1️⃣ Why Protection is Critical in High-Power PD Chargers?
With the widespread adoption of USB Type-C and USB Power Delivery (PD) technologies, the power output of fast charging devices is constantly increasing (30W, 65W, and even 140W+). At such high power densities, chargers not only need to be small and fast, but also safe and stable.
To ensure the reliability of the entire power path, we have designed a complete protection scheme for PD fast charging.
Reference Block Diagram：
2️⃣ Key Device Selection Considerations
🔸 AC Input Terminal: GDT Gas Discharge Tube
The AC input terminal is most vulnerable to lightning surges and strong interference spikes from the power grid. Adding a GDT gas discharge tube before the rectifier stage allows for rapid conduction during high-energy transients, bypassing dangerous voltages to ground, thus protecting:
- APFC Front-End Circuit
- Main Power MOSFET
- Subsequent Transformer and Controller
Advantages of the gas discharge tube include:
- Extremely high surge withstand capability
- Low leakage current, does not affect normal operation
🔸 Main Power Stage: High-Efficiency MOSFETs Ensure Conversion Efficiency
In fast-charging power supplies, MOSFETs are key components affecting energy efficiency and temperature rise. We use MOSFETs in the following locations:
✔ Primary Switch
MOSFETs used for the primary switch must possess:
- Low Rds(on) → Reduces switching losses
- High withstand voltage → Typically 650V/700V or similar ratings
- Fast switching characteristics → Improves APFC + PWM system efficiency
✔ Synchronous Rectifier (SR) Switch
Using low on-resistance MOSFETs can achieve:
- Significantly reduced conduction losses
- Improved energy efficiency of 65W/100W PD output
- Reduced temperature rise, reducing heat dissipation pressure
🔸 Type-C Interface
The Type-C interface, being the point of direct contact for end users, is easily affected by electrostatic discharge (ESD), transient plugging/unplugging, and incorrect connections.
✔ ESD Protection Devices (TVS)
- We deploy ESD protection on sensitive lines such as CC/SBU/DP/DM/VBUS:
- <1pF ultra-low capacitance (does not affect the integrity of high-speed interface signals)
- IEC 61000-4-2 Level 4 protection
- Fast response speed
✔ Load Switch MOS (VBUS Switch)
- Responsible for turning the PD output on/off. Features:
- Low Rds(on) → Reduces VBUS voltage drop
- Supports high current (3A/5A)
- Used for overcurrent protection, soft start, thermal shutdown, and other mechanisms.
3️⃣ Design Benefits
- High Reliability: Input surges no longer threaten the upstream APFC and MOS.
- High Efficiency: SR MOS reduces heat loss and improves overall conversion efficiency.
- High Safety: The Type-C port has comprehensive ESD + OCP protection.
- Extended Product Lifespan: Reduces component stress and minimizes after-sales risks.
🔍 Looking for Complete PD Protection Solutions?
Looking for complete protection components for PD fast charging, USB-C ports, adapters, and system-level designs?
Explore our full range of surge, ESD, MOSFET, and circuit-level protection solutions 👉 https://en.semiware.com/application/
🔹 About Semiware
Semiware is a professional manufacturer of circuit protection and discrete semiconductor devices, headquartered in Shanghai, China.
Founded by experienced engineers in the circuit protection industry, we focus on developing high-reliability TVS diodes, ESD protection devices, GDTs, Triacs, and other discrete components for global OEM and EMS customers.
Our products are widely used in:
- Network & Telecom Equipment
- Automotive Electronics
- Industrial Control Systems
- Security Devices
- New Energy Applications
- Consumer Electronics
We not only supply components, but also provide professional circuit protection design support and EMC technical assistance to help customers improve product reliability.
Stable quality, competitive pricing, and reliable delivery make us a trusted partner for long-term cooperation.
📩 Feel free to contact us for samples or technical discussion.
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