Developed by ECI in the mid 1980's, "planar magnetics" is a component topology which is typically characterized by low profile core structures utilizing laminated or copper lead-frame windings in place of round magnet wire.

Typical applications for planar magnetics technology are SMPS switching topologies including: Flyback, Forward, Dual Forward, Push-Pull, Half or Full Bridge. Input voltages range from DC-DC to Off-Line applications. Typical switching frequencies range from 20kHz to 2MHz. Typical power ratings range from a few watts to 20kW, with output currents up to 200A. Typical sizes range from 1cm, with heights as low as 0.5cm.

Some of the benefits of using multilayer PCB technology for planar magnetics are that winding circuits may be interleaved, thus minimizing parasitic leakage inductance. Terminations are able to be arranged to suit specific applications. Multiple windings may be incorporated on a single structure, limited only by the number of layers available and space allocated for pin-outs. ECI planar transformers are typically multilayer PCB or hybrid (PCB/copper lead frame combination) construction. Planar transformers may be terminated using a variety of methods including; Thru-hole, SMT pins or pads, tab mount or card mount. Multilayer insulation materials providing operating temperature ratings from 105ºC to >180ºC include: High Tg FR-4, BT (Bismaleimide-Triazine) Epoxy, and Polyimide. Other advantages of planar include "integrated planar magnetics", where the output inductor is combined with the transformer, resulting in an overall reduction in space. For a custom designed ECI planar transformer, complete the "custom planar transformer design worksheet", and forward to ECI.

Typical applications for planar transformers:

  • All SMPS switching topologies
  • DC-DC or Off-Line applications
  • Switching frequencies of 20kHz to >2MHz
  • Output power ranging from a few watts to 20KW
  • Output currents up to 200A

Advantages of planar transformers:

  • Inherent low profile structure
  • High power density
  • Excellent performance repeatability
  • Low radiated EMI
  • Good heat dissipation
  • High surface area to volume ratio enhances conduction cooling
  • Solid construction facilitates heat transfer
  • Low leakage inductance
  • Highly controlled transformer parasitics
  • Minimized skin effect losses
  • Accommodates many windings
  • Flexible pin-out patterns