Impact of the spread-spectrum technique on the higher-order harmonics and radiated emissions of a synchronous buck converter

Switched-mode power converters generate electromagnetic emissions which may violate the limits specified in the regulations. Spread-spectrum is an effective technique for reducing the electromagnetic interference of switching devices. The reduction of the magnitude of the first harmonic by the spread-spectrum technique is mainly in focus in the literature. In this paper, the impact on the higher-order harmonics and on the radiated emissions is analyzed. A non-regulated synchronous buck converter is used as a device under test. The radiated emissions of the converter are calculated from the measurements performed by a transverse electromagnetic cell and a hybrid coupler. The measurements are performed for different values of the parameters of the spread-spectrum technique and a reduction of up to 5.7 dB is obtained.