Low-loss bidirectional buck-boost DC-DC converter

Abstract

For DC energy systems there is reversible buck/boost pulse converter (RPC) in the classic converter circuit. The maximum efficiency of the RPC without additional mechanisms to reduce the dynamic energy losses in the power semiconductor keys (PSK) during their commutation is about 92%. Improved efficiency is achieved by providing «soft switching» of the transistors RPC, i.e. in zero current/voltage switching. These methods require the introduction of supporting links in the RPC, which have a negative impact on the performance of reversible buck/boost pulse converter. Due to the increase in the number of components, this leads to degradation of mass-size characteristics of the product and decrease in its reliability. New RPC transistors control algorithm RPC provides an opportunity to use transistors at zero voltage without additional elements. Because of the relative novelty of this technical solution, the energy exchange processes in the reactive elements of power semiconductor devices (PSD) are poorly studied. By reason of insufficient studying of power exchange processes in reactive elements of converter, it seems important to study these processes and use the received results for recommendations about reversible buck/boost pulse converter designing. As a result of research it was found out that the recuperation of energy stored in parasitic capacitance of drain-source transistors acting as PSD. At designing of RPC the account of the revealed phenomenon of energy, recovery will allow additionally to raise its efficiency at the expense of decrease in losses of energy on PSK in shutdown state. For this purpose, it is necessary to use transistors with high value of parasitic capacitance of drain-source or include additional capacitors in parallel with PSK.