Off-the-line primary-side regulation LED lamp driver with single-stage PFC and TRIAC dimming using LED forward-voltage and duty-variation tracking control

Non-isolation LED drivers [1] are more attractive than isolated drivers in terms of efficiency and lower fabrication cost. However, some areas such as bar-typed fluorescent lamp retrofit applications still require a solution with isolation. Even for replacement of the incandescent and compact fluorescent lamps, some LED lamp makers prefer isolated driver solutions due to safety issues. One of the popular solutions is the flyback converter which is widely used in low-to-moderate power applications [2]. However, generally, it requires secondary voltage or current-sense circuit, and opto-coupler isolator to form a feedback loop. Thus, primary-side regulation (PSR) flyback converters have been steadily used in LED applications since they do not need secondary circuits and isolator [3]. This paper introduces a PSR method for LED lamp which satisfies low price, good efficiency, high power factor (PF) and triode AC switch (TRIAC) dimming control.