LC5540LD Series: Single-Stage Power Factor Corrected Off-Line Switching Regulators

LC5540LD 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.

The LC5540LD devices are intended for isolated designs. The incorporated MOSFET has a VDSS(min) rating from 650 V (LC5545LD and LC5546LD) to 800 V (LC5548LD). The RDS(on)(max) is 1.9 Ω (LC5546LD) to 3.95 Ω (LC5545LD). It is capable of a maximum output power of 20 W on 230 VAC supply to 16 W on universal supply (LC5546LD) based on the thermal rating. Note that the maximum output power can be up to 120% to 140% of this value. However, it may be limited in applications with low output voltage or short duty cycle.


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  • 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

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Product Image Functional Block Diagram Typical Application

Part Number Specifications and Availability

Part Number Package Type Temperature RoHS
Part Composition /
RoHS Data
Comments Samples Check
Distributor Stock
LC5545LD 8-lead DIP -20°C to 85°C Yes View Data New Contact your
local sales rep
Check Stock
LC5546LD 8-lead DIP -20°C to 85°C Yes View Data New Contact your
local sales rep
Check Stock
LC5548LD 8-lead DIP -20°C to 85°C Yes View Data New Contact your
local sales rep
Check Stock

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