PCB busbar and motor controller

Abstract

This invention provides a PCB busbar and a motor controller. The PCB busbar includes: a windowed structure with metal windows on the top and bottom layers for AC / DC traces, used for externally soldering metal sheets for current amplification and heat dissipation, and for leading out AC / DC terminals; multiple power switching devices evenly arranged on the top layer of the busbar, including three sets of single-phase bridge structures, each consisting of power switching devices connected in parallel in the upper and lower bridge arms; AC connection points formed by connecting the power switching devices connected in parallel between the upper and lower bridge arms of each single-phase bridge structure; and DC capacitors located in the middle of the power switching devices in the upper and lower bridge arms, connected in parallel with the power switching devices of each single-phase bridge. The windowed structure on the top and bottom layers allows for the external soldering of copper sheets of different thicknesses, achieving the desired current carrying capacity and heat dissipation effect. The multi-layer PCB design reduces stray inductance in the circuit, and the symmetrical arrangement of electronic components achieves excellent current sharing.

Description

Technical Field

[0001] This invention relates to the field of motor controller technology, specifically to a PCB busbar and a motor controller. Background Technology

[0002] Motor controllers mainly consist of power modules, power drive modules, and central control modules. Power electronic devices are the core components of motor controllers, determining the performance and cost of the motor control system. In existing technologies, SiC MOSFETs are a key research focus in motor controller design due to their high temperature resistance, low loss, and suitability for high-frequency operation. Parallel connection of SiC MOSFETs can achieve controllers with small to medium power ratings; however, the common approach of using high-purity oxygen-free copper to create a special composite structure as the busbar is unsuitable for the mounting and soldering of discrete SiC MOSFET devices. Furthermore, SiC devices have high switching speeds and are sensitive to stray circuit parameters. The large stray inductance causes SiC MOSFETs to experience significant voltage overshoot during high-speed switching, leading to switching oscillations, additional power losses, and a significantly increased risk of device failure, thus hindering further improvements in the efficiency, switching frequency, and reliability of the motor controller.

[0003] In existing technologies, the power drive circuits of discrete SiC MOSFET devices mainly employ high-power drive circuit control methods, utilizing power modules combined with stacked busbars made of high-purity oxygen-free copper. This results in high cost and price for medium-power drive circuits. Furthermore, due to the inherent loop inductance of the SiC MOSFET module and limitations imposed by module packaging, the stray inductance in the loop design is relatively large. Uneven current leads to unequal losses and current and voltage stresses among parallel devices, causing a bottleneck effect that forces the entire system to operate at a derating rate, significantly impacting the efficiency and power consumption performance of the inverter in the motor controller. In contrast, existing discrete device controllers based on PCB busbars typically have large busbar areas to handle maximum current, resulting in low power density and high stray inductance. Moreover, the PCB substrate causes significant heat generation during high current flow, making these designs only suitable for low-power controllers. Summary of the Invention

[0004] In view of this, the present invention provides a PCB busbar and a motor controller to solve the problem that the busbar cannot simultaneously achieve the functions of improving heat dissipation, reducing stray inductance, balancing current and reducing power density.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] In a first aspect, embodiments of the present invention provide a PCB busbar, comprising:

[0007] The window structure consists of multiple vertical PCB stacks. The top and bottom layers of the busbar have metal windows for DC and AC traces, which are used for external soldering of metal sheets for current amplification and heat dissipation and for leading out AC and DC terminals.

[0008] Multiple power switching devices are evenly arranged on the top layer of the busbar. The multiple power switching devices form a three-phase full-bridge structure. The three-phase full-bridge structure includes three sets of single-phase bridge structures. The single-phase bridge structure includes power switching devices connected in parallel in the upper bridge arm and power switching devices connected in parallel in the lower bridge arm.

[0009] The AC connection point is formed by power switching devices connected in parallel between the upper and lower bridge arms of each single-phase bridge structure. The AC connection point is the midpoint between the upper and lower bridge arms and is used to externally weld copper columns to connect the motor.

[0010] The DC capacitor is located in the middle of the power switching devices in the upper and lower bridge arms, and is connected in parallel with the power switching devices of each single-phase bridge.

[0011] The PCB busbar provided in this embodiment of the invention increases current carrying capacity and heat dissipation of the board through the window structure of the top and bottom layers. The stray inductance in the circuit is reduced through the multi-layer PCB design, and the symmetrically arranged electronic components achieve a good current sharing effect, making up for the shortcomings of commonly used PCB busbars which can only be used in low-power applications.

[0012] Optionally, the power switching device is a SiC MOSFET.

[0013] SiC MOSFETs are characterized by high temperature resistance, low loss, and suitability for high-frequency operation, making them the best choice among existing devices for power switching in this busbar structure design.

[0014] Optionally, the PCB busbar is circular in shape.

[0015] Making the PCB busbar circular not only better ensures the symmetry of components and the current sharing effect, but also maximizes the power density of the circular busbar while carrying the largest possible current. At the same time, this compact design also saves on raw material costs.

[0016] Optionally, the metal window is a copper window, and the metal sheet is an irregularly shaped copper sheet of different thicknesses.

[0017] Optionally, the current carried by the busbar is proportional to the thickness of the copper sheet.

[0018] The copper window design of the PCB busbar provided in this embodiment of the invention allows for the selection of copper sheets of appropriate thickness according to the current carrying requirements, ensuring current flow while achieving better heat dissipation.

[0019] Optionally, each PCB stack includes a positive bus layer and a negative bus layer, wherein the positive bus layer and the negative bus layer are adjacent to each other in adjacent layers, and each PCB stack forms a loop.

[0020] The current flowing through the positive and negative bus layers in each PCB stack is equal in magnitude and opposite in direction, which reduces the stray inductance of the bus circuit and prevents the power switching devices from experiencing large voltage overshoots during high-speed switching, thereby reducing power loss and improving system efficiency.

[0021] Optionally, there are two DC input terminals at the center of the busbar, which are respectively connected to the positive busbar layer and the negative busbar layer.

[0022] Placing the DC input terminal at the exact center of the busbar helps to achieve symmetrical current flow to each parallel device, ensuring current sharing.

[0023] Optionally, the busbar consists of eight vertical PCB stacks, forming four circuits in total.

[0024] In practical applications, after multiple tests and verifications, the four-circuit busbar composed of eight PCBs is the best solution in terms of both cost and the effect of reducing stray inductance of the circuit.

[0025] Optionally, in each single-phase bridge structure, the drains of the power switching devices connected in parallel in the upper arms are all connected to the positive bus layer, the power sources of the power switching devices connected in parallel in the lower arms are all connected to the negative bus layer, and the power sources of the power switching devices connected in parallel in the upper arms are connected to the drains of the power switching devices connected in parallel in the lower arms.

[0026] By implementing the above methods, the distance and impedance from the AC connection point to the parallel power switching devices in the upper and lower bridge arms can be made equal. Furthermore, by establishing electrical connections through each set of stacked busbars, current flows from the positive busbar layer through capacitors to the negative busbar layer, forming a minimal current loop and reducing the inductance in the loop. Therefore, through the above connection relationships, the current has a minimum loop, ultimately resulting in a smaller inductance on the loop.

[0027] In a second aspect, embodiments of the present invention provide a motor controller, including:

[0028] A power module, including the PCB busbar as described in any one of the first aspects;

[0029] The drive module is used to provide power to the motor;

[0030] The control module is used to control the power module and the drive module to make the motor work.

[0031] The electronic controller provided in this embodiment of the invention assists the motor to work efficiently and stably through a power module having the PCB busbar described in any embodiment of the first aspect. Attached Figure Description

[0032] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0033] Figure 1 This is a schematic diagram of a PCB busbar structure provided in an embodiment of the present invention;

[0034] Figure 2A This is a schematic diagram of an eight-layer PCB stack in a specific embodiment of a PCB busbar provided by the present invention;

[0035] Figure 2B This invention provides a specific embodiment of a PCB busbar, showing the wiring method of two conductors with opposite current directions.

[0036] Figure 3 A connection diagram of two equivalent conductors in the positive and negative busbar layers in a specific embodiment of a PCB busbar provided by the present invention;

[0037] Figure 4A This is a schematic diagram of the top copper window structure of a PCB busbar provided in an embodiment of the present invention;

[0038] Figure 4B This is a schematic diagram of the bottom copper window structure of a PCB busbar provided in an embodiment of the present invention;

[0039] Figure 5 A diagram showing the location distribution of multiple electronic components on a circular PCB board;

[0040] Figure 6 A circuit diagram of the U-phase bridge arm in a specific embodiment of a PCB busbar provided by the present invention;

[0041] Figure 7 This is a schematic diagram of the actual PCB traces in a specific embodiment of a PCB busbar provided by the present invention;

[0042] Figure 8 This is a schematic diagram of the structure of a motor controller provided in an embodiment of the present invention. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0045] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can also refer to the internal connection of two components; and they can refer to a wireless connection or a wired connection. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0046] The technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0047] Example 1

[0048] This invention provides a PCB busbar, such as Figure 1 As shown, it includes:

[0049] The windowed structure consists of multiple vertically stacked PCB layers. The top and bottom layers of the busbar have metal windows for DC and AC traces, used for externally soldering metal sheets for current amplification and heat dissipation, and for leading out AC and DC terminals. The windows on the top and bottom layers are for soldering copper sheets, allowing the AC and DC current to carry greater current while enhancing heat dissipation. Without externally soldered copper sheets, the PCB board with a copper thickness of 1 oz (equivalent to 0.14 mm) and a trace width of 1 mm can only carry a maximum current of 1 A. This embodiment of the invention, by using windows and externally soldering copper sheets, can increase the current carrying capacity to more than three times the original current under the same PCB board specifications.

[0050] Specifically, in one embodiment, each PCB stack includes a positive bus layer and a negative bus layer, with the positive and negative bus layers adjacent to each other, forming a loop in each PCB stack. The currents flowing through the positive and negative bus layers in each PCB stack are equal in magnitude and opposite in direction. Utilizing the principle that opposite currents in the vertical direction result in the smallest loop area with the least parasitic inductance, the stray inductance of the bus circuit is reduced, preventing power switching devices from experiencing large voltage overshoots during high-speed switching, thereby reducing power loss and improving system efficiency.

[0051] Specifically, in one embodiment, the busbar consists of eight vertically stacked PCB layers, forming four circuits. For example... Figure 2A The diagram shown is a schematic of an eight-layer PCB stack-up structure. Figure 2B This refers to the wiring method for two conductors with opposite current directions (the upper and lower positive and negative busbars can be regarded as two conductors). In practical applications, after multiple tests and verifications, the four-loop busbar composed of eight PCBs is the best solution in terms of both cost and the effect of reducing stray inductance of the loop, achieving a stray inductance of less than 20nH.

[0052] For example, if the upper and lower positive and negative busbars are considered as two conductors, their equivalent circuit diagram is as follows: Figure 3 As shown, the calculation process for its stray inductance is as follows:

[0053] The voltages across the two conductors are as follows:

[0054]

[0055]

[0056] Where V1 is the voltage across the upper conductor, V2 is the voltage across the lower conductor, I1 is the current flowing through the upper conductor, I2 is the current flowing through the lower conductor, M is the mutual inductance between the two conductors, L1 is the parasitic inductance of the upper conductor, and L2 is the parasitic inductance of the lower conductor, the following formula can be derived:

[0057]

[0058]

[0059] Where s is the differential operator, V is the voltage across the two conductors, and... Figure 3 We know that V = V1 = V2. According to Ohm's law, the total impedance of the conductor is as follows:

[0060]

[0061] When two adjacent conductors are of the same material and thickness, their parasitic inductances should be the same.

[0062] L1=L2=L

[0063] therefore,

[0064]

[0065] Where L represents the parasitic inductance of the two conductors. As shown in the formula, to reduce the total impedance, the mutual inductance must be increased. The mutual inductance M is expressed as:

[0066]

[0067] Where μ0 represents the free permeability, l represents the length of the conductor, and d represents the distance between the two conductors. The formula shows that reducing the distance between the positive and negative poles increases mutual inductance and decreases the total impedance. It can be deduced that in PCB layout, if the current flows in opposite directions between adjacent layers and they are close together, the inductance generated by interlayer electromagnetic induction can be significantly reduced.

[0068] Specifically, in one embodiment, the PCB busbar is circular. For example, the busbar diameter of two parallel devices can be 8cm. With a board thickness of only 2mm, a single layer copper thickness of 4 ounces and a maximum current carrying capacity of 8 layers can be achieved. Making the PCB busbar circular not only better ensures the symmetry of the components and the current sharing effect, but also achieves the highest power density while carrying the largest possible current. At the same time, this compact design also saves on raw material costs.

[0069] Specifically, in one embodiment, the metal window is a copper window, and the metal sheet is an irregularly shaped copper sheet of varying thickness. The current carried by the busbar is proportional to the thickness of the outer soldered copper sheet. For example, as shown... Figure 4A As shown in the diagram, the black areas represent the copper on the top layer, and all of them have windows (the top layer (i.e., the first, third, fifth, and seventh layers) all use the same copper layout, but only the top layer can have windows and externally soldered copper sheets; the black areas on the top layer represent the externally soldered copper sheets). Figure 4BAs shown in the figure, the black parts represent the bottom layer copper, all of which have been opened (the bottom layer (eighth layer), second layer, fourth layer, and sixth layer all use the same copper layout; only the bottom layer can have windows, and the black parts of the bottom layer represent externally soldered copper sheets). The copper windowing allows for the external soldering of irregular copper sheets on both AC and DC traces. The thickness and width of the copper sheets can be flexibly designed to accommodate the required current, overcoming the limitation of conventional PCBs used as busbars, which are limited to low-power applications. The copper windowing design of the PCB busbar provided in this embodiment allows for the selection of copper busbars of appropriate thickness based on current carrying requirements. The externally soldered copper busbars also facilitate heat dissipation, ensuring current flow while achieving better heat dissipation. Tests showed that the highest operating temperature of this PCB busbar under an AC peak current of 120A was 41.4℃.

[0070] Multiple power switching devices are evenly arranged on the top layer of the busbar, forming a three-phase full-bridge structure. This structure includes three sets of single-phase bridge structures, each consisting of power switching devices connected in parallel in both the upper and lower bridge arms. For example... Figure 5 The diagram shows the location distribution of multiple electronic components on a circular PCB board.

[0071] Specifically, in one embodiment, the power switching device is a SiC MOSFET. SiC MOSFETs are characterized by high temperature resistance, low loss, and suitability for high-frequency operation, making them the optimal choice among existing devices for power switching in this busbar structure design.

[0072] The AC connection point is formed by the parallel connection of power switching devices between the upper and lower arms of each single-phase bridge structure. The AC connection point is the midpoint between the upper and lower arms. For example, AC connection points U, V, and W are located at the midpoints of the upper and lower tubes of the corresponding single-phase bridge arms, and are respectively connected to point S of the parallel tube of the upper tube and point D of the parallel tube of the lower tube, with equal distances to the parallel tubes. Figure 6 The circuit diagram shown is for the U-phase bridge arm. The V-phase and W-phase are similar to the U-phase, so they will not be described again here. The distance from the AC connection point and the positive (or negative) terminal of the bus capacitor to each parallel tube is equal, ensuring that the impedance and inductance of the parallel tubes are equal, which is beneficial for current sharing.

[0073] Specifically, in one embodiment, the drains of the power switching devices connected in parallel in the upper arms of each single-phase bridge structure are all connected to the positive bus layer, the power sources of the power switching devices connected in parallel in the lower arms of each single-phase bridge structure are all connected to the negative bus layer, and the power sources of the power switching devices connected in parallel in the upper arms of each single-phase bridge structure are connected to the drains of the power switching devices connected in parallel in the lower arms of each single-phase bridge structure. Figure 7 The diagram shown is a schematic of the actual PCB routing.

[0074] The DC capacitor is located in the middle of the power switching devices in the upper and lower bridge arms, and is connected in parallel with the power switching devices of each single-phase bridge. For example, the DC capacitor is placed as close as possible to the power switching devices and in the middle of the upper and lower tubes of each single-phase bridge arm. This ensures that the distance and impedance from the capacitor commutation point to the parallel switching tubes are equal, achieving the effect of current sharing.

[0075] The PCB busbar provided in this embodiment of the invention increases current carrying capacity and heat dissipation of the board through the window structure of the top and bottom layers. The stray inductance in the circuit is reduced through the multi-layer PCB design, and the symmetrically arranged electronic components achieve a good current sharing effect, making up for the shortcomings of commonly used PCB busbars which can only be used in low-power applications.

[0076] Specifically, in one embodiment, there are two DC input terminals at the very center of the busbar, which are connected to the positive busbar layer and the negative busbar layer, respectively. Placing the DC input terminals at the very center of the busbar helps to achieve symmetrical loops of DC current to each parallel device, ensuring current sharing.

[0077] By implementing the above methods, the distance and impedance from the AC connection point to the parallel power switching devices in the upper and lower bridge arms can be made equal. Furthermore, by establishing electrical connections through each set of stacked busbars, current flows from the positive busbar layer through capacitors to the negative busbar layer, forming a minimal current loop and reducing the inductance in the loop. Therefore, through the above connection relationships, the current has a minimum loop, ultimately resulting in a smaller inductance on the loop.

[0078] Example 2

[0079] This invention provides a motor controller, such as... Figure 8 As shown, it includes:

[0080] The power module includes the PCB busbar of any of Embodiment 1. A detailed description of the PCB busbar has been provided in Embodiment 1 and will not be repeated here.

[0081] The drive module is used to provide power to the motor. Existing technologies are sufficient to fulfill the functions of the drive module; the specific implementation method is not limited.

[0082] The control module is used to control the power module and drive module to make the motor work. Existing technology is sufficient to fulfill the functions of the control module; the specific implementation method is not limited.

[0083] The electronic controller provided in this embodiment of the invention assists the motor to work efficiently and stably through a power module having a PCB busbar in any embodiment of the first aspect.

[0084] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A PCB busbar, characterized in that, include: The window structure consists of multiple vertical PCB stacks. The top and bottom layers of the busbar have metal windows for DC and AC traces, which are used for external soldering of metal sheets for current amplification and heat dissipation and for leading out AC and DC terminals. Multiple power switching devices are evenly arranged on the top layer of the busbar. The multiple power switching devices form a three-phase full-bridge structure. The three-phase full-bridge structure includes three sets of single-phase bridge structures. The single-phase bridge structure includes power switching devices connected in parallel in the upper bridge arm and power switching devices connected in parallel in the lower bridge arm. The AC connection point is formed by power switching devices connected in parallel between the upper and lower bridge arms of each single-phase bridge structure. The AC connection point is the midpoint between the upper and lower bridge arms and is used to externally weld copper columns to connect the motor. A DC capacitor is located in the middle of the power switching devices in the upper and lower bridge arms, and is connected in parallel with the power switching devices of each single-phase bridge. Each PCB stack includes a positive bus layer and a negative bus layer, which are adjacent to each other in adjacent layers, forming a loop in each PCB stack. There are two DC input terminals at the center of the busbar, which are connected to the positive bus layer and the negative bus layer respectively. The busbar consists of eight vertical PCB stacks, forming four loops. The drains of the power switching devices in the upper bridge arms of each single-phase bridge structure are all connected to the positive bus layer, the power sources of the power switching devices in the lower bridge arms of each single-phase bridge structure are all connected to the negative bus layer, and the power sources of the power switching devices in the upper bridge arms of each single-phase bridge structure are connected to the drains of the power switching devices in the lower bridge arms of each single-phase bridge structure.

2. The PCB busbar according to claim 1, characterized in that, The power switching device is a SiC MOSFET.

3. The PCB busbar according to claim 1, characterized in that, The PCB busbar is circular in shape.

4. The PCB busbar according to claim 1, characterized in that, The metal window is a copper window, and the metal sheet is an irregularly shaped copper sheet of varying thickness.

5. The PCB busbar according to claim 4, characterized in that, The current carried by the busbar is proportional to the thickness of the copper sheet.

6. A motor controller, characterized in that, include: A power module, comprising the PCB busbar as described in any one of claims 1-5; The drive module is used to provide power to the motor; The control module is used to control the power module and the drive module to make the motor work.

Images