Boost-Buck power factor correction converter with integrated different current control methods

Working principle of single-phase Boost-cascaded Boost-Buck(BoCBB) power factor correction converter is analyzed. On this basis, a new nonlinear current control method for buck converter is presented first, and a novel integrated control strategy constituting average current mode control and the above nonlinear current control method is proposed for BoCBB converter. With this control strategy, the BoCBB converter can work as a simple boost or a simple buck converter as required. That is, when the input voltage is lower than the output voltage, BoCBB works as a boost converter and the average current control method is used, and when the input voltage is higher than the output voltage, BoCBB works as a buck converter and the above nonlinear current control method is used. Compared with the traditional control scheme that the first-stage boost converter and second-stage buck converter are controlled independently, both the switching loss and voltage stress of the BoCBB can be reduced markedly, and the input current can be controlled more effectively not only in boost work mode, but also in buck work mode. Control diagram is given in this paper, and a 1.5kW rated single-phase boost-buck converter prototype controlled with digital signal processor (DSP) TMS28027 is built to verify the theoretical analysis. Experimental results shows that the output voltage can be regulated at a given value which is lower than peak line voltage, the input current can also be controlled into a sinusoidal waveform, and unit power factor is achieved meanwhile.