TITLE:
Integrated Off-Line Ballast for High Brightness LEDs with Dimming Capability
AUTHORS:
Jorge Garcia, Antonio J. Calleja, Emilio L. Corominas, David Gacio, Lidia Campa, Ramón E. Díaz
KEYWORDS:
High Brightness LEDs, Light Dimming, Electrolytic Capacitor Avoidance, Integration of Stages
JOURNAL NAME:
Circuits and Systems,
Vol.2 No.4,
October
17,
2011
ABSTRACT: This paper presents an off-line integrated full ballast to supply a 35W assembly of Power LEDs. The proposed solution integrates an input PFC stage (a flyback converter operating in DCM) and a DC-DC output converter (a buck converter) into a single switch power stage, operating with peak current control. As it will be shown, this control scheme maintains the current through the load constant, regardless of the instantaneous value of the DC link voltage. This issue allows the use of a small capacitor for the DC link, which enhances the overall system reliability. The complete ballast has full dimming capability, and all the analysis and design steps are presented, thus ensuring the fulfilling of the existing regulations. The novelty of the final solution comes from the simplicity and robustness of the control scheme in an integrated compact single-switch power stage. A final prototype of the ballast has been built and tested, and experimental results are shown in the last part of the paper. Finally, conclusions and future developments are shown.