Switching power supplies generate Electromagnetic Interference (EMI) by virtue of their inherent design characteristics. Internal switching power supply circuits that generate undesirable emissions that are rich in harmonics can cause electrical interference both internally to the circuit in which the power supply is installed and to other electronic equipment in the vicinity of the emission source. This application note examines the rules and regulations governing control of EMI, discusses types of noise generated by switching power supplies, and provides basic guidance for EMI mitigation, whether the power supply is installed in other equipment as part of a larger system or designed for stand-alone applications.