Multiplier-Less PFC Controller Boosts Energy Efficiency in Consumer Apps
The L6462A transition-mode (TM) power-factor-correction (PFC) controller cuts bill-of-materials costs while enhancing efficiency. As a result, consumer products and power supplies up to 250 W can meet stringent eco-design standards in high-end battery chargers, power adapters, and power supplies for domestic and consumer products like flat-panel televisions and lighting drivers.
The controller, developed by STMicroelectronics, uses a current generator and shaper to produce a sinusoidal reference instead of a conventional voltage sensor and analog multiplier, permitting boost-PFC converters without external voltage-divider components. This allows it to coordinate the PFC conversion cycles by sensing inductor demagnetization via the gate-driver output. Hence, it requires no auxiliary inductor winding or interface components.
The L6462A’s totem-pole output delivers up to +600/-300 mA to directly drive external boost-converter MOSFETs. It can operate on a wide AC input-voltage range, from 90 to 264 V, and is typically designed to deliver a 400-V output voltage. An enhanced error amplifier and high-accuracy voltage reference sharpen dynamic response to large-load transients and prevent excessive output overshoots or undershoots.
At full load, the L6462A operates in quasi-resonant mode (valley switching) to minimize power dissipation. As the load is reduced, valley skipping progressively lowers the operating frequency to maintain efficiency. In addition, the controller has a deep burst-mode threshold that ensures smooth dimming in LED-lighting applications.
The innovative current shaping and demagnetization sensing minimizes total harmonic distortion (THD) and enhances efficiency, particularly at intermediate and light loads where its idle current is below 60 µA.
Designers can evaluate the L6462’s features using the EVL6462A-250W-M demonstration board and an accompanying application note, AN6380, which describes the board’s operating modes and performance measurements.
The controller, housed in a SOT23-6L package, is in production now, priced at $0.18 for orders of 1.000 pieces.
Visit https://www.st.com/l6462a for more information.
About the Author
Lee Goldberg
Contributing Editor
Lee is the author of the popular PowerBites series.
Lee Goldberg is a self-identified “Recovering Engineer,” Maker/Hacker, Green-Tech Maven, Aviator, Gadfly, and Geek Dad. He spent the first 18 years of his career helping design microprocessors, embedded systems, renewable energy applications, and the occasional interplanetary spacecraft. After trading his ‘scope and soldering iron for a keyboard and a second career as a tech journalist, he’s spent the next two decades at several print and online engineering publications.
Lee’s current focus is power electronics, especially the technologies involved with energy efficiency, energy management, and renewable energy. This dovetails with his coverage of sustainable technologies and various environmental and social issues within the engineering community that he began in 1996. Lee also covers 3D printers, open-source hardware, and other Maker/Hacker technologies.
Lee holds a BSEE in Electrical Engineering from Thomas Edison College, and participated in a colloquium on technology, society, and the environment at Goddard College’s Institute for Social Ecology. His book, “Green Electronics/Green Bottom Line - A Commonsense Guide To Environmentally Responsible Engineering and Management,” was published by Newnes Press.
Lee, his wife Catherine, and his daughter Anwyn currently reside in the outskirts of Princeton N.J., where they masquerade as a typical suburban family.