Low cost conducted emission tips for switching power supplies

The major challenge in achieving compliance with conducted emissions requirements for switch mode power supplies is the implementation of the optimum control of the common mode conducted emissions. Common mode emissions arise on the input power leads from a combination of conducted effects associated with stray capacitance between the switching elements and the chassis and inductive effects related to magnetic coupling from the magnetic components in the supply and the input and output wiring harnesses. This paper addresses both subjects from a conceptual view with some resulting suggestions for simple modifications to filters and internal layout.