Transformer design: which safety standards should you apply?

August 11, 2014 // By Richard Chung & Dean Huumala
When designing an offline flyback power supply, integrating the IC with the other components can be a daunting task. Not knowing the safety standards can lead to unwanted surprises of non-conformance at the qualifying labs and sending a product back to design.

Integrating the transformer properly is more than finding the turns-ratio to match with your input and output(s). “I thought a Flyback transformer is just transferring energy across a safety isolation barrier,” leads to; “I guess there is more to understand.” Not knowing the safety standards will usually mean more iterations than necessary when working with a transformer manufacturer. Not knowing the safety standards can lead to unwanted surprises of non-conformance at the qualifying labs and sending a product back to design phase rather than qualification before mass production.

This summary article has been compiled by two companies that supply those key aspects; the silicon controller IC and the transformer. Understanding the requirements that govern transformer design and manufacturing will shorten design cycles to finished products using Fairchild parts in its Power Supply WebDesigner (PSW) facility. Just knowing the appropriate safety standards required for your design will be enough to allow Wurth Electronics Midcom to design the right part the first time over 90% of the time.

Knowing safety standard required during product definition or design definition will ensure unnecessary design iteration and cost. Below you will find the most common standards used in the industry to define the safety requirements of offline transformers. Wurth Electronics Midcom is very familiar with these standards and typically knowing which standard you are trying to meet and the insulation type is enough to get you what you need.

Which transformer safety standard to use is not always immediately clear to the electronics designer. Typically, the standards to be met for a product are based on the equipment type to be designed; and the markets that the equipment is targeting. Product Marketing as well as Safety Engineers with in a company are best equipped to choose which standards apply.

In order to make your search easier, we have listed a number of the more common standards that are referred to by electronics manufacturers that apply to their equipment. We have attempted to take the scope and a brief description of these standards from the standards themselves. While the descriptions have been pulled directly from the standards, they have been paraphrased for readability and are not in any way a substitute for the actual standard. The advantage here is that the scopes of the most typical standards that are used, have been compile into one document to let you easily identify which standard might apply. From there you can purchase the full standard document for further review.

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