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  3. onsemi — NCP1945 CrM Boost PFC and QR Flyback Controller

onsemi — NCP1945 CrM Boost PFC and QR Flyback Controller

 

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onsemi NCP1945 CrM Boost PFC and QR Flyback Controller

High efficiency power conversion for compact USB PD and offline designs

onsemi NCP1945 combines power factor correction and quasi-resonant flyback control in a single IC to simplify high performance off-line power supply designs. Balancing efficiency, power density, and compliance across varying load conditions can be complex.

This solution streamlines that challenge by integrating CrM PFC with advanced frequency foldback and QR control techniques that maintain efficiency from full load down to light load operation.

The device supports near unity power factor while minimizing switching losses through valley synchronized frequency foldback and adaptive operating modes. Its QR flyback section enhances efficiency at high frequencies and smoothly transitions into skip operation for light load conditions, helping improve thermal performance and meet stringent energy standards.

Features

  • Integrated CrM boost PFC and quasi resonant flyback controller
  • Valley Synchronized Frequency Fold-back for improved light load efficiency
  • Near unity power factor performance
  • High frequency QR operation up to 500 kHz
  • Valley lockout for stable operation down to the 6th valley
  • Auto tuning skip mode for optimized light load behavior
  • Power Excursion Mode up to 2x output capability
  • Adaptive gate drive for improved switching performance
  • Constant output current limit independent of output voltage
  • 150 V wide range VCC architecture
  • Built in protections including
    • Brownout detection
    • Non dissipative overpower protection
    • Latched over voltage protection
    • Overtemperature protection via NTC
    • Line removal detection with X2 capacitor discharge

Applications

  • Off-line power supplies
  • USB Power Delivery adapters
  • USB Type-C chargers
  • High density AC-DC adapters
  • Industrial power supplies
  • LED drivers

NCP1945 Typical Application Circuit

Typical Application Circuit

 

onsemi — NCP1945 CrM Boost PFC QR Flyback Controller

 

Reference Design

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TND6511/D

The onsemi TND6511/D Evaluation Module (EVM) is a 140 W USB Power Delivery 3.1 (PD3.1) Extended Power Range reference design for high-performance USB-C chargers, notebook adapters, and other compact AC-DC power supplies. It operates from a universal 90 VAC to 264 VAC input and provides programmable outputs from 5 V to 28 V, delivering up to 140 W of power. The design is built around the NCP1945 PFC controller, enabling efficient power factor correction and supporting the latest fast-charging requirements.

The TND6511/D combines a Critical Conduction Mode (CrM) PFC stage controlled by the NCP1945 with a two-switch quasi-resonant flyback topology, utilizing onsemi's advanced controllers and GaN power devices to achieve high efficiency, low standby power, and high power density. The EVM also incorporates comprehensive protection features, including OVP, OCP, SCP, and OTP, and is supported by complete design documentation such as schematics, PCB layouts, magnetic specifications, and BOM data, making it an excellent platform for evaluating and accelerating next-generation USB PD3.1 power supply designs.

Reference Design ↗

onsemi — TND6511/D Reference Design
🔍 Reference Design