One Cycle Control of Bridgeless Buck Converter
Analysis and design of a voltage doubler bridgeless buck converter is performed during the course of project and hardware implementation of a prototype was done during this period. Voltage doubler bridgeless buck converters can be used in switched mode power supplies as rectification as well as power factor correction circuit. Conventional switched mode power supplies contains a bridge rectifier followed by power factor correction circuit and second stage dc to dc converters for generating the required dc voltage.Bridgelesss voltage doubler circuit combines both the rectifier and power factor correction circuit to a single circuit, the output of which is double the voltage produced by a single buck converter  used as pfc circuit. This circuit consists of two buck converters connected in parallel in series out manner. The total output obtained is the sum of voltage across each capacitor of the buck converters which are operating during positive and negative half respectively. MOSFET is used as the switching device of the buck converter Usually pulse width modulation technique is used for switching operation and clamped current mode control is used for controlling the buck converter. In this paper ,a new control method called One Cycle Control is used for controlling the buck converter during both half of supply voltage. This method is a non linear control technique to control the duty ratio of the switch in real time such that in each half cycle the average value of the chopped waveform is made equal to the reference value. This method provides greater response and rejects input voltage perturbations.Simualation of the circuit employing One Cycle Control is done in MATLAB/SIMULINK .A prototype of voltage doubler buck converter generating a dc voltage of 12V operating at a switching frequency of 65kHz is developed. The gating signals are generated by microcontroller ATMEGA16 and the program is written in C language.PWM switching technique is used here as implementation of One Cycle Control required a better controller. The results obtained are also presented in this paper.
Rajitha A R, Leena Thomas, Bindu Elias