The strong demand of the electronics and telecommunications market to develop increasingly economical and, at the same time, performing and reliable systems has contributed to increasing the spread and the use of magnetic components in planar technology, noticely in the design and manufacture of switching power supply (AC / DC power supplies, DC / DC converters and inverters).
Whereas the windings are made of circular-section wire in the 'traditional' wound-wrapped magnetic components, the planar windings are made of rectangular section conductors, for example:
a) conductive tracks on Printed Circuit Board (PCB)
b) Litz wire (braided wire used to reduce the skin effect)
c) Flat copper leadframes, which are often molded to create a laminate-like wrapping structure.
Parts and assembly
flat copper wire
stamped lead frames
The result is a planar magnetic component with high power density and reduced dimensions compared to the analogous traditional wound wire component (25-30% of volume and weight). Lower size and weight can eliminate many of the design constraints associated with traditional wirewound components and there are other features of the planar magnetic component that offer additional benefits.
- efficiency (reduction of losses)
Most of the losses in the windings of a high frequency inductor / transformer are due to the AC impedance compared to the DC resistance. The planar technology causes a significant reduction of these resistive AC losses compared to those observed in the equivalent wound wire components and this fact results in a greater efficiency of the 'planar' component.
- heat transfer efficiency (cooling)
The large base area in relation to the volume offered by the planar cores used in the planar magnetic components makes them ideal for mounting / coupling with active and passive dissipators, thus allowing the increase of the overall efficiency of the transformer / inductor in planar technology.
- low leakage inductance
The laminated construction and the ease of 'twisting' the windings (interleaving) allows the 'optimal' magnetic coupling between the windings; this turns into low values of dispersion inductance.
- excellent repeatability in the production process
The planar components are made from pre-formed parts that are assembled in a few phases process; this allows the manufacturing of ‘equal’ items with high stability of the electrical parameters and minimum incidence of the Not Good components.
Main industry areas
• High frequency battery chargers
• Hybrid electric vehicles
• DC / DC converters and rectifiers
• Devices for solar and wind energy systems
• Welding equipment