A Dual Half-Bridge LLC Resonant Converter With Magnetic Control for Battery Charger Application

In this paper, a dual half-bridge
LLC
resonant converter with magnetic control is proposed for the battery charger application. The primary switches are shared by two
LLC
resonant networks, and their outputs are connected in series. One of the
LLC
resonant converters is designed to operate at the series resonant frequency, which is also the highest efficiency operating point, and the constant output voltage characteristic is achieved at this operating point. The second
LLC
resonant converter adopts magnetic control to regulate the total output current and voltage during both constant current charge mode and constant voltage charge mode. Meanwhile, the function decoupling idea is adopted to further improve the system efficiency. The significant amount of the power is handled by the
LLC
resonant converter operating at the series resonant frequency, whereas the second
LLC
resonant converter fulfills the responsibility to achieve closed-loop control. By carefully designing the resonant networks, the zero-voltage switching for primary switches and zero-current switching for secondary diodes can be achieved for whole operation range. A 320-W experimental prototype is built to verify the theoretical analysis, and the maximum efficiency is measured about 95.5%.