What is a linear LED driver?

A linear LED driver is a linear regulator which often exists in packaged integrated circuits (ICs) that only need a rectified voltage source, e.g., a bridge rectifier to rectify an alternating current (AC) voltage to generate a driving voltage. Owing to their small size and low-cost, simple linear driver circuits have generated extensive interest in field of the LED lighting. Switched-mode power supplies (SMPS) may be configured to operate more efficiently than linear power supplies. Nevertheless, the SMPS creates the predetermined magnitude of DC power through a high-speed switching operation to result in much noise, thus producing interference, which detrimentally affects the adjacent circuit elements. Linear drivers have inherently low frequency content, hence eliminating the requirement of reactive (e.g., inductive and/or capacitive) input EMI/EMC filter elements. Linear LED drivers uses no electrolytic capacitor that stores sufficient energy to drive the circuits during the time periods where no line voltage power is available, and therefore extends lifetime of the LED driver and has no problem of flicker. With less parts count, smaller size, linear LED drivers facilitate a cost-effective LED driver design while eliminating the weakest link (short-life electrolytic capacitor) in a chain and reducing the total cost of ownership (TOC). LED light engines in driver-on-board (DOB) designs incorporate linear driver ICs and LED modules which dramatically reduce the form factor of LED luminaires.