A Novel Design Approach for LLC Resonant Converters in Off-line LED Driving Applications

• Published in: Journal of control, automation & electrical systems automation & electrical systems, 2021-12, Vol.32 (6), p.1758-1770
• Main Authors: Ferraz, Ruan M., Resende, Lucas H. G., Braga, Henrique A. C., Almeida, Pedro S., Alonso, J. Marcos, Soares, Guilherme M.
• Format: Article
• Language: English
• Subjects: Algorithms; Control; Control and Systems Theory; Converters; Design analysis; Design engineering; Design parameters; Electrical Engineering; Energy conversion efficiency; Engineering; Mechatronics; Numerical models; Power supplies; Ripples; Robotics; Robotics and Automation
• ISSN: 2195-3880; 2195-3899
• DOI: 10.1007/s40313-021-00793-y

This work presents an analysis and a design methodology for a DC–DC LLC resonant converter applied to off-line LED driving. An investigation regarding the main design parameters that influence the LED low-frequency (LF) ripple has been carried out. The study was based on a mathematical analysis of the converter and employs numerical algorithms to solve a set of equations that accurately describe the converter behavior. Based on this analysis, a novel design methodology that allows for LF current ripple prediction has been devised. A numerical model has been developed to determine the LF current ripple transmission in DC–DC LLC resonant converters and provide a methodology for designing the bus capacitance in two-stage off-line LED power supplies. The work shows that the design of the LLC resonant converter for off-line LED driving is a trade-off between the converter efficiency and the LF ripple transmission. Experimental results were taken from two 46-W laboratory prototypes considering two different design goals: one for LF ripple reduction and another aiming at the highest converter efficiency and better power quality. Furthermore, the design of a two-stage LED driver based on an LLC converter taking into account the LF ripple transmission is also presented.