EMI Filter Design, 3rd Edition

11Transformer’s Addition to the EMI Filter

The transformer is overlooked as an EMI filter element. This is because of the obvious disadvantages of weight, size, and cost. Using off-line regulators and switchers can often eliminate transformers. On the other hand, switchers often complicate EMI issues because of the high-frequency switching noise they generate. This is worse as the switcher frequency increases. Also, switchers, because of their present-day glut of components, may have a tendency to impact MTBF (mean time before failure) requirements. A question for the system designer is perhaps, “Do the disadvantages of using a transformer overshadow the advantages?”

11.1 Transformer Advantages

The main advantages of the transformer, without ...