The SG6741SZ is a highly integrated Quasi-Resonant (QR) PWM controller from Fairchild Semiconductor, now ON Semiconductor. This device is designed for high-performance, low standby power offline flyback converter applications. It optimizes performance for adapter and charger applications.

Applications

• AC/DC adapters for laptops and notebooks
• Power supplies for LCD TVs and monitors
• Offline power supplies for set-top boxes
• Battery chargers
• Auxiliary power supplies

Features

• Quasi-Resonant (QR) operation for high efficiency and low EMI
• Valley switching operation for reduced switching losses
• Low startup current
• Built-in soft-start function
• Frequency hopping to reduce EMI emissions
• Over-voltage protection (OVP)
• Over-temperature protection (OTP)
• Overload protection (OLP)
• Short-circuit protection (SCP)
• Adjustable switching frequency
• Leading-edge blanking

Benefits

• High efficiency minimizes power loss and reduces heat dissipation
• Low EMI simplifies system design and reduces compliance costs
• Comprehensive protection features enhance system reliability and prevent damage
• Reduced component count lowers BOM (Bill of Materials) cost
• Improved light-load efficiency reduces standby power consumption

Additional Details

The SG6741SZ utilizes valley switching operation in QR mode to minimize switching losses and improve efficiency. The integrated features of QR operation also contribute to reduced EMI emissions. The built-in soft-start function minimizes stress on the power components during startup. The frequency hopping function further reduces EMI by spreading the energy over a broader frequency range. The comprehensive protection features, including OVP, OTP, OLP, and SCP, provide robust system protection. The adjustable switching frequency allows for optimization of the power supply design. The device exhibits a low startup current, which contributes to improved efficiency. The SG6741SZ delivers excellent performance and reliability within a compact package. It is commonly deployed in applications where high efficiency, minimal EMI, and robust protection are paramount. Effective thermal management is crucial for ensuring reliable operation. Detailed application notes and design resources are readily available from ON Semiconductor.