18W High-Efficiency Adapter Solution

Application

Description

Complete 18W adapter solution featuring PN8147 flyback controller with synchronous rectification

Core Advantages

Quasi-Resonant Operation QR operation reduces switching losses and improves efficiency across the load range
Synchronous Rectification SR controller improves efficiency at 5V output by 3-4% compared to diode rectification
Built-in Frequency Dithering Frequency dithering reduces EMI and helps meet EMC requirements with simpler filtering
Automatic Burst Mode Burst mode operation achieves ultra-low standby power below 50mW
High Integration Integrated 700V MOSFET and comprehensive protections reduce external component count

Recommended Bill of Materials (BOM)

Item Part Number Description Quantity Datasheet
1 📄 Download
2 📄 Download
3 📄 Download

Applications

Smartphone chargers
Tablet chargers
Portable device power supplies
Consumer electronics adapters

Technical Specifications

Input Voltage
90-264VAC
Output
5V/3.6A
Max Power
18W
Efficiency
>87%
Standby Power
<50mW
Operating Temperature
0°C to +50°C

Customer Success Stories

Consumer Electronics OEM

Consumer Electronics |

Challenge

Needed compact 18W adapter with high efficiency and low standby power for smartphone charger

Solution

Implemented PN8147+PN8307 solution with optimized transformer design

Results

Achieved 88% efficiency and 45mW standby power. Passed all safety certifications. Reduced BOM cost by 15% compared to previous design.

Power Adapter Manufacturer

Power Supplies |

Challenge

Needed to upgrade 15W adapter design to meet new efficiency regulations

Solution

Redesigned with PN8147+PN8307 solution and optimized transformer

Results

Efficiency improved from 82% to 88%, meeting latest DoE requirements. Thermal performance improved significantly.

FAE Expert Insights

S

Senior FAE

Applications Engineer

10+ years

Professional Insights

This 18W adapter solution is one of my most recommended designs for cost-sensitive consumer applications. The PN8147's high integration level significantly reduces component count while the PN8307 SR controller delivers 3-4% efficiency improvement over diode rectification. Key design considerations: 1) Transformer design is critical - use proper winding technique to minimize leakage inductance. 2) For EMI, place the Y capacitor close to the transformer and use proper shielding. 3) The SR MOSFET selection should consider Rds(on) vs. gate charge for optimal efficiency. 4) Thermal design requires adequate copper area for the primary MOSFET drain pin.

Key Takeaways

  • Transformer design is the most critical factor for efficiency and EMI
  • SR MOSFET selection balances conduction loss vs. switching loss
  • Proper snubber design protects the MOSFET and reduces EMI
  • PCB layout significantly affects thermal performance
  • Burst mode optimization achieves lowest standby power

Decision Framework

Steps:
  1. Evaluate power requirements and input voltage range
  2. Select appropriate controller and synchronous rectifier solution
  3. Design optimized transformer parameters
  4. Complete PCB layout and thermal design
  5. Conduct EMI testing and efficiency optimization

Ready to Implement This Solution?

Contact our FAE team for design support and quotes

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Frequently Asked Questions

What is the typical efficiency across load range?

Efficiency is typically 88% at full load, 85% at 50% load, and 82% at 25% load. Light load efficiency in burst mode maintains >75% down to 10% load. For more detailed information and application guidance, please consult the product datasheet or contact our technical support team.

Monitor efficiency across your typical load range for optimization.

How do I modify the output voltage?

Output voltage is set by the TL431 reference and resistor divider. Change the feedback resistor ratio to adjust output voltage. Ensure output capacitors are rated for the new voltage. For more detailed information and application guidance, please consult the product datasheet or contact our technical support team.

Recalculate feedback divider and verify capacitor ratings.

What modifications are needed for different output power?

For different power levels: 1) Select appropriate PN8xxx controller based on power rating. 2) Resize transformer core and wire gauge. 3) Adjust output capacitor quantity based on ripple requirements. 4) Verify thermal design for new power level.

Contact FAE for power level modification guidance.

How do I meet conducted EMI requirements?

Key EMI design points: 1) Use proper input filter with X and Y capacitors. 2) Minimize primary switching loop area. 3) Add shielding winding in transformer if needed. 4) Use frequency dithering feature. 5) Optimize snubber design.

Follow EMI design guidelines and conduct pre-compliance testing.

Can this design be used for 12V output?

Yes, with modifications: 1) Adjust transformer turns ratio for 12V output. 2) Change output capacitor voltage rating to 16V or 25V. 3) Adjust feedback divider resistors. 4) Verify SR MOSFET voltage rating is adequate.

Modify transformer ratio and component ratings for 12V output.