Power converter

Abstract

This power conversion device comprises: an inverter circuit formed by connecting, in series, switching elements of an upper arm and a lower arm; an output current detector that outputs a detection value of AC current output from a connection point between the switching elements of the upper arm and the lower arm; a driver circuit that drives the switching elements by driving signals via a switched gate resistor; an overcurrent detection circuit that compares the detection value and one of a predetermined plurality of overcurrent thresholds and, when the detection value is greater than the overcurrent threshold, outputs an overcurrent detection signal; and a controller that sends the driving signals, sends, to the driver circuit, a gate resistance switching signal for switching the gate resistor, and sends an overcurrent threshold switching signal for switching the overcurrent threshold. When the controller has been switched, by using the gate resistance switching signal, to the gate resistor for which a resistance value is lower, the controller sets the overcurrent threshold to a small value, by using the overcurrent threshold switching signal.

Description

Technical Field

[0001] The present invention relates to a power conversion device.

Background Art

[0002] A power conversion device that converts DC power into AC power includes a plurality of phases of arms each configured by connecting an upper-arm switching element and a lower-arm switching element in series. The switching element is driven by a drive signal input via a gate resistor connected to the gate of the switching element.

[0003] Generally, a switching element generates switching losses when energized, but the switching speed of the switching element is increased and the losses of the switching element are reduced by switching the gate resistor according to the operating conditions of the switching element such as the applied voltage and current. On the other hand, when the switching element turns off, a surge voltage is generated in proportion to the rate of decrease of the collector current.

[0004] Patent Document 1 describes a power conversion device that varies the gate resistor under conditions where the surge voltage becomes high.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the technique described in Patent Document 1, when the motor current suddenly increases due to some abnormality in a state where the resistance value of the gate resistor is low, there is a risk of causing the switching element to fail due to the surge voltage, and the reliability of the power conversion device is reduced.

Means for Solving the Problems

[0007] The power conversion device according to the present invention comprises an inverter circuit having multiple phase arms, each arm having an upper arm switching element and a lower arm switching element connected in series between the positive and negative terminals of a DC power line; an output current detector that detects the AC current output from the connection point between the upper arm switching element and the lower arm switching element and outputs a detected value; a driver circuit that drives each switching element by a drive signal input via the switched gate resistor, and has a gate resistance switching circuit that switches the gate resistor connected to the gate of each switching element; an overcurrent detection circuit that compares the detected value detected by the output current detector with one of a predetermined number of overcurrent thresholds and outputs an overcurrent detection signal when the detected value exceeds the overcurrent threshold; and a controller that transmits the drive signal to the driver circuit, transmits a gate resistance switching signal to the driver circuit to switch the gate resistor, and transmits an overcurrent threshold switching signal to the overcurrent detection circuit to switch the overcurrent threshold, wherein the controller, by the gate resistance switching signal , compared to before the switch When switching to the gate resistor with a lower resistance value, the overcurrent threshold switching signal is used. , compared to before switching the gate resistor Set the overcurrent threshold to a small value. [Effects of the Invention]

[0008] According to the present invention, it is possible to improve the reliability of the power conversion device even when the resistance value of the gate resistor is reduced. [Brief explanation of the drawing]

[0009] [Figure 1] This is an overall configuration diagram of the power converter in the first embodiment. [Figure 2] This is a detailed configuration diagram of the main components of the power converter in the first embodiment. [Figure 3] (a)(B) These graphs show the relationship between the collector-emitter voltage of a switching element, the switching of the gate resistance, and the relationship between the overcurrent threshold and the AC current. [Figure 4] This is a detailed configuration diagram of the main components of the power converter in the second embodiment. [Figure 5] This is a detailed configuration diagram of the main components of the power converter in the third embodiment.

[0010] Embodiments of the present invention will be described below with reference to the drawings. The following description and drawings are illustrative for illustrating the present invention, and have been omitted and simplified as appropriate for clarity of explanation. The present invention can also be carried out in various other forms. Unless otherwise specified, each component may be singular or plural.

[0011] [First Embodiment] Figure 1 is an overall configuration diagram of the power converter 1000 in the first embodiment. The power converter 1000 converts DC power supplied from a DC power source 2000, such as a battery, into AC power to drive the motor 3000. The DC power source 2000 supplies DC power between the positive terminal P and the negative terminal N of the power converter 1000 via a contactor 2001. The motor 3000 is, for example, a three-phase induction motor and is used as a power source for a vehicle.

[0012] The power converter 1000 includes a voltage detector 100 connected in parallel between the positive terminal P and the negative terminal N to detect the DC voltage between the positive terminal P and the negative terminal N, a capacitor module 200 for smoothing the DC current, and an inverter circuit 300 for performing power conversion. Furthermore, the power converter 1000 includes an output current detector 400, an overcurrent detection circuit 500, a controller 600, a cutoff circuit 700, and a driver circuit 800.

[0013] The inverter circuit 300 includes a power module 310 having an upper and lower arm series circuit consisting of a switching element 311 and diode 312 that operates as an upper arm, and a switching element 321 and diode 322 that operates as a lower arm. Three power modules 310 are provided for each phase (U phase, V phase, W phase) corresponding to the phase windings of the motor 3000. In other words, the inverter circuit 300 has three arms, each consisting of an upper arm switching element 311 and a lower arm switching element 321 connected in series between the positive DC terminal P and the negative DC terminal N. Here, we explain using a three-phase example, but for example, a configuration with multiple power modules 310 corresponding to the number of phases of the motor 3000 is also possible.

[0014] The output current detector 400 detects the AC current output from the connection point between the switching element of the upper arm and the switching element of the lower arm for each phase, and outputs the detected value Ei to the overcurrent detection circuit 500 and the controller 600. The detected value Ei represents the magnitude of the detected AC current as a voltage value.

[0015] The overcurrent detection circuit 500 is provided for each phase and outputs an overcurrent detection signal Em to the controller 600 and the cutoff circuit 700 when the detected value of the AC current exceeds the overcurrent threshold. Details of the overcurrent detection circuit 500 will be described later.

[0016] Controller 600 receives a low voltage from the low voltage power supply 4000 when the vehicle's ignition key is ON, as the low voltage power supply 4000 is connected to the low voltage power supply 4000 from outside the power converter 1000. Then, in response to a torque command from a higher-level controller (not shown in the diagram), a detected voltage Vdc from the voltage detector 100, a detected value Ei from the output current detector 400, and an overcurrent detection signal Em from the overcurrent detection circuit 500, it outputs a drive signal Pw to the driver circuit 800 via the cutoff circuit 700. Controller 600 also outputs an overcurrent threshold switching signal Ts to the overcurrent detection circuit 500. Furthermore, it transmits a gate resistance switching signal Rs to the driver circuit 800 to switch the gate resistance according to the detected value from the output current detector 400. Details of controller 600 will be described later.

[0017] The cutoff circuit 700 is provided corresponding to the driver circuit 800, and in response to the overcurrent detection signal Em output from the overcurrent detection circuit 500, cuts off the drive signal Pw from the controller 600 to the switching elements 311 and 321. Details of the cutoff circuit 700 will be described later. The driver circuit 800 is provided corresponding to each of the switching elements 311 and 321, has a gate resistance switching circuit that switches the gate resistances connected to the gates of the respective switching elements 311 and 321, and drives the switching elements 311 and 321 with the drive signal Pw input through the switched gate resistances. Details of the driver circuit 800 will be described later.

[0018] FIG. 2 is a detailed configuration diagram of the main part of the power conversion device 1000 in the first embodiment. In this figure, an overcurrent detection circuit 500 corresponding to the power module 310 for one phase, and a cutoff circuit 700 and a driver circuit 800 corresponding to the switching element 321 of the lower arm of the power module 310 for one phase are shown. That is, the cutoff circuit 700 and the driver circuit 800 corresponding to the switching element 311 of the upper arm of the power module 310 for one phase are not shown in the figure, but have the same configuration as the cutoff circuit 700 and the driver circuit 800 corresponding to the switching element 321 of the lower arm. Further, the overcurrent detection circuit 500 corresponding to the power module 310 of other phases, and the cutoff circuit 700 and the driver circuit 800 corresponding to the switching elements 311 and 321 of the power module 310 of other phases also have the same configuration as in FIG. 2.

[0019] The detected value Ei from the output current detector 400 is input to the overcurrent detection circuit 500 and the controller 600. The detected voltage Vdc from the voltage detector 100 is input to the controller 600.

[0020] The controller 600 transmits the drive signal Pw to the driver circuit 800 via the cutoff circuit 700. Also, the controller 600 transmits a gate resistance switching signal Rs for switching the gate resistance to the driver circuit 800. The drive signal Pw is a PWM signal. When an overcurrent detection signal Em (which will be described in detail later by the overcurrent detection circuit 500) is input, the cutoff circuit 700 immediately cuts off the drive signal Pw. As a result, the driving of the switching element 321 by the driver circuit 800 is stopped.

[0021] The driver circuit 800 includes a drive circuit 810 and a gate resistance switching circuit 820. The gate resistance switching circuit 820 switches the gate resistances Rf1 and Rf2 connected to the gate of the switching element 321 according to the gate resistance switching signal Rs. The gate resistance Rn0 is a resistance connected when the switching element 321 is turned on. The gate resistances Rf1 and Rf2 are resistances connected when the switching element 321 is turned off, and the resistance value of the gate resistance Rf1 is lower than the resistance value of the gate resistance Rf2. In response to the input of the gate resistance switching signal Rs, the resistance when the switching element 321 is off is switched to the gate resistance Rf1.

[0022] Generally, switching losses occur in the switching element 321, which is a factor reducing the efficiency of the inverter circuit 300 and thus the cruising range of the vehicle. Therefore, depending on the operating conditions of the switching element 321 such as voltage and current, when the switching element 321 is turned off, by switching to the gate resistance Rf1 with a low resistance value, the switching speed is increased to reduce the switching losses of the switching element 321. Specifically, when it is detected that the DC voltage, which is the detected voltage Vdc detected by the voltage detector 100, is low and the current flowing through the motor 3000 detected by the output current detector 400 is low, the allowable surge voltage becomes high. In this case, it is switched to the gate resistance Rf1 with a low resistance value to increase the switching speed further and reduce the switching losses.

[0023] However, if the current flowing to the motor 3000 increases rapidly due to some abnormality while the gate resistor's resistance value is low, there is a risk that the surge voltage may cause the switching element 321 to fail. Therefore, when the controller 600 switches to the gate resistor Rf1 with a low resistance value, it sends an overcurrent threshold switching signal Ts to the overcurrent detection circuit 500 described later, setting the overcurrent threshold to a small value. That is, the controller 600 outputs the overcurrent threshold switching signal Ts at approximately the same time as it switches to the gate resistor Rf1 using the gate resistor switching signal Rs, setting the overcurrent threshold of the overcurrent detection circuit 500 to a small value. This prevents the switching element 321 from failing and improves the reliability of the power converter 1000 even when the gate resistor's resistance value is low.

[0024] As shown in Figure 2, the overcurrent detection circuit 500 includes a threshold switching unit 510 and a comparison unit 520. The threshold switching unit 510 switches the threshold to overcurrent thresholds VH1, VL1, or VH2, VL2 using a switch SW. Specifically, the switch SW is operated by an overcurrent threshold switching signal Ts from the controller 600, and overcurrent thresholds VH1, VL1 are selected. When the overcurrent threshold switching signal Ts disappears, overcurrent thresholds VH2, VL2 are selected. The unit of the threshold is voltage, and the relationships are overcurrent threshold VH1 < overcurrent threshold VH2 and overcurrent threshold VL1 < overcurrent threshold VL2. The overcurrent thresholds VH1, VL1, VH2, and VL2 are supplied from multiple power sources with different voltage values.

[0025] The comparison unit 520 includes a comparator CH that compares the detected value Ei from the output current detector 400 with the overcurrent threshold VH1 or VH2, and a comparator CL that compares the detected value Ei with the overcurrent threshold VL1 or VL2, and outputs an overcurrent detection signal Em according to the comparison result. If there is no overcurrent threshold switching signal Ts and overcurrent thresholds VH2 or VL2 are selected, the overcurrent detection signal Em is not output if the detected value Ei is within the range of overcurrent thresholds VH2 or VL2. If the detected value Ei exceeds the range of overcurrent thresholds VH2 or VL2, the overcurrent detection signal Em is output. If overcurrent thresholds VH1 or VL1 are selected by the overcurrent threshold switching signal Ts, the overcurrent detection signal Em is not output if the detected value Ei is within the range of overcurrent thresholds VH1 or VL1. If the detected value Ei exceeds the range of overcurrent thresholds VH1 or VL1, the overcurrent detection signal Em is output. The overcurrent detection signal Em is input to the controller 600 and the cutoff circuit 700.

[0026] The overcurrent thresholds VH2 and VL2 are set to values ​​that indicate the current value at which the voltage applied to the switching element 321 does not exceed the allowable value of the switching element 321 when the switching element 321 is driven at the resistance value of the gate resistor Rf2. Similarly, the overcurrent thresholds VH1 and VL1 are set to values ​​that indicate the current value at which the voltage applied to the switching element 321 does not exceed the allowable value of the switching element 321 when the switching element 321 is driven at the resistance value of the gate resistor Rf1.

[0027] The controller 600 prevents overcurrent in the motor 3000 by stopping the output of the drive signal Pw when an overcurrent detection signal Em is input. Since the overcurrent detection signal Em is also input to the cutoff circuit 700, the drive signal Pw can be cut off immediately without waiting for the controller 600 to stop the output of the drive signal Pw.

[0028] Figure 3(a) is a graph showing the relationship between the voltage Vce applied between the collector and emitter of the switching element 321 and the current value I detected by the output current detector 400. The horizontal axis represents the current value I, and the vertical axis represents the voltage Vce. Figure 3(B) is a graph showing the relationship between the overcurrent threshold and the detected AC current value Ei. The horizontal axis represents time, and the vertical axis represents voltage.

[0029] Normally, when the switching element 321 turns off, the voltage Vce applied between the collector and emitter of the switching element 321 increases as the current flowing through the switching element 321 increases. Furthermore, the magnitude of this increase is greater when the switching speed is fast. In addition, the switching speed at the time of turn-off is inversely proportional to the resistance value of the gate resistor; it tends to be slower when the resistance value is high and faster when the resistance value is low. For this reason, the surge voltage is small when the resistance value is high and large when the resistance value is low.

[0030] On the other hand, when the switching speed is fast, the switching loss of the switching element 321 can be reduced, so the resistance value of the gate resistor can be lowered in the low current region, and the surge voltage can be kept below the allowable value while reducing losses.

[0031] In Figure 3(a), I0 is the current value used to switch to the gate resistor Rf1 with the lower resistance, I1 is the overcurrent detection level at the gate resistor Rf1 with the lower resistance, and I2 is the overcurrent detection level at the gate resistor Rf2 with the higher resistance. Vm is the allowable breakdown voltage of the switching element 321.

[0032] The graph in Figure 3(a) shows an example where the controller 600 switches to gate resistor Rf2 when the current value I is greater than the current value I0, and to gate resistor Rf1 when the current value I is less than or equal to the current value I0, based on the detected value Ei from the output current detector 400.

[0033] Here, we consider the case where the gate resistance remains Rf2 regardless of the current value I. In this case, as shown by the dotted line Vf2 in Figure 3(a), the voltage Vce applied to the switching element 321 gradually increases as the current increases from 0(A) to I0(A), I1(A), and I2(A).

[0034] However, if the motor 3000 or other components malfunction and the current increases rapidly, exceeding the maximum current, the voltage Vce applied to the switching element 321 may exceed the allowable withstand voltage Vm, potentially causing the switching element 321 to fail. To prepare for this situation, overcurrent thresholds VH2 and VL2 are set. Overcurrent thresholds VH2 and VL2 correspond to the overcurrent detection level I2. When the current reaches the overcurrent detection level I2, the controller 600 prevents the current flowing to the motor 3000 from increasing by controlling the transmission of the PWM signal, thereby controlling the voltage Vce applied to the switching element 321 so that it does not exceed the allowable withstand voltage Vm.

[0035] On the other hand, when switching between gate resistors Rf1 and Rf2, in the low-current region where the current is I0 or less, the switch is made to the gate resistor Rf1 with the lower resistance value to increase the switching speed of the switching element 321. Here, if an overcurrent condition suddenly occurs in the state with the low gate resistance Rf1, the increase in surge voltage is greater than when the resistance value is high. For this reason, if the overcurrent detection level remains at I2, as shown by the dotted line Vf1 in Figure 3(a), the voltage Vce will exceed the allowable withstand voltage Vm when the current is greater than I1.

[0036] In this embodiment, when the gate resistance is set to a low value, the overcurrent detection level is set to an overcurrent detection level I1, which is lower than I2. The overcurrent detection level I1 corresponds to the overcurrent thresholds VH1 and VL1. This is the value at which the voltage applied to the switching element 321 does not exceed the allowable value of the switching element 321 when the switching element 321 is driven by the gate resistance Rf1. As shown by the thick solid line Vf in Figure 3(a), the overcurrent detection level is set to overcurrent detection level I1 when the gate resistance is switched to a low value Rf1, and to overcurrent detection level I2 when the gate resistance is switched to a high value Rf2.

[0037] As shown in Figure 3(b), when the gate resistance Rf1 is switched to a low value, if the detected value Ei from the output current detector 400 exceeds the range of the overcurrent thresholds VH1 and VL1, the overcurrent detection circuit 500 detects this and outputs an overcurrent detection signal Em. This makes it possible to prevent failure of the switching element 321 and improve the reliability of the power converter 1000, even when the switching speed of the switching element 321 is increased by switching the resistance value of the gate resistor.

[0038] In this example, we have described a case where the gate resistance is switched in two stages, but a configuration with three or more stages of switching is also possible. In this case, the gate resistance switching circuit 820 switches multiple gate resistances, and the overcurrent detection circuit 500 switches multiple overcurrent thresholds according to the switched gate resistances.

[0039] [Second Embodiment] Figure 4 is a detailed configuration diagram of the main components of the power converter 1000 in the second embodiment. In this figure, as in Figure 2, the overcurrent detection circuit 500 corresponding to one phase power module 310 and the interruption circuit 700 and driver circuit 800 corresponding to the switching element 321 on the lower arm of one phase power module 310 are shown. The same reference numerals are used for the same parts as in Figure 2, and their explanations are simplified. The overall configuration diagram of the power converter 1000 is the same as in Figure 1. In the second embodiment, the configuration of the overcurrent detection circuit 500 differs from that of the first embodiment.

[0040] As shown in Figure 4, the overcurrent detection circuit 500 includes a threshold switching unit 510 and a comparison unit 520. Similar to Figure 2, the comparison unit 520 includes a comparator CH that compares the detected value Ei from the output current detector 400 with the overcurrent threshold VH1 or VH2, and a comparator CL that compares the detected value Ei with the overcurrent threshold VL1 or VL2, and outputs an overcurrent detection signal Em according to the comparison result.

[0041] The threshold switching unit 510 includes resistors R1, R2, and R3 connected in series with the reference power supply, resistor R4 connected in parallel with resistor R1 via FET 511, and resistor R5 connected in parallel with resistor R3 via FET 512. Multiple overcurrent thresholds are supplied by dividing the voltage from a single power supply. At low levels when the overcurrent threshold switching signal Ts from the controller 600 is not output, FET 511 via the knot gate 513 and FET 512 without the knot gate 513 are off. In this case, the overcurrent threshold VH2 divided by resistors R1, R2, and R3 is input to comparator CH, and the overcurrent threshold VL2 is input to comparator CL. At high levels when the overcurrent threshold switching signal Ts from the controller 600 is output, FETs 511 and 512 are turned on, so resistor R4 is connected in parallel with resistor R1 and resistor R5 is connected in parallel with resistor R3, reducing their resistance values. Therefore, the overcurrent threshold VH1 is input to comparator CH, and the overcurrent threshold VL1 is input to comparator CL.

[0042] When the controller 600 switches to a gate resistor with a lower resistance value using the gate resistance switching signal Rs, it sets the overcurrent threshold to a smaller value using the overcurrent threshold switching signal Ts. Then, when the overcurrent detection signal Em is input, the controller 600 performs control to prevent overcurrent of the motor 3000, such as stopping the output of the drive signal Pw. According to this embodiment, even when the switching speed of the switching element 321 is increased by switching the resistance value of the gate resistor, it is possible to prevent failure of the switching element 321 and improve the reliability of the power converter 1000, as well as simplify the configuration of the overcurrent detection circuit 500.

[0043] [Third Embodiment] Figure 5 is a detailed configuration diagram of the main components of the power converter 1000 in the third embodiment. This figure shows the interruption circuit 700 and driver circuit 800 corresponding to the switching element 321 on the lower arm of the single-phase power module 310. The overcurrent detection circuit 500 is provided within the driver circuit 800. The same reference numerals are used for the same parts as in Figure 2, and their explanations are simplified. The overall configuration diagram of the power converter 1000 is the same as in Figure 1. In the third embodiment, the configuration of the output current detection circuit 410 and the overcurrent detection circuit 500 differs from that of the first embodiment.

[0044] As shown in Figure 5, the switching element 321 is equipped with a current sense terminal that divides the current flowing through the switching element 321. The output current detection circuit 410 converts the divided current into a voltage value using the sense resistor Rj, and outputs this as the detected value Ej to the overcurrent detection circuit 500.

[0045] The overcurrent detection circuit 500 includes a threshold switching unit 510 and a comparison unit 520. The threshold switching unit 510 selects the overcurrent threshold V2 by a switch SW if there is no overcurrent threshold switching signal Ts from the controller 600, and selects the overcurrent threshold V1 if there is an overcurrent threshold switching signal Ts. The relationship is overcurrent threshold V1 < overcurrent threshold V2. The comparison unit 520 compares the detected value Ej from the output current detection circuit 410 with the overcurrent threshold V1 or overcurrent threshold V2, and outputs an overcurrent detection signal Em according to the comparison result.

[0046] When the controller 600 switches to a gate resistor with a lower resistance value using the gate resistance switching signal Rs, it sets the overcurrent threshold to a smaller value using the overcurrent threshold switching signal Ts. Then, when the overcurrent detection signal Em is input, the controller 600 performs control to prevent overcurrent of the motor 3000, such as stopping the output of the drive signal Pw. According to this embodiment, even when the switching speed of the switching element 321 is increased by switching the resistance value of the gate resistor, it is possible to prevent failure of the switching element 321 and improve the reliability of the power converter 1000. In addition, the configuration of the output current detection circuit 410 and the overcurrent detection circuit 500 can be simplified.

[0047] According to the embodiments described above, the following effects and advantages can be obtained. (1) The power converter 1000 includes an inverter circuit 300 having multiple phases of arms, each arm consisting of an upper arm switching element 311 and a lower arm switching element 321 connected in series between the positive and negative DC terminals; an output current detector 400 that detects the AC current output from the connection point between the upper arm switching element 311 and the lower arm switching element 321 and outputs a detected value Ei; a gate resistance switching circuit 820 that switches gate resistors Rf1 and Rf2 connected to the gates of each switching element 311 and 321, and a driver circuit 800 that drives each switching element 311 and 321 by a drive signal Pw input via the switched gate resistors Rf1 and Rf2; and a predetermined value Ei detected by the output current detector 400. The system includes an overcurrent detection circuit 500 that compares the detected value Ei with one of several overcurrent thresholds VH1, VL1, VH2, and VL2 and outputs an overcurrent detection signal Em when the detected value Ei becomes larger than the overcurrent thresholds VH1, VL1, VH2, and VL2, and a controller 600 that sends a drive signal Pw to the driver circuit 800, sends a gate resistance switching signal Rs to the driver circuit 800 to switch gate resistors Rf1 and Rf2, and sends an overcurrent threshold switching signal Ts to the overcurrent detection circuit 500 to switch overcurrent thresholds VH1, VL1, VH2, and VL2. When the controller 600 switches to a gate resistor Rf1 with a lower resistance value using the gate resistance switching signal Rs, it sets the overcurrent thresholds VH1, VL1, VH2, and VL2 to smaller values ​​using the overcurrent threshold switching signal Ts. This makes it possible to improve the reliability of the power converter even when the resistance value of the gate resistor is lowered.

[0048] The present invention is not limited to the embodiments described above, and other forms conceivable within the scope of the technical concept of the present invention are also included within the scope of the present invention, as long as they do not impair the features of the present invention. Furthermore, configurations combining the embodiments described above are also possible. [Explanation of Symbols]

[0049] 100...Voltage detector, 200...Capacitor module, 300...Inverter circuit, 310...Power module, 311, 321...Switching element, 312, 322...Diode, 400...Output current detector, 410...Output current detection circuit, 500...Overcurrent detection circuit, 510...Threshold switching section, 520...Comparison section, 600...Controller, 700...Cutoff circuit, 800...Driver circuit, 810...Drive circuit 820...Gate resistance switching circuit, 1000...Power converter, 2000...DC power supply, 2001...Contactor, 3000...Motor, 4000...Low voltage power supply, Rn0, Rf1, Rf2...Gate resistance, Rs...Gate resistance switching signal, Pw...Drive signal, Vdc...Detected voltage, Ei, Ej...Detected value, VH1, VL1, VH2, VL2, V1, V2...Overcurrent threshold, Ts...Overcurrent threshold switching signal, Em...Overcurrent detection signal.

Claims

1. An inverter circuit having multiple phases of arms, each arm consisting of an upper arm switching element and a lower arm switching element connected in series between the positive and negative DC terminals, An output current detector that detects the AC current output from the connection point between the switching element of the upper arm and the switching element of the lower arm and outputs a detected value, A driver circuit having a gate resistance switching circuit that switches the gate resistance connected to the gate of each switching element, and which drives each switching element by a drive signal input via the switched gate resistance, An overcurrent detection circuit that compares the detected value detected by the output current detector with one of a predetermined number of overcurrent thresholds, and outputs an overcurrent detection signal when the detected value becomes greater than the overcurrent threshold, The system includes a controller that transmits the drive signal to the driver circuit, transmits a gate resistance switching signal to the driver circuit to switch the gate resistance, and transmits an overcurrent threshold switching signal to the overcurrent detection circuit to switch the overcurrent threshold, The controller is a power converter that, when it switches to a gate resistor with a lower resistance value than before the switch, uses the overcurrent threshold switching signal to set the overcurrent threshold to a smaller value than before the switch.

2. In the power conversion device according to claim 1, The overcurrent threshold is set to a value that indicates a current value such that the voltage applied to the switching element does not exceed the allowable value of the switching element when the switching element is driven by the switched gate resistor.

3. In the power conversion device according to claim 1 or claim 2, The overcurrent detection circuit is a power conversion device comprising a threshold switching unit that switches the plurality of overcurrent thresholds by an overcurrent threshold switching signal, and a comparison unit that compares the detected value with the overcurrent threshold.

4. In the power conversion device according to claim 3, The aforementioned multiple overcurrent thresholds are powered by a power converter supplied by multiple power sources with different voltage values.

5. In the power conversion device according to claim 3, The aforementioned multiple overcurrent thresholds are power converters that supply voltage by dividing the voltage from a single power source.

6. In the power conversion device according to claim 1 or claim 2, The controller includes a cutoff circuit that cuts off the drive signal transmitted to the driver circuit, The interruption circuit is a power conversion device that interrupts the drive signal in response to the overcurrent detection signal output from the overcurrent detection circuit.

7. An inverter circuit having multiple phases of arms, each arm consisting of an upper arm switching element and a lower arm switching element connected in series between the positive and negative DC terminals, An output current detection circuit that detects the current flowing through each of the aforementioned switching elements and outputs a detected value, The driver circuit has a gate resistance switching circuit that switches the gate resistance connected to the gate of each switching element, and drives each switching element with a drive signal using the switched gate resistance, An overcurrent detection circuit compares the detected value detected by the output current detection circuit with one of a predetermined number of overcurrent thresholds, and outputs an overcurrent detection signal when the detected value becomes greater than the overcurrent threshold; The controller includes a controller that transmits the drive signal to the driver circuit, transmits a gate resistance switching signal to the gate resistance switching circuit to switch the gate resistance, and transmits an overcurrent threshold switching signal to the overcurrent detection circuit to switch the overcurrent threshold, The controller is a power converter that, when it switches to a gate resistor with a lower resistance value than before the switch, uses the overcurrent threshold switching signal to set the overcurrent threshold to a smaller value than before the switch.

8. In the power conversion device according to claim 7, The output current detection circuit is a power conversion device that detects the current from a current sense terminal that divides the current flowing through the switching element and outputs the detected value.

Images