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, Semiware has designed a complete protection scheme for PD fast charging.
I. Key Electrical Risks in USB-C PD Fast Chargers
| Risk Source | Potential Failure |
| AC Line Surge / Lightning Transients | APFC stage damage, primary MOSFET failure |
| ESD from Cable Plugging / User Contact | USB Type-C controller damage |
| Hot Plug Events | VBUS instability or abnormal PD negotiation |
| High-Frequency Switching Stress | MOSFET overheating and efficiency loss |
| Power Grid Disturbance | Reduced system reliability |
A robust protection architecture significantly improves charger safety, EMC performance, and long-term durability.
II. Recommended Protection Solution for USB-C PD Chargers
- AC Input Protection: GDT Gas Discharge Tube
The AC input stage is the first line of defense and one of the most vulnerable areas for surge events.
Lightning-induced transients and grid disturbances can generate high-energy spikes that threaten downstream circuits.
Adding a Gas Discharge Tube (GDT) before the rectifier stage enables rapid conduction during surge events, safely diverting excessive energy away from critical components.
GDT's Advantages
- Extremely high surge withstand capability
- Ultra-low leakage current during normal operation
- Long operational lifetime
- Effective high-energy transient suppression
- Main Power Stage Design: High-Efficiency MOSFETs Enhance Performance
MOSFETs are among the core components that critically influence fast-charging efficiency, thermal performance, and power density.
The judicious selection of MOSFETs not only boosts conversion efficiency but also effectively mitigates thermal stress within the system:
- Low RDS(on) — Reduces conduction losses
- High Voltage Withstand Capability — Typically found in 650V / 700V platforms
- Fast Switching Performance — Enhances APFC + PWM conversion efficiency
- Low Gate Charge (Qg) — Reduces switching losses
- Enhanced Avalanche Capability — Improves system reliability
↗️ Semiware Mosfet Product Line
- USB Type-C Port Protection — Low-Capacitance TVS Diode Arrays
The USB Type-C port is the interface most frequently accessed directly by users, making it the area most susceptible to electrical transients and stress.
Key risks include:
- Electrostatic Discharge (ESD)
- Hot-plugging transients
- Electrical Overstress (EOS)
- Abnormal connection scenarios
Strategically deploying low-capacitance (<1pF) TVS diode arrays provides robust protection for sensitive ICs without compromising the integrity of high-speed data signals.
↗️ Semiware TVS Diode Array Product Line
III. Reference Block Diagram
👉 Explore more: https://en.semiware.com/applications/pd-fast-charging/
Semiware offers a complete portfolio of components for system-level protection, including TVS diodes, ESD protection devices, GDTs (Gas Discharge Tubes), MOSFETs, and more.
Beyond providing components, we offer:
☑️ Circuit protection design support
☑️ EMC optimization recommendations
☑️ Component selection guidance and sample support
We invite you to contact us to collaborate on enhancing your product's reliability and system stability.
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