FMTT, Inc.

Edward Herbert, President

Flat Matrix Transformers
Technology for License

"Flat is where it's at!"

Simplified method of calculating core losses
LinkUser-friendly Data for Magnetic Core Loss Calculations  (pdf, 234 k)
Core loss data is usually specified for sine waves, where as many power converter applications use low duty-ratio pulses.  A new method of calculating core losses based upon square wave data is presented.  Methods are proposed for calculating the core loss using low duty-ratio pulses, symmetrical or asymmetrical.
Revised November 10, 2008, 7 pages, 234 k.

Transformer SPICE Model
LinkTransformer Spice Model  (pdf, 1,020 k)
New SPICE models are presented for transformers, from a simple ideal transformer to models including core saturation, core losses and winding losses.  The core loss models are based upon a new analysis of core losses, and the analysis is included as Appendix A.
Revised February 14, 2008.  41 pages, 1,020 k.

Coaxial Push Pull Transformers
LinkCoaxial Push Pull Transformers  (pdf, 227 k)
The coaxial push pull transformer uses the same magnetic core structures as the flat matrix transformer, and shares its characteristic low profile and excellent thermal dissipation.  A new winding design using a coaxial arrangement between the primary and the secondary windings has near ideal coupling and near zero leakage inductance.  The absence of multiple layers of copper eliminates many of the more troublesome high frequency effects.  The coaxial push pull transformer is ideal for a "dc-dc transformer".  A variant has a turns ration that can be varied electronically, so the "dc-dc transformer" can have a precise output voltage even with input and load regulation.
Revised March 14, 2006.  26 pages, 227 k.

Variable Dc-Dc Transformers
Variable Dc-Dc Transformers and Their Use as Modulators

The variable dc-dc transformer has boost modulator characteristics.  It is the preferred output modulator for power converters requiring isolation and having a large step-down voltage ratio.

The primary excitation operates at 100 % duty-cycle, for maximum efficiency.  The effective turns ratio is controlled on the secondary side, so no feed-back signals need to cross the isolation barrier.

The efficiency of the variable dc-dc transformer is highest when its effective turns ratio is maximum, just as in a boost converter operating at nearly 0 % duty-cycle.  If the input voltage droops, the effective turns ratio is reduced to maintain the output voltage regulation.  Because the effective turns ratio is lower, the input current increases and efficiency is reduced.

More information:  A Seminar Presented at the Fifth International High Frequency Power Conversion Conference '90 Santa Clara, California,   May 11, 1990:  Tutorial: "Design and Application of Matrix Transformers and Symmetrical Converters"  (Pdf. file, 7.9 M)

FMTT, Inc.
One Dyer Cemetery Road
Canton, CT 06019
Phone: 860 693 1684
Fax: 860 693 1686
January 17, 2010