Method for monitoring the degradation status of electrical interconnects in a power module assembly

Abstract

A method for monitoring the degradation state of an electrical interconnect (15) in a power module assembly (100) includes acquiring a detection signal that is sensitive to a reverse recovery current generated from a diode (14) in the power module assembly. The reverse recovery current is generated by the turn-on switching operation of a switch (11) in a test half-bridge branch (1) comprising a diode, a switch, and an interconnect. The method of the present invention may be optionally combined with another monitoring method based on the turn-off switching operation of a switch to monitor the degradation state of another electrical interconnect in the same half-bridge branch. Thus, it becomes possible to monitor the entire interconnect of the half-bridge branch.

Description

[Technical Field]

[0001] The present invention relates to a method for monitoring the degradation state of electrical interconnects in a power module assembly. The present invention also relates to a power module assembly suitable for carrying out such a method. Priority is claimed in European Patent Application Publication No. 23306810.5, filed on 16 October 2023, the contents of which are incorporated herein by reference. [Background technology]

[0002] Power module assemblies are used in many applications, such as power converters and power sources for motors, including traction motors, particularly those for electric vehicles. They operate by switching between high current and high voltage according to a time-controlled sequence. Most of these power module assemblies comprise multiple half-bridge branches connected in parallel to each other between a first supply terminal and a second supply terminal. This allows for the supply of high or very high current to a load connected to the output of the power module assembly. In such a configuration, each half-bridge branch comprises at least a first switch, a first electrical interconnect, a midpoint terminal, a first diode, and a second electrical interconnect, all connected in series, with the midpoint terminal located between the first switch and the first electrical interconnect on one side, and between the first diode and the second electrical interconnect on the other. Such half-bridge branches are typically supplied as separate, integrated electrical elements commonly known as modules. The midpoint terminals of all half-bridge branches are connected to the load supply terminals of the power module assembly.

[0003] In addition, within each half-bridge branch, the connection direction of the first diode is such that when the first switch of that half-bridge branch is turned on, the first diode of the same half-bridge branch transitions from a conductive state to a disconnected state.

[0004] In reality, each switch or diode is, in most cases, a separate semiconductor die, electrically connected to other electrical components via interconnects that can be bond wires, solder, sintered layers, copper wiring, etc. However, the aging degradation of these interconnects, particularly due to thermal or mechanical stress, is a problem for the lifespan of the power module assembly. Therefore, it is important to detect the degradation status of such interconnects in order to request maintenance of the power module assembly at the appropriate time, including the replacement of half-bridge branches with degraded interconnects.

[0005] Furthermore, it is known that the presence of a diode that transitions from a conductive state to an interrupted state causes a transient current called a reverse recovery current to flow through the branch containing the diode. This reverse recovery current flows from the cathode to the anode of the diode, causing the diode junction to reverse polarization, which in turn leads to the diode being interrupted. [Overview of the project] [Problems that the invention aims to solve]

[0006] Starting from this situation, one object of the present invention is to enable the detection of degraded interconnects within a power module assembly while the power module assembly is in use.

[0007] Another object of the present invention is to enable such detection without removing the power module assembly for testing purposes.

[0008] Another object of the present invention is to provide a diagnosis of the degradation state of the electrical interconnects inside the power module assembly, advantageously in real time during its useful operation. [Means for solving the problem]

[0009] To meet at least one of these objectives or other objectives, a first aspect of the present invention proposes a new method for monitoring the degradation state of electrical interconnections in a power module assembly having the above configuration. Within each half-bridge branch, the connection direction of the first diode is such that when the first switch of this half-bridge branch is turned on, the reverse recovery current generated by the first diode transitioning from a conducting state to a blocking state flows through the second electrical interconnection and at least partially through the first electrical interconnection.

[0010] According to the present invention, the method includes connecting at least one sensor to the power module assembly, whereby at least one detection signal delivered by the at least one sensor is sensitive to the time variation of the current flowing through a first electrical interconnection of one of the half-bridge branches of the power module assembly called the test target branch. And the method includes the following first step sequence: - Acquiring the detection signal that appears after the turn-on of the first switch of the test target branch; - Estimating information regarding the degradation state of the second electrical interconnection of the test target branch based on the characteristics of the acquired detection signal and further includes.

[0011] Therefore, the method of the present invention uses the reverse recovery current generated after the turn-on of the first switch to reveal changes in the state of the second electrical interconnection through signal detection at the first electrical connection.

[0012] Preferably, the sensor may be permanently included within the power module assembly, whereby the monitoring method can be continuously or repeatedly implemented during the useful operation of the power module assembly. Alternatively, the sensor may be connected to the power module assembly only during test times, such as during maintenance including the method of the present invention.

[0013] Generally, with respect to the present invention, the first switch related to the turn-on switching operation for implementing the method of the present invention, and the first electrical interconnection related to the connection of the sensor may be an upper switch close to the first supply terminal and the second supply terminal having the highest potential value. However, alternatively, it may be a lower switch close to both supply terminals having the lowest potential value.

[0014] When the second electrical interconnection of the test target branch is composed of a plurality of wires connected in parallel to each other, the information regarding the deterioration state may include the number of damaged wires among the wires of the second electrical interconnection of the test target branch. In such a case, by repeatedly executing the method of the present invention, a diagnosis regarding progressive deterioration is provided before the operation of the power module assembly is hindered by the disconnection of all the wires of the second electrical interconnection.

[0015] Here also generally, with respect to the present invention, the characteristics of the detection signal used to estimate the deterioration state of the second electrical interconnection of the test target branch are - whether at least one peak value of the detection signal is higher than a threshold value in absolute value, - the sign of a part of the detection signal, and - the difference in shape between two detection signals obtained during the execution of each of the first step sequences respectively related to the same one of the half-bridge branches of the power module assembly used as the test target branch, may include at least one of the above.

[0016] In a first embodiment of the method of the present invention, at least one sensor may include two voltage sensors respectively connected in parallel to one of the first electrical interconnections of one of the half-bridge branches of the power module assembly, which is different from the half-bridge branch of the other voltage sensor. Such a first embodiment provides better separation between the characteristics of the detection signals related to each second electrical interconnection.

[0017] In a second embodiment of the method of the present invention, the first node is located between a first switch and a first electrical interconnect in each of at least two half-bridge branches of the power module assembly. At least one sensor may be a voltage sensor connected between the first nodes of each of these two half-bridge branches. According to such a second embodiment, it is possible to reduce the number of sensors required to monitor all second electrical interconnects included in the power module assembly.

[0018] The first step sequence of the method of the present invention may be advantageously combined with a dedicated second step sequence for monitoring the degradation state of the first electrical interconnect of the branch under test, using the same sensor for the first and second step sequences. Thus, advantageously, both the same one first and second electrical interconnect of the half-bridge branch can be monitored during useful operation of the power module assembly. For this purpose, the method includes the following second step sequence: - Using at least one sensor, acquire another detection signal that appears after the first switch of the branch under test is turned off, - Based on the characteristics of this other detection signal obtained, information regarding the degradation state of the first electrical interconnect of the branch under test is estimated. It may also include the following.

[0019] According to possible configurations of power module assemblies that may be preferable for common-mode rejection requirements, the second supply terminal is a reference terminal or a ground terminal, and the following features may be further implemented: -The first switch and first electrical interconnect of the branch under test may be connected in series between the midpoint terminal and the second supply terminal of the branch under test. - The first electrical interconnect is connected between the first switch and the second supply terminal in the branch under test, and - At least one sensor comprises a voltage sensor connected in parallel with the first electrical interconnect.

[0020] In general, the method of the present invention may be implemented in a configuration of a power module assembly suitable for supplying positive and negative currents to a load. In such a case, each half-bridge branch of the power module assembly may further comprise a second switch connected in parallel with a first diode of the half-bridge branch, and each second diode connected in parallel with the first switch of the same half-bridge branch. Each half-bridge branch may be configured such that, during operation of the power module assembly, its first and second switches are simultaneously turned on and off in opposite directions. Furthermore, the direction of conduction of each of the first and second switches and the direction of conduction of the corresponding first or second diode connected in parallel are opposite, respectively.

[0021] In such a configuration of the power module assembly, the first step sequence may be performed twice with respect to the branch under test: once to estimate information about the degradation state of one of the first and second interconnects of the branch under test with respect to the load current flowing out of the power module assembly at the load supply terminal, and the other to estimate information about the degradation state of the other of the first and second interconnects of the branch under test with respect to the load current returning to the power module assembly at the load supply terminal.

[0022] In general, in the present invention, each first switch may be of the isolated grid bipolar transistor type or MOSFET type. If any, each second switch may also be of the isolated grid bipolar transistor type or MOSFET type.

[0023] A second aspect of the present invention proposes a power module assembly comprising at least two half-bridge branches connected in parallel to each other between a first supply terminal and a second supply terminal. In this power module assembly, -Each half-bridge branch comprises a first switch, a first electrical interconnect, a center terminal, a first diode, and a second electrical interconnect, with the center terminal located between the first switch and the first electrical interconnect on one side, and between the first diode and the second electrical interconnect on the other side. -All half-bridge branch midpoint terminals are connected to the load supply terminals of the power module assembly. - The connection direction of the first diode in each half-bridge branch is such that when the first switch of the half-bridge branch is turned on, the reverse recovery current generated from the first diode, which transitions from a conducting state to an interrupted state, flows through the second electrical interconnect and, at least partially, through the first electrical interconnect.

[0024] According to the present invention, the power module assembly is -Means for controlling the turn-on of one of the first switches of a half-bridge branch of a power module assembly called the branch to be tested, - After the first switch of the branch under test is turned on, at least one sensor is connected to deliver at least one detection signal that is sensitive to the time variation of the current flowing through the first electrical interconnect of the branch under test, - At least one signal processing unit connected to receive a detection signal from at least one sensor and configured to estimate information regarding the degradation state of a second electrical interconnect of the branch being tested based on the characteristics of the detection signal. To further prepare.

[0025] Such a power module assembly is suitable for implementing a monitoring method that satisfies an aspect of the first invention. Furthermore, the power module assembly may further have the optional additional features described above in relation to an aspect of the first invention. In particular, it may be suitable for supplying positive and negative currents to a load and may be even more suitable for implementing a second step sequence. [Brief explanation of the drawing]

[0026] [Figure 1] The minimum configuration of a power module assembly suitable for carrying out the method of the present invention is shown.

[0027] [Figure 2] This is a time diagram of the detection signals obtained when implementing the monitoring method of the present invention for a first possible sensor connection configuration.

[0028] [Figure 3] The second possible sensor connection configuration corresponds to Figure 2.

[0029] [Figure 4] Another power module assembly configuration similarly suitable for carrying out the method of the present invention is shown.

[0030] [Figure 5] Another power module assembly configuration similarly suitable for carrying out the method of the present invention is shown.

[0031] [Figure 6a] Figure 5 shows the connection configuration of the switches and parallel-connected diodes in the power module assembly. [Figure 6b] Figure 5 shows the connection configuration of the switches and parallel-connected diodes in the power module assembly. [Modes for carrying out the invention]

[0032] In these diagrams, the same reference number shown in different diagrams indicates the same element of the same function.

[0033] In Figure 1, reference numeral 100 indicates a power module assembly comprising multiple half-bridge branches connected in parallel between a positive supply terminal 101 and a negative supply terminal 102. For clarity, only two half-bridge branches are shown in the figure, but their number is arbitrary and may be up to, for example, 10. All half-bridge branches may be similar and each comprises the following components connected in series from supply terminal 101 to supply terminal 102 in the following order, as listed first for half-bridge branch 1. For example, a first switch 11 of the MOSFET type or IGBT type (IGBT stands for isolated grid bipolar transistor), First electrical interconnection section 12, midpoint terminal 13, The first diode 14, and Second electrical interconnection section 15. The same order of components is used for the half-bridge branch 2: the first switch 21, the first electrical interconnect 22, the center terminal 23, the first diode 24, and the second electrical interconnect 25.

[0034] The midpoint terminals 13, 23, ... are all connected to the load supply terminal 103 of the power module assembly 100, thereby adding up the load current contributions of each half-bridge branch 1, 2 ... and applying this to the load (not shown), which is hereafter referred to as the load current. 103 It can supply a higher output current, as indicated by the notation Z. In Figure 1, the reference numeral Z 1-2 This indicates the impedance of the interconnection between the midpoint terminals 13 and 23.

[0035] The switches 11, 21... and diodes 14, 24... may each be manufactured as separate dies, generally indicated as D, and the electrical interconnects 12, 22..., 15, 25... may each be manufactured as bundles of bond wires, for example, each bundle of 10 bond wires. When the first switches 11 and 21 are IGBTs, the terminals of each switch 11 or 21 connected to the first electrical interconnect 12 or 22 are generally known as Kelvin emitters. For switches 11 (21 respectively), they are denoted as Ke1 (Ke2 respectively). The Kelvin emitters Ke1 and Ke2 are referred to as the first nodes in the general parts of this specification. The midpoint terminals 13 and 23 are generally known as power emitters. The collectors of the IGBT switches 11 and 21 are connected to the positive supply terminal 101. The cathodes of the diodes 14 (each 24) are connected to the center terminals 13 (each 23), and the anodes of the diodes 14 (each 24) are connected to the second electrical interconnection parts 15 (each 25), thereby oriented in the opposite direction to the conduction direction of the switches 11 (each 21).

[0036] For the useful operation of the power module assembly 100, each half-bridge branch may be controlled such that switch 11 is controlled by a first control signal generator 10, switch 21 by a second control signal generator 20, and so on; however, alternatively, a single common control signal generator may be used to control all switches 11, 21... The control signal generator 10 forms means for controlling the turn-on of switch 11, as described in the general part of this specification. The assembly portion connected between supply terminal 101 and load supply terminal 103 is generally called the upper portion and is denoted as TS, and the other assembly portion connected between load supply terminal 103 and supply terminal 102 is generally called the lower portion and is denoted as BS. Such a structure of the power module assembly 100 is well known and is very commonly used in many power applications. Each half-bridge branch 1, 2... may be provided as a separate module, and it is a challenge to monitor the normal operation of each of these modules over the long service life of the power module assembly 100. The first challenge in this regard is to detect potential degradation in each of the second electrical interconnects 15, 25... The method of the present invention for addressing this first challenge is described here. An improvement of the present invention may also be to detect potential degradation in each of the first electrical interconnects 12, 22..., which will be described later.

[0037] According to the method of the present invention, the sensor is connected to be sensitive to the current flowing through the first electrical interconnect 12. Such a sensor is connected to a high-speed voltmeter V according to one of the following connection configurations. HS1 That's fine. - Between the Kelvin emitter Ke1 and the power emitter 13 shown in Figure 1, or - Between both Kelvin emitters Ke1 and Ke2, thus interconnected in series, the impedance Z 1-2 and in parallel with the interconnection section 22.

[0038] In both cases, the high-speed voltmeter V HS1The positive terminal of HS1 the voltage profile detected by the high-speed voltmeter V may be connected to the Kelvin emitter Ke1. And, during the operation of the power module assembly 100, the voltage profile detected by the high-speed voltmeter V is recorded from the turn-on of the switch 11 controlled by the control signal generator 10 to the end time of recording before the subsequent turn-off of the switch 11. Upon turn-on, a current contribution starts to flow from the supply terminal 101 to the load supply terminal 103. However, in a known method, the turn-on of the switch 11 immediately shifts the diode 14 from the conducting state to the blocking state, and such a shift generates a transient reverse recovery current through the diode 14. This reverse recovery current partially occurs from the upper part of the half-bridge branch 1, but also partially occurs from the upper part of the half-bridge branch 2. However, due to the impedance Z 1-2 between the power emitters 13 and 23, the reverse recovery current of the diode 14 mainly flows through the upper part of the half-bridge branch 1, that is, from the supply terminal 101 through the switch 11 and the first interconnecting portion 12. Therefore, the voltage detected by the high-speed voltmeter V HS1 connected to both ends of the first interconnecting portion 12 is sensitive to the reverse recovery current of the diode 14. It may be advantageous to time-filter this detection signal detected by the high-speed voltmeter V HS1 to separate the contribution of the reverse recovery current from the increase in the contribution of the half-bridge branch 1 to the load current I 103 . In fact, the reverse recovery current causes a voltage overshoot after the turn-on of the switch 11, which is superimposed on another voltage contribution due to the increase in the load current contribution. In some cases, the detection signal may be accumulated over multiple consecutive turn-on switching operations of the switch 11. Since the reverse recovery current of the diode 14 flows through the second interconnecting portion 15, the overshoot amplitude of the detection signal detected by the high-speed voltmeter V HS1 reflects the deterioration state of this second interconnecting portion 15. The high-speed voltmeter V, including optional accumulation, time window processing, peak detection, peak amplitude value measurement, threshold processing, code analysis, etc. HS1All signal processing and analysis steps applied to the detection signal output by may be performed by a signal processing unit 104 connected to receive the detection signal. The time diagram in Figure 2 shows several detected voltage profiles thus obtained, respectively, for the case where no bond wires are broken in the second interconnect 15 (curve labeled 0WB), for the case where two bond wires are broken in the second interconnect 15 (curve labeled 2WB), for the case where four bond wires are broken (curve labeled 4WB), and for the case where six bond wires are broken (curve labeled 6WB). In this figure, the x-axis represents the time value in microseconds (μs) denoted as t, and the y-axis represents V Ke1-13 This indicates the detected instantaneous voltage value in volts (V), denoted as V. The shape of the profile is determined by the resistance and inductance values ​​of the impedances of the electrical interconnects 12 and 15, respectively, as well as the operating temperatures of switches 11 and 21, while the amplitude of each profile reflects the number of broken wires present in the second electrical interconnect 15. A high-speed voltmeter V can be accumulated and filtered over multiple turn-on switching operations of switch 11. HS1 The detection signal provided may be processed through peak detection and peak amplitude measurement. The peak amplitude value may be compared to a pre-recorded value to determine the number of broken wires in the second interconnect 15. Alternatively, voltage profiles corresponding to different values ​​of the number of broken wires can be pre-recorded, and the detection signal detected for monitoring purposes is identified to one of the pre-recorded voltage profiles using a best-match algorithm. The pre-recorded voltage profiles may be a reference profile provided by the manufacturer of the power module assembly 100, or a voltage profile recorded during quality testing performed early in the life of the power module assembly 100, for example, immediately after manufacture when all interconnects are considered undamaged.

[0039] Figure 3 shows a high-speed voltmeter V HS1This is another time graph obtained when the voltmeter's positive terminal is connected to the Kelvin emitter Ke1, where it is instead connected between both Kelvin emitters Ke1 and Ke2. The x-axis has the same meaning as before, and the y-axis represents V Ke1-Ke2 This indicates the instantaneous voltage value detected between both Kelvin emitters Ke1 and Ke2. The voltage profile obtained in this alternative method differs from the one described above, but these also reflect the number of broken wires in the second electrical interconnect 15. A high-speed voltmeter V is used between both Kelvin emitters Ke1 and Ke2. HS1 By connecting this, in addition to monitoring the second electrical interconnect 15 of half-bridge branch 1, it also becomes possible to monitor the potential degradation of the bond wires constituting the second electrical interconnect 25 of half-bridge branch 2. The sign analysis performed on the main peak of the detected signal directly indicates whether the degradation is related to the interconnect 15 of half-bridge branch 1 or the interconnect 25 of half-bridge branch 2. The curve labels 0WB, 2WB, 4WB, and 6WB in Figure 3 have the same meaning as in Figure 2.

[0040] Clearly, the voltage profiles 0WB, 2WB, 4WB, and 6WB, as shown in Figures 2 and 3, change when some of the wires in each of the second electrical interconnects 15 and 25 break simultaneously. However, the resulting profiles can be pre-recorded for each combination of the number of broken wires associated with each of the second electrical interconnects of the power module assembly 100. The detected profiles obtained during the monitoring method are then compared with such pre-recorded profiles. However, in certain situations where both interconnects 15 and 25 are degraded to the same extent as the other, the detected profiles may not be affected.

[0041] Figure 4 shows an alternative configuration of the power module assembly 100, which may be advantageous when implementing the method of the present invention using a separate sensor dedicated to each half-bridge branch. In the power module assembly 100 of Figure 4, the components of the upper portion TS and the lower portion BS are swapped, and the supply terminal 102 is grounded. High-speed voltmeter V HS1 Here too, it is dedicated to half-bridge branch 1 and is still connected in parallel with the first electrical interconnect 12 between the Kelvin emitter Ke1 at the new position of the lower BS and the supply terminal 102. Similarly, the high-speed voltmeter V HS2 This is dedicated to half-bridge branch 2 and is connected between the Kelvin emitter Ke2 and supply terminal 102 of the lower BS. High-speed voltmeter V HS1 (V HS2 The positive terminal of the ) is connected to the Kelvin emitter Ke1 (Ke2 respectively), and the high-speed voltmeter V HS1 and V HS2 Each of its negative terminals is connected to the grounded supply terminal 102. This is connected to the high-speed voltmeter V HS1 and V HS2 It has the advantage of simplifying the design. The monitoring operation according to the present invention is the same as described above, and the high-speed voltmeter V HS1 (V HS2 The detection signal detected by the high-speed voltmeter V primarily reflects any potential degradation present in the electrical interconnects 15 (25 each). For this purpose, HS1 and V HS2 Both are connected to transmit their respective detection signals to the signal processing unit 104.

[0042] Furthermore, to monitor the degradation state of one of the first electrical interconnects 12, i.e., the interconnects belonging to the same upper or lower side as the currently controlled switch 11, a high-speed voltmeter connected within the power module assembly 100, as described with reference to Figure 1 or Figure 4, may also be used. This high-speed voltmeter V is connected between the Kelvin emitter Ke1 and the power emitter 13 in the configuration of Figure 1, or between the Kelvin emitter Ke1 and the supply terminal 102 in the configuration of Figure 4.HS1 This may be done by connecting a high-speed voltmeter V between both Kelvin emitters Ke1 and Ke2. Alternatively, a high-speed voltmeter V HS1 This may be performed by connecting the first electrical interconnect 12. Monitoring of the first electrical interconnect 12 involves recording the voltage detected after the switch 11 is turned off. This turn-off reduces the current in the first electrical interconnect 12, thereby generating a transient voltage in the first electrical interconnect 12 depending on its resistance and inductance values, and thus reflecting the number of bond wires in the first electrical interconnect 12 that are conducting or broken. This number can be estimated from the detection signal detected by a fast voltmeter in a similar manner to that described above for the second electrical interconnect 15 using the turn-on control of the switch 11. If the fast voltmeter is connected between both Kelvin emitters Ke1 and Ke2, the sign of the main peak of the detected detection signal indicates which of the first electrical interconnects 12 and 22 is degraded. Here too, the turn-off control of switch 11, as well as the voltage profiles corresponding to various numbers of broken wires in the first electrical interconnects 12 and 22, can be recorded in advance, and the detection signal detected by the high-speed voltmeter can be compared with these voltage profiles using a best-match algorithm. Thus, it becomes possible to monitor the entire interconnect using a single high-speed voltmeter, i.e., to identify the degradation state of the first interconnect and the second interconnects 12 and 15 inside the half-bridge branch 1 under test.

[0043] Figure 5 shows yet another possible configuration of the power module assembly 100, where the upper TS and lower BS of each half-bridge branch have similar structures. Thus, within half-bridge branch 1, a second diode 14' is added in parallel with switch 11, and a second switch 11' is added in parallel with diode 14. Diode 14' is oriented antiparallel to the conduction direction of switch 11, i.e., the cathode of diode 14' is oriented toward the supply terminal 101. Similarly, switch 11' is oriented antiparallel to diode 14, i.e., the conduction direction of switch 11' is oriented from the midpoint terminal 13 toward the supply terminal 102. A second control signal generator 10' is also added to control the turn-on and turn-off switching operation of switch 11'. For useful operation of such a power module assembly 100, the signs of the control signals of both control signal generators 10 and 10' are opposite, so that when switch 11 is turned on, switch 10' is turned off, and vice versa. Each other half-bridge branch of the power module assembly 100 has a structure similar to that of half-bridge branch 1 described above. Thus, half-bridge branch 2 is completed by another second switch 21', another second diode 24', and another control signal generator 20'. To implement the monitoring method of the present invention, a high-speed voltmeter V HS1 Here too, it is connected between the Kelvin emitter Ke1 and the power emitter 13 in the upper TS. And the positive load current I 103 During the operation period in which the high-speed voltmeter V is turned on after the switch 11 controlled by the control signal generator 10 is turned on, the high-speed voltmeter V is turned on after the switch 11 is turned on, which is controlled by the control signal generator 10. HS1 The detection signal detected by the second electrical interconnect 15 is used to monitor the voltmeter V after the switch 11 is turned off, which is controlled by the control signal generator 10. HS1 The detection signal detected by this device is used to monitor the first electrical interconnection unit 12.

[0044] In the configuration shown in Figure 5, a second high-speed voltmeter V is connected between the Kelvin emitter Ke1' and the supply terminal 102 at the lower BS. HS1 It is possible to add '. And negative load current I 103 During the period when the load current flows through the load supply terminal 103, i.e., when the load current flows from the load to the power module assembly 100, the high-speed voltmeter V is turned on after the switch 11' controlled by the control signal generator 10' is turned on. HS1 The detection signal detected by ' monitors the first electrical interconnect 12, and after the turn-off of the switch 11' controlled by the control signal generator 10', the voltmeter V HS1 The detection signal detected by ' is used to monitor the second electrical interconnection unit 15.

[0045] In practice, as shown in Figure 5, the connected switch 11 and diode 14' correspond to both MOSFET and diode semiconductor components formed on a single die, and the same applies to the switch 11' and diode 14 formed on separate dies. However, in most cases, the switch 11 and diode 14' are formed on separate dies, and the same applies to the switch 11' and diode 14. Each antiparallel combination of a switch and its corresponding diode may take either the connection configuration shown in Figure 6a or the connection configuration shown in Figure 6b. In these figures, the dies for switches 11 and 11' are denoted as D11 and D11', respectively, and the dies for diodes 14 and 14' are denoted as D14 and D14'. On the one hand, the space between dies D11 and D14' is separated in the upper TS, and on the other hand, the space between dies D11' and D14 is separated in the lower BS. Therefore, the emitter of switch 11 in the upper TS (11' in the lower BS) is connected to the anode of diode 14' in the upper TS (14 in the lower BS) via an additional electrical interconnect 16 in the upper TS (16' in the lower BS). The connection to the midpoint terminal 13 (supply terminal 102) may occur from between the additional electrical interconnect 16 (16') and the diode anode, as shown in Figure 6a, or from between the emitter of the switch and the additional interconnect electrical 16 (16'), as shown in Figure 6b. Table 1 below summarizes the degradation monitoring provided by the present invention, assuming that both the upper and lower sides have the connection configuration shown in Figure 6a or Figure 6b.

[0046] [Table 1]

[0047] Therefore, in each connection configuration of Figure 6a or Figure 6b, the high-speed voltmeter V is used for the four test conditions listed in Table 1. HS1 and H VS1By combining the analysis of the detection signals provided by ', it becomes possible to determine whether each of the electrical interconnects 12, 16, 15, and 16' is degraded. The high-speed voltmeter V connected as shown in Figure 5 HS2 and V HS2 Using this method, similar monitoring is possible for half-bridge branch 2.

[0048] The above description shows that the monitoring method of the present invention can be performed during useful operation of the power module assembly, and therefore assumes that all half-bridge branches are operating during the execution of the monitoring method. Alternatively, it is possible to operate only the branch under test during the execution of the monitoring method. For example, if the branch under test is half-bridge branch 1, the first or second step sequence may be performed by controlling the turn-on or turn-off switching operation of control signal generator 10 or 10' while continuously keeping the control signal generators of all other half-bridge branches in the off state. This reduces the possibility of misidentification that may occur when identifying a damaged interconnect of a separate half-bridge branch from the detection signal.

[0049] Finally, the monitoring method of the present invention may be carried out using a different type of sensor than a voltmeter. For example, an ammeter can be used as an alternative when connected in series rather than in parallel with the relevant electrical interconnect.

Claims

1. A method for monitoring the degradation state of electrical interconnects in a power module assembly (100), wherein the power module assembly comprises at least two half-bridge branches (1, 2) connected in parallel to each other between a first supply terminal and a second supply terminal (101, 102), Each half-bridge branch (1, 2) comprises a first switch (11, 21) connected in series, a first electrical interconnect (12, 22), a center terminal (13, 23), a first diode (14, 24), and a second electrical interconnect (15, 25), wherein the center terminal is located between the first switch and the first electrical interconnect on one side, and between the first diode and the second electrical interconnect on the other side. The midpoint terminals (13, 23) of all half-bridge branches (1, 2) are connected to the load supply terminal (103) of the power module assembly (100). The connection direction of the first diodes (14, 24) in each half-bridge branch (1, 2) is such that when the first switch (11, 21) of the half-bridge branch is turned on, the reverse recovery current generated from the first diode, which transitions from a conductive state to a disconnected state, flows through the second electrical interconnect (15, 25) and at least partially through the first electrical interconnect (12, 22). The method includes connecting at least one sensor to the power module assembly (100) such that at least one detection signal transmitted by the at least one sensor is sensitive to the time variation of the current flowing through the first electrical interconnect (12) of one of the half-bridge branches (1, 2) of the power module assembly called the branch under test (1), The above method is the following first step sequence: - To acquire the detection signal that appears after the first switch (11) of the test target branch (1) is turned on, - Based on the characteristics of the acquired detection signal, information regarding the deterioration state of the second electrical interconnect (15) of the test target branch (1) is estimated. Methods that further include this.

2. The method according to claim 1, wherein the second electrical interconnect (15) of the test branch (1) includes a plurality of wires connected in parallel with each other, and the information relating to the deterioration state of the second electrical interconnect of the test branch includes the number of damaged wires among the wires of the second electrical interconnect.

3. The characteristics of the detection signal used to estimate the deterioration state of the second electrical interconnection section (15) of the test target branch (1) are, - Whether at least one peak value of the detection signal is higher than the threshold in absolute value, - A part of the code of the detection signal, and - The difference in shape between two detection signals acquired during the execution of each of the first step sequences associated with each of the same half-bridge branches (1, 2) of the power module assembly (100) used as the branch under test. The method according to claim 1 or 2, comprising at least one of the following.

4. The at least one of the sensors is connected in parallel to one of the first electrical interconnects (12, 22) of the half-bridge branches (1, 2) of the power module assembly (100), which is different from the half-bridge branch of the other voltage sensor, and the two voltage sensors (V ＨＳ１ , V ＨＳ２ ) equipped with, Alternatively, the first nodes (Ke1, Ke2) are located between the first switches (11, 21) and the first electrical interconnects (12, 22) in each of the at least two half-bridge branches (1, 2) of the power module assembly (100), and the at least one sensor is a voltage sensor (V) connected between the first nodes of each of the two half-bridge branches. ＨＳ１ ) equipped with, The method according to any one of claims 1 to 3.

5. The following is the second step sequence: - Using at least one of the sensors, obtain another detection signal that appears after the first switch (11) of the test branch (1) is turned off, - Based on the characteristics of the acquired other detection signal, information regarding the deterioration state of the first electrical interconnect (12) of the test target branch (1) is estimated. The method according to any one of claims 1 to 4, further comprising:

6. The second supply terminal (102) is a reference terminal or a ground terminal. - The first switch (11) and the first electrical interconnect (12) of the test branch (1) are connected in series between the midpoint terminal (13) and the second supply terminal (102) of the test branch. - The first electrical interconnect (12) is connected between the first switch (11) and the second supply terminal (102) in the test branch (1), and - The at least one sensor is a voltage sensor (V) connected in parallel with the first electrical interconnection unit (12). ＨＳ１ ) equipped with, The method according to any one of claims 1 to 5.

7. The method according to any one of claims 1 to 6, wherein each of the half-bridge branches (1, 2) of the power module assembly (100) further comprises a second switch (11', 21') connected in parallel with the first diode (14, 24) of the half-bridge branch, and each of the half-bridge branches is arranged such that the first and second switches of the half-bridge branch are turned on and off simultaneously but in opposite directions during operation of the power module assembly, and the conduction direction of each of the first and second switches is opposite to the conduction direction of the corresponding first or second diode connected in parallel.

8. The first step sequence is executed twice for the test branch (1), and once for the load current (I) flowing out from the power module assembly (100) at the load supply terminal (103). １０３ The method according to claim 7, wherein the method is performed once to estimate the information regarding the degradation state of one of the first interconnection (12) and the second interconnection (15) of the test branch (1) with respect to the load current returning to the power module assembly at the load supply terminal, and the method is performed once to estimate the information regarding the degradation state of the other of the first interconnection and the second interconnection of the test branch with respect to the load current returning to the power module assembly at the load supply terminal.

9. The method according to claim 7 or 8, wherein each second switch (11', 21') is an isolated grid bipolar transistor type or a MOSFET type.

10. The method according to any one of claims 1 to 9, wherein each first switch (11, 21) is of the isolated grid bipolar transistor type or MOSFET type.

11. A power module assembly (100) comprising at least two half-bridge branches (1, 2) connected in parallel to each other between a first supply terminal and a second supply terminal (101, 102), Each half-bridge branch (1, 2) comprises a first switch (11, 21) connected in series, a first electrical interconnect (12, 22), a center terminal (13, 23), a first diode (14, 24), and a second electrical interconnect (15, 25), wherein the center terminal is located between the first switch and the first electrical interconnect on one side, and between the first diode and the second electrical interconnect on the other side. The midpoint terminals (13, 23) of all half-bridge branches (1, 2) are connected to the load supply terminal (103) of the power module assembly (100). The connection direction of the first diodes (14, 24) in each half-bridge branch (1, 2) is such that when the first switch (11, 21) of the half-bridge branch is turned on, the reverse recovery current generated from the first diode, which transitions from a conductive state to a disconnected state, flows through the second electrical interconnect (15, 25) and at least partially through the first electrical interconnect (12, 22). The power module assembly (100) is - Means (10) for controlling the turn-on of the first switch (11) of one of the half-bridge branches (1, 2) of the power module assembly (100) called the branch to be tested (1), - After the first switch (11) of the branch to be tested is turned on, at least one sensor is connected to deliver at least one detection signal that is sensitive to the time variation of the current flowing through the first electrical interconnect (12) of the branch to be tested, - At least one signal processing unit (104) connected to receive the detection signal from the at least one sensor and configured to estimate information regarding the degradation state of the second electrical interconnect (15) of the branch (1) being tested based on the characteristics of the detection signal. A power module assembly that further includes [the following features].

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