FSQ0765RS: 650V Integrated Power Switch with Quasi-Resonant Operation for 70Watt offline flyback converters

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), Internal
• Thermal Shutdown (TSD) with Hysteresis,
• Output Short Protection (OSP)
• Under-Voltage Lockout (UVLO) with Hysteresis
• Internal Startup Circuit
• Internal High-Voltage Sense FET (650 V)
• Built-in Soft-Start (17.5 ms)

Application Notes