Design and Analysis of the DC–DC Converter With a Frequency Hopping Technique for EMI Reduction

Active EMI Reduction Using Chaotic Modulation in a Buck Converter with Relaxed Output LC Filter

“…The simulated switching frequency distribution of the chaotic triangular ramp generator using slope modulation is shown in Figure 10. To achieve the most flattened power spectrum, a uniformly distributed switching frequency is most desirable [18]. As seen in Figure 10, the distribution of the chaotic switching frequency is not uniformly distributed over the desired frequency range.…”

“…However, the frequency spreads out continuously in the pre-defined range; therefore, harmonic peaks in the power spectrum in chaotic mode are expected to disappear. Generally, the EMI reduction of the switched-mode dc-dc converters using spread spectrum technique can be verified by analyzing the power spectrum [16][17][18]. The power spectrum of the switching node and the output node were calculated using the available spectrum analyzer tool in Cadence software.…”

“…In previous works using the randomized modulation technique [17,18], the power at the harmonic frequencies was spread out around discrete fixed-frequency levels. In particular, using the theory reported in [18], and assuming that randomness was assured, the theoretical reduction (ideal case) in the power spectrum using 2, 4, and 8 switching frequencies was 6 dB, 12 dB, and 18 dB, respectively. Using the spread-spectrum chaotic modulation proposed here, the reduction in the power spectrum can easily be more than 18 dB without the requirement of randomness because the power spectrum is spread continuously out rather than clustered around discrete frequency harmonics.…”

“…This is equivalent to hopping among an infinite set of switching frequencies, which results in the full elimination of the peaks in the power spectrum present in the standard fixed-frequency PWM mode. Therefore, EMI reduction can be higher than that offered by previous solutions [17,18]. Proposed scheme for synthesizing a chaotic pulse-width modulation (PWM) signal with an N-shaped chaotic generator for a buck converter using a type-III compensator network.…”

“…As described in the previous sections, EMI reduction via the spread-spectrum technique is always achieved at the cost of a performance reduction in the buck converter, including: (1) an increase in the output voltage ripple; (2) a increase in inductor current ripple; and (3) a reduction in power efficiency. However, those negative side-effects have often been neglected in the literature [16][17][18]. All of those factors require an increase in the size of passive LC output filter [8,22].…”