Recent publications on DC-DC converters have pointed out that a chaotic operation mode may be of advantage for EMC reasons. This paper proposes a boost-converter scheme the switching operation of which is controlled by a chaotic return map. A spectral analysis of the converter's input current demonstrates how the shape of the return map affects the power density spectrum of the input current. This provides an approach to solve the design problem, i.e. to choose a return map in order to meet particular spectral demands. Finally a simple circuit solution for the chaotic control of the converter is proposed.