M. Fernández

1. High-efficiency AHB for LED streetlightingFeedforward and self-driven synchronous rectification in the asymmetrical half bridge M. Fernández This poster proposes the AHB converter as the second stage for a LED driver in which the key points of the design are reliability and efficiency. The first one implies not using electrolytic capacitors so the low frequency ripple cannot be neglected. To solve this problem a feedforward technique is used. Due to the low output voltage, a specifically-designed synchronous rectification is mandatory to achieve high efficiency. GOALS OF THE SYSTEM Requirements Proposedtopology Maintasks • First stage (Boost BCM): • Power Factor Correction (η=97%) • No electrolytic capacitors • Second stage (AHB): • Galvanic isolation • Output regulation • No electrolytic capacitors • High efficiency • High reliability • Galvanic Isolation • Input voltage range 90-305 Vac • 60 W (12 V / 5 A) Grupo de Sistemas Electrónica de Alimentación Project sponsoredby FEEDFORWARD Relationship between Vg and Vo is non linear SELF-DRIVEN SYNCHRONOUS RECTIFICATION VGS(S3) and VGS(S4) are not inside the desired limits with the SR conventional method Reduction of losses because only CGS(S3) and CGS(S4) are fully charged/discharged in each switching cycle EXPERIMENTAL RESULTS CONCLUSIONS • The proposed feedforward technique makes possible the design of a slow control loop to achieve stability while cancelling the low frequency ripple due to the absence of electrolytic capacitors. • Self-driven synchronous rectification reduces losses, working perfectly under all conditions of the converter. • AHB converter efficiency = 94.6% (Boost converter efficiency = 97%)  92.42% overall efficiency.