Non-Electrolytic Capacitor LED Driver with Feed-Forward control

Abstract

In this thesis a non-electrolytic capacitor LED driver with feed-forward control is proposed It includes an AC-DC PFC converter and a DC-DC LLC resonant converter Typically the output of the AC-DC converter is a DC bus voltage with 120 Hz ripple and this ripple will cause high current ripple on the LED load Therefore the electrolytic capacitor (E-cap) is used to reduce the output current ripple But the use of the E-cap will lead to the shorter lifetime of the lighting system In this thesis an analog feed-forward control is proposed to reduce the output current ripple In this control the 120 Hz ripple signal acts as feed-forward signal This signal can be used to modulate the switching frequency of the LLC resonant converter to reduce the output current ripple Finally the hardware prototype with an input voltage of 90~264 VRMS output voltage of 43 V and constant output current of 3 5 A/150 W is implemented to verify the proposed control schemes and the feasibility of the system Under universal input voltage range the output current ripple is below 25 % without electrolytic capacitor and the power factor is higher than 0 97 and the highest efficiency is 90 % which meets the IEC 61000-3-2 Class C standard requirements Moreover there is no visible flicker in the LED light output

Date of Award	2014 Aug 2
Original language	English
Supervisor	Tsorng-Juu Liang (Supervisor)