Diodes Incorporated

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QR/CCM Operation

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The AP3301 is a peak-current control, Quasi-Resonant (QR) PWM controller which is optimized for high performance, low standby power and cost effective offline flyback converters.

At no load or light load, the IC will enter the burst mode to minimize standby power consumption. The minimum switching frequency (about 20kHz) is set to avoid the audible noise. At medium load, the IC will enter valley lock QR mode with frequency foldback to improve system efficiency and EMI performance. The maximum switching frequency (about 120kHz) is set to clamp the QR frequency to improve efficiency. At low line input & heavy load, when switching frequency decreases below 62KHz with output load increasing, the IC will enter CCM mode with fixed switching frequency of 62kHz to optimize low line power conversion efficiency. 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 piecewise linear line compensation ensures constant output power limit over entire universal line voltage range.

Comprehensive protection features are included, such as brown out protection, cycle-by-cycle current limit (OCP), VCC Over Voltage Protection (VOVP), Secondary-Side Output OVP (SOVP), internal OTP, Over Load Protection (OLP) and pins’ fault protection.


  • Very Low Start-up Current
  • Multi-Mode Control
  • Quasi-Resonant Operation with Valley Lock
  • Fixed Frequency CCM Operation at Low Line Heavy Load
  • Non-Audible-Noise Quasi-Resonant Control
  • Internal Slope Compensation
  • Soft Start During Startup Process
  • Frequency Fold Back for High Average Efficiency
  • Secondary Winding Short Protection with FOCP
  • Frequency dithering for Reducing EMI
  • VCC Maintain Mode
  • Useful Pin Fault Protection: SENSE Pin Floating, FB/Opto-coupler Open/Short
  • Comprehensive System Protection Feature: VCC Over Voltage Protection (VOVP), Over Load Protection (OLP)
  • Brown Out Protection (BNO)
  • Secondary Side OVP (SOVP)
  • Mini Size Package of SOT26
  • Totally Lead-free & Fully RoHS Compliant
  • Halogen and Antimony Free. “Green” Device


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

Product Specifications

Product Parameters

Operation Mode QR/CCM
HV Start-UpCircuit N/A
Vcc_MAX(V) 30
UVLOThresholdon/off (V) 15.5/7.6 V
Gate OutputCurrent (mA) -1 mA
Maximum OscillationFrequency (kHz) 62 (CCM mode)/120 (QR mode) kHz
BNO Auto-Recover
Release Date 201606

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