High-Efficiency Power Adapter

The power adapter solution can support various fast charging protocols when combined with appropriate protocol controllers: 1) USB-C PD (Power Delivery) - up to 65W with proper controller, 2) Qualcomm Quick Charge - QC2.0, QC3.0, QC4+ with dedicated controller, 3) USB BC1.2 - standard USB charging, 4) Apple 2.4A - for Apple devices, 5) Samsung AFC - Adaptive Fast Charging. The BP3288 provides the power stage, while protocol detection and negotiation require additional controller ICs. LiTong can recommend compatible protocol controllers for your target devices.

Select protocol controllers based on target devices. Contact LiTong for fast charging solution recommendations.

Achieving ultra-low standby power (<30mW): 1) Use burst mode operation at no-load, 2) Minimize startup resistor current (use active startup), 3) Optimize feedback network power consumption, 4) Use low-quiescent current controllers, 5) Implement X-capacitor discharge circuits efficiently, 6) Optimize synchronous rectifier control for light loads. The BP3288's frequency foldback and burst mode help achieve low standby power. Every component in the standby path should be optimized - even small improvements add up to significant standby power reduction.

Follow low standby power design guidelines or contact LiTong for ultra-low standby power optimization.

Quasi-resonant (QR) controllers switch at the voltage valley, reducing switching losses compared to standard PWM hard switching. Benefits: 1) Lower switching losses - 2-5% efficiency improvement, especially at light loads, 2) Reduced EMI - softer switching transitions, 3) Lower voltage stress on MOSFET, 4) Better light-load efficiency. Trade-offs: 1) Variable switching frequency - requires careful EMI filter design, 2) More complex transformer design - must optimize for resonant operation, 3) Higher peak currents - requires MOSFETs with higher current rating. For adapters above 30W, QR is generally preferred for efficiency.

Use QR for high-efficiency adapters above 30W. Contact LiTong for QR design guidance.

QR transformer design considerations: 1) Magnetizing inductance - determines switching frequency range, 2) Turns ratio - affects output voltage range and MOSFET stress, 3) Leakage inductance - affects valley detection and snubber design, 4) Core selection - must handle flux swing without saturation. The transformer must be designed specifically for QR operation with proper consideration of resonant frequency. BPSemi provides transformer design guidelines and can recommend qualified suppliers. The transformer is the most critical component for QR performance.

Use BPSemi reference transformer designs or contact LiTong for custom transformer design support.

Thermal management requirements: 1) Primary MOSFET - typically highest loss component, requires adequate copper area or small heatsink, 2) Synchronous rectifier - significant loss at high current, needs good thermal connection to PCB, 3) Transformer - core and copper losses, ensure adequate airflow, 4) Output capacitors - ripple current causes heating, use multiple capacitors to distribute loss. Calculate power dissipation for each component and ensure junction temperatures stay within limits. For compact adapters, thermal design is critical - consider using thermally enhanced packages and copper pours for heat spreading.

Perform thermal calculations early in design. Contact LiTong for thermal design support and analysis.