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

Abstract

To provide a deterioration diagnosis system for diagnosing deterioration of a semiconductor element, and a power conversion device.SOLUTION: A deterioration diagnosis system 101 includes: a semiconductor element 1 having a gate G, a first main terminal S which is a source or emitter, and a second main terminal D which is a drain or collector; a push-pull circuit 10; a gate drive circuit having a gate resistor 21 provided in the push-pull circuit or between the push-pull circuit and the gate, and a capacitor 31 connected in parallel with the gate resistor; and a deterioration diagnosis device 40 that diagnoses deterioration of the semiconductor element 1 by using a capacitor voltage Vc generated between both ends of the capacitor 31.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

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

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the conventional technology, it is not possible to diagnose the degradation of semiconductor elements.

[0005] The present disclosure provides a degradation diagnosis system, a degradation diagnosis method, and a power conversion device capable of diagnosing the degradation of semiconductor elements.

Means for Solving the Problems

[0006] In one aspect, the present disclosure provides a semiconductor element having a gate, a first main terminal that is a source or an emitter, and a second main terminal that is a drain or a collector; a push-pull circuit; a gate resistor provided 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 that diagnoses the degradation of the semiconductor element using the capacitor voltage generated across the capacitor, and provides a degradation diagnosis system.

[0007] The present disclosure, as another aspect, provides a deterioration diagnosis method for diagnosing the deterioration of a semiconductor element by using a capacitor voltage generated across both ends of 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.

[0008] The present disclosure, as another aspect, a semiconductor element having a gate, a first main terminal that is a source or an emitter, and a second main terminal that is a drain or a collector, a push-pull circuit, a gate resistor provided in the push-pull circuit or between the push-pull circuit and the gate, a capacitor connected in parallel with the gate resistor, a deterioration diagnosis device for diagnosing the deterioration of the semiconductor element by using the capacitor voltage generated across both ends of the capacitor, and a peak hold unit that holds the maximum value of the capacitor voltage over a certain period according to the operation cycle of the semiconductor element, and provides a power conversion device.

Advantages of the Invention

[0009] According to the present disclosure, the deterioration of the semiconductor element can be diagnosed.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

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Figure 8

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Figure 10

Figure 11

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Figure 14

Mode for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present disclosure will be described.

[0012] FIG. 1 is a diagram showing a configuration example of a deterioration diagnosis system according to the first embodiment. The deterioration diagnosis system 101 shown in FIG. 1 is a system for diagnosing the deterioration of a semiconductor element 1 (for example, the gate oxide film or the bulk of the semiconductor element 1). The deterioration diagnosis system 101 includes a semiconductor element 1, a gate drive circuit 20, and a deterioration diagnosis device 40. The deterioration diagnosis system 101 may 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, a speed-up capacitor circuit 30, and a detection circuit 23.

[0013] 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 that is a source or an emitter, and a second main terminal that is a drain or a collector. FIG. 1 illustrates the case 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. Other examples of the semiconductor element 1 include an IGBT (Insulated Gate Bipolar Transistor).

[0014] 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 may be an analog circuit configured by a combination of logic circuits, a computer having a processor and a memory, or a combination thereof. The control device 50 may be configured by one unit or divided into a plurality of units.

[0015] 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 has 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.

[0016] The first power line 15 is a positive power line that outputs a positive power supply voltage for maintaining the semiconductor element 1 in the on state, and is connected to a power supply 13 that generates the positive power supply voltage. The second power line 16 is a negative power line that outputs a negative power supply voltage for maintaining the semiconductor element 1 in the off state, and is connected to a power supply 13 that generates the negative power supply voltage. The second power line 16 may be a ground line that outputs a ground voltage for maintaining the semiconductor element 1 in the off state.

[0017] 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 line 15 according to a control signal SG generated by the control device 50. The first switch 11 is a circuit or element that turns on or off according to the control signal SG. When the first switch 11 is turned on, the gate line 22 and the first power line 15 are electrically connected. When the first switch 11 is turned off, the gate line 22 and the first power line 15 are electrically disconnected.

[0018] 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 line 16 according to a control signal SG generated by the control device 50. The second switch 12 is a circuit or element that turns 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 line 16 are electrically connected, and when the second switch 12 is turned off, the gate line 22 and the second power line 16 are electrically disconnected.

[0019] The push-pull circuit 10 switches the first switch 11 and the second switch 12 to be alternately turned on or off with a dead time for turning off both the first switch 11 and the second switch 12 according to the control signal SG. When the first switch 11 is on and the second switch 12 is off, a positive power supply voltage is applied between the gate G and the source S of the semiconductor element 1, so the semiconductor element 1 is turned on. When the first switch 11 is off and the second switch 12 is on, a negative power supply voltage is applied between the gate G and the source S of the semiconductor element 1, so the semiconductor element 1 is turned off.

[0020] The gate line 22 is a drive line connecting 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 resistor 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 with the gate line 22.

[0021] The speed-up 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 speed-up capacitor circuit 30 includes 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 in the charge transfer path from the gate G to the capacitor 31. In this example, the diode 33 has an anode connected to the gate line 22 between the gate resistor 21 and the gate G, and a cathode connected to one end of each of the capacitor 31 and the discharge resistor 32.

[0022] When the second switch 12 switches 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 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 increases. When the capacitor voltage Vc becomes 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 be started during the turn-off of the semiconductor element 1.

[0023] The detection circuit 23 detects the voltage (capacitor voltage Vc) generated across the capacitor 31 and outputs the detected value of the capacitor voltage Vc.

[0024] The deterioration diagnosis device 40 diagnoses the deterioration of the semiconductor element 1 by using the detected value of the capacitor voltage Vc detected by the detection circuit 23. The deterioration diagnosis device 40 outputs a signal Vb representing the diagnosis result of the deterioration of the semiconductor element 1.

[0025] The deterioration diagnosis device 40 may be an analog circuit composed of a combination of logic circuits, a computer having a processor and a memory, or a combination thereof. The function of the deterioration diagnosis device 40 (the process performed by the deterioration diagnosis device 40) is realized, for example, by a processor such as a CPU (Central Processing Unit) operating according to a program stored in the memory. The function of the deterioration diagnosis device 40 may be realized by an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit).

[0026] FIG. 2 is a diagram for explaining the deterioration of the semiconductor element. The horizontal axis represents the amount of charge Qg discharged from the gate G at the turn-off of the semiconductor element 1. The vertical axis represents the voltage Vgs between the gate G and the source S at the turn-off of the semiconductor element 1. The Qg-Vgs curve represents the gate dynamic characteristics of the semiconductor element 1.

[0027] When the semiconductor element 1 (especially the gate oxide film of the semiconductor element 1) deteriorates, the 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 fluctuate. Although it depends on the device structure, as the deterioration of the semiconductor element 1 progresses, the Qg-Vgs curve shifts as shown in FIG. 2, so the on-voltage Von and the threshold voltage Vth increase. The increase in the on-voltage Von and the threshold voltage Vth causes an increase in the heat generation amount of the semiconductor element 1. Therefore, the deterioration of the semiconductor element 1 can be a concern from the viewpoint of power cycling.

[0028] FIG. 3 is a diagram for explaining a method for diagnosing degradation of a semiconductor element. FIG. 3 is a diagram in which an operation line of a capacitor voltage Vc generated at both ends of the capacitor 31 is added to the characteristic diagram shown in FIG. 2. 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 having a reciprocal of the capacitance of the capacitor 31 as a slope according to "Vgs = Qg / (capacitance of the capacitor 31)". In FIG. 3, intersection points Pa and Pb between the operation line of the capacitor 31 and the Qg-Vgs curve represent operation points where the capacitor voltage Vc becomes equal to the voltage Vgs.

[0029] As shown in FIG. 3, the voltage value when the capacitor voltage Vc becomes equal to the voltage Vgs is different before and after degradation of the semiconductor element 1. The voltage value V1 is the voltage value when the capacitor voltage Vc becomes equal to the voltage Vgs of the semiconductor element 1 before degradation. The voltage value V2 is the voltage value when the capacitor voltage Vc becomes equal to the voltage Vgs of the semiconductor element 1 after degradation. The degradation diagnosis device 40 according to the first embodiment diagnoses 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 switch operation of the semiconductor element 1 (in this example, during turn-off) is greater than the voltage value V2 set as a determination threshold value, the degradation diagnosis device 40 diagnoses that the semiconductor element 1 is degraded.

[0030] As described above, the degradation diagnosis device 40 according to the first embodiment can diagnose degradation of the semiconductor element 1 by using 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 due to degradation by detecting the capacitor voltage Vc to diagnose degradation. This is because the effect of filtering the voltage waveform by the capacitor 31 is obtained. Further, since the degradation diagnosis device 40 uses the capacitor voltage Vc detected during the switch operation of the semiconductor element 1 for diagnosing degradation of the semiconductor element 1, degradation of the semiconductor element 1 can be diagnosed without stopping the device using the semiconductor element 1 (for example, a power conversion device, etc.).

[0031] FIG. 4 is a diagram for explaining a method for diagnosing deterioration of a semiconductor element. FIG. 4 is a diagram obtained by converting the characteristic diagram shown in FIG. 3 into a timing chart. The horizontal axis represents time. The vertical axis represents the voltage Vgs at the turn-off of the semiconductor element 1 and the capacitor voltage Vc.

[0032] As shown in FIG. 4, during the switch operation of the semiconductor element 1 (in this example, during turn-off), at the timing when the capacitor voltage Vc reaches the maximum value Vcp (peak value), the capacitor voltage Vc becomes equal to the voltage Vgs. Therefore, the deterioration diagnosis device 40 can diagnose the deterioration 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 switch operation of the semiconductor element 1 exceeds the voltage value V2 (see FIG. 3) set as the determination threshold value, the deterioration diagnosis device 40 diagnoses that the semiconductor element 1 is deteriorated.

[0033] The maximum value Vcp of the capacitor voltage Vc during the switch operation of the semiconductor element 1 is easily detected by peak-holding the capacitor voltage Vc. Next, a deterioration diagnosis system having a peak-holding function for the capacitor voltage Vc will be described.

[0034] FIG. 5 is a diagram showing a configuration example of a deterioration diagnosis system according to the second embodiment. In the second embodiment, the description of the same configuration, operation, and effects as those in the above-described embodiment is omitted by referring to the above description. The deterioration diagnosis system 102 according to the second embodiment shown in FIG. 5 is different from the above-described deterioration diagnosis system 101 in that it has a peak-holding unit 41 having a function of holding the maximum value Vcp of the capacitor voltage Vc for a certain period T.

[0035] The deterioration diagnosis system 102 has a peak-holding unit 41 having a function of holding the maximum value Vcp of the capacitor voltage Vc for a certain period T. By the function of the peak-holding unit 41, the maximum value Vcp of the capacitor voltage Vc for a certain period T can be accurately sampled. The peak-holding unit 41 may be configured in the gate drive circuit 20 or in the deterioration diagnosis device 40.

[0036] The peak hold unit 41 samples the maximum value Vcp of the capacitor voltage Vc during a certain period T in synchronization with, for example, a reset signal SR synchronized with the operation cycle of the semiconductor element 1. As a result, the deterioration diagnosis device 40 can acquire the maximum value Vcp of the capacitor voltage Vc during a certain period T for each operation cycle of the semiconductor element 1, so that the deterioration diagnosis result of the semiconductor element 1 can be updated for each operation cycle of the semiconductor element 1.

[0037] 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 may also be a signal generated by the gate drive circuit 20 based on the control signal SG.

[0038] FIG. 6 is a timing chart for explaining a first example of a method of sampling the maximum value of the capacitor voltage during a certain period in accordance with the operation cycle of the semiconductor element. The peak hold unit 41 samples the maximum value Vcp of the capacitor voltage Vc during a certain period T in synchronization with a reset signal SR synchronized with the operation cycle of the semiconductor element 1.

[0039] The upper part of FIG. 6 shows a first example of the operation cycle of the semiconductor element 1. As an example of a device including 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. The power conversion device has, for example, the configuration shown in FIG. 5. In FIG. 6, 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 of stopping the load such as the motor. The peak hold unit 41 samples the maximum value Vcp of the capacitor voltage Vc detected during the turn-off of the semiconductor element 1 every time the reset signal SR is input. As a result, the deterioration diagnosis device 40 acquires the maximum value Vcp of the capacitor voltage Vc during a certain period T for each stop of the semiconductor element 1, and updates the deterioration diagnosis result of the semiconductor element 1 for each stop of the semiconductor element 1.

[0040] FIG. 7 is a timing chart for explaining a second example of a method of sampling the maximum value of the capacitor voltage during a certain period according to the operation cycle of the semiconductor element. The peak hold unit 41 samples the maximum value Vcp of the capacitor voltage Vc during a certain period T in accordance with a reset signal SR synchronized with the operation cycle of the semiconductor element 1.

[0041] The upper part of FIG. 7 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 of a certain frequency to a load. The CVCF power supply is an example of a power conversion device and has, for example, the configuration shown in FIG. 5. In FIG. 7, the control device 50 outputs a reset signal SR that samples and resets the maximum value Vcp in synchronization with the timing at which the output voltage or output current of a certain frequency supplied to the load crosses zero. The peak hold unit 41 samples the maximum value Vcp of the capacitor voltage Vc detected during the turn-off of the semiconductor element 1 every time the reset signal SR is input. Thereby, the deterioration diagnosis device 40 acquires the maximum value Vcp of the capacitor voltage Vc during a certain period T every time the output voltage or output current of the semiconductor element 1 crosses zero, and updates the deterioration diagnosis result of the semiconductor element 1 every time the output voltage or output current of the semiconductor element 1 crosses zero.

[0042] FIG. 8 is a timing chart for explaining a third example of a method of sampling the maximum value of the capacitor voltage during a certain period according to the operation cycle of the semiconductor element. The peak hold unit 41 samples the maximum value Vcp of the capacitor voltage Vc during a certain period T in accordance with a reset signal SR synchronized with the operation cycle of the semiconductor element 1.

[0043] The upper part of FIG. 8 shows a third example of the operation cycle of the semiconductor element 1. Specifically, it shows the carrier cycle (the cycle of carrier C) of the gate drive of the semiconductor element 1. The carrier cycle represents the pulse width modulation cycle for driving the semiconductor element 1 by pulse width modulation. The control device 50 outputs a reset signal SR that samples and resets the maximum value Vcp in synchronization with the carrier cycle. The peak hold unit 41 samples the maximum value Vcp of the capacitor voltage Vc detected during the turn-off of the semiconductor element 1 every time the reset signal SR is input. Thereby, the deterioration diagnosis device 40 acquires the maximum value Vcp of the capacitor voltage Vc in a certain period T for each carrier cycle of the semiconductor element 1, and updates the deterioration diagnosis result of the semiconductor element 1 for each carrier cycle of the semiconductor element 1.

[0044] 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 larger than the command value A, the control device 50 outputs a gate-off 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 (the maximum value in the illustrated example) of the carrier C, it can be surely reset in the gate-off state of the semiconductor element 1.

[0045] Note that the sampling of the maximum value Vcp may 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 necessarily have to be the same as the timing when the reset signal SR is input.

[0046] The completion of the turn-off of the semiconductor element 1 may 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 elapsed time since the turn-off signal is input to the semiconductor element 1. The completion of the turn-off of the semiconductor element 1 may be determined by this information of the semiconductor element connected in series with the semiconductor element 1 (not shown).

[0047] FIG. 9 is a diagram showing a configuration example that implements the method shown in FIG. 8. In FIG. 9, the description of the configuration, operation, and effects similar to those of the above-described embodiment is omitted by referring to the above description. The deterioration diagnosis system 103 according to the third embodiment shown in FIG. 9 is different from the above-described deterioration diagnosis system 101 or deterioration diagnosis system 102 in that it includes a reset circuit 34.

[0048] 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 in response to a reset signal SR synchronized with the operation cycle of the semiconductor element 1. Thereby, even without the discharge resistor 32, the capacitor 31 can be discharged every carrier cycle.

[0049] When the second switch 12 switches 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 without moving to the reset circuit 34 in which the reset switch is in the off state. As a result, the voltage Vgs between the gate G and 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 increases. When a reset signal SR synchronized with the operation cycle of the semiconductor element 1 is input to the reset circuit 34, the reset circuit 34 switches the reset switch from off to on. When the reset switch is turned on, the charge accumulated in the capacitor 31 starts to discharge through the on-state reset switch. Thereby, even if the turn-off time of the semiconductor element 1 is shortened, the discharge of the capacitor 31 can be started during the turn-off of the semiconductor element 1.

[0050] FIG. 10 is a diagram showing a configuration example of a degradation diagnosis system according to the fourth embodiment. In the fourth embodiment, descriptions of the same configurations, operations, and effects as those in the above-described embodiments are omitted by referring to the above descriptions. The degradation diagnosis system 104 according to the fourth embodiment shown in FIG. 10 differs from the above-described degradation diagnosis system 101 and the like in that the degradation diagnosis device 40 diagnoses the degradation of the semiconductor element 1 using the capacitor voltage Vc and the information of the semiconductor element 1.

[0051] Examples of the information of the semiconductor element 1 include the voltage Vds between the drain D and the source S of the semiconductor element 1, the current Id flowing between the drain D and the source S of the semiconductor element 1, the temperature Th of the semiconductor element 1, and the like.

[0052] 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, for example. The degradation diagnosis device 40 may acquire the information of the semiconductor element 1 from the control device 50, the gate drive circuit 20, or other devices.

[0053] The Qg-Vgs curve (see FIG. 2) changes according to the voltage Vds, the current Id, or the temperature Th. Referring to FIG. 2, as the voltage Vds or the current Id increases, or as the temperature Th decreases, the Qg-Vgs curve shifts as shown in FIG. 2, so the on-voltage Von and the threshold voltage Vth increase. Therefore, by using the information of the semiconductor element 1 by the degradation diagnosis device 40 for diagnosing the degradation of the semiconductor element 1, the accuracy of diagnosing the degradation of the semiconductor element 1 is improved.

[0054] The degradation diagnosis device 40 may diagnose the degradation 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 predetermined condition. Thereby, the timing for diagnosing the degradation 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 predetermined condition. For example, the frequency of diagnosing the degradation of the semiconductor element 1 is suppressed without becoming excessive.

[0055] As an example of the case where predetermined conditions are satisfied, there is a case where at least one of a first condition that the voltage Vds is higher than a predetermined voltage threshold, a second condition that the current Id is higher than a predetermined current threshold, and a third condition that the temperature is lower than a predetermined temperature threshold is satisfied.

[0056] FIG. 11 is a diagram showing a configuration example of a deterioration diagnosis system according to the fifth embodiment. In the fifth embodiment, the description of the same configuration, operation, and effects as those in the above-described embodiments is omitted by referring to the above description. The deterioration diagnosis system 105 according to the fifth embodiment shown in FIG. 11 is different from the above-described deterioration diagnosis system 101 and the like 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.

[0057] The deterioration diagnosis device 40 sets a threshold value Va corresponding to the information of the semiconductor element 1 acquired from the control device 50 or the like 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 acquired information of the semiconductor element 1. The threshold value Va is a determination threshold value for diagnosing the deterioration of the semiconductor element 1 and corresponds to, for example, a voltage value V2 (see FIG. 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 by the comparison unit 42. For example, when the maximum value Vcp is larger than the threshold value Va, the deterioration diagnosis device 40 diagnoses that the semiconductor element 1 is deteriorated.

[0058] FIG. 12 is a diagram showing a configuration example of a deterioration diagnosis system according to the sixth embodiment. In the sixth embodiment, the description of the same configuration, operation, and effects as those in the above-described embodiments is omitted by referring to the above description. The deterioration diagnosis system 106 according to the sixth embodiment shown in FIG. 12 is different from the above-described deterioration diagnosis system 105 in that the deterioration diagnosis device 40 diagnoses the deterioration of the semiconductor element 1 by comparing the capacitor voltage Vc with a fixed threshold value Va.

[0059] When the maximum value Vcp of the capacitor voltage Vc is greater than a fixed threshold value Va, the deterioration diagnosis device 40 diagnoses the deterioration of the semiconductor element 1 using information (for example, voltage Vds, current Id, or temperature Th, etc.) of the semiconductor element 1. Since the deterioration diagnosis unit 43 that diagnoses deterioration does not read the detected value itself of the capacitor voltage Vc, the number of AD converters for detecting the capacitor voltage Vc can be reduced.

[0060] The threshold value Va may be stored in advance in a memory, for example, or may be provided as a voltage source having the voltage of the threshold value Va. The threshold value Va is determined by a previously conducted test or a data sheet.

[0061] When the information of the semiconductor element 1 satisfies a predetermined condition and the capacitor voltage Vc is greater than the fixed threshold value Va, the deterioration diagnosis device 40 may diagnose the deterioration of the semiconductor element 1. For example, the deterioration diagnosis device 40 compares the maximum value Vcp of the capacitor voltage Vc with the threshold value Va by the comparison unit 42, and when the maximum value Vcp is greater than the threshold value Va, it asserts the determination signal Ve. When the information of the semiconductor element 1 such as the voltage Vds, current Id, or temperature Th satisfies the above predetermined condition and the determination signal Ve is asserted, the deterioration diagnosis unit 43 may diagnose that the semiconductor element 1 is deteriorated. The deterioration diagnosis unit 43 receives the assertion of the determination signal Ve, acquires the information of the semiconductor element 1 such as the voltage Vds, current Id, or temperature Th, and may diagnose that the semiconductor element 1 is deteriorated when these information satisfy the above predetermined condition.

[0062] FIG. 13 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. The deterioration diagnosis system 107 shown in FIG. 13 may be any of the 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 detected 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 detected value of the AC current detected by the current sensor 71.

[0063] The inverter circuit 70 is a bridge circuit constituted by 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 switching the plurality of semiconductor elements u, v, w, x, y, z, and drives a load M1 such as a motor with three-phase AC.

[0064] 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.

[0065] The semiconductor elements u, v, w, x, y, z are each an example of the semiconductor element 1 described above. FIG. 13 illustrates the case where the semiconductor element 1 is an IGBT having a gate G, an emitter, and a collector.

[0066] The deterioration diagnosis device 40 acquires the capacitor voltage Vc detected by the isolation type AD converter via an insulating portion 63 that insulates between a high potential portion and a low potential portion. Although not shown, the deterioration diagnosis device 40 acquires information on the semiconductor element 1 such as the voltage Vds, the current Id, or the temperature Th from a low potential portion such as the control device 50.

[0067] The degradation diagnosis device 40 is provided in an external device with relatively high computing power (for example, a control device 50 or an external server not shown). By being provided in an external device with high computing power, the degradation diagnosis device 40 can diagnose the degradation of semiconductor elements with high accuracy.

[0068] The degradation diagnosis device 40 diagnoses the degradation of some or all of the plurality of semiconductor elements u, v, w, x, y, z. In this example, it represents the degradation diagnosis of the semiconductor element u. The degradation diagnosis device 40 transmits the diagnosis results of the degradation of some or all of the plurality of semiconductor elements u, v, w, x, y, z to the user interface 72. The user interface 72 presents the received diagnosis results to the user by at least one presenting means among screen display, lamp, and speaker. Thereby, the user can recognize the diagnosis results.

[0069] FIG. 14 is a diagram showing a second example of the application of the degradation diagnosis system according to the present embodiment to a power conversion device. The degradation diagnosis system 108 shown in FIG. 14 may be any of a plurality of degradation diagnosis systems of the present disclosure. The configuration regarding the power conversion operation of the power conversion device 202 shown in FIG. 14 may be the same as that of the above-mentioned power conversion device 201. In this embodiment, information such as the voltage Vds, current Id, or temperature Th of the semiconductor element 1 may be acquired from the high potential part.

[0070] The degradation diagnosis device 40 is provided in the power conversion device 202 (for example, a gate drive circuit). The degradation diagnosis device 40 transmits the diagnosis result of the semiconductor element to the user interface 72 outside the power conversion device 202 by wire or wirelessly. The diagnosis result transmitted from the degradation diagnosis device 40 provided in the high potential part to the user interface 72 provided in the low potential part is information with a relatively small amount of information (for example, the presence or absence of degradation or the degradation level of the semiconductor element). For this reason, the degradation diagnosis device 40 can transmit the diagnosis result to the user interface 72 via the insulation part 63 without using a high-resolution device such as an isolation type AD converter.

[0071] As described above, the embodiments have been explained. However, the above embodiments are presented as examples, and the present invention is not limited by the above embodiments. The above embodiments can be implemented in various other forms, and various combinations, omissions, replacements, 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 also included in the invention described in the claims and the equivalent scope thereof.

[0072] For example, the gate resistor 21 may be provided within the push-pull circuit 10. The gate resistor 21 provided within the push-pull circuit 10 may 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 speed-up capacitor circuit 30 is connected in parallel with the turn-off gate resistor. The diode 33 within the speed-up capacitor circuit 30 has its anode connected to the gate drive line between the turn-off gate resistor and the gate G, and its cathode connected to one end of each of the capacitor 31 and the discharge resistor 32.

[0073] The operation and effect in the form where the gate resistor 21 is a turn-off gate resistor are the same as the operation and effect in the above-described embodiment where the gate resistor 21 is inserted in series between the connection point 14 and the gate G. Therefore, the above description is incorporated by reference and omitted.

[0074] The gate resistor 21 provided within the push-pull circuit 10 may 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 speed-up capacitor circuit 30 is connected in parallel with the turn-on gate resistor. The diode 33 within the speed-up capacitor circuit 30 has its cathode connected to the gate drive line between the turn-on gate resistor and the gate G, and its anode connected to one end of each of the capacitor 31 and the discharge resistor 32.

[0075] In the form where the gate resistor 21 is the turn-on gate resistor, when the first switch 11 switches from off to on, the charge on the first power 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 source S of the semiconductor element 1 rises rapidly, 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 begins 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 be started during the turn-on of the semiconductor element 1.

[0076] Even in the form where the gate resistor 21 is the turn-on gate resistor, similar to the case shown in FIG. 3, the voltage value when the capacitor voltage Vc becomes equal to the voltage Vgs differs before and after the deterioration of the semiconductor element 1. The deterioration diagnosis device 40 diagnoses the deterioration 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 (in this example, during turn-on) of the semiconductor element 1 is greater than the voltage value V2 set as the determination threshold value, the deterioration diagnosis device 40 diagnoses that the semiconductor element 1 is deteriorated.

Description of Reference Numerals

[0077] 1 Semiconductor element 10 Push-pull circuit 11 First switch 12 Second switch 13 Power supply 14 Connection point 15 First power line 16 Second power line 20 Gate drive circuit 21 Gate resistor 22 Gate line 23 Detection circuit 30 Speed-up capacitor circuit 31 Capacitor 32 Discharge resistor 33 Diode 34 Reset Circuit 40 Degradation Diagnosis Device 41 Peak Hold Section 42 Comparison Section 43 Degradation Diagnosis Section 50 Control Device 60 DC Power Supply 63 Insulation Section 70 Inverter Circuit 71 Current Sensor 72 User Interface 101,102,103,104,105,106,107,108 Degradation Diagnosis System 201,202 Power Conversion Device

Claims

1. A semiconductor device having a gate, a first main terminal that is a source or an emitter, and a second main terminal that is a drain or a collector; A push-pull circuit; A gate resistor provided 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 that diagnoses degradation of the semiconductor device using a capacitor voltage generated across both ends of the capacitor, a degradation diagnosis system comprising the same.

2. The degradation diagnosis device diagnoses degradation of the semiconductor device using a voltage value when the capacitor voltage becomes equal to a voltage between the gate and the first main terminal. The degradation diagnosis system according to Claim 1.

3. The voltage value is a maximum value of the capacitor voltage. The degradation diagnosis system according to Claim 2.

4. Having a peak hold section that holds a maximum value of the capacitor voltage over a certain period; The voltage value is a maximum value held by the peak hold section. The degradation diagnosis system according to Claim 3.

5. The peak hold section samples the maximum value according to an operation cycle of the semiconductor device. The degradation diagnosis system according to Claim 4.

6. The operation cycle is a zero-crossing period of an output voltage or an output current of the semiconductor device. The degradation diagnosis system according to Claim 5.

7. The operation cycle is a carrier period of the semiconductor device. The degradation diagnosis system according to Claim 5.

8. The degradation diagnosis device diagnoses degradation of the semiconductor device using the capacitor voltage and information of the semiconductor device. The degradation diagnosis system according to any one of Claims 1 to 7.

9. The degradation diagnosis device diagnoses degradation of the semiconductor device when information of the semiconductor device satisfies a predetermined condition. The degradation diagnosis system according to Claim 8.

10. The degradation diagnosis device diagnoses degradation of the semiconductor device by comparing the capacitor voltage with a threshold value set according to information of the semiconductor device. The degradation diagnosis system according to Claim 8.

11. The degradation diagnosis device diagnoses degradation of the semiconductor device using information of the semiconductor device when the capacitor voltage is greater than a fixed threshold value. The degradation diagnosis system according to Claim 8.

12. The deterioration diagnosis device according to claim 8, wherein when the information of the semiconductor element satisfies a predetermined condition and the capacitor voltage is greater than a fixed threshold value, the deterioration of the semiconductor element is diagnosed.

13. A deterioration diagnosis method for diagnosing the deterioration of a semiconductor element by using a 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.

14. A semiconductor element having a gate, a first main terminal that is a source or an emitter, and a second main terminal that is a drain or a collector, A push-pull circuit, A gate resistor provided in the push-pull circuit or between the push-pull circuit and the gate, A capacitor connected in parallel with the gate resistor, A deterioration diagnosis device for diagnosing the deterioration of the semiconductor element by using the capacitor voltage generated across the capacitor, A power conversion device comprising: a peak hold unit that holds the maximum value of the capacitor voltage over a certain period according to the operation cycle of the semiconductor element.

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

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