FSQ321: 650V Integrated Power Switch with Valley Switching control for 10Watt offline flyback converters

A Valley Switching Converter 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 valley switching operation with minimal external components. The PWM controller includes an integrated fixed-frequency oscillator, Under-Voltage Lockout, Leading Edge Blanking (LEB), optimized gate driver, internal soft-start, temperature-compensated precise current sources for loop compensation, and self-protection circuitry. Compared with discrete MOSFET and PWM controller solutions, the FSQ-series reduces total cost, component count, size and weight; while simultaneously increasing efficiency, productivity, and system reliability. This device provides a basic platform that is well suited for cost-effective designs of valley switching fly-back converters.

Features

• Optimized for Valley Switching (VSC)
• Low EMI through Variable Frequency Control andInherent Frequency Modulation
• High Efficiency through Minimum Voltage Switching
• Narrow frequency Variation Range over Wide Load andInput Voltage Variation
• Advanced Burst-Mode Operation for Low StandbyPower Consumption
• Pulse-by-Pulse Current Limit
• Various Protection functions: Over Load Protection(OLP), Over Voltage Protection (OVP), AbnormalOver Current Protection (AOCP), Internal ThermalShutdown (TSD)
• Under Voltage Lock Out (UVLO) with Hysteresis
• Internal Start-up Circuit
• Internal High-Voltage Sense FET (650V)
• Built-in Soft-Start (15ms)

Application Notes