SG6905

SG6905—Green Mode PFC/Flyback-PWM Controller October 2008 SG6905 Green Mode PFC/Flyback-PWM Controller Features ƒ Interleaved PFC/PWM Switching ƒ Green Mode PWM Operation ƒ Low Startup and Operating Current ƒ Innovative Switching-Charge Multiplier-Divider ƒ Average-Current-Mode Control for PFC ƒ PFC Over-Voltage and Under-Voltage Protections ƒ PFC Remote On/Off Control ƒ PFC and PWM Feedback Open-Loop Protection ƒ Cycle-by-Cycle Current Limiting for PFC/PWM ƒ Slope Compensation for PWM ƒ Constant Power Limit for PWM ƒ Power-On Sequence Control ƒ Brownout Protection ƒ Over-Temperature Protection Applications ƒ Switching Power Suppliers with Active PFC ƒ High-Power Adaptors ƒ LCD TV Applications Description The highly integrated SG6905 is specially designed for power supplies consisting of boost PFC and flyback PWM. It requires very few external components to achieve green-mode operation and versatile protections. It is available in 20-pin SOP package. The proprietary interleave-switching feature synchronizes the PFC and PWM stages and reduces switching noise. At light loads, the switching frequency is continuously decreased to reduce power consumption. For PFC stage, the proprietary multi-vector control scheme provides a fast transient response in a lowbandwidth PFC loop, in which the overshoot and undershoot of the PFC voltage are clamped. If the feedback loop is broken, the SG6905 shuts off PFC to prevent extra-high voltage on output. For the flyback PWM, the synchronize...