具有自主均压能力的混合型LLC谐振变流器研究

Hybrid LLC Converter With Input Voltage Auto-balance Ability

提出一种基于飞跨电容的混合型LLC谐振变流器。变流器利用飞跨电容实现对输入电压的分压处理,把原边开关管的电压应力自动钳位在输入电压的一半,有利于变流器工作在高输入电压大功率的场合。输入电源经过飞跨电容的分压分流后连接到LLC谐振网络,利用LLC谐振变流器所具有的滞后功率因素特性实现原边开关管的软开关,减小开关损耗,提升变流器效率,并且利于实现高频化。此外,通过LLC谐振变流器所具有的频率增益特性,可以在较宽的范围内实现对变流器电压增益的调整。最后,制作一个400-640V输入、48V输出的1 kW实验样机,验证所提出的拓扑的有效性。

An advanced hybrid LLC series resonant converter with integrated flying-capacitor cell was proposed in this paper to enable the high step-down conversion in the high input voltage applications. The inherent flying-capacitor branch in the primary side can effectively halve the primary switch voltage stress compared with the half-bridge LLC converters. Moreover, the inherent soft switching performance during wide load range that exists in the LLC converters is still kept to reduce the switching losses, which ensures the high efficiency. Besides, wide-range voltage regulation is achieved due to the frequency-gain characteristics of the LLC resonant tank. Finally, a 400-640 V-input 48 V-output 1 kW prototype was built and tested to verify the effectiveness of the proposed converter. The results prove that the proposed converter is an excellent candidate for the high input voltage and high step-down DC/DC conversion systems.