Isolated multiple output cuk converter with primary input voltage

Abstract

A novel isolated, capacitive idling, Cuk switching-mode converter features two separate nonisolated feedback loops, one on the primary side to regulate against input voltage changes and the other on the secondary side to regulate against load current changes only. While preserving cost, size and simplicity of conventional multiple output switching-mode converters, the new converter and feedback control approach offers the advantages of simple feedback control implementation due to elimination of isolation requirements in the feedback control circuits, simultaneous regulation of all output voltages from no load to full load, and greatly improved bandwidth and step-load transient response. For operation from a rectified ac line, feedback control on the input to the transformer is modified to force the average input current to follow the full-wave rectified ac line voltage for unity power factor (UPF) performance on the input and wide bandwidth voltage regulation on the output. Both are demonstrated simultaneously in a single, isolated, multiple ac-to-dc switching-mode power converter. The novel decoupled feedback control is shown to be equally applicable to a number of Cuk-type converter topologies featuring capacitive energy transfer from a voltage source to a load.