Mitigating conducted EMI from DC-DC converters

Conducted EMI can result from the normal operation of switching circuits. The ON and OFF actions of the power switches generate large discontinuous currents. The discontinuous currents are present at the input side of buck converters, the output side of boost converters and at both input and output ports of flyback and buck-boost topologies. Voltage ripple generated by discontinuous currents can be conducted to other systems via physical contact of the conductors. Without control, excessive input and/or output voltage ripple can compromise operation of the source, load or adjacent system. The discontinuous currents at the input port of a converter need to be filtered by an input filter to smooth out the voltage perturbations leading to the source. Meanwhile, the output side is usually well filtered by the existing output filter of the converter. Proper application of filtering leads to meeting regulatory requirements that allow the end product to be sellable in the marketplace.

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Originally published by Texas Instruments at www.ti.com as "Simple Success With Conducted EMI From DC-DC Converters".