Description A Quasi-Resonant Converter (QRC) generally shows lower EMI and higher power conversion efficiency than a conventional hard-switched converter with a fixed switching frequency. The FSQ-series is an integrated Pulse-Width Modulation (PWM) controller and SenseFET specifically designed for quasi-resonant operation and Alternating Valley Switching (AVS). The PWM controller includes an integrated fixed-frequency oscillator, Under-Voltage Lockout (UVLO), Leading Edge Blanking (LEB), optimized gate driver, internal soft start, temperature-compensated precise current sources for a loop compensation, and self-protection circuitry. Compared with a discrete MOSFET and PWM controller solution, the FSQ-series can reduce total cost, component count, size, and weight; while simultaneously increasing efficiency, productivity, and system reliability. This device provides a basic platform for cost-effective designs of quasi-resonant switching flyback converters. Features ■ Optimized for Quasi-Resonant Converters (QRC) ■ Low EMI through Variable Frequency Control and AVS (Alternating Valley Switching) ■ High-Efficiency through Minimum Voltage Switching ■ Narrow Frequency Variation Range over Wide Load and Input Voltage Variation ■ Advanced Burst-Mode Operation for Low Standby Power Consumption ■ Simple Scheme for Sync Voltage Detection ■ Pulse-by-Pulse Current Limit ■ Various Protection Functions: Overload Protection (OLP), Over-Voltage Protection (OVP), Abnormal Over-Current Protection (AOCP), Internal Thermal Shutdown (TSD) with Hysteresis, Output Short Protection (OSP) ■ Under-Voltage Lockout (UVLO) with Hysteresis ■ Internal Startup Circuit ■ Internal High-Voltage Sense FET (650V) ■ Built-in Soft-Start (17.5ms) Applications ■ Power Supply for LCD TV and Monitor, VCR, SVR, STB, and DVD & DVD Recorder ■ Adapter
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