Quadratic Buck-Boost Single Switch Converter inLow Power SSL Applications:Pros and Cons Analysis

Inhalt:
The Quadratic Buck-Boost (QBB) insulated topology is a single switch converter where the switch is shared between two cascaded semi-stages: the first semi-stage is a buck-boost acting as an input active PFC stage, the second one is aninsulated Flyback stage. The biggest advantage of this topology is its ability to achieve high control bandwidth, keeping low both the input current distortion and the output low-frequency ripple, with an easy control strategy. In this paper the QBB converter is briefly analyzed, and an insulated design is proposed for a low-cost LED driver. However, with the aid of a prototype it will be shown that when the power converter is designed for the Universal ac range (88-264 V), the topology has somedrawbacks that will be analyzed in this paper, and that limit its usage in low power applications. Finally, designing the converter for the European ac range, a compromise is found.