Randomly modulated spread spectrum technique employed in boost PFC circuits

Abstract

Boost power factor correction (PFC) circuit is widely employed in industrial applications to provide regulated DC-link voltage and high-power factor. However, the high switching frequency in boost PFC circuit generates significant electromagnetic (EM) noise. Although electromagnetic interference (EMI) filters can effectively mitigate EM noises, they introduce trade-offs, such as high cost, low efficiency, and low power density. To address those challenges, spread spectrum modulation (SSM) methods have been researched. They distribute the switching frequency over a wide frequency band, reducing peak and quasi-peak EM noises. Random SSM shows high EM noise mitigation performance due to its ability to uniformly distribute noise in a stochastic manner. However, random SSM increases computational burden due to random number generation and operating instability from abrupt frequency shifts in power converters. Although employing random SSM in a CCM boost PFC can effectively mitigate EM noise, its control performance cannot be guaranteed due to distorted current sampling data. To overcome those drawbacks, this paper proposes a variable sampling method to implement random SSM under CCM boost PFC circuit. The design methodology of the proposed random SSM for the boost PFC circuit, focusing on digital implementation, EMI reduction. In addition, associated side effects according to various SSM parameters are analyzed and discussed.