| Part I. For coupled-inductor and integrated-magnetics design it is of paramount importance to accurately model leakages. Air gap position has a dramatic effect on coupled-inductor characteristics. Improved reluctance models that capture this effect are proposed.A method to estimate this reluctance from core geometry is also suggested.A new coupled-inductor structure that achieves quasi-zero current ripple without need for turns ratio adjustment is introduced.Closed-form design equations for coupled-inductors are given.For the most common coupled-inductor structures, i.e., UU and UI cores with windings on different legs, a simple model valid for any gap arrangement is proposed. The model has a single leakage reluctance that is constant for a given core geometry and can be determined from a single set of measurements.Part 2. The concept of One-Cycle control has recently been proposed. The generality of this control technique is demonstrated through description of its implementation for different DC-DC switching converters. It is a nonlinear control technique with significant advantages in terms of rejection of line perturbation, speed of response and insensitivity to circuit parameters. Until now, no stability analysis was available and, under certain conditions, instability was observed. In this paper a stability analysis of a One-Cycle controlled Cuk converter (a fourth order system) is performed, which shows that stability depends on the value of parasitic elements. A modification of the control to eliminate steady-state output voltage error is proposed. Finally, a modification of the control that ensures stability independently of the value of parasitic elements is suggested. All theoretical results are experimentally verified. |
