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The AP31261 is a current mode PWM controller which is optimized for high performance, low standby power and cost effective offline flyback converters. The PWM switching frequency at normal operation is internally fixed (about 65kHz). In middle load, the IC will enter green mode to improve system efficiency with the help of frequency foldback. A minimum switching frequency (about 20kHz) is set to avoid the audible noise. In no load or light load, the IC will enter the burst mode to minimize standby power. Furthermore, the frequency dithering function is built-in to reduce EMI emission. Internal slope compensation allows more stable Peak-Current Mode control over wide range of input voltage and load conditions. Internal line compensation ensures constant output power limit over entire universal line voltage range. Comprehensive protection features are included, such as cycle-bycycle current limit (OCP), VCC Over Voltage Protection (VOVP), internal OTP, Over Load Protection (OLP) and pins’ fault protection.


  • Switching AC-DC Adapter/Charger
  • ATX/BTX Auxiliary Power
  • Set-top Box (STB) Power Supply
  • Open Frame Switching Power Supply


  • Very Low Start-up Current
  • Current Mode Control
  • Non-audible-noise Green-mode Control
  • Internal Slope Compensation
  • Soft Start During Startup Process
  • Frequency Fold Back for High Average Efficiency
  • Secondary Winding Short Protection with FOCP
  • Soft Switching for Reducing EMI
  • VCC Maintain Mode
  • Useful Pin Fault Protection:
         SENSE Pin Floating
         CTRL Pin Short to Ground
         FB/Opto-coupler Open/Short
  • Comprehensive System Protection Feature:
         VCC Over Voltage Protection (VOVP)
         Over Load Protection (OLP)
  • Mini Size Package of SOT26
  • Pin to Pin Compatible with AP3125A/V/R/L
  • Totally Lead-free & Fully RoHS Compliant
  • Halogen and Antimony Free. “Green” Device

Product Specifications

Product Parameters

HV Start-Up Circuit No
Startup Current 1 µA
UVLO Threshold on/off 15.8/7.6 V
Gate Output Current 350 mA
Oscillation Frequency 65 kHz
CTRL Pin Low Latch
CTRL Pin High Auto-Recover
VOVP Auto-Recover

Related Content

SOT26 (SC74R)

Technical Documents

Recommended Soldering Techniques


Orderable Part Number Authorized Distributor Quantity Inventory Date Buy Online Region
AP31261KTR-G1 Digi-Key Electronics 2629 8/8/2020 Buy Now United States


Product Change Notices

PCN # Issue Date Subject
PCN-2246 2017-06-28 Additional Qualified Assembly/Test (A/T) Site – Chengdu A/T (CAT) with Part Marking Update