How to optimize electromagnetic compatibility design in power strip to reduce interference radiation?
Release Time : 2025-09-03
The electromagnetic compatibility design of power strips requires a coordinated approach across multiple dimensions, including circuit design, layout and routing, shielding and grounding, filtering and absorption, and process optimization, to systematically reduce interference radiation.
During the circuit design phase, low-noise components, such as low-loss inductors and low-equivalent series resistance (ESR) capacitors, should be prioritized to mitigate interference at the source. Simultaneously, the power supply topology should be optimized. For example, soft-switching technology can be used to reduce voltage and current fluctuations (dv/dt and di/dt) when power transistors are turned on and off, or spread spectrum technology can be used to disperse energy concentrations in frequency bands to avoid excessive radiation at specific frequencies. Furthermore, adding decoupling capacitors in critical signal paths can shorten current loops and suppress high-frequency noise propagation.
Power strip layout and routing should adhere to the principle of "high-frequency separation and proximity grounding." High-frequency circuits (such as switches and transformers) should be separated from low-frequency circuits (such as control chips and feedback circuits) to avoid mutual coupling. Signal lines should be placed as close to a complete ground plane as possible to minimize electromagnetic coupling. Conductors in adjacent wiring layers should be routed perpendicularly or diagonally to avoid signal crosstalk caused by parallel traces. For high-frequency current loops (such as the path from switch transistor to transformer to rectifier diode), the loop area should be reduced by shortening trace lengths and increasing copper foil width, thereby reducing the intensity of magnetic field radiation.
Shielding and grounding are key means of suppressing radiation. Adding metal shielding layers to key locations (such as transformers and inductors) and reliably grounding the shielding layers can effectively limit electromagnetic wave leakage. For example, wrapping the transformer with copper foil and grounding it can reduce magnetic field radiation. Metal casings should be sealed with conductive foam or copper foil tape to prevent electromagnetic leakage. Grounding should utilize single-point or multi-point grounding to ensure sufficiently low ground resistance and avoid the "antenna effect" caused by ground loops. For multilayer boards, the middle layer can be designated as a power or ground layer to reduce interlayer interference through interlayer isolation.
Filtering and absorption technologies can specifically suppress interference in different frequency bands. Install a power line filter at the power line entrance. X capacitors (connected across the L and N lines) filter differential-mode noise, Y capacitors (connected across the L/N lines and ground) filter common-mode noise, and common-mode inductors suppress common-mode currents. For high-frequency noise, you can add ferrite beads or loops in series with the signal line, or use RC/LC filters to further attenuate interference. Additionally, connecting an RC snubber circuit in parallel across the diode can absorb the voltage spikes generated by the reverse recovery current and reduce high-frequency radiation.
Process optimization must be implemented throughout the entire manufacturing process. PCB manufacturing utilizes high-precision laser etching to ensure trace accuracy and reduce electromagnetic radiation caused by edge burrs. Component soldering utilizes vacuum reflow technology to avoid poor contact and interference caused by cold solder joints and bridging. During production, process parameters such as soldering temperature and time are strictly controlled to ensure consistent and reliable soldering quality. Furthermore, electromagnetic simulation software is used to pre-evaluate the power strip, simulating the electromagnetic field distribution under different layouts. This allows for early identification of potential interference sources and design optimization, significantly reducing subsequent rectification costs.