Edward Herbert, President
Flat Matrix Transformers
where it's at!"
Simplified method of
calculating core losses
Link: User-friendly Data for Magnetic Core Loss
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
Link: Transformer 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
Link: Coaxial 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
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
Link: Variable Dc-Dc Transformers and Their Use as
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
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.
One Dyer Cemetery Road
Canton, CT 06019
Phone: 860 693 1684
Fax: 860 693 1686
January 17, 2010