Deterioration diagnosis system, deterioration diagnosis method, and power conversion device

Abstract

The present invention addresses the problem of making it possible to diagnose deterioration of a semiconductor element. This deterioration diagnosis system is provided with: a semiconductor element having a gate, a first main terminal as a source or emitter, and a second main terminal as a drain or collector; a push-pull circuit; the grid resistor is arranged in the push-pull circuit or is arranged between the push-pull circuit and the grid; a capacitor connected in parallel with the gate resistor; and a deterioration diagnosis device that diagnoses deterioration of the semiconductor element using a capacitor voltage generated at both ends of the capacitor.

Description

Technical Field

[0001] The present invention relates to a degradation diagnosis system, a degradation diagnosis method, and a power conversion device. Background Art

[0002] A gate drive method is known in which the degradation of a power semiconductor is suppressed by controlling the time during which a voltage lower than the source potential is applied to the gate of the power semiconductor (for example, see Patent Document 1).

[0003] <Prior Art Documents>

[0004] <Patent Documents>

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2018-133892 Summary of the Invention

[0006] <Problems to be Solved by the Invention>

[0007] However, in the existing technology, the degradation of semiconductor elements cannot be diagnosed.

[0008] The present invention provides a degradation diagnosis system, a degradation diagnosis method, and a power conversion device capable of diagnosing the degradation of semiconductor elements.

[0009] <Means for Solving the Problems>

[0010] As one aspect, the present invention provides a degradation diagnosis system including:

[0011] a semiconductor element having a gate, a first main terminal serving as a source or an emitter, and a second main terminal serving as a drain or a collector;

[0012] a push-pull circuit;

[0013] a gate resistor provided in the push-pull circuit or between the push-pull circuit and the gate;

[0014] a capacitor connected in parallel with the gate resistor; and

[0015] a degradation diagnosis device that diagnoses the degradation of the semiconductor element using the capacitor voltage generated across the capacitor.

[0016] As another aspect, the present invention provides a degradation diagnosis method that diagnoses the degradation of a semiconductor element using the capacitor voltage generated across a capacitor connected in parallel with a gate resistor provided in a push-pull circuit or between the push-pull circuit and the gate of the semiconductor element.

[0017] The present invention provides, as another aspect, a power conversion device including:

[0018] a semiconductor element having a gate, a first main terminal serving as a source or an emitter, and a second main terminal serving as a drain or a collector;

[0019] a push-pull circuit;

[0020] a gate resistor provided in the push-pull circuit or between the push-pull circuit and the gate;

[0021] a capacitor connected in parallel with the gate resistor;

[0022] a degradation diagnosis device that diagnoses degradation of the semiconductor element using a capacitor voltage generated across the capacitor; and

[0023] a peak holding unit that holds a maximum value of the capacitor voltage during a fixed period according to an operation cycle of the semiconductor element.

[0024] <Effects of the Invention>

[0025] According to the present invention, degradation of a semiconductor element can be diagnosed. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 FIG. is a diagram showing a structural example of a degradation diagnosis system according to a first embodiment.

[0027] Figure 2 FIG. is a diagram for explaining degradation of a semiconductor element.

[0028] Figure 3 FIG. is a diagram for explaining a method of diagnosing degradation of a semiconductor element.

[0029] Figure 4 FIG. is a diagram for explaining a method of diagnosing degradation of a semiconductor element.

[0030] Figure 5 FIG. is a diagram showing a structural example of a degradation diagnosis system according to a second embodiment.

[0031] Figure 6 FIG. is a timing chart showing a first example of a method of sampling a maximum value of a capacitor voltage during a fixed period according to an operation cycle of a semiconductor element.

[0032] Figure 7 FIG. is a timing chart showing a second example of a method of sampling a maximum value of a capacitor voltage during a fixed period according to an operation cycle of a semiconductor element.

[0033] Figure 8It is a timing chart showing a third example of a method for sampling the maximum value during a fixed period of the capacitor voltage according to the operation cycle of a semiconductor element.

[0034] Figure 9 It is a diagram showing a structural example of the deterioration diagnosis system according to the third embodiment.

[0035] Figure 10 It is a diagram showing a structural example of the deterioration diagnosis system according to the fourth embodiment.

[0036] Figure 11 It is a diagram showing a structural example of the deterioration diagnosis system according to the fifth embodiment.

[0037] Figure 12 It is a diagram showing a structural example of the deterioration diagnosis system according to the sixth embodiment.

[0038] Figure 13 It is a diagram showing a first example of the application of the deterioration diagnosis system according to the present embodiment to a power conversion device.

[0039] Figure 14 It is a diagram showing a second example of the application of the deterioration diagnosis system according to the present embodiment to a power conversion device.

[0040] Symbol Explanation

[0041] 1: Semiconductor element

[0042] 10: Push-pull circuit

[0043] 11: First switch

[0044] 12: Second switch

[0045] 13: Power supply

[0046] 14: Connection point

[0047] 15: First power line

[0048] 16: Second power line

[0049] 20: Gate drive circuit

[0050] 21: Gate resistor

[0051] 22: Gate line

[0052] 23: Detection circuit

[0053] 30: Acceleration capacitor circuit

[0054] 31: Capacitor

[0055] 32: Discharge resistor

[0056] 33: Diode

[0057] 34: Reset circuit

[0058] 40: Degradation diagnosis device

[0059] 41: Peak hold section

[0060] 42: Comparison section

[0061] 43: Degradation diagnosis section

[0062] 50: Control device

[0063] 60: DC power supply

[0064] 63: Insulation section

[0065] 70: Inverter circuit

[0066] 71: Current sensor

[0067] 72: User interface

[0068] 101, 102, 103, 104, 105, 106, 107, 108: Degradation diagnosis system

[0069] 201, 202: Power conversion device. Detailed implementation manners

[0070] Hereinafter, embodiments of the present disclosure will be described.

[0071] Figure 1 It is a diagram showing a structural example of a degradation diagnosis system according to the first embodiment. Figure 1 The shown degradation diagnosis system 101 is a system for diagnosing the degradation of a semiconductor element 1 (for example, the gate oxide film or bulk of the semiconductor element 1). The degradation diagnosis system 101 includes a semiconductor element 1, a gate drive circuit 20, and a degradation diagnosis device 40. The degradation diagnosis system 101 may also include a control device 50 as a component. The gate drive circuit 20 includes, for example, a push-pull circuit 10, a gate line 22, a gate resistor 21, an acceleration capacitor circuit 30, and a detection circuit 23.

[0072] The semiconductor element 1 is a switching element driven by the gate drive circuit 20. The semiconductor element 1 has a gate, a first main terminal as a source or emitter, and a second main terminal as a drain or collector. Figure 1An example where the semiconductor element 1 is a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) having a gate G, a source S, and a drain D is shown. As other examples of the semiconductor element 1, an IGBT (Insulated Gate Bipolar Transistor) or the like can be cited.

[0073] The control device 50 is a control unit that generates one or more control signals SG for driving the push-pull circuit 10. The control device 50 can be an analog circuit composed of a combination of logic circuits, a computer having a processor and a memory, or a combination thereof. The control device 50 can be constituted by a single unit or divided into multiple units.

[0074] The push-pull circuit 10 is a drive unit that drives the gate G of the semiconductor element 1 according to the control signal SG supplied from the control device 50. The push-pull circuit 10 includes a first power supply line 15, a second power supply line 16, a power supply 13, a first switch 11, a second switch 12, and a connection point 14.

[0075] The first power supply line 15 is a positive power supply line that outputs a positive power supply voltage for maintaining the semiconductor element 1 in the on state, and is connected to the power supply 13 that generates the positive power supply voltage. The second power supply line 16 is a negative power supply line that outputs a negative power supply voltage for maintaining the semiconductor element 1 in the off state, and is connected to the power supply 13 that generates the negative power supply voltage. The second power supply line 16 can also be a ground line that outputs a ground voltage for maintaining the semiconductor element 1 in the off state.

[0076] The first switch 11 is a switching unit that switches whether to connect the gate line 22 connected to the connection point 14 to the first power supply line 15 according to the control signal SG generated by the control device 50. The first switch 11 is a circuit or element that is turned on (ON) or off (OFF) according to the control signal SG. When the first switch 11 is turned on, the gate line 22 and the first power supply line 15 are electrically connected. When the first switch 11 is turned off, the gate line 22 and the first power supply line 15 are electrically disconnected.

[0077] The second switch 12 is a switching unit that switches whether to connect the gate line 22 connected to the connection point 14 to the second power supply line 16 according to the control signal SG generated by the control device 50. The second switch 12 is a circuit or element that is turned on or off according to the control signal SG. When the second switch 12 is turned on, the gate line 22 and the second power supply line 16 are electrically connected. When the second switch 12 is turned off, the gate line 22 and the second power supply line 16 are electrically disconnected.

[0078] The push-pull circuit 10 switches the first switch 11 and the second switch 12 alternately between on and off according to the control signal SG, with a dead time during which both the first switch 11 and the second switch 12 are turned off. When the first switch 11 is on and the second switch 12 is off, since the positive power supply voltage is applied between the gate G and the source S of the semiconductor element 1, the semiconductor element 1 is turned on. When the first switch 11 is off and the second switch 12 is on, since the negative power supply voltage is applied between the gate G and the source S of the semiconductor element 1, the semiconductor element 1 is turned off.

[0079] The gate line 22 is a driving line connected between the connection point 14 of the push-pull circuit 10 and the gate G of the semiconductor element 1. The gate resistor 21 is a resistance element provided between the connection point 14 of the push-pull circuit 10 and the gate G of the semiconductor element 1, and is inserted in series into the gate line 22.

[0080] The acceleration capacitor circuit 30 is a circuit for shortening the turn-off time of the semiconductor element 1, and is connected in parallel with the gate resistor 21. The acceleration capacitor circuit 30 has a capacitor 31 connected in parallel with the gate resistor 21, a discharge resistor 32 connected in parallel with the capacitor 31, and a diode 33 inserted in series into the path of charge movement from the gate G to the capacitor 31. In this example, the anode of the diode 33 is connected to the gate line 22 between the gate resistor 21 and the gate G, and the cathode is connected to one end of each of the capacitor 31 and the discharge resistor 32.

[0081] When the second switch 12 is switched from off to on, the charge accumulated in the gate G of the semiconductor element 1 moves to the capacitor 31 via the diode 33. As a result, the voltage Vgs between the gate G and the source S of the semiconductor element 1 rapidly decreases, so the turn-off time of the semiconductor element 1 is shortened. As the voltage Vgs of the semiconductor element 1 decreases, the voltage (capacitor voltage Vc) generated across the capacitor 31 rises. When the capacitor voltage Vc is equal to the voltage Vgs, the charge accumulated in the capacitor 31 starts to discharge via the discharge resistor 32. Thus, even if the turn-off time of the semiconductor element 1 is shortened, the discharge of the capacitor 31 can start in the middle of the turn-off of the semiconductor element 1.

[0082] The detection circuit 23 detects the voltage (capacitor voltage Vc) generated across the capacitor 31 and outputs a detection value of the capacitor voltage Vc.

[0083] The degradation diagnosis device 40 uses the detection value of the capacitor voltage Vc detected by the detection circuit 23 to diagnose the degradation of the semiconductor element 1. The degradation diagnosis device 40 outputs a signal Vb representing the diagnosis result of the degradation of the semiconductor element 1.

[0084] The deterioration diagnosis device 40 can be an analog circuit composed of a combination of logic circuits, a computer having a processor and a memory, or a combination thereof. The functions of the deterioration diagnosis device 40 (the processes performed by the deterioration diagnosis device 40) are realized, for example, by a processor such as a CPU (Central Processing Unit) operating according to a program stored in the memory. The functions of the deterioration diagnosis device 40 can also be realized by an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit).

[0085] Figure 2 It is a diagram for explaining the deterioration of a semiconductor element. The horizontal axis represents the amount of charge Qg discharged from the gate G when the semiconductor element 1 is turned off. The vertical axis represents the voltage Vgs between the gate G and the source S when the semiconductor element 1 is turned off. The Qg-Vgs curve represents the gate dynamic characteristics of the semiconductor element 1.

[0086] When the semiconductor element 1 (especially the gate oxide film of the semiconductor element 1) deteriorates, the turn-on voltage Von (the voltage in the on state between the drain D and the source S) and the threshold voltage Vth of the semiconductor element 1 change. Although it also depends on the device structure, as the deterioration of the semiconductor element 1 progresses, the Qg-Vgs curve Figure 2 shifts as shown, and thus the turn-on voltage Von and the threshold voltage Vth increase. The increase in the turn-on voltage Von and the threshold voltage Vth leads to an increase in the heat generation of the semiconductor element 1. Therefore, from the viewpoint of power cycling, the deterioration of the semiconductor element 1 may be a concern.

[0087] Figure 3 It is a diagram for explaining a method for diagnosing the deterioration of a semiconductor element. Figure 3 It is a diagram in which the operation line of the capacitor voltage Vc generated across the capacitor 31 is added to the Figure 2 characteristic diagram shown. The capacitor voltage Vc is determined by the gate capacitance and gate charge of the semiconductor element 1 and the capacitance and charge of the capacitor 31. Therefore, the operation line of the capacitor 31 on the Qg-Vgs plane is represented by a straight line with the reciprocal of the capacitance of the capacitor 31 as the slope according to "Vgs = Qg / (capacitance of the capacitor 31)". In Figure 3 , the intersection points Pa and Pb of the operation line of the capacitor 31 and the Qg-Vgs curve represent the operation points where the capacitor voltage Vc is equal to the voltage Vgs.

[0088] As Figure 3As shown, the voltage value at which the capacitor voltage Vc equals the voltage Vgs is different before and after the degradation of the semiconductor element 1. The voltage value V1 is the voltage value at which the capacitor voltage Vc equals the voltage Vgs of the semiconductor element 1 before degradation. The voltage value V2 is the voltage value at which the capacitor voltage Vc equals the voltage Vgs of the semiconductor element 1 after degradation. The degradation diagnosis device 40 according to the first embodiment diagnoses the degradation of the semiconductor element 1 by observing the difference between the voltage value V1 and the voltage value V2. For example, when the value of the capacitor voltage Vc detected during the switching operation of the semiconductor element 1 (in this case, during turn-off) is greater than the voltage value V2 set as a judgment threshold, it is diagnosed that the semiconductor element 1 is degraded.

[0089] Thus, the degradation diagnosis device 40 according to the first embodiment can diagnose the degradation of the semiconductor element 1 by using the capacitor voltage Vc. By detecting the capacitor voltage Vc, the degradation diagnosis device 40 has improved noise resistance compared to the case of directly measuring the change in the voltage Vgs accompanying degradation for diagnosis. This is because the capacitor 31 can obtain the effect of filtering the voltage waveform. Furthermore, since the degradation diagnosis device 40 uses the capacitor voltage Vc detected during the switching operation of the semiconductor element 1 for the degradation diagnosis of the semiconductor element 1, it is possible to diagnose the degradation of the semiconductor element 1 without stopping the device (e.g., a power conversion device, etc.) using the semiconductor element 1.

[0090] Figure 4 It is a diagram for explaining a method of diagnosing the degradation of a semiconductor element. Figure 4 It is to Figure 3 A diagram that converts the characteristic diagram shown into a timing diagram. The horizontal axis represents time. The vertical axis represents the voltage Vgs and the capacitor voltage Vc when the semiconductor element 1 is turned off.

[0091] As Figure 4 shown, during the switching operation of the semiconductor element 1 (in this case, during turn-off), at the timing when the capacitor voltage Vc reaches the maximum value Vcp (peak value), the capacitor voltage Vc equals the voltage Vgs. Therefore, the degradation diagnosis device 40 can diagnose the degradation of the semiconductor element 1 by using the maximum value Vcp of the capacitor voltage Vc. For example, when the maximum value Vcp of the capacitor voltage Vc detected during the switching operation of the semiconductor element 1 exceeds the voltage value V2 (refer to Figure 3 ) set as a determination threshold, the degradation diagnosis device 40 diagnoses that the semiconductor element 1 is degraded.

[0092] By holding the capacitor voltage Vc at the peak, it is possible to easily detect the maximum value Vcp of the capacitor voltage Vc during the switching operation of the semiconductor element 1. Next, a degradation diagnosis system having a function of holding the peak value of the capacitor voltage Vc will be described.

[0093] Figure 5 This is a diagram showing a structural example of the degradation diagnosis system according to the second embodiment. In the second embodiment, the description of the same structure, operation, and effects as those in the above embodiment is omitted by reference to the above description. Figure 5 The degradation diagnosis system 102 according to the second embodiment shown is different from the above degradation diagnosis system 101 in that it has a peak holding function for the peak value of the capacitor voltage Vc.

[0094] The degradation diagnosis system 102 has a peak holding unit 41, which has the function of holding the maximum value Vcp of the capacitor voltage Vc during a fixed period T. By the function of the peak holding unit 41, the maximum value Vcp of the capacitor voltage Vc during the fixed period T can be sampled with high precision. The peak holding unit 41 can be constituted in the gate drive circuit 20 or in the degradation diagnosis device 40.

[0095] The peak holding unit 41 samples the maximum value Vcp of the capacitor voltage Vc during the fixed period T, for example, according to a reset signal SR synchronized with the operation cycle of the semiconductor element 1. Thus, the degradation diagnosis device 40 can obtain the maximum value Vcp of the capacitor voltage Vc during the fixed period T for each operation cycle of the semiconductor element 1, and therefore can update the degradation diagnosis result of the semiconductor element 1 for each operation cycle of the semiconductor element 1.

[0096] The reset signal SR is generated, for example, by a control device 50 that controls the operation of the semiconductor element 1. However, the reset signal SR can also be a signal generated by the gate drive circuit 20 based on a control signal SG.

[0097] Figure 6 This is a timing diagram for explaining a first example of a method for sampling the maximum value of the capacitor voltage during a fixed period according to the operation cycle of the semiconductor element. The peak holding unit 41 samples the maximum value Vcp of the capacitor voltage Vc during the fixed period T according to a reset signal SR synchronized with the operation cycle of the semiconductor element 1.

[0098] Figure 6 The upper part of shows a first example of the operation cycle of the semiconductor element 1. As an example of a device having the semiconductor element 1, there is a power conversion device that operates a load such as a motor driven by the semiconductor element 1 in an operation cycle that repeats in the order of acceleration, constant speed, deceleration, and stop. This power conversion device, for example, has the structure shown in Figure 5 shown. In Figure 6In this case, the control device 50 outputs a control signal SG for turning off the semiconductor element 1 and a reset signal SR for sampling and resetting the maximum value Vcp in synchronization with the timing for stopping a load such as a motor. Each time the reset signal SR is input, the peak holding unit 41 samples the maximum value Vcp of the capacitor voltage Vc detected during the turn-off of the semiconductor element 1. As a result, the degradation diagnosis device 40 obtains the maximum value Vcp of the capacitor voltage Vc during the fixed period T each time the semiconductor element 1 stops, and updates the degradation diagnosis result of the semiconductor element 1 each time the semiconductor element 1 stops.

[0099] Figure 7 FIG. is a timing chart for explaining a second example of a method of sampling the maximum value of the capacitor voltage during a fixed period according to the operation cycle of the semiconductor element. The peak holding unit 41 samples the maximum value Vcp of the capacitor voltage Vc during the fixed period T according to the reset signal SR synchronized with the operation cycle of the semiconductor element 1.

[0100] Figure 7 The upper part of FIG. shows a second example of the operation cycle of the semiconductor element 1. As an example of a device including the semiconductor element 1, there is a CVCF (Constant Voltage Constant Frequency) power supply that supplies a voltage with a constant frequency to a load. The CVCF power supply is an example of a power conversion device and includes, for example, Figure 5 the structure shown in FIG. In Figure 7 this case, the control device 50 outputs a reset signal SR for sampling and resetting the maximum value Vcp in synchronization with the timing at which the output voltage or output current of a constant frequency supplied to the load crosses zero. Each time the reset signal SR is input, the peak holding unit 41 samples the maximum value Vcp of the capacitor voltage Vc detected during the turn-off of the semiconductor element 1. As a result, the degradation diagnosis device 40 obtains the maximum value Vcp of the capacitor voltage Vc during the fixed period T each time the output voltage or output current of the semiconductor element 1 crosses zero, and updates the degradation diagnosis result of the semiconductor element 1 each time the output voltage or output current of the semiconductor element 1 crosses zero.

[0101] Figure 8 FIG. is a timing chart for explaining a third example of a method of sampling the maximum value of the capacitor voltage during a fixed period according to the operation cycle of the semiconductor element. The peak holding unit 41 samples the maximum value Vcp of the capacitor voltage Vc during the fixed period T according to the reset signal SR synchronized with the operation cycle of the semiconductor element 1.

[0102] Figure 8The upper part shows a third example of the operation cycle of the semiconductor element 1, specifically showing the carrier period (the period of the carrier C) of the gate drive of the semiconductor element 1. The carrier period represents the pulse width modulation period used to drive the semiconductor element 1 by pulse width modulation. The control device 50 outputs a reset signal SR for sampling and resetting the maximum value Vcp synchronously with the carrier period. Whenever the reset signal SR is input, the peak holding unit 41 samples the maximum value Vcp of the capacitor voltage Vc detected during the turn-off of the semiconductor element 1. Thus, the deterioration diagnosis device 40 obtains the maximum value Vcp of the capacitor voltage Vc during the fixed period T for each carrier period of the semiconductor element 1, and updates the deterioration diagnosis result of the semiconductor element 1 for each carrier period of the semiconductor element 1.

[0103] The control device 50 turns off or turns on the semiconductor element 1 by comparing the carrier C with the command value A. For example, when the carrier C is greater than the command value A, the control device 50 outputs a gate disconnection command for the semiconductor element 1. When the control device 50 outputs the reset signal SR at the timing of the maximum value or the minimum value of the carrier C (the maximum value in the illustrated example), reliable reset can be performed in the gate-disconnected state of the semiconductor element 1.

[0104] Sampling of the maximum value Vcp can be performed until the turn-off of the semiconductor element 1 is completed and the reset signal SR is input. Therefore, the sampling timing of the maximum value Vcp does not have to be the same as the timing when the reset signal SR is input.

[0105] Completion of the turn-off of the semiconductor element 1 can be determined by the voltage applied between the gate G and the source S or between the drain D and the source S of the semiconductor element 1, the current flowing through the drain D, or the time elapsed since the turn-off signal was input to the semiconductor element 1. Completion of the turn-off of the semiconductor element 1 can also be determined by this information of the semiconductor element connected in series with the semiconductor element 1 (not shown).

[0106] Figure 9 is a diagram showing Figure 8 a structural example embodying the method shown. In Figure 9 the description of the same structure, operation, and effects as those in the above embodiment is omitted by reference to the above description. Figure 9 The deterioration diagnosis system 103 according to the third embodiment shown is different from the above deterioration diagnosis system 101 or deterioration diagnosis system 102 in that it includes a reset circuit 34.

[0107] The reset circuit 34 has a reset switch connected in parallel with the capacitor 31. The reset circuit 34 discharges the charge of the capacitor 31 by turning on the reset switch according to a reset signal SR synchronized with the operation cycle of the semiconductor element 1. Thus, even without the discharge resistor 32, the capacitor 31 can be discharged for each carrier cycle.

[0108] When the second switch 12 is switched from off to on, the charge accumulated in the gate G of the semiconductor element 1 moves to the capacitor 31 via the diode 33 instead of moving to the reset circuit 34 in which the reset switch is in the off state. Thus, the voltage Vgs between the gate G and source S of the semiconductor element 1 rapidly decreases, and therefore the turn-off time of the semiconductor element 1 is shortened. As the voltage Vgs of the semiconductor element 1 decreases, the voltage (capacitor voltage Vc) generated across the capacitor 31 rises. When the reset signal SR synchronized with the operation cycle of the semiconductor element 1 is input, the reset circuit 34 switches the reset switch from off to on. When the reset switch is on, the charge accumulated in the capacitor 31 starts to discharge via the on-state reset switch. Thus, even if the turn-off time of the semiconductor element 1 is shortened, the discharge of the capacitor 31 can be started in the middle of the turn-off of the semiconductor element 1.

[0109] Figure 10 FIG. is a diagram showing a structural example of the degradation diagnosis system according to the fourth embodiment. In the fourth embodiment, the description of the same structure, operation, and effects as those in the above embodiment is omitted by reference to the above description. Figure 10 The degradation diagnosis system 104 according to the fourth embodiment shown diagnoses the degradation of the semiconductor element 1 using the capacitor voltage Vc and the information of the semiconductor element 1 in the degradation diagnosis device 40, which is different from the above degradation diagnosis systems 101 and the like.

[0110] As an example of the information of the semiconductor element 1, the voltage Vds between the drain D and source S of the semiconductor element 1, the current Id flowing between the drain D and source S of the semiconductor element 1, the temperature Th of the semiconductor element 1, etc. can be cited.

[0111] The information of the semiconductor element 1 such as the voltage Vds, the current Id, or the temperature Th is measured by known means such as a sensor. The degradation diagnosis device 40 may also obtain the information of the semiconductor element 1 from the control device 50, the gate drive circuit 20, or other devices.

[0112] The Qg-Vgs curve (see Figure 2 ) varies according to the voltage Vds, the current Id, or the temperature Th. Referring to Figure 2 , the larger the voltage Vds or the current Id, or the lower the temperature Th, the Qg-Vgs curve is as Figure 2The more it is shifted as shown, the higher the turn-on voltage Von and the threshold voltage Vth become. Therefore, the deterioration diagnosis device 40 uses the information of the semiconductor element 1 for the deterioration diagnosis of the semiconductor element 1, thereby improving the accuracy of the deterioration diagnosis of the semiconductor element 1.

[0113] The deterioration diagnosis device 40 can also diagnose the deterioration of the semiconductor element 1 when the information of the semiconductor element 1 such as the voltage Vds, the current Id, or the temperature Th satisfies a given condition. Thereby, the timing for diagnosing the deterioration of the semiconductor element 1 is limited to the case where the information of the semiconductor element 1 such as the voltage Vds, the current Id, or the temperature Th satisfies a given condition. Therefore, for example, the frequency of diagnosing the deterioration of the semiconductor element 1 is suppressed and does not become excessive.

[0114] As an example of the case where a given condition is satisfied, a case where at least one of a first condition that the voltage Vds is higher than a given voltage threshold, a second condition that the current Id is higher than a given current threshold, and a third condition that the temperature is lower than a given temperature threshold holds can be cited.

[0115] Figure 11 FIG. is a diagram showing a structural example of the deterioration diagnosis system according to the fifth embodiment. In the fifth embodiment, the description of the same structure, operation, and effect as those in the above embodiment is omitted by reference to the above description. Figure 11 The deterioration diagnosis system 105 according to the fifth embodiment shown is different from the above-described deterioration diagnosis system 101 etc. in that the deterioration diagnosis device 40 diagnoses the deterioration of the semiconductor element 1 by comparing the capacitor voltage Vc with a threshold value set according to the information of the semiconductor element 1.

[0116] The deterioration diagnosis device 40 sets a threshold value Va corresponding to the information of the semiconductor element 1 obtained from the control device 50 etc. based on the correspondence relationship between the information of the semiconductor element 1 such as the voltage Vds, the current Id, or the temperature Th and the threshold value Va. Thereby, the deterioration diagnosis device 40 can set a threshold value Va suitable for the obtained information of the semiconductor element 1. The threshold value Va is a determination threshold value for the deterioration diagnosis of the semiconductor element 1 and corresponds to, for example, a voltage value V2 (see Figure 3 ). The correspondence relationship between the information of the semiconductor element 1 and the threshold value Va is determined by a map or an arithmetic expression. The deterioration diagnosis device 40 diagnoses the deterioration of the semiconductor element 1 by comparing the maximum value Vcp of the capacitor voltage Vc with the threshold value Va using the comparison unit 42. For example, when the maximum value Vcp is greater than the threshold value Va, the deterioration diagnosis device 40 diagnoses that the semiconductor element 1 is deteriorated.

[0117] Figure 12This is a diagram showing a structural example of the degradation diagnosis system according to the sixth embodiment. In the sixth embodiment, the description of the same structures, operations, and effects as those in the above embodiments is omitted by reference to the above description. Figure 12 The degradation diagnosis system 106 of the sixth embodiment shown is different from the above degradation diagnosis system 105 in that the degradation diagnosis device 40 diagnoses the degradation of the semiconductor element 1 by comparing the capacitor voltage Vc with a fixed threshold value Va.

[0118] The degradation diagnosis device 40 uses the information of the semiconductor element 1 (such as the voltage Vds, current Id, or temperature Th, etc.) when the maximum value Vcp of the capacitor voltage Vc is greater than the fixed threshold value Va, and diagnoses the degradation of the semiconductor element 1 through the degradation diagnosis unit 43. Since the degradation diagnosis unit 43 for diagnosing degradation does not read the detection value of the capacitor voltage Vc itself, the number of AD converters for detecting the capacitor voltage Vc can be reduced.

[0119] The threshold value Va can be stored in the memory in advance, or can be set as a voltage source having the threshold value Va. The threshold value Va is determined through experiments or data tables implemented in advance.

[0120] The degradation diagnosis device 40 can also diagnose the degradation of the semiconductor element 1 when the information of the semiconductor element 1 satisfies a given condition and the capacitor voltage Vc is greater than the fixed threshold value Va. For example, the degradation diagnosis device 40 compares the maximum value Vcp of the capacitor voltage Vc with the threshold value Va through the comparison unit 42, and when the maximum value Vcp is greater than the threshold value Va, makes the determination signal Ve effective. The degradation diagnosis unit 43 can diagnose that the semiconductor element 1 is degraded when the information of the semiconductor element 1 such as the voltage Vds, current Id, or temperature Th satisfies the above given condition and the determination signal Ve is effective. The degradation diagnosis unit 43 can also receive the case where the determination signal Ve is effective, obtain the information of the semiconductor element 1 such as the voltage Vds, current Id, or temperature Th, and diagnose that the semiconductor element 1 is degraded when these information satisfy the above given condition.

[0121] Figure 13 This is a diagram showing a first example of the application of the degradation diagnosis system according to the present embodiment to a power conversion device. Figure 13The illustrated deterioration diagnosis system 107 can be any one of a plurality of deterioration diagnosis systems of the present disclosure. The power conversion device 201 includes an inverter circuit 70 that converts DC power input from a DC power source 60 into AC power and supplies it to a load M1 such as a motor. A current sensor 71 detects an AC current flowing between the inverter circuit 70 and the load M1, and outputs a detection value of the AC current to a control device 50 and a deterioration diagnosis device 40. The control device 50 generates a control signal SG for driving the inverter circuit 70 using the detection value of the AC current detected by the current sensor 71.

[0122] The inverter circuit 70 is a bridge circuit composed of a plurality of semiconductor elements u, v, w, x, y, z connected between a first DC bus 61 and a second DC bus 62. The inverter circuit 70 converts the DC voltage input from the DC power source 60 into an AC voltage by the switching operation of the plurality of semiconductor elements u, v, w, x, y, z, and drives a load M1 such as a three-phase AC motor.

[0123] The control device 50 generates a plurality of control signals SG for driving the respective gates Gu, Gv, Gw, Gx, Gy, Gz of the plurality of semiconductor elements u, v, w, x, y, z so that the three-phase AC generated by the inverter circuit 70 flows to the load M1.

[0124] The semiconductor elements u, v, w, x, y, z are each an example of the semiconductor element 1 described above. Figure 13 An example is shown in which the semiconductor element 1 is an IGBT having a gate G, an emitter, and a collector.

[0125] The deterioration diagnosis device 40 obtains a capacitor voltage Vc detected by an insulated AD converter via an insulating section 63 that insulates a high potential section from a low potential section. Although not shown, the deterioration diagnosis device 40 obtains information on the semiconductor element 1 such as a voltage Vds, a current Id, or a temperature Th from a low potential section such as the control device 50.

[0126] The deterioration diagnosis device 40 is provided in an external device having a relatively high computing power (such as the control device 50 or an external server not shown). By providing the deterioration diagnosis device 40 in an external device having a high computing power, it is possible to accurately diagnose the deterioration of the semiconductor element.

[0127] The deterioration diagnosis device 40 diagnoses the deterioration of some or all of the plurality of semiconductor elements u, v, w, x, y, and z. In this example, the deterioration of the semiconductor element u is diagnosed as a representative. The deterioration diagnosis device 40 sends the diagnosis results of the deterioration of some or all of the plurality of semiconductor elements u, v, w, x, y, and z to the user interface 72. The user interface 72 notifies the received diagnosis results to the user through at least one of a display screen, a lamp, and a speaker as a notification unit. Thus, the user can recognize the diagnosis results.

[0128] Figure 14 FIG. is a diagram showing a second example of the application of the deterioration diagnosis system according to the present embodiment to the power conversion device. Figure 14 The illustrated deterioration diagnosis system 108 may be any one of the plurality of deterioration diagnosis systems of the present disclosure. Figure 14 The structure related to the power conversion operation of the illustrated power conversion device 202 may be the same as that of the above-described power conversion device 201. In addition, in the present embodiment, information of the semiconductor element 1 such as the voltage Vds, the current Id, or the temperature Th may be obtained from the high potential portion.

[0129] The deterioration diagnosis device 40 is provided in the power conversion device 202 (for example, a gate drive circuit). The deterioration diagnosis device 40 sends the diagnosis results of the semiconductor element to the user interface 72 located outside the power conversion device 202 in a wired or wireless manner. The diagnosis results sent from the deterioration diagnosis device 40 of the gate drive circuit provided in the high potential portion to the user interface 72 provided in the low potential portion are information with relatively little amount of information (for example, the presence or absence of deterioration of the semiconductor element or the level of deterioration). Therefore, even without using a high-resolution device such as an isolation type AD converter, the deterioration diagnosis device 40 can send the diagnosis results to the user interface 72 via the insulation portion 63.

[0130] As described above, the embodiments have been described, but the above embodiments are presented as examples, and the present invention is not limited to the above embodiments. The above embodiments can be implemented in various other ways, and various combinations, omissions, substitutions, changes, etc. can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and its equivalents.

[0131] For example, the gate resistor 21 can also be provided within the push-pull circuit 10. The gate resistor 21 provided within the push-pull circuit 10 can be a resistor (turn-off gate resistor) inserted in series with the second switch 12 in the signal path between the connection point 14 and the second power supply line 16. In this case, the acceleration capacitor circuit 30 is connected in parallel with the turn-off gate resistor. The anode of the diode 33 in the acceleration capacitor circuit 30 is connected to the gate drive line between the turn-off gate resistor and the gate G, and the cathode is connected to one end of each of the capacitor 31 and the discharge resistor 32.

[0132] The functions and effects in the manner where the gate resistor 21 is a turn-off gate resistor are the same as the functions and effects in the above-described embodiment where the gate resistor 21 is inserted in series between the connection point 14 and the gate G, and thus are omitted by reference to the above description.

[0133] The gate resistor 21 provided within the push-pull circuit 10 can also be a resistor (turn-on gate resistor) inserted in series with the first switch 11 in the signal path between the connection point 14 and the first power supply line 15. In this case, the acceleration capacitor circuit 30 is connected in parallel with the turn-on gate resistor. The cathode of the diode 33 within the acceleration capacitor circuit 30 is connected to the gate drive line between the turn-on gate resistor and the gate G, and the anode is connected to one end of each of the capacitor 31 and the discharge resistor 32.

[0134] In the manner where the gate resistor 21 is a turn-on gate resistor, when the first switch 11 is switched from off to on, the charge of the first power supply line 15 moves to the gate G of the semiconductor element 1 via the diode 33. As a result, the voltage Vgs between the gate G and the source S of the semiconductor element 1 rapidly rises, so the turn-on time of the semiconductor element 1 is shortened. As the voltage Vgs of the semiconductor element 1 rises, the voltage (capacitor voltage Vc) generated across the capacitor 31 rises. When the capacitor voltage Vc becomes equal to the voltage Vgs, the charge stored in the capacitor 31 starts to discharge via the discharge resistor 32. Thus, even if the turn-on time of the semiconductor element 1 is shortened, the discharge of the capacitor 31 can start in the middle of the turn-on of the semiconductor element 1.

[0135] Even in the manner where the gate resistor 21 is a turn-on gate resistor, it is the same as the Figure 3 case shown. The voltage value when the capacitor voltage Vc becomes equal to the voltage Vgs is different before and after the degradation of the semiconductor element 1. The degradation diagnosis device 40 diagnoses the degradation of the semiconductor element 1 by observing the difference between the voltage value V1 and the voltage value V2. For example, when the value of the capacitor voltage Vc detected during the switching operation of the semiconductor element 1 (in this example, during turn-on) is greater than the voltage value V2 set as a determination threshold, the degradation diagnosis device 40 diagnoses that the semiconductor element 1 is degraded.

Claims

1. A degradation diagnosis system comprising: A semiconductor element having a gate, a first main terminal as source or emitter and a second main terminal as drain or collector; Push-pull circuit; A gate resistor, which is arranged in the push-pull circuit or between the push-pull circuit and the gate; a capacitor connected in parallel with the gate resistor; as well as A degradation diagnosis device diagnoses degradation of the semiconductor element using a capacitor voltage generated across the capacitor.

2. The degradation diagnosis system according to claim 1, wherein: The degradation diagnosis device diagnoses degradation of the semiconductor element using a voltage value when the capacitor voltage is equal to a voltage between the gate and the first main terminal.

3. The degradation diagnosis system according to claim 2, wherein: The voltage value is the maximum value of the capacitor voltage.

4. The degradation diagnosis system according to claim 3, wherein: The degradation diagnosis system includes a peak holding unit that holds a maximum value of the capacitor voltage during a fixed period. The voltage value is a maximum value held by the peak holding unit.

5. The degradation diagnosis system according to claim 4, wherein: The peak holding unit samples the maximum value according to an operation cycle of the semiconductor element.

6. The degradation diagnosis system according to claim 5, wherein: The operation cycle is a zero-crossing cycle of the output voltage or the output current of the semiconductor element.

7. The degradation diagnosis system according to claim 5, wherein: The operation cycle is a carrier cycle of the semiconductor element.

8. The degradation diagnosis system according to any one of claims 1 to 7, wherein: The degradation diagnosis device diagnoses degradation of the semiconductor element using the capacitor voltage and information of the semiconductor element.

9. The degradation diagnosis system according to claim 8, wherein: The degradation diagnosis device diagnoses degradation of the semiconductor element when information on the semiconductor element satisfies a given condition.

10. The degradation diagnosis system according to claim 8, wherein: The degradation diagnosis device diagnoses degradation of the semiconductor element by comparing the capacitor voltage with a threshold value set based on information on the semiconductor element.

11. The degradation diagnosis system according to claim 8, wherein: The degradation diagnosis device diagnoses degradation of the semiconductor element using information of the semiconductor element when the capacitor voltage is larger than a fixed threshold value.

12. The degradation diagnosis system according to claim 8, wherein: The degradation diagnosis device diagnoses degradation of the semiconductor element when information of the semiconductor element satisfies a given condition and the capacitor voltage is greater than a fixed threshold value.

13. A degradation diagnosis method, wherein: Deterioration of the semiconductor element is diagnosed using a capacitor voltage generated across a capacitor connected in parallel with a gate resistor provided in a push-pull circuit or provided between the push-pull circuit and a gate of the semiconductor element.

14. A power conversion device comprising: A semiconductor element having a gate, a first main terminal as source or emitter and a second main terminal as drain or collector; Push-pull circuit; A gate resistor, which is arranged in the push-pull circuit or between the push-pull circuit and the gate; a capacitor connected in parallel with the gate resistor; a degradation diagnosis device for diagnosing degradation of the semiconductor element using a capacitor voltage generated across the capacitor; as well as A peak holding unit holds a maximum value of the capacitor voltage during a fixed period according to an operation cycle of the semiconductor element.

15. The power conversion device according to claim 14, wherein: The operation cycle is a zero-crossing cycle of the output voltage or the output current of the semiconductor element.

Images