DCDC common-mode noise suppression circuit for electronic control unit

Abstract

The invention relates to the related technical field of circuit substrates, and discloses a DCDC common-mode noise suppression circuit for an electronic control unit, which comprises the electronic control unit, and the electronic control unit distributes a power supply through a DC-DC converter and is a system block diagram of an electric power steering electronic control unit. The whole vehicle power input supplies power to the power management chip, the driving chip and the motor driving circuit. The power supply management chip is responsible for distributing a power supply and supplying power to the CAN transceiver, the microprocessor, the motor angle sensor, the TAS sensor and other chips; the microprocessor is interconnected with other chips; through the synergistic effect of the normal filter and the common-mode filter, in combination with the ground plane segmentation design and the conduction effect of the conductive metal screws, efficient suppression of differential-mode noise and common-mode noise is realized near a noise emission source, the electromagnetic disturbance of an electronic control unit is effectively reduced, and the noise suppression effect of the electronic control unit is improved. And the electromagnetic compatibility of the electronic control unit and the whole vehicle is improved.

Description

Technical Field

[0001] This invention belongs to the technical field of circuit boards, and more specifically, it relates to a DC-DC common-mode noise suppression circuit for electronic control units. Background Technology

[0002] In electronic control units such as electric power steering, the DC-DC converter (DCDC) is a core component for power management. The power management chip controls the input power by alternating switching of the DCDC input power (duty cycle adjustment), thereby achieving stable output voltage regulation to power components such as CAN transceivers, microprocessors, and TAS sensors. However, the switching characteristics of the DCDC generate intentional electromagnetic interference at a fixed frequency. This interference can be transmitted to various parts of the circuit board through the power supply loop and ground loop, and then spread through the vehicle wiring harness or space radiation. This not only affects the stability of the internal circuitry of the electronic control unit, but also reduces the electromagnetic compatibility (EMC) performance of the entire vehicle.

[0003] Existing technologies typically incorporate filters with common-mode coils at the power port of the electronic control unit (ECU), but this approach suffers from three major drawbacks: first, the common-mode coil is bulky, limiting the miniaturization of the ECU; second, the common-mode coil is expensive, increasing manufacturing costs; and third, the noise suppression point is far from the DC-DC converter (emitter), allowing noise to diffuse throughout the substrate, failing to effectively prevent interference with sensitive components such as TAS sensors and motor angle sensors. Therefore, a noise solution that achieves "source-end suppression and a compact structure" is urgently needed.

[0004] Therefore, in view of this, we have studied and improved the existing structure and its shortcomings, and provided a DC-DC common-mode noise suppression circuit for electronic control units, in order to achieve a more practical and valuable purpose. Summary of the Invention

[0005] The present invention provides a DC-DC common-mode noise suppression circuit for electronic control units, which overcomes the above-mentioned defects in the prior art.

[0006] The purpose and effectiveness of the DC-DC common-mode noise suppression circuit for electronic control units of this invention are achieved by the following specific technical means: A DC-DC common-mode noise suppression circuit for an electronic control unit includes a substrate body and a circuit section formed on the substrate body; the circuit section includes a power management circuit (the core component of which is a power management chip U1), the power management circuit integrating a DC-DC converter (DCDC) and configured with a normal mode filter (for suppressing differential-mode noise) and a common-mode filter (for suppressing common-mode noise), the specific structure of which is as follows: Normal state filters: These include normal state filter 1 and normal state filter 2. If the output stage Vout of the power management circuit has multiple outputs, normal state filter n can be added to ensure full-channel differential mode noise suppression. The first normal-state filter is located at the input stage Vin of the power management circuit and consists of an L1 inductor and a C3 capacitor. Power flows into the input stage Vin through the L1 inductor, and the two ends of the C3 capacitor are connected to the power input Vin and the dedicated ground plane GND P (power management chip ground plane) of the power management circuit, respectively. The L1 inductor is used to impede the conduction of differential-mode noise, and the C3 capacitor is used to bypass the differential-mode noise of the input stage to the ground plane GND P, thereby achieving precise suppression of differential-mode noise in the input stage.

[0007] The second normal filter is located at the output stage Vout of the power management circuit and consists of capacitor C4. The two ends of capacitor C4 are connected to the power output Vout and the ground plane GND P, respectively, to bypass the differential mode noise of the output stage to the ground plane GNDP, thus preventing differential mode noise from interfering with the load components at the output end.

[0008] Normal filter n: When the output stage Vout of the power management circuit has multiple outputs (such as simultaneously powering a microprocessor, sensor, and CAN transceiver), each output is configured with a "normal filter n" that has the same structure as the second normal filter, ensuring that differential mode noise of different output channels is effectively suppressed.

[0009] Common-mode filter: Located between the input stage Vin of the power management circuit and the ground plane GND P, and works in conjunction with the metal housing of the electronic control unit (the housing is connected to the vehicle ground). The common-mode filter consists of capacitor C1, resistor R2, capacitor C2, and resistor R3. After capacitor C1 is connected in series with resistor R2, one end is connected to the chassis and the other end is connected to the L1 inductor coil of the input stage (i.e., the power input path). After capacitor C2 is connected in series with resistor R3, one end is connected to the chassis and the other end is connected to ground plane GND P; Utilizing the low impedance characteristics of capacitors to high-frequency noise, common-mode noise (containing a large amount of AC components) will preferentially flow into capacitors C1 and C2, which have even lower high-frequency impedance, and then be conducted to the vehicle ground through the chassis, thus achieving common-mode noise shunt suppression. Resistors R2 and R3 are used to limit the amplitude of common-mode noise current, preventing component overcurrent damage, and optimizing the filtering frequency characteristics.

[0010] Ground plane design: The dedicated ground plane GND P of the power management circuit is connected to the substrate ground plane GND (the common ground of the 200 circuit board) through resistor R1, realizing "resistor single-point grounding". This ground plane segmentation design can effectively plan the noise return path, avoid noise coupling between different ground planes, optimize impedance matching, and further improve the noise suppression performance of the filter.

[0011] Conductor section (210 screw): A conductive metal 210 screw is mounted on one or both surfaces of the substrate body as a conductor section. At least a portion of this conductor section is located at the clamping position of at least two of the following: capacitor C1, capacitor C2, power management circuit input stage Vin, and ground plane GND P (ensuring the shortest noise current conduction path). The 210 screw is formed on the substrate surface and fastened to the housing (serving both substrate fixation and electrical connection functions), and is electrically connected to the other end of capacitor C1 and capacitor C2, respectively, such that: Current can flow between capacitors C1 and C2 through the 210 screw; Current can flow between capacitors C1 and C2 and the housing through the 210 screw; Ultimately, the common-mode noise current is efficiently transferred to the chassis and then flows back from the chassis to the 200 circuit board, significantly reducing the area of ​​the noise propagation loop and reducing noise radiation and conduction.

[0012] Flexible component design: The components involved in this invention, such as the L1 inductor, C1 capacitor, C2 capacitor, C3 capacitor, C4 capacitor, R1 resistor, R2 resistor, and R3 resistor, are not limited to a single component. In practical applications, multiple corresponding components (such as multiple capacitors connected in parallel to increase the capacitance value, or multiple resistors connected in series to adjust the resistance value) can be combined according to the noise characteristics, voltage and current parameters of the 200 circuit board. The specific parameters of the components (such as inductance, capacitance, and resistance values) must be matched with the appropriate 200 circuit board to achieve the best noise suppression effect.

[0013] A circuit board based on the above-mentioned noise suppression circuit is a six-layer 200 circuit board, including L1 layer 200A (top layer), L2 layer 200B (inner layer), L3 layer 200C (inner layer), L4 layer 200D (inner layer), L5 layer 200E (inner layer), and L6 layer 200F (bottom layer), and is provided with a 230 solder mask layer, the specific design of which is as follows: Substrate layer number and solder mask design: The six-layer structure of the 200 circuit board has a clear division of labor. The L1 layer 200A is the core component and conductor pattern arrangement layer, the L2 layers 200B-L5 layers 200E are the inner power, ground or signal layers, and the L6 layer 200F is the auxiliary component arrangement layer. The 230 solder mask layer covers the non-pad areas of the L1 layer 200A and the L6 layer 200F to protect the conductor patterns and prevent oxidation and short circuits.

[0014] Conductive connection structure: The 200 circuit board has 224 conductive vias (used to realize electrical connection between different layers). The 224 conductive vias are connected to the 205 conductor pattern on the L1 layer 200A. The 210 screws are in close contact with the 224 conductive vias to realize a reliable electrical connection between the housing and the 205 conductor pattern, providing a path for common mode noise current to flow to the housing.

[0015] The conductor patterns and component connections in L1 layer 200A: Multiple conductor patterns (conductor pattern 201, conductor pattern 202, conductor pattern 203, conductor pattern 204, conductor pattern 205, conductor pattern 206, conductor pattern 207, conductor pattern 208, and conductor pattern 209) are formed on L1 layer 200A. The connection relationships between each conductor pattern and the components are as follows: Vehicle power supply path: The vehicle power supply (such as VBAT) flows through the 201 conductor pattern, through the reverse connection protection diode D1, and then into the 202 conductor pattern; it then flows through the L1 inductor coil into the 203 conductor pattern, and finally flows into the input Vin of the power management chip U1 through the 203 conductor pattern.

[0016] Input differential mode noise filtering: The 203 conductor pattern is connected to one end of the C3 capacitor, and the other end of the C3 capacitor is connected to the 207 conductor pattern corresponding to the ground plane GND P, so as to bypass the input differential mode noise to GND P.

[0017] Output stage differential noise filtering: The output Vout of the power management chip U1 is connected to one end of the C4 capacitor through the 209 conductor pattern, and the other end of the C4 capacitor is connected to the 207 conductor pattern, so as to bypass the output stage differential noise to GND P.

[0018] Ground plane connection: Conductor pattern 207 (corresponding to GND P) is connected to conductor pattern 208 (corresponding to the substrate ground plane GND) through resistor R1 to achieve single-point grounding of the resistor.

[0019] Common-mode noise conduction: Conductor pattern 202 is connected to conductor pattern 204 through resistor R2. Conductor pattern 204 is connected to one end of capacitor C1, and the other end of capacitor C1 is connected to conductor pattern 205. Conductor pattern 207 is connected to conductor pattern 206 through resistor R3. Conductor pattern 206 is connected to one end of capacitor C2, and the other end of capacitor C2 is connected to conductor pattern 205. The 205 conductor pattern is connected to the housing via a 210 screw, forming a common-mode noise current conduction path of "200 circuit board → C1 capacitor / C2 → 205 conductor pattern → 210 screw → housing → vehicle ground".

[0020] Pad connections: To ensure reliable connection between components and conductor patterns, dedicated pads are used at critical connection points. The connection point for capacitor C1 on the 204 conductor pattern is pad 220a, and the connection point on the 205 conductor pattern is pad 220b. The connection point for capacitor C2 on conductor pattern 205 is pad 222a, and the connection point on conductor pattern 206 is pad 222b.

[0021] Compared with the prior art, the present invention has the following beneficial effects: By combining the synergistic effect of the normal mode filter and the common mode filter, along with the ground plane segmentation design and the conduction effect of the conductive metal screws, efficient suppression of differential mode noise and common mode noise is achieved near the noise emission source, effectively reducing electromagnetic interference of the electronic control unit and improving the electromagnetic compatibility performance of the electronic control unit and the whole vehicle.

[0022] Noise suppression can be achieved by using small components such as capacitors and resistors and optimizing the substrate structure, without the need for bulky common-mode coils. This significantly reduces the size of noise suppression-related structures and provides favorable conditions for the miniaturization design of electronic control units.

[0023] It avoids the use of high-cost components such as common-mode coils, and uses low-cost components such as capacitors, resistors, and screws. The structural design is simple, which reduces the production and manufacturing costs of the product.

[0024] Conductive metal screws not only conduct noise but also provide a fixed connection, eliminating the need for additional steps, simplifying the installation process, and effectively improving production efficiency. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0027] Figure 1 This is a system block diagram of the electric power steering electronic control unit of the present invention.

[0028] Figure 2 This is a simplified schematic diagram of the filter of the present invention.

[0029] Figure 3 This is a partial top view of the DC-DC noise suppression circuit in the 200 circuit board of the electronic control unit.

[0030] Figure 4 This is a cross-sectional view of the internal structure of the connection between the 200 common-mode filter of the electronic control unit and the housing.

[0031] Explanation of reference numerals in the attached figures: 1. Normal filter; 2. Normal filter; n. Normal filter; 200 circuit board; L1 layer 200A; L2 layer 200B; L3 layer 200C; L4 layer 200D; L5 layer 200E; L6 layer 200F; Conductor patterns 201, 201; Conductor patterns 202, 202; Conductor patterns 203, 203; Conductor patterns 204, 204; Conductor patterns 205, 205; Conductor patterns 206, 206; Conductor patterns 207, 207; Conductor patterns 208, 208; Conductor patterns 209, 209; Screws 210, 210; 220a, 220a pads; 220b, 220b pads; 222a, 222a pads; 222b, 222b pads; 224. Conductive via; 230. Solder mask layer; D1. Reverse polarity protection diode; L1. Inductor coil; C1, C1 capacitor; C2, C2 capacitor; C3, C3 capacitor; C4, C4 capacitor; R1, R1 resistor; R2, R2 resistor; R3, R3 resistor; U1, power management chip; GND P, power management chip ground plane; GND, substrate ground plane GND; Vin, power input Vin; Vout, power output Vout. Detailed Implementation

[0032] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0033] In the description of this invention, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," "outer," "front end," "rear end," "head," "tail," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and 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, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0034] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" 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. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0035] As attached Figure 1 To be continued Figure 4 As shown: The present invention provides a DC-DC common-mode noise suppression circuit for an electronic control unit, comprising an electronic control unit that distributes power through a DC-DC converter.

[0036] Figure 1 This is a system block diagram of the electric power steering electronic control unit. The vehicle's power input supplies power to the power management chip, drive chip, and motor drive circuit. The power management chip is responsible for distributing power to chips such as the CAN transceiver, microprocessor, motor angle sensor, and TAS sensor. The microprocessor interconnects with other chips and communicates with the vehicle via the CAN transceiver. By analyzing and calculating the signals returned from circuits such as the TAS sensor and motor angle sensor, the microprocessor sends corresponding operating instructions to the drive chip, which then controls the motor drive circuit to output three-phase current to drive the motor.

[0037] The power management chip regulates the output voltage through a DC-DC converter (hereinafter referred to as DCDC). The DCDC controls the input power by alternately switching the input power supply (i.e., duty cycle regulation). During operation, it will generate intentional electromagnetic interference at a fixed frequency. This interference can be transmitted to various parts of the substrate through the power supply and ground loops, and then propagated to the whole vehicle through wiring harnesses or spatial radiation; affecting the electronic control unit and even the electromagnetic compatibility performance of the whole vehicle.

[0038] Figure 2The diagram shows a simplified schematic of the filter provided by this invention. To suppress the noise generated by the DC-DC circuit of the power management chip, two types of filters are provided: a normal mode filter and a common mode filter.

[0039] The first normal filter is set in the input stage Vin of the power management chip U1. It consists of an inductor L1 and a capacitor C3. Power flows into Vin through L1. The two ends of the capacitor C3 are connected to the power input Vin and the ground plane GND P of the U1 chip, respectively. L1 and C3 are simplified models. In the actual implementation, they can be composed of multiple inductors or capacitors. The specific values ​​also need to be matched with the specific substrate.

[0040] The second normal filter is located at the output stage Vout of the power management chip U1. The two ends of capacitor C4 are connected to the ground plane GND P that connects the power output Vout and the U1 chip. C4 is a simplified model; in a real implementation, it can be composed of multiple capacitors, and the specific values ​​must be matched with the specific substrate.

[0041] The output stage Vout of power management chip U1 is a simplified model. In a real implementation, it can be composed of multiple capacitors, and the specific values ​​must be matched with the specific substrate. In practice, it may have multiple outputs; therefore, a normal operating filter n will be included, following the same design concept as the second normal operating filter. A common-mode filter is positioned between the input stage Vin of the power management chip U1 and the ground plane GND P. The housing is the metal casing of the electronic control unit and is connected to the vehicle ground. Capacitor C1 and resistor R2 are connected in series between the housing and the differential-mode filter L1 of the power input stage; capacitor C2 and resistor R3 are connected in series between the housing and the ground plane GND P of the power management chip U1. Capacitors C1, C2, R2, and R3 are simplified models; in practice, they can be composed of multiple resistors or capacitors, and their specific values ​​must be matched with the specific substrate.

[0042] This invention segments the ground plane of the electronic control unit. The ground plane GND P of the power management chip U1 is connected to the substrate ground plane GND through resistor R1. Resistor R1 is a simplified model; in a specific implementation, multiple resistors can be used at different points on the substrate for matching. Ground segmentation can effectively plan noise return paths, perform impedance matching, and better utilize the filter's performance.

[0043] Figure 3 This is a partial top view showing the DC-DC noise suppression circuit in the 200 circuit board of the electronic control unit.

[0044] Figure 4 This is a cross-sectional view of the internal structure of the common-mode filter and the housing connection area in the 200 circuit board.

[0045] like Figure 3 As shown, on layer L1 200A of the 200 circuit board, the vehicle power supply flows through conductor pattern 201, reverse polarity protection diode D1, and into conductor pattern 202; then through inductor coil L1 into conductor pattern 203; from conductor pattern 203 into the input Vin of power chip U1, simultaneously bypassing capacitor C3, and returning to capacitor C3 through conductor pattern 207 on the ground plane of U1; the output Vout of power chip U1 bypasses capacitor C4 through conductor pattern 209, and returns to capacitor C4 through conductor pattern 207 on the ground plane of U1. Conductor pattern 207 on the ground plane of U1 is connected to conductor pattern 208 on the ground plane of the 200 circuit board through resistor R1.

[0046] Conductor pattern 202 is connected to conductor pattern 204 via resistor R2, and then connected to conductor pattern 205 via capacitor C1. Conductor pattern 205 is connected to the housing via screw 210. The ground plane GND P of power management chip U1 is connected to conductor pattern 206 via conductor pattern 207 and resistor R2. Conductor pattern 206 is connected to conductor pattern 205 via capacitor C2. Pad 220a is the connection point for capacitor C1 on conductor pattern 204, pad 220b is the connection point for capacitor C1 on conductor pattern 205, pad 222a is the connection point for capacitor C2 on conductor pattern 205, and pad 222b is the connection point for capacitor C2 on conductor pattern 206.

[0047] like Figure 4 As shown, the 200 circuit board is formed into a six-layer structure. The 200 circuit board, for example, includes layer L1 200A, layer L2 200B, layer L3 200C, layer L4 200D, layer L5 200E, and layer L6 200F. 230 is the solder mask layer of the 200 circuit board. Conductive vias 224 are connected to a conductor pattern 205. The housing is connected to the conductor pattern 205 by screws 210 that contact the conductive vias 224.

[0048] As explained above, in the electronic control unit of this embodiment, screw 210 connects the common terminal of capacitors C1 and C2 in a tightened state, thereby allowing current generated by noise from the DC-DC circuit of the power management chip U1 to flow to the housing via screw 210. As a result, according to circuit board 200, common-mode noise can be reduced.

[0049] DC-DC noise is generated by repeated switching of the power supply. Assuming there is no 210 screw, this noise travels through a large loop formed by the vehicle's power supply (battery or smart power supply), electronic control unit, vehicle wiring harness, and ground.

[0050] In contrast, with this embodiment, noise is transmitted from the substrate to the housing and also flows back from the housing to the substrate; the resulting loop is much smaller than the loop without the 210 screws. Furthermore, since common-mode noise contains a large amount of AC components, it flows into the C1 and C2 capacitors, which have lower high-frequency impedances. This helps to reduce common-mode noise.

[0051] Furthermore, according to the 200 circuit board, when the 210 screws are set on the board, common mode noise can be reduced without adding new processes by simply tightening the screws.

[0052] The embodiments of the present invention are given for illustrative and descriptive purposes only, and are not intended to be exhaustive or to limit the invention to the forms disclosed. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described in order to better illustrate the principles and practical application of the invention, and to enable those skilled in the art to understand the invention and to design various embodiments with various modifications suitable for a particular purpose.

Claims

1. A DC-DC common-mode noise suppression circuit for an electronic control unit, characterized in that, It includes a substrate body and a circuit section formed on the substrate body; the circuit section includes a power management circuit for an integrated DC-DC converter and is configured with a normal mode filter and a common mode filter; The normal state filter includes a normal state filter located at the input stage Vin of the power management circuit and a normal state filter located at the output stage Vout. The normal state filter consists of an L1 inductor and a C3 capacitor. Power flows into Vin through L1, and the two ends of the C3 capacitor are connected to Vin and the ground plane GND P of the power management circuit, respectively. The second normal filter is composed of a C4 capacitor, with its two ends connected to Vout and GND P respectively; the common mode filter is located between Vin and GND P, and the housing of the electronic control unit is connected to the vehicle ground. The common-mode filter includes capacitor C1, resistor R2, capacitor C2, and resistor R3. Capacitor C1 and resistor R2 are connected in series between the housing and L1. Capacitor C2 and resistor R3 are connected in series between the housing and GND P. GND P is connected to the ground plane GND of the substrate through resistor R1, realizing single-point grounding of the resistor.

2. The DC-DC common-mode noise suppression circuit for an electronic control unit according to claim 1, characterized in that, The substrate body has 210 screws made of conductive metal mounted on one or both sides as conductors; the 210 screws are at least partially located at the clamping positions of at least two of the C1 capacitor, C2 capacitor, Vin and GND P, and are fastened to the housing; the 210 screws are electrically connected to the other end of the C1 capacitor and the other end of the C2 capacitor respectively, and the current can flow between the C1 capacitor and the C2 capacitor through the 210 screws, or between the C1 capacitor, the C2 capacitor and the housing.

3. The DC-DC common-mode noise suppression circuit for an electronic control unit according to claim 1, characterized in that, The L1 inductor, C3 capacitor, C4 capacitor, C1 capacitor, C2 capacitor, R2 resistor, R3 resistor, and R1 resistor can all be composed of multiple corresponding components, and the component values ​​are matched with the compatible 200 circuit board. When the output stage Vout of the power management circuit has multiple outputs, each output is configured with a normal filter n that is consistent with the structure of the second normal filter.

4. A DC-DC common-mode noise suppression circuit for an electronic control unit based on any one of claims 1-3, characterized in that, The circuit board is a 200 circuit board, which has a six-layer structure, including L1 layer 200A, L2 layer 200B, L3 layer 200C, L4 layer 200D, L5 layer 200E, L6 layer 200F and a 230 solder mask layer. The 200 circuit board has 224 conductive vias, which are connected to the conductor pattern on the 200 circuit board. The connection between the housing and the conductor pattern is achieved by contacting the 224 conductive vias with 210 screws.

5. The DC-DC common-mode noise suppression circuit for an electronic control unit according to claim 4, characterized in that, On the L1 layer 200A of the 200 circuit board, the vehicle power supply flows through the conductor pattern through the reverse connection protection diode D1, and then flows into the Vin of the power management circuit through the L1 inductor coil and the conductor pattern in sequence. At the same time, it is bypassed to the C3 capacitor and flows back to the C3 capacitor through the conductor pattern corresponding to GND P. The Vout of the power management circuit is bypassed to capacitor C4 through the conductor pattern, and returned to capacitor C4 through the conductor pattern corresponding to GND P; the conductor pattern corresponding to GND P is connected to the conductor pattern corresponding to the GND ground plane of the substrate through resistor R1.

6. A DC-DC common-mode noise suppression circuit for an electronic control unit according to claim 5, characterized in that, The conductor patterns on layer L1 200A include conductor patterns 201, 202, 203, 204, 205, 206, 207, 208, and 209. Conductor pattern 202 is connected to conductor pattern 204 via resistor R2, conductor pattern 204 is connected to conductor pattern 205 via capacitor C1, and conductor pattern 205 is connected to the housing via a 210 screw. Conductor pattern 207, corresponding to GND P, is connected to conductor pattern 206 via resistor R3, and conductor pattern 206 is connected to conductor pattern 205 via capacitor C2. The connection point of capacitor C1 on conductor pattern 204 is pad 220a, and the connection point on conductor pattern 205 is pad 220b. The connection point of capacitor C2 on conductor pattern 205 is pad 222a, and the connection point on conductor pattern 206 is pad 222b.

7. A DC-DC common-mode noise suppression circuit for an electronic control unit according to claim 4, characterized in that, The 230 solder resist layer covers the non-pad areas of the L1 layer 200A and L6 layer 200F of the 200 circuit board, and is made of insulating and heat-resistant material, with a temperature range of not less than -40℃ to 125℃.

8. A DC-DC common-mode noise suppression circuit for an electronic control unit according to claim 1, characterized in that, The C1 and C2 capacitors are high-frequency ceramic capacitors, while the C3 and C4 capacitors are a combination of aluminum electrolytic capacitors and ceramic capacitors, respectively adapted to the suppression requirements of high-frequency common-mode noise and high- and low-frequency differential-mode noise.

9. A DC-DC common-mode noise suppression circuit for an electronic control unit according to claim 2, characterized in that, The 210 screw has a tin-plated layer on its surface. The 210 screw is connected to the housing by a threaded fastening. After fastening, the contact resistance between the 210 screw and the housing is no greater than 50mΩ.

10. A DC-DC common-mode noise suppression circuit for an electronic control unit according to claim 5, characterized in that, The L2 layer 200B of the 200 circuit board is an inner power layer used to transmit power to the entire vehicle; the L3 layer 200C is an inner ground layer, corresponding to the ground plane GND of the board; the L4 layer 200D and L5 layer 200E are inner signal layers, used to arrange the transmission paths of control signals and sensor signals, respectively.

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