Advantages of the Second Generation Planar Magnetics

  • ER core geometry reduces ATL (average turn length) thus reducing Rdc and Rac of windings.
  • Reduction in Rdc and Rac improves efficiency.
  • Total surface of planar turn is in direct contact with a core backwall, thus greatly improving thermal conductivity and reducing EMI.
  • In most applications better efficiency and better thermal management (lower thermal impedance) allow the use of smaller packages.
  • Smaller packages mean lower costs.
  • Flexible, low impedance terminations.
  • U.S. Patent No.7,129,809 SMD packages with excellent co-planarity.



Technical Comparison of Isolation Systems
 

Multilayer (mlt) Based

  

Plastic Bobbin Based
•
 Mlt Board System laminates high potential copper layers with prepreg Copper sealed inside mlt board. Terminals soldered far from core.
•
 High Potential copper turns mounted in a cavity inside lower half of plastic bobbin. Upper half of bobbin mates with lower half.
•
 Stack of windings do not have any air pockets and have a direct heat dissipation path to the ferrite core.Thus, lower thermal impedance and operating temperature.
•
 There are at least three air pockets in the system increasing thermal impedance and, consequently, windings run hot.
•
 The thickness of isolating layers is only 8-12 mils. Low voltage copper leadframes are bonded directly to mlt boards.
•
 Plastic bobbin wall thickness is at least 20 mils and is used from 2 to 4 times. The wall increases thermal impedance. Multiple cavity bobbins which are used for high power further increase thermal impedance.
•
 Mlt boards are vertically spaced from one another outside the core thus forming openings for free passage of cooling air.
•
 High potential windings are sealed inside the bobbin and can not be air cooled.

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