Element temperature estimation device

Abstract

To provide an element temperature estimation device improved in estimation accuracy.SOLUTION: The element temperature estimation device is applied to a power conversion device. The power conversion device includes a wiring board, a semiconductor element that is connected to wiring of the wiring board and performs a switching operation, and a housing that accommodates the semiconductor element therein and is thermally connected to the semiconductor element. The power conversion device has a first heat dissipation path that is a heat dissipation path from the semiconductor element to the housing, and a second heat dissipation path that is a heat dissipation path from the semiconductor element to the wiring board. The device temperature estimation device includes a heat transfer amount estimation unit 30a1 and a device temperature estimation unit 30a2. The heat transfer amount estimation unit 30a1 estimates a first heat transfer amount Q1 of heat transferred through the first heat dissipation path. The device temperature estimation unit 30a2 estimates the device temperature TJ, which is the temperature of the semiconductor device, based on the first heat transfer amount 30a1 estimated by the heat transfer amount estimation unit Q1.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The disclosure in this specification relates to an element temperature estimation device. [Background technology]

[0002] Patent Document 1 describes a power conversion device that converts power supplied from a power source and outputs it to a load. This power conversion device includes multiple semiconductor elements that form an inverter circuit. Heat generated in the semiconductor elements when current is applied is transferred to the housing and then released into a coolant by heat dissipation fins provided on the housing.

[0003] Here, to prevent the temperature of the semiconductor element (element temperature) from exceeding the heat resistance temperature, it is necessary to reduce or stop the output when the element temperature reaches or exceeds a threshold value. Therefore, a device for estimating the element temperature is required. The element temperature estimation device described in Patent Document 1 estimates the element temperature based on the temperature detected by a temperature sensor attached to a heat dissipation fin, the refrigerant flow rate, and the refrigerant temperature. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6029796 Summary of the Invention [Problem to be solved by the invention]

[0005] The above-mentioned estimation device estimates the element temperature on the assumption that most of the heat generated in the semiconductor element is dissipated from the heat dissipation fins. However, in reality, some of the heat generated in the semiconductor element is also dissipated from heat dissipation paths (sub-heat dissipation paths) other than the heat dissipation path from the heat dissipation fins. If the amount of heat dissipated from the sub-heat dissipation paths is large, the accuracy of the estimation device for the element temperature will decrease.

[0006] One disclosed object is to provide an element temperature estimation device with improved estimation accuracy. [Means for solving the problem]

[0007] In order to achieve the above object, an element temperature estimation device according to one aspect of the present disclosure includes: A wiring board (21), a semiconductor element (221) connected to the wiring of the wiring board and performing a switching operation to convert power supplied from a power source and output it to a load (7m1); a housing (10) that accommodates a semiconductor element therein and is thermally connected to the semiconductor element; In a device temperature estimation device applied to a power conversion device (7i) having a first heat dissipation path (R1) that is a heat dissipation path from a semiconductor element to a housing, and a second heat dissipation path (R2) that is a heat dissipation path from the semiconductor element to a wiring board, a heat transfer amount estimation unit (30a1) for estimating a first heat transfer amount (Q1) through the first heat dissipation path or a second heat transfer amount (Q2) through the second heat dissipation path; The heat transfer control device further includes an element temperature estimation unit (30a2) for estimating an element temperature, which is the temperature of the semiconductor element, based on the amount of heat transfer estimated by the heat transfer amount estimation unit.

[0008] Here, even if the amount of heat generated in the semiconductor element is the same, if the second heat transfer amount is large, the first heat transfer amount will be small. In other words, if the element temperature is estimated without considering the second heat transfer amount, a temperature higher than the actual element temperature will be estimated. Similarly, if the first heat transfer amount is large, the second heat transfer amount will be small, and if the element temperature is estimated without considering the first heat transfer amount, a temperature higher than the actual element temperature will be estimated. In consideration of this, in the element temperature estimation device disclosed above, the heat transfer amount estimating unit estimates the first heat transfer amount or the second heat transfer amount. Therefore, when estimating the first heat transfer amount, the larger the second heat transfer amount, the smaller the estimated first heat transfer amount. When estimating the second heat transfer amount, the larger the estimated first heat transfer amount, the smaller the estimated second heat transfer amount. Then, since the element temperature is estimated based on the heat transfer amount estimated in this way, the element temperature can be estimated with high accuracy.

[0009] The reference numbers in parentheses above merely indicate an example of the correspondence with specific configurations in the embodiments described below, and do not in any way limit the technical scope. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram illustrating a configuration of an eVTOL in a first embodiment. [Figure 2] FIG. 2 is an external view of the propeller and EPU shown in FIG. 1. [Figure 3] FIG. 2 is an electrical block diagram of the EPU shown in FIG. 1. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 2. [Figure 5] FIG. 5 is a view taken along the arrow V in FIG. 4. [Figure 6] FIG. 6 is a front view of the semiconductor module shown in FIG. [Figure 7] FIG. 2 is a cross-sectional view of a semiconductor module. [Figure 8] FIG. 4 is a diagram showing thermal resistance at each portion included in the heat dissipation path according to the first embodiment. [Figure 9] 4 is a graph showing the relationship between the distance from a semiconductor module and the temperature in the first embodiment. [Figure 10] 10 is a map used to estimate a first heat transfer amount in the second embodiment. [Figure 11] FIG. 10 is an electrical block diagram of element temperature estimation according to a second embodiment. [Figure 12] FIG. 10 is an electrical block diagram of element temperature estimation according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, several embodiments for carrying out the present disclosure will be described with reference to the drawings. In each embodiment, parts corresponding to matters described in the preceding embodiment will be assigned the same reference numerals, and duplicate descriptions may be omitted. In each embodiment, when only a part of the configuration is described, other previously described embodiments may be applied to the other parts of the configuration. In addition to combinations of parts that are specifically specified as being combinable in each embodiment, it is also possible to partially combine embodiments even if not specified, as long as there is no particular problem with the combination.

[0012] (First embodiment) The electric aircraft shown in Figure 1 is a vertical take-off and landing aircraft called eVTOL2, which is an electric aircraft that can take off and land vertically. eVTOL is an abbreviation for electric Vertical Take-Off and Landing aircraft. eVTOL2 is a manned aircraft that carries a crew member. eVTOL2 is equipped with an airframe 3, a battery 4, an FCU 5, a propeller 6, an EPU 7, etc.

[0013] The airframe 3 has an airframe main body 3a and gliding wings 3b. A plurality of propellers 6 are attached to the gliding wings 3b, generating lift and thrust for the airframe 3. The EPU 7 is an electric propulsion device that drives the propellers 6 to rotate. EPU is an abbreviation for Electric Propulsion Unit. The EPU 7 has a motor device 7m and a motor control device. In the following explanation, the motor control device will be referred to as MCU 7i. MCU is an abbreviation for Motor Control Unit.

[0014] An EPU 7 is provided for each of the multiple propellers 6. The EPUs 7 are arranged next to the propellers 6 along the propeller axes. All of the multiple EPUs 7 are fixed to the airframe 3. The EPUs 7 support the propellers 6 so that they can rotate. The battery 4 is mounted on the airframe 3. The battery 4 supplies DC power to the multiple EPUs 7. The battery 4 has a secondary battery that can be charged and discharged.

[0015] The FCU 5 is a flight control device, and FCU is an abbreviation for Flight Control Unit. The FCU 5 controls the flight state of the eVTOL 2 by controlling the operation of each EPU 7. The FCU 5 controls the drive state of the motor device 7m, and ultimately the drive state of the propeller 6, mainly by controlling the operation of the MCU 7i. As shown in FIG. 3, the FCU 5 is mainly composed of a computer. This computer has a processor 5a, a memory 5b, an input / output interface, a bus connecting these, etc. The FCU 5 performs various processes such as flight control processes for flight control by having the processor 5a execute a control program 5c stored in the memory 5b.

[0016] As shown in FIG. 2, the propeller 6 and the motor device 7m are connected by a rotation shaft 8. The propeller 6 and the motor device 7m are arranged along the motor axis Cm so that the rotation axis of the motor device 7m coincides with the rotation axis of the propeller 6. The EPU 7 may be provided with a reducer that reduces the speed of rotation by the motor device 7m. The MCU 7i is arranged along the motor axis Cm together with the propeller 6 and the motor device 7m. In the example shown in FIG. 2, the MCU 7i is arranged between the motor device 7m and the propeller 6. The MCU 7i may also be arranged on the opposite side of the propeller 6 from the motor device 7m.

[0017] The motor device 7m includes a motor and a motor housing 7m1. The motor is an electric rotating machine having a stator and a rotor, and is a multi-phase AC motor. The motor housing 7m1 accommodates the motor. The motor housing 7m1 is cylindrical with a bottom and concentric with the motor axis Cm. Heat dissipation fins 7m2 are attached to the outer surface of the motor housing 7m1. The motor housing 7m1 and the heat dissipation fins 7m2 are made of metal. Outside air flows along the outer surface of the motor housing 7m1 in the direction of the motor axis Cm. Heat generated by the motor when current is applied is transferred from the motor housing 7m1 to the heat dissipation fins 7m2, and then released into the outside air from the heat dissipation fins 7m2. In short, the motor device 7m is air-cooled by the outside air.

[0018] As shown in FIG. 3, the MCU 7i includes an inverter circuit 20, a control circuit 30, an inverter housing, and the like. In the following description, the inverter housing will be simply referred to as the housing 10. The housing 10 accommodates the inverter circuit 20 and the control circuit 30. The housing 10 has a cylindrical shape with a bottom that is concentric with the motor axis Cm. Heat dissipation fins 11 are attached to the outer periphery of the housing 10. The housing 10 and the heat dissipation fins 11 are made of metal. Outside air flows along the outer periphery of the housing 10 in the direction of the motor axis Cm. Heat generated in the inverter circuit 20 when current is applied is transferred from the housing 10 to the heat dissipation fins 11, and then released from the heat dissipation fins 11 into the outside air. In short, the MCU 7i is air-cooled by the outside air.

[0019] The EPU 7 may also include a blower fan that blows outside air to the heat dissipation fins 7m2 and the heat dissipation fins 11. The EPU 7 may also include a blower duct. The blower duct (not shown) has a cylindrical shape that is concentric with the motor axis Cm and covers the entire motor housing 7m1 and the housing 10. The outside air blown from the blower fan into the blower duct flows between the outer peripheral surfaces of the motor housing 7m1 and the housing 10 and the blower duct, and exchanges heat with the heat dissipation fins 7m2 and the heat dissipation fins 11.

[0020] As shown in Fig. 4, the inverter circuit 20 includes a thick copper substrate 21, a semiconductor module 22, a capacitor 23, etc. The inverter circuit 20 is a circuit that converts DC power supplied from the battery 4 into AC power, and an upper arm and a lower arm are formed by a plurality of semiconductor modules 22. The capacitor 23 reduces pulsation in the voltage applied to the inverter circuit 20. The semiconductor module 22 and the capacitor 23 are mounted on the thick copper substrate 21. The thick copper substrate 21 is a type of wiring board in which wiring is applied to an insulating substrate, and is a wiring board in which the copper layer serving as wiring has a thickness of 100 µm or more.

[0021] The semiconductor module 22 and the capacitor 23 are electrically connected to the wiring of the thick copper substrate 21. The capacitor 23 is mounted on the thick copper substrate 21. The semiconductor module 22 is thermally connected to the inner circumferential surface of the housing 10. In the direction of the motor axis Cm, the region of the housing 10 where the heat dissipation fins 11 are provided is called the fin region. As shown in FIG. 5 , the multiple semiconductor modules 22 are arranged in a line in the circumferential direction along the inner circumferential surface of the housing 10.

[0022] The control circuit 30 includes a control board 31 and an IC chip 32. The control circuit 30 controls the operation of the inverter circuit 20 to control the drive of the motor device 7m. The IC chip 32 is mounted on the control board 31. The IC chip 32 includes a processor 30a and a memory 30b shown in FIG. 3. The control circuit 30 is mainly composed of a computer. This computer includes the processor 30a, the memory 30b, an input / output interface, a bus connecting these, and the like. The control circuit 30 executes various processes, such as inverter control process for controlling the inverter circuit 20, by having the processor 30a execute a control program 30c stored in the memory 30b.

[0023] The thick copper substrate 21 and the control substrate 31 are supported by the housing 10. Through holes 21a, 31a are formed in the centers of the thick copper substrate 21 and the control substrate 31. The rotary shaft 8 is inserted into these through holes 21a, 31a. As shown in FIG. 4, the thick copper substrate 21 and the control substrate 31 are arranged so that the plate surfaces of the substrates are perpendicular to the motor axis Cm. The thick copper substrate 21 and the control substrate 31 are arranged opposite to each other. The control substrate 31 is arranged on the opposite side of the thick copper substrate 21 from the semiconductor module 22 and the capacitor 23.

[0024] 6, the semiconductor module 22 has a semiconductor element 221, power terminals 222, signal terminals 223, a heat sink 224 (heat diffusion member), and mold resin 225. The semiconductor element 221 is a switching element, and although a MOSFET is used in this embodiment, a switching element such as an IGBT may also be used.

[0025] The power terminals 222 include a drain terminal and a source terminal. The signal terminals 223 include a gate terminal. The semiconductor element 221 according to this embodiment is a small element that does not include a temperature sensor. As shown in FIG. 7 , the power terminals 222 and the signal terminals 223 are electrically connected to the semiconductor element 221 by connecting wires 226.

[0026] The heat sink 224 is a metal block body that is in close contact with the semiconductor element 221 while being electrically insulated. The molded resin 225 molds and seals the semiconductor element 221, the power terminals 222, the signal terminals 223, and the heat sink 224. Parts of the power terminals 222 and the signal terminals 223 extend from the inside to the outside of the molded resin 225. One surface (exposed surface 224a) of the heat sink 224 is exposed from the molded resin 225.

[0027] An insulating sheet 24 having electrical insulation properties is disposed between the semiconductor module 22 and the housing 10. The semiconductor module 22 is thermally connected to the housing 10 via the insulating sheet 24. The semiconductor module 22 is pressed against the housing 10 by a clip member (not shown). Most of the surface of the semiconductor module 22 that is thermally connected to the housing 10 is a heat sink 224.

[0028] The semiconductor element 221 generates heat when current is applied. In the following description, the temperature of the semiconductor element 221 is referred to as element temperature TJ. If the element temperature TJ rises above its heat resistance temperature, there is a concern that the semiconductor element 221 may be damaged. On the other hand, the semiconductor element 221 according to this embodiment is a small element that does not include a temperature sensor. Therefore, the control circuit 30 estimates the element temperature TJ. Furthermore, if the estimated temperature exceeds a threshold value, the control circuit 30 limits or stops the output from the inverter circuit 20 to the motor device 7m. The control circuit 30 when estimating the element temperature TJ corresponds to an "element temperature estimation device." Note that the element temperature estimation device may include temperature sensors such as a high-temperature side sensor 41 and a low-temperature side sensor 42, which will be described later.

[0029] A portion of the heat generated in the semiconductor element 221 is transferred by thermal conduction to the heat sink 224, the insulating sheet 24, the housing 10, and the heat dissipation fins 11 in this order. The heat is then dissipated by heat transfer from the heat dissipation fins 11 to the outside air. In this way, the heat dissipation path from the semiconductor element 221 to the housing 10 corresponds to the first heat dissipation path R1 shown in FIGS. 7 and 8.

[0030] Furthermore, a portion of the heat generated in the semiconductor element 221 is transferred by thermal conduction to the power terminal 222 and then to the thick copper substrate 21. The heat is then dissipated by thermal conduction from the thick copper substrate 21 to the surrounding air. In this way, the heat dissipation path from the semiconductor element 221 to the thick copper substrate 21 corresponds to the second heat dissipation path R2 shown in FIGS. 7 and 8.

[0031] In the following description, the amount of heat generated in the semiconductor element 221 is referred to as the heat generation amount Q, the amount of heat transferred to the first heat dissipation path R1 is referred to as the first heat transfer amount Q1, and the amount of heat transferred to the second heat dissipation path R2 is referred to as the second heat transfer amount Q2. In addition to these heat dissipation paths, there is also a path in which heat conducted from the semiconductor element 221 to the molded resin 225 is dissipated into the inside air, for example. However, because the thermal conductivity of the molded resin 225 is extremely low compared to the heat sink 224 and the power terminals 222, which are made of metal, most of the heat generation amount Q is dissipated through the first heat dissipation path R1 and the second heat dissipation path R2.

[0032] It goes without saying that the first heat transfer amount Q1 is greater than the second heat transfer amount Q2. Measurements of the first heat transfer amount Q1 and the second heat transfer amount Q2 for the MCU 7i according to this embodiment revealed that the ratio of the first heat transfer amount Q1 to the second heat transfer amount Q2 was 7:3. This means that if an attempt is made to estimate the temperature of the semiconductor element 221 from the first heat transfer amount Q1 while ignoring the second heat transfer amount Q2, the estimation error will be large. Therefore, the element temperature estimation device according to this embodiment estimates the element temperature TJ by taking both the first heat transfer amount Q1 and the second heat transfer amount Q2 into consideration. The estimation method will be described in detail below.

[0033] 3, the element temperature estimation device includes a heat transfer amount estimation unit 30a1, an element temperature estimation unit 30a2, a high-temperature side sensor 41, and a low-temperature side sensor 42. The heat transfer amount estimation unit 30a1 and the element temperature estimation unit 30a2 are provided by the processor 30a executing a control program 30c. In other words, the processor 30a when estimating the heat transfer amount by executing the control program 30c corresponds to the heat transfer amount estimation unit 30a1. Furthermore, the processor 30a when estimating the element temperature TJ by executing the control program 30c corresponds to the element temperature estimation unit 30a2.

[0034] The high-temperature side sensor 41 and the low-temperature side sensor 42 are arranged on the first heat dissipation path R1. The high-temperature side sensor 41 is arranged closer to the semiconductor element 221 than the insulating sheet 24, and the low-temperature side sensor 42 is arranged closer to the housing 10 than the insulating sheet 24.

[0035] More specifically, the high-temperature-side sensor 41 is disposed between the insulating sheet 24 and the heat sink 224, and is in contact with both the heat sink 224 and the insulating sheet 24. It can be said that the high-temperature-side sensor 41 detects the temperature THS of the heat sink 224. The low-temperature-side sensor 42 is disposed between the insulating sheet 24 and the housing 10, and is in contact with both the housing 10 and the insulating sheet 24. It can be said that the low-temperature-side sensor 42 detects the temperature TC of the housing 10.

[0036] At least a portion of the low-temperature-side sensor 42 is located within the projection range W1 of the high-temperature-side sensor 41 in the direction perpendicular to the sheet surface of the insulating sheet 24. In the example of Fig. 7, the same temperature sensor is used for the high-temperature-side sensor 41 and the low-temperature-side sensor 42, and the entire low-temperature-side sensor 42 is located within the projection range W1.

[0037] The surface of the semiconductor element 221 that faces the housing 10 is defined as the element heat dissipation surface 221a. At least a portion of the low-temperature-side sensor 42 and at least a portion of the high-temperature-side sensor 41 are located within a projection range W2 of the element heat dissipation surface 221a in the direction perpendicular to the element heat dissipation surface 221a. In the example of Fig. 7, the high-temperature-side sensor 41 and the low-temperature-side sensor 42 are entirely located within a projection range W1.

[0038] 8, the thermal resistance differs for each portion of the first heat dissipation path R1 and the second heat dissipation path R2. For example, the thermal conductivity of the insulating sheet 24 is much lower than that of the heat sink 224 and the housing 10, which are made of metal. Therefore, although the thickness of the insulating sheet 24 is much smaller than that of the heat sink 224 and the housing 10, the thermal resistance RS of the insulating sheet 24 is greater than the thermal resistance RHS of the heat sink 224 and the thermal resistance RC of the housing 10.

[0039] The temperature THS of the heat sink 224 is lower than the element temperature TJ due to the thermal resistance RHS. The temperature TC of the housing 10 is lower than the temperature THS due to the thermal resistance RS. The temperature TF of the heat dissipation fin 11 is lower than the temperature TC due to the thermal resistance RC. The outside air temperature TA is lower than the temperature TF due to the thermal resistance RF. The inside air temperature TLF is lower than the element temperature TJ due to the thermal resistance RLF of the power terminal 222.

[0040] The test results shown in Figure 9 are a graph showing the relationship between the distance from the end face of the semiconductor module 22 and the temperature, i.e., the relationship between the distance from the exposed surface 224a of the heat sink 224 and the temperature. The magnitude of the temperature change with distance is called the temperature gradient. Within the first heat dissipation path R1, the temperature gradient in the insulating sheet 24 is greater than the temperature gradient in the housing 10.

[0041] The thermal resistance RF of the heat dissipation fin 11 is the largest among the first heat dissipation paths R1 because it is due to heat transfer rather than heat conduction. The heat sink 224 diffuses heat in a direction perpendicular to the first heat dissipation path R1, i.e., in a direction perpendicular to the radial direction of the housing 10. This increases the first heat transfer amount Q1.

[0042] Because the correlation between the temperature gradient and the first heat transfer quantity Q1 is high, the first heat transfer quantity Q1 can be estimated with high accuracy from the temperature gradient. Unlike the heat sink 224, thermal diffusion hardly occurs in the insulating sheet 24. Therefore, the correlation between the temperature gradient in the insulating sheet 24 and the first heat transfer quantity Q1 is higher than the correlation between the temperature gradient in the heat sink 224 and the first heat transfer quantity Q1. The difference between the temperatures detected by the high-side sensor 41 and the low-side sensor 42 is the difference between the temperature THS of the heat sink 224 and the temperature TC of the housing 10. This difference corresponds to the temperature gradient in the insulating sheet 24. In other words, the first heat transfer quantity Q1 can be estimated with high accuracy from the difference between the temperatures detected by the high-side sensor 41 and the low-side sensor 42.

[0043] In consideration of the above, the heat transfer amount estimator 30a1 estimates the first heat transfer amount Q1 using the equation Q1=(THS-TC) / RS shown in FIG. 3. That is, the heat transfer amount estimator 30a1 acquires the temperature THS detected by the high-temperature side sensor 41 and the temperature TC detected by the low-temperature side sensor 42. The heat transfer amount estimator 30a1 calculates the difference between the two acquired temperatures THS and TC. The memory 30b pre-stores the value of the thermal resistance RS of the insulating sheet 24. The heat transfer amount estimator 30a1 calculates the first heat transfer amount Q1 by dividing the difference by the thermal resistance RS. In short, the heat transfer amount estimator 30a1 estimates the first heat transfer amount Q1 based on the two temperatures THS and TC and the thermal resistance RS.

[0044] The element temperature estimator 30a2 estimates the element temperature TJ based on the temperature at an arbitrary position on the first heat dissipation path R1 and the thermal resistance value from the arbitrary position on the first heat dissipation path R1 to the semiconductor element 221. The temperature THS of the heat sink 224, i.e., the temperature detected by the high-temperature-side sensor 41, is used as the temperature at the arbitrary position. The element temperature TJ is calculated using the formula TJ = THS + RHS × Q1 shown in FIG. 3. That is, the element temperature estimator 30a2 multiplies the thermal resistance RHS of the heat sink 224 by the first heat transfer amount Q1 to calculate the temperature drop amount by which the element temperature TJ drops to the temperature THS of the heat sink 224. The element temperature estimator 30a2 calculates the element temperature TJ by adding the temperature THS of the heat sink 224 to the temperature drop amount. The memory 30b pre-stores the value of the thermal resistance RHS of the heat sink 224.

[0045] The control circuit 30 determines whether the element temperature TJ estimated by the element temperature estimator 30a2 is equal to or greater than a preset threshold. If it is determined that the element temperature TJ is equal to or greater than the threshold, the control circuit 30 reduces the output from the inverter circuit 20 to the motor device 7m, contrary to the output command from the FCU 5. Alternatively, the control circuit 30 forcibly stops the output from the inverter circuit 20 to the motor device 7m.

[0046] The heat transfer amount estimator 30a1 and the element temperature estimator 30a2 perform their estimations when the detected temperature is stable. That is, during a transient state where the change in the detected temperature per unit time is greater than a predetermined value, the estimation accuracy cannot be sufficiently ensured, and therefore the estimations are prohibited.

[0047] <Operation and effect of the first embodiment> The control circuit 30 (element temperature estimation device) according to this embodiment includes a heat transfer amount estimator 30a1 and an element temperature estimator 30a2. The heat transfer amount estimator 30a1 estimates a first amount of heat Q1 transferred through a first heat dissipation path R1. The element temperature estimator 30a2 estimates an element temperature TJ, which is the temperature of the semiconductor element 221, based on the first amount of heat transfer Q1 estimated by the heat transfer amount estimator 30a1.

[0048] Here, the larger the second heat transfer amount Q2, the smaller the first heat transfer amount Q1. In other words, if the element temperature TJ is estimated without considering the second heat transfer amount Q2, a temperature higher than the actual element temperature TJ will be estimated. In consideration of this, in this embodiment, the first heat transfer amount Q1 is first estimated. Therefore, the larger the second heat transfer amount Q2, the smaller the estimated first heat transfer amount Q1. Then, since the element temperature TJ is estimated based on the first heat transfer amount Q1 estimated in this way, it is possible to estimate the element temperature TJ to a highly accurate value that takes the second heat transfer amount Q2 into consideration. As described above, the control circuit 30 according to this embodiment can improve the estimation accuracy.

[0049] Furthermore, in this embodiment, the element temperature estimator 30a2 estimates the element temperature TJ based on the temperature at an arbitrary position on the first heat dissipation path R1 and the thermal resistance value from the arbitrary position on the first heat dissipation path R1 to the semiconductor element 221. For example, the arbitrary position is set at the boundary between the heat sink 224 and the insulating sheet 24. In this case, the temperature at the arbitrary position is the temperature THS of the heat sink 224, and the thermal resistance value is the thermal resistance RHS of the heat sink 224. Then, the element temperature TJ can be estimated according to the formula TJ=THS+RHS×Q1 shown in FIG. 3, for example, so that the element temperature TJ can be estimated with high accuracy.

[0050] Furthermore, in the element temperature estimation device according to this embodiment, a high-temperature side sensor 41 and a low-temperature side sensor 42 are provided on the heat dissipation path. The heat transfer amount estimator 30a1 estimates the heat transfer amount based on the temperature gradient, which is the difference between the temperatures detected by these sensors, and the thermal resistance value from the low-temperature side temperature measurement point to the high-temperature side temperature measurement point. This allows the heat transfer amount to be estimated with high accuracy, and ultimately the element temperature TJ to be estimated with high accuracy.

[0051] Furthermore, in this embodiment, the heat transfer amount estimator 30a1 estimates the first heat transfer amount Q1. An insulating sheet 24 having electrical insulation properties is disposed between the semiconductor element 221 and the housing 10. The high-temperature side temperature measurement point is set closer to the semiconductor element 221 than the insulating sheet 24, and the low-temperature side temperature measurement point is set closer to the housing 10 than the insulating sheet 24. As illustrated in FIG. 9, the insulating sheet 24 has a high thermal resistance, and its temperature drops significantly over a short heat dissipation path. In other words, the temperature gradient in the insulating sheet 24 is larger than that of the heat sink 224, etc. Moreover, because the insulating sheet 24 has a shorter heat dissipation path than the heat sink 224, the amount of heat diffused in a direction perpendicular to the heat dissipation path is small. As described above, according to this embodiment, in which temperatures are detected on both sides of the insulating sheet 24, the first heat transfer amount Q1 can be estimated with high accuracy. Consequently, the element temperature TJ can be estimated with high accuracy.

[0052] Furthermore, in this embodiment, at least a portion of the low-temperature-side sensor 42 is located within the projection range W1 of the high-temperature-side sensor 41 in the direction perpendicular to the sheet surface of the insulating sheet 24. Therefore, as described above, it is possible to detect a temperature gradient with reduced influence of diffusing heat, and therefore it is possible to estimate the first heat transfer amount Q1 with high accuracy.

[0053] Furthermore, in this embodiment, at least a portion of the low-temperature-side sensor 42 and at least a portion of the high-temperature-side sensor 41 are located within a projection range W2 in the vertical direction of the element heat dissipation surface 221a. This allows the first heat transfer amount Q1 to be estimated with high accuracy, and therefore the element temperature TJ to be estimated with high accuracy.

[0054] Furthermore, the element temperature estimation device according to this embodiment includes a heat sink 224 as a heat diffusion member. The heat sink 224 is thermally connected to the semiconductor element 221 and diffuses heat in a direction perpendicular to the first heat dissipation path R1. The high-temperature-side sensor 41 is in contact with this heat sink 224. This allows the first amount of heat transfer Q1 to be estimated with higher accuracy than when the high-temperature-side sensor 41 is disposed at a position in the semiconductor module 22 where it contacts the mold resin 225.

[0055] Furthermore, in this embodiment, the housing 10 is provided with heat dissipation fins 11. The low-temperature-side sensor 42 is in contact with the area of ​​the housing 10 where the heat dissipation fins 11 are provided. This allows the first heat transfer amount Q1 to be estimated with higher accuracy than when the low-temperature-side sensor 42 is disposed in an area of ​​the housing 10 where the heat dissipation fins 11 are not provided.

[0056] Furthermore, in this embodiment, the element temperature estimator 30a2 estimates the element temperature TJ based on the temperature at an arbitrary position on the first heat dissipation path R1 and the thermal resistance value from the arbitrary position on the first heat dissipation path R1 to the semiconductor element 221. The temperature at the arbitrary position is the temperature detected by either the high-temperature-side sensor 41 or the low-temperature-side sensor 42. In this way, the high-temperature-side sensor 41 or the low-temperature-side sensor 42 for detecting the temperature gradient can also be used to detect the temperature at the arbitrary position. This eliminates the need for a dedicated temperature sensor for detecting the temperature at the arbitrary position.

[0057] (Second embodiment) In the first embodiment, the temperature gradient of the heat dissipation path is detected by the high-temperature side sensor 41 and the low-temperature side sensor 42. Then, the heat transfer amount is estimated based on the detected temperature gradient and a pre-stored thermal resistance value. In contrast, in this embodiment, the heat transfer amount is estimated using a map described below.

[0058] The map shown in Fig. 10 is an example of the map and is stored in advance in the memory 30b serving as a storage device. This map shows the correspondence relationship between the heat generation amount Q, the airflow rate, and the first heat transfer amount Q1. The airflow rate refers to the amount of outside air blown to the heat dissipation fins 11 by the blower fan described above. Fig. 10 shows three examples of heat generation amounts Q: 30 W, 20 W, and 10 W.

[0059] The first heat transfer quantity Q1 and the calorific value Q are highly correlated, and the larger the calorific value Q, the larger the first heat transfer quantity Q1. The first heat transfer quantity Q1 and the airflow rate are also highly correlated, and the larger the airflow rate, the larger the first heat transfer quantity Q1. The correspondence relationship between the calorific value Q, the airflow rate, and the first heat transfer quantity Q1 is tested in advance, and a map created based on the test results is stored in memory 30b. However, in a range where the airflow rate is equal to or greater than a predetermined value, the first heat transfer quantity Q1 hardly changes even if the airflow rate changes. Therefore, the map may also show the correspondence relationship between the calorific value Q and the first heat transfer quantity Q1, instead of the correspondence relationship between the calorific value Q, the airflow rate, and the first heat transfer quantity Q1.

[0060] As shown in FIG. 11, the element temperature estimation device includes a heat generation amount calculation unit 30a3. The heat generation amount calculation unit 30a3 is provided by the processor 30a executing the control program 30c. In other words, the processor 30a when estimating the heat generation amount Q by executing the control program 30c corresponds to the heat generation amount calculation unit 30a3. The heat generation amount calculation unit 30a3 acquires a voltage value V applied to the semiconductor element 221 and a current value I flowing through the semiconductor element 221. A specific example of the acquired voltage value V is the detected battery voltage. A specific example of the acquired current value I is the detection value of a current sensor included in the inverter circuit 20. The heat generation amount calculation unit 30a3 calculates the heat generation amount Q from the current value I and the voltage value V.

[0061] The rotation speed sensor 43 detects the number of rotations per unit time (i.e., the rotation speed) of the blower fan. The heat transfer amount estimator 30a1 calculates the airflow rate based on the detected value of the rotation speed sensor 43. Furthermore, the heat transfer amount estimator 30a1 estimates the first heat transfer amount Q1 by referring to the map based on the acquired heat generation amount Q and airflow rate. The element temperature estimator 30a2 calculates the element temperature TJ according to the formula TJ=THS+RHS×Q1, as in the first embodiment.

[0062] As described above, in this embodiment, a map showing at least the correspondence relationship between the heat generation amount Q and the first heat transfer amount Q1 is pre-stored in the memory 30b serving as a storage device. The heat transfer amount estimator 30a1 estimates the first heat transfer amount Q1 by referring to the map based on the heat generation amount Q. The element temperature estimator 30a2 then estimates the element temperature TJ based on the estimated first heat transfer amount Q1. That is, similar to the first embodiment, the first heat transfer amount Q1, which changes depending on the second heat transfer amount Q2, is estimated, and the element temperature TJ is estimated based on the first heat transfer amount Q1. This improves the accuracy of estimating the element temperature TJ. Furthermore, this embodiment eliminates the need to detect a temperature gradient, thereby reducing the number of temperature sensors required to estimate the element temperature TJ.

[0063] Furthermore, in this embodiment, the amount of outside air blown by the blower fan to the heat dissipation fins 11 is acquired. Then, the first heat transfer amount Q1 is estimated based on the heat generation amount Q, taking the amount of air blown into consideration, so that the estimation accuracy of the first heat transfer amount Q1 can be further improved.

[0064] (Third embodiment) In the first and second embodiments, the element temperature TJ is estimated based on the temperature at an arbitrary position on the first heat dissipation path R1 and the first heat transfer amount Q1. In contrast, in the present embodiment, the element temperature TJ is estimated based on the temperature at an arbitrary position on the second heat dissipation path R2 and the second heat transfer amount Q2. The arbitrary position on the second heat dissipation path R2 may be set to the tip surface of the power terminal 222. Furthermore, the temperature of the tip surface of the power terminal 222 may be considered to be equivalent to the inside air temperature TLF, and the inside air temperature TLF may be used as the temperature at the arbitrary position.

[0065] More specifically, in the second embodiment, the element temperature TJ is calculated according to the formula TJ=THS+RHS×Q1. In contrast, in this embodiment, the element temperature TJ is calculated according to the formula TJ=TLF+RLF×(Q−Q1) shown in FIG. 12. TLF is the inside air temperature, and RLF is the thermal resistance of the power terminal 222. Furthermore, (Q−Q1) corresponds to the second heat transfer amount Q2.

[0066] The heat generation amount calculation unit 30a3 and the heat transfer amount estimation unit 30a1 according to this embodiment are the same as those in the second embodiment and estimate the first heat transfer amount Q1 by referring to a map. The element temperature estimation unit 30a2 according to this embodiment calculates the second heat transfer amount Q2 by subtracting the first heat transfer amount Q1 calculated by the heat transfer amount estimation unit 30a1 from the heat generation amount Q calculated by the heat generation amount calculation unit 30a3. Furthermore, the element temperature estimation unit 30a2 multiplies the thermal resistance RLF of the power terminal 222 by the second heat transfer amount Q2 to calculate the temperature drop amount by which the element temperature TJ has dropped to the inside air temperature TLF. Furthermore, the element temperature estimation unit 30a2 calculates the element temperature TJ by adding the inside air temperature TLF to the temperature drop amount. The value of the thermal resistance RLF of the power terminal 222 is pre-stored in the memory 30b.

[0067] As described above, in this embodiment, the element temperature estimator 30a2 calculates the second heat transfer amount Q2 based on the estimated first heat transfer amount Q1 and the heat generation amount Q. Then, the element temperature TJ is estimated based on the second heat transfer amount Q2. That is, the second heat transfer amount Q2, which changes depending on the first heat transfer amount Q1, is estimated, and the element temperature TJ is estimated based on the second heat transfer amount Q2. Therefore, the estimation accuracy of the element temperature TJ can be improved. Furthermore, according to this embodiment, it is not necessary to provide a temperature sensor in the first heat dissipation path R1.

[0068] (Other embodiments) In each of the above embodiments, the electric aircraft on which the EPU 7 is mounted may be an aircraft without gliding wings 3b, or may be an unmanned aircraft. The element temperature estimation device according to each of the above embodiments is applied to a power conversion device (MCU 7i) mounted on an electric aircraft, but may also be applied to a power conversion device mounted on a vehicle or a stationary power conversion device.

[0069] The power conversion device to which the element temperature estimation device according to each of the above embodiments is applied is an MCU 7i having an inverter circuit 20, but may also be a power conversion device having a boost circuit that boosts voltage. In the power conversion device to which the element temperature estimation device according to each of the above embodiments is applied, the load to which power is output is a motor device 7m. However, the load may also be an electric actuator other than a motor.

[0070] The EPU 7 according to each of the above embodiments has one MCU 7i for one motor device 7m. The EPU 7 according to other embodiments may have two MCUs 7i for one motor device 7m.

[0071] In the first embodiment, the high-temperature-side sensor 41 and the low-temperature-side sensor 42 do not have to be located in contact with the front and back surfaces of the insulating sheet 24 as long as they are located on the first heat dissipation path R1. In the first embodiment, the high-temperature-side sensor 41 and the low-temperature-side sensor 42 may be located on the second heat dissipation path R2. In this case, the temperature gradient at a predetermined position on the second heat dissipation path R2 is detected, and the second amount of heat transfer Q2 is calculated based on the temperature gradient. The first amount of heat transfer Q1 may also be calculated by subtracting the second amount of heat transfer Q2 calculated in this manner from the amount of heat generated Q. [Explanation of symbols]

[0072] 30 Control circuit (element temperature estimation device) 10 Housing, 11 Heat dissipation fin, 21 Wiring board, 221 Semiconductor element, 221a Element heat dissipation surface, 224 Heat diffusion member, 24 Insulating sheet, 30a1 Heat transfer amount estimation unit, 30a2 Element temperature estimation unit, 30b Memory device, 41 High temperature side sensor, 42 Low temperature side sensor, 7i MCU (power conversion device), 7m1 Load, Q Heat generation amount, Q1 First heat transfer amount, Q2 Second heat transfer amount, R1 First heat dissipation path, R2 Second heat dissipation path, W1, W2 Projection range.

Claims

1. A wiring board (21), a semiconductor element (221) connected to the wiring of the wiring board and performing a switching operation to convert power supplied from a power source and output it to a load (7m1); a housing (10) that accommodates the semiconductor element therein and is thermally connected to the semiconductor element; In the element temperature estimation device applied to a power conversion device (7i) having a first heat dissipation path (R1) that is a heat dissipation path from the semiconductor element to the housing, and a second heat dissipation path (R2) that is a heat dissipation path from the semiconductor element to the wiring board, a heat transfer amount estimation unit (30a1) that estimates a first heat transfer amount (Q1) that is transferred through the first heat dissipation path or a second heat transfer amount (Q2) that is transferred through the second heat dissipation path; an element temperature estimation unit (30a2) that estimates an element temperature, which is the temperature of the semiconductor element, based on the heat transfer amount estimated by the heat transfer amount estimation unit; An element temperature estimation device comprising:

2. the heat transfer amount estimating unit estimates the first heat transfer amount, 2. The element temperature estimation device according to claim 1, wherein the element temperature estimation unit estimates the element temperature based on a temperature at an arbitrary position on the first heat dissipation path and a thermal resistance value from the arbitrary position on the first heat dissipation path to the semiconductor element.

3. the heat transfer amount estimating unit estimates the second heat transfer amount, 2. The element temperature estimation device according to claim 1, wherein the element temperature estimation unit estimates the element temperature based on a temperature at an arbitrary position on the second heat dissipation path and a thermal resistance value from the arbitrary position on the second heat dissipation path to the semiconductor element.

4. The heat dissipation path includes a high-temperature side sensor (41) disposed at a high-temperature side temperature measurement point in either the first heat dissipation path or the second heat dissipation path, and a low-temperature side sensor (42) disposed at a low-temperature side temperature measurement point located on the low-temperature side of the high-temperature side temperature measurement point, 2. The element temperature estimation device according to claim 1, wherein the heat transfer amount estimation unit estimates the heat transfer amount based on a temperature gradient, which is the difference between the temperature detected by the high-temperature side sensor and the temperature detected by the low-temperature side sensor, and a thermal resistance value from the low-temperature side temperature measurement point to the high-temperature side temperature measurement point.

5. the heat transfer amount estimating unit estimates the first heat transfer amount, An insulating sheet (24) having electrical insulation properties is disposed between the semiconductor element and the housing, The high-temperature side temperature measuring point is set closer to the semiconductor element than the insulating sheet, The element temperature estimation device according to claim 4 , wherein the low-temperature side temperature measurement point is set closer to the housing than the insulating sheet.

6. 6. The element temperature estimation device according to claim 5, wherein at least a portion of the low-temperature-side sensor is located within a projection range (W1) of the high-temperature-side sensor in the direction of the first heat dissipation path.

7. The surface of the semiconductor element facing the housing is an element heat dissipation surface (221a), 7. The element temperature estimation device according to claim 5, wherein at least a portion of the low-temperature-side sensor and at least a portion of the high-temperature-side sensor are located within a projection range (W2) of the element heat dissipation surface in the direction of the first heat dissipation path.

8. a heat diffusion member (224) thermally connected to the semiconductor element to diffuse heat; 6. The element temperature estimation device according to claim 4, wherein the high-temperature side sensor is in contact with the heat diffusion member.

9. The housing is provided with heat dissipation fins (11), 6. The element temperature estimation device according to claim 4, wherein the low-temperature-side sensor is in contact with a region of the housing where the heat dissipation fins are provided.

10. the heat transfer amount estimating unit estimates the first heat transfer amount, the element temperature estimating unit estimates the element temperature based on a temperature at an arbitrary position on the first heat dissipation path and a thermal resistance value from the arbitrary position on the first heat dissipation path to the semiconductor element; 6. The element temperature estimation device according to claim 4, wherein the temperature at the arbitrary position is a temperature detected by either the high-temperature side sensor or the low-temperature side sensor.

11. a storage device (30b) in which a map showing a correspondence relationship between the amount of heat generated (Q) in the semiconductor element and the first amount of heat transfer is stored in advance; The element temperature estimation device according to claim 1 , wherein the heat transfer amount estimating unit estimates the first heat transfer amount by referring to the map based on the heat generation amount.

12. a storage device (30b) in which a map showing a correspondence relationship between the heat generation amount (Q) in the semiconductor element and the first heat transfer amount is stored in advance; 2. The element temperature estimation device according to claim 1, wherein the heat transfer amount estimator estimates the second heat transfer amount by subtracting the first heat transfer amount, which is calculated by referring to the map based on the heat generation amount, from the heat generation amount.

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