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Why Standex Electronics Planar Transformers

Standex Electronics Planar Transformers

“Standex Electronics Planar Transformers offer improved power density and performance over-wire wound designs.”

If there are particular areas you need help with, feel free to skip to any of the following sections:
The Advantages of Planar Transformers Over Wire-Wound
Why Standex Electronics Planar Transformers?
General Guide on Designing with Planar Transformers
Examples of Where Planar Transformers Reside
Additional Resources

Efficiency: Updating capabilities, improving capacity, reducing costs

“If I were to tell you that there was a way to reduce costs, electrical efficiency capabilities, and enhance electrical capacity through a product you needed – would you buy it? Of course, you would! Smaller, faster, cheaper – the name of today’s engineering game.”


Standex Electronics Planar Transformers are steadily replacing traditional wire-wound transformers in many industries. Planar magnetics are the growing trend in many industries, especially electric vehicles and alternative energy. And, those are just some of the areas where this technology is gaining ground. Standex planar designs deliver to various needs which include core materials, their shapes, and manufacturing techniques.

So, with the ever-increasing need to be faster, perform with greater accuracy, improve time to market, and reduce costs – planar transformers replace the traditional wire-wound transformers with a solution that makes perfect sense for a successful blueprint.

The Advantages of Planar Transformers Over Wire-Wound


Planar Transformers group

“First, the difference that planar transformers allow over traditional wire-wound transformers is the planar’s use of flat copper windings or lead frames,” explains Will Schellin, Engineer at Standex Electronics. While the windings of wire-wound transformers are used with round wire, the planar’s windings are built by utilizing flat copper layers (PCBs) or plated flat copper windings (lead frames) to create a laminate-style winding construction. Finally, the result is a compact, high power density planar transformer that is typically 30% of the volume and weight of a traditional wire-wound transformer.

A Matter of Size

Moreover, this size reduction eliminates many of the wire-wound design constraints. As if that wasn’t enough, the planar transformer’s other characteristics offer additional benefits. The benefit of a very low profile and excellent thermal properties for starters. Then you have high repeatability and low leakage inductance.  In other words, planar transformers can easily meet the needs of modern power transformer designs.

Custom Designs for Greater Flexibility

However, the benefits of planar transformers can be best realized with customization. Thanks in part to the PCB and lead frame structure, planar transformers provide a great degree of design flexibility. So, they can be modified to more exactly fit the parameters of specific applications.

“At Standex Electronics, we’ve had great success partnering with our customers to create custom solutions,” said Schellin. “The technology behind planar transformers really opens up a lot of possibilities for innovation. And by working with designers, engineers, and manufacturers, we can take advantage of those opportunities. Whether to heighten efficiency, tighten control, or simply save space and money.”

Customer Configurations

Check out the below sample list of custom planar options or take a deeper look at our planar design guide for sample reference designs.

  • Soft switching, single or multiple outputs
  • Wide switching frequency range
  • Input/output voltages
  • Optimized turns ratio
  • Thermal solutions heat sinks, etc.
  • Multiple terminal/termination options
  • Inductors available for design in all packages
  • Value-added assemblies
Planar Magnetics Design Guide

Planar Magnetics Design Guide

General Guide on Designing with Planar Transformers

In summary, designing Planar Transformers is generally guided by some basic principles listed below. Our engineers can assist you with your custom planar transformer or custom planar inductor request today!

  • Choose optimum core cross section
  • Choose optimum core window height
  • Iterate turns vs. duty cycle
  • Core loss
  • Cu loss
  • Evaluate thermal methods
  • Estimate temperature rise
  • Tradeoff cost vs. number of layers
  • Mechanical design fit envelope pad layout
  • Fit within core window height
  • Size sufficient for power loss and thermal solution

Why Standex Electronics Planar Transformers?

Now that you have a better understanding of Planar Transformers designs. Next let’s take a look at the below list of what Standex Planar Magnetics have to offer.

  • Repeatability, high-performance, and reliability
  • Multiple winding options and topologies
  • Low profile height and lightweight
  • Low leakage inductance
  • Space savings and capacity improvement (retro/custom fits)
  • High efficiency (resistance, flux density)
  • Customized terminations
  • Volumetric efficiency (small size)
  • High voltage isolation transformers
  • Low turns count improves Cu loss
  • Large core surface promotes heat transfer
  • PCB construction yields lowest Cu loss
  • AC resistance and proximity Cu loss minimized
  • Opportunity to embed planar into PCB module (integrated magnetics)
  • Optimized core cross-section lowers core loss

For a switched-mode power supply (SMPS), our planar transformers act as the main component and the smart choice for converting power and doing the transformation of the voltage effectively. Smaller volume planars can handle the same amount of work as larger wire-wound transformers.

Standex Planar Transformers in switched-mode power supply (SMPS)

Standex Planar Transformers in switched-mode power supply (SMPS)

Examples of Where Planar Transformers Reside

Below are some high level examples of where planar transformers are commonly used.

  • Distributed isolated power
  • Battery charging and operation (12V, 24V, 48V, and 1-10KW)
  • Isolated inverters (to 50KW)
  • Renewable energy sources (wind and photovoltaic)
  • AC-DC resonant designs

At Standex Electronics we believe “Complex Problems Deserve Custom Solutions”. So, below we detail three examples of how Standex delivered superior planar transformer designs, solving complex problems.

Example 1: Industrial Applications: Precision Control for Arc Welding

Some of the most demanding uses for electronic components are in the industrial sector. Where high temperatures, harsh environments, and heavy workloads can all contribute to stress and strain. Therefore, the high performance and reliability of planar transformers makes them ideal for industrial use.
For example, “an industrial customer came to us with a project involving arc welding,” said Schellin. “Arc welding is an incredibly demanding process. Since arc welding produces a lot of heat and involves virtually continuous arcing across the electrode and weld spot. As a result, the continuous arc produces a large temperature rise in a small welded area.”
So the customer needed a reliable planar transformer for their arc welding power supply. And, they were looking to improve efficiency, but a solution that could handle the increased thermal demand of the transformer.
As mentioned above, the windings in planar transformers are flat rather than round, and as a result offer less AC winding resistance and thus reduce overall loss. The duty cycle of the power supply can limit the time the arc welder can operate the welder. Possible damage to the power supply may occur if the power supply is run over the rated continuous time for the specific unit.
Standex therefore designed a planar transformer that was not only high-performing and reliable. But also allowed for greater control of temperature, resistance, and heat dissipation. “Precision and control are always essential to a successful weld, no matter which method you employ,” said Schellin. “With the increased thermal performance and help of an aluminum heatsink the planar transformer provided to our customer helped ensure greater control of the welding process and longer continuous weld times.”


Find out more about our unique planar capabilities. Or if you have planar design defined, fill out our custom planar transformer form

Additional Resources

Take a look at our Planar magnetics flyer for a quick comparison of standard sizes offered.

Planar Magnetics Flyer

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