Dimmable Passive Light-Emitting Diode Drivers for Smart Lampposts

Passive light-emitting-diode (LED) drivers have recently been adopted by the lighting industry in street lighting applications due to their high robustness against adverse weather conditions, long operating lifetime and high percentage of recyclable components. This paper presents a new dimmable technology for passive LED drivers, which incorporates a switchable parallel capacitor across the input current-limiting inductor. The insertion of a parallel capacitor provides a mechanism for the current circulation within the inductor-capacitor branch, which causes a zero-current condition for the diode rectifier, thus reducing the average power supplied to the LED load. The empirical model of the new dimmable passive LED system is also elucidated. A hardware prototype of a 90 W dimmable passive LED system is constructed for experimental verification.