An interleaved LLC resonant converter operating at constant switching frequency

The interleaving and phase shedding techniques on LLC resonant converters will increase the load capacity, reduce the output current ripple and improve the efficiency. However, conventional frequency-controlled LLCs will lose regulation in individual phases if all phases are synchronized for interleaving, causing current imbalance. Existing load-sharing solutions for multiphase LLCs cannot achieve voltage regulation, phase shedding, and expandable load capacity all at the same time. In this paper, a switch-controlled capacitor (SCC) modulated LLC converter (SCC-LLC) is presented for multiphase paralleling. It features constant switching frequency, which results in a simple structure for paralleling and the ability for phase shedding to improve light-load efficiency. In the proposed structure, a SCC unit is used in each individual LLC stage to regulate the output gain, thereby inherently solves the conflict between the interleaving and the load sharing.