为解决传统LLC谐振变换器在宽电压增益应用中所需开关频率范围过宽、总体效率较低等问题,文中提出一种多模式双LLC谐振变换器.该变换器基于半桥、全桥切换以及桥式、倍压整流切换的拓扑重构思路,以增益不同的4种模式实现较窄频率范围内的超宽输出电压,提高变换器效率的同时通过复用开关器件来降低成本.为了实现模式间的平滑过渡,针对所提变换器设计一种脉冲宽度频率调制控制方法,并根据模式切换特性进一步优化,提高模式切换速度.基于SiC开关器件,设计并搭建一台 60～450 V输出电压、最大功率为 900 W 的实验样机,以验证所提拓扑及控制方法的可行性.
An Ultrawide Voltage Gain Dual LLC Resonant Converter and Control Method
Due to the wide switching frequency range and low overall efficiency,traditional LLC resonant converters are not suitable for wide voltage gain applications.To solve the problem,a multi-mode dual LLC resonant converter is proposed.Based on the topology reconfiguration of half-bridge and full-bridge circuits as well as full-bridge and voltage-doubler rectifiers,the converter realizes an ultrawide output voltage within a limited frequency range by four modes with different voltage gain.While the efficiency of the converter is improved,the cost is reduced by multiplexing power devices.In order to achieve smooth transitions between these modes,a pulse width modulation-pulse frequency modulation(PWM-PFM)control method is designed for the converter,which is further optimized according to the characteristics of mode switching to improve the speed.To verify the feasibility of the proposed converter and control method,a SiC-based experimental prototype with an output voltage of 60～450 V and a maximum power of 900 W is designed and tested.
LLC resonant converterdual-transformertopology reconfigurationwide voltage gainmode switching
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