This paper compares the characteristics of the classic and short time Fourier transform with the continuous wavelet transform. The wavelet transform perfectly suits the considered application, the study of the time evolution of frequency spectra in switched mode power supplies, which operate with significant transients. The analysis made with wavelets offers a means to better understand the generation and propagation of conducted noise
from the noise source, the switching devices, to the point where
the noise is actually measured, the line impedance stabilization
network
High temperature SiC devices need the materials for device packages also capable of working at higher temperature than those for Si devices. This paper presents a selection of materials that are potentially suitable for use in high temperature package assembly, including die attach, substrate, interconnections, encapsulation, case, heat spreader and heat sink. The temperature under consideration is up to 250 °C, corresponding to the need of many applications, including automobiles and aircraft.
Joule heating of copper traces and vias in high current PCBs can significantly deteriorate the reliability of power electronics products. Optimization of the PCB layout is therefore fundamental to guarantee the thermal performance of a converter. This paper investigates the temperature distribution of copper traces and through via holes, when number and disposition of parallel vias are changed in a standard PCB.
Limiting harmonics in the conducted noise of switch mode power supplies is very important, but finding the causes of harmonics to get the best solution to the electromagnetic interference (EMI) problem is often complex. A new tool for the search of conducted noise causes is presented: the more significant harmonics in the EMI receiver measurement are searched in the time evolution of the line impedance stabilization network (LISN) voltage by using the continuous wavelet transform (CWT). In the time frames where the harmonics are present, similar harmonic contents are searched for in the waveforms of the circuit, because these are the causes of the conducted noise. An example of application is described: signals of a boost PFC are processed in different ways to be compared to the EMI receiver measurements of LISN voltage spectrum. The CWT results match pretty well and give some further information than the Fourier transform doe
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