Switching converters for input current shaping and regulation of multiple outputs

Author: Stevanovic, Ljubisa D.

Year: 1995

Degree: Dissertation (Ph.D.)

Advisors: Cuk, Slobodan; Middlebrook, Robert David

Committee Member: Unknown, Unknown

Option: Electrical Engineering

Abstract

A novel class of isolated Capacitive Idling switching power converters featuring decoupled primary and secondary side feedback loops is presented. While preserving the cost, size and simplicity of the conventional multiple output dc-to-dc converters, this new class of isolated converters possesses the following advantages: no need to cross isolation barrier in the feedback, full regulation of all outputs from no-load to full-load, faster transient response, and independent short circuit protection of each output.

Operation of the Capacitive Idling converters in single-phase ac-to-dc power conversion systems is also analyzed. It is found that these converters perform input current shaping automatically, i.e., without an input current feedback loop. This is achieved by operating primary side inductance(s) in discontinuous inductor current mode (DICM). Consequently, the high power factor performance is obtained without any penalty in complexity, cost and size of the converter. Input current shaping and full regulation of multiple outputs is made possible by the internal energy storage and presence of one secondary-side active switch for each output. When compared to conventional current shaper-regulator configurations involving up to three cascaded power stages, the new converter class represents a very attractive alternative. The main advantages of the Capacitive Idling shapers are:

current shaping and regulation in a single power stage,
simplified control implementation with no feedback isolation, - wide bandwidth loop gain on all outputs, - independent short-circuit protection of each output. Analysis of the Capacitive Idling converters reveals that the input current shaping mode of operation involves a trade-off between the high power factor and the increased switch voltage stress. Boundary of the DICM of operation is determined, resulting in a design equation for the primary side inductance(s). Experimental results verify the analysis and confirm that these converters represent a viable and attractive approach for input current shaping and multiple output regulation.

Files

Stevanovic_ld_1995.pdf (application/pdf)