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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.
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
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)