Modelling and control of an optimized cascade structure for LED street lighting fixtures

This paper presents a converter structure applied to supply high power Light Emitting Diodes (LEDs) from the mains in a street lighting system, based on the Reduced Redundant Power Processing (R²P²) principle. It is used a Buck-Boost operating in Discontinuous Conduction Mode (DCM) as Power Factor Corrector (PFC) to guarantee high power factor and low current harmonic injection to the mains. The second converter of the structure works only to control the current through the LED array. Because LED have a voltage source behaviour, only part of the rated power needs to be processed twice to regulate the output current. The system modelling and control structure are shown in detail. A laboratory prototype, with a rated power of 75W for a rated input voltage of 220V_rms, was built to show the feasibility of the idea.