Active Clamp Flyback (ACF) Controller Combines Industry’s Highest Integration and Operational Efficiency with Ultra-Low No-Load Power

SZ1131 33W to 100W

The latest addition to Silanna’s family of CO2 Smart Power™ technologies addresses the ultimate power management challenge facing engineers by simplifying design and improving performance while meeting environmental sustainability goals through more efficient energy use. 

The SZ1131 provides the ease-of-design of a simple flyback controller with all the benefits of an ACF design, including recycling the leakage inductance energy of the flyback transformer and limiting the primary FET drain voltage spike during turn-off events. 

Employing Silanna Semiconductor’s OptiMode™ digital control architecture, the SZ1131 adjusts its mode of operation on a cycle-by-cycle basis to maintain high efficiency, low EMI, fast dynamic load regulation, and other key power supply parameters in response to varying line voltage and load. Efficiencies of up to 95% across universal (90Vac – 265Vac) input voltages and varying loads combine with ultra-low no-load power of less than 20mW up to 65W to significantly reduce overall energy consumption.

The SZ1131 integrates an adaptive digital PWM controller, an active clamp FET, active clamp gate driver and a startup regulator. Built-in protection against over-temperature, over-voltage, over-current, over-power and short circuit conditions as well as transformer core saturation faults further reduces the need for external components.

Vin=265 Vac, Vout=20 V, Lout=3.25 A, Vds_pri (max) = 551 V Vds_sec (max) = 95 V

Vin=265 Vac, Vout=20 V, Lout=3.25 A, Vds_pri (max) = 551 V Vds_sec (max) = 95 V

Key Features:

  • Integrated UHV active clamp FET, active clamp driver and start-up regulator
  • Capable of over 95% efficiency
  • Flat efficiency across universal (90Vac to 265Vac) input voltage and load
  • < 20mW system no-load power consumption
  • OptiMode™ cycle-by-cycle adaptive digital control
  • Self-tuning valley mode switching (VMS)
  • Multi-mode operation (burst mode, QR, VMS)
  • > 6 dB EMI margin
  • OTP, OVP, OCP, OPP, output short circuit and transformer saturation protection
  • Up to 65W output power with universal input and 100W+ output power with front-end PFC
  • 16-pin SOIC package
  • CO2 Smart Power™ by Silanna Semiconductor


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