A spread spectrum modulation (SSM) is a good solution to mitigate the EM noises by power converters through switching modulations. However, the SSM causes high output voltage ripples in LLC resonant converter due to the frequency-dependent characteristics of the resonant network. In this paper, partial power-regulated LLC converter is proposed. It can obtain high efficiency as well as good output voltage regulation performance under the SSM. The LLC converter performs the SSM as a DCX operating at the resonant frequency without feedback control. In contrast, the buck converter controls the duty cycles to compensate for the voltage ripples using partial power. As a result, EM noise mitigation, good output voltage regulation performance, and high power conversion efficiency can be obtained. The validity of the proposed converter is verified by a 500-W prototype.
