## 3 Results and Discussion
### Uniformly Distributed Chaotic Signal for Uniform Shaping of Conventional PWM Power Spectrum  
Using [PERSON]'s chaotic signal \(x\) and the obtained uniform distribution chaotic signal \(y\) to perform chaotic spread spectrum modulation on conventional PWM, the measured power spectra are shown in Figure 14. The maximum value is marked by '\(\times\)'. \begin{table}
\begin{tabular}{c c} \hline
**Parameter** & **Specification or Value** \\ \hline transformer magnetic core & PQ3535 \\ transformer excitation inductance \(L_{\text{m}}\) & 509.02 \(\mu\)H \\ primary coil leakage inductance \(L_{\text{s}}\) & 9.74 \(\mu\)H \\ resonant capacitor \(C_{\text{r}}\) & 0.1 \(\mu\)F \\ voltage sensor & LV25-P \\ current sensor & FC-SCT4.6-1:100 \\ output capacitor \(C_{\text{o}}\) & 100 \(\mu\)F \\ \hline \end{tabular}
\end{table} 
Table 1: _Cont._  
Figure 12: The implementation of chaotic spread spectrum modulation PWM: (**a**) analog spread spectrum implementation; (**b**) digital spread spectrum implementation. Figure 13: Clock signal of chaotic spread spectrum modulation PWM. Figure 14a shows that the power spectrum of conventional PWM is a linear spectrum with a large peak; the power spectra of Chua's chaotic spread spectrum modulated PWM and uniformly distributed chaotic spread spectrum modulated PWM are both continuous spectra, with the peak being significantly reduced. Figure 14b shows that Chua's chaotic spread spectrum modulated PWM power spectrum is non-uniformly distributed, while the uniformly distributed chaotic spread spectrum modulated PWM power spectrum is uniformly distributed, with a smaller peak. Therefore, the uniformly distributed chaotic signal can uniformly shape the power spectrum of conventional PWM, obtaining a uniformly distributed power spectrum, thus maximally reducing the peak of the power spectrum and effectively suppressing EMI. Uniformly Distributed Chaotic Signal for Uniform Shaping of Power Spectrum of Common-Mode Conducted EMI  
The actual measured power spectra of common-mode conducted EMI under the operation of the prototype in conventional PWM control mode, \(x\) chaotic spread spectrum modulated PWM control mode, and \(y\) chaotic spread spectrum modulated PWM control mode are shown in Figure 15.  
The measured data of the maximum value of common-mode conducted EMI are as follows: 81.73 dB\(\upmu\)V for the conventional PWM control mode; 68.65 dB\(\upmu\)V for the \(x\) chaotic spread spectrum modulated PWM control mode; and 65.17 dB\(\upmu\)V for the \(y\) chaotic spread spectrum modulated PWM control mode, as indicated by the '\(\times\)' mark in Figure 15a. Figure 14: Power spectrum of conventional PWM and chaotic spread spectrum modulation (CSSM) PWM: (**a**) power spectrum; (**b**) zoomed-in image of region A.  
Figure 15: Power spectra of common-mode conducted EMI; (**a**) power spectra; (**b**) zoomed-in image of region B. Figure 15a shows that under the conventional PWM control mode, the power spectrum of the common-mode conducted EMI appears as a discrete line spectrum with the maximum peak. This is the root cause of severe EMI in conventional PWM controlled converters. Under the \(x\) chaotic spread spectrum modulated PWM mode and \(y\) chaotic spread spectrum modulated PWM control mode, the power spectrum of common-mode conducted EMI is extended, showing a continuous distribution, and the peak is significantly reduced. Figure 15b shows that the distribution of the power spectrum of common-mode conducted EMI under the \(y\) chaotic spread spectrum modulated PWM control mode is the most uniform, with the lowest peak. Compared to conventional PWM control mode, the maximum peak reduction is 16.56 dB. Compared to the \(x\) chaotic spread spectrum modulated PWM control mode, there is a 3.48 dB improvement in the suppression effect on common-mode conducted EMI. In summary, employing the acquired uniformly distributed chaotic signal to modulate the frequency of conventional PWM converters can uniformize the power spectrum, exhibiting uniform distribution characteristics.