Gate driver for field-effect transistors

Abstract

To provide a gate drive device that easily detects at least one of characteristic variations of a field effect transistor.SOLUTION: A gate drive device 1 of a field effect transistor Tr1 includes a power supply V1 for outputting a gate drive voltage Vg and a gate resistance unit 10 in which an input resistance connected between a power supply and a gate G of the field effect transistor is configured to have a higher resistance value in an inspection mode than in an operation mode. A resistance value of a second input resistor Rg2 is sufficiently larger than that of a first input resistor Rg1, and is equal to or close to gate-emitter resistance Rge of the field-effect transistor. A switch SW1 inputs, in the operation mode, a gate drive voltage of the power supply to a gate of the field effect transistor through the first input resistor without going through the second input resistor, and inputs, in the inspection mode, the gate drive voltage of the power supply to the gate of the field effect transistor through the second input resistor without going through the first input resistor.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The technology disclosed herein relates to a gate driver for a field-effect transistor. [Background technology]

[0002] Field-effect transistors (FIELD-EVERYS) are used, for example, as power devices and are mounted in inverters that control the power supplied to a load. It is known that the electrical characteristics of such FIELD-EVERYS transistors can change over time with prolonged use. For example, gate leakage can increase due to the breakdown of the gate insulating film of a FIELD-EVERYS transistor. Alternatively, charge can be trapped in the gate insulating film, increasing the gate threshold voltage. Technologies for detecting such characteristic changes are needed.

[0003] Patent documents 1 and 2 disclose gate driving devices capable of detecting gate leakage in a field-effect transistor. Both gate driving devices disclosed in patent documents 1 and 2 are configured to detect gate leakage by referring to the voltage applied to the input resistance of the gate of a field-effect transistor. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2011-71174 [Patent Document 2] Japanese Patent Publication No. 2003-143833 [Overview of the project] [Problems that the invention aims to solve]

[0005] Generally, the gate-emitter (or gate-source) resistance of the gate insulating film of a field-effect transistor is several MΩ, while the gate input resistance is several Ω. Gate leakage current, which flows due to damage to the gate insulating film, flows through a series circuit of the gate-emitter resistance of the gate insulating film and the gate input resistance, but depending on the extent of the damage, it can be as small as 1 μA or less. Therefore, the voltage applied to the gate input resistance due to the gate leakage current is several μV or less. The technologies in Patent Documents 1 and 2 require measuring such a small voltage, which may result in the inability to detect gate leakage.

[0006] This specification provides a gate drive device capable of easily detecting at least one characteristic variation of a field-effect transistor. [Means for solving the problem]

[0007] The gate drive device for a field-effect transistor disclosed herein may include a power supply that outputs a gate drive voltage, and a gate resistor section configured such that the input resistance connected between the power supply and the gate of the field-effect transistor has a higher resistance value in the test mode than in the operating mode.

[0008] The gate drive device may further include a voltage measuring device configured to measure the gate voltage of the field-effect transistor, and a detection unit configured to generate an abnormal signal based on the gate voltage in the inspection mode. Here, the gate voltage is the voltage between the gate and emitter (or gate and source) of the field-effect transistor or an index correlated therewith. In this gate drive device, when considering a series circuit of the input resistance of the gate and the gate-emitter (or gate-source) resistance of the gate insulating film, the input resistance of the gate is higher in the inspection mode than in the operating mode. Therefore, when the gate-emitter (or gate-source) resistance of the gate insulating film fluctuates due to damage to the gate insulating film or the like, the gate voltage divided by the series circuit can fluctuate significantly in the inspection mode. The gate drive device disclosed herein can easily detect gate leakage of the field-effect transistor.

[0009] The detection unit may be configured to generate the abnormal signal when the gate voltage in the inspection mode falls below a predetermined threshold. This gate drive device can detect gate leakage of the field-effect transistor with a small amount of computation.

[0010] The detection unit may be configured to calculate the average value of the gate voltage measured for each of the past multiple inspection modes, calculate the difference between the average value and the gate voltage in the current inspection mode, and generate an abnormal signal based on the difference. For example, the detection unit may be configured to generate the abnormal signal when the difference exceeds a predetermined threshold. Alternatively, the detection unit may be configured to generate the abnormal signal based on the trend of the cumulative value of the difference calculated for each of the past multiple inspection modes. In this case, the detection unit may be configured to generate the abnormal signal based on the slope of the cumulative value from the origin. These gate drive devices make it possible to detect gate leakage of the field-effect transistor in a highly robust manner.

[0011] The resistance value of the input resistor in the test mode may be set such that the gate voltage is higher than the gate threshold voltage of the field-effect transistor when the field-effect transistor is in its initial state. With this gate drive device, it is possible to detect that the gate threshold voltage has changed when the field-effect transistor is turned off in the test mode.

[0012] The gate resistor section may include a first input resistor connected to the gate of the field-effect transistor, and a second input resistor connected to the gate of the field-effect transistor, having a higher resistance value than the first input resistor. The gate resistor section may be configured such that, in the operating mode, the gate drive voltage of the power supply is input to the gate of the field-effect transistor via the first input resistor without going through the second input resistor, and in the test mode, the gate drive voltage of the power supply is input to the gate of the field-effect transistor via the second input resistor. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic diagram of the gate drive mechanism configuration. [Figure 2] This diagram shows the equivalent circuit of the first input resistor, the second input resistor, and the gate-emitter resistor of a field-effect transistor. [Figure 3] This figure shows the gate voltage waveform of a field-effect transistor in test mode. [Figure 4] This figure shows a graph of the cumulative value obtained by accumulating the difference between the gate voltage in the current test mode and the average value of past gate voltages. [Figure 5] This diagram shows a graph illustrating the progression of the cumulative difference, and is intended to explain how to calculate the slope of the cumulative value from the origin. [Figure 6] This diagram illustrates the relationship between the number of cycles and the slope of the cumulative value from the origin. [Figure 7] This figure shows the waveform of the gate voltage of a field-effect transistor in test mode and illustrates a method for detecting fluctuations in the gate threshold voltage. [Figure 8] This diagram shows the processing flow of a gate drive device. [Figure 9] This diagram shows a modified configuration of the gate resistor section. [Figure 10] This diagram shows the configuration of another modified gate resistor section. [Figure 11] Figure 9 shows the specific circuit configuration of the gate resistor section. [Modes for carrying out the invention]

[0014] Figure 1 shows the configuration of a gate drive device 1 capable of detecting gate leakage and gate threshold voltage fluctuations of a field-effect transistor Tr1. Note that the gate drive device 1 may be configured to detect only one of the characteristic fluctuations, either gate leakage or gate threshold voltage fluctuation. In this example, the field-effect transistor Tr1 is an IGBT having a collector C and an emitter E. Alternatively, the field-effect transistor Tr1 may be a MISFET or MOSFET having a drain and a source. The collector C of the field-effect transistor Tr1 is at a DC voltage V ccIt is connected to the positive electrode of the power supply V2 that outputs [output content not provided in the original text], and the emitter E of the field-effect transistor Tr1 is grounded. A load (not shown) is connected in series to the field-effect transistor Tr1. The field-effect transistor Tr1 is used, for example, as a power device and is mounted on an inverter device or the like that controls the power supplied to a load (not shown).

[0015] The gate drive device 1 is configured to be able to execute an inspection mode for detecting gate leakage and gate threshold variation of the field-effect transistor Tr1 at a timing different from the normal operation mode. The gate drive device 1 includes a power supply V1 that outputs [output content not provided in the original text], a gate resistance section 10, a voltage measurement device 20, and a detection section 30. g It is provided between the power supply V1 and the gate G of the field-effect transistor Tr1, and has a first input resistance R

[0016] and a second input resistance R g1 and a switch SW1. g2 It has [output content not provided in the original text].

[0017] The first input resistance R g1 and the second input resistance R g2 are connected in parallel between the switch SW1 and the gate G of the field-effect transistor Tr1. The resistance value of the second input resistance R g2 is sufficiently larger than the resistance value of the first input resistance R g1 and is the same as or close to the resistance R ge between the gate and emitter of the field-effect transistor Tr1.

[0018] The switch SW1 is configured to switch the connection destination of the power supply V1 between the first input resistance R g1 and the second input resistance R g2 . In the operation mode, by connecting the connection destination of the power supply V1 to the first input resistance R g1 , the gate drive voltage Vg of the power supply V1 is applied to the first input resistance R g2 without passing through the second input resistance R g1It is configured to input to the gate G of the field-effect transistor Tr1 via the switch SW1. In test mode, the switch SW1 is further configured to connect to the second input resistor R of the power supply V1. g2 By connecting to the first input resistor R, the gate drive voltage Vg of the power supply V1 becomes R g1 Without going through the second input resistor R g2 It is configured to be input to the gate G of the field-effect transistor Tr1 via [this].

[0019] The voltage measuring device 20 measures the gate voltage V, which is the voltage between the gate and emitter of the field-effect transistor Tr1. ge It is configured to measure the gate voltage V of the field-effect transistor Tr1. The voltage measuring device 20 measures the gate voltage V of the field-effect transistor Tr1, at least in the test mode. ge It is configured to measure the second input resistor R. In this example, the voltage measuring device 20 is configured to directly measure the gate-emitter voltage of the field-effect transistor Tr1. Alternatively, in test mode, the voltage measuring device 20 is configured to measure the second input resistor R g2 Measure the voltage across the terminals and the gate drive voltage V of power supply V1. g The second input resistance R measured from g2 By subtracting the voltage across the terminals, the gate voltage V of the field-effect transistor Tr1 is obtained. ge You may measure it.

[0020] The detection unit 30 is for detecting gate leakage of the field-effect transistor Tr1 and includes a calculation unit 32, a memory 34, a comparator 36, and a notification device 38.

[0021] The arithmetic unit 32 receives the gate voltage V of the field-effect transistor Tr1 from the voltage measuring device 20. geThe arithmetic unit 32 receives the signal and executes the calculation method described below to calculate the calculation result (i.e., feature quantity) in the current inspection mode. The arithmetic unit 32 stores the calculated calculation result in the memory 34 as needed. The comparator 36 compares the calculated calculation result with a set threshold and outputs an abnormal signal to the notification device 38 based on the comparison result. When the notification device 38 receives an abnormal signal from the comparator 36, it notifies the user and / or the higher-level system that the gate leakage of the field-effect transistor Tr1 has increased.

[0022] (Method for detecting gate leaks) Figure 2 shows the first input resistor R. g1 and the second input resistor R g2 and the gate-emitter resistor R of the field-effect transistor Tr1 ge The equivalent circuit is shown. First input resistor R g1 The resistance value is 1Ω. Second input resistor R g2 The resistance value is 10MΩ. The gate-emitter resistance R of the field-effect transistor Tr1. ge The initial resistance value is 50 MΩ. The gate-emitter resistance R ge The initial resistance value refers to the state in which no substantial damage has occurred to the gate insulating film of the field-effect transistor Tr1. For example, it is the gate-emitter resistance value of the field-effect transistor Tr1 immediately after it has been shipped.

[0023] Here, damage occurs to the gate insulating film of the field-effect transistor Tr1, and the gate-emitter resistance R ge Assume that the resistance value of the resistor R has decreased by 10% from its initial value, degrading to 45 MΩ. Switch SW1 connects to the first input resistor R of power supply V1. g1 If this is the case, the first input resistor R will be placed between the power supply V1 and ground. g1 and the gate-emitter resistor R ge A series circuit exists. The gate-emitter resistance R ge The first input resistor R has a resistance value relative to the value of the first input resistor R. g1 Since the resistance value is sufficiently small, the gate-emitter resistor R ge Even if the first input resistor R deteriorates, g1and the gate-emitter resistor R ge The voltage division ratio due to the series circuit remains almost unchanged. Therefore, the first input resistor R g1 The voltage V applied across both ends Rg1 Regarding the gate-emitter resistance R, ge The voltage before degradation was 0.20 μV, and after degradation it was 0.22 μV, a difference of 0.02 μV. The conventional technology described in the background technology is the first input resistor R g1 The voltage V applied across both ends Rg1 This method attempts to detect gate leaks by measuring the voltage difference before and after degradation. Conventional techniques have resulted in small differences in measured voltage before and after degradation, making gate leak detection difficult.

[0024] On the other hand, in the gate drive device 1 disclosed herein, in inspection mode, switch SW1 connects to the second input resistor R, which is the destination of the power supply V1. g2 Switch to the second input resistor R. g2 The resistance value is the first input resistor R g1 The resistance value is sufficiently larger than the gate-emitter resistance R. ge It is close to this value. Therefore, the gate-emitter resistance R ge When the second input resistor R deteriorates, g2 and the gate-emitter resistor R ge The voltage division ratio due to the series circuit fluctuates significantly. Therefore, the second input resistor R g2 The voltage V applied across both ends Rg2 Regarding the gate-emitter resistance R, ge The voltage before degradation was 1.67V, and after degradation it was 1.82V, a difference of 0.15V. Similarly, the gate voltage V of the field-effect transistor Tr1 ge Also, the gate-emitter resistance R ge A difference of 0.15V occurs before and after the degradation. Such a difference in measured voltage is a change that can be easily detected even by a simple voltage measuring device 20 with low resolution.

[0025] Figure 3 shows the gate voltage V of the field-effect transistor Tr1 in test mode. geThe waveform is shown. In test mode, at timing t1, the gate drive voltage V from power supply V1 is shown. g The supply is started, and at timing t3, the gate drive voltage V from power supply V1 is started. g The supply will be terminated. From timing t1 to t2, switch SW1 is the first input resistor R g1 It is connected to the second input resistor R, and from timing t2 to t3, switch SW1 is connected to the second input resistor R. g2 It is connected to this. Thus, in inspection mode, the gate drive voltage V g While continuing to supply power, connect switch SW1 to the first input resistor R g1 From the second input resistor R g2 This is implemented to switch to the gate-emitter resistor R. The solid line represents the gate-emitter resistor R. ge This is the waveform before degradation, and the dashed line represents the gate-emitter resistance R. ge This is the waveform after degradation.

[0026] As described above, switch SW1 is the second input resistor R g2 When connected (timing t2 to t3), the gate-emitter resistance R ge Before and after degradation, the gate voltage V of the field-effect transistor Tr1 ge A difference of 0.15V occurs. The gate drive device 1 is configured to use this difference to detect gate leakage of the field-effect transistor Tr1. Note that the switch SW1 is switched between timing t1 and t2 and the first input resistor R g1 The reason for connecting it is to confirm that the field-effect transistor Tr1 is functioning correctly. If this confirmation is omitted and the test mode starts from the beginning, switch SW1 is connected to the second input resistor R g2 You may connect to it.

[0027] Next, the calculation methods 1 to 4 executed by the detection unit 30 of the gate drive device 1 will be described. The gate drive device 1 detects the gate leakage of the field-effect transistor Tr1 by appropriately utilizing the following calculation methods 1 to 4.

[0028] (1) Calculation method 1 In this calculation method 1, a predetermined voltage value that serves as a threshold for comparison by the comparator 36 is recorded in the memory 34. The comparator 36 uses the gate voltage V in the current test mode, measured by the voltage measuring device 20. ge This is compared to a threshold value recorded in memory 34. The comparator 36 checks the gate voltage V in the current test mode. ge When the value falls below the threshold, an abnormal signal is output to the notification device 38. This calculation method 1 allows for the detection of an increase in the gate leakage of the field-effect transistor Tr1 with minimal computational processing.

[0029] (2) Calculation method 2 In this calculation method 2, the gate voltage V measured for each of the past multiple inspection modes is used. ge The average value, the number of past test modes, and a predetermined voltage value that serves as a threshold for comparison by the comparator 36 are recorded in the memory 34. The arithmetic unit 32 records the gate voltage V in the current test mode measured by the voltage measuring device 20. ge and past gate voltage V ge The difference in the average values ​​is calculated, and the gate voltage V in the current inspection mode is calculated. ge A new average value is calculated by adding the difference. The calculated difference and the newly calculated average value are recorded in memory 34. The comparator 36 compares the calculated difference with a threshold value stored in memory 34. When the calculated difference exceeds the threshold value, the comparator 36 outputs an abnormal signal to the notification device 38. Because this calculation method 2 uses an average value, it is possible to detect an increase in the gate leakage of the field-effect transistor Tr1 while suppressing a certain degree of device characteristic variation and measurement variation. This calculation method 2 is a more robust detection method than calculation method 1.

[0030] (3) Calculation method 3 In this calculation method 3, in addition to the information recorded in memory 34 in calculation method 2 above, the integrated value of the differences calculated for each of the past multiple inspection modes is also recorded in memory 34. The calculation device 32 calculates the integrated value of the differences by adding the newly calculated differences to the calculation performed in calculation method 2 above. The newly calculated integrated value of the differences is recorded in memory 34. The comparator 36 compares the calculated integrated value of the differences with a threshold value stored in memory 34. When the calculated integrated value of the differences exceeds the threshold value, the comparator 36 outputs an abnormal signal to the notification device 38. Calculation methods 1 and 2 above are susceptible to noise such as instantaneous fluctuations. On the other hand, calculation method 3 suppresses large fluctuations in the integrated value of the differences due to such instantaneous fluctuations. Therefore, calculation method 3 can detect gate leakage of the field-effect transistor Tr1 while suppressing the effects of noise. This calculation method 3 is a more robust detection method than calculation methods 1 and 2.

[0031] Figure 4 shows a graph of the cumulative difference calculated by the gate drive unit 1. Figure 4 shows graphs of the cumulative difference for two field-effect transistors Tr1, "A" and "B". In field-effect transistor Tr1 "A", the rate of increase of the cumulative difference increases after the number of test mode cycles reaches N2. Therefore, it is suggested that when the number of test mode cycles reached N2, damage occurred in the gate insulating film of field-effect transistor Tr1 "A". In field-effect transistor Tr1 "B", the rate of increase of the cumulative difference increases after the number of test mode cycles reaches N1. Therefore, it is suggested that when the number of test mode cycles reached N1, damage occurred in the gate insulating film of field-effect transistor Tr1 "B". In calculation method 3, when the cumulative difference exceeds a predetermined threshold, an abnormal signal is output to the notification device 38.

[0032] Comparing the graphs of the cumulative difference changes, the field-effect transistor Tr1 of "B" shows an earlier point of change in the rate of increase of the cumulative difference than the field-effect transistor Tr1 of "A". However, because the rate of increase of the cumulative difference is smaller for field-effect transistor Tr1 of "B" than for field-effect transistor Tr1 of "A", the time it takes for the cumulative difference to reach a predetermined threshold is slower for field-effect transistor Tr1 of "A". Calculation method 4, described below, is a method that can quickly capture the point of change in the cumulative difference.

[0033] (4) Calculation method 4 In this calculation method 4, in addition to the information recorded in memory 34 in calculation method 3 above, the slope of the cumulative difference value from the origin in the graph of the transition of the cumulative difference value is recorded. The arithmetic unit 32 calculates the slope of the cumulative difference value from the origin based on the number of inspection modes in the current inspection mode and the cumulative difference value, in addition to the calculation performed in calculation method 3 above. The calculated slope of the cumulative difference value is recorded in memory 34. The comparator 36 compares the calculated slope of the cumulative difference value from the origin with a threshold value recorded in memory 34. When the calculated slope of the cumulative difference value exceeds the threshold value, the comparator 36 determines that the gate leak has increased and outputs an abnormal signal to the notification device 38. In this example, the horizontal axis is the number of inspection modes, but this may be replaced with the usage time of the field-effect transistor Tr1, etc.

[0034] Figure 5 shows a graph illustrating the progression of the cumulative difference calculated by the gate drive unit 1. The inspection mode count "N12" indicates the current inspection mode. A point of change in the cumulative difference is observed at inspection mode count "N11," which is several inspection modes prior to the current inspection mode.

[0035] In the test mode, from cycle number "0 (i.e., the origin)" to "N11", the change in the difference is small, and the cumulative value of the difference increases at roughly a constant rate. The relationship between the number of cycles from the origin to "N11" and the cumulative value of the difference is y=ax, and the slope from the origin is constant at a. When the gate leakage of the field-effect transistor Tr1 increases and the difference changes significantly, the relationship between the number of cycles from "N11" to "N12" and the cumulative value of the difference becomes y=a'x-b', and the slope from the origin becomes a'-b' / x.

[0036] Figure 6 shows a graph illustrating the relationship between the number of cycles and the slope from the origin. As shown, the slope from the origin remains constant until gate leakage occurs in the field-effect transistor Tr1, and changes significantly as the gate leakage increases. In calculation method 4, an abnormal signal is output to the notification device 38 when the slope from the origin exceeds a predetermined threshold. By detecting the point of change in the slope from the origin in calculation method 4, it is possible to quickly detect an increase in gate leakage in the field-effect transistor Tr1.

[0037] (Method for detecting fluctuations in gate threshold voltage) Figure 7 shows the gate voltage V of the field-effect transistor Tr1 in test mode. ge The waveform is shown. Note that this gate voltage V ge The waveform is shown in Figure 3, where R is the gate-emitter resistor. ge Gate voltage V before degradation ge It is similar to the waveform shown.

[0038] Figure 7(A) shows "V th1 " is the initial value of the gate threshold voltage of the field-effect transistor Tr1. "V" is shown in Figure 7(B). th2 "This means that the charge is trapped in the gate insulating film of the field-effect transistor Tr1 and the gate threshold voltage is ΔV th This is the value after an increase of that amount.

[0039] As described above, in the gate drive device 1, at timing t2, switch SW1 connects the power supply V1 to the second input resistor R, which has a high resistance value. g2By switching to, the gate voltage V of the field - effect transistor Tr1 ge decreases. In the gate driving device 1, as shown in (A) of FIG. 7, after this decrease, the gate voltage V ge is slightly higher than the initial value of the gate threshold voltage of the field - effect transistor Tr1, which is "V th1 ". Thus, the resistance value of the second input resistor R g2 is set. Therefore, if the gate threshold voltage of the field - effect transistor Tr1 does not fluctuate significantly, after switching to the second input resistor R g2 , the field - effect transistor Tr1 continues to be in the on state.

[0040] However, as shown in (B) of FIG. 7, when the gate threshold voltage of the field - effect transistor Tr1 increases to "V th2 " and exceeds the gate voltage V ge , the field - effect transistor Tr1 turns off. When the field - effect transistor Tr1 turns off in the inspection mode, the gate driving device 1 determines that the gate threshold voltage of the field - effect transistor Tr1 has increased, and uses the notification device 38 to notify the user and / or the upper - level system that the gate threshold voltage of the field - effect transistor Tr1 has increased. Note that the on or off determination of the field - effect transistor Tr1 can be made by monitoring a current measuring device (not shown) connected in series to the collector C or emitter E of the field - effect transistor Tr1.

[0041] In the gate driving device 1, one second input resistor R g2 was connected between the power supply V1 and the gate G of the field - effect transistor Tr1. Instead of this example, by configuring the input resistor between the power supply V1 and the gate G of the field - effect transistor Tr1 to be continuously or multi - step variable in the inspection mode (for example, using a variable resistor or multiple resistors), the fluctuation of the gate threshold voltage of the field - effect transistor Tr1 can be detected with high resolution.

[0042] (Processing flow of the gate driving device) Hereinafter, referring to FIG. 8, the processing flow executed by the gate driving device 1 will be described.

[0043] First, in step S1, the gate driving device 1 determines whether it is the timing of the inspection mode. For example, when the field-effect transistor Tr1 and the gate driving device 1 are used in an in-vehicle inverter device, the gate driving device 1 is not particularly limited, but may determine that it is the timing of the inspection mode immediately after the vehicle ignition is turned on, or when the vehicle has stopped at an intersection or the like for a predetermined time has elapsed, or when it is not related to the movement of the vehicle. In the case of the inspection mode, in step S2, the gate driving device 1 starts supplying the gate driving voltage V from the power supply V1. Note that the connection destination of the switch SW1 is the first input resistor R when the operation mode state is maintained. g and it becomes. g1

[0044] Next, in step S3, the gate driving device 1 switches the connection destination of the switch SW1 to the second input resistor R. After switching to the second input resistor R, in step S4, the gate driving device 1 uses the voltage measuring device 20 to obtain the gate voltage V of the field-effect transistor Tr1. g2 g2 ge

[0045] Next, in step S5, the gate driving device 1 calculates a feature amount using the arithmetic device 32, and records the calculated feature amount in the memory 34 as necessary. The feature amount calculated here is the feature amount described by the adopted arithmetic method among the above arithmetic methods 1 to 4.

[0046] ​​​​Next, in step S6, the gate drive unit 1 uses the comparator 36 to determine whether the feature quantity exceeds a threshold. If the feature quantity exceeds the threshold, the gate drive unit 1 determines that the gate leakage of the field-effect transistor Tr1 has increased and outputs an abnormal signal to the notification device 38. In step S7, the gate drive unit 1 uses the notification device 38 to notify the user and / or the higher-level system that the gate leakage of the field-effect transistor Tr1 has increased, and terminates the inspection mode.

[0047] If the feature quantity does not exceed the threshold, the gate drive unit 1 determines in step S8 whether or not to detect a change in the gate threshold voltage. The detection of a change in the gate threshold voltage is not particularly limited, but may be performed for each test mode, for example, at predetermined intervals of the test mode, or for each test mode after the test mode has reached a predetermined number of cycles. If a change in the gate threshold voltage is not detected, the gate drive unit 1 terminates the test mode. If a change in the gate threshold voltage is detected, the gate drive unit 1 proceeds to step S9.

[0048] In step S9, the gate drive device 1 controls the second input resistor R g2 When the switch is made, it is determined whether the field-effect transistor Tr1 remains ON or OFF. If the field-effect transistor Tr1 remains ON, the gate drive unit 1 determines that the gate threshold voltage has not fluctuated significantly and terminates the inspection mode. If the field-effect transistor Tr1 is OFF, in step S10, the gate drive unit 1 uses the notification device 38 to notify the user and / or the higher-level system that the gate threshold voltage of the field-effect transistor Tr1 has increased and terminates the inspection mode.

[0049] (Modified gate resistor section) The gate resistance section 10 of the gate drive device 1 described above is the first input resistance R g1 and the second input resistor R g2The switch SW1 and the gate G of the field-effect transistor Tr1 were connected in parallel. The gate resistor 10 disclosed herein is configured such that the input resistance connected between the power supply V1 and the gate G of the field-effect transistor Tr1 has a higher resistance value in the test mode than in the operating mode.

[0050] For example, as shown in Figure 9, the first input resistor R g1 and the second input resistor R g2 A power supply V1 is connected in series with the gate G of the field-effect transistor Tr1, and a switch SW1 is connected to the second input resistor R g2 It may be connected in parallel with the other. Switch SW1 is configured to open in test mode.

[0051] For example, as shown in Figure 10, the first input resistor R g1 and the second input resistor R g2 A power supply V1 is connected in parallel between the power supply V1 and the gate G of the field-effect transistor Tr1, and a switch SW1 is connected to the first input resistor R g1 A second input resistor R is connected in series with the first input resistor. g2 It may be connected in parallel with the other. Switch SW1 is configured to open in test mode.

[0052] Here, Figure 11 shows an example of a specific circuit configuration of the gate resistor section 10 in Figure 9. In this example, the gate drive device 1 is configured as a general push-pull type drive circuit. The first input resistor R is located between the connection point of the NPN type first transistor Q1 and the PNP type second transistor Q2 and the gate G of the field-effect transistor Tr1. g1 The second input resistor R is connected. g2 The third transistor Q3, an NPN type, is connected in parallel with the first transistor Q1, and the second input resistor R g2 It is connected in series with the first transistor Q1 and in parallel with the first transistor Q1.

[0053] In operating mode, the field-effect transistor Tr1 is driven by switching the first transistor Q1 and the second transistor Q2 on and off, while the third transistor Q3 is not driven (always off). In test mode, the system switches from a state where the first transistor Q1 is on, the second transistor is off, and the third transistor Q3 is off, to a state where the first transistor Q1 is off, the second transistor is off, and the third transistor Q3 is on. Due to this switching operation, the input resistance between the power supply V1 and the gate G of the field-effect transistor Tr1 is the first input resistance R g1 Starting from the state with only the first input resistor R g1 and the second input resistor R g2 The gate resistors switch to a series connection state. The gate resistor section 10 shown in Figure 11 can be easily incorporated into existing push-pull type drive circuits.

[0054] Although specific examples of the present invention have been described in detail above, these are merely illustrative and do not limit the scope of the claims. The technologies described in the claims include various modifications and changes to the specific examples illustrated above.

[0055] In each of the calculation methods described above, the gate voltage V of the field-effect transistor Tr1 is ge This method involved directly calculating and processing the gate voltage V to detect gate leaks. Instead of this example, for example, the gate voltage V ge The second input resistor R correlates with g2 Similarly, gate leakage can be detected by calculating the voltage across the terminals. In this specification, the gate voltage V ge To perform calculations on the gate voltage V ge It is used in a broad sense, including cases where calculations are performed on values ​​that correlate with each other.

[0056] In calculation methods 3 and 4 described above, the cumulative value of the differences was used. Instead of this example, the mean of the differences, the variance of the differences, the standard deviation of the differences, etc., may also be used.

[0057] The above-mentioned field-effect transistor Tr1 may be used in an in-vehicle inverter device. In this case, the detection unit 30 of the gate drive device 1 may be mounted in the in-vehicle ECU, built into a semiconductor module constituting the inverter device, incorporated into the gate drive circuit, or mounted on a server outside the vehicle and the gate voltage V is transmitted via a communication device. ge It may be configured to receive.

[0058] Furthermore, the technical elements described herein or in the drawings demonstrate technical usefulness individually or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technologies illustrated herein or in the drawings can achieve multiple objectives simultaneously, and achieving even one of these objectives itself constitutes technical usefulness. [Explanation of Symbols]

[0059] 1: Gate drive unit, 10: Gate resistance unit, 20: Voltage measuring device, 30: Detection unit, 32: Calculation unit, 34: Memory, 36: Comparator, 38: Notification device, R g1 : First input resistor, R g2 : Second input resistor, Tr1: Field-effect transistor, V1: Power supply

Claims

1. A gate drive device for a field-effect transistor, A power supply that outputs the gate drive voltage, A gate resistor section is configured such that the input resistance connected between the power supply and the gate of the field-effect transistor has a higher resistance value in the test mode than in the operating mode. A voltage measuring device configured to measure the gate voltage of the aforementioned field-effect transistor, The system includes a detection unit configured to generate an abnormal signal based on the gate voltage in the inspection mode, The gate drive device is configured such that the detection unit calculates the average value of the gate voltage measured for each of the past multiple inspection modes, calculates the difference between the average value and the gate voltage in the current inspection mode, and generates the abnormal signal based on the difference.

2. The gate drive device according to claim 1, wherein the detection unit is configured to generate the abnormal signal when the difference exceeds a predetermined threshold.

3. The gate drive device according to claim 1, wherein the detection unit is configured to generate the abnormal signal based on the trend of the cumulative value of the difference calculated for each of the past multiple inspection modes.

4. The gate drive device according to claim 3, wherein the detection unit is configured to generate the abnormal signal based on the slope of the integrated value from the origin.

5. The gate drive device according to any one of claims 1 to 4, wherein the resistance value of the input resistor in the test mode is set such that the gate voltage is higher than the gate threshold voltage of the field-effect transistor when the field-effect transistor is in its initial state.

6. The gate resistor section is A first input resistor connected to the gate of the field-effect transistor, The field-effect transistor has a second input resistor connected to the gate, and the second input resistor has a higher resistance value than the first input resistor. The gate drive device according to any one of claims 1 to 5, wherein the gate resistor is configured such that, in the operating mode, the gate drive voltage of the power supply is input to the gate of the field-effect transistor via the first input resistor without going through the second input resistor, and in the test mode, the gate drive voltage of the power supply is input to the gate of the field-effect transistor via the second input resistor.

7. A gate drive device for a field-effect transistor, A power supply that outputs the gate drive voltage, The system includes a gate resistor section configured such that the input resistance connected between the power supply and the gate of the field-effect transistor has a higher resistance value in the test mode than in the operating mode, A gate drive device in which the resistance value of the input resistor in the test mode is set such that when the field-effect transistor is in its initial state, the gate voltage of the field-effect transistor is higher than the gate threshold voltage of the field-effect transistor.

Images