Over-current detection device, over-current detection method, semiconductor DC circuit breaker, and power conversion device

Abstract

Provided is an overcurrent detection device with high overcurrent detection accuracy even when there is a location where the temperature is unknown due to an instantaneous large current. A concentrated overcurrent detection device (11) is provided with: an instantaneous current estimation unit (101) that estimates an estimated instantaneous current (I) at a temperature-unknown site (X) on the basis of a measured instantaneous voltage (V) of a conductor (111) and an estimated resistance (R) at the temperature-unknown site (X) of the conductor (111); an overcurrent determination unit (102) that determines whether there is an overcurrent on the basis of the estimated instantaneous current (I); a power consumption calculation unit (103) that calculates power consumption (P) on the basis of the instantaneous voltage (V) and the estimated instantaneous current (I); a thermal equivalent circuit (Tmodel) that takes into account at least the thermal resistance (Rth) and the thermal capacity (Rth) of the conductor (111); a temperature estimation unit (104) that estimates and updates the temperature (T) of a region (X) at which the temperature is unknown, on the basis of the power consumption (P) and the known temperatures (Ta, Tt) of at least one region of the conductor (111); and a resistance estimation unit (105) that updates, on the basis of the updated temperature (T), the estimated resistance (R) of the portion (X) at which the temperature is unknown.

Description

Technical Field

[0001] This invention relates to an overcurrent detection device, an overcurrent detection method, a semiconductor DC circuit breaker, and a power conversion device. Background Technology

[0002] In the event of an overcurrent, the overcurrent is detected by an overcurrent detection device, and the semiconductor switching element of the semiconductor DC circuit breaker is controlled to cut off the current, or to protect the semiconductor switching element used in the power conversion device.

[0003] As a technique for measuring current, for example, there is Patent Document 1. In Patent Document 1... Figure 5 Paragraph 0048 describes the following technique: measuring voltage V1(T) which depends on temperature T and voltage V2(I, T) which depends on current I and temperature T, and calculating current I based on the measured voltages V1 and V2.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2007-187667 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] However, Patent Document 1 is based on the premise of accurately determining the temperature T when measuring voltage V2.

[0009] For example, when a large current flows instantaneously, it can sometimes become locally hot in a location different from where the temperature T is accurately determined. The characteristics of current, voltage, and resistance are temperature-dependent. Therefore, in the presence of locations with unknown temperatures, even calculating the current based on the measured voltage will introduce errors, resulting in reduced accuracy in overcurrent detection.

[0010] The problem to be solved by the present invention is to provide an overcurrent detection device, an overcurrent detection method, a semiconductor DC circuit breaker using the overcurrent detection device, and a power conversion device that have high overcurrent detection accuracy even in situations where the temperature is unknown, such as due to a large instantaneous current flow.

[0011] Methods for solving problems

[0012] To address the aforementioned issues, the overcurrent detection device / method of the present invention is characterized by comprising: an instantaneous current estimation unit / step, which estimates an estimated instantaneous current I of the unknown temperature region X in the conductor based on an instantaneous voltage V measured at a predetermined measurement location in the conductor and an estimated resistance R of an unknown temperature region X in the conductor; an overcurrent determination unit / step, which determines whether an overcurrent is present based on the estimated instantaneous current I; a power consumption calculation unit / step, which calculates the power consumption P based on the instantaneous voltage V and the estimated instantaneous current I; a temperature estimation unit / step, which estimates and updates the temperature T of the unknown temperature region X in the conductor based on a thermal equivalent circuit that considers at least the thermal resistance and thermal capacity of the conductor, the power consumption P, and a known temperature of at least one location in the conductor; and a resistance estimation unit / step, which updates the estimated resistance R of the unknown temperature region X in the conductor based on the temperature T updated in the temperature estimation unit / step.

[0013] Furthermore, the semiconductor DC circuit breaker of the present invention includes: the above-described overcurrent detection device; a semiconductor switching element; and a control unit that, when the overcurrent determination unit determines that it is an overcurrent, controls the semiconductor switching element to cut off the main current flowing through the semiconductor switching element.

[0014] Furthermore, the power conversion device of the present invention includes: the above-described overcurrent detection device; a power conversion circuit configured using a semiconductor switching element; and a protection circuit that, when the overcurrent determination unit determines that it is an overcurrent, performs control to protect the semiconductor switching element.

[0015] Invention Effects

[0016] According to the present invention, even in cases where the temperature is unknown due to a large instantaneous current flow, a high-accuracy overcurrent detection device, an overcurrent detection method, a semiconductor DC circuit breaker using the overcurrent detection device, and a power conversion device can be realized. Attached Figure Description

[0017] Figure 1 This is a functional block diagram of the overcurrent detection device in Example 1.

[0018] Figure 2 This is a top view illustrating an example of the shape of a conductor.

[0019] Figure 3 Is with Figure 2 The corresponding thermal equivalent circuit.

[0020] Figure 4 This is a top view illustrating other examples of the shape of a conductor.

[0021] Figure 5 Is with Figure 4 The corresponding thermal equivalent circuit.

[0022] Figure 6 This is a graph illustrating the thermal time constant.

[0023] Figure 7 This is a diagram illustrating the conditions of a simulation used to explain the effect of Example 1.

[0024] Figure 8 This is a graph showing the simulation results used to illustrate the effects of Example 1.

[0025] Figure 9 This is a circuit diagram of the semiconductor DC circuit breaker and semiconductor module of Example 2.

[0026] Figure 10 This is a perspective view of the semiconductor module in Example 2.

[0027] Figure 11 This is a three-dimensional view of the interior of the semiconductor module in Example 2.

[0028] Figure 12 This is a top view of the interior of the semiconductor module in Example 2.

[0029] Figure 13 This is a top view of the interior of the semiconductor module in Example 2.

[0030] Figure 14 This is a top view of the first external terminal of the semiconductor module and the fuse in Embodiment 2.

[0031] Figure 15 This is a circuit diagram of the semiconductor DC circuit breaker and semiconductor module of Example 3.

[0032] Figure 16 This is a three-dimensional view of the interior of the semiconductor module in Example 3.

[0033] Figure 17 This is a top view of the interior of the semiconductor module in Example 3.

[0034] Figure 18 This is a circuit diagram of the semiconductor DC circuit breaker and semiconductor module of Example 4.

[0035] Figure 19 This is a circuit diagram of the semiconductor DC circuit breaker and semiconductor module of Example 5.

[0036] Figure 20 This is a circuit diagram of the semiconductor DC circuit breaker and semiconductor module of Example 6.

[0037] Figure 21 This is a circuit diagram of the semiconductor DC circuit breaker and semiconductor module of Example 7.

[0038] Figure 22 This is a functional block diagram of the power conversion device in Example 8. Detailed Implementation

[0039] Hereinafter, embodiments of the present invention will be described using the accompanying drawings. In the various figures and embodiments, the same or similar constituent elements are labeled with the same reference numerals, and repeated descriptions are omitted.

[0040] Example 1

[0041] Figure 1 This is a functional block diagram of the overcurrent detection device in Example 1. Figure 2 This is a top view illustrating an example of the shape of a conductor. Figure 3 Is with Figure 2 The corresponding thermal equivalent circuit.

[0042] The overcurrent detection device 11 of Embodiment 1 is input with an instantaneous voltage V measured at a predetermined measurement location of the conductor 111, which is the object of measurement, and a known temperature (e.g., substrate temperature Ta and terminal temperature Tt) of at least one location of the conductor 111. Based on the thermal equivalent circuit Tmodel that takes into account at least the thermal resistance Rth and thermal capacity Cth of the conductor 111, as well as the input instantaneous voltage V and the known temperature, it estimates the estimated instantaneous current I of the unknown temperature location X in the conductor 111. Based on the estimated instantaneous current I, it determines whether it is an overcurrent. If it is determined to be an overcurrent, it outputs an overcurrent detection signal 107.

[0043] As a specific structure, the overcurrent detection device 11 of this embodiment has an instantaneous current estimation unit 101, an overcurrent determination unit 102, a power consumption calculation unit 103, a temperature estimation unit 104, a resistance estimation unit 105, and a thermal equivalent circuit storage unit 106 as functional blocks. Each functional block can be implemented, for example, by executing a program on a computer system such as a microcomputer.

[0044] Next, the details of each functional block of the overcurrent detection device 11 in this embodiment and the overcurrent detection method will be described.

[0045] In the instantaneous current estimation step, the instantaneous current estimation unit 101 estimates the estimated instantaneous current I of the unknown temperature location X in the conductor 111 based on the instantaneous voltage V measured at a predetermined measurement location in the conductor 111 and the estimated resistance R of the unknown temperature location X in the conductor 111. The estimated instantaneous current I can be obtained, for example, by using a formula such as "I = V / R".

[0046] In the overcurrent determination step, the overcurrent determination unit 102 determines whether there is an overcurrent based on the estimated instantaneous current I. The determination of whether there is an overcurrent can be made, for example, by using a formula such as "I≥ILIM" to determine whether the estimated instantaneous current I is greater than or equal to the threshold ILIM. If this formula is satisfied, the overcurrent determination unit 102 determines that there is an overcurrent and outputs an overcurrent detection signal 107.

[0047] In the power consumption calculation step, the power consumption calculation unit 103 calculates the power consumption P based on the instantaneous voltage V and the estimated instantaneous current I. The power consumption P can be obtained, for example, by using a formula such as "P = IV". The power consumption P corresponds to the power consumption of the part X with an unknown temperature.

[0048] In the temperature estimation step, the temperature estimation unit 104 estimates and updates the temperature T of an unknown location X in the conductor 111 based on the thermal equivalent circuit Tmodel, which takes into account at least the thermal resistance Rth and heat capacity Cth of the conductor 111, the power consumption P, and the known temperatures of at least one location of the conductor 111 (e.g., substrate temperature Ta and terminal temperature Tt). The temperature T can be expressed, for example, by a formula such as "T = f(Tmodel, P, Ta, Tt)". Details of the thermal equivalent circuit Tmodel and the method for estimating the temperature T will be described later.

[0049] In the resistance estimation step, the resistance estimation unit 105 updates the estimated resistance R of the unknown temperature portion X in the conductor 111 based on the temperature T updated by the temperature estimation unit 104. The estimated resistance R depends on the temperature T, so it can be calculated using coefficients a and b, for example, by using a formula such as "R = aT + b".

[0050] The instantaneous current estimation step, overcurrent determination step, power consumption calculation step, temperature estimation step, and resistance estimation step are repeatedly executed at a predetermined cycle. The estimated resistance R updated in the resistance estimation step is used in the next instantaneous current estimation step.

[0051] The thermal equivalent circuit Tmodel is pre-stored in the thermal equivalent circuit storage unit 106.

[0052] Next, we will refer to Figure 2 and Figure 3 Describe the details of the thermal equivalent circuit Tmodel.

[0053] like Figure 2As shown, the conductor 111, which is the object of measurement, is configured to have a first portion 111A, a second portion 111B, and a portion X with an unknown temperature existing between the first portion 111A and the second portion 111B. Here, as an example of the conductor 111, we will describe the case where a terminal of a semiconductor module through which the main current flows is used. This terminal is connected to a semiconductor switching element provided inside the semiconductor module.

[0054] The first part 111A is connected to the substrate side where a semiconductor switching element is disposed. It is assumed that the temperature of the first part 111A is equal to the substrate temperature Ta. The substrate temperature Ta can be measured, for example, by a thermistor, thermocouple, etc. disposed on the substrate, and is assumed to be known.

[0055] The second part 111B is the side of the terminal that is connected to the outside. It is assumed that the temperature of the second part 111B is equal to the terminal temperature Tt. The terminal temperature Tt is assumed to be known, for example, by means of a thermistor installed in a busbar, etc. Furthermore, it is assumed that an instantaneous voltage V is measured in the second part 111B.

[0056] The width of the portion X with unknown temperature is smaller than that of the first portion 111A and the second portion 111B. Therefore, for example, in the case of a large current flowing instantaneously, it is assumed that the temperature T of this portion is higher than the temperature of the first portion 111A and the second portion 111B, whose temperatures are known. Therefore, the heat dissipation direction 112 of the first portion 111A and the second portion 111B becomes... Figure 2 direction shown.

[0057] Here, the characteristics of current, voltage, and resistance are temperature-dependent. Therefore, if there is a part X in conductor 111 with an unknown temperature, even if the current is calculated based on the measured instantaneous voltage V without considering the temperature T of the unknown part X, errors will occur, resulting in a decrease in the accuracy of overcurrent detection.

[0058] Therefore, in this embodiment, the temperature T of the unknown part X in conductor 111 is estimated by using a thermal equivalent circuit Tmodel that takes into account at least the thermal resistance Rth and thermal capacity Cth of conductor 111.

[0059] like Figure 3 As shown, with Figure 2 The corresponding thermal equivalent circuit Tmodel has the following structure: In the first part 111A, the thermal resistance Rth1 and the heat capacity Cth1 are connected in parallel; in the second part 111B, the thermal resistance Rth2 and the heat capacity Cth2 are connected in parallel; and in the part X where the temperature is unknown, they are connected in series.

[0060] For example, when the thermal conductivity of the second part 111B is λ, the specific heat capacity is c, the density is d, the cross-sectional area is A, and the length is l, the thermal resistance Rth2 = l / λA and the heat capacity Cth2 = cdAl can be calculated. The thermal resistance Rth1 and the heat capacity Cth1 of the first part 111A can be calculated in the same way.

[0061] In the thermal equivalent circuit Tmodel, the consumed power P corresponds to the current, the temperature T corresponds to the voltage, and the loss, which is the integral of the consumed power P, corresponds to the charge, which is the integral of the current. Therefore, the consumed power P generated at the unknown temperature location X flows from temperature T toward the substrate temperature Ta, through the thermal resistance Rth1 via the consumed power P1R, through the heat capacity Cth1 via the consumed power P1C, and from temperature T toward the terminal temperature Tt, through the thermal resistance Rth2 via the consumed power P2R, through the heat capacity Cth2 via the consumed power P2C. Therefore, as the thermal equivalent circuit Tmodel, at time t, the following equations (1) and (2) hold.

[0062] [Formula 1]

[0063]

[0064] [Equation 2]

[0065]

[0066] Figure 4 This is a top view illustrating other examples of the shape of a conductor. Figure 5 Is with Figure 4 The corresponding thermal equivalent circuit.

[0067] like Figure 4 As shown, when the second part 111B of conductor 111 is composed of a third part 111B1 with a cross-sectional area A1 and a length l1 and a fourth part 111B2 with a cross-sectional area A2 and a length l2, as Figure 5 As shown, the thermal equivalent circuit Tmodel of the second part 111B can be represented using the thermal resistance Rth21 and thermal capacity Cth21 of the third part 111B1 and the thermal resistance Rth22 and thermal capacity Cth22 of the fourth part 111B2. Here, the structure of the second part 111B of conductor 111 divided into two segments is used as an example, but when it is divided into three or more segments, the thermal equivalent circuit Tmodel can also be represented by extending the same idea.

[0068] In addition, when the shape of conductor 111 is complex, the temperature rise of conductor 111 can be calculated by simulation, and the parameters of the thermal equivalent circuit Tmodel can be estimated.

[0069] Figure 6 This is a diagram illustrating the thermal time constant. In Figure 6 In the figure, the horizontal axis represents time t, and the vertical axis represents the terminal temperature Tt, both expressed on a logarithmic scale.

[0070] For example, imagine applying a voltage V' to the second portion 111B of conductor 111 and allowing a current I' to flow through it, such as Figure 6 The diagram illustrates the change from an initial temperature Tt0 to a steady-state temperature Tt'. In this case, the thermal time constant τ is defined as the time required for the temperature to change by 63.2% from the initial temperature Tt0 to the steady-state temperature Tt'. Furthermore, in cases such as... Figure 3 Given the thermal equivalent circuit Tmodel of the second part 111B as shown, it can be obtained from the thermal resistance Rth2=Tt' / I'V' and the thermal capacity Cth2=τ / Rth2.

[0071] Furthermore, the simulation results are obtained only through, for example Figure 3 In cases where the thermal resistance Rth and heat capacity Cth of a single element, as shown, cannot be expressed with high precision, for example... Figure 5 The accuracy can be improved by increasing the number of elements such as thermal resistance Rth and heat capacity Cth as shown.

[0072] Next, the method for estimating the temperature T in the temperature estimation section 104 will be explained.

[0073] The temperature estimation unit 104 estimates the temperature T by setting the initial value of the temperature T to be equal to the initial value of the known temperature (e.g., substrate temperature Ta and terminal temperature Tt) of at least one part of the conductor 111.

[0074] Here, it is assumed that conductor 111 is Figure 2 The shape shown Figure 3 The thermal equivalent circuit Tmodel is established for explanation. In this case, equations (1) and (2) above hold. The integral equation of equation (2) is solved by numerical solution.

[0075] Assuming that the power consumption P is 0 and the temperature T, substrate temperature Ta and terminal temperature Tt are equal as initial values, then the following equation (3) holds.

[0076] [Formula 3]

[0077]

[0078] Given the initial value, P(t) = I(t)·V(t) as the history of power consumption P, and Ta(t) and Tt(t) as the history of known temperature, calculate T(t) as the history of temperature T.

[0079] If we differentiate equation (2) using t, it becomes equation (4).

[0080] [Formula 4]

[0081]

[0082] Assuming that the instantaneous voltage V, substrate temperature Ta, and terminal temperature Tt are measured at predetermined sampling intervals Δt, the differential can be replaced by the difference between the measured values ​​divided by the difference at time t (=Δt). Therefore, equation (4) becomes equation (5). In addition, the superscript n+1 represents the updated value in this process, and n represents the value before the update in this process.

[0083] [Formula 5]

[0084]

[0085] In equation (5), by replacing the temperature difference ΔT, the time difference Δt, the substrate temperature difference ΔTa, and the terminal temperature difference ΔTt as in equation (6) below, the equation becomes equation (7) below.

[0086] [Formula 6]

[0087]

[0088] [Formula 7]

[0089]

[0090] Equation (1) also holds true in the updated value in this process. Therefore, rewriting equation (1) with the superscript subscript being n+1, substituting it into equation (7) and rearranging it, we get equation (8).

[0091] [Formula 8]

[0092]

[0093] If we solve equation (8) for ΔT, it becomes equation (9).

[0094] [Formula 9]

[0095]

[0096] In equation (9), the updated value of the power consumption P (superscript n+1) can be the power consumption P calculated by the power consumption calculation unit 103. The values ​​of P1R and P2R before the update (superscript n) can be the values ​​obtained by equation (7) in the previous processing. ΔTa and ΔTt can be the difference between the current measurement value and the previous measurement value. Δt can be the specified sampling interval Δt. Rth1, Rth2, Cth1, and Cth2 can be the values ​​used in the thermal equivalent circuit Tmodel. Therefore, ΔT can be obtained by equation (9). In addition, after obtaining ΔT, the updated values ​​of P1R and P2R (superscript n+1) are obtained by equation (7) for the next processing.

[0097] By calculating the difference ΔT of temperature T, the updated value of temperature T in this process (with superscript n+1) is obtained using the following formula (10).

[0098] [Formula 10]

[0099]

[0100] By performing the above process, the temperature estimation unit 104 can estimate the temperature T.

[0101] Next, the results of verifying the current estimation accuracy of the method in this embodiment by simulating a transient large current will be explained.

[0102] Figure 7 This is a diagram showing the conditions of the simulation used to illustrate the effect of Example 1. Figure 8 This is a graph showing the results of a simulation used to illustrate the effects of Example 1. Figure 7 and Figure 8 In the diagram, the horizontal axis represents time t. Figure 7 The vertical axis represents the current. Figure 8 The vertical axis represents the estimated instantaneous current I.

[0103] Here, as Figure 7 As shown, assuming a cross-sectional area of ​​12mm 2 A conductor 111 with a length of 40 mm was energized with a stable current of 500 A, resulting in a maximum instantaneous current of 5000 A within 1000 μs. Furthermore, as a thermal equivalent circuit Tmodel, simulations were performed using three methods to calculate the estimated instantaneous current I: Comparative Example 1, which did not consider thermal resistance Rth and thermal capacity Cth; Comparative Example 2, which only considered thermal resistance Rth; and the method of this embodiment, which considered thermal resistance Rth and thermal capacity Cth.

[0104] like Figure 8 As shown, the curve of 121 without considering RC in Comparative Example 1 is compared to... Figure 7The current shown is large, and the estimated instantaneous current I is overestimated. Furthermore, the curve for R considering 122 in Comparative Example 2 is larger than... Figure 7 The current shown is small, which is too small to evaluate the estimated instantaneous current I. On the other hand, the RC consideration diagram 123 based on the method of this embodiment becomes close to... Figure 7 The current results shown confirm that the current estimation accuracy is high.

[0105] As explained above, according to this embodiment, even in cases where the temperature is unknown due to a large instantaneous current flow, an overcurrent detection device and overcurrent detection method with high overcurrent detection accuracy can be realized.

[0106] Example 2

[0107] Example 2 is an example of a semiconductor DC circuit breaker 1 using the overcurrent detection device 11 of Example 1.

[0108] Figure 9 This is a circuit diagram of the semiconductor DC circuit breaker and semiconductor module of Example 2.

[0109] The semiconductor DC circuit breaker 1 of Embodiment 2 is connected between the power supply 3 and the protected device 4, and interrupts the current when an overcurrent is detected. Here, the semiconductor DC circuit breaker 1 includes: a semiconductor switching element 21 that interrupts the main current when an overcurrent is detected; a fuse 25 connected in series with the semiconductor switching element 21; a voltage detection unit 14 that detects the voltage at a predetermined measurement point; a temperature detection unit 15 that detects the temperature at a predetermined point; an overcurrent detection device 11 of Embodiment 1 that detects the overcurrent based on the voltage detected by the thermal equivalent circuit Tmodel and the voltage detection unit 14 (corresponding to the instantaneous voltage V of Embodiment 1) and the temperature detected by the temperature detection unit 15 (corresponding to the substrate temperature Ta and terminal temperature Tt of Embodiment 1); and a control unit 12 that disconnects the semiconductor switching element 21 when an overcurrent is detected by the overcurrent detection device 11.

[0110] In other words, the semiconductor DC circuit breaker 1 of this embodiment has the overcurrent detection device 11 of embodiment 1, the semiconductor switching element 21, and the control unit 12 that controls the semiconductor switching element 21 to cut off the main current flowing through the semiconductor switching element 21 when the overcurrent determination unit 102 of the overcurrent detection device 11 determines that there is an overcurrent.

[0111] Furthermore, the magnitude of the overcurrent that causes the semiconductor switching element 21 to disconnect is set to be smaller than the fusing current of the fuse 25. Specifically, the semiconductor DC circuit breaker 1 has a fuse 25 connected in series with the semiconductor switching element 21, and the overcurrent determination unit 102 of the overcurrent detection device 11 determines an overcurrent when the estimated instantaneous current I is above a predetermined threshold ILIM, which is smaller than the fusing current of the fuse 25. In addition, the fusing current of the fuse 25 is set below the allowable current of the protected device 4.

[0112] With this structure, when an overcurrent flows, it is possible to detect the overcurrent and disconnect the semiconductor switching element 21 before the fuse 25 blows to interrupt the current. Therefore, the semiconductor DC circuit breaker 1 can be reused, and even if the semiconductor switching element 21 fails due to cosmic rays or the like, the current can still be interrupted by the fuse 25 connected in series. That is, it has redundancy that allows the current to be interrupted even if the semiconductor switching element 21 used to interrupt the current when an overcurrent is detected fails.

[0113] In addition, the semiconductor DC circuit breaker 1 in this embodiment uses a terminal (described later) that is connected to the semiconductor switching element 21 and through which the main current flows. Figure 14 The first external terminal 31, serving as conductor 111 in Embodiment 1, has a fuse 25 formed on a portion therein, which melts when a fusing current flows through it. The portion X of conductor 111 with an unknown temperature is the portion where the fuse 25 is formed. Then, the voltage detection unit 14 measures the instantaneous voltage V of the terminal. Furthermore, the known temperatures of at least one portion of conductor 111 include the temperature of the substrate on which the semiconductor switching element 21 is mounted, i.e., the substrate temperature Ta, and the temperature of the portion of the terminal further outward than the fuse 25, i.e., the terminal temperature Tt.

[0114] The semiconductor switching element 21 is a bidirectional switch formed by connecting the reference potential terminal of the first switching element 21a and the reference potential terminal of the second switching element 21b. Thus, current can be interrupted regardless of its direction. Furthermore, a unidirectional semiconductor switching element 21 can be used when bidirectional interruption is not required.

[0115] exist Figure 9 The example shown is an example of using a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) as the first switching element 21a and the second switching element 21b, but it is not limited to this and other semiconductor switching elements such as IGBT (Insulated Gate Bipolar Transistor) can also be used.

[0116] When the semiconductor switching element 21 is a MOSFET, the reference potential terminal through which the main current flows is the source S, which is one of the main terminals. Furthermore, a diode 22, consisting of the MOSFET's built-in main diode, is connected in anti-parallel between the source S and the drain D, the other main terminal through which the main current flows. A control signal from the control unit 12 is input to the gate G to control the switching on and off. Alternatively, in the case of an IGBT, the source is replaced with the emitter, the drain with the collector, and an external diode can be used for diode 22.

[0117] The semiconductor DC circuit breaker 1 has a semiconductor module 2 with a built-in semiconductor switching element 21.

[0118] Figure 10 This is a perspective view of the semiconductor module in Example 2. Figure 11 This is a three-dimensional view of the interior of the semiconductor module in Example 2. Figure 12 as well as Figure 13 This is a top view of the interior of the semiconductor module in Embodiment 2. Figure 14 This is a top view of the first external terminal of the semiconductor module and the fuse in Embodiment 2. Additionally, in Figure 13 The diagram illustrates external terminals and auxiliary terminals, as well as the integrated wiring formed with them. Figure 12 Their illustrations are omitted.

[0119] Semiconductor module 2 has a semiconductor switching element 21, a housing 38 housing the semiconductor switching element 21, a first external terminal 31, and a second external terminal 32. The first external terminal 31 is connected to a first main terminal of the semiconductor switching element 21, and the second external terminal 32 is connected to a second main terminal of the semiconductor switching element 21. Figure 9 The example shown is an example where the first main terminal is the drain D of the first switching element 21a and the second main terminal is the drain D of the second switching element 21b.

[0120] Furthermore, in Embodiment 2, the fuse 25, which is connected in series with the semiconductor switching element 21, is also built into the housing 38 of the semiconductor module 2. Moreover, the built-in fuse 25 is formed from a portion of the wiring within the housing 38 and melts when a predetermined fusing current flows through it.

[0121] In Embodiment 2, as an example of the built-in fuse 25, such as Figure 14 As shown, the fuse 25 is formed by thinning a portion of the connection wiring 31a integrally formed with the first external terminal 31. Thus, as... Figure 9As shown, a fuse 25 can be provided between the semiconductor switching element 21 and the protected device 4. Furthermore, the method of forming the fuse 25 is not limited to this; for example, the fuse 25 can also be formed by thinning a portion of the connection wiring 31a integrally formed with the first external terminal 31, or by using a material with a lower melting point than other portions.

[0122] As in Example 1 Figure 2 Correspondingly, the first external terminal 31 and the connecting wiring 31a integrally formed therewith, and the overcurrent measurement auxiliary terminal 37 (described later) directly connected to the first external terminal 31 are connected. Figure 11 (etc.) are collectively referred to as a terminal, which corresponds to conductor 111. Additionally, the portion where the fuse 25 is formed corresponds to the portion X in conductor 111 where the temperature is unknown. Figure 14 In the middle, the connection wire 31a, which is located above the fuse 25, corresponds to the first part 111A and is connected to the substrate on which the semiconductor switching element 21 is mounted. The temperature of this substrate corresponds to the substrate temperature Ta. Figure 14 In the middle, the connecting wiring 31a, the first external terminal 31, and the auxiliary terminal 37 for overcurrent measurement, which are located below the fuse 25, correspond to the second part 111B. The portion of this terminal that is further outward than the fuse 25 is... Figure 14 The temperature of the connection wiring 31a, the first external terminal 31, or the overcurrent measuring auxiliary terminal 37 located lower than the fuse 25 corresponds to the terminal temperature Tt. Furthermore, the thermal equivalent circuit Tmodel of this terminal is calculated in advance and stored in the thermal equivalent circuit storage unit 106. Additionally, the first drain sensing auxiliary terminal 35 (described later) is used in the voltage measurement performed by the voltage detection unit 14. Figure 11 Therefore, the first drain sensing auxiliary terminal 35 can also be included in the conductor 111 to construct the thermal equivalent circuit Tmodel. However, since no main current flows through the first drain sensing auxiliary terminal 35, there is almost no effect of temperature rise. Therefore, in order to simplify the calculation, the first drain sensing auxiliary terminal 35 can also be excluded from the conductor 111 to construct the thermal equivalent circuit Tmodel.

[0123] Furthermore, the housing 38 of the semiconductor module 2 is sealed with a gel, such as silicone gel (not shown), and the fuse 25 is also sealed with gel. As a result, the insulation withstand voltage of the fuse 25 is improved, and it can be miniaturized.

[0124] In addition, fuse 25 has parasitic resistance and parasitic inductance. The wiring of semiconductor module 2 also has parasitic resistance and parasitic inductance. Figure 9 The parasitic resistance 23 shown includes the parasitic resistance of the wiring and the parasitic resistance of the fuse 25, and the parasitic inductance 24 includes the parasitic inductance of the wiring and the parasitic inductance of the fuse 25.

[0125] Therefore, the voltage detection unit 14 in Embodiment 2 is configured to also utilize the parasitic resistance or parasitic inductance of the fuse 25 to detect the voltage generated across the parasitic resistance or parasitic inductance of the fuse 25, and the overcurrent is detected by the overcurrent detection device 11 based on this voltage.

[0126] Therefore, the semiconductor module 2 is configured such that, as an external terminal connected to the outside of the housing 38, it has a measuring terminal capable of measuring the voltage including the voltage generated across the parasitic resistance or parasitic inductance of the fuse 25. In embodiment 2, as the measuring terminal, a [missing information - likely a specific type of terminal] can be used. Figure 11 The auxiliary terminal 37 for overcurrent measurement and the first drain sensing auxiliary terminal 35 are shown.

[0127] Auxiliary terminal 37 for overcurrent measurement is with Figure 9 The terminal connected to the right side of the voltage detection unit 14, in Figure 11 In this embodiment, the auxiliary terminal 37 for overcurrent measurement is directly connected to the first external terminal 31. Furthermore, the auxiliary terminal 37 for overcurrent measurement is not limited to this; it can also be directly connected to the connecting wiring 31a as long as it is located closer to the first external terminal 31 than the fuse 25. In Embodiment 2, an example is shown where the auxiliary terminal 37 for overcurrent measurement is provided only on one of the two first external terminals 31, but it can also be provided on the other first external terminal 31, or on both first external terminals 31. Alternatively, only one first external terminal 31 may be provided.

[0128] The first drain sensing auxiliary terminal 35 is related to Figure 9 The terminal connected to the left side of the voltage detection unit 14 is... Figure 13 The first drain sensing pad 45 is connected. This allows measurement of the potential of the drain D of the first switching element 21a. Furthermore, in Embodiment 2, two first drain sensing auxiliary terminals 35 are provided, but only one may be provided. Additionally, the first drain sensing auxiliary terminal 35 is larger than the other auxiliary terminals, becoming an external terminal with a shape similar to the first external terminal 31. This allows the use of components from the AC terminals of semiconductor modules used in power conversion devices, etc. Furthermore, the first drain sensing auxiliary terminal 35 is not limited to this; it may also be made with the same small shape as the other auxiliary terminals.

[0129] like Figures 11 to 13 As shown, the semiconductor module 2 of Embodiment 2 has six insulating substrates 47 on a base plate 39. A wiring layer 48 is formed on the insulating substrates 47, a portion of which functions as solder pads. Sometimes the insulating substrates 47 and the wiring layer 48 are collectively referred to as substrates.

[0130] like Figure 12As shown, the two larger of the three insulating substrates 47 on the upper side are each equipped with a plurality of first switching elements 21a and are connected by bonding materials such as solder and bonding wires 49. The remaining substrate is an auxiliary substrate having a gate pad 43 connected to the gate G of the first switching element 21a and a source sensing pad 44 connected to the source sensing of the first switching element 21a.

[0131] Similarly, the two larger of the three insulating substrates 47 on the lower side are each equipped with a plurality of second switching elements 21b. The remaining substrate is an auxiliary substrate having a gate pad 43 connected to the gate G of the second switching element 21b and a source sensing pad 44 connected to the source sensing of the second switching element 21b.

[0132] Here, multiple first switching elements 21a and second switching elements 21b are used to ensure current capacity, and are configured as two parallel connections between the left and right insulating substrates 47. However, this is not a limitation; a configuration of three or more parallel connections is also possible, or a single path can be used without distinguishing between the left and right sides. Alternatively, the gate pad 43 and source sensing pad 44 can be provided on the insulating substrate 47 on which the first switching elements 21a and second switching elements 21b are mounted without using an auxiliary substrate. Furthermore, the first switching elements 21a and second switching elements 21b can be mounted on a single insulating substrate 47 without distinguishing between the upper and lower sides. In other words, the number of insulating substrates 47 is arbitrary.

[0133] like Figure 11 as well as Figure 13 As shown, the semiconductor module 2 has a first external terminal 31, a second external terminal 32, a gate auxiliary terminal 33, a source sensing auxiliary terminal 34, a first drain sensing auxiliary terminal 35, a second drain sensing auxiliary terminal 36, and an overcurrent measurement auxiliary terminal 37 as external terminals.

[0134] The first external terminal 31 is connected to the first drain pad 41 and to the drain D of the first switching element 21a, through which the main current flows. The second external terminal 32 is connected to the second drain pad 42 and to the drain D of the second switching element 21b, through which the main current flows.

[0135] The gate auxiliary terminal 33 on the right side is connected to the gate pad 43 on the upper side and to the gate G of the first switching element 21a. The gate auxiliary terminal 33 on the left side is connected to the gate pad 43 on the lower side and to the gate G of the second switching element 21b.

[0136] The source sensing auxiliary terminal 34 on the right is connected to the upper source sensing pad 44, and is connected to the source sensing of the first switching element 21a. The source sensing auxiliary terminal 34 on the left is connected to the lower source sensing pad 44, and is connected to the source sensing of the second switching element 21b.

[0137] The gate auxiliary terminal 33 and the source sensing auxiliary terminal 34 are connected to the control unit 12, and the semiconductor switching element 21 is driven by the control signal from the control unit 12.

[0138] The first drain sensing auxiliary terminal 35 and the overcurrent measurement auxiliary terminal 37 have already been described, so their descriptions are omitted.

[0139] The second drain sensing auxiliary terminal 36 is connected to the second drain sensing pad 46. This allows for the measurement of the potential of the drain D of the second switching element 21b. Furthermore, while only one second drain sensing auxiliary terminal 36 is provided in Embodiment 2, two or more may also be provided.

[0140] Next, the clamping circuit of Embodiment 2 will be described.

[0141] like Figure 9 As shown, in Embodiment 2, fuses 25 are connected in series. Fuse 25 requires a high current density to melt when a specified fusing current flows, thus its inductance is large. If the inductance increases due to the series connection of fuses 25, the surge voltage increases when the semiconductor switching element 21 is switched off; therefore, the semiconductor switching element 21 requires a high-voltage withstand capability. However, increasing the voltage withstand capability of the semiconductor switching element 21 leads to an increase in its on-resistance, resulting in increased losses.

[0142] Therefore, in Embodiment 2, a clamping circuit is configured to suppress surge voltage. By providing a clamping circuit that includes a semiconductor switching element 21 within the path but does not include a fuse 25 within the path, the influence of the inductance of the fuse 25 can be suppressed.

[0143] In Example 2, an example with two clamping circuits is shown.

[0144] The first clamping circuit is a clamping circuit consisting of a first switching element 21a, a Zener diode 26 connected between the gate G and drain D of the first switching element 21a, and a path of the control unit 12. When an overcurrent is detected and the control unit 12 releases charge from the gate of the first switching element 21a to cut off the current flowing through the first switching element 21a, a drain surge voltage is induced. When a voltage exceeding the avalanche voltage is applied to the Zener diode 26, the avalanche current is charged to the gate G of the first switching element 21a, thus slowing down the switching speed and gradually cutting off the current. Therefore, the maximum voltage between the source S and drain D can be limited, allowing the use of a low-voltage semiconductor switching element 21.

[0145] The Zener diode 26 connected to the first switching element 21a can be connected between the gate auxiliary terminal 33 and the first drain sensing auxiliary terminal 35 of the first switching element 21a. Furthermore, the smaller the parasitic inductance, the better; therefore, a drain sensing auxiliary terminal composed of terminals smaller than the first drain sensing auxiliary terminal 35 can also be provided and connected to them.

[0146] In addition, such as Figure 9 As shown, similarly, on the side of the second switching element 21b, a clamping circuit including the second switching element 21b is provided within the path by also providing a Zener diode 26 between the gate G and the drain D of the second switching element 21b. The Zener diode 26 connected to the second switching element 21b can be connected between the gate auxiliary terminal 33 and the second drain sensing auxiliary terminal 36 of the second switching element 21b. Alternatively, it can be connected to the second external terminal 32 instead of the second drain sensing auxiliary terminal 36, but since a smaller parasitic inductance is better, the second drain sensing auxiliary terminal 36 is preferred.

[0147] Since the fuse 25 is not included in the path of these first clamping circuits, it becomes a structure that is unaffected even if the inductance increases due to the series connection of the fuse 25.

[0148] The second clamping circuit is a clamping circuit consisting of a path containing a semiconductor switching element 21 and a variable resistor 13 connected to both ends of the semiconductor switching element 21. Additionally, in Figure 9 The inductor shown next to the variable resistor 13 is the parasitic inductance of the clamping circuit. The variable resistor 13 can be, for example, a metal oxide variable resistor (MOV). When a voltage above a specified value is applied, the variable resistor 13 experiences avalanche voltage, causing its resistance to drop and current to bypass to the variable resistor 13 side, thus allowing the use of a low-voltage semiconductor switching element 21. Furthermore, since the first clamping circuit applies a thermal load to the semiconductor switching element 21 when it operates, the second clamping circuit also has the effect of mitigating the thermal load.

[0149] One side of the variable resistor 13 is connected to the first drain sensing auxiliary terminal 35, and the other side is connected to either the second drain sensing auxiliary terminal 36 or the second external terminal 32. The second external terminal 32 has a larger current capacity than the second drain sensing auxiliary terminal 36, therefore it is preferable to connect to the second external terminal 32. Similarly, it is preferable that the first drain sensing auxiliary terminal 35 has a larger current capacity than the other auxiliary terminals.

[0150] Since the path of the second clamping circuit does not include the fuse 25, it becomes a structure that is unaffected even if the inductance increases due to the series connection of the fuse 25.

[0151] In addition, Figure 9 In this configuration, the Zener diode 26 and the variable resistor 13 are disposed outside the semiconductor module 2, but at least one of them may also be built into the semiconductor module 2. A portion or all of the voltage detection unit 14, temperature detection unit 15, overcurrent detection device 11, and control unit 12 may be included in the semiconductor module 2.

[0152] As explained above, according to Embodiment 2, in addition to the effects of Embodiment 1, it is also possible to realize a semiconductor DC circuit breaker 1 with redundancy that can interrupt current even if the semiconductor switching element 21 used to interrupt current when an overcurrent is detected fails, and a semiconductor module 2 suitable for use in the semiconductor DC circuit breaker 1.

[0153] Example 3

[0154] Example 3 is a variation of Example 2. The implementation method of the fuse 25 in Example 3 is different from that in Example 2. Otherwise, it is the same as Example 2, so the description will focus on the differences and repeated descriptions will be omitted.

[0155] Figure 15 This is a circuit diagram of the semiconductor DC circuit breaker and semiconductor module in Example 3. Figure 16 This is a three-dimensional view of the interior of the semiconductor module in Example 3. Figure 17 This is a top view of the interior of the semiconductor module in Example 3. Figure 15 Corresponding to Figure 9 , Figure 16 Corresponding to Figure 11 , Figure 17 Corresponding to Figure 12 .

[0156] In the semiconductor DC circuit breaker 1 and semiconductor module 2 of Embodiment 3, the fuse 25 is formed between the reference potential terminal (source S) of the first switching element 21a and the reference potential terminal (source S) of the second switching element 21b. Furthermore, in this case, the current path is also in series, therefore it can be interpreted that the fuse 25 and the semiconductor switching element 21 are connected in series.

[0157] In Embodiment 3, the built-in fuse 25 is formed from a portion of the wiring within the housing 38, and it melts when a predetermined fusing current flows through it, which is the same as in Embodiment 2, but... Figure 17 As shown, the bonding line 49 connecting the insulating substrate 47 with the first switching element 21a and the insulating substrate 47 with the second switching element 21b is... Figure 12 The amount of material is small, thus functioning as fuse 25. Therefore, it has the advantage of being easy to implement compared to Example 2. The fuse 25 of Example 3 can also be sealed with gel.

[0158] However, in Embodiment 3, in the portion where the fuse 25 is not formed, the terminal connected to the semiconductor switching element 21 and through which the main current flows is connected to the semiconductor switching element 21 is connected to the conductor 111 of Embodiment 1, and the voltage is measured by the voltage detection unit 14. Since the parasitic resistance 23 and parasitic inductance 24 do not include the parasitic resistance and inductance of the fuse 25, Embodiment 2 has higher sensitivity for detecting overcurrent. Furthermore, the fact that the fuse 25 is not included in the path of the first clamping circuit is the same as in Embodiment 2, thus achieving the same effect. However, the second clamping circuit includes the fuse 25 in its path, therefore, the second clamping circuit is affected by the increased inductance due to the series connection of the fuse 25, unlike Embodiment 2.

[0159] Corresponding to Embodiment 1, and similarly to Embodiment 2, the first external terminal 31, the connecting wiring 31a integrally formed therewith, and the overcurrent measurement auxiliary terminal 37 directly connected to the first external terminal 31 (see...) are also included. Figure 16 These are collectively referred to as a terminal, which corresponds to conductor 111. However, no fuse 25 is formed at this terminal. However, due to the complex shape of this terminal, there is a portion that becomes hotter than the measurable terminal temperature Tt due to the flow of the main current. Therefore, this hot portion is designated as the unknown temperature location X in conductor 111, and the thermal equivalent circuit Tmodel of this terminal is constructed.

[0160] Example 4

[0161] Example 4 is a variation of Example 3. In Example 4, the location where the voltage is measured by the voltage detection unit 14 and the location where the temperature is measured by the temperature detection unit 15 are different from those in Example 3. Otherwise, it is the same as Example 3, so the description will focus on the differences and repeated descriptions will be omitted.

[0162] Figure 18 This is a circuit diagram of the semiconductor DC circuit breaker and semiconductor module of Example 4. Figure 18 Is with Figure 15 The corresponding diagram.

[0163] In this embodiment, the semiconductor DC circuit breaker 1 uses two source sensing auxiliary terminals 34 to measure the voltage at the location where the fuse 25 is formed, that is, the voltage between the source S of the first switching element 21a and the source S of the second switching element 21b, through the voltage detection unit 14.

[0164] Corresponding to Embodiment 1, conductor 111 corresponds to fuse 25 formed by a portion of the wiring connected to semiconductor switching element 21. The portion X in conductor 111 with an unknown temperature is set at a location within fuse 25, such as the intermediate point where the wiring constituting fuse 25 is furthest from the substrate. Since no main current flows through the source sensing auxiliary terminal 34, for the sake of simplified calculation, the source sensing auxiliary terminal 34 may not be included in conductor 111. Furthermore, the known temperature of at least one portion of conductor 111 can be replaced by... Figure 2 The terminal temperature Tt can be determined by using two substrate temperatures Ta.

[0165] According to this embodiment, the current flowing through the fuse 25 can be estimated with higher accuracy than in Embodiment 3.

[0166] Example 5

[0167] Example 5 is a variation of Examples 2 and 3. Example 5 differs from Examples 2 and 3 in that the fuse 25 is located outside the semiconductor module 2. Otherwise, it is the same as Examples 2 and 3, and therefore the description will focus on the differences, omitting repeated descriptions.

[0168] Figure 19 This is a circuit diagram of the semiconductor DC circuit breaker and semiconductor module of Example 5. Figure 19 Is with Figure 9 The corresponding diagram.

[0169] In Embodiment 5, the fuse 25 of the semiconductor DC circuit breaker 1 and the semiconductor module 2 is disposed outside the semiconductor module 2. Therefore, a general fuse 25 can be used.

[0170] As a counterpart to Example 1, it is the same as Example 3.

[0171] Example 6

[0172] Example 6 is a variation of Example 5. The detection methods of the voltage detection unit 14 and temperature detection unit 15 in Example 5 are different from those in Example 5. Apart from this, it is the same as Example 5, so the description will focus on the differences and repeated descriptions will be omitted.

[0173] Figure 20 This is a circuit diagram of the semiconductor DC circuit breaker and semiconductor module of Example 6. Figure 20 Is with Figure 19 The corresponding diagram.

[0174] In Embodiment 6, the semiconductor DC circuit breaker 1 and semiconductor module 2 are similar to those in Embodiment 5, with the fuse 25 disposed outside the semiconductor module 2. Therefore, a general-purpose fuse 25 can be used.

[0175] Furthermore, the voltage detection unit 14 detects the voltage generated across the parasitic resistance or parasitic inductance of the fuse 25, and detects the overcurrent through the overcurrent detection device 11 based on this voltage.

[0176] Corresponding to Embodiment 1, the fuse 25 corresponds to the conductor 111. The part X in the conductor 111 where the temperature is unknown is set to a part of the fuse 25, such as the part with the highest temperature. In addition, as the known temperature of at least one part of the conductor 111, the temperature can be measured by the temperature detection unit 15 to measure the temperature of the part that can measure the temperature of the fuse 25 or its surroundings.

[0177] Example 7

[0178] Example 7 is a variation of Example 5. Example 7 differs from Example 5 in that the fuse 25 is not provided. Otherwise, it is the same as Example 5, so the description will focus on the differences and repeated descriptions will be omitted.

[0179] Figure 21 This is a circuit diagram of the semiconductor DC circuit breaker and semiconductor module of Example 7. Figure 21 Is with Figure 19 The corresponding diagram.

[0180] This embodiment is an example of applying the overcurrent detection device 11 of Embodiment 1 to a general semiconductor DC circuit breaker 1 without a fuse 25.

[0181] As a counterpart to Example 1, it is the same as Example 5.

[0182] Example 8

[0183] Example 8 is an example of a power conversion device 200 using the overcurrent detection device 11 of Example 1.

[0184] Figure 22 This is a functional block diagram of the power conversion device in Example 8.

[0185] The power conversion device 200 of Embodiment 8 includes the overcurrent detection device 11 of Embodiment 1, the power conversion circuit 201 composed of semiconductor switching elements, and the protection circuit 202 that controls the semiconductor switching elements to protect them when the overcurrent determination unit 102 of the overcurrent detection device 11 determines that there is an overcurrent.

[0186] As in Embodiment 1, the semiconductor switching element connected to the power conversion circuit 201 is connected, and the terminal of the semiconductor switching element through which the main current flows corresponds to the conductor 111.

[0187] The power conversion circuit 201 and the protection circuit 202 can use generally known structures.

[0188] The semiconductor module used in the power conversion circuit 201 is equivalent to that in Example 7. Figure 21 The second switching element 21b is oriented in the same direction as the first switching element 21a in the semiconductor module. In addition, an AC terminal is led out from the connection node between the source S of the first switching element 21a and the drain D of the second switching element 21b as an external terminal.

[0189] The detection methods for voltage detection unit 14 and temperature detection unit 15 are the same as in Example 7.

[0190] The embodiments of the present invention have been described above, but the present invention is not limited to the structures described in the embodiments, and various changes can be made within the scope of the technical concept of the present invention. In addition, some or all of the structures described in each embodiment can also be combined and applied.

[0191] Furthermore, the overcurrent detection device 11 and overcurrent detection method of Embodiment 1 are not limited to the semiconductor DC circuit breaker 1 and the power conversion device 200, but can also be applied to other devices.

[0192] Symbol Explanation

[0193] 1: Semiconductor DC circuit breaker; 2: Semiconductor module; 3: Power supply; 4: Protected equipment; 11: Overcurrent detection device; 12: Control unit; 13: Variable resistor; 14: Voltage detection unit; 15: Temperature detection unit; 21: Semiconductor switching element; 21a: First switching element; 21b: Second switching element; 22: Diode; 23: Parasitic resistance; 24: Parasitic inductance; 25: Fuse; 26: Zener diode; 31: First external terminal; 31a: Connection Wiring connection; 32: Second external terminal; 33: Gate auxiliary terminal; 34: Source sensing auxiliary terminal; 35: First drain sensing auxiliary terminal; 36: Second drain sensing auxiliary terminal; 37: Auxiliary terminal for overcurrent measurement; 38: Housing; 39: Base plate; 41: First drain pad; 42: Second drain pad; 43: Gate pad; 44: Source sensing pad; 45: First drain sensing pad; 46: Second drain sensing pad; 47: Insulating substrate; 48: Wiring connection. Layer, 49: Bonding line, 101: Instantaneous current estimation unit, 102: Overcurrent judgment unit, 103: Power consumption calculation unit, 104: Temperature estimation unit, 105: Resistance estimation unit, 106: Thermal equivalent circuit storage unit, 107: Overcurrent detection signal, 111: Conductor, 111A: First part, 111B: Second part, 111B1: Third part, 111B2: Fourth part, 112: Heat dissipation direction, 121: RC not considered, 122: R considered 123: Considering RC, 200: Power conversion device, 201: Power conversion circuit, 202: Protection circuit, G: Gate, S: Source, D: Drain, V: Instantaneous voltage, X: Location with unknown temperature, R: Estimated resistance, I: Estimated instantaneous current, P: Power consumption, Tmodel: Thermal equivalent circuit, Rth: Thermal resistance, Cth: Thermal capacity, T: Temperature, Ta: Substrate temperature, Tt: Terminal temperature, ILIM: Threshold, τ: Thermal time constant, t: Time.

Claims

1. An overcurrent detection device, characterized by comprising: have: The instantaneous current estimation unit estimates the estimated instantaneous current I of the unknown temperature part X in the conductor based on the instantaneous voltage V measured at a specified measurement location in the conductor and the estimated resistance R of the unknown temperature part X in the conductor. The overcurrent determination unit determines whether an overcurrent is present based on the estimated instantaneous current I. The power consumption calculation unit calculates the power consumption P based on the instantaneous voltage V and the estimated instantaneous current I; The temperature estimation unit estimates and updates the temperature T of an unknown temperature portion X in the conductor based on a thermal equivalent circuit that takes into account at least the thermal resistance and thermal capacity of the conductor, the power consumption P, and the known temperature of at least one part of the conductor. as well as The resistance estimation unit updates the estimated resistance R of the unknown temperature portion X in the conductor based on the temperature T updated by the temperature estimation unit.

2. The overcurrent detection device according to claim 1, characterized in that, The temperature estimation unit estimates the temperature T by making the initial value of the temperature T equal to the initial value of the known temperature of at least one part of the conductor.

3. A semiconductor DC circuit breaker, characterized by have: The overcurrent detection device according to claim 1; Semiconductor switching elements; and The control unit controls the semiconductor switching element to cut off the main current flowing through the semiconductor switching element when the overcurrent determination unit determines that it is an overcurrent.

4. The semiconductor DC circuit breaker according to claim 3, characterized in that have: A fuse, which is connected in series with the semiconductor switching element, The overcurrent determination unit determines that an overcurrent occurs when the estimated instantaneous current I is above a predetermined threshold smaller than the fuse's fusing current.

5. The semiconductor DC circuit breaker according to claim 4, characterized in that, The conductor is a terminal connected to the semiconductor switching element and through which the main current flows. The terminal is partially formed with a fuse that melts when the fusible current flows. The part X in the conductor where the temperature is unknown is the part where the fuse is formed.

6. The semiconductor DC circuit breaker according to claim 5, characterized in that, The known temperature of at least one portion of the conductor includes the temperature of the substrate on which the semiconductor switching element is mounted and the temperature of the portion of the terminal that is further outward than the fuse.

7. The semiconductor DC circuit breaker according to claim 4, characterized in that, The conductor is the fuse. The fuse is formed from a portion of the wiring connected to the semiconductor switching element. The part X in the conductor with an unknown temperature is a part of the fuse.

8. The semiconductor DC circuit breaker according to claim 7, characterized in that, The known temperature of at least one portion of the conductor includes the temperature of the substrate on which the semiconductor switching element is mounted.

9. The semiconductor DC circuit breaker according to claim 4, characterized in that, The conductor is a terminal connected to the semiconductor switching element and through which the main current flows.

10. The semiconductor DC circuit breaker according to claim 3, characterized in that, The conductor is a terminal connected to the semiconductor switching element and through which the main current flows.

11. A power conversion device, characterized in that, have: The overcurrent detection device according to claim 1; Power conversion circuits, which are constructed using semiconductor switching elements; and A protection circuit that controls the semiconductor switching element to protect it when the overcurrent determination unit determines that an overcurrent has occurred.

12. The power conversion device according to claim 11, characterized in that, The conductor is a terminal connected to the semiconductor switching element and through which the main current of the semiconductor switching element flows.

13. An overcurrent detection method, characterized in that, have: The instantaneous current estimation step estimates the estimated instantaneous current I of the unknown temperature part X in the conductor based on the instantaneous voltage V measured at a specified measurement location in the conductor and the estimated resistance R of the unknown temperature part X in the conductor. The overcurrent determination step determines whether it is an overcurrent based on the estimated instantaneous current I. The power consumption calculation step calculates the power consumption P based on the instantaneous voltage V and the estimated instantaneous current I; The temperature estimation step estimates and updates the temperature T of an unknown temperature location X in the conductor based on a thermal equivalent circuit that takes into account at least the thermal resistance and thermal capacity of the conductor, the power consumption P, and the known temperature of at least one location of the conductor. as well as The resistance estimation step updates the estimated resistance R of the unknown temperature portion X in the conductor based on the temperature T updated in the temperature estimation step.

14. The overcurrent detection method according to claim 13, characterized in that, In the temperature estimation step, the initial value of the temperature T is estimated by assuming that it is equal to the initial value of the known temperature of at least one part of the conductor.

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