EMI evaluation and hardening of DC-DC converters-a prime source for high conducted noise

In recent trends, DC-DC power converters are now used in mostly all subsystems for deriving single or multiple output voltages from a single power supply module. Though it gives a distinct advantage to the system designer, it has a serious drawback from an EMI point of view which most of the time goes unnoticed in the design level. The authors have evaluated different subsystems of aerospace systems and found that one of the main culprits for high conducted emissions from subsystems is the DC-DC power converter, the levels of which are sometimes so high that they affect the system itself. So as to achieve success of a mission, it is very important to know the EMI performance of DC-DC power converters used in these subsystems. This paper presents some of the problems the authors have come across which are explicitly due to DC-DC power converters of different makes and the methods used to mitigate them. The paper also suggests general EMC design guidelines which can be followed in the design and development stages to control the emissions from DC-DC power converters in order to save the cost and time of hardening at a later date