JP2016116411A - Abnormality detection method for semiconductor device - Google Patents

Abstract

A method for detecting an abnormality of a semiconductor device capable of detecting that some semiconductor elements are in an overheated state is provided. An abnormality detection method for a semiconductor device, which includes a plurality of semiconductor elements having a negative temperature characteristic with a magnitude of an operating threshold voltage, and outputs an energization current obtained by combining currents flowing through the plurality of semiconductor elements. A plurality of semiconductor elements in a predetermined temperature range are obtained by obtaining a first waveform that is a time-varying waveform of an energization current detected when a plurality of semiconductor elements in a predetermined temperature range is driven with a first pulse. By calculating a second waveform that is a time-varying waveform of the energization current detected when driving with a second pulse, and detecting a difference between the second waveform and the first waveform, a plurality of It is detected that a part of the semiconductor element is in an overheated state. [Selection] Figure 5

Description

  The present invention relates to a method for detecting the occurrence of a heat generation abnormality in a semiconductor device.

  Since power semiconductor devices are exposed to high voltage and high current usage environments, it is common to detect overheating conditions to protect the devices from degradation and destruction.

  Patent Document 1 describes that a temperature of an IGBT chip is monitored by bonding and arranging a PTC (Positive Temperature Coefficient) element on an IGBT (Insulated Gate Bipolar Transistor) chip.

International Publication No. 2006/068082

  In a semiconductor device having a semiconductor region composed of an assembly of unit cells such as an IGBT chip, a semiconductor element is formed for each unit cell included in the semiconductor region. An inverter provided in a vehicle or the like is provided with an element having a large chip size because a large current flows, and there is a possibility that the heat generation distribution in the chip may be biased due to non-uniform joining to the heat radiating body. When the semiconductor element of any one of the cells is in an overheated state or in a partially overheated state, the reliability of the connection portion may be lowered due to deformation such as chip warping or a failure due to partial thermal destruction may occur.

  However, the conventional temperature monitoring method can only know a macro temperature representative of the state of the cell aggregate. Therefore, it is difficult to detect the occurrence of partial overheating in the chip.

  In view of the above problems, the present invention provides a method for detecting an abnormality of a semiconductor device that can detect that some semiconductor elements are in an overheated state.

  A first aspect of the present invention is a method for detecting an abnormality in a semiconductor device having a plurality of semiconductor elements having negative temperature characteristics with a magnitude of an operating threshold voltage, and outputting an energized current obtained by synthesizing currents flowing through the plurality of semiconductor elements. When the temperature change is within a predetermined value within a predetermined temperature range and for a predetermined time, the plurality of semiconductor elements generate an energized state in which heat dissipation is within the transient heat region. A first waveform that is a time-varying waveform of the energization current detected when driven by one pulse is obtained, and the plurality of semiconductors are generated by a second pulse that generates an energization state in which heat dissipation becomes a steady heat region By obtaining a second waveform that is a time-varying waveform of the energization current that is detected when the element is driven, and detecting a difference between the second waveform and the first waveform, Some semiconductor elements are overheated To detect the Rukoto.

  According to the first invention, when the plurality of semiconductor elements are driven by the first driving method when the temperature change is within the predetermined range and the temperature change is within the predetermined range, A waveform is obtained, and then a difference from the waveform obtained by the second driving method is detected, thereby detecting occurrence of partial overheating in which some semiconductor elements are in an overheated state. In a plurality of semiconductor elements having a temperature characteristic in which the magnitude of the operation threshold voltage is negative, the occurrence of partial overheating causes a specific change in the waveform of the energization current from the first waveform. Therefore, if the difference between the second waveform and the first waveform is detected, it can be determined whether or not a change specific to the waveform has occurred, and the occurrence of partial overheating can be detected.

  ADVANTAGE OF THE INVENTION According to this invention, the abnormality detection method of a semiconductor device which can detect that a one part semiconductor element is in an overheated state can be provided.

The circuit block diagram which shows the structure of the apparatus group containing the apparatus which performs the abnormality detection method of the semiconductor device which concerns on embodiment of this invention 4 is a time chart for explaining processing by the abnormality detection method for a semiconductor device according to the embodiment of the present invention. The graph explaining the principle which detects abnormality of a semiconductor device concerning an embodiment of the present invention. The graph explaining the electric current waveform calculated | required by the abnormality detection method of the semiconductor device which concerns on embodiment of this invention 6 is a flowchart for explaining processing by a semiconductor device abnormality detection method according to an embodiment of the present invention;

  Hereinafter, embodiments will be described with reference to FIGS.

[Configuration of device group including control device]
FIG. 1 shows a configuration of a device group including devices that execute the abnormality detection method for a semiconductor device according to the present embodiment. The abnormality detection method for the semiconductor device is to obtain a waveform of a change in energization current of the semiconductor device 1 over time and detect a heat generation abnormality such as partial overheating from the characteristics of the waveform. The device group is provided in a vehicle such as an automobile, and includes a semiconductor device 1, a drive device 2, a current sensor 3, a temperature sensor 4, and a control device 5.

  The semiconductor device 1 has a semiconductor region R composed of an assembly of unit cells U. The unit cell U includes an IGBT (semiconductor element) 1a constituting one functional unit. The gate threshold voltage (operation threshold voltage) of the IGBT 1a has a so-called negative temperature characteristic that decreases as the temperature increases. The IGBTs 1a of all the unit cells U are connected in parallel. The collectors of the IGBTs 1 a are connected to each other, and the connection point between the collectors is drawn out of the semiconductor device 1 as the collector terminal C of the semiconductor region R. The emitters of the IGBTs 1a are connected to each other, and the connection point between the emitters is drawn out of the semiconductor device 1 as the emitter terminal E of the semiconductor region R.

  The semiconductor device 1 is cooled by a cooler (not shown). The cooler temperature Tc is detected by a temperature sensor (not shown), and temperature information of the cooler temperature Tc is input to the control device 5. In addition, the vehicle speed Vs is input to the control device 5 from a vehicle speed sensor (not shown).

  The driving device 2 drives each IGBT 1a by pulse width control or the like. The operation of the driving device 2 is controlled by the control device 5.

  The current sensor 3 detects a current that flows out from the emitter terminal E when the IGBT 1a is driven, that is, a conduction current Ic in the semiconductor region R. The energization current Ic is a combined current of the collector currents of all the IGBTs 1a. The energization current Ic may be detected from a current flowing into the collector terminal C. Information on the current detected by the current sensor 3 is input to the control device 5.

  The temperature sensor 4 detects the element temperature Tigbt of the IGBT 1a in the semiconductor region R or in the vicinity of the semiconductor region R. The temperature sensor 4 transmits information on the detected element temperature Tigbt to the control device 5. The temperature sensor 4 is composed of, for example, a temperature detection diode or a thermistor.

  The control device 5 controls the normal drive performed by the drive device 2 on the IGBT 1a and performs the following operation. The control device 5 obtains a time-change waveform of the energization current Ic as shown in FIG. 4 from the information of the energization current Ic acquired from the current sensor 3. When some of the IGBTs 1a are in an overheated state, the waveform has a characteristic change from the waveform at normal temperature. Therefore, if this unique change is detected, it can be detected that the semiconductor region R is in a partially overheated state. If partial overheating has occurred, the control device 5 changes the control mode of the IGBT 1a and controls to notify the user.

[Control device processing]
Next, current waveform acquisition processing and evaluation processing by the control device 5 will be described with reference to FIGS. The semiconductor device 1 constitutes an inverter that supplies electric power to a vehicle motor. FIG. 2 shows the relationship between the state of the vehicle and the processing of the control device 5. In FIG. 2, (A) shows the transition when the vehicle state and the control mode of the IGBT 1a are viewed in time series, (B) shows the drive signal waveform of the IGBT 1a, (C) shows the change in the element temperature Tigbt, (D). Indicates changes in the vehicle speed Vs. FIG. 3 shows the relationship between the gate voltage of the IGBT 1a and the energization current Ic. FIG. 4 shows a waveform of the change over time of the energization current Ic obtained by the control device 5 from the acquired information of the energization current Ic.

  For convenience of explanation, in FIG. 2A, it is assumed that four periods of a normal mode period F0, a temporary stop period F1, a measurement period F2, and an output limit mode period F3 are sequentially continued. A reference current waveform (first waveform), which is a normal current waveform of the energization current Ic, is obtained in the first half of the measurement period F2, and a current waveform (second waveform) is newly obtained in the second half of the measurement period F2. Compare with current waveform. As a result of the comparison, a change specific to the waveform is recognized and the occurrence of partial overheating is detected, and the vehicle travels in the output restriction mode period F3 corresponding to the detection.

  As shown by the solid line in FIG. 3, when the heat generation in the semiconductor region R is uniform, the relationship between the gate voltage of the IGBT 1a and the energization current Ic is a curve f that smoothly connects before and after the gate threshold voltage Vth0. When a plurality of IGBTs 1a are driven and a part of the IGBTs 1a is overheated, the gate threshold voltage Vth1 of the part of the IGBTs 1a becomes smaller than the gate threshold voltage Vth0. Therefore, the overheated IGBT 1a shifts to the on state with a lower gate voltage than the other IGBTs 1a. As a result, a distortion df in the direction in which the current increases around the gate threshold voltage Vth1 appears in the relationship between the gate voltage and the energization current Ic.

  In the normal mode period F0, the vehicle is traveling and the semiconductor device 1 is in a warm state. In order to continue the normal mode period F0, the element temperature Tigbt is required to be lower than the threshold temperature Tth. As shown in FIG. 2C, there is a state in which the element temperature Tigbt exceeds a reference temperature T0 (described later) that determines whether waveform acquisition can be started. Although not shown, in the warm state, the cooler temperature Tc is also in the temperature range. During the normal mode period F0, the control device 5 periodically acquires the vehicle speed Vs, the element temperature Tigbt, and the cooler temperature Tc, and whether or not it is suitable for acquiring the waveform information of the energization current Ic each time. Make a decision.

  Once in the stop period F1, the vehicle is stopped, and the semiconductor device 1 is in a stop state (non-energized state). As shown in FIG. 2C, the element temperature Tigbt is stabilized within a certain range in the vicinity of the temperature according to the cooler temperature Tc because the semiconductor device 1 that is not energized does not generate heat. When it is determined that the vehicle speed Vs, the element temperature Tigbt, and the cooler temperature Tc, which are regularly acquired by the control device 5 from the normal mode period F0, are suitable for starting the waveform acquisition of the energization current Ic, the measurement period Move to F2. The state suitable for the start of the waveform acquisition is (i) the vehicle speed Vs is 0 (zero), and (ii) the upper limit temperature at which the element temperature Tigbt and the cooler temperature Tc allow the start of waveform acquisition. It is determined that the variation range ΔTigbt of the element temperature Tigbt and the variation range ΔTc of the cooler temperature Tc are lower (stable) than the reference value T0 and (iii) in a predetermined period. This is a state. If it is not determined that the state is suitable for obtaining the waveform of the energization current Ic, the control device 5 continues to periodically obtain the vehicle speed Vs, the element temperature Tigbt, and the cooler temperature Tc, and shifts to the measurement period F2. do not do.

  In the subsequent measurement period F2, the control device 5 first performs a process of acquiring a reference current waveform of the energization current Ic. In this process, the heat generation in the semiconductor region R due to the energization of the IGBT 1a becomes uniform without depending on the bonding state between the IGBT 1a and the cooler, that is, a heat dissipation transient heat region is generated in which thermal diffusion does not reach the cooler. The control device 5 applies, to the IGBT 1a, a specified pulse (first pulse) M1 whose length is set so as to generate an energized state in which heat dissipation is confined in the transient heat region, a specified number of times. The control device 5 acquires the waveform information of the energization current Ic every time the specified pulse M1 is applied (reference current waveform). When a prescribed time has elapsed from the end of application of the prescribed pulse M1, the control device 5 applies the prescribed pulse (second pulse) M2 to the IGBT 1a a prescribed number of times. The length of the specified pulse M2 is that the generated heat reaches the cooler sufficiently with respect to the heat generation of the semiconductor region R due to the energization of the IGBT 1a, and the cooling is partially depending on the joining state between the IGBT 1a and the cooler. It is set so as to be insufficient, that is, partial overheating can occur. By applying the prescribed pulse M2 having the length, an energized state in which heat dissipation becomes a so-called steady heat region is generated. The control device 5 acquires waveform information of the energization current Ic (heat generation current waveform) each time the specified pulse M2 is applied. At this time, as indicated by the alternate long and short dash line in FIG. 4, if there is a period ta in which the waveform g has a distortion dg, it can be seen that partial overheating has occurred. The distortion dg occurs as a distorted portion in the direction in which the current value increases. The control device 5 determines the magnitude of the distortion dg based on the previously acquired reference current waveform. The magnitude of the distortion dg is calculated as a difference ΔI between the waveform of the distortion dg and the reference current waveform in the period ta. The method for defining the difference ΔI may be arbitrary, for example, the maximum current value difference between both waveforms in the period ta. If the difference ΔI exceeds the threshold value, the control device 5 determines that partial overheating has occurred in the semiconductor region R.

  In the subsequent output restriction mode period F3, the vehicle travels again. The control device 5 suppresses heat generation by controlling the driving of each IGBT 1a in the output restriction mode. In the output restriction mode, for example, control for restricting the load factor is performed in the same manner as when the element temperature Tigbt is equal to or higher than the threshold temperature Tth. Although not shown in the example of FIG. 2, even in the normal mode period F0, the transition to the output restriction mode is performed when Tigbt ≧ Tth.

  Next, a processing procedure executed by the control device 5 will be described with reference to the flowchart of FIG. The processing procedure is such that a computer provided in the control device 5 reads out and executes a program stored in the storage medium, or hardware built in the control device 5 is connected to the storage medium as necessary. It is executed with data input / output.

  FIG. 5 shows a series of flowcharts from determination of whether or not waveform acquisition by the control device 5 is performed, reference current waveform acquisition, exothermic current waveform acquisition, and partial overheating determination. In the following, it is assumed that the processing is periodically started every time the vehicle power source is turned on. When the vehicle power is turned on, first, in step S101, the control device 5 sets the control to the normal mode, and proceeds to S102, which is a basic condition confirmation step for shifting to the normal mode continuation and the IGBT overheat detection measurement.

  Next, in step S102, the control device 5 compares the element temperature Tigbt with the threshold temperature Tth in order to determine whether or not to continue the normal mode and whether or not to shift to the IGBT overheat detection measurement. If Tigbt <Tth, it is determined that the normal mode can be continued and the transition to the IGBT overheat detection measurement is possible, and the process proceeds to step S103. If Tigbt ≧ Tth, the process proceeds to step S112 and this flow ends.

  Next, in step S103, the control device 5 determines whether or not the vehicle speed Vs is 0, that is, whether or not the vehicle is stopped. If Vs = 0, the process proceeds to step S104, and if Vs = 0, the process returns to step S102. In step S104, the control device 5 compares the acquired cooler temperature Tc and element temperature Tigbt with the reference temperature T0 described in FIG. If Tc <T0 and Tigbt <T0, the semiconductor device 1 is in a temperature range suitable for the IGBT overheat detection measurement, and the process proceeds to step S105. If Tc ≧ T0 or Tigbt ≧ T0, it is determined that the IGBT overheat detection measurement is impossible, and the process returns to step S102. In step S105, the control device 5 acquires the element temperature Tigbt and the cooler temperature Tc a plurality of times during a predetermined time interval, and determines whether or not the fluctuation ranges ΔTigbt and ΔTc are within the predetermined width ΔT1. If ΔTigbt <ΔT1 and ΔTc <ΔT1, it is determined that IGBT overheat detection measurement is possible, and the process proceeds to step S106. If ΔTigbt ≧ ΔT1 or ΔTc ≧ ΔT1, it is determined that the IGBT overheat detection measurement is not possible, and the process returns to step S102.

  In step S106, the control device 5 controls the drive device 2 so as to apply the specified pulse M1 to each IGBT 1a. In subsequent step S107, the control device 5 obtains information on the energization current Ic input from the current sensor 3 at a constant time interval, and obtains a waveform of the change in energization current Ic over time. The control device 5 thus acquires the reference current waveform data and stores it in the storage medium. In subsequent step S108, the control device 5 controls the drive device 2 so as to apply the specified pulse M2 to each IGBT 1a. In subsequent step S109, the control device 5 obtains information on the energization current Ic input from the current sensor 1 at regular time intervals, and obtains a waveform of the change in energization current Ic over time. In step S110, the control device 5 compares the acquired current waveform data with the reference current waveform data read from the storage medium. Next, in step S111, the control device 5 determines whether or not the difference ΔI between both waveforms exceeds the threshold value Ifail. If ΔI> Ifail, the process proceeds to step S112, and if ΔI ≦ Ifail, the process returns to step S102. The fact that ΔI> Ifail corresponds to the occurrence of the distortion dg in FIG.

  In step S112, the control device 5 sets the control of each IGBT 1a to the output restriction mode. Moreover, while performing control which shows failure prediction with a vehicle interior indicator, or urges the vehicle to be repaired, notification to the user is performed, and this flow ends.

[Effects of the embodiment, etc.]
According to the present embodiment, in a temperature range lower than the reference temperature T0, a plurality of IGBTs 1a in a state suitable for waveform acquisition of the energization current Ic in which the temperature variation is smaller than the predetermined width ΔT1 are regulated. Driven by a pulse (driven by the specified pulse M2 following the drive by the specified pulse M1), the waveform of the time variation of the energization current Ic in each is obtained. By comparing the respective waveforms and detecting the difference, occurrence of partial overheating in which a part of the IGBT 1a is in an overheated state is detected. Since the IGBT 1a has a temperature characteristic in which the magnitude of the operation threshold voltage is negative, the occurrence of partial overheating in the semiconductor region R causes a specific change from the reference current waveform in the waveform of the energized current. Therefore, by detecting the difference between the current waveform in the steady heat region and the reference current waveform, it can be determined whether or not a change specific to the waveform has occurred, and the occurrence of partial overheating can be detected. As described above, it is possible to provide an abnormality detection method for a semiconductor device that can detect that some semiconductor elements are in an overheated state.

  The present invention is applicable to a system including an inverter as well as a vehicle system.

1 Semiconductor Device 1a IGBT
2 Drive device 3 Current sensor 4 Temperature sensor 5 Control device C Collector terminal E Emitter terminal F0 Normal mode period F1 Temporary stop period F2 Measurement period F3 Output limit mode period df, dg Distortion g Waveform ΔI Difference Ifail Threshold M1, M2 Specified pulse R Semiconductor region ΔT1 Predetermined value Tigbt Element temperature T0 Reference temperature Tth Threshold temperature Tc Cooler temperature ta Period U Unit cell Vs Vehicle speed Vth0, Vth1 Gate threshold voltage

Claims (1)

A method for detecting an abnormality in a semiconductor device, which includes a plurality of semiconductor elements having negative temperature characteristics with a magnitude of an operating threshold voltage, and outputs an energized current obtained by combining currents flowing through the plurality of semiconductor elements,
A first pulse that generates an energized state in which the heat dissipation of the plurality of semiconductor elements is within a transient heat region when the temperature change is within a predetermined value within a predetermined temperature range and for a predetermined time. Obtaining a first waveform which is a waveform of time change of the energized current detected when driven by
Obtaining a second waveform that is a time-varying waveform of the energization current detected when the plurality of semiconductor elements are driven with a second pulse that generates an energization state in which heat dissipation becomes a steady heat region;
A method for detecting an abnormality of a semiconductor device, comprising: detecting a difference between the second waveform and the first waveform to detect that a part of the plurality of semiconductor elements is in an overheated state.

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