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M-LA Technical Developments Volume 21 February 1994
MULTI-CONDUCTOR FLEX-PRINT ~ TRANSFORMERS AND lNDUCTOR$
by Ronald G. Myers
This publication describes a method for wind- ing transformers and inductors using a flex-print coil structure.
High frequency transformers and inductors may have severe power losses due to an increase in AC resistance caused by the skin effect in conductors. Thin copper foil conductors are used effectively to control AC resistance. Thin foil conductor windings are difficult to produce due to the geometry and interconnection problems. This flex-print scheme allows the conductor patterns to be printed in the form of multi-layers of conductors and insulation. Number and placement of the turns are controlled exactly by the design. Flex-print is rolled or formed to the pattern required by the magnetic core yielding a product with consistent performance parameters and low manufacturing cost.
Referring to Figure 1, the flex-print 27 comprises a front layer 28 and a rear layer 29. The front layer comprises a four turn primary foil 30 and a two turn secondary foil 31. The rear layer comprises a two
turn secondary foil 32 and a four turn primary foil
33. Ah foil conductors are electrically isolated using standard flex print manufacturing techniques. This particular flex-print 27 is~for a push-pull transformer with a primary to secondary turns ratio of 2 to 1. The flex print 27 is wound on a suitable mandrel or other forming device to shape the coi...
