Lifetime assessment device, semiconductor device, and lifetime assessment method,

Abstract

To provide a technology with which, while suppressing decline in accuracy of diagnosis regarding lifetime of a power semiconductor element, it is possible to suppress a data volume of aggregate data indicating the number of times a temperature cycle has occurred in each of a plurality of temperature divisions.SOLUTION: A control circuit 80 comprises: a waveform count unit 804 for aggregating, with respect to a cycle temperature difference ΔTj occurring in a temperature cycle of a power semiconductor element 100 mounted to an electricity converter 1, the number of times a temperature cycle has occurred in each of a plurality of temperature divisions for aggregation extending over a target temperature range; a diagnosis table creation unit 806 for estimating the number of times a temperature cycle has occurred in each of the plurality of temperature divisions for diagnosis extending over the target temperature range, the table being constituted by dividing at least some of the plurality of temperature divisions for aggregation into two or more, on the basis of the tendency of distribution of occurrence counts of temperature cycle in each of the plurality of temperature divisions for aggregation; and a lifetime diagnosis unit 808 for performing diagnosis regarding lifetime of the power semiconductor element 100, on the basis of lifetime data 807 and the occurrence counts of temperature cycle in each of the plurality of temperature divisions for diagnosis.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present disclosure relates to a life assessment device and the like. [Background technology]

[0002] A technology is known that performs diagnosis regarding the life of a power semiconductor element based on the temperature difference (hereinafter, "cycle temperature difference") for each cycle of increase and decrease in temperature of the power semiconductor element (hereinafter, "temperature cycle") and life characteristic data of the power semiconductor element (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5343901 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, there are cases where the number of occurrences of temperature cycles is tallied for each of a plurality of temperature divisions over a predetermined temperature range of cycle temperature difference, and the lifespan of power semiconductor elements is diagnosed from the number of occurrences of temperature cycles for each of the plurality of temperature divisions. In this case, it is possible to diagnose the lifespan of the power semiconductor elements, and also to retroactively analyze and verify the history of the number of occurrences of temperature cycles for each of the plurality of temperature divisions.

[0005] However, if the granularity of the multiple temperature sections is set finely, the amount of data for the tabulated data on the number of temperature cycle occurrences becomes relatively large, and there is a possibility that the data cannot be stored in a storage area prepared in advance.

[0006] On the other hand, if the granularity of the multiple temperature sections is set coarsely so that they can be stored in a pre-prepared storage area, the intervals between the temperature sections will become wider, which may reduce the accuracy of diagnosis regarding the life of the power semiconductor elements.

[0007] In view of the above problems, an object of the present invention is to provide a technology that can reduce the amount of aggregated data on the number of temperature cycles occurring for each of a plurality of temperature ranges while suppressing a decrease in the accuracy of diagnosis regarding the lifespan of power semiconductor elements. [Means for solving the problem]

[0008] In order to achieve the above object, in one embodiment of the present disclosure, a temperature acquisition unit that acquires an internal temperature of a power semiconductor element mounted on the semiconductor device; a counting unit that detects a temperature cycle consisting of an increase and decrease in temperature caused by an operation of the power semiconductor element based on a change in temperature acquired by the temperature acquisition unit, and counts the number of occurrences of the temperature cycle for each of a plurality of first sections over a predetermined temperature range for a cycle temperature difference corresponding to a change width of the increase and decrease in temperature occurring in the temperature cycle; an estimation unit that estimates the number of occurrences of the temperature cycle for each of a plurality of second divisions across the predetermined temperature range, the second divisions being configured by dividing at least a portion of the plurality of first divisions into two or more, based on a distribution tendency of the number of occurrences of the temperature cycle for each of the plurality of first divisions tallied by the talliation unit; and a life diagnosis unit that performs a diagnosis regarding the life of the power semiconductor element based on characteristic data indicating a correspondence relationship between the cycle temperature difference and the life of the power semiconductor element and the number of occurrences of the temperature cycle for each of the plurality of second divisions. A life assessment device is provided.

[0009] In another embodiment of the present disclosure, A device equipped with the above-mentioned life assessment device. A semiconductor device is provided.

[0010] In another embodiment of the present disclosure, A lifespan assessment method executed by a lifespan assessment device, comprising: a temperature acquiring step of acquiring an internal temperature of a power semiconductor element mounted on the semiconductor device; a counting step of detecting a temperature cycle constituted by an increase and decrease in the temperature caused by an operation of the power semiconductor element based on the change in temperature acquired in the temperature acquiring step, and counting the number of occurrences of the temperature cycle for each of a plurality of first sections over a predetermined temperature range for a cycle temperature difference corresponding to a change width of the increase and decrease in the temperature occurring in the temperature cycle; an estimation step of estimating the number of occurrences of the temperature cycle for each of a plurality of second divisions over the predetermined temperature range, the second divisions being configured by dividing at least a part of the plurality of first divisions into two or more, based on a distribution tendency of the number of occurrences of the temperature cycle for each of the plurality of first divisions tallied in the tallied step; and a lifetime diagnosis step of diagnosing the lifetime of the power semiconductor element based on characteristic data indicating a correspondence relationship between the cycle temperature difference and the lifetime of the power semiconductor element and the number of occurrences of the temperature cycle for each of the plurality of second divisions. A method for assessing a lifetime is provided. Effect of the Invention

[0011] According to the above-described embodiment, it is possible to reduce the amount of data collected on the number of occurrences of temperature cycles for each of a plurality of temperature ranges while suppressing a decrease in the accuracy of diagnosis regarding the life span of power semiconductor elements. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram illustrating an example of a configuration of a power conversion device. [Diagram 2] FIG. 1 is a diagram illustrating an example of an internal structure of a power semiconductor. [Diagram 3] FIG. 2 is a functional block diagram showing an example of a configuration of a control circuit related to a life diagnosis function. [Figure 4] FIG. 1 is a diagram showing an example of a change in the internal temperature (junction temperature) of a power semiconductor. [Diagram 5] FIG. 13 is a diagram showing an example of a temperature cycle history table for aggregation. [Figure 6]FIG. 13 is a diagram showing an example of a frequency distribution of temperature cycles based on a compilation temperature cycle history table. [Figure 7] FIG. 13 is a diagram showing an example of a diagnostic temperature cycle history table. [Figure 8] FIG. 13 is a diagram showing an example of a frequency distribution of temperature cycles based on a diagnostic temperature cycle history table. [Figure 9] FIG. 13 is a diagram showing an example of a power cycle characteristic. [Figure 10] FIG. 11 is a diagram showing an example of the relationship between the temperature divisions for aggregation and the power cycle life. [Figure 11] 13 is a diagram illustrating an example of a method for calculating the number of occurrences of temperature cycles for each of a plurality of diagnostic temperature sections in a diagnostic temperature cycle history table. FIG. [Figure 12] 13 is a diagram showing an example of a calculation result of the number of occurrences of temperature cycles for each of a plurality of diagnostic temperature sections in a diagnostic temperature cycle history table. FIG. [Figure 13] FIG. 13 is a diagram showing another example of the calculation results of the number of occurrences of temperature cycles for each of a plurality of diagnostic temperature sections in the diagnostic temperature cycle history table. [Figure 14] 13 is a diagram illustrating another example of a method for calculating the number of occurrences of temperature cycles for each of a plurality of diagnostic temperature sections in the diagnostic temperature cycle history table. FIG. [Figure 15] FIG. 13 is a diagram showing yet another example of the calculation results of the number of occurrences of temperature cycles for each of a plurality of diagnostic temperature sections in the diagnostic temperature cycle history table. [Figure 16] FIG. 13 is a diagram showing yet another example of the calculation results of the number of occurrences of temperature cycles for each of a plurality of diagnostic temperature sections in the diagnostic temperature cycle history table. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment will be described with reference to the drawings.

[0014] [Power conversion device configuration] First, with reference to FIG. 1, the configuration of a power conversion device 1 according to this embodiment will be described.

[0015] FIG. 1 is a diagram showing an example of the configuration of a power conversion device 1 according to this embodiment.

[0016] The power conversion device 1 (an example of a semiconductor device) converts three-phase AC power (e.g., R phase, S phase, and T phase) input from a commercial power source PS into three-phase AC power (e.g., U phase, V phase, and W phase) having a predetermined voltage and a predetermined frequency, and drives an electric motor EM.

[0017] The power conversion device 1 includes a rectifier circuit 10, a smoothing circuit 20, an inverter circuit 30, a current sensor 40, a voltage sensor 50, a temperature sensor 60, a gate drive circuit 70, a control circuit 80, and a display unit 90.

[0018] The rectifier circuit 10 is configured to be capable of rectifying three-phase AC power input from a commercial power source PS and outputting DC power. The rectifier circuit 10 has positive and negative output terminals connected to one end of a positive line PL and a negative line NL, respectively, and can output DC power to the smoothing circuit 20 through the positive line PL and the negative line NL. The rectifier circuit 10 is, for example, a bridge-type full-wave rectifier circuit including six semiconductor diodes SD (an example of a power semiconductor element) and in which three sets of series-connected bodies of two semiconductor diodes SD constituting upper and lower arms are connected in parallel.

[0019] The smoothing circuit 20 suppresses and smoothes pulsations in the DC power output from the rectifier circuit 10 and the DC power regenerated from the inverter circuit 30 .

[0020] The smoothing circuit 20 includes, for example, a smoothing capacitor 21 .

[0021] The smoothing capacitor 21 may be provided in parallel with the rectifier circuit 10 and the inverter circuit 30 in a path connecting the positive line PL and the negative line NL.

[0022] The smoothing capacitor 21 smoothes the DC power output from the rectifier circuit 10 and the DC power output (regenerated) from the inverter circuit 30 while repeatedly charging and discharging as appropriate.

[0023] There may be only one smoothing capacitor 21. Alternatively, a plurality of smoothing capacitors 21 may be disposed, and the plurality of smoothing capacitors 21 may be connected in parallel or in series between the positive line PL and the negative line NL. Alternatively, the plurality of smoothing capacitors 21 may be configured in such a way that a series connection of two or more smoothing capacitors is connected in parallel between the positive line PL and the negative line NL.

[0024] Moreover, the smoothing circuit 20 may include, for example, a reactor.

[0025] The reactor may be provided in the positive line PL between the rectifier circuit 10 and the smoothing capacitor 21 (specifically, the branch point from the path in which the smoothing capacitor 21 is disposed).

[0026] The reactor smoothes the DC power output from the rectifier circuit 10 and the DC power output (regenerated) from the inverter circuit 30 while appropriately generating a voltage to prevent a change in the current.

[0027] The inverter circuit 30 has positive and negative input terminals connected to the other terminals of the positive line PL and the negative line NL. The inverter circuit 30 converts the DC power supplied from the smoothing circuit 20 into three-phase AC power (e.g., U phase, V phase, and W phase) having a predetermined frequency and a predetermined voltage by a switching operation of a semiconductor switch SW (an example of a power semiconductor element), and outputs the power to the electric motor EM. The semiconductor switch SW may be, for example, an IGBT (Insulated Gate Bipolar Transistor) or a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) made of silicon (Si). The semiconductor switch SW may also be, for example, a semiconductor element using a wide band gap semiconductor such as silicon carbide (SiC) or gallium nitride (GaN).

[0028] The inverter circuit 30 includes, for example, six semiconductor switches SW, and is configured to include a bridge circuit in which three sets of series-connected bodies (switch legs) of two semiconductor switches SW constituting upper and lower arms are connected in parallel between a positive line PL and a negative line NL. The inverter circuit 30 may output three-phase AC power through three output lines drawn from the connection points of the three sets of upper and lower arms. A free wheel diode may be connected in parallel to each of the six semiconductor switches SW.

[0029] Hereinafter, the power semiconductor elements mounted on the power conversion device 1, such as the semiconductor diode SD of the rectifier circuit 10 and the semiconductor switch SW of the inverter circuit 30, may be collectively referred to as the "power semiconductor element 100", or any one of them may be referred to individually.

[0030] The current sensor 40 detects the current of each of the three-phase (three wires) output lines of the power conversion device 1, i.e., the current of each of the three phases of the electric motor EM. The current sensor 40 outputs a signal corresponding to the current value of each of the three phases of the electric motor EM, and the output signal of the current sensor 40 is input to the control circuit 80.

[0031] The voltage sensor 50 detects the voltage (DC link voltage) between the positive line PL and the negative line NL of the power conversion device 1. The voltage sensor 50 outputs a signal corresponding to the voltage value between the positive line PL and the negative line NL, and the output signal of the voltage sensor 50 is input to the control circuit 80.

[0032] The temperature sensor 60 outputs a detection signal related to the internal temperature of the power semiconductor device 100. The detection signal output from the temperature sensor 60 is input to the control circuit 80.

[0033] The temperature sensor 60 detects, for example, a temperature for estimating an internal temperature of the power semiconductor element 100. The temperature sensor 60 may be mounted, for example, on a housing of the power conversion device 1 or a cooling fin for cooling the power semiconductor element 100, and detect the temperatures of the housing of the power conversion device 1 or the cooling fin.

[0034] Further, the temperature sensor 60 may be configured to directly detect the internal temperature of the power semiconductor element 100, for example.

[0035] The gate drive circuit 70, under the control of the control circuit 80, outputs drive signals for switching (ON / OFF) the six semiconductor switches SW of the inverter circuit 30 to the gate terminals of each of the six semiconductor switches SW.

[0036] The control circuit 80 (an example of a lifespan assessment device) controls the power conversion device 1.

[0037] The functions of the control circuit 80 may be realized by any hardware or any combination of hardware and software.

[0038] The control circuit 80 is mainly composed of a computer including, for example, a central processing unit (CPU), a memory device such as a random access memory (RAM), a non-volatile auxiliary storage device such as a read only memory (ROM), and an interface device for input and output with the outside. The control circuit 80 performs various controls by loading a program installed in the auxiliary storage device into the memory device and having the CPU execute the program. The control circuit 80 also receives external signals and outputs (transmits) signals to the outside through the interface device.

[0039] The control circuit 80 controls the inverter circuit 30 so that the electric motor EM operates under a predetermined operating condition, for example. Specifically, the control circuit 80 may output a control signal to the gate drive circuit 70, thereby outputting a drive signal such as a PWM (Pulse Width Modulation) signal to the semiconductor switch SW via the gate drive circuit 70, thereby controlling the inverter circuit 30.

[0040] Furthermore, the control circuit 80 performs, for example, processing related to a life diagnosis function of the power semiconductor elements 100 mounted on the power conversion device 1. The life diagnosis function will be described in detail later.

[0041] The display unit 90 displays information about the power conversion device 1 to a user (e.g., a worker in a factory where a driven device electrically driven by the electric motor EM is installed) under the control of the control circuit 80. The display unit 90 includes, for example, a warning light, an electronic bulletin board, a liquid crystal display, an organic EL (Electroluminescence) display, etc.

[0042] [Outline of lifespan diagnosis function for power semiconductor elements] Next, the life diagnosis function of the control circuit 80 for the power semiconductor element 100 (semiconductor diode SD, semiconductor switch SW, etc.) will be described with reference to FIGS.

[0043] FIG. 2 is a diagram showing an example of the internal structure of the power semiconductor element 100. FIG. 3 is a functional block diagram showing an example of the configuration of a control circuit 80 related to a life diagnosis function. FIG. 4 is a diagram showing an example of a change in the internal temperature (junction temperature Tj) of the power semiconductor element 100. FIG. 5 is a diagram showing an example of a compilation temperature cycle history table 805. FIG. 6 is a diagram showing an example of a frequency distribution of temperature cycles based on the compilation temperature cycle history table 805. FIG. 7 is a diagram showing an example of a diagnostic temperature cycle history table. FIG. 8 is a diagram showing an example of a frequency distribution of temperature cycles based on the diagnostic temperature cycle history table. FIG. 9 is a diagram showing an example of a power cycle characteristic. FIG. 10 is a diagram showing an example of a relationship between compilation temperature divisions and power cycle life (power cycle characteristic).

[0044] It should be noted that the vertical axis (power cycle life) in Figures 9 and 10 is expressed in a logarithmic scale, as is the case with Figures 11 and 14 described below.

[0045] As shown in FIG. 2, the power semiconductor element 100 includes, for example, a semiconductor chip 101, a wire 102 joined onto the semiconductor chip 101, an insulating substrate 103 on which the semiconductor chip 101 is mounted, and a base substrate 104 on which the insulating substrate 103 is mounted.

[0046] For example, in the power semiconductor element 100 such as a semiconductor switch SW, switching loss occurs due to repetition of ON / OFF operation, and the semiconductor chip 101 heats up. In addition, for example, in the power semiconductor element 100, resistance loss occurs due to an internal resistance component when current is applied, and the semiconductor chip 101 heats up. Therefore, thermal fatigue accumulates in the joint between the insulating substrate 103 and the semiconductor chip 101 (dotted line part in the figure), the joint between the wire 102 and the semiconductor chip 101, and the like, due to repetition of a temperature cycle (power cycle) consisting of the heat generation of the semiconductor chip 101 and the rise and fall of temperature accompanying the subsequent cooling. Then, when the temperature cycle is repeated to a certain extent and the degree of thermal fatigue accumulates to a certain extent, the joint between the insulating substrate 103 and the semiconductor chip 101, the joint between the wire 102 and the semiconductor chip 101, and the like are destroyed by thermal stress, and the power semiconductor element 100 reaches the end of its life.

[0047] Therefore, the control circuit 80 performs diagnosis regarding the life of the power semiconductor element 100 by monitoring the repetition of temperature cycles accompanying the operation of the power semiconductor element 100. The diagnosis regarding the life of the power semiconductor element 100 includes prediction of the life of the power semiconductor element 100 (for example, a judgment as to whether the life has been reached or not, and a prediction of the remaining life, i.e., remaining life, etc.).

[0048] The control circuit 80 may, for example, perform a diagnosis regarding the lifetime of each of the target power semiconductor elements 100 among the power semiconductor elements 100 mounted in the power conversion device 1. The power semiconductor elements 100 targeted for the lifetime diagnosis may be all of the power semiconductor elements 100 mounted in the power conversion device 1, or may be a part of them.

[0049] 3, the control circuit 80 includes a temperature acquisition unit 801, a peak / valley detection unit 802, a stack table 803, a waveform counting unit 804, and a temperature cycle history table for aggregation 805. The control circuit 80 also includes a diagnosis table creation unit 806, life data 807, a life diagnosis unit 808, and a life integration buffer 809.

[0050] The temperature acquisition unit 801 acquires the internal temperature of the power semiconductor element 100 at each predetermined control period based on the output signal of the temperature sensor 60. The temperature acquisition unit 801 acquires, for example, the temperature Tj of the junction between the insulating substrate 103 and the semiconductor chip 101 (hereinafter referred to as the "junction temperature").

[0051] For example, when the temperature of the housing, cooling fins, etc. of the power conversion device 1 is detected by the temperature sensor 60, the temperature acquisition unit 801 estimates the junction temperature Tj of the power semiconductor element 100 based on the output signal of the temperature sensor 60. That is, the temperature acquisition unit 801 may acquire an estimated value of the junction temperature Tj of the power semiconductor element 100 based on the output signal of the temperature sensor 60. Specifically, the temperature acquisition unit 801 may estimate the loss of the power semiconductor element 100 based on the output signals of the current sensor 40 and the voltage sensor 50 and the electrical characteristics (for example, characteristics of an electrical resistance component) of the power semiconductor element 100. Then, the temperature acquisition unit 801 may estimate the junction temperature Tj based on the estimated loss of the power semiconductor element 100, the temperatures of the housing, cooling fins, etc. detected by the temperature sensor 60, and the thermal resistance between the power semiconductor element 100 and the housing, cooling fins, etc. The electrical characteristics of the power semiconductor element 100 and the thermal resistance between the power semiconductor element 100 and the housing or the cooling fins, etc., may be specified in advance, for example, through experiments or simulations, and data relating to these may be stored in advance in an auxiliary storage device of the control circuit 80, etc.

[0052] Furthermore, for example, when the internal temperature of the power semiconductor device 100 is directly detected by the temperature sensor 60, the temperature acquisition unit 801 acquires the detection value of the junction temperature Tj directly from the output signal of the temperature sensor 60.

[0053] The peak / valley detection unit 802 detects a peak (peak or valley) in the time change of the junction temperature Tj based on the junction temperature Tj successively acquired by the temperature acquisition unit 801.

[0054] 4, for example, the junction temperature Tj of the power semiconductor element 100 changes over time depending on the operating state of the power semiconductor element 100. Specifically, as described above, when a loss occurs in the power semiconductor element 100, the junction temperature Tj rises, and when the power semiconductor element 100 subsequently transitions to a loss-free state, the junction temperature Tj drops. As the junction temperature Tj of the power semiconductor element 100 repeatedly rises and falls with the operation of the power semiconductor element 100, peaks (parts indicated by dotted arrows in the figure) and valleys (parts indicated by hollow arrows in the figure) appear in the time change of the junction temperature Tj. The peak-valley detection unit 802 detects such peaks that occur in the time change of the junction temperature Tj.

[0055] Specifically, the peak / valley detection unit 802 monitors the change over time of the junction temperature Tj successively acquired by the temperature acquisition unit 801, and detects the point of change (peak) where the junction temperature Tj changes from increasing to decreasing or the point of change (valley) where the junction temperature Tj changes from decreasing to increasing.

[0056] The stack table 803 is stored, for example, in a memory device or an auxiliary storage device of the control circuit 80. In the stack table 803, values ​​of the junction temperature Tj of the peak portions (peaks or valleys) detected by the peak-valley detection unit 802 (hereinafter, "peak values") are recorded in chronological order.

[0057] The waveform counting unit 804 (an example of a counting unit) counts (detects) the temperature cycles (power cycles) of the power semiconductor element 100 based on the peak values ​​of the junction temperature Tj recorded in chronological order in the stack table 803. For example, the waveform counting unit 804 may execute a process of counting (detecting) the temperature cycles of the power semiconductor element 100 every time the stack table 803 is updated.

[0058] The waveform counting unit 804 may arbitrarily apply a known method (e.g., maximum-minimum method, maximum-minimum method, amplitude method, level crossing method, range pair method, rainflow method, etc.) to the data in the stack table 803 to count the temperature cycles of the power semiconductor element 100. The waveform counting unit 804 outputs the change width (amplitude) ΔTj of the junction temperature Tj in the detected temperature cycle (hereinafter, "cycle temperature difference").

[0059] The waveform counting section 804 records the history of the cycle temperature difference ΔTj of the temperature cycle in a compilation temperature cycle history table 805 based on the cycle temperature difference ΔTj of the detected temperature cycle.

[0060] The tallying temperature cycle history table 805 is stored in, for example, an auxiliary storage device of the control circuit 80. As described above, the tallying temperature cycle history table 805 records the history of the cycle temperature difference ΔTj for each temperature cycle detected by the waveform counting unit 804. Specifically, the tallying temperature cycle history table 805 records the number of occurrences of temperature cycles for each of a plurality of temperature sections (hereinafter, "temperature sections for tallying") (an example of a first section) that divide a predetermined temperature range (hereinafter, "target temperature range") at predetermined temperature intervals (an example of a first interval). The target temperature range is a range defined by an upper limit value and a lower limit value of the temperature range in which the cycle temperature difference ΔTj is expected to occur. The target temperature range is, for example, a range of 0°C to 120°C.

[0061] For example, as shown in FIG. 5, the temperature cycle history table 805 for aggregation has 24 temperature divisions TA1 to TA 24 In addition, the temperature cycle history table 805 for compilation has temperature divisions TA1 to TA 24 For each, the number of occurrences is NA1 to NA 24 is recorded.

[0062] The range of cycle temperature difference (temperature range) for each temperature division for aggregation in FIG. 5 may be specified, for example, in a mode including the lower limit value and excluding the upper limit value (lower limit value≦temperature range<upper limit value).

[0063] Each time a temperature cycle is detected, the waveform counting unit 804 increments by 1 the number of occurrences of the tallying temperature section including the cycle temperature difference ΔTj of the detected temperature cycle, thereby recording the history of the cycle temperature difference ΔTj in the tallying temperature cycle history table 805. For example, when a temperature cycle with a cycle temperature difference ΔTj of 22.5° C. is detected, the number of occurrences NA5 of the tallying temperature section TA5 (20° C.≦ΔTj<25° C.) is incremented by 1.

[0064] 6, the tallying temperature cycle history table 805 is expressed as a graph of a frequency distribution of the number of occurrences (occurrence frequency) of temperature cycles for each of a plurality of tallying temperature sections corresponding to the cycle temperature difference ΔTj. This allows the control circuit 80 to analyze, for example, the relationship between the occurrence status of cycle temperature differences in the power semiconductor element 100 and the operating status of the power conversion device 1 based on the tallying temperature cycle history table 805 and the history data related to the operating status of the power conversion device 1.

[0065] Returning to Fig. 3, the diagnostic table creation unit 806 (an example of an estimation unit) creates a diagnostic temperature cycle history table (hereinafter, "diagnostic temperature cycle history table") based on the tabulation temperature cycle history table 805. Specifically, the diagnostic temperature cycle history table specifies the number of occurrences of temperature cycles for each of a plurality of temperature categories (hereinafter, "diagnostic temperature categories") (an example of second categories) spanning the target temperature range, which are relatively finer in granularity than the plurality of tabulation temperature categories. The plurality of diagnostic temperature categories are configured by dividing the target tabulation temperature range into two or more categories for each of the plurality of tabulation temperature ranges.

[0066] The diagnostic table creation unit 806 estimates the number of occurrences of temperature cycles for each of the multiple diagnostic temperature sections based on the number of occurrences for each of the multiple tallying temperature sections. Specifically, the diagnostic table creation unit 806 estimates the number of occurrences of temperature cycles for each of the multiple diagnostic temperature sections in a manner that distributes the number of occurrences of a target temperature section for each of the multiple tallying temperature sections to two or more diagnostic temperature sections included in the target temperature section. Details of the method of estimating the number of occurrences of temperature cycles for each of the multiple diagnostic temperature sections will be described later.

[0067] For example, as shown in FIG. 7, the diagnostic temperature cycle history table includes a plurality of diagnostic temperature divisions TB1 to TB2 that divide the target temperature range in 1° C. increments based on the tabulation temperature cycle history table 805 of FIG. 120 Number of temperature cycles occurring per NB1~NB 120 In other words, in this example, a plurality of temperature divisions for aggregation TA p For each (p: any integer between 1 and 24), the target temperature classification TA p 5 diagnostic temperature ranges in 1°C increments 5(p-1)+1 ~TB 5(p-1)+5 By dividing the temperature into multiple diagnostic temperature ranges, q (q: an integer between 1 and 120) is specified. Then, multiple temperature divisions for aggregation TA p For each temperature category TA p Number of occurrences: NA p The target temperature category TA p The five diagnostic temperature ranges included in TB 5(p-1)+1 ~TB 5(p-1)+5 Number of occurrences per NB 5(p-1)+1 ~NB 5(p-1)+5 As a result, the diagnosis table creation unit 806 creates a plurality of diagnosis temperature divisions TB q Number of occurrences per NB q A relatively fine-grained diagnostic temperature cycle history table can be created that includes:

[0068] For example, as shown in Fig. 8, the diagnostic temperature cycle history table is expressed as a graph of a frequency distribution of the number of occurrences (occurrence frequency) of temperature cycles for each of a plurality of diagnostic temperature sections corresponding to the cycle temperature difference ΔTj. The frequency distribution graph corresponding to the diagnostic temperature cycle history table has finer granularity with respect to the cycle temperature difference ΔTj than the frequency distribution graph corresponding to the aggregation temperature cycle history table 805 (Fig. 6). Therefore, for example, by using the diagnostic temperature cycle history table, the control circuit 80 can analyze the relationship between the occurrence status of the cycle temperature difference of the power semiconductor element 100 and the operating status of the power conversion device 1 in more detail.

[0069] The life data 807 is stored, for example, in an auxiliary storage device of the control circuit 80 and is read out to a memory device for use. The life data 807 is data necessary for predicting the life of the power semiconductor element 100. The life data 807 includes, for example, power cycle characteristic data (an example of characteristic data). The power cycle characteristic data is data that represents a correspondence relationship (hereinafter, "power cycle characteristic") between the cycle temperature difference ΔTj of the power semiconductor element 100 and the number of power cycles (temperature cycles) corresponding to the life (hereinafter, "power cycle life"). The power cycle life corresponds to the number of power cycles (temperature cycles) until the power semiconductor element 100 reaches the end of its life when power cycles with a certain cycle temperature difference ΔTj are repeated.

[0070] 9, this example shows power cycle characteristics when the cycle temperature difference ΔTj is in the range of 20° C. to 100° C. The power cycle life of the power semiconductor element 100 is relatively large when the cycle temperature difference ΔTj is relatively small, and exponentially decreases as the cycle temperature difference ΔTj increases.

[0071] In addition, when the power cycle characteristic of FIG. 9 is adopted, the power cycle life of the cycle temperature difference ΔTj in the range of 0° C. to 20° C. may be substituted with, for example, the power cycle life when the cycle temperature difference ΔTj is 20° C. In addition, when the power cycle characteristic of FIG. 9 is adopted, the power cycle life of the cycle temperature difference ΔTj in the range of 0° C. to 20° C. may be specified by, for example, a complementary curve based on a curve representing the power cycle characteristic in the range of 20° C. to 100° C. The same may be true for the power cycle life of the cycle temperature difference ΔTj in the range exceeding 100° C. In addition, the life data 807 may be in a form in which data generated outside the power conversion device 1 is registered in the control circuit 80. In addition, the life data 807 may be generated by the control circuit 80 based on, for example, data of the actual power cycle characteristic obtained by a power cycle test of the power semiconductor element 100. The power cycle test of the power semiconductor element 100 is performed by the manufacturer or user of the power semiconductor element 100.

[0072] 3, the life diagnosis unit 808 performs diagnosis on the life of the power semiconductor element 100. Specifically, the life diagnosis unit 808 applies Miner's rule (linear cumulative damage rule) based on the diagnostic temperature cycle history table and the life data 807. Then, the life diagnosis unit 808 performs prediction on the life of the power semiconductor element 100 by integrating the degree of thermal fatigue of the power semiconductor element 100 for each temperature cycle.

[0073] The life diagnosis unit 808 divides the target temperature range into a predetermined number k of diagnosis temperature sections TB q Number of temperature cycles occurring for each (q=1~k) NB q For example, in the case of FIG. 7 described above, the target temperature range is 0° C. to 120° C., the predetermined temperature interval is 1° C., and the predetermined number k is 120. The cumulative damage value D may be calculated based on the diagnostic temperature range TB q Power cycle life per N q Using this, it is expressed by the following equation (1).

[0074]

number

[0075] The cumulative damage value D is in a range smaller than 1, and the closer it is to 1, the relatively closer it is to the end of its life. When it reaches 1 or more, it indicates that the power semiconductor device 100 has reached the end of its life.

[0076] The life diagnosis unit 808 may, for example, calculate the cumulative damage value D at a predetermined timing (for example, when the power of the power conversion device 1 is turned on or off, etc.) and perform diagnosis regarding the life of the power semiconductor element 100. Furthermore, the life diagnosis unit 808 may also manually calculate the cumulative damage value D in response to, for example, an input from a user and perform diagnosis regarding the life of the power semiconductor element 100.

[0077] For example, when the cumulative damage value D reaches or exceeds a predetermined threshold value (hereinafter, "first threshold value") that is equal to or less than 1, the life diagnosis unit 808 may determine that the power semiconductor element 100 has reached the end of its life. Then, the life diagnosis unit 808 may notify the user of an alert indicating this through the display unit 90. Furthermore, for example, when the cumulative damage value D reaches or exceeds a predetermined threshold value (hereinafter, "second threshold value") that is less than the first threshold value, the life diagnosis unit 808 may determine that the life of the power semiconductor element 100 is nearing the end of its life and that there is a high possibility of a failure occurring. Then, the life diagnosis unit 808 may notify the user of an advance alert before the end of its life through the display unit 90 or the like. The first threshold value is set to, for example, a value relatively close to 1 (for example, 0.95, etc.). Furthermore, the second threshold value may be set in multiple stages, and the level of the advance alert before the end of its life may be raised as the second threshold value of the multiple stages increases.

[0078] The life integration buffer 809 is stored in, for example, a memory device, an auxiliary storage device, etc. The life integration buffer 809 stores data on the diagnosis results of the life of the power semiconductor element 100 calculated by the life diagnosis unit 808 in chronological order. For example, the life integration buffer 809 stores a history of the accumulated damage value D calculated by the life diagnosis unit 808.

[0079] Thus, in this example, the control circuit 80 creates a diagnostic temperature cycle history table with relatively finer granularity regarding the cycle temperature difference ΔTj based on the aggregation temperature cycle history table 805. Then, the control circuit 80 calculates the cumulative damage value D based on the history of the cycle temperature difference ΔTj for each temperature cycle in the diagnostic temperature cycle history table (the history of temperature cycles for each of a plurality of diagnostic temperature sections), and performs a diagnosis regarding the life of the power semiconductor element 100.

[0080] For example, when a temperature range for aggregation with a relatively large temperature span (e.g., 5°C or 10°C increments) is adopted, the number of temperature ranges for aggregation that cover the target temperature range can be relatively reduced. This allows the amount of data in the temperature cycle history table for aggregation 805 to be relatively reduced. Therefore, for example, even if the memory area prepared inside the power conversion device 1 is relatively small, the power conversion device 1 can store the temperature cycle history table for aggregation 805 inside the device.

[0081] On the other hand, in the case of a temperature section for tabulation having a relatively large temperature range, the fluctuation range of the power cycle life within the range of the upper and lower limits of the temperature range is relatively large.

[0082] For example, as shown in Fig. 10, power cycle lives PC1 to PC3 corresponding to the upper limit (30°C), middle (27.5°C), and lower limit (25°C) of the cycle temperature difference ΔTj in the tabulation temperature section TA6 (25°C to 30°C) are shown on the power cycle characteristic PC. As described above, the power cycle life is expressed on a logarithmic scale, and the difference between the power cycle life PC1 corresponding to the upper limit of the cycle temperature difference ΔTj and the power cycle life PC3 corresponding to the lower limit of the cycle temperature difference ΔTj is relatively large.

[0083] Therefore, if a diagnosis of the lifespan of the power semiconductor element 100 were to be performed using the aggregation temperature cycle history table 805, which is compiled based on the aggregation temperature range having a relatively large temperature range, as is, there is a possibility that the accuracy would be relatively reduced.

[0084] In contrast, in this embodiment, a diagnostic temperature cycle history table is created that is defined by a plurality of diagnostic temperature sections that have a smaller temperature range than the tallying temperature sections, and a diagnosis regarding the life of the power semiconductor element 100 is performed based on the diagnostic temperature cycle history table. Therefore, the control circuit 80 can suppress a decrease in accuracy of the diagnosis regarding the life of the power semiconductor element 100 while suppressing a relatively small amount of data in the tallying temperature cycle history table 805.

[0085] Furthermore, in this example, the control circuit 80 can perform a diagnosis process regarding the lifespan of the power semiconductor element 100 at any timing by using the aggregation temperature cycle history table 805. Therefore, the control circuit 80 can perform a diagnosis regarding the lifespan of the power semiconductor element 100 by selectively using a timing that has little effect on the operation of the power conversion device 1, such as when the power supply of the power conversion device 1 is turned on or off.

[0086] [How to create a diagnostic temperature cycle history table] Next, a method for creating a diagnostic temperature cycle history table, i.e., a specific example of a method for estimating the number of temperature cycles occurring for each of a plurality of diagnostic temperature sections, will be described with reference to Figures 11 to 16. In this example, the following mainly describes an example of creating the diagnostic temperature cycle history table of Figure 7 from the aggregation temperature cycle history table 805 of Figure 5 described above.

[0087] <An example of a method for estimating the number of temperature cycles that occur for each diagnostic temperature category> FIG. 11 shows a plurality of diagnostic temperature divisions TB in the diagnostic temperature cycle history table. q Number of temperature cycles per NB q11 is a diagram for explaining an example of a method for calculating the temperature range TB 26 ~TB 30 Number of temperature cycles per NB 26 ~NB 30 12 is a diagram for explaining an example of a calculation method (estimation method) of a plurality of diagnostic temperature sections TB in a diagnostic temperature cycle history table. q Number of temperature cycles per NB q 12 is a diagram showing an example of the calculation result of the temperature range TB 26 ~TB 30 Number of temperature cycles per NB 26 ~NB 30 13 is a diagram showing an example of a calculation result of a plurality of diagnostic temperature sections TB in a diagnostic temperature cycle history table. q Number of temperature cycles per NB q 13 is a diagram showing another example of the calculation result of the temperature range TB6 for the five diagnostic temperature ranges TB 26 ~TB 30 Number of temperature cycles per NB 26 ~NB 30 FIG. 13 is a diagram showing another example of the calculation result.

[0088] As shown in FIG. 11, in this example, the distribution of the number of occurrences of temperature cycles NA5 to NA7 for each of the temperature intervals TA5 to TA7 for calculation has a tendency TD1 that increases uniformly from the small cycle temperature difference ΔTj to the large cycle temperature difference ΔTj. 26 ~NB 30 It is highly likely that the following conditions (1-1) and (1-2) are met.

[0089] (1-1) Number of temperature cycles NB 26 ~NB 30 is the diagnostic temperature category TB included in the tabulation temperature category TA5. 21 ~TB 25 Number of temperature cycles NB 21~NB 25 Greater than.

[0090] (1-2) The five diagnostic temperature ranges TB included in the collection temperature range TA6, which is located between the collection temperature ranges TA5 and TA7. 26 ~TB 30 Number of temperature cycles per NB 26 ~NB 30 increases as the cycle temperature difference ΔTj goes from smaller to larger.

[0091] Therefore, the diagnostic table creation unit 806 selects, based on the condition (1-1), for example, five diagnostic temperature sections TB 21 ~TB 25 Number of temperature cycles NB 21 ~NB 25 The average value (=NA5 / 5) of the above is used as the diagnostic temperature classification TB 26 ~TB 30 In other words, the diagnosis table creation unit 806 allocates a number corresponding to the number of occurrences of temperature cycles NA5 in the tabulation temperature section TA5 from the number of occurrences of temperature cycles NA6 in the tabulation temperature section TA6 to the diagnosis temperature section TB 26 ~TB 30 Distribute equally among them.

[0092] Based on the conditions in (1-1), the occurrence frequency NA6 of the aggregation temperature category TA6 is set to the diagnosis temperature category TB 26 ~TB 30 For convenience, the form of distribution based on the condition (2-1), distribution based on the condition (3-2) or (3-3), and distribution based on the condition (4-2) or (4-3) described below are also referred to as the "base distribution."

[0093] Then, based on the condition (1-2), the diagnostic table creation unit 806 divides the remaining number (=NA6-NA5) of the occurrence number NA6 into the diagnostic temperature division TB 26 ~TB 30 Specifically, the diagnosis table creation unit 806 may allocate the remaining number (=NA6-NA5) of the occurrence number NA6 to the diagnosis temperature division TB 26 ~TB 30 may be distributed to.

[0094] Based on the conditions in (1-2), the number of occurrences of the temperature category TA6 for aggregation NA6 is set to the temperature category TB for diagnosis. 26 ~TB 30 For convenience, the distribution based on the condition (2-2) and the distribution based on the condition (3-1) described below are also referred to as "trend fluctuation distribution."

[0095] As a result, the diagnostic table creation unit 806 calculates the sum of the number of base distributions and the number of trend fluctuation distributions that increases with an increase in the cycle temperature difference ΔTj as the diagnostic temperature division TB 26 ~TB 30 Number of temperature cycles per NB 26 ~NB 30 It can be estimated that:

[0096] The same idea applies to the temperature classification TA2 to TA 23 A predetermined number M of diagnostic temperature ranges TB included in each of the above M(p-1)+1 ~TB M(p-1)+M Number of temperature cycles per NB M(p-1)+1 ~NB M(p-1)+M (p: an integer of 2≦p≦23) may be applied as a method of estimating the temperature range TA p-1 ~TA p+1 The number of temperature cycles occurring in the direction of the larger cycle temperature difference ΔTj is NA. p-1 ~NA p+1If increases, the number of temperature cycles NB M(p-1)+1 ~NB M(p-1)+M may be estimated.

[0097] For example, the diagnosis table creation unit 806 calculates the distribution rate DR of the trend fluctuation distribution by the following formulas (2) to (4). x may be calculated.

[0098]

number

[0099] The predetermined number M is the target temperature division TA p In the above example (FIG. 7), M is "5" (M=5). The variable x is the number of diagnostic temperature sections included in the target temperature section TA p A diagnostic temperature range TB of a given number M included in M(p-1)+1 ~TB M(p-1)+M For each of these, the cycle temperature difference ΔTj is assigned in the order of 1, ..., M, starting from the smallest.

[0100] Then, the diagnosis table creation unit 806 calculates the distribution ratio DR x Based on the intercept b corresponding to the number of base distributions, the diagnostic temperature category TB is calculated using the following equations (5) and (6). M(p-1)+1 ~TB M(p-1)+M Number of temperature cycles per NB M(p-1)+1 ~NB M(p-1)+M may be calculated.

[0101]

number

[0102] For example, as shown in FIG. 12, the diagnosis table creation unit 806 uses the above-mentioned formulas (2) to (6) to create a diagnosis temperature section TB 26 ~TB 30 Number of temperature cycles per NB 26 ~NB 30 can be calculated.

[0103] In addition, for example, the diagnostic table creation unit 806 calculates the diagnostic temperature classification TB based on the slope a of the trend variation distribution with respect to the variable x and the intercept b corresponding to the number of base distributions, using the following formulas (7) and (8). M(p-1)+1 ~TB M(p-1)+M Number of temperature cycles per NB M(p-1)+1 ~NB M(p-1)+M may be calculated.

[0104]

number

[0105] For example, as shown in FIG. 13, the diagnosis table creation unit 806 uses the above-mentioned formulas (7) and (8) to create the diagnosis temperature section TB 26 ~TB 30 Number of temperature cycles per NB 26 ~NB 30 can be calculated.

[0106] In addition, the diagnosis table creation unit 806 creates a temperature division TA p-1 ~TA p+1 The number of temperature cycles occurring in the direction of the larger cycle temperature difference ΔTj is NA. p-1 ~NA p+1 If the temperature decreases, the temperature classification TA p Diagnostic temperature classification TB included in M(p-1)+1 ~TB M(p-1)+M Number of temperature cycles per NB M(p-1)+1 ~NB M(p-1)+M may be estimated.

[0107] In this case, the temperature classification for calculation TA p-1 ~TA p+1 Number of temperature cycles per NA p-1 ~NA p+1 There is a tendency for the distribution of temperature differences ΔTj to decrease uniformly from small to large. Therefore, the number of temperature cycles NB M(p-1)+1 ~NBM(p-1)+M It is highly likely that the following conditions (2-1) and (2-2) will be met.

[0108] (2-1) Number of temperature cycles NB M(p-1)+1 ~NB M(p-1)+M is the temperature classification for aggregation TA p+1 Diagnostic temperature classification TB included in Mp+1 ~TB Mp+M Number of temperature cycles NB Mp+1 ~NB Mp+M Greater than.

[0109] (2-2) Temperature classification for aggregation TA p-1 ,TA p+1 Diagnostic temperature category TB located between M(p-1)+1 ~TB M(p-1)+M Number of temperature cycles per NB M(p-1)+1 ~NB M(p-1)+M increases as the cycle temperature difference ΔTj goes from larger to smaller.

[0110] Therefore, the diagnosis table creation unit 806 creates, for example, the temperature classification TA p Number of temperature cycles NA p From among these, the temperature category for aggregation TA p+1 A diagnostic temperature range TB of a given number M included in Mp+1 ~TB Mp+M Number of temperature cycles NB Mp+1 ~NB Mp+M The average value of (=NA p+1 / M) for diagnostic temperature classification TB M(p-1)+1 ~TB M(p-1)+M In other words, the diagnosis table creation unit 806 distributes the temperature ranges TA p Number of temperature cycles NA p From among these, the temperature category for aggregation TA p+1 Number of temperature cycles NA p+1 The number equivalent to the diagnostic temperature category TB M(p-1)+1 ~TB M(p-1)+M Distribute equally among them.

[0111] Then, the diagnosis table creation unit 806 determines, based on the condition (2-2), for example, the occurrence count NA p The remaining number of (=NA p -NA p+1 ) is set to the diagnostic temperature range TB so that the distribution number increases in accordance with the decrease in the cycle temperature difference ΔTj. M(p-1)+1 ~TB M(p-1)+M Specifically, the diagnosis table creation unit 806 may distribute the occurrence count NA p The remaining number of (=NA p -NA p+1 ) is set to the diagnostic temperature range TB so that the distribution number increases linearly with the decrease in the cycle temperature difference ΔTj. M(p-1)+1 ~TB M(p-1)+M may be distributed to.

[0112] As a result, the diagnostic table creation unit 806 calculates the sum of the number of base distributions and the number of trend fluctuation distributions that increases with the decrease in the cycle temperature difference ΔTj as the diagnostic temperature division TB M(p-1)+1 ~TB M(p-1)+M Number of temperature cycles per NB M(p-1)+1 ~NB M(p-1)+M It can be estimated that:

[0113] <Another example of a method for estimating the number of temperature cycles that occur for each diagnostic temperature category> FIG. 14 shows a plurality of diagnostic temperature divisions TB in the diagnostic temperature cycle history table. q Number of temperature cycles per NB q 14 is a diagram for explaining another example of a method for calculating the temperature for diagnosis TB included in the temperature for collection TA6. 26 ~TB 30 Number of temperature cycles per NB 26 ~NB 30 15 is a diagram for explaining another example of a calculation method (estimation method) of a plurality of diagnostic temperature sections TB in a diagnostic temperature cycle history table. q Number of temperature cycles per NB q15 is a diagram showing yet another example of the calculation result of the temperature range TB6 for diagnosis included in the temperature range TA6 for aggregation. 26 ~TB 30 Number of temperature cycles per NB 26 ~NB 30 16 is a diagram showing yet another example of the calculation result of a plurality of diagnostic temperature sections TB in the diagnostic temperature cycle history table. q Number of temperature cycles per NB q 16 is a diagram showing yet another example of the calculation result of the temperature range TB 26 ~TB 30 Number of temperature cycles per NB 26 ~NB 30 FIG. 13 is a diagram showing yet another example of the calculation result.

[0114] As shown in Fig. 14, in this example, the distribution of the number of occurrences of temperature cycles NA5 to NA7 for each of the temperature divisions TA5 to TA7 for calculation has a tendency TD2 in which the cycle temperature difference ΔTj changes from increasing to decreasing in the temperature division TA6 for calculation. Therefore, the five diagnostic temperature divisions TB 26 ~TB 30 Number of temperature cycles per NB 26 ~NB 30 It is highly likely that the following conditions (3-1) to (3-3) are met.

[0115] (3-1) Five diagnostic temperature ranges TB included in the collection temperature range TA6 between the collection temperature ranges TA5 and TA7 26 ~TB 30 Number of temperature cycles per NB 26 ~NB 30 increases toward the larger cycle temperature difference ΔTj and then decreases in the middle. In other words, the diagnostic temperature range TB 26 ~TB 25+c Number of temperature cycles per NB 26 ~NB25+c can be estimated to increase toward the larger cycle temperature difference ΔTj (c: an integer where 1 < c < 5). On the other hand, for each diagnostic temperature range TB 25+c ~TB 30 the number of occurrences NB 25+c ~NB 30 of each temperature cycle can be estimated to increase toward the smaller cycle temperature difference ΔTj.

[0116] (3-2) For each diagnostic temperature range TB 26 ~TB 25+c the number of occurrences NB 26 ~NB 25+c of each temperature cycle is larger than the number of occurrences NB 21 ~TB 25 of the diagnostic temperature ranges TB 21 ~NB 25 included in the aggregation temperature range TA5.

[0117] (3-3) For each diagnostic temperature range TB 25+c ~TB 30 the number of occurrences NB 25+c ~NB 30 of each temperature cycle is larger than the number of occurrences NB 31 ~TB 35 of the diagnostic temperature ranges TB 31 ~NB 35 included in the aggregation temperature range TA7.

[0118] The diagnostic temperature range TB 25+c corresponds to the intermediate position where it is assumed that the number of occurrences of the temperature cycle among the diagnostic temperature ranges TB 26 ~TB 30 changes from increasing to decreasing toward the larger cycle temperature difference ΔTj. The diagnostic temperature range TB 25+c is, for example, the central diagnostic temperature range TB 26 ~TB 30 among five diagnostic temperature ranges TB 28(c=3).

[0119] Therefore, the diagnostic table creation unit 806 selects, based on the condition (3-2), for example, five diagnostic temperature sections TB 21 ~TB 25 Number of temperature cycles NB 21 ~NB 25 The average value (=NA5 / 5) of the above is used as the diagnostic temperature classification TB 26 ~TB 25+c-1 The funds will be distributed to each of the following:

[0120] Further, the diagnostic table creation unit 806 selects, based on the condition (3-3), for example, five diagnostic temperature sections TB 31 ~TB 35 Number of temperature cycles NB 31 ~NB 35 The average value (=NA7 / 5) of the above is used as the diagnostic temperature classification TB 25+c+1 ~TB 30 The funds will be distributed to each of the following:

[0121] Also, the diagnostic table creation unit 806 calculates, for example, the number of temperature cycle occurrences NB 21 ~NB 25 or the number of temperature cycles NB 31 ~NB 35 The average value of the diagnostic temperature category TB 25+c Distribute to.

[0122] Then, based on the condition (3-1), the diagnostic table creation unit 806 sets, for example, the remaining number of occurrences NA6 to the diagnostic temperature classification TB 26 The number of distributions is increased according to an increase in the cycle temperature difference ΔTj from the diagnostic temperature section TB30 or a decrease in the cycle temperature difference ΔTj from the diagnostic temperature section TB30. 26 ~TB 30Specifically, the diagnostic table creating unit 806 may allocate the diagnostic temperature range TB 26 The number of distributions increases linearly according to an increase in the cycle temperature difference ΔTj from the diagnostic temperature section TB30 or a decrease in the cycle temperature difference ΔTj from the diagnostic temperature section TB30. 26 ~TB 30 may be distributed to.

[0123] As a result, the diagnostic table creation unit 806 calculates the sum of the number of base distributions and the number of trend fluctuation distributions that increases with an increase or decrease in the cycle temperature difference ΔTj as the diagnostic temperature division TB 26 ~TB 30 Number of temperature cycles per NB 26 ~NB 30 It can be estimated that:

[0124] The same idea can be applied to the temperature classification TA2 to TA 23 A predetermined number M of diagnostic temperature ranges TB included in each of the above M(p-1)+1 ~TB M(p-1)+M Number of temperature cycles per NB M(p-1)+1 ~NB M(p-1)+M (p: an integer of 2≦p≦23) may be applied as a method of estimating the temperature range TA p-1 ~TA p+1 In this case, the number of temperature cycles occurring is NA toward the larger temperature difference ΔTj. p-1 ~NA p+1 Temperature classification for calculation is TA p In the same way, if the temperature changes from increasing to decreasing, the number of temperature cycles NB M(p-1)+1 ~NB M(p-1)+M may be estimated.

[0125] For example, the diagnosis table creation unit 806 calculates the distribution rate DR x1 ,DR x2 may be calculated.

[0126]

number

[0127] In addition, the "c-1" in the first term of the denominator of each of the formulas (13) and (14) and the "M-(c-1)" in the second term may be replaced with "c" and "Mc", respectively. In addition, the variable x1 is the temperature division TA p The temperature range for diagnosis TB, which includes the temperature difference ΔTj in the cycle, is relatively small. M(p-1)+1 ~TB M(p-1)+c-1 The cycle temperature difference ΔTj is assigned to each of the following in the order of 1,...,c-1 from the smallest to the largest. Also, the variable x2 is the target temperature classification TA p The temperature range for diagnosis TB, which includes the temperature difference ΔTj in the cycle, is relatively large. M(p-1)+c ~TB M(p-1)+M For each of the above, the cycle temperature difference ΔTj is assigned in the order of 1, ..., M-(c-1) from the largest.

[0128] Then, the diagnosis table creation unit 806 calculates the distribution ratio DR x1 ,DR x2 Based on the intercepts b1 and b2 corresponding to the base distribution, the diagnostic temperature range TB is calculated using the following equations (15) to (18). M(p-1)+1 ~TB M(p-1)+M Number of temperature cycles NB M(p-1)+1 ~NB M(p-1)+M may be calculated.

[0129]

number

[0130] For example, as shown in FIG. 15, the diagnosis table creation unit 806 uses the above-mentioned formulas (9) to (18) to create a diagnosis temperature section TB 26 ~TB 30 Number of temperature cycles per NB 26 ~NB 30 can be calculated.

[0131] In addition, the diagnostic table creation unit 806 calculates the diagnostic temperature classification TB based on the slopes a1 and a2 of the trend variation distribution with respect to the variables x1 and x2, and the intercepts b1 and b2 corresponding to the number of base distributions, using the above-mentioned formulas (17) and (18) and the following formulas (19) to (22). M(p-1)+1 ~TB M(p-1)+M Number of temperature cycles NB M(p-1)+1 ~NB M(p-1)+M may be calculated.

[0132]

number

[0133] In addition, "c" in the first term and "Mc" in the second term of the denominators of equations (21) and (22) may be replaced with "c-1" and "M-(c-1)", respectively.

[0134] For example, as shown in FIG. 16, the diagnosis table creation unit 806 uses the above-mentioned formulas (17) to (22) to create a diagnosis temperature section TB 26 ~TB 30 Number of temperature cycles per NB 26 ~NB 30 can be calculated.

[0135] In addition, the diagnosis table creation unit 806 creates a temperature division TA p-1 ~TA p+1 In this case, the number of temperature cycles occurring is NA toward the larger temperature difference ΔTj. p-1 ~NA p+1 Temperature classification for calculation is TA p In the same way, if the temperature changes from decreasing to increasing, the temperature classification TA p Diagnostic temperature classification TB included in M(p-1)+1 ~TB M(p-1)+M Number of temperature cycles per NB M(p-1)+1 ~NB M(p-1)+M may be estimated.

[0136] In this case, the temperature classification for calculation TA p-1 ~TAp+1 The number of occurrences NA of each temperature cycle p-1 ~NA p+1 In the distribution of, the temperature bins TA for aggregation are from the smaller to the larger cycle temperature difference ΔTj p There is a tendency to change from decreasing to increasing. Therefore, the number of occurrences NB of the temperature cycle M(p-1)+1 ~NB M(p-1)+M is likely to satisfy the following conditions (4-1) to (4-3).

[0137] (4-1) The temperature bins TA for aggregation p-1 , TA p+1 The temperature bins TA for aggregation between p contain a predetermined number M of diagnostic temperature bins TB M(p-1)+1 ~TB M(p-1)+M The number of occurrences NB of each temperature cycle M(p-1)+1 ~NB M(p-1)+M decreases towards the larger cycle temperature difference ΔTj and turns to increase in the middle. That is, for the diagnostic temperature bins TB with a relatively smaller cycle temperature difference ΔTj M(p-1)+1 ~TB M(p-1)+c The number of occurrences NB of each temperature cycle M(p-1)+1 ~NB M(p-1)+c can be estimated to decrease towards the larger cycle temperature difference ΔTj (c: an integer where 1 < c < M). On the other hand, for the diagnostic temperature bins TB with a relatively larger cycle temperature difference M(p-1)+c ~TB M(p-1)+M The number of occurrences NB of each temperature cycle M(p-1)+c ~NB M(p-1)+M can be estimated to decrease towards the smaller cycle temperature difference ΔTj.

[0138] (4-2) For the diagnostic temperature bins TB with a relatively smaller cycle temperature difference ΔTj M(p-1)+1 ~TB M(p-1)+c The number of occurrences NB of each temperature cycle M(p-1)+1 ~NB M(p-1)+c is the diagnostic temperature bins TB included in the temperature bins TA for aggregation p-1 ~TB M(p-2)+1 ~TB M(p-2)+MNumber of temperature cycles NB M(p-2)+1 ~NB M(p-2)+M Less than.

[0139] (4-3) The diagnostic temperature range TB where the cycle temperature difference ΔTj is relatively large M(p-1)+c ~TB M(p-1)+M Number of temperature cycles per NB M(p-1)+c ~NB M(p-1)+M is the temperature classification for aggregation TA p+1 Diagnostic temperature classification TB included in Mp+1 ~TB Mp+M Number of temperature cycles NB Mp+1 ~NB Mp+M Less than.

[0140] Therefore, the diagnosis table creation unit 806 creates, for example, the temperature classification TA p Number of temperature cycles NA p From among these, the temperature category for aggregation TA p-1 A diagnostic temperature range TB of a given number M included in M(p-2)+1 ~TB M(p-2)+M Number of temperature cycles NB M(p-2)+1 ~NB M(p-2)+M The average value of (=NA p-1 / M) for diagnostic temperature classification TB M(p-1)+1 ~TB M(p-1)+c-1 The funds will be distributed to each of the following:

[0141] Further, the diagnosis table creation unit 806 creates, for example, the temperature classification TA p Number of temperature cycles NA p From among these, the temperature category for aggregation TA p+1 A diagnostic temperature range TB of a given number M included in Mp+1 ~TB Mp+M Number of temperature cycles NB Mp+1 ~NB Mp+M The average value of (=NA p+1 / M) for diagnostic temperature classification TB M(p-1)+c+1 ~TB M(p-1)+M The funds will be distributed to each of the following:

[0142] Also, the diagnostic table creation unit 806 calculates, for example, the number of temperature cycle occurrences NB M(p-2)+1 ~NB M(p-2)+M or the number of temperature cycles NB Mp+1 ~NB Mp+M The average value of the diagnostic temperature category TB M(p-1)+c Distribute to.

[0143] Then, the diagnosis table creation unit 806 determines whether the total sum of the distribution numbers is within the tabulation temperature range TA p Number of temperature cycles NA p The diagnostic temperature range TB M(p-1)+1 ~TB M(p-1)+M Specifically, the diagnostic table creation unit 806 collects (reduces) the number of items already distributed to the diagnostic temperature category TB M(p-1)+1 Increase in cycle temperature difference ΔTj from TB M(p-1)+M The diagnostic temperature range TB M(p-1)+1 ~TB M(p-1)+M Recover the amount already distributed to.

[0144] Based on the conditions in (4-1), the temperature classification for aggregation TA p Number of occurrences: NA p From diagnostic temperature classification TB M(p-1)+1 ~TB M(p-1)+M For convenience, the manner in which the excess allocated numbers are collected may be referred to as "trend fluctuation collection."

[0145] As a result, the diagnostic table creation unit 806 calculates the difference obtained by subtracting the number of trend fluctuation collections that increases with an increase or decrease in the cycle temperature difference ΔTj from the number of base distributions, as the diagnostic temperature division TB M(p-1)+1 ~TB M(p-1)+M Number of temperature cycles per NB M(p-1)+1 ~NB M(p-1)+M It can be estimated that:

[0146] <Another example of a method for estimating the number of temperature cycles occurring for each diagnostic temperature range> The diagnostic table creation unit 806 creates a predetermined number M of diagnostic temperature sections TB1 to TB2 included in the tabulation temperature section TA1 based on the magnitude relationship between the occurrence counts NA1 and NA2 of the temperature cycles in the tabulation temperature sections TA1 and TA2. M Number of temperature cycles NB1 to NB M This is because the tallying temperature section TA1 is located at one end of the target temperature range where the cycle temperature difference ΔTj is small, and there are no adjacent tallying temperature sections except on the side where the cycle temperature difference ΔTj is large. Specifically, the diagnosis table creation unit 806 estimates that the trend (increase or decrease) of the change in the number of temperature cycle occurrences NA1 relative to the number of temperature cycle occurrences NA2 is the same as the trend (increase or decrease) of the change in the number of temperature cycle occurrences NA1 relative to the number of temperature cycle occurrences NA2 in the diagnosis temperature sections TB1 to TB M Number of temperature cycles between NB1 and NB M As reflected in the distribution of occurrences NB1 to NB M may be estimated.

[0147] Similarly, the diagnosis table creation unit 806 creates, for example, a temperature division for compilation TA 23 ,TA 24 Number of temperature cycles NA 23 ,NA 24 Based on the magnitude relationship, the temperature classification for aggregation TA 24 A diagnostic temperature range TB of a given number M included in 23M+1 ~TB 23M+M Number of temperature cycles NB 23M+1 ~NB 23M+M Estimate the temperature range for aggregation TA 24 This is because the temperature range is located at one end where the cycle temperature difference ΔTj is large, and there are no adjacent temperature ranges for aggregation only at the end where the cycle temperature difference ΔTj is small. 23 Number of temperature cycles NA 24 The trend of change (increase or decrease) of the diagnostic temperature category TB 23M+1 ~TB 23M+M Number of temperature cycles occurring during NB 23M+1 ~NB 23M+M As reflected in the distribution of 23M+1 ~NB23M+M may be estimated.

[0148] Also, the diagnostic table creation unit 806, for example, divides the number of occurrences NA1 of the temperature cycles in the tabulation temperature section TA1 into the predetermined number M of diagnostic temperature sections TB1 to TB M The number of temperature cycles NB1 to NB M In other words, the diagnostic table creating unit 806 may estimate the number of occurrences of the temperature cycles NB1 to NB M may be estimated as the value (=NA1 / M) obtained by dividing the number of occurrences of temperature cycles NA1 in the temperature division TA1 for aggregation by a predetermined number M. M is very small and the effect on accuracy can be considered small.

[0149] Similarly, the diagnosis table creation unit 806 creates, for example, a temperature division for compilation TA 24 Number of temperature cycles NA 24 , diagnostic temperature classification TB 23M+1 ~TB 23M+M The number of temperature cycles NB 23M+1 ~NB 23M+M In other words, the diagnostic table creating unit 806 may estimate the number of occurrences of the temperature cycle NB 23M+1 ~NB 23M+M The temperature range for aggregation is TA 24 Number of temperature cycles NA 24 Divided by a given number M (=NA 24 / M).

[0150] [Other embodiments] Next, other embodiments will be described.

[0151] The above-described embodiment may be modified or altered as appropriate.

[0152] For example, in the above-described embodiment, the power conversion device 1 may generate three-phase AC power for driving the electric motor EM based on three-phase AC power input from a power source other than the commercial power source PS.

[0153] Furthermore, for example, in the above-described embodiment, the power conversion device 1 may generate three-phase AC power for driving the electric motor EM based on power input from a DC power source instead of or in addition to the three-phase AC power source. In this case, the DC power is input to a DC link unit (positive line PL and negative line NL) between the rectifier circuit 10 and the inverter circuit 30.

[0154] Also, for example, in the above-mentioned embodiment, the power conversion device 1 may output three-phase AC power for driving a load device other than the electric motor EM. In this case, for example, instead of the three-phase AC power, the power conversion device 1 may output two systems of single-phase AC power or two systems of DC power with any one of the U phase, V phase, and W phase as a reference potential. For example, the other load device is a coil of an induction furnace.

[0155] In addition, for example, in the above-mentioned embodiment, the control circuit 80 calculates the target temperature range TA p Based on the distribution trend of the number of occurrences of temperature cycles in four or more tabulation temperature categories, including M(p-1)+1 ~TB M(p-1)+M Number of temperature cycles NB M(p-1)+1 ~NB M(p-1)+M may be estimated.

[0156] In addition, for example, in the above-mentioned embodiment, the control circuit 80 sets the temperature division for calculation TA p Number of temperature cycles NA p The diagnostic temperature range TB is set so that the distribution number changes nonlinearly. M(p-1)+1 ~TB M(p-1)+M The number of temperature cycles NB M(p-1)+1 ~NB M(p-1)+M may be estimated.

[0157] In addition, for example, in the above-mentioned embodiment, a plurality of temperature divisions TAp may be configured with unequal widths at least in part over the target temperature range. p A diagnostic temperature section TB having a predetermined number M of sections, at least some of which are composed of unequal widths M(p-1)+1 ~TB M(p-1)+M The predetermined number M may be a number of temperature divisions TA p The value may be changed for each

[0158] In addition, for example, in the above-mentioned embodiment, a plurality of temperature divisions TA p Only a part of the temperature ranges is divided into a predetermined number M of temperature ranges for diagnosis, and the remaining temperature ranges TA p may be used as a diagnostic temperature range as is.

[0159] Also, for example, in the above-described embodiment, the function of the control circuit 80 may be realized by a plurality of control circuits. For example, the control circuit 80 may be replaced with a plurality of control circuits including a control circuit for realizing a function of controlling the operation of the power conversion device 1, such as a function of controlling the inverter circuit 30, and a control circuit for realizing a life diagnosis function of the power semiconductor element 100 of the power conversion device 1.

[0160] Also, for example, in the above-mentioned embodiment, the life diagnosis function of the power semiconductor element 100 mounted on the power conversion device 1 may be transferred to a predetermined external device (an example of a life diagnosis device) capable of communicating with the power conversion device 1 (control circuit 80) instead of the control circuit 80. The predetermined external device is, for example, a server device. The server device may be, for example, an on-premise server or a cloud server such as a management center installed outside a factory where the device to be driven by the electric motor EM is installed. Also, the server device may be, for example, an edge server installed within the premises of the factory where the device to be driven by the electric motor EM is installed, or in a communication facility (for example, a base station or a station building) located relatively close to the factory. Also, the predetermined external device is, for example, a terminal device (user terminal) used by a user of the power conversion device 1. The terminal device may be, for example, a stationary terminal device such as a desktop computer terminal installed in a management room or the like of a factory where the device to be driven by the electric motor EM is installed. Also, the terminal device may be, for example, a portable terminal device (mobile terminal) such as a smartphone, a tablet terminal, or a laptop computer terminal.

[0161] Also, for example, in the above-described embodiment, the life diagnosis function is applied to the life diagnosis of the power semiconductor element 100 mounted on the power conversion device 1, but it may also be applied to the life diagnosis of other semiconductor devices in which a power semiconductor element is mounted.

[0162] [Effect] Next, the operation of the life assessment function according to this embodiment will be described.

[0163] In this embodiment, the control circuit 80 includes a temperature acquisition unit 801, a waveform counting unit 804, a diagnostic table creation unit 806, and a life diagnosis unit 808. Specifically, the temperature acquisition unit 801 acquires the internal temperature of the power semiconductor element 100 mounted on the semiconductor device. Furthermore, the waveform counting unit 804 detects a temperature cycle consisting of temperature rise and fall accompanying the operation of the power semiconductor element 100 based on the change in temperature acquired by the temperature acquisition unit 801. Furthermore, the waveform counting unit 804 tallies up the number of occurrences of temperature cycles for each of a plurality of tallying temperature sections across the target temperature range for cycle temperature differences ΔTj corresponding to the range of change in temperature rise and fall occurring in the temperature cycle in a tallying temperature cycle history table 805. Furthermore, the diagnostic table creation unit 806 estimates the number of occurrences of temperature cycles for each of a plurality of diagnostic temperature sections across the target temperature range, which is configured by dividing at least some of the plurality of tally temperature sections into two or more, based on the distribution tendency of the number of occurrences of temperature cycles for each of the plurality of tally temperature sections tallied by the waveform counting unit 804. Then, the life diagnosis unit 808 performs diagnosis regarding the life of the power semiconductor element 100, based on the characteristic data indicating the correspondence between the cycle temperature difference ΔTj and the life of the power semiconductor element 100, and the number of occurrences of temperature cycles for each of the plurality of diagnostic temperature sections.

[0164] Thereby, the control circuit 80 can create a diagnostic temperature cycle history table with finer granularity regarding the cycle temperature difference ΔTj from the tallying temperature cycle history table 805, for example. Therefore, the control circuit 80 can use the diagnostic temperature cycle history table to reduce the amount of data (tallying temperature cycle history table 805) of the number of occurrences of temperature cycles for each of a plurality of tallying temperature sections while suppressing a decrease in the accuracy of diagnosis regarding the life of the power semiconductor element 100. Therefore, even if a large storage area cannot be secured for the number of occurrences of temperature cycles for each of a plurality of tallying temperature sections, such as when a life diagnosis function is built into the power conversion device 1, a decrease in the accuracy of diagnosis regarding the life of the power semiconductor element 100 can be suppressed.

[0165] Furthermore, in this embodiment, the waveform counting unit 804 may count the number of occurrences of temperature cycles for each of a plurality of tabulation temperature sections that divide the target temperature range into equal widths at first intervals (e.g., at 5°C intervals or 10°C intervals).Then, based on the tendency of distribution of the number of occurrences of temperature cycles for each of the tabulation temperature sections tabulated by the waveform counting unit 804, the diagnostic table creating unit 806 may estimate the number of occurrences of temperature cycles for each of a plurality of diagnostic temperature sections that divide the target temperature range into second intervals (e.g., at 1°C intervals) that correspond to the value obtained by dividing the first interval by a predetermined integer equal to or greater than 2 (predetermined number M).

[0166] As a result, the control circuit 80 can use multiple temperature sections for aggregation and multiple temperature sections for diagnosis, which are configured with equal widths, to aggregate the number of temperature cycles that have occurred related to the cycle temperature difference ΔTj and estimate the number of temperature cycles that have occurred.

[0167] In addition, in this embodiment, the diagnostic table creation unit 806 may estimate the number of temperature cycles occurring for each of multiple diagnostic temperature sections, for at least some of the tallying temperature sections, in a manner that distributes the number of temperature cycles occurring in the target tallying temperature section to two or more diagnostic temperature sections included in the target tallying temperature section, based on the tendency of distribution of the number of temperature cycles occurring in two or more adjacent tallying temperature sections including the target tallying temperature section among the multiple tallying temperature sections.

[0168] This enables the control circuit 80 to estimate the number of temperature cycles occurring for each of two or more diagnostic temperature sections included in the target aggregation temperature section, in accordance with the distribution trend of the number of temperature cycles occurring between two or more adjacent aggregation temperature sections that include the target aggregation temperature section.

[0169] In addition, in this embodiment, for at least some of the aggregation temperature sections, if the number of temperature cycles occurring in three or more adjacent aggregation temperature sections including the target aggregation temperature section and the adjacent aggregation temperature sections before and after it among the multiple aggregation temperature sections tends to increase or decrease from the smaller cycle temperature difference ΔTj to the larger cycle temperature difference ΔTj, the diagnostic table creation unit 806 may distribute the number of temperature cycles occurring in the target aggregation temperature section to two or more diagnostic temperature sections included in the target aggregation temperature section so that the number of temperature cycles occurring increases or decreases from the smaller cycle temperature difference ΔTj to the larger cycle temperature difference ΔTj.

[0170] This enables the control circuit 80 to estimate the number of temperature cycles occurring for each of two or more diagnostic temperature sections included in the target aggregation temperature section, based on the specific distribution trend of the number of temperature cycles occurring in three or more adjacent aggregation temperature sections before and after the target aggregation temperature section.

[0171] In addition, in this embodiment, for at least some of the aggregation temperature sections, if the number of temperature cycles occurring in three or more adjacent aggregation temperature sections, including the target aggregation temperature section among the multiple aggregation temperature sections and the adjacent aggregation temperature sections before and after it, tends to change from increasing to decreasing, or from decreasing to increasing, in the target aggregation temperature section as the cycle temperature difference ΔTj moves from smaller to larger, the diagnostic table creation unit 806 may distribute the number of temperature cycles occurring in the target aggregation temperature section to two or more diagnostic temperature sections included in the target aggregation temperature section so that it increases from smaller to larger cycle temperature difference ΔTj and then turns to decreasing in the middle, or decreases and then turns to increasing in the middle.

[0172] This enables the control circuit 80 to estimate the number of temperature cycles occurring for each of two or more diagnostic temperature sections included in the target aggregation temperature section, based on the specific distribution trend of the number of temperature cycles occurring in three or more adjacent aggregation temperature sections before and after the target aggregation temperature section.

[0173] In addition, in this embodiment, the diagnostic table creation unit 806 may estimate the number of temperature cycles occurring for each of multiple diagnostic temperature sections for at least some of the aggregation temperature sections by linearly distributing the number of temperature cycles occurring in the target aggregation temperature section to two or more diagnostic temperature sections included in the target aggregation temperature section.

[0174] This allows the control circuit 80 to relatively easily estimate the number of temperature cycles that occur for each of the multiple diagnostic temperature sections, thereby reducing the processing load on the control circuit 80 for the number of temperature cycles that occur for each of the multiple diagnostic temperature sections.

[0175] Although the embodiments have been described in detail above, the present disclosure is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist described in the claims. [Explanation of symbols]

[0176] 1 Power conversion equipment (semiconductor equipment) 10 Rectifier circuit 20 Smoothing circuit 30 Inverter circuit 40 Current Sensor 50 Voltage Sensor 60 Temperature Sensor 70 Gate drive circuit 80 Control circuit (life diagnosis device) 100 Power semiconductor element 801 Temperature acquisition section 802 Mountain / Valley Detector 803 Stack Table 804 Waveform counting unit (counting unit) 805 Temperature cycle history table for aggregation 806 Diagnosis table creation unit (estimation unit) 807 Life Data 808 Lifespan Diagnosis Unit 809 Lifetime Accumulation Buffer EM electric motor PS commercial power supply

Claims

1. a temperature acquisition unit that acquires an internal temperature of a power semiconductor element mounted on the semiconductor device; a counting unit that detects a temperature cycle constituted by an increase and decrease in the temperature associated with an operation of the power semiconductor element based on a change in temperature acquired by the temperature acquisition unit, and counts the number of occurrences of the temperature cycle for each of a plurality of first sections over a predetermined temperature range for a cycle temperature difference corresponding to a change width of the increase and decrease in the temperature that occurs in the temperature cycle; an estimation unit that estimates the number of occurrences of the temperature cycle for each of a plurality of second divisions across the predetermined temperature range, the estimation unit being configured by dividing at least a portion of the plurality of first divisions into two or more, based on a distribution tendency of the number of occurrences of the temperature cycle for each of the plurality of first divisions tallied by the talliation unit; and a life diagnosis unit that performs a diagnosis regarding a life of the power semiconductor element based on characteristic data indicating a correspondence relationship between the cycle temperature difference and a life of the power semiconductor element and the number of occurrences of the temperature cycle for each of the plurality of second divisions. Lifespan diagnostic device.

2. the counting unit counts the number of occurrences of the temperature cycle for each of the plurality of first divisions that divide the predetermined temperature range into first intervals; the estimation unit estimates the number of occurrences of the temperature cycle for each of the plurality of second sections that divide the predetermined temperature range into second intervals that correspond to a value obtained by dividing the first interval by a predetermined integer equal to or greater than 2, based on a distribution tendency of the number of occurrences of the temperature cycle for each of the plurality of first sections that are tallied by the talliation unit; The life assessment device according to claim 1 .

3. the estimation unit estimates the number of occurrences of the temperature cycles for each of the plurality of second sections in a manner that distributes the number of occurrences of the temperature cycles in a target first section to two or more of the second sections included in the target first section based on a distribution tendency of the number of occurrences of the temperature cycles in two or more adjacent first sections including the target first section among the plurality of first sections; 3. The life assessment device according to claim 1 or 2.

4. When the number of occurrences of the temperature cycles in three or more adjacent first sections including a target first section and adjacent first sections before and after the target first section among the plurality of first sections tends to increase or decrease from the smaller cycle temperature difference to the larger cycle temperature difference, the estimation unit distributes the number of occurrences of the temperature cycles in the target first section to two or more second sections included in the target first section such that the number of occurrences of the temperature cycles in the target first section increases or decreases from the smaller cycle temperature difference to the larger cycle temperature difference. The life assessment device according to claim 3 .

5. When the number of occurrences of the temperature cycles in three or more adjacent first sections including a target first section and adjacent first sections before and after the target first section among the plurality of first sections tends to change from an increase to a decrease, or from a decrease to an increase, in the target first section as the cycle temperature difference increases from the smallest second section among the three or more second sections included in the target first section, and changes to a decrease in the second section between the two end second sections among the three or more second sections included in the target first section, or changes from the smallest second section among the three or more second sections included in the target first section toward the largeest cycle temperature difference, and changes to an increase in the second section between the two end second sections among the three or more second sections included in the target first section.

5. The life assessment device according to claim 3 or 4.

6. the estimation unit estimates the number of occurrences of the temperature cycles for each of the second sections in a manner that linearly distributes the number of occurrences of the temperature cycles in the first section of interest for at least the part of the first sections to the second sections included in the first section of interest; The life assessment device according to claim 3 .

7. A life assessment device comprising the life assessment device according to any one of claims 1 to 6, Semiconductor device.

8. A lifespan assessment method executed by a lifespan assessment device, comprising: a temperature acquiring step of acquiring an internal temperature of a power semiconductor element mounted on the semiconductor device; a counting step of detecting a temperature cycle constituted by an increase and decrease in the temperature caused by an operation of the power semiconductor element based on the change in temperature acquired in the temperature acquiring step, and counting the number of occurrences of the temperature cycle for each of a plurality of first sections over a predetermined temperature range for a cycle temperature difference corresponding to a change width of the increase and decrease in the temperature occurring in the temperature cycle; an estimation step of estimating the number of occurrences of the temperature cycle for each of a plurality of second sections across the predetermined temperature range, the second section being configured by dividing at least a part of the plurality of first sections into two or more sections based on a distribution tendency of the number of occurrences of the temperature cycle for each of the plurality of first sections tallied in the tallying step; and a lifetime diagnosis step of diagnosing the lifetime of the power semiconductor element based on characteristic data indicating a correspondence relationship between the cycle temperature difference and the lifetime of the power semiconductor element and the number of occurrences of the temperature cycle for each of the plurality of second divisions. Lifespan assessment method.

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