Minimising peak current in boundary conduction mode for the four-switch buck-boost DC/DC converter with soft switching

The DC/DC converter needs the inductor to get the desirable increased voltage, which means it is impossible to avoid the power loss. Thus, minimising the inductor current may be a way to suppress the loss. In this study, to achieve higher efficiency of DC/DC converters, the control method to minimise peak current in boundary conduction mode (BCM) of the DC/DC converter is proposed when implementing soft switching of the converter switches. The comprehensive principle to minimise peak current in BCM is studied and the precise conduction time and conduction sequence of four switches of the buck-boost circuit are deduced. On comparing with the bipolar BCM and unipolar BCM, the proposed BCM could effectively reduce the inductor current in the DC/DC converter. Furthermore, low-voltage and high-voltage DC experiments were independently designed to verify the proposed control. The experimental results from a prototype of 1kW DC/DC converter proved that this novel control method could realise the soft switching with the minimising peak current of the buck-boost converter switches and reduce the loss of the whole DC/DC converter.