Low impedance buffer capacitor arrangement in a converter module

Abstract

The invention relates to an AC drive for driving an electric motor. The AC drive comprises a three-phase diode bridge, an inverter and a buffer board with multilayer printed circuit board elements, wherein the power channels in each layer of each element are connected to only one potential DC- or DC+, each element comprises two capacitors of opposite polarity, wherein each element comprises two C-shaped busbars, and wherein the C-shaped busbars of two adjacent elements are placed in close proximity to each other.

Description

Technical Field

[0001] This invention relates to an AC driver for driving an electric motor, or, for example, in a gate converter and / or power converter. The AC driver includes a three-phase diode bridge, an inverter, and a buffer board with multiple layers of printed circuit board elements, wherein a power path in each layer of each element is connected to only one potential DC- or DC+, each element includes two capacitors of opposite polarity, each element includes two C-shaped busbars, and the C-shaped busbars of two adjacent elements are placed close to each other. Background Technology

[0002] AC drives are prone to buffered voltage at their IGBTs. During this period, the voltage within the drive can rise significantly when the IGBT is turned off. This voltage rise is caused by the inductance between the IGBT and the DC link capacitor and / or the drive's busbar. The voltage rise can lead to problematic drive performance and / or damage to drive components. Custom-designed buffer capacitor solutions that could help mitigate this problem are often excluded due to cost considerations, especially as drive size and manufacturing costs have decreased.

[0003] Alternatively, if low-cost capacitors are used to overcome this problem, a matching custom busbar is required, which in turn increases the overall cost of the driver. Furthermore, standard capacitors have fixed specifications and are typically too large for the AC driver described here. Therefore, multiple smaller capacitors must be used in parallel, which degrades the AC driver's performance due to the increased inductance of the custom busbar solution. Summary of the Invention

[0004] The object of this invention is to provide an improved AC driver that overcomes these problems. This object is achieved by the AC driver according to claim 1. Preferred embodiments of the invention are the subject of the dependent claims.

[0005] According to the present invention, an AC driver for driving an electric motor is provided. The AC driver includes a three-phase diode bridge, an inverter, and a buffer board having multilayer printed circuit board components, wherein the power path in each layer of each component is connected to only one potential DC- or DC+, and each component includes two capacitors of opposite polarity. Each component includes two C-shaped busbars, wherein the C-shaped busbars of two adjacent components are placed close to each other. The C-shaped busbars are not limited to a C-shape, but can be any shape, such as an I-shape or an L-shape.

[0006] Multilayer printed circuit board components can be understood as including busbars. Alternatively, busbars can be considered as components separate from the multilayer printed circuit board components. Close proximity of busbars can be understood as these busbars being separated from only one component (such as an insulator) while being in close contact with said component.

[0007] This invention utilizes a multilayer PCB with buffer capacitors to provide a low-inductance path for the IGBT or other active components of the driver. A low-inductance design is employed to implement the path from the PCBA to the IGBT, where the DC+ and DC- buses are mechanically connected to each other as closely as possible. Furthermore, there is a large, flat area between them. This is facilitated by the large, flat middle section of the C-shaped busbars.

[0008] The driver described here provides a solution that forms a very low inductance circuit for the buffer capacitor, thereby reducing the buffer voltage of the IGBT. Compared to the known alternative solutions mentioned above, the driver described here offers a more cost-effective solution. Furthermore, the driver's manufacturing quality is improved because it can be easily assembled in an automated assembly process.

[0009] In a preferred embodiment of the invention, an insulator is provided between the C-shaped busbars of two adjacent elements, with the C-shaped busbars spaced apart from each other by the thickness of the insulator. The insulator may be aligned parallel to the middle section of the C-shaped busbar. The insulator may be glued to or otherwise attached to the C-shaped busbar. Therefore, the distance between the two busbars may be slightly greater than the thickness of the insulator.

[0010] In another preferred embodiment of the invention, the middle section of adjacent C-shaped busbars is in close contact with the insulator. The middle section may be glued to or otherwise attached to the insulator.

[0011] In another preferred embodiment of the invention, five multilayer printed circuit board elements are provided. The number of multilayer printed circuit board elements can be freely selected to provide the required characteristics to the driver. These multilayer printed circuit board elements can be aligned with each other.

[0012] In another preferred embodiment of the invention, the multilayer printed circuit board element includes layers alternately connected to DC+ and DC-, wherein the layers are separated from each other by air gaps and / or PCB core material and / or prepreg.

[0013] In another preferred embodiment of the invention, the multilayer printed circuit board element includes a top layer connected to DC-, a second layer connected to DC+, a third layer connected to DC-, and a bottom layer connected to DC+. Accordingly, two sets of layers may exist, one set connected to DC+ and the other set connected to DC-. Layers in one set may not overlap their entire surface. The non-overlapping areas of the layers can be used to connect the layer to DC+ or DC-. These layers can be separated from each other by air gaps and / or PCB core material and / or prepreg.

[0014] In another preferred embodiment of the invention, the C-shaped busbar is connected to the element via screws and / or washers (preferably SMD washers) and / or nuts and / or through holes. The nut may be a hexagonal nut.

[0015] In another preferred embodiment of the invention, the buffer plate is directly mounted to the DC+ and DC- terminals of the IGBT of the driver.

[0016] In another preferred embodiment of the invention, the C-shaped busbar is disposed on one side of the buffer plate, and the capacitor is disposed on the opposite side of the buffer plate.

[0017] In another preferred embodiment, the multilayer printed circuit board components are mounted behind the high-current busbar with sufficient clearance to prevent voltage bulging.

[0018] In another preferred embodiment, the multilayer printed circuit board element is mounted behind a high-current busbar and includes a low-impedance path for current to flow between the capacitor and the high-current busbar. Attached Figure Description

[0019] Further details and advantages of the invention will be described with reference to the accompanying drawings. The drawings show:

[0020] Figure 1 Circuit diagram of AC driver;

[0021] Figure 2 : This shows the circuit diagram of the buffer capacitor;

[0022] Figure 3 Detailed view of the connection between the C-shaped busbar and the multilayer printed circuit board components;

[0023] Figure 4 Detailed view of the insulator between the C-shaped busbars;

[0024] Figure 5 Detailed view of the buffer plate;

[0025] Figure 6 : Circuit diagram of the buffer board; and

[0026] Figure 7 View of multilayer printed circuit board components behind a high-current busbar. Detailed Implementation

[0027] Figure 1 An embodiment of a circuit diagram of an AC driver according to the present invention is shown. This driver is configured to drive an electric motor, particularly a three-phase electric motor 10. The driver includes a three-phase diode bridge 7, an inverter 8, and a snubber board 9 having multilayer printed circuit board components 20, 21. (The remaining text will be omitted.) Figure 3 and Figure 4 The multilayer printed circuit board components 20 and 21 are shown in more detail. The three-phase diode bridge 7 may be an active front end, and the inverter 8 may be a three-phase IGBT inverter.

[0028] In each layer of each multilayer printed circuit board element 20, 21, the power lane is connected to only one potential DC-1 or DC+2, and each element 20, 21 includes two capacitors C1-C10 with opposite polarities.

[0029] exist Figure 1 In this embodiment, only two pairs of capacitors C1-C4 are shown, wherein the pair of first capacitor C1 and second capacitor C2, and the pair of third capacitor C3 and fourth capacitor C4, have switching polarities relative to each other. The capacitors C1-C4 of the buffer plate 9 serve as snubber capacitors for the driver.

[0030] Figure 2 A circuit diagram with a buffer capacitor is shown. A buffer capacitor is a capacitor connected to a high-current switching node to reduce the parasitic inductance of a wire. Parasitic inductance can cause a large surge when the circuit is turned off (i.e., when the current is interrupted). When such a surge exceeds the component's rating, the component may be damaged. To reduce the parasitic inductance of the wire, it is necessary to… Figure 2 A capacitor is connected near the area indicated by reference numeral 100 in the attached figure.

[0031] Figure 3 This is a detailed view of the connection between the C-shaped busbar 19 and the multilayer printed circuit board element 21, as shown in the cup layer build-up. As will be shown in the figure below, each multilayer printed circuit board element 20, 21 can be positioned between two separate busbars 18, 19. Each of these two separate busbars 18, 19 is connected to DC- or DC+.

[0032] Despite Figure 3Only one multilayer printed circuit board element 21 is shown, but the rest of the multilayer printed circuit board elements 20, 21 may have a similar or consistent architecture. Reference numeral 13 indicates the top layer of element 21 connected to DC-. Reference numeral 14 indicates the second layer connected to DC+. Reference numeral 15 indicates the third layer connected to DC-. Reference numeral 16 indicates the bottom layer connected to DC+. Screw 12 may be configured to electrically connect the top layer 13 or the bottom layer 16 to the busbar 19.

[0033] Electrical connections between every other layer can be provided by means of through-hole 17 and correspondingly placed conductors. To facilitate electrical connections between every other layer, extensions of adjacent layers (such as top layer 13 and second layer 14), particularly extensions along the longitudinal direction of buffer plate 9, can be selected such that they do not overlap over their entire length and / or surface area.

[0034] exist Figure 3 In this embodiment, the top layer 13 and the third layer 15 extend all the way to bus 19, while the bottom layer 16 and the second layer 14 are shorter and do not extend all the way to bus 19. Therefore, the second layer 14 and the bottom layer 16 do not interfere with the electrical connection between the top layer 13, the third layer 15, and one of the bus bars 19. The bottom layer 16 and the second layer 14 may extend all the way to another bus bar 18 opposite to bus bar 19, wherein... Figure 3 The other busbar 18 is not shown in the diagram.

[0035] exist Figure 3 In this embodiment, the multilayer printed circuit board element 21 includes a top layer 13 connected to DC- (i.e., busbar 19). A second layer 14 is connected to DC+, i.e., connected to the layer opposite to busbar 19 and... Figure 3 Busbar 18 is not shown. The third layer 15 is connected to DC- again via via 17 and the corresponding conductive portion, just like the top layer 13, and thus to busbar 19. The bottom layer 16 is connected to DC+ again.

[0036] If more than four layers are used in multilayer printed circuit board components 20 and 21, additional layers can also be connected to alternating busbars 18 and 19. Accordingly, two sets of layers can exist, one connected to DC+2 and the other connected to DC-1. The layers in one set do not need to overlap on the entire surface of these layers. The non-overlapping areas of these layers can be used to connect the layers to DC+2 or DC-1.

[0037] The bottom layer 16, or more generally the bottom layer of the multilayer printed circuit board elements 20, 21, may extend at least in a direction perpendicular to busbars 18, 19. Additionally or alternatively, the upper layers may extend further in said direction than the lower layers of the multilayer printed circuit board elements 20, 21. From the top layer 13 to the bottom layer 16, each of a pair of adjacent layers may have equal or similar lengths in a direction perpendicular to busbars 18, 19. In the direction perpendicular to busbars 18, 19, the top pair of layers may have the maximum length, and the bottom pair of layers may have the minimum length. In the direction perpendicular to busbars 18, 19 and relative to the top and bottom pairs of layers, the middle pair of layers may have intermediate lengths.

[0038] The minutely offset geometry of the layers of multilayer printed circuit board components 20 and 21 makes it easy to provide alternating connections to DC+ and DC-, or more precisely, to the layers of the corresponding busbars 18 and 19. According to Figure 3 In some embodiments, the layers can be separated from each other by air gaps. Alternatively or additionally, PCB core material and / or prepreg can be disposed between the layers.

[0039] Busbar 19 and / or multilayer printed circuit board element 21 may include circular or partially circular holes or recesses. The holes and / or recesses may at least partially overlap, for example, to provide space for tools and / or components.

[0040] Figure 4 This is a detailed view of the insulator 22 between the C-shaped busbars 18 and 19. Although C-shaped busbars 18 and 19 are shown here, busbars 18 and 19 of any shape can be combined with the corresponding insulator 22. The two busbars 18 and 19 partially enclose their respective multilayer printed circuit board elements 20 and 21 in a direction perpendicular to the surfaces of the multilayer printed circuit board elements 20 and 21. The insulator 22 can be oriented in a direction perpendicular to the surfaces of the multilayer printed circuit board elements 20 and 21. The surfaces of the multilayer printed circuit board elements 20 and 21 can be understood as the flat sides of the elements 20 and 21.

[0041] The insulator 22 may have the same or similar length as the two busbars 18, 19. The vertical direction of the insulator 22 may correspond to the direction of the screw 12. The insulator 22 may extend further in its vertical direction than the screw 12 and / or the two busbars 18, 19.

[0042] Each of the multilayer printed circuit board components 20, 21 may include two C-shaped busbars 18, 19 or any other suitable shape of busbar. The two busbars 18, 19 of two adjacent components 20, 21 may be placed close to each other and may preferably be arranged symmetrically to each other.

[0043] Two adjacent C-shaped busbars 18, 19 are spaced apart by the thickness of insulator 22. Insulator 22 may be aligned parallel to the middle section of the C-shaped busbars 18, 19. Both insulator 22 and the middle section of the C-shaped busbars may be planar. Insulator 22 may be glued to or otherwise attached to the C-shaped busbars 18, 19.

[0044] exist Figure 4 In one embodiment, only the middle section of adjacent C-shaped busbars 18 and 19 is in close contact with the insulator 22. The middle section of the C-shaped busbars 18 and 19 may extend in the vertical direction of the busbars 18 and 19, for example, extending halfway to the insulator 22.

[0045] C-shaped busbars 18 and 19 are connected to components 20 and 21 via screws 12. Additional or alternative washers may be provided for connecting components 20 and 21 to busbars 18 and 19. For example, SMD washers may be provided between the parallel end portions of the C-shaped busbars 18 and 19. Additionally or alternatively, one or more nuts, such as hexagonal nuts, may be provided. The nuts may be screwed onto screws 12 such that the parallel end portions of busbars 18 and 19 are compressed by the screw head on one side and the nut on the other. Alternatively, only one end portion of the C-shaped busbars 18 and 19 may be positioned between the screw head and the nut.

[0046] Through-holes 17 can be provided in the layers of multilayer printed circuit board elements 20 and 21 to facilitate electrical connection between the alternating layers of the multilayer printed circuit board elements 20 and 21.

[0047] Figure 5 This is a detailed view of buffer board 9. The PCBA of this buffer board can contain ten 750nF capacitors C1-C10 connected in parallel across four PWB layers. The power path (plane) in each layer is connected to only one potential, DC-1 or DC+2. In the example described here, and as... Figure 3 As shown, the top layer 13 can be connected to DC-1, the second layer 14 to DC+2, the third layer 15 to DC-1, and the bottom layer 16 to DC+2. The buffer plate 9 can be directly mounted to the DC+ and DC- terminals of the IGBT. The polarity of every other capacitor is reversed to reduce mutual inductance. The C-shaped busbars 18 and 19 are placed as close to each other as possible. Busbars 18 and 19 can be connected to the PWB with screws via SMD washers. An insulator 22 is placed between busbars 19 and 19, as shown. Figure 4 As shown.

[0048] Figure 5The embodiment illustrates five multilayer printed circuit board elements 20, 21. The number of multilayer printed circuit board elements 20, 21 can vary depending on the total required capacitance of the driver.

[0049] C-shaped busbars 18 and 19 are located on one side of the buffer plate 9, and capacitors C1-C10 are located on the opposite side of the buffer plate 9. The buffer plate 9 can be directly mounted to the DC+ and DC- terminals of the driver's IGBT.

[0050] Figure 6 It shows Figure 5 The circuit diagram of the buffer board. Each pair of capacitors C1-C10 is part of multilayer printed circuit board components 20 and 21.

[0051] Figure 7 Multilayer printed circuit board (PCB) components 20 and 21 are shown behind the high-current busbar 23. The height of the PCB components 20 and 21 is kept low to ensure sufficient free space between the component screws 12, capacitors C1-C10, and C-shaped busbars 18 and 19 of the PCB components 20 and 21 and the high-current busbar 23. A minimum distance can be defined to avoid high-voltage buckling between the component screws 12, capacitors C1-C10, and C-shaped busbars 18 and 19 of the PCB components 20 and 21 and the high-current busbar 23. Capacitors C1-C10 can have a low height to support the gap between capacitors C1-C10 and the high-current busbar 23.

[0052] The low height or profile of the multilayer printed circuit board components 20 and 21, which include component screws 12, capacitors C1-C10, and C-shaped busbars 18 and 19, allows the multilayer printed circuit board components 20 and 21 to be positioned behind the high-current busbar 23.

[0053] Compared to a design with one area containing a high-current busbar 23 and another containing multilayer printed circuit board components 20, 21, placing the multilayer printed circuit board components 20, 21 behind the high-current busbar 23 requires less space inside the driver. The very short distance between the multilayer printed circuit board components 20, 21 and the high-current busbar 23 makes the buffer capacitors C1-C10 very effective due to the low-impedance path for conducting current.

Claims

1. An AC driver for driving an electric motor, the AC driver comprising a three-phase diode bridge (7), an inverter (8), and a buffer board (9) having multilayer printed circuit board elements (20, 21), wherein a power path in each layer of each element (20, 21) is connected to only one potential DC- or DC+ (1, 2), each element (20, 21) includes two capacitors (C1-C10) of opposite polarity, wherein each element (20, 21) includes two C-shaped busbars (18, 19), and wherein the C-shaped busbars (18, 19) of two adjacent elements (20, 21) are placed close to each other, wherein, The multilayer printed circuit board elements (20, 21) include layers that are alternately connected to DC+ (1) and DC- (2).

2. The AC driver according to claim 1, characterized in that, An insulator (22) is provided between the C-shaped busbars (18, 19) of two adjacent elements (20, 21), and the C-shaped busbars (18, 19) are spaced apart from each other by the thickness of the insulator (22).

3. The AC driver according to claim 2, characterized in that, The middle section of the adjacent C-shaped busbars (18, 19) is in close contact with the insulator (22).

4. The AC driver according to any one of claims 1 to 3, characterized in that, Set up 5 multilayer printed circuit board components (20, 21).

5. The AC driver according to any one of claims 1 to 3, characterized in that, The layers are separated from each other by air gaps and / or PCB core material and / or prepreg.

6. The AC driver according to any one of claims 1 to 3, characterized in that, The multilayer printed circuit board components (20, 21) include a top layer (13) connected to DC- (2), a second layer (14) connected to DC+ (1), a third layer (15) connected to DC- (2), and a bottom layer (16) connected to DC+ (1).

7. The AC driver according to any one of claims 1 to 3, characterized in that, The C-shaped busbars (18, 19) are connected to the elements (20, 21) via screws (12) and / or washers and / or nuts and / or through holes (17).

8. The AC driver according to any one of claims 1 to 3, characterized in that, The buffer plate (9) is directly mounted to the DC+ and DC- terminals of the IGBT of the driver.

9. The AC driver according to any one of claims 1 to 3, characterized in that, The C-shaped busbars (18, 19) are disposed on one side of the buffer plate (9), and the capacitors (C1-C10) are disposed on the opposite side of the buffer plate (9).

10. The AC driver according to any one of claims 1 to 3, characterized in that, The multilayer printed circuit board components (20, 21) are mounted behind the high current busbar (23) with sufficient clearance to avoid voltage bulging.

11. The AC driver according to any one of claims 1 to 3, characterized in that, The multilayer printed circuit board elements (20, 21) are mounted behind the high-current busbar (23) and include a low-impedance path for current to flow between the capacitors (C1-C10) and the high-current busbar (23).

12. The AC driver according to claim 7, characterized in that, The gasket is an SMD gasket.

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