This work discusses measurements and modeling of conducted emissions in the time and frequency domain to evaluate the impact of common DC/DC converters existing on DC grids. Variable DC input voltages are used to study the influence of input voltage on the LISN and conducted emissions. The time-frequency domain was shown to provide extra information to assess conducted emissions in addition to the time- and frequency-domain representations. PSIM software was used to model the system, and MATLAB was used to analyze the signals. Short-time Fourier transform (STFT) and spectrogram of the signal have been employed for the evaluation of conducted emissions. According to the results when the input voltage rose, the amplitude of the transmitted propagation decreased. In the future, the findings might be applied to the design of EMI filters.