Description
LC5540LF series is a quasi-resonant topology switching power supply IC, designed for input capacitorless applications, and making it possible for systems to comply with the harmonics standard (IEC61000-3-2 class C). It incorporates separate controller and power MOSFET chips. The controller adapts the average current control method for realizing high power factors, and the quasi-resonant topology contributes to high efficiency and low EMI noise. The rich set of protection features helps to realize low component counts, and high performance-to-cost power supply.

FEATUREs and Benefits
• Integrated on-width control circuit (it realizes high power factor by average current control)
• Integrated startup circuit (no external startup circuit necessary)
• Integrated soft-start circuit (reduces power stress during start-up on the incorporated power MOSFET and rectifier)
• Integrated bias assist circuit (improves the startup performance, suppresses VCC voltage droop during operation, allows reduction of VCC capacitor value as well as use of a ceramic capacitor)
• Integrated Leading Edge Blanking (LEB) circuit
• Integrated maximum on-time limit circuit
• Dual-chip structure, with an avalanche-guaranteed power MOSFET (allows simplified surge suppressing circuits)
• Protection features:
▫ Overcurrent protection (OCP): pulse-by-pulse
▫ Overvoltage protection (OVP): latched shutdown
▫ Overload protection (OLP): latched shutdown
▫ Thermal shutdown (TSD): latched shutdown

APPLICATIONs
• LED lighting fixtures
• LED light bulbs