• Less than 75mW Standby Power
  • Proprietary "η-BalanceTM" to boost light load efficiency
  • Proprietary "zero OCP/OPP recovery gap" control
  • Built-in soft start function
  • Programmable OLP Debounce Time
  • Proprietary "Audio Noise Free OCP Compensation"
  • Frequency Reduction and Burst Mode Control for Energy Saving
  • Programmable switching frequency
  • Current Mode Control
  • Built-in Frequency Shuffling
  • Cycle-by-Cycle Current Limiting
  • Built-in Leading Edge Blanking (LEB)
  • Constant Power Limiting
  • Audio Noise Free Operation
  • 运用

    Offline AC/DC Flyback Converter for
  • AC/DC Adaptors
  • Open-frame SMPS
  • Set-Top Box Power Supplies
  • ATX Standby Power
      • SF5533 is a high performance, high efficiency, low cost, highly integrated current mode PWM controller for offline flyback converter applications. 
        PWM switching frequency with shuffling is externally programmable, which can reduce conduction EMI emission of a power supply. When the output power demands decrease, the IC automatically decreases switching frequency based on the proprietary η-BalanceTM control to boost Power conversion efficiency at the light load. When the current set-point falls below a given value, e.g. the output power demand diminishes, the IC enters into burst mode and provides excellent efficiency without audio noise.
        SF5533 can achieve "Zero OCP/OPP Recovery Gap" using SiFirst's proprietary control algorithm. Meanwhile, the OCP/OPP variation versus universal line input is compensated. The IC has built-in synchronized slope compensation to prevent sub-harmonic oscillation at high PWM duty output. The IC also has built-in soft start function to soften the stress on the MOSFET during power on period.  
        SF5533 integrates functions and protections of Under Voltage Lockout (UVLO), VCC Over Voltage Protection (OVP), Cycle-by-cycle Current Limiting (OCP), All Pins Floating Protection, Over Load Protection (OLP), RT Pin Short-to-GND Protection, Gate Clamping, VCC Clamping, Leading Edge Blanking (LEB). 
        SF5533 is available in SOT23-6, DIP-8 packages.