Low ripple and noise DC/DC converter with quasi-resonant switching and integrated magnetics.

Abstract

A low output ripple and noise converter is achieved by employing a zero-voltage switch (ZVS), an integrated magnetics structure which couples a transformer and several coupled inductors in one core, and several auxiliary packaging designs. In the steady-state analysis, the operation of ZVS converter is described and the ZVS switch resonant component design procedure is developed. An optimized geometrical core constant integrated magnetics design procedure is proposed. Some auxiliary packaging design considerations are addressed. The converter ac analysis is divided into two parts to observe the individual small signal effect introduced by the ZVS switch and coupled inductor. The uncoupled-inductor converter ac analysis is conducted by a new approach: an extended circuit averaging method. The converter ac model is obtained by substituting in the coupled inductor ac model to the uncoupled-inductor converter ac model. It is found both the dc coupled inductor zero current ripple condition and the ac converter transfer function response are affected by the turns ratio and the leakage inductance of the coupled inductor. Hence, the converter dc and ac designs are coupled by the coupled inductor operation. Experimental results of the dc and ac analysis of a ZVS converter with coupled inductor are shown. Integrated magnetics achieves less than 3% peak-to-peak current ripple on both coupled inductors at the same time. The equivalent result by separate magnetics approach requires twice the volume implemented by the integrated magnetics structure.