshold voltage adjustment unit 60 of the overcurrent protection circuit 41 corrects the deviation of the overcurrent threshold value associated with the deviation of the current sensors 21a to 21c when an overcurrent occurs, thereby achieving the same effect as the power conversion device 100 of the embodiment.

[0144] 18, 41, 47, and 49 show an example in which the correction command signal sc is input to the smoothing circuit 66 that generates the negative adjustment source voltage Vsn via the inverter 63, but the present invention is not limited to this, and the correction command signal sc may be input to the smoothing circuit 65 that generates the positive adjustment source voltage Vsp via the inverter 63. In this case, the same effect can be achieved, except that the relationship between the duty ratio Du and voltage adjustment is reversed.

[0145] In recent years, silicon carbide (SiC) elements, which have the characteristics of low loss and high-speed operation, have been used as power semiconductor elements to improve the performance of power conversion devices. SiC elements have a wide band gap and a dielectric breakdown voltage that is about 10 times higher than that of Si (Silicon) elements. Therefore, when the dielectric breakdown voltage is designed to be the same, the thickness of the semiconductor layer that forms the current path can be made thinner than that of Si elements, and a very small on-resistance value during conduction can be achieved. In addition, when compared at the same dielectric breakdown voltage, the depletion layer width of SiC elements is about 1 / 10 that of Si elements, and the shortened carrier travel length enables switching that is about 10 times faster than Si elements.

[0146] By applying SiC elements to power conversion devices used in electric powertrains, it is possible to reduce losses during vehicle operation, leading to improvements in the vehicle's electricity consumption, which is equivalent to its fuel economy. When the power conversion device is an inverter, the loss in the power semiconductor elements is directly linked to the overall loss of the inverter, so reducing the loss in power conversion devices such as inverters is essential to realizing environmentally friendly and competitive electric vehicles.

[0147] The power conversion device 100 of embodiments 1 to 5 has a greater effect than when a Si element is used, since the lower the switching loss of a device, such as a SiC element which is a semiconductor element using a wide band gap semiconductor material, the greater the effect of the difference in switching loss due to the switching speed at turn-on.

[0148] In the first to fifth embodiments, an example has been described in which the overcurrent protection circuit 41 disclosed in the present application is applied to a two-level three-phase inverter to protect the power semiconductor element from an overcurrent. However, the overcurrent protection circuit 41 of the present application is not limited to this, and can be applied to various power conversion devices. For example, the two-level power conversion device has been described, but a three-level or multi-level power conversion device may be used, and the overcurrent protection circuit 41 of the present application may be applied to a single-phase inverter when power is supplied to the motor 9 in the case of a single-phase load. Furthermore, the overcurrent protection circuit 41 of the present application can be applied to a DC / DC converter, an AC / DC converter, or the like when power is supplied to a DC load such as the motor 9 or a battery. When the power conversion device is a DC / DC converter, the current sensor is disposed on the wiring on the input side or output side of the power conversion unit 110.

[0149] In addition, 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 application in 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 specification. For example, this includes cases in which at least one component is modified, added, or omitted, and further cases in which at least one component is extracted and combined with components of other embodiments.

[0150] Although the preferred embodiments have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the claims.

[0151] Various aspects of the present disclosure are summarized below as appendices.

[0152] (Appendix 1) A power conversion device that controls a power conversion unit having a plurality of power semiconductor elements to convert DC power into AC power or AC power into DC power, a drive circuit that outputs an element drive signal that drives the plurality of power semiconductor elements, a control unit that controls the drive circuit, and a current sensor that detects an AC current of the power conversion unit, The drive circuit includes: an element drive circuit that outputs the element drive signal to the power semiconductor element; an overcurrent protection circuit that determines that an overcurrent has flowed through the power semiconductor element and outputs an overcurrent stop signal to the element drive circuit to output the element drive signal that switches the power semiconductor element from an on state to an off state, The overcurrent protection circuit includes: a comparator that determines that an overcurrent has flowed through the power semiconductor element by comparing a detection voltage output by the current sensor with an overcurrent threshold voltage, and generates the overcurrent stop signal; a threshold output unit that outputs the overcurrent threshold voltage; a threshold voltage adjustment unit that generates an adjustment voltage for causing the threshold output unit to output the overcurrent threshold voltage based on a correction command signal output from the control unit, and outputs the adjustment voltage to the threshold output unit, a voltage correction amount is a difference between a first voltage of a current sensor at the time of design and a second voltage of the current sensor mounted on the power semiconductor device, for a predetermined overcurrent setting value that turns off the power semiconductor device; The control unit is generating the correction command signal based on the voltage correction amount stored in advance or the voltage correction amount calculated from voltage correction amount data stored in advance; Power conversion equipment. (Appendix 2) The control unit is The voltage correction amount data includes characteristic data of an output voltage with respect to a current detected by the current sensor, the characteristic data being actually measured in advance, generating the correction command signal based on the voltage correction amount calculated from the voltage correction amount data; 2. The power conversion device of claim 1. (Appendix 3) the power conversion unit is a full bridge circuit in which the power semiconductor element of an upper arm and the power semiconductor element of a lower arm are connected in series, The overcurrent protection circuit includes: a first comparator that determines that an overcurrent has flowed through the power semiconductor element of the upper arm by comparing a detection voltage output by the current sensor with the overcurrent threshold voltage on a positive side and generates the overcurrent stop signal on a positive side; a second comparator that determines that an overcurrent has flowed through the power semiconductor element of the lower arm by comparing a detection voltage output by the current sensor with the negative overcurrent threshold voltage, and generates the negative overcurrent stop signal; the threshold output unit that outputs the positive overcurrent threshold voltage and the negative overcurrent threshold voltage; a threshold voltage adjustment unit that outputs the first adjustment voltage and the second adjustment voltage to the threshold output unit, The threshold voltage adjustment unit is generating the first regulated voltage and the second regulated voltage based on the correction command signal output from the control unit; 3. The power conversion device according to claim 1 or 2. (Appendix 4) the power conversion unit is a full bridge circuit in which the power semiconductor element of an upper arm and the power semiconductor element of a lower arm are connected in series, The overcurrent protection circuit includes: a first comparator that determines that an overcurrent has flowed through the power semiconductor element of the upper arm by comparing a detection voltage output by the current sensor with the overcurrent threshold voltage on a positive side and generates the overcurrent stop signal on a positive side; a second comparator that determines that an overcurrent has flowed through the power semiconductor element of the lower arm by comparing a detection voltage output by the current sensor with the negative overcurrent threshold voltage, and generates the negative overcurrent stop signal; A first threshold output unit that outputs the positive overcurrent threshold voltage; A second threshold output unit that outputs the negative overcurrent threshold voltage; a threshold voltage adjustment unit that outputs a first adjusted voltage to a first threshold output unit and outputs a second adjusted voltage to a second threshold output unit, the control unit outputs the first correction command signal and the second correction command signal to the overcurrent protection circuit; The threshold voltage adjustment unit is generating a first regulated voltage based on the first corrected command signal, and generating a second regulated voltage based on the second corrected command signal; 3. The power conversion device according to claim 1 or 2. (Appendix 5) The current sensor further includes a temperature sensor for detecting a temperature of the current sensor. The control unit is The temperature map includes characteristic data of an output voltage versus a current detected by the current sensor, the characteristic data being measured in advance at a plurality of temperatures, generating the correction command signal based on a total correction amount obtained by adding together the temperature correction amount extracted based on the temperature information detected by the temperature sensor and the temperature map and the voltage correction amount; 3. The power conversion device according to claim 1 or 2. (Appendix 6) The temperature correction amount is a change amount of the detection voltage output by the current sensor with respect to the overcurrent setting value with respect to a preset reference temperature. 6. The power conversion device according to claim 5. (Appendix 7) the correction command signal is a pulse signal whose duty ratio is changeable, the threshold voltage adjustment unit includes a smoothing circuit that smoothes the pulse signal or an inverted pulse signal obtained by inverting the pulse signal, and outputs an adjustment source voltage; the threshold output unit is a series circuit in which a plurality of resistors are connected in series between a power supply voltage and a ground, a connection point between the resistors in the series circuit is connected to the comparator, and an output point from which the regulated source voltage is output is connected to the connection point via a resistor. 7. The power conversion device according to claim 1, 2, 5, or 6. (Appendix 8) the power conversion unit is a full bridge circuit in which the power semiconductor element of an upper arm and the power semiconductor element of a lower arm are connected in series, The overcurrent protection circuit includes: a first comparator that determines that an overcurrent has flowed through the power semiconductor element of the upper arm by comparing a detection voltage output by the current sensor with the overcurrent threshold voltage on a positive side and generates the overcurrent stop signal on a positive side; a second comparator that determines that an overcurrent has flowed through the power semiconductor element of the lower arm by comparing a detection voltage output by the current sensor with the overcurrent threshold voltage on a negative side and generates the overcurrent stop signal on a negative side; the threshold output unit that outputs the positive overcurrent threshold voltage and the negative overcurrent threshold voltage; a threshold voltage adjustment unit that outputs the first adjustment voltage and the second adjustment voltage to the threshold output unit, The threshold voltage adjustment unit is a first smoothing circuit that smoothes the pulse signal and outputs a first regulated source voltage, and a second smoothing circuit that smoothes the pulse signal and outputs a second regulated source voltage, the threshold output unit is a series circuit in which a first resistor, a second resistor, and a third resistor are connected in series between a power supply voltage and a ground, a first connection point at which the first resistor and the second resistor on the power supply voltage side are connected is connected to the first comparator; an output point of the first smoothing circuit, from which the first regulated source voltage is output, is connected to the first connection point via a resistor; a second connection point at which the third resistor and the second resistor on the ground side are connected is connected to a second comparator; an output point of the second smoothing circuit, from which the second regulated source voltage is output, is connected to the second connection point via a resistor; 8. The power conversion apparatus of claim 7. (Appendix 9) the power conversion unit is a full bridge circuit in which the power semiconductor element of an upper arm and the power semiconductor element of a lower arm are connected in series, The overcurrent protection circuit includes: a first comparator that determines that an overcurrent has flowed through the power semiconductor element of the upper arm by comparing a detection voltage output by the current sensor with the overcurrent threshold voltage on a positive side and generates the overcurrent stop signal on a positive side; a second comparator that determines that an overcurrent has flowed through the power semiconductor element of the lower arm by comparing a detection voltage output by the current sensor with the overcurrent threshold voltage on a negative side and generates the overcurrent stop signal on a negative side; the threshold output unit that outputs the positive overcurrent threshold voltage and the negative overcurrent threshold voltage; a threshold voltage adjustment unit that outputs the first adjustment voltage and the second adjustment voltage to the threshold output unit, The threshold voltage adjustment unit is a first smoothing circuit that smoothes the pulse signal and outputs a first regulated source voltage, and a second smoothing circuit that smoothes an inverted pulse signal obtained by inverting the pulse signal by an inverter and outputs a second regulated source voltage, the threshold output unit is a series circuit in which a first resistor, a second resistor, and a third resistor are connected in series between a power supply voltage and a ground, a first connection point at which the first resistor and the second resistor on the power supply voltage side are connected is connected to the first comparator; an output point of the first smoothing circuit, from which the first regulated source voltage is output, is connected to the first connection point via a resistor; a second connection point at which the third resistor and the second resistor on the ground side are connected is connected to a second comparator; an output point of the second smoothing circuit, from which the second regulated source voltage is output, is connected to the second connection point via a resistor; 8. The power conversion apparatus of claim 7. (Appendix 10) The voltage correction amount data is a first characteristic data of an output voltage with respect to a current detected by the current sensor, which is actually measured in advance; a first threshold data of the positive side overcurrent threshold voltage with respect to the duty ratio at the positive side overcurrent setting value; and a second threshold data of the negative side overcurrent threshold voltage with respect to the duty ratio at the negative side overcurrent setting value, The control unit is A first overcurrent threshold, which is the positive side overcurrent threshold voltage for the positive side overcurrent setting value, is calculated from the first characteristic data within a positive settable range, and a second overcurrent threshold, which is the negative side overcurrent threshold voltage for the negative side overcurrent setting value, is calculated from the first characteristic data within a negative settable range; Calculating a first voltage correction amount, which is the voltage correction amount for the first overcurrent threshold obtained by calculation, and a second voltage correction amount, which is the voltage correction amount for the second overcurrent threshold obtained by calculation; When generating the correction command signal, In the case of condition A, a first limit condition in which the first overcurrent threshold is the limit value of the positive side settable range or a second limit condition in which the second overcurrent threshold is the limit value of the negative side settable range is satisfied. If only one of the first limit condition and the second limit condition is satisfied, a duty ratio value derived based on the limit value and one of the first threshold data and the second threshold data corresponding to the limit value is determined as a selected duty ratio value; If the first limit condition and the second limit condition are satisfied, a limit value corresponding to the smaller correction amount between the first voltage correction amount and the second voltage correction amount is set as a selected limit value, and a value of the duty ratio derived based on the selected limit value and one of the first threshold data and the second threshold data corresponding to the selected limit value is determined as a selected duty ratio value; In the case of a condition B other than the condition A, in which the first voltage correction amount and the second voltage correction amount are different, the smaller correction amount is determined as a selected voltage correction amount, and the value of the duty ratio derived based on the selected voltage correction amount and one of the first threshold data and the second threshold data corresponding to the selected voltage correction amount is determined as a selected duty ratio value; In the case of a condition C other than the condition A and the condition B, in which the first voltage correction amount and the second voltage correction amount are the same, a first duty ratio value which is the value of the duty ratio derived based on the first voltage correction amount and the first threshold data, and a second duty ratio value which is the value of the duty ratio derived based on the second voltage correction amount and the second threshold data, If the first duty ratio value and the second duty ratio value are the same, the duty ratio of the first duty ratio value is determined as a selected duty ratio value; If the first duty ratio value and the second duty ratio value are different, a third voltage correction amount, which is the voltage correction amount calculated from the voltage value of the second threshold data for the first duty ratio value, is compared with a fourth voltage correction amount, which is the voltage correction amount calculated from the voltage value of the first threshold data for the second duty ratio value, and the duty ratio value which has a smaller correction amount is determined as a selected duty ratio value; generating the pulse signal having the selected duty ratio value as the correction command signal; 10. The power conversion device according to claim 8 or 9. (Appendix 11) the power conversion unit is a full bridge circuit in which the power semiconductor element of an upper arm and the power semiconductor element of a lower arm are connected in series, The overcurrent protection circuit includes: a first comparator that determines that an overcurrent has flowed through the power semiconductor element of the upper arm by comparing a detection voltage output by the current sensor with the overcurrent threshold voltage on a positive side and generates the overcurrent stop signal on a positive side; a second comparator that determines that an overcurrent has flowed through the power semiconductor element of the lower arm by comparing a detection voltage output by the current sensor with the negative overcurrent threshold voltage, and generates the negative overcurrent stop signal; the threshold output unit that outputs the positive overcurrent threshold voltage and the negative overcurrent threshold voltage; a threshold voltage adjustment unit that outputs a first adjusted voltage to a first threshold output unit and outputs a second adjusted voltage to a second threshold output unit, the control unit outputs a first adjustment source voltage and a second adjustment source voltage to the overcurrent protection circuit as a first correction command signal and a second correction command signal, respectively; The threshold voltage adjustment unit is a first input resistor for adjusting the first regulated voltage to a first regulated voltage, and a second input resistor for adjusting the second regulated voltage to a second regulated voltage, the threshold output unit is a series circuit including a first resistor, a second resistor, and a third resistor connected in series between a power supply voltage and a ground, a first connection point at which the first resistor and the second resistor on the power supply voltage side are connected is connected to the first comparator; One end of the first input resistor at a side where the first regulated voltage is output is connected to the first connection point, a second connection point at which the third resistor and the second resistor on the ground side are connected is connected to a second comparator; One end of the second input resistor at a side where the second regulated voltage is output is connected to the second connection point. 7. The power conversion device according to claim 1, 2, 5, or 6. (Appendix 12) The AC power handled by the power conversion unit is three-phase AC power, the current sensors are three current sensors for detecting each phase of a three-phase AC current of the power conversion unit, The overcurrent protection circuit includes: a first comparator and a second comparator are provided for each phase of a three-phase AC current; The three first comparators receive the same positive overcurrent threshold voltage output from the threshold output unit, The three second comparators are input with the same negative overcurrent threshold voltage output from the threshold output unit. 10. The power conversion device according to claim 8 or 9. (Appendix 13) The AC power handled by the power conversion unit is three-phase AC power, the current sensors are three current sensors for detecting each phase of a three-phase AC current of the power conversion unit, the first correction command signal and the second correction command signal are pulse signals whose duty ratios are changeable, The overcurrent protection circuit includes: a first comparator and a second comparator are provided for each phase of a three-phase AC current; The three first comparators receive the same positive overcurrent threshold voltage output from the first threshold output unit, The three second comparators receive the same negative overcurrent threshold voltage output from the second threshold output unit, The threshold voltage adjustment unit is a first smoothing circuit that smoothes the pulse signal of the first correction command signal to output a first adjustment source voltage, and a second smoothing circuit that smoothes the pulse signal of the second correction command signal to output a second adjustment source voltage, The first threshold output unit is a first series circuit in which a plurality of resistors are connected in series between a power supply voltage and a ground, The second threshold output unit is a second series circuit in which a plurality of resistors are connected in series between a power supply voltage and ground, a first connection point which is a connection point between the resistors in the first series body is connected to three first comparators, and an output point at which the first regulated source voltage is output is connected to the first connection point via a resistor; a second connection point which is a connection point between the resistors in the second series body is connected to three second comparators, and an output point at which the second regulated source voltage is output is connected to the second connection point via a resistor; 5. The power conversion apparatus of claim 4. (Appendix 14) The overcurrent protection circuit includes: a voltage detection circuit that detects the positive overcurrent threshold voltage and outputs the detected voltage as threshold detection voltage information; the control unit corrects the voltage correction amount so that a difference between the voltage indicated by the threshold detection voltage information and the overcurrent threshold voltage calculated from the voltage correction amount becomes small, and adjusts a duty ratio of the pulse signal based on the corrected voltage correction amount. 10. The power conversion device according to claim 8 or 9. (Appendix 15) The overcurrent protection circuit includes: a voltage detection circuit that detects the positive overcurrent threshold voltage and outputs the detected voltage as threshold detection voltage information; the control unit adjusts a duty ratio of the pulse signal so that a difference between the positive overcurrent threshold voltage calculated from the first characteristic data and a voltage indicated by the threshold detection voltage information becomes small or falls within a predetermined difference range. 11. The power conversion apparatus of claim 10. (Appendix 16) The AC power handled by the power conversion unit is three-phase AC power, the current sensors are three current sensors for detecting each phase of a three-phase AC current of the power conversion unit, The overcurrent protection circuit includes: The control circuit includes a first comparator, a second comparator, a threshold output unit, and a threshold voltage adjustment unit for each phase of a three-phase AC current. 16. The power conversion device according to claim 14 or 15. (Appendix 17) The overcurrent protection circuit includes: a voltage detection circuit that detects the positive overcurrent threshold voltage and outputs the detected voltage as threshold detection voltage information; the control unit corrects the voltage correction amount so that a difference between the voltage indicated by the threshold detection voltage information and the voltage correction amount corresponding to the positive overcurrent threshold voltage becomes small, and adjusts a duty ratio of the pulse signal based on the corrected voltage correction amount. 14. The power conversion device according to claim 12 or 13. (Appendix 18) The overcurrent protection circuit includes: a voltage detection circuit that detects the positive overcurrent threshold voltage and outputs the detected voltage as threshold detection voltage information; The voltage correction amount data is First characteristic data of an output voltage versus a current detected by the current sensor for each phase, the first characteristic data being actually measured in advance; a first threshold data of the overcurrent threshold voltage on a positive side for the duty ratio at the overcurrent setting value on a positive side, and a second threshold data of the overcurrent threshold voltage on a negative side for the duty ratio at the overcurrent setting value on a negative side, the control unit adjusts a duty ratio of the pulse signal so that a difference between the positive overcurrent threshold voltage determined based on the first characteristic data of each phase and a voltage indicated by the threshold detection voltage information becomes small or falls within a predetermined difference range. 14. The power conversion device according to claim 12 or 13. (Appendix 19) The voltage correction amount data is a first characteristic data of an output voltage for a current detected by the current sensor for each phase, which is actually measured in advance; a first threshold data of the positive side overcurrent threshold voltage for the duty ratio at the positive side overcurrent setting value; and a second threshold data of the negative side overcurrent threshold voltage for the duty ratio at the negative side overcurrent setting value, The control unit is A first overcurrent threshold is calculated for each phase from the first characteristic data within a positive settable range, the first overcurrent threshold being the positive overcurrent threshold voltage for the positive overcurrent setting value, and a second overcurrent threshold is calculated for each phase from the first characteristic data within a negative settable range, the second overcurrent threshold being the negative overcurrent threshold voltage for the negative overcurrent setting value; Calculating, for each phase, a first voltage correction amount which is the voltage correction amount for the first overcurrent threshold obtained by calculation, and a second voltage correction amount which is the voltage correction amount for the second overcurrent threshold obtained by calculation; When generating the first correction command signal, determining a smallest correction amount among the first voltage correction amounts of each phase as a selected voltage correction amount, and determining a value of the duty ratio derived based on the selected voltage correction amount and the first threshold data corresponding to the selected voltage correction amount as a first selected duty ratio value; generating the pulse signal having the determined first selected duty ratio value as a first correction command signal; When generating the second correction command signal, determining a smallest correction amount among the second voltage correction amounts of each phase as a selected voltage correction amount, and determining a value of the duty ratio derived based on the selected voltage correction amount and the second threshold data corresponding to the selected voltage correction amount as a second selected duty ratio value; generating the pulse signal having the determined second selected duty ratio value as a second correction command signal; 14. The power conversion apparatus of claim 13. (Appendix 20) The voltage correction amount data is a first characteristic data of an output voltage for a current detected by the current sensor for each phase, which is actually measured in advance; a first threshold data of the positive side overcurrent threshold voltage for the duty ratio at the positive side overcurrent setting value; and a second threshold data of the negative side overcurrent threshold voltage for the duty ratio at the negative side overcurrent setting value, The control unit is A first overcurrent threshold is calculated for each phase from the first characteristic data within a positive settable range, the first overcurrent threshold being the positive overcurrent threshold voltage for the positive overcurrent setting value, and a second overcurrent threshold is calculated for each phase from the first characteristic data within a negative settable range, the second overcurrent threshold being the negative overcurrent threshold voltage for the negative overcurrent setting value; Calculating a first voltage correction amount, which is the voltage correction amount for the first overcurrent threshold obtained by calculation, and a second voltage correction amount, which is the voltage correction amount for the second overcurrent threshold obtained by calculation; When generating the correction command signal, In the case of condition A, the three first overcurrent thresholds include the limit value of the positive side settable range or the three second overcurrent thresholds include the limit value of the negative side settable range, If one of the three first overcurrent thresholds and the three second overcurrent thresholds is a limit value, a duty ratio value derived based on the limit value and one of the first threshold data and the second threshold data corresponding to the limit value is determined as a selected duty ratio value; If two or more of the three first overcurrent thresholds and the three second overcurrent thresholds are limit values, a limit value corresponding to the smallest of the first voltage correction amount or the second voltage correction amount corresponding to the candidate limit value is set as a selected limit value, and a value of the duty ratio derived based on the selected limit value and one of the first threshold data and the second threshold data corresponding to the selected limit value is determined as a selected duty ratio value; In the case of a condition B other than the condition A, in which the three first voltage correction amounts and the three second voltage correction amounts are not the same, the smallest correction amount is determined as a selected voltage correction amount, and the value of the duty ratio derived based on the selected voltage correction amount and one of the first threshold data and the second threshold data corresponding to the selected voltage correction amount is determined as a selected duty ratio value; In the case of a condition C other than the condition A and the condition B, in which the three first voltage correction amounts and the three second voltage correction amounts are the same, among a first duty ratio value which is the value of the duty ratio derived based on the first voltage correction amount and the first threshold data, and a second duty ratio value which is the value of the duty ratio derived based on the second voltage correction amount and the second threshold data, If the first duty ratio value and the second duty ratio value are the same, the duty ratio of the first duty ratio value is determined as a selected duty ratio value; If the first duty ratio value and the second duty ratio value are different, a third voltage correction amount, which is the voltage correction amount calculated from the voltage value of the second threshold data for the first duty ratio value, is compared with a fourth voltage correction amount, which is the voltage correction amount calculated from the voltage value of the first threshold data for the second duty ratio value, and the duty ratio value which has a smaller correction amount is determined as a selected duty ratio value; generating the pulse signal having the selected duty ratio value as the correction command signal; 13. The power conversion apparatus of claim 12. (Appendix 21) 21. The power conversion device according to any one of claims 1 to 20, wherein the power semiconductor element is a power semiconductor element using a wide band gap semiconductor material. [Explanation of symbols]

[0153] 3a, 3b, 3c, 3d, 3e, 3f...power semiconductor element, 10...control unit, 14...drive circuit, 21a, 21b, 21c...current sensor, 22...temperature sensor, 39a, 39b...threshold value settable range, 40...element drive circuit, 41...overcurrent protection circuit, 42a, 42b, 42c, 42d, 42e, 42f, 42n, 42p...comparator, 55...corrected sensor characteristics (voltage correction amount data, first characteristic data), 56a, 56b, 56c...sensor characteristics (voltage correction amount data), 57a, 57b, 57c...sensor characteristics (voltage correction amount data, first characteristic data), 59, 59u, 59v, 59w...overcurrent protection circuit, 60...threshold voltage adjustment unit, 61, 61a, 61b...threshold output unit, 63...inverter, 65...smoothing circuit (first smoothing circuit), 65a...smoothing circuit (first smoothing circuit), 65b...smoothing circuit (second smoothing circuit), 66...smoothing circuit (second smoothing circuit), 70...voltage detection circuit, 75...temperature map, 83a, 83b, 86a, 86b...voltage correction amount, 87a, 87b, 88a, 88b...temperature correction amount, 89a, 89b, 89c...voltage correction amount, 92a, 92b, 92c, 92d, 92e, 92f...positive side overcurrent threshold characteristic (voltage correction amount data), 93a, 93b, 93c, 93d, 93e, 93f...Negative overcurrent threshold characteristic (voltage correction amount data), 94a...Positive overcurrent threshold characteristic (voltage correction amount data), 94b...Positive overcurrent threshold characteristic (voltage correction amount data, first threshold data), 95a...Negative overcurrent threshold characteristic (voltage correction amount data), 95b...Negative overcurrent threshold characteristic (voltage correction amount data, second threshold data), 96a, 96b, 96c, 96d, 96e, 96f...Positive overcurrent threshold characteristic (voltage correction amount data), 97a, 97b, 97c, 97d, 97e, 97f...Negative overcurrent threshold characteristic (voltage correction amount data), 100...Power conversion device, 110...Power Conversion section, d4...duty ratio value, Du...duty ratio, da1...first duty ratio value, da2...second duty ratio value, ds...selected duty ratio value, GND...ground, Iocn...negative overcurrent setting value, Iocp...positive overcurrent setting value, Iu, Iv, Iw...AC current, n1, n2...connection point (output point), n3...connection point (first connection point), n4...connection point (second connection point), R1, R2...resistance, R3...resistance (first resistor), R4...resistance (second resistor), R5...resistance (third resistor), Ra1, Ra2, Ra3, Ra4...resistance, Ta...temperature detection value (temperature information), sc, scup,scun, scvp, scvn, scwp, scwn...correction command signal, scp, scn, scu, scv, scw...correction command signal, sd, sda, sdb, sdc, sdd, sde, sdf...element drive signal, st, stp, stn...overcurrent stop signal, stup, stun, stvp, stvn, stwp, stwn...overcurrent stop signal, V1...first overcurrent threshold, V2...second overcurrent threshold, Vi, Viu, Viv, Viw...detection voltage, Vm, Vmu, Vmv, Vmw...threshold detection voltage information, Vm0...detection voltage, Vpi...pulse signal, Vpia...pulse signal (inverted pulse signal), Vpp...power supply voltage, Vsp...adjustment source voltage, Vsn...adjustment source voltage, vsp, vsn, vsup, vsun, vsvp , vsvn, vswp, vswn...correction command signal, Vthn...negative overcurrent threshold (overcurrent threshold voltage), Vthp...positive overcurrent threshold (overcurrent threshold voltage), Vth0n...negative overcurrent threshold (overcurrent threshold voltage, first voltage), Vth0p...positive overcurrent threshold (overcurrent threshold voltage, first voltage), Vthan...negative overcurrent threshold (overcurrent threshold voltage, second voltage), Vthap...positive overcurrent threshold (overcurrent threshold voltage, second voltage), Van...negative adjustment voltage, Vap...positive adjustment voltage, Vthnmax...upper negative overcurrent threshold (limit value), Vthpmin...lower positive overcurrent threshold (limit value), ΔV1...first voltage correction amount, ΔV2...second voltage correction amount, ΔV3...third voltage correction amount, ΔV4...fourth voltage correction amount, ΔVs...selected voltage correction amount,

Claims

1. A power conversion device that controls a power conversion unit having a plurality of power semiconductor elements to convert DC power into AC power or AC power into DC power, a drive circuit that outputs an element drive signal that drives the plurality of power semiconductor elements, a control unit that controls the drive circuit, and a current sensor that detects an AC current of the power conversion unit, The drive circuit includes: an element drive circuit that outputs the element drive signal to the power semiconductor element; an overcurrent protection circuit that determines that an overcurrent has flowed through the power semiconductor element and outputs an overcurrent stop signal to the element drive circuit to output the element drive signal that switches the power semiconductor element from an on state to an off state, The overcurrent protection circuit includes: a comparator that determines that an overcurrent has flowed through the power semiconductor element by comparing a detection voltage output by the current sensor with an overcurrent threshold voltage, and generates the overcurrent stop signal; a threshold output unit that outputs the overcurrent threshold voltage; a threshold voltage adjustment unit that generates an adjustment voltage for causing the threshold output unit to output the overcurrent threshold voltage based on a correction command signal output from the control unit, and outputs the adjustment voltage to the threshold output unit, a voltage correction amount is a difference between a first voltage of a current sensor at the time of design and a second voltage of the current sensor mounted on the power semiconductor device, for a predetermined overcurrent setting value that turns off the power semiconductor device; The control unit is generating the correction command signal based on the voltage correction amount stored in advance or the voltage correction amount calculated from voltage correction amount data stored in advance; Power conversion equipment.

2. The control unit is The voltage correction amount data includes characteristic data of an output voltage with respect to a current detected by the current sensor, the characteristic data being actually measured in advance, generating the correction command signal based on the voltage correction amount calculated from the voltage correction amount data; The power converter according to claim 1 .

3. the power conversion unit is a full bridge circuit in which the power semiconductor element of an upper arm and the power semiconductor element of a lower arm are connected in series, The overcurrent protection circuit includes: a first comparator that determines that an overcurrent has flowed through the power semiconductor element of the upper arm by comparing a detection voltage output by the current sensor with the overcurrent threshold voltage on a positive side and generates the overcurrent stop signal on a positive side; a second comparator that determines that an overcurrent has flowed through the power semiconductor element of the lower arm by comparing a detection voltage output by the current sensor with the overcurrent threshold voltage on a negative side and generates the overcurrent stop signal on a negative side; the threshold output unit that outputs the positive overcurrent threshold voltage and the negative overcurrent threshold voltage; a threshold voltage adjustment unit that outputs the first adjustment voltage and the second adjustment voltage to the threshold output unit, The threshold voltage adjustment unit is generating the first regulated voltage and the second regulated voltage based on the correction command signal output from the control unit; The power conversion device according to claim 1 or 2.

4. the power conversion unit is a full bridge circuit in which the power semiconductor element of an upper arm and the power semiconductor element of a lower arm are connected in series, The overcurrent protection circuit includes: a first comparator that determines that an overcurrent has flowed through the power semiconductor element of the upper arm by comparing a detection voltage output by the current sensor with the overcurrent threshold voltage on a positive side and generates the overcurrent stop signal on a positive side; a second comparator that determines that an overcurrent has flowed through the power semiconductor element of the lower arm by comparing a detection voltage output by the current sensor with the overcurrent threshold voltage on a negative side and generates the overcurrent stop signal on a negative side; A first threshold output unit that outputs the positive overcurrent threshold voltage; A second threshold output unit that outputs the negative overcurrent threshold voltage; a threshold voltage adjustment unit that outputs a first adjusted voltage to a first threshold output unit and outputs a second adjusted voltage to a second threshold output unit, the control unit outputs the first correction command signal and the second correction command signal to the overcurrent protection circuit; The threshold voltage adjustment unit is generating a first regulated voltage based on the first corrected command signal, and generating a second regulated voltage based on the second corrected command signal; The power conversion device according to claim 1 or 2.

5. The current sensor further includes a temperature sensor for detecting a temperature of the current sensor. The control unit is The temperature map includes characteristic data of an output voltage versus a current detected by the current sensor, the characteristic data being measured in advance at a plurality of temperatures, generating the correction command signal based on a total correction amount obtained by adding together the temperature correction amount extracted based on the temperature information detected by the temperature sensor and the temperature map and the voltage correction amount; The power conversion device according to claim 1 or 2.

6. The temperature correction amount is a change amount of the detection voltage output by the current sensor with respect to the overcurrent setting value with respect to a preset reference temperature. The power converter according to claim 5.

7. the correction command signal is a pulse signal whose duty ratio is changeable, the threshold voltage adjustment unit includes a smoothing circuit that smoothes the pulse signal or an inverted pulse signal obtained by inverting the pulse signal, and outputs an adjustment source voltage; the threshold output unit is a series circuit in which a plurality of resistors are connected in series between a power supply voltage and a ground, a connection point between the resistors in the series circuit is connected to the comparator, and an output point from which the regulated source voltage is output is connected to the connection point via a resistor. The power conversion device according to claim 1 or 2.

8. the power conversion unit is a full bridge circuit in which the power semiconductor element of an upper arm and the power semiconductor element of a lower arm are connected in series, The overcurrent protection circuit includes: a first comparator that determines that an overcurrent has flowed through the power semiconductor element of the upper arm by comparing a detection voltage output by the current sensor with the overcurrent threshold voltage on a positive side and generates the overcurrent stop signal on a positive side; a second comparator that determines that an overcurrent has flowed through the power semiconductor element of the lower arm by comparing a detection voltage output by the current sensor with the overcurrent threshold voltage on a negative side and generates the overcurrent stop signal on a negative side; the threshold output unit that outputs the positive overcurrent threshold voltage and the negative overcurrent threshold voltage; a threshold voltage adjustment unit that outputs the first adjustment voltage and the second adjustment voltage to the threshold output unit, The threshold voltage adjustment unit is a first smoothing circuit that smoothes the pulse signal and outputs a first regulated source voltage, and a second smoothing circuit that smoothes the pulse signal and outputs a second regulated source voltage, the threshold output unit is a series circuit in which a first resistor, a second resistor, and a third resistor are connected in series between a power supply voltage and a ground, a first connection point at which the first resistor and the second resistor on the power supply voltage side are connected is connected to the first comparator; an output point of the first smoothing circuit, from which the first regulated source voltage is output, is connected to the first connection point via a resistor; a second connection point at which the third resistor and the second resistor on the ground side are connected is connected to a second comparator; an output point of the second smoothing circuit, from which the second regulated source voltage is output, is connected to the second connection point via a resistor; The power converter according to claim 7.

9. the power conversion unit is a full bridge circuit in which the power semiconductor element of an upper arm and the power semiconductor element of a lower arm are connected in series, The overcurrent protection circuit includes: a first comparator that determines that an overcurrent has flowed through the power semiconductor element of the upper arm by comparing a detection voltage output by the current sensor with the overcurrent threshold voltage on a positive side and generates the overcurrent stop signal on a positive side; a second comparator that determines that an overcurrent has flowed through the power semiconductor element of the lower arm by comparing a detection voltage output by the current sensor with the negative overcurrent threshold voltage, and generates the negative overcurrent stop signal; the threshold output unit that outputs the positive overcurrent threshold voltage and the negative overcurrent threshold voltage; a threshold voltage adjustment unit that outputs the first adjustment voltage and the second adjustment voltage to the threshold output unit, The threshold voltage adjustment unit is a first smoothing circuit that smoothes the pulse signal and outputs a first regulated source voltage, and a second smoothing circuit that smoothes an inverted pulse signal obtained by inverting the pulse signal by an inverter and outputs a second regulated source voltage, the threshold output unit is a series circuit in which a first resistor, a second resistor, and a third resistor are connected in series between a power supply voltage and a ground, a first connection point at which the first resistor and the second resistor on the power supply voltage side are connected is connected to the first comparator; an output point of the first smoothing circuit, from which the first regulated source voltage is output, is connected to the first connection point via a resistor; a second connection point at which the third resistor and the second resistor on the ground side are connected is connected to a second comparator; an output point of the second smoothing circuit, from which the second regulated source voltage is output, is connected to the second connection point via a resistor; The power converter according to claim 7.

10. The voltage correction amount data is a first characteristic data of an output voltage with respect to a current detected by the current sensor, which is actually measured in advance; a first threshold data of the positive side overcurrent threshold voltage with respect to the duty ratio at the positive side overcurrent setting value; and a second threshold data of the negative side overcurrent threshold voltage with respect to the duty ratio at the negative side overcurrent setting value, The control unit is A first overcurrent threshold, which is the positive side overcurrent threshold voltage for the positive side overcurrent setting value, is calculated from the first characteristic data within a positive settable range, and a second overcurrent threshold, which is the negative side overcurrent threshold voltage for the negative side overcurrent setting value, is calculated from the first characteristic data within a negative settable range; Calculating a first voltage correction amount, which is the voltage correction amount for the first overcurrent threshold obtained by calculation, and a second voltage correction amount, which is the voltage correction amount for the second overcurrent threshold obtained by calculation; When generating the correction command signal, In the case of condition A, a first limit condition in which the first overcurrent threshold is the limit value of the positive side settable range or a second limit condition in which the second overcurrent threshold is the limit value of the negative side settable range is satisfied. If only one of the first limit condition and the second limit condition is satisfied, a duty ratio value derived based on the limit value and one of the first threshold data and the second threshold data corresponding to the limit value is determined as a selected duty ratio value; If the first limit condition and the second limit condition are satisfied, a limit value corresponding to the smaller correction amount between the first voltage correction amount and the second voltage correction amount is set as a selected limit value, and a value of the duty ratio derived based on the selected limit value and one of the first threshold data and the second threshold data corresponding to the selected limit value is determined as a selected duty ratio value; In the case of a condition B other than the condition A, in which the first voltage correction amount and the second voltage correction amount are different, the smaller correction amount is determined as a selected voltage correction amount, and the value of the duty ratio derived based on the selected voltage correction amount and one of the first threshold data and the second threshold data corresponding to the selected voltage correction amount is determined as a selected duty ratio value; In the case of a condition C other than the condition A and the condition B, in which the first voltage correction amount and the second voltage correction amount are the same, a first duty ratio value which is the value of the duty ratio derived based on the first voltage correction amount and the first threshold data, and a second duty ratio value which is the value of the duty ratio derived based on the second voltage correction amount and the second threshold data, If the first duty ratio value and the second duty ratio value are the same, the duty ratio of the first duty ratio value is determined as a selected duty ratio value; If the first duty ratio value and the second duty ratio value are different, a third voltage correction amount, which is the voltage correction amount calculated from the voltage value of the second threshold data for the first duty ratio value, is compared with a fourth voltage correction amount, which is the voltage correction amount calculated from the voltage value of the first threshold data for the second duty ratio value, and the duty ratio value which has a smaller correction amount is determined as a selected duty ratio value; generating the pulse signal having the selected duty ratio value as the correction command signal; The power converter according to claim 9.

11. the power conversion unit is a full bridge circuit in which the power semiconductor element of an upper arm and the power semiconductor element of a lower arm are connected in series, The overcurrent protection circuit includes: a first comparator that determines that an overcurrent has flowed through the power semiconductor element of the upper arm by comparing a detection voltage output by the current sensor with the overcurrent threshold voltage on a positive side and generates the overcurrent stop signal on a positive side; a second comparator that determines that an overcurrent has flowed through the power semiconductor element of the lower arm by comparing a detection voltage output by the current sensor with the overcurrent threshold voltage on a negative side and generates the overcurrent stop signal on a negative side; the threshold output unit that outputs the positive overcurrent threshold voltage and the negative overcurrent threshold voltage; a threshold voltage adjustment unit that outputs a first adjusted voltage to a first threshold output unit and outputs a second adjusted voltage to a second threshold output unit, the control unit outputs a first adjustment source voltage and a second adjustment source voltage to the overcurrent protection circuit as a first correction command signal and a second correction command signal, respectively; The threshold voltage adjustment unit is a first input resistor for adjusting the first regulated voltage to a first regulated voltage, and a second input resistor for adjusting the second regulated voltage to a second regulated voltage, the threshold output unit is a series circuit including a first resistor, a second resistor, and a third resistor connected in series between a power supply voltage and a ground, a first connection point at which the first resistor and the second resistor on the power supply voltage side are connected is connected to the first comparator; One end of the first input resistor at a side where the first regulated voltage is output is connected to the first connection point, a second connection point at which the third resistor and the second resistor on the ground side are connected is connected to a second comparator; One end of the second input resistor at a side where the second regulated voltage is output is connected to the second connection point. The power conversion device according to claim 1 or 2.

12. The AC power handled by the power conversion unit is three-phase AC power, the current sensors are three current sensors detecting respective phases of a three-phase AC current of the power conversion unit, The overcurrent protection circuit includes: a first comparator and a second comparator are provided for each phase of a three-phase AC current; The three first comparators receive the same positive overcurrent threshold voltage output from the threshold output unit, The three second comparators are input with the same negative overcurrent threshold voltage output from the threshold output unit. The power converter according to claim 9.

13. The AC power handled by the power conversion unit is three-phase AC power, the current sensors are three current sensors detecting respective phases of a three-phase AC current of the power conversion unit, the first correction command signal and the second correction command signal are pulse signals whose duty ratios are changeable, The overcurrent protection circuit includes: a first comparator and a second comparator are provided for each phase of a three-phase AC current; The three first comparators receive the same positive overcurrent threshold voltage output from the first threshold output unit, The three second comparators receive the same negative overcurrent threshold voltage output from the second threshold output unit, The threshold voltage adjustment unit is a first smoothing circuit that smoothes the pulse signal of the first correction command signal to output a first adjustment source voltage, and a second smoothing circuit that smoothes the pulse signal of the second correction command signal to output a second adjustment source voltage, The first threshold output unit is a first series circuit in which a plurality of resistors are connected in series between a power supply voltage and a ground, The second threshold output unit is a second series circuit in which a plurality of resistors are connected in series between a power supply voltage and ground, a first connection point which is a connection point between the resistors in the first series body is connected to three first comparators, and an output point at which the first regulated source voltage is output is connected to the first connection point via a resistor; a second connection point which is a connection point between the resistors in the second series body is connected to three second comparators, and an output point at which the second regulated source voltage is output is connected to the second connection point via a resistor; The power converter according to claim 4.

14. The overcurrent protection circuit includes: a voltage detection circuit that detects the positive overcurrent threshold voltage and outputs the detected voltage as threshold detection voltage information; the control unit corrects the voltage correction amount so that a difference between the voltage indicated by the threshold detection voltage information and the overcurrent threshold voltage calculated from the voltage correction amount becomes small, and adjusts a duty ratio of the pulse signal based on the corrected voltage correction amount. The power converter according to claim 9.

15. The overcurrent protection circuit includes: a voltage detection circuit that detects the positive overcurrent threshold voltage and outputs the detected voltage as threshold detection voltage information; the control unit adjusts a duty ratio of the pulse signal so that a difference between the positive overcurrent threshold voltage calculated from the first characteristic data and a voltage indicated by the threshold detection voltage information becomes small or falls within a predetermined difference range. The power converter according to claim 10.

16. The AC power handled by the power conversion unit is three-phase AC power, the current sensors are three current sensors detecting respective phases of a three-phase AC current of the power conversion unit, The overcurrent protection circuit includes: The control circuit includes a first comparator, a second comparator, a threshold output unit, and a threshold voltage adjustment unit for each phase of a three-phase AC current. The power converter according to claim 15.

17. The overcurrent protection circuit includes: a voltage detection circuit that detects the positive overcurrent threshold voltage and outputs the detected voltage as threshold detection voltage information; the control unit corrects the voltage correction amount so that a difference between the voltage indicated by the threshold detection voltage information and the voltage correction amount corresponding to the positive overcurrent threshold voltage becomes small, and adjusts a duty ratio of the pulse signal based on the corrected voltage correction amount. The power converter according to claim 12.

18. The overcurrent protection circuit includes: a voltage detection circuit that detects the positive overcurrent threshold voltage and outputs the detected voltage as threshold detection voltage information; The voltage correction amount data is First characteristic data of an output voltage versus a current detected by the current sensor for each phase, the first characteristic data being actually measured in advance; a first threshold data of the overcurrent threshold voltage on a positive side for the duty ratio at the overcurrent setting value on a positive side, and a second threshold data of the overcurrent threshold voltage on a negative side for the duty ratio at the overcurrent setting value on a negative side, the control unit adjusts a duty ratio of the pulse signal so that a difference between the positive overcurrent threshold voltage determined based on the first characteristic data of each phase and a voltage indicated by the threshold detection voltage information becomes small or falls within a predetermined difference range. The power converter according to claim 12.

19. The voltage correction amount data is a first characteristic data of an output voltage for a current detected by the current sensor for each phase, which is actually measured in advance; a first threshold data of the positive side overcurrent threshold voltage for the duty ratio at the positive side overcurrent setting value; and a second threshold data of the negative side overcurrent threshold voltage for the duty ratio at the negative side overcurrent setting value, The control unit is A first overcurrent threshold is calculated for each phase from the first characteristic data within a positive settable range, the first overcurrent threshold being the positive overcurrent threshold voltage for the positive overcurrent setting value, and a second overcurrent threshold is calculated for each phase from the first characteristic data within a negative settable range, the second overcurrent threshold being the negative overcurrent threshold voltage for the negative overcurrent setting value; Calculating, for each phase, a first voltage correction amount which is the voltage correction amount for the first overcurrent threshold obtained by calculation, and a second voltage correction amount which is the voltage correction amount for the second overcurrent threshold obtained by calculation; When generating the first correction command signal, determining a smallest correction amount among the first voltage correction amounts of each phase as a selected voltage correction amount, and determining a value of the duty ratio derived based on the selected voltage correction amount and the first threshold data corresponding to the selected voltage correction amount as a first selected duty ratio value; generating the pulse signal having the determined first selected duty ratio value as a first correction command signal; When generating the second correction command signal, determining a smallest correction amount among the second voltage correction amounts of each phase as a selected voltage correction amount, and determining a value of the duty ratio derived based on the selected voltage correction amount and the second threshold data corresponding to the selected voltage correction amount as a second selected duty ratio value; generating the pulse signal having the determined second selected duty ratio value as a second correction command signal; The power converter according to claim 13.

20. The voltage correction amount data is a first characteristic data of an output voltage for a current detected by the current sensor for each phase, which is actually measured in advance; a first threshold data of the positive side overcurrent threshold voltage for the duty ratio at the positive side overcurrent setting value; and a second threshold data of the negative side overcurrent threshold voltage for the duty ratio at the negative side overcurrent setting value, The control unit is A first overcurrent threshold is calculated for each phase from the first characteristic data within a positive settable range, the first overcurrent threshold being the positive overcurrent threshold voltage for the positive overcurrent setting value, and a second overcurrent threshold is calculated for each phase from the first characteristic data within a negative settable range, the second overcurrent threshold being the negative overcurrent threshold voltage for the negative overcurrent setting value; Calculating a first voltage correction amount, which is the voltage correction amount for the first overcurrent threshold obtained by calculation, and a second voltage correction amount, which is the voltage correction amount for the second overcurrent threshold obtained by calculation; When generating the correction command signal, In the case of condition A, the three first overcurrent thresholds include the limit value of the positive side settable range or the three second overcurrent thresholds include the limit value of the negative side settable range, If one of the three first overcurrent thresholds and the three second overcurrent thresholds is a limit value, a duty ratio value derived based on the limit value and one of the first threshold data and the second threshold data corresponding to the limit value is determined as a selected duty ratio value; If two or more of the three first overcurrent thresholds and the three second overcurrent thresholds are limit values, a limit value corresponding to the smallest of the first voltage correction amount or the second voltage correction amount corresponding to the candidate limit value is set as a selected limit value, and a value of the duty ratio derived based on the selected limit value and one of the first threshold data and the second threshold data corresponding to the selected limit value is determined as a selected duty ratio value; In the case of a condition B other than the condition A, in which the three first voltage correction amounts and the three second voltage correction amounts are not the same, the smallest correction amount is determined as a selected voltage correction amount, and the value of the duty ratio derived based on the selected voltage correction amount and one of the first threshold data and the second threshold data corresponding to the selected voltage correction amount is determined as a selected duty ratio value; In the case of a condition C other than the condition A and the condition B, in which the three first voltage correction amounts and the three second voltage correction amounts are the same, a first duty ratio value which is the value of the duty ratio derived based on the first voltage correction amount and the first threshold data, and a second duty ratio value which is the value of the duty ratio derived based on the second voltage correction amount and the second threshold data, If the first duty ratio value and the second duty ratio value are the same, the duty ratio of the first duty ratio value is determined as a selected duty ratio value; If the first duty ratio value and the second duty ratio value are different, a third voltage correction amount, which is the voltage correction amount calculated from the voltage value of the second threshold data for the first duty ratio value, is compared with a fourth voltage correction amount, which is the voltage correction amount calculated from the voltage value of the first threshold data for the second duty ratio value, and the duty ratio value which has a smaller correction amount is determined as a selected duty ratio value; generating the pulse signal having the selected duty ratio value as the correction command signal; The power converter according to claim 12.

21. 3. The power conversion device according to claim 1, wherein the power semiconductor element is a power semiconductor element using a wide band gap semiconductor material.

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