Analysis and design of the quadratic buck-boost converter as a high-power-factor driver for power-LED lamps

In this paper the quadratic buck-boost (QBB) converter is proposed as a high-power-factor off-line power supply for power-LED lamps. The QBB converter features just one controlled switch and two inductors and is able to supply a solid-state lamp from the mains providing high power factor and good efficiency. In the paper, the QBB converter is analyzed and a design methodology is proposed. It is demonstrated that with a careful design of the converter, the filter capacitances can be made small enough so that film capacitors may be used. In this way, the converter mean time between failures (MTBF) can be made as high as that of the solid-state lamp. A design example for a 70 W converter supplied from a 230 V/50 Hz mains for street lighting applications is shown. Finally, experimental results from a laboratory prototype are also presented.