Half-bridge in an inverter and method for reducing parasitic inductances in a half-bridge of an inverter

Abstract

Half-bridge (2) in an inverter (1) in which a high-side power switch (3) and a low-side power switch (4) are arranged, characterized in that a first connecting wire (8) of the high-side power switch (3) and a second connecting wire (9) of the low-side power switch (4) are arranged in direct connection between the connecting wires (8, 9) and in a common bore in a printed circuit board (6) are electrically connected to conductor traces (12) on the printed circuit board (6) and that pins (10) of the power switches (3, 4) have a bend at a first distance from the power switch (3, 4) and the connecting wires (8, 9) have a bend at a second distance from the power switch (3, 4), wherein the second distance is greater than the first distance.

Description

[0001] The invention relates to a half-bridge in an inverter in which a high-side circuit breaker and a low-side circuit breaker are arranged.

[0002] The invention also relates to a method for reducing parasitic inductances in a half-bridge of an inverter, wherein a high-side power switch and a low-side power switch are provided in a half-bridge.

[0003] It is well known that inverters, also known as voltage converters, convert an input DC voltage into an output AC voltage, which is used, for example, to power an electric motor. This allows for the controlled operation of an electric motor, such as one used in an electric refrigerant compressor in a vehicle.

[0004] A very common circuit arrangement for the controlled control of electric drives using an inverter is a so-called B6 bridge or B6 bridge circuit.

[0005] The B6 bridge comprises three half-bridges, each consisting of a high-side power switch and a low-side power switch, where these power switches or semiconductor power switches are designed, for example, as MOSFETs (metal-oxide-semiconductor field-effect transistors) or IGBTs (insulated-gate bipolar transistors).

[0006] Within a half-bridge, one terminal of the high-side circuit breaker is directly connected to one terminal of the low-side circuit breaker and to an output of the half-bridge or inverter. This output carries the voltage (U, V, or W) generated by the half-bridge, for example, to operate a connected electric motor.

[0007] Between the upper high-side power switch and the lower low-side power switch of a half-bridge, also known as a commutation cell, in a typical circuit configuration, undesirable parasitic inductances develop. To minimize these unwanted parasitic inductances, the semiconductor power switches within a half-bridge are positioned close together on a printed circuit board.

[0008] An example of this state of the art is known from http: / / www.irf.com / productinfo / iqbt / pcb-layoutquidelines.pdf.

[0009] In practice, semiconductor power switches are frequently used, which typically have a TO220 or TO247 transistor package. These components have three terminals, also known as leads or pins. For mounting on a printed circuit board (PCB), these transistors, i.e., the semiconductor power switches of half-bridges, are arranged using a through-hole mounting technique (THT). The leads are inserted through pre-drilled holes in the PCB and soldered to corresponding traces. The semiconductor power switches can be mounted vertically or horizontally on the PCB, with the leads bent accordingly.The three connecting wires can be the gate, collector and emitter terminals of an IGBT device or the gate, source and drain terminals of a MOSFET device.

[0010] Despite the close arrangement of these semiconductor power switches in a half-bridge on the circuit board, a gap remains between the semiconductor power switches, which can lead to the formation of unwanted parasitic inductance.

[0011] This remaining parasitic inductance leads to longer switching times for the semiconductor power switches, and thus to an increase in switching energy loss or switching power loss. Besides the associated lower efficiency due to the higher switching power loss, this results in additional heating of the semiconductor power switches. To counteract this additional heating, a more complex cooling concept for the semiconductor power switches is necessary, which leads to higher manufacturing costs.

[0012] The remaining parasitic inductance hinders the development of components and assemblies, such as inverters, with ever-improving performance, for example through the use of higher switching frequencies.

[0013] To improve the performance or effectiveness of modern inverters, it is necessary to further reduce the parasitic inductances that form between the high-side power switch and the low-side power switch of a commutation cell or half-bridge.

[0014] Therefore, there is a need to improve the known state of the art in order to be able to operate inverters with higher switching frequencies without further increasing the cooling effort.

[0015] German patent application DE 10 2015 200 716 A1 describes a switched-mode power supply and a method for operating the switched-mode power supply with a plurality of parallel branches. Each parallel branch has two series-connected controllable switches and an inductor connected between the two switches and an output node. Furthermore, the switched-mode power supply includes a capacitor connected between the output nodes of the parallel branches and ground.A controller is configured to switch the two series-connected controllable switches of each parallel branch such that the first switch of a parallel branch is switched from a conducting to a blocking state when the current through a coil of the parallel branch reaches a first current value greater than 5 amperes, and the second switch is switched from a conducting to a blocking state when the current through the coil of the parallel branch reaches a second current value less than 0 amperes. It is described that, on a circuit board where the switching power supply is implemented, instead of three through-holes for the leads from three pairs of switches to a terminal or to a trace connected to the terminal, a single through-hole is sufficient because the three leads are short-circuited anyway.

[0016] DE 10 2017 207 564 A1 describes a semiconductor module with at least two semiconductor components, which are arranged within a housing between two electrical conductor elements and are electrically connected to the electrical conductor elements. Each electrical conductor element has a contact extension that protrudes from the housing, and two contact extensions arranged in different planes are connected to each other outside the housing via a contact element, which forms a current path between the two contact extensions outside the housing.

[0017] The object of the invention is to provide a half-bridge or commutation cell which exhibits reduced parasitic inductance and is simple and inexpensive to manufacture. The reduction of parasitic inductance is intended to occur, in particular, between a high-side circuit breaker and a low-side circuit breaker.

[0018] Furthermore, the cooling requirements for such a half-bridge should be reduced. Electromagnetic interference should also be reduced.

[0019] The problem is solved by an object having the features according to claim 1 of the independent patent claims. Further developments are specified in the dependent patent claims.

[0020] The problem is also solved by a method with the features according to claim 4 of the independent patent claims. Further developments are specified in the dependent patent claims.

[0021] The first aspect of the invention provides a half-bridge in an inverter, in which a high-side circuit breaker and a low-side circuit breaker are arranged. A first connecting wire of the high-side circuit breaker and a second connecting wire of the low-side circuit breaker are electrically connected in a direct line between the connecting wires and in a common bore in a printed circuit board, via conductors on the circuit board. According to the invention, the pins of the circuit breakers have a bend at a first distance from the circuit breaker, and the connecting wires have a bend at a second distance from the circuit breaker, the second distance being greater than the first distance.

[0022] As a second aspect of the invention, a method for reducing parasitic inductances in a half-bridge of an inverter is provided, wherein in this method a high-side power switch and a low-side power switch are provided in a half-bridge, and wherein a first connecting wire of the high-side power switch and a second connecting wire of the low-side power switch are provided in direct connection between the connecting wires and electrically connected in a common bore in a printed circuit board with conductor traces on the printed circuit board. According to the invention, the pins of the power switches are provided with a bend at a first distance from the power switch and the connecting wires are provided with a bend at a second distance from the power switch, the second distance being greater than the first distance.

[0023] The aim is to further reduce the distance between the high-side and low-side power switches of a commutation cell. Specifically, the distance between two connecting wires or pins of the two semiconductor power switches within a half-bridge on a printed circuit board is reduced. For this reduction, the connecting wire of the emitter of the high-side power switch and the connecting wire of the collector of the low-side power switch are, for example, designed using IGBT components.

[0024] Alternatively, the source terminal wire of the high-side circuit breaker and the drain terminal wire of the low-side circuit breaker can also be provided in a version with MOSFET components to reduce the distance.

[0025] This reduction in the distance between the aforementioned connecting wires of the components is achieved by arranging the aforementioned connecting wires in a common hole on the circuit board.

[0026] For this purpose, it is intended, for example, to bend the emitter lead of the high-side circuit breaker and the collector lead of the low-side circuit breaker differently from the other leads or pins. In the example of a horizontal mounting of the semiconductor circuit breakers, the emitter lead of the high-side circuit breaker and the collector lead of the low-side circuit breaker, viewed from the respective component, have a longer straight section compared to the other two leads or pins of the components. At the end of this straight section, the aforementioned leads have a bend.

[0027] This longer straight section of the aforementioned connecting wires allows them to be arranged in a common hole in the circuit board and, for example, soldered together with a solder pad or conductor track on the circuit board.

[0028] This arrangement, for example of the connecting wire of the emitter of the high-side circuit breaker and the connecting wire of the collector of the low-side circuit breaker, leads to a direct connection between these component terminals and thus to a significant reduction in the parasitic inductances that develop.

[0029] This reduction in parasitic inductances makes it possible to operate inverters with this arrangement of semiconductor power switches in the half-bridges according to the invention at higher switching frequencies. This arrangement of the same semiconductor power switches, known from the prior art, does not lead to such high component heating, even at higher switching frequencies, caused by higher component losses, which could impair the function of the components or even lead to their destruction. The efficiency of such inverters is therefore increased.

[0030] Due to the lower parasitic inductances, electromagnetic interference caused by the half-bridges or inverter arrangement is also reduced. This allows for the use of simpler and cheaper EMC filters (electromagnetic compatibility) to eliminate the electromagnetic interference that occurs.

[0031] Since the lower switching loss energy or switching loss power reduces the power requirements for the semiconductor power switches, less expensive components can be used for the semiconductor power switches.

[0032] For example, the present invention can be advantageously used in the field of hybrid and electric vehicles. Such vehicles also employ inverters in the area of ​​electric refrigerant compressors, which can be operated more efficiently and manufactured at lower costs.

[0033] Further details, features, and advantages of embodiments of the invention will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings. These show: Fig. 1: a B6 bridge in a state-of-the-art inverter, Fig. 2: A prior art arrangement of two semiconductor power switches on a printed circuit board (inverter board) in a side view, Fig. 3: an arrangement of two semiconductor power switches on a printed circuit board section in a practical implementation according to the state of the art, Fig. 4: an equivalent circuit diagram of a half-bridge according to the state of the art, Fig. 5: an embodiment of the arrangement according to the invention in a side view, Fig. 6: the circuit breakers of a half-bridge in an arrangement according to Fig. 5 in a perspective view without a circuit board and Fig. 7: An arrangement of two semiconductor power switches according to the invention on a printed circuit board section in a practical implementation.

[0034] The Fig. Figure 1 shows a B6 bridge in a prior art inverter 1. The inverter 1 comprises, by way of example, three half-bridges 2, each containing a high-side circuit breaker 3 and a low-side circuit breaker 4. The half-bridges 2 are arranged, for example, between the input potentials HV+ and HV-.

[0035] The half-bridges 2 are configured such that one terminal or first connecting wire 8 of the high-side circuit breaker 3 is directly connected to one terminal or second connecting wire 9 of the low-side circuit breaker 4. The output of the respective phase 5 (U, V, W) is also connected at this connection point.

[0036] The first terminal 8 of the high-side circuit breaker 3, which is connected to the second terminal 9 of the low-side circuit breaker 4, can be an emitter terminal of the high-side circuit breaker 3. In this case, the second terminal 9 of the low-side circuit breaker 4 is a collector terminal.

[0037] The first terminal 8 of the high-side circuit breaker 3, which is connected to the second terminal 9 of the low-side circuit breaker 4, can alternatively be a source terminal of the high-side circuit breaker 3. In this case, the second terminal 9 of the low-side circuit breaker 4 is a drain terminal.

[0038] In the Fig. Figure 1 also shows the freewheeling diodes known from the prior art at the power switches 3 and 4.

[0039] The Fig. Figure 2 shows an arrangement of two semiconductor power switches 3, 4 on a printed circuit board 6, such as an inverter printed circuit board or inverter board, from the prior art.

[0040] The power switches 3 and 4 of a half-bridge 2 are, for example, housed in a TO220 or TO247 package. For electrical connection of the power switches 3 and 4 to corresponding traces on the printed circuit board 6, the power switches 3 and 4 each have three pins 10, for example, for the emitter, collector, and gate connections of the respective power switch 3 or 4. One of the three pins 10 of the high-side power switch 3 is the first connection 8, while one pin 10 of the low-side power switch 4 is the second connection 9.

[0041] The three pins 10 of each power switch 3 or 4 are bent or angled at a defined initial distance from the component housing at an angle of, for example, 90 degrees. In this way, the power switches 3 and 4 can be inserted into holes in the printed circuit board 6 by means of through-hole mounting and electrically connected to corresponding conductors on the printed circuit board 6, for example, using a soldering process.

[0042] These horizontally arranged circuit breakers 3 and 4 can, as in the Fig. 2, shown, is connected to a heat sink 7 to dissipate the heat generated in the circuit breakers 3 and 4. These connections can be made, for example, using a screw or a rivet.

[0043] For electrical insulation and to improve heat conduction between the power switches 3 and 4 and the heat sink 7, a thermally conductive material 11 (TIM, Thermal Interface Material) is arranged between them.

[0044] The Fig. Figure 3 shows a practical implementation of an arrangement of two circuit breakers 3 and 4 on a section of a printed circuit board 6. For better understanding, two circuit breakers 3 and 4 belonging to a half-bridge 2 are arranged or soldered onto a section of a printed circuit board 6. In practice, the circuit breakers 3 and 4 are arranged in the same way, for example, on a larger printed circuit board 6 implementing the functionalities of an inverter 1, such as an inverter board.

[0045] In the left part of the Fig. Figure 3 shows a view of the component side of the circuit board 6, while the right part of the Fig. Figure 3 shows a view of the conductor tracks on circuit board 6. In the right part of the Fig. 3 is the low-side power switch 4, in this case a low-side power transistor, represented by a dash-dash line, since it is hidden by the circuit board 6.

[0046] For example, in the Fig. 3 only one conductor 12 is shown, which realizes the connection of the first connecting wire 8 of the high-side circuit breaker 3 with the second connecting wire 9 of the low-side circuit breaker 4.

[0047] This area of ​​the connecting wires 8 and 9, as well as the depicted conductor 12, is the area where the parasitic inductances develop. (Not shown in the...) Fig. 3 is the connection of conductor 12 with the output for the associated phase 5.

[0048] The three pins 10 of each power switch 3 or 4 are bent at a 90-degree angle at a defined initial distance from the component housing itself. These bent pins 10 are inserted into the holes provided in the circuit board 6 and soldered to a conductor 12 or a solder pad on the conductor side of the circuit board 6.

[0049] Here, the circuit breakers 3 or 4 are arranged offset from each other. This offset ensures that the first connecting wire 8 of the high-side circuit breaker 3 has a short and, for example, straight connection to the second connecting wire 9 of the low-side circuit breaker 4 via the conductor 12.

[0050] This short connection of the connecting wires 8 and 9, according to the state of the art, nevertheless leads to the occurrence of parasitic inductances, which negatively affect the switching behavior of the power switches 3 or 4.

[0051] In the Fig. Figure 4 shows an equivalent circuit diagram of a half-bridge 2. The half-bridge 2, arranged between the potentials HV+ and HV-, has a high-side circuit breaker 3 and a low-side circuit breaker 4.

[0052] In the area of ​​the first connecting wire 8, a first parasitic inductance 13 develops. In the area of ​​the second connecting wire 9, a second parasitic inductance 14 develops. The areas referred to here are both the connecting wires 8 and 9 as well as the conductor track. The output for the voltage of a phase 5 (phase-U) is located approximately midway between these parasitic inductances 13 and 14. As already explained, the formation of the parasitic inductances 13 and 14 negatively affects the operation of the power switches 3 and 4, particularly at high switching frequencies, which can, for example, be in the range between 20 kHz and 400 kHz.

[0053] In the Fig. Figure 4 also shows a DC link capacitor 15 arranged between the potentials HV+ and HV- and the usual freewheeling diodes.

[0054] In the Fig. Figure 5 shows a side view of an embodiment of the arrangement according to the invention. The power switches 3 and 4 of a half-bridge 2 are, for example, implemented in a TO220 or TO247 package. For electrical connection of the power switches 3 and 4 to corresponding traces on the printed circuit board 6, the power switches 3 and 4 each have three pins 10, for example, for the emitter, collector, and gate connections of the respective power switch 3 or 4.

[0055] As already known, one of the three pins 10 of the high-side circuit breaker 3 is the first connecting wire 8, while one pin of the low-side circuit breaker 4 is the second connecting wire 9.

[0056] In contrast to the prior art, the first connecting wire 8 and the second connecting wire 9 are bent at a defined second distance from the component housing, this second distance being greater than the defined first distance from the component housing at which the remaining pins 10 are bent. This bending of the pins 10, as well as the connecting wires 8 and 9, is performed at an angle of, for example, 90 degrees. Variations of this bending angle other than 90 degrees, or a division of the bend into two angles of, for example, 45 degrees, are possible.

[0057] This design of the bends of pins 10 and connecting wires 8 and 9 makes it possible to arrange the connecting wires 8 and 9 in a common hole in the circuit board 6 and to solder them together with a conductor trace or a solder pad.

[0058] Furthermore, the connecting wires 8 and 9 can, for example, be soldered together in an area where they run parallel to each other.

[0059] This arrangement of the connecting wires 8 and 9 in a common bore, designed accordingly in their diameter, leads to a shortening of the area between the circuit breakers 3 and 4 and thus to a reduction in the formation of the parasitic inductances 13 and 14.

[0060] In this way, higher switching frequencies are possible compared to the state of the art when using the same components for the power switches 3 and 4, without increasing the switching energy loss or switching power loss and thus the heat generation through the power switches 3 and 4 within a half-bridge 2 of an inverter.

[0061] Such a common bore, in which the connecting wires 8 and 9 are arranged, can also be designed as a through-hole.

[0062] Also in the arrangement according to the invention Fig. 5 The horizontally arranged circuit breakers 3 and 4 can be connected to a heat sink 7 in a known manner to dissipate the heat generated in the circuit breakers 3 and 4.

[0063] For electrical insulation and to improve heat conduction between the circuit breakers 3 and 4 and the heat sink 7, a thermally conductive material 11 can also be arranged in this design.

[0064] The Fig. Figure 6 shows the circuit breakers 3 and 4 of a half-bridge 2 in an arrangement according to Fig. 5 in a perspective view without a circuit board. 6. For a better understanding of the invention, the following are shown in the Fig. Figure 6 shows only the high-side circuit breaker 3 with its first connecting wire 8 and the low-side circuit breaker 4 with its second connecting wire 9, without the circuit board 6. The different bending distances between pins 10 and connecting wires 8 and 9 are visible. Also visible is a section of connecting wires 8 and 9 where they run parallel to each other and where they can be soldered together and inserted into a common hole on the circuit board 6.

[0065] The Fig. Figure 7 shows an arrangement of two semiconductor power switches 3 and 4 according to the invention on a section of a printed circuit board 6 in a practical implementation.

[0066] For better understanding of the explanations, two circuit breakers 3 and 4 belonging to a half-bridge 2 are arranged or soldered onto a section of a printed circuit board 6. In practice, the circuit breakers 3 and 4 are in the same configuration as in the Fig. 7 as shown, for example on a larger circuit board 6 implementing the functionalities of an inverter 1, such as an inverter circuit board.

[0067] In the left part of the Fig. Figure 7 shows a view of the component side of the circuit board 6, while the right part of the Fig. Figure 7 shows a view of the side of the conductor traces of the circuit board 6. In the right part of the Fig. 7 shows the low-side power transistor 4 by means of a dash-dash line, since it is hidden by the circuit board 6.

[0068] The connecting wires 8 and 9 can be arranged and soldered in a common hole or via in the printed circuit board 6 due to the larger second distance of the bending point from the component itself, thus greatly reducing the formation of parasitic inductances. Not shown in the Fig. 7 is the connection of the connecting wires 8 and 9 with the output for the associated phase 5.

[0069] The remaining pins 10 of each power switch 3 or 4 are bent in a manner known from the prior art, wherein the first distance of these bends from the component itself is smaller than the second distance between the bends of the connecting wires 8 and 9. These bends are also advantageously made at an angle of 90 degrees.

[0070] In this arrangement according to the invention, the circuit breakers 3 or 4 are also arranged offset from each other. This offset allows the first connecting wire 8 of the high-side circuit breaker 3 and the second connecting wire 9 of the low-side circuit breaker 4 to be arranged in a common bore, while no changes to the design of the printed circuit board 6 are necessary for the remaining pins 10 in this arrangement according to the invention. Reference symbol list 1 Inverter 2 Half-bridge 3 High-side circuit breakers 4 low-side power switches, low-side power transistor 5 Phase (U, V, W) 6 circuit board 7 heat sinks 8 first connecting wire 9 second connecting wire 10-pin (connectors) 11 Thermally conductive material (TIM) 12 ladder 13 first parasitic inductance 14 second parasitic inductance 15 Intermediate circuit capacitor

Claims

[1] Half-bridge (2) in an inverter (1) in which a high-side circuit breaker (3) and a low-side circuit breaker (4) are arranged, characterized by , that a first connecting wire (8) of the high-side circuit breaker (3) and a second connecting wire (9) of the low-side circuit breaker (4) are arranged in direct connection between the connecting wires (8, 9) and in a common bore in a printed circuit board (6) electrically connected to conductor traces (12) on the printed circuit board (6) and that pins (10) of the circuit breakers (3, 4) have a bend at a first distance from the circuit breaker (3, 4) and the connecting wires (8, 9) have a bend at a second distance from the circuit breaker (3, 4), the second distance being greater than the first distance. [2] Half-bridge (2) according to claim 1, characterized by, that the first connecting wire (8) is an emitter terminal or a source terminal of the high-side circuit breaker (3) and the second connecting wire (9) is a collector terminal or a drain terminal of the low-side circuit breaker (4). [3] Half-bridge (2) according to one of claims 1 or 2, characterized by , that the bends of the pins (10) and the connecting wires (8, 9) are arranged in the same direction and at an angle of 90 degrees. [4] Method for reducing parasitic inductances in a half-bridge (2) of an inverter (1) wherein a high-side power switch (3) and a low-side power switch (4) are provided in a half-bridge (2), characterized by, that a first connecting wire (8) of the high-side circuit breaker (3) and a second connecting wire (9) of the low-side circuit breaker (4) are provided in direct connection between the connecting wires (8, 9) and in a common hole in a printed circuit board (6) electrically connected with conductor traces on the printed circuit board (6), and that pins (10) of the circuit breakers (3, 4) are provided with a bend at a first distance from the circuit breaker (3, 4) and the connecting wires (8, 9) are provided with a bend at a second distance from the circuit breaker (3, 4), the second distance being greater than the first distance. [5] Method according to claim 4, characterized by , that the first connecting wire (8) is an emitter terminal or a source terminal of the high-side circuit breaker (3) and the second connecting wire (9) is a collector terminal or a drain terminal of the low-side circuit breaker (4). [6] Method according to one of claims 4 or 5, characterized by , that the bends of the pins (10) and the connecting wires (8, 9) are produced in the same direction and at an angle of 90 degrees. [7] Method according to any one of claims 4 to 6, characterized by , that the connecting wires (8, 9) are electrically connected to each other and to conductors on the circuit board (6) by means of a soldering process.

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