This should be a power supply circuit board.
Notice the four pairs of opposing small tips in the red circles — could it be for discharging electricity?
Great question! Those four pairs of opposing small tips in the red circles are ESD (Electrostatic Discharge) protection spark gaps — a common passive protection design for power supply circuit boards.
Core Purpose
- Shield the power supply’s internal components (like capacitors, ICs, or rectifiers) from electrostatic damage.
- Serve as a “safe vent” for static electricity, preventing high-voltage ESD from piercing sensitive chips or breaking down insulation.
How It Works
- The small opposing tips create a narrow air gap (usually just a few tenths of a millimeter).
- When static electricity builds up to a certain voltage (exceeding the air breakdown threshold, typically 2–10kV for such gaps), an arc jumps between the tips.
- This diverts the high-voltage static charge to ground, bypassing critical components and protecting the circuit.
Design Considerations for Power Supply Boards
- Power supplies are prone to ESD during handling, installation, or operation, so this passive design is cost-effective and reliable.
- The number of pairs (four here) and gap width are calibrated to match the power supply’s working voltage and ESD protection level (common targets: IEC 61000-4-2 Level 4).
- Unlike active ESD diodes, spark gaps don’t degrade over time and work well in high-temperature or high-voltage power supply environments.
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ESD-related. The layout of the common-mode choke coil uses a serrated copper foil pattern. This way, when the voltage difference at both ends becomes too large, tip discharge into the air will occur.
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This is a typical ESD discharge gap, an ultra-common passive protection design on power boards!
The core concept is to create a “fast discharge path” for static electricity: the opposing small tips inside the red circle form an extremely narrow air gap (typically just a fraction of a millimeter). When static accumulates to a certain voltage threshold, it directly arcs between these tips and discharges through the grounding path, preventing downstream sensitive components like ICs and capacitors from being damaged by breakdown.
This design offers low cost, high temperature resistance, and voltage tolerance advantages over ESD diodes, making it better suited for the harsh working environment of power boards. The four pairs of gaps are arranged to enhance protection redundancy, avoiding single-point failure risks.
The item circled in red is a passive ESD protection gap, specifically designed to address static electricity issues in power boards, offering clear advantages over active protection components:
- Compared to ESD diodes: It has no reverse leakage current, maintains stable performance in high-temperature environments (e.g., power board heat dissipation areas), and is resistant to surge impacts.
- Compared to varistors: It has faster response speed (nanosecond-level), blocks high-frequency static pulses, and has a compact size, saving valuable layout space on the power board.
Common misconception: Some may mistake it as “arc ignition” or “overvoltage fusing,” but this is entirely incorrect — the gap only targets transient high voltages from static electricity. Under normal operating voltages, the air gap remains insulating and does not affect circuit operation. The four-pair design further enhances protection stability.
Hmm… the AI’s response is this long?
How did you figure that out?
“Saw a pile of Markdown+Emoji and thought it was just a copied AI response…”
A bit like AI 
AI text output format is all markdown 
, Doubao is more normal, GPT adds emojis to every subheading
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