Allegro MicroSystems, Inc. Introduces New Single Stage Off-Line LED Driver IC Series
The LC5540LD/LF series are quasi-resonant topology switching power supply ICs, designed for input capacitorless applications making it possible for systems to comply with the harmonics standard (IEC61000-3-2 class C). These devices incorporate 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 the 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.
These devices are intended for isolated designs. The incorporated MOSFET has a VDSS(min) rating from 650 V (LC5545LD, LC5546LD, LC5546LF, and LC5547LF,) to 800 V (LC5548LD and LC5549LF). The RDS(on)(max) is 1.1 Ω (LC5547LF), 1.9 Ω (LC5546LD and LC5546LF,) and 3.95 Ω (LC5545LD). These devices are capable of a maximum output power of 20 to 80 W on a 230 VAC supply to 16 W (LC5546LD) to 55 W (LC5547LF) on a universal supply 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.
This series is available in the DIP8 and TO220 packages that have been designed to protect the IC and overall system from excessive heat. Similar competitive designs on the market cannot easily detect the power MOSFET rising temperatures.