1. In the design of switching power supplies, PCB board design is a critical step that significantly impacts the performance, EMC requirements, reliability, and manufacturability of the power supply.
2. With the advancement of electronic technology, switching power supplies are becoming smaller, operating frequencies are increasing, and component densities are rising.
3. Consequently, the demands for anti-interference in PCB layout and wiring are becoming more stringent.
4. A well-planned and scientifically designed PCB layout can greatly enhance efficiency and effectiveness in your work.
1. Layout requirements
The PCB board layout demands precision, rather than mere placement and compression. General PCB layout should adhere to several key principles:
(1) The primary consideration in layout is ensuring optimal routing efficiency. Attention must be paid to interconnects when relocating components, grouping those with related connections together.
(2) Arrange components symmetrically and compactly around each functional circuit’s core components. This not only enhances aesthetics but also facilitates easier assembly, soldering, and mass production. Minimize lead lengths and inter-component connections. Ensure oscillators, decoupling capacitors, and filters are placed in close proximity to ICs, keeping ground paths short.
(3) Future soldering and maintenance considerations are crucial when placing components. Avoid situating small components between taller ones to prevent production and maintenance challenges. While density is important, balance it with advancements in electronic technology, especially in miniaturization and spatial efficiency. Consider IPC-A-610E standards to mitigate component misalignment risks affecting solder joints and component spacing.
(4) Optoelectronic coupling devices and current sampling circuits are susceptible to interference and should be distanced from sources of electric or magnetic fields, such as high-current traces, transformers, and devices with high potential pulsations.
(5) Prioritize minimizing the loop area of high-frequency pulse currents and large currents to suppress switching power supply radiation interference. High-frequency pulse current paths should be isolated from input/output terminals to enhance EMC performance.
(6) Heat-generating elements like transformers, switch tubes, and rectifier diodes should be strategically placed for even heat dissipation across the entire power supply. Ensure sensitive components such as ICs are sufficiently distanced from these heat sources and other devices that could affect system longevity.
(7) Consider the height of components on the bottom layer during layout. Uneven heights, particularly around potted DC-DC power modules, can lead to imbalanced pin heights post-potting.
(8) When laying out control pins, ensure adequate anti-static protection. Maintain sufficient distance between circuit components to prevent unintended capacitance, which could compromise module anti-static capabilities.
2. Wiring principle
(1) Keep small signal traces separated from high-current traces whenever possible, minimizing proximity or ensuring sufficient distance if they must run parallel. Minimize the loop area for critical small signal wiring such as current sampling and optocoupler feedback lines.
(2) Avoid lengthy parallel runs between adjacent traces, particularly in high-frequency circuits where right angles and acute angles should be avoided to maintain electrical performance.
(3) Segregate power and control circuits, employing single-point grounding. Ground components around primary PWM control ICs directly to the IC’s ground pin, leading to a large capacitance ground wire and onward to power ground. Use a parallel single-point grounding method for multiple ICs.
(4) Avoid placing high-frequency components on the bottom layer directly beneath other components. If unavoidable, shield them, ensuring high-frequency components on the top layer are shielded from the control circuit on the bottom layer using copper shielding.
(5) Focus on optimal routing of filter capacitors to enhance ripple and noise filtering effectiveness, ensuring superior performance in noise-sensitive applications.
(6) Proximity of power and ground lines should be minimized to reduce loop area, thereby mitigating electromagnetic interference. Maintain consistent line width without abrupt changes to enhance electrical performance.
(7) Utilize large bare copper areas beneath components generating substantial heat, such as TO-252 MOS tubes, to improve component reliability. Use tinned bare copper to handle high-current flows through narrow sections of power traces.
3. Safety distance and process requirements
(1) Ensure adequate electrical clearance and creepage distance between conductors and adjacent conductive surfaces. Utilize isolation slots where necessary to enhance primary and secondary isolation, adhering to specific slot dimensions for optimal safety and performance.
(2) Components positioned at the edge of the PCB should maintain a sufficient distance from the board’s edge to prevent manufacturing issues or performance compromises.
(3) Implement teardrops where trace widths entering round pads or via holes are smaller than the pad diameter, reinforcing adhesion to prevent detachment.
(4) Provide thermal isolation for SMD device pins connected to large copper areas to prevent soldering issues during reflow due to rapid heat dissipation.
(5) Consider the feasibility of sub-boarding during PCB assembly, ensuring adequate component-to-edge distances to mitigate stress-induced component warping. Use appropriate slotting to alleviate stress during PCB breaking.
These guidelines reflect best practices in PCB design, particularly for switching power supplies, ensuring both functionality and manufacturability are optimized.
2. With the advancement of electronic technology, switching power supplies are becoming smaller, operating frequencies are increasing, and component densities are rising.
3. Consequently, the demands for anti-interference in PCB layout and wiring are becoming more stringent.
4. A well-planned and scientifically designed PCB layout can greatly enhance efficiency and effectiveness in your work.
1. Layout requirements
The PCB board layout demands precision, rather than mere placement and compression. General PCB layout should adhere to several key principles:
(1) The primary consideration in layout is ensuring optimal routing efficiency. Attention must be paid to interconnects when relocating components, grouping those with related connections together.
(2) Arrange components symmetrically and compactly around each functional circuit’s core components. This not only enhances aesthetics but also facilitates easier assembly, soldering, and mass production. Minimize lead lengths and inter-component connections. Ensure oscillators, decoupling capacitors, and filters are placed in close proximity to ICs, keeping ground paths short.
(3) Future soldering and maintenance considerations are crucial when placing components. Avoid situating small components between taller ones to prevent production and maintenance challenges. While density is important, balance it with advancements in electronic technology, especially in miniaturization and spatial efficiency. Consider IPC-A-610E standards to mitigate component misalignment risks affecting solder joints and component spacing.
(4) Optoelectronic coupling devices and current sampling circuits are susceptible to interference and should be distanced from sources of electric or magnetic fields, such as high-current traces, transformers, and devices with high potential pulsations.
(5) Prioritize minimizing the loop area of high-frequency pulse currents and large currents to suppress switching power supply radiation interference. High-frequency pulse current paths should be isolated from input/output terminals to enhance EMC performance.
(6) Heat-generating elements like transformers, switch tubes, and rectifier diodes should be strategically placed for even heat dissipation across the entire power supply. Ensure sensitive components such as ICs are sufficiently distanced from these heat sources and other devices that could affect system longevity.
(7) Consider the height of components on the bottom layer during layout. Uneven heights, particularly around potted DC-DC power modules, can lead to imbalanced pin heights post-potting.
(8) When laying out control pins, ensure adequate anti-static protection. Maintain sufficient distance between circuit components to prevent unintended capacitance, which could compromise module anti-static capabilities.
2. Wiring principle
(1) Keep small signal traces separated from high-current traces whenever possible, minimizing proximity or ensuring sufficient distance if they must run parallel. Minimize the loop area for critical small signal wiring such as current sampling and optocoupler feedback lines.
(2) Avoid lengthy parallel runs between adjacent traces, particularly in high-frequency circuits where right angles and acute angles should be avoided to maintain electrical performance.
(3) Segregate power and control circuits, employing single-point grounding. Ground components around primary PWM control ICs directly to the IC’s ground pin, leading to a large capacitance ground wire and onward to power ground. Use a parallel single-point grounding method for multiple ICs.
(4) Avoid placing high-frequency components on the bottom layer directly beneath other components. If unavoidable, shield them, ensuring high-frequency components on the top layer are shielded from the control circuit on the bottom layer using copper shielding.
(5) Focus on optimal routing of filter capacitors to enhance ripple and noise filtering effectiveness, ensuring superior performance in noise-sensitive applications.
(6) Proximity of power and ground lines should be minimized to reduce loop area, thereby mitigating electromagnetic interference. Maintain consistent line width without abrupt changes to enhance electrical performance.
(7) Utilize large bare copper areas beneath components generating substantial heat, such as TO-252 MOS tubes, to improve component reliability. Use tinned bare copper to handle high-current flows through narrow sections of power traces.
3. Safety distance and process requirements
(1) Ensure adequate electrical clearance and creepage distance between conductors and adjacent conductive surfaces. Utilize isolation slots where necessary to enhance primary and secondary isolation, adhering to specific slot dimensions for optimal safety and performance.
(2) Components positioned at the edge of the PCB should maintain a sufficient distance from the board’s edge to prevent manufacturing issues or performance compromises.
(3) Implement teardrops where trace widths entering round pads or via holes are smaller than the pad diameter, reinforcing adhesion to prevent detachment.
(4) Provide thermal isolation for SMD device pins connected to large copper areas to prevent soldering issues during reflow due to rapid heat dissipation.
(5) Consider the feasibility of sub-boarding during PCB assembly, ensuring adequate component-to-edge distances to mitigate stress-induced component warping. Use appropriate slotting to alleviate stress during PCB breaking.
These guidelines reflect best practices in PCB design, particularly for switching power supplies, ensuring both functionality and manufacturability are optimized.
