Power electronics arrangement with parallel-connected semiconductor switches, power electronics device, motor vehicle and method for manufacturing a power electronics arrangement

Abstract

Power electronics arrangement (1) comprising a switching device (3) for switching an electrical conductor section (2) of the power electronics arrangement (1), wherein the switching device (3) comprises several semiconductor switches (4) connected in parallel, controlled jointly via supply lines (8, 8a, 8b, 8c, 8d) by a control unit (6), which switch via the respective supply line (8, 8a, 8b, 8c, 8d) upon reaching a switching charge state, characterized in that all supply lines (8, 8a, 8b, 8c, 8d) have at least substantially the same electrical resistance despite at least partially different lengths, wherein the supply lines (8, 8a, 8b, 8c, 8d) are bond wires (9) and wherein supply lines (8, 8a, 8b, 8c, 8d) of different lengths are used to compensate for resistance differences due to the length of the supply lines (8, 8a, 8b, 8c, 8d). 8c, 8d) differ in at least one adaptation property besides length, where the adaptation property is the material,the materials from which the leads (8, 8a, 8b, 8c, 8d) are made, wherein the different materials differ in their purity such that the longest leads (8, 8a, 8b, 8c, 8d) consist of a pure base material, in particular copper or aluminum, while the purity decreases with length for shorter leads (8, 8a, 8b, 8c, 8d).

Description

[0001] The invention relates to a power electronics arrangement comprising a switching device for switching an electrical conductor section of the electronics arrangement, wherein the switching device has several semiconductor switches connected in parallel, which are jointly controlled via supply lines by a control unit and switch via the respective supply line when a switching charge state is reached. The invention further relates to a power electronics device, a motor vehicle, and a method for manufacturing a power electronics arrangement.

[0002] Semiconductor switches are frequently used in power electronics applications, such as in motor vehicles, to keep sections of a line conductive or non-conductive, or, in some cases, to create specific resistances along the line. Semiconductor switches for power electronics are typically designed for specific maximum currents. Therefore, it has been proposed to use several semiconductor switches connected in parallel within a switching device to enable the switching of higher currents. The multiple semiconductor switches connected in parallel then act as a single, large switch. Semiconductor switches (often also referred to as power semiconductors) can be used, for example, in power electronics devices such as pulse inverters, charging devices, DC-DC converters, and the like.

[0003] Manufacturing techniques for IGBTs (Insulated Gate Bipolar Transistors), also known as silicon switches, are now available that allow for the production of large switches with high current-carrying capacity, so that in many cases one or a few, for example two, IGBTs are sufficient. In particular, it is possible to fabricate very large chips from wafers.

[0004] In current developments, however, MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), especially those based on SiC, are gaining in importance. However, the defect rate on the wafer is still relatively high with current manufacturing processes, meaning that only small chips, and therefore semiconductor switches designed for low maximum currents, can be produced. Therefore, when switching devices for high currents are required, larger numbers of MOSFETs are often connected in parallel as semiconductor switches, for example, four, six, or eight MOSFETs.

[0005] Since the semiconductor switches of the switching device are to be controlled together, each semiconductor switch requires a connection from a control unit to its gate terminal. The control unit applies the corresponding switching signals, usually by applying a voltage, simultaneously to the various connections. However, with different connection lengths, especially with an increasing number of semiconductor switches, this can lead to different switching times for the individual semiconductor switches. Semiconductor switches typically switch depending on a specific gate-source voltage, which is generated by charging a corresponding capacitance across the gate terminal of the semiconductor switch; in other words, a specific switching charge state must be reached.For different geometric positions and thus different resulting lead lengths, the time it takes to reach the switching state (switching time) varies, assuming the lead design is otherwise identical (e.g., using standard bond wires). Semiconductor switches with the shortest leads switch first and are therefore initially subjected to the full total current through the lead section until other semiconductor switches also switch on. This means that either the semiconductor switches must be oversized to accommodate this load, or the lifespan of the semiconductor switches, and consequently the switching device, is reduced.

[0006] DE 10 2014 117 385 A1 relates to a power semiconductor circuit with electrically parallel connected current valves and a control circuit designed to control the electrically parallel connected current valves. The control circuit is intended to generate control signals such that, when the electrically parallel connected current valves are switched off, a current valve designated by the control circuit switches off for a longer duration than the other electrically parallel connected current valves, or, if the power semiconductor circuit has two electrically parallel connected current valves, for a longer duration than the other electrically parallel connected current valves.This is intended to achieve advantages in terms of reducing voltages and parasitic inductances. It is assumed that differences in the switching behavior of the current-limiting valves arising from varying cable lengths can be neglected.

[0007] WO 2013 / 0 093 410 A1 concerns a control unit for controlling a power semiconductor switching device into a plurality of states. It also proposes intermediate states in which a specific resistance of the switching device is given, in order to switch hundreds of power semiconductor switching devices in a controlled, synchronized manner. A feedback control circuit is used that utilizes negative feedback, so that the behavior of the switching device can be controlled based on measured voltage and current feedback signals, such that the switching device behaves like a passive resistor. By adjusting the parameters of the control loop, the effective resistance of the switching device can be adjusted.

[0008] WO 2015 / 001 311 A1 concerns methods and circuits for controlling the switching operations of parallel coupled power semiconductor switching devices, for example in a power converter. It proposes introducing switching delays for the different switching devices relative to corresponding command signals in order to reduce the variance between the switching delays of the multitude of switching devices and / or to reduce the variation in the switching delays of a switching device over time.

[0009] DE 696 26 371 T2 discloses a modular semiconductor assembly with switching elements, each of whose gates is fitted with a gate resistor. The gate resistors have the effect of balancing the respective gate currents of the switching elements during the on / off control processes of the switching elements. If the connection paths between the respective gates of the switching elements and the signal terminal plate are of different lengths, this can lead to unequal gate currents at the switching elements. To achieve equal, or approximately equal, gate currents, the gate resistors are connected upstream of the respective switching elements.

[0010] DE 10 2008 040 480 A1 discloses a semiconductor module with one or more power semiconductors connected in parallel. Each power semiconductor has a switching terminal which is electrically connected to a contact point via a resistance wire, in particular a bond wire. If several power semiconductors are present, each of the resistance wires can have a different resistance value.

[0011] The invention is based on the objective of providing an improved method for synchronizing the switching-on behavior of power semiconductor switches in a parallel arrangement, which in particular does not require a massive increase in control effort.

[0012] To solve this problem, a power electronics arrangement, a power electronics device, a motor vehicle, and a method for manufacturing a power electronics arrangement with the features of the dependent claims are provided. According to the invention, all leads, despite at least partially differing lengths, exhibit at least substantially the same electrical resistance.

[0013] The invention is based on the understanding that the key factor leading to different switching times for different lengths of (otherwise identical) supply lines is the resulting difference in ohmic resistance, which can delay reaching the switching charge state, and thus, in particular, a switching voltage in a capacitive arrangement. Therefore, it is proposed to adjust the resistance of the supply lines (control lines) according to their geometric length so that all supply lines have the same ohmic resistance, thereby achieving at least substantially identical switching times. In this way, the turn-on behavior of the semiconductor switches can be synchronized, and overloading of individual semiconductor switches can be avoided.Oversizing the power semiconductor switches is no longer necessary, thus saving costs and installation space. At the same time, the power electronics assembly becomes more robust, thereby improving the quality and lifespan of the power electronics device utilizing it.

[0014] The leads connect the control outputs of the control unit, for example, a control chip, to the gate terminals of the respective semiconductor switches. While the semiconductor switches can generally be IGBTs, the inventive method is particularly advantageous for MOSFETs, especially SiC MOSFETs, so that the semiconductor switches can preferably be MOSFETs. The power electronics arrangement can, for example, comprise three to ten semiconductor switches; however, it is also possible to use more than ten semiconductor switches, for example, up to fifty, up to one hundred, or even up to one thousand semiconductor switches. According to the invention, the leads are bond wires. The bond wire configuration is particularly preferred because the properties that influence the resistance can be adapted to them in a particularly simple manner.

[0015] If the semiconductor switches are designed as individual chips, as is usual, the control unit, which can also be called a control module, can also be a chip, and the corresponding connections of the chips can be connected via the bond wires, in particular control connections of the control unit with gate connections of the semiconductor switches.

[0016] Specifically, it is provided that, to compensate for differences in resistance due to the length of the supply lines, supply lines of varying lengths differ in at least one adaptation property in addition to their length. According to the invention, the adaptation property is the material from which the supply lines are made. Another adaptation property can be the lateral expansion, in particular the thickness, of the supply lines. In other words, for example, the thickness of the supply line, such as its diameter / edge length, can be varied to reduce increased resistance due to its length. Regarding the material, it is provided that the different materials differ in their purity.The material is therefore varied, namely with regard to purity, electrical conductivity and / or alloy, in order to compensate for resistance differences arising from different lengths and to provide supply lines with the same resistance.

[0017] This design starts with a base material, particularly copper or aluminum. The longest connecting leads are then made of the pure base material, while the purity decreases with length for shorter leads. The pure material has the highest conductivity, which decreases with decreasing purity, compensating for the resistance reduction due to length.

[0018] In addition to the power electronics arrangement, the invention also relates to a power electronics device comprising at least one power electronics arrangement according to the invention. The descriptions regarding the power electronics arrangement also apply to the power electronics device. The power electronics device can, for example, be a converter device, in particular a pulse inverter and / or a DC / DC converter, or a charging device for a high-voltage battery to be installed in a motor vehicle.

[0019] A motor vehicle according to the invention comprises at least one power electronics device according to the invention. The motor vehicle can, in particular, be an electric vehicle or a hybrid vehicle, which thus includes an electric machine connected to a high-voltage network whose voltage is higher than the voltage of a low-voltage network of the motor vehicle. The power electronics device can then be, for example, a converter via which the electric machine is connected to the high-voltage network, or it can also be a power electronics device connected to the high-voltage network in some other way, for example, a DC-DC converter connecting the high-voltage network to the low-voltage network.

[0020] Finally, the invention also relates to a method for manufacturing a power electronics arrangement comprising a switching device for switching an electrical conductor section of the power electronics arrangement, wherein the switching device has several semiconductor switches connected in parallel, which are jointly controlled via supply lines by a control unit and switch via the respective supply line when a switching charge state is reached. The method includes adapting supply lines of different lengths by selecting at least one matching property such that the electrical resistances of the supply lines are at least substantially the same. In particular, a power electronics arrangement according to the invention can be manufactured using this method.In general, different matching properties are varied depending on the length in order to match the resistances of the supply lines as closely as possible and thus achieve the most accurate possible synchronization of the switching times of the semiconductor switches.

[0021] Specifically, for example, placement equipment capable of assembling different types of conductors with a common placement head can be used to carry out the process. Such placement equipment has already been proposed, for example, for pick-and-place processes.

[0022] The explanations regarding the previous items according to the invention also apply to the process, of course.

[0023] Further advantages and details of the present invention will become apparent from the exemplary embodiments described below and from the drawing. The drawings show: Fig. 1 a schematic diagram of a power electronics arrangement according to the invention, Fig. 2 a known design of supply lines, Fig. 3 a design of supply lines according to the invention, and Fig. 4 a schematic diagram of a motor vehicle according to the invention.

[0024] Fig. Figure 1 shows a schematic diagram of a power electronics arrangement 1 according to the invention, comprising a conductor section 2 which is to be switched by means of a switching device 3. Since the current potentially flowing through the conductor section 2 exceeds the maximum permissible currents for some of the power semiconductor switches used here, in this case SiC MOSFETs, the switching device 3 has a plurality, here for example six, of such semiconductor switches 4, all of which are connected in parallel. For the sake of simplicity, the semiconductor switches 4 are only indicated schematically by their corresponding chips. In addition to the connections for the correspondingly branched conductor section 2, i.e., the source connection and the drain connection, which are not shown in detail here, each of the semiconductor switches 4, implemented as chips, has a gate connection 5 as a control connection.

[0025] These semiconductor switches 4 are to be controlled by a control unit 6, which is also designed as a chip, in such a way that they behave like a single, large switch. For this purpose, corresponding control terminals 7 of the control unit 6 are connected to a respective gate terminal 5 of the semiconductor switches 4 via leads 8, which are designed here as bond wires 9. Due to the geometric arrangement of the semiconductor switches 4, the leads 8 have different lengths. Nevertheless, due to the clever selection of lengths with different matching characteristics in the power electronics arrangement, Fig. 1 ensures that the supply lines 8 all have the same resistance, since then, with simultaneous control signal generation by the control unit 6, it is possible to switch the semiconductor switches 4 on and off as precisely as possible.

[0026] Fig. Figure 2 shows a known possibility for such an adaptation. Two leads 8a and 8b are shown, each connecting a gate terminal 5 and a control terminal 7 of the control unit 6. Lead 8b is clearly longer than lead 8a. The resulting increase in resistance, assuming identical configurations of leads 8a and 8b, is illustrated in the example of... Fig. 2. This is compensated for by increasing the diameter, and therefore the thickness, of the supply line 8b compared to that of the supply line 8a, so that the supply lines 8a, 8b nevertheless have the same ohmic resistance.

[0027] One possibility according to the invention illustrates Fig. Figure 3 shows a schematic representation. Two leads 8c and 8d of different lengths are shown there. However, the matching property here is the material from which the leads 8c and 8d are made. In this case, the material of lead 8d, which is shown hatched for differentiation, has a higher electrical conductivity than the material of lead 8c, thus compensating for the difference in length, at least substantially. The material difference lies in the purity.

[0028] Fig.Figure 4 shows a schematic diagram of a motor vehicle 10 according to the invention. In this case, it is an electric motor vehicle which has an electric machine 11 in its drive train (not shown in detail). The electric machine 11 is connected via a converter 12, as a power electronics component 13, to a high-voltage network 14, which is supplied by a battery 15. By way of example, a DC-DC converter 16 and an on-board charger 17 for the battery 15 are shown connected to the high-voltage network 14 as further power electronics devices 13. In this case, all these power electronics devices 13 comprise at least one power electronics arrangement 1 of the type according to the invention.

Claims

[1] Power electronics arrangement (1) comprising a switching device (3) for switching an electrical line section (2) of the power electronics arrangement (1), wherein the switching device (3) comprises several semiconductor switches (4) connected in parallel, controlled jointly via supply lines (8, 8a, 8b, 8c, 8d) by a control unit (6), which switch via the respective supply line (8, 8a, 8b, 8c, 8d) when a switching charge state is reached, characterized by, that all leads (8, 8a, 8b, 8c, 8d) exhibit at least substantially the same electrical resistance despite at least partially differing lengths, wherein the leads (8, 8a, 8b, 8c, 8d) are bond wires (9), and wherein, to compensate for resistance differences due to the length of the leads (8, 8a, 8b, 8c, 8d), leads (8, 8a, 8b, 8c, 8d) of different lengths differ in at least one matching property besides length, wherein the matching property is the material from which the leads (8, 8a, 8b, 8c, 8d) are made, wherein the different materials differ in their purity such that the longest leads (8, 8a, 8b, 8c, 8d) consist of a pure base material, in particular copper or aluminum, while the purity decreases with length for shorter leads (8, 8a, 8b, 8c, 8d). Supply lines (8, 8a, 8b, 8c, 8d) decrease. [2] Power electronics arrangement according to claim 1, characterized bythat the semiconductor switches (4) are MOSFETs, in particular SiC MOSFETs, and / or that the power electronics arrangement (1) comprises three to ten semiconductor switches (4). [3] Power electronics arrangement according to one of the preceding claims, characterized by , that another adaptation property is a lateral extent, in particular thickness, of the leads (8, 8a, 8b, 8c, 8d). [4] Power electronics arrangement according to claim 3, characterized by that the different materials differ in their electrical conductivity. [5] Power electronics device (13) comprising at least one power electronics arrangement (1) according to any one of the preceding claims. [6] Power electronic device according to claim 5, characterized bythat it is a converter device, in particular a pulse inverter and / or a DC voltage converter (13), or a charging device for a high-voltage battery (15) to be installed in a motor vehicle (10). [7] Motor vehicle (10) comprising at least one power electronics device (13) according to claim 5 or 6. [8] Method for manufacturing a power electronics arrangement (1) comprising a switching device (3) for switching an electrical conductor section (2) of the power electronics arrangement (1), wherein the switching device (3) comprises several semiconductor switches (4) connected in parallel, controlled jointly via supply lines (8, 8a, 8b, 8c, 8d) by a control unit (6), switching via the respective supply line (8, 8a, 8b, 8c, 8d) when a switching charge state is reached, wherein the supply lines (8, 8a, 8b, 8c, 8d) are bond wires (9), characterized by, that leads (8, 8a, 8b, 8c, 8d) of different lengths are matched by choosing at least one matching property such that the electrical resistances of the leads (8, 8a, 8b, 8c, 8d) are at least substantially the same, wherein the matching property is the material of which the leads (8, 8a, 8b, 8c, 8d) are made, wherein the different materials differ in their purity such that the longest leads (8, 8a, 8b, 8c, 8d) are made of a pure base material, in particular copper or aluminum, while the purity decreases with length for shorter leads (8, 8a, 8b, 8c, 8d).

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