The SG6931DZ is a quasi-resonant (QR) PWM controller from Fairchild/ON Semiconductor, designed for high-performance offline flyback converter applications. This controller is optimized for achieving high efficiency, low EMI, and low standby power consumption in adapters, chargers, and other power supplies. It leverages quasi-resonant operation to minimize switching losses and improve overall system performance.

Applications

• AC/DC Adapters for consumer electronics (laptops, gaming consoles)
• Battery Chargers for mobile devices (smartphones, tablets)
• LED Lighting Power Supplies
• Auxiliary Power Supplies for industrial equipment
• Open-frame SMPS

Features

• Quasi-Resonant (QR) Operation: Reduces switching losses and improves efficiency.
• Valley Switching: Minimizes voltage stress on the MOSFET.
• Low Startup Current: Minimizes power consumption during startup.
• Frequency Foldback: Improves efficiency at light loads.
• Over-Temperature Protection (OTP): Protects the device from overheating.
• Over-Voltage Protection (OVP): Prevents damage from excessive output voltage.
• Over-Current Protection (OCP): Limits the output current to protect the device and load.
• Under-Voltage Lockout (UVLO): Ensures proper operation during startup and prevents erratic behavior.
• Open-Loop Protection (OLP): Protects the power supply from damage in case of feedback loop failure.
• Soft-Start Function: Reduces stress on components during startup.

Benefits

• High Efficiency: Quasi-resonant operation minimizes switching losses.
• Low EMI: Valley switching reduces electromagnetic interference.
• Compact Design: Reduces board space requirements.
• Enhanced Reliability: Comprehensive protection features ensure robust operation.
• Simplified Design: Fewer external components required.
• Cost-Effective Solution: Reduces overall system cost.
• Low Standby Power Consumption: Meets stringent energy efficiency standards.

Additional Details

The SG6931DZ operates by switching the MOSFET at the valley of the drain-source voltage, minimizing switching losses and improving efficiency. The frequency foldback feature reduces the switching frequency at light loads, further improving efficiency. The controller is available in various packages, including DIP and SOP. The datasheet contains detailed specifications regarding voltage ranges, current limits, and switching frequencies.