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A Two Stage Buck Boost Converter With Isolation As A High Power Factor Supply For Power-LED Lamps

Lekshmi Sasidharan, Jeneesh Scaria

In recent years, power converters are used to get high power factor for low power applications. In this work, the design and development of a DC-DC Converter using two stage buck–boost converter with isolation operation as high-power-factor offline power supply for power-LED lamps is discussed. This converter is suitable for low power application such as a matrix LED lighting system. The advantage of this converter is that instead of using two controlled switches as in case of a conventional converter, this circuit uses one MOSFET as a switch. The circuit uses two inductors and two capacitors as energy transferring elements that are able to provide a good quality, high efficiency power supply to the load. The design of this converter is simulated with closed loop control using a PI controller circuit. The main feature of this circuit is that have a galvanic isolation between the load and the source. Thus, by a suitable controller and galvanic isolation, the ripple magnitude in the output is reduced considerably. A design example for a 70-W converter supplied from a 230 V/50 Hz mains for street lighting applications is shown. Simulation results demonstrate that the power factor of the closed-loop proposed converter is 0.993 and the output voltage of the designed controller can be stably maintained at 200V. The experimental results are shown to substantiate this design. This converter is used to provide power factor correction in streetlight application. The simulation studies using MATLAB/Simulink is also presented.