针对传统LLC谐振变换器重载工作时电压增益低,难以实现宽范围输出,同时低增益工作时开关频率高,开关管损耗大、电路效率低的问题,结合全桥LLC拓扑结构和线性-谐振(L-R)调制方法,提出一种多模式宽输出三桥臂DC-DC变换器.所提变换器在全桥LLC变换器的基础上增加一组L桥臂,通过将谐振电感复用为储能电感,在谐振传递能量前对谐振腔预先储能,从而提高传统谐振模式的电压增益.所提变换器采用脉冲宽度调制-脉冲频率调制(PWM-PFM)策略,具有高、中和低3 种电压增益模式,拓宽了输出电压范围,且具有在全负载范围内软开关、环流小的优点.详细介绍了3 种模式下变换器的工作原理,利用时域法推出增益公式,并对器件参数和闭环控制方法进行设计,最后通过搭建一台输入 400 V,输出 125～500 V 的实验样机验证了理论的可行性.
Multi-mode three-bridge DC-DC converter for wide voltage output range
Aiming at the low voltage gain of traditional LLC resonant converter under heavy load opera-tion,it is difficult to achieve wide range output.At the same time,when working at low gain,the switc-hing frequency is high,the switch loss is large,and the circuit efficiency is low.Combining the full-bridge LLC topology and the linear-resonant(L-R)modulation method,a multi-mode wide-output three-bridge DC-DC converter was proposed.In the proposed converter a set of linear-bridge was added based on the full-bridge LLC converter.By multiplexing the resonant inductor into an energy storage inductor,the resonant cavity was stored before the resonant energy was transmitted,thereby improving the voltage gain of the traditional resonant mode.In the proposed converter the PWM-PFM modulation strategy was a-dopted,and three modes were realized including high-,medium-and low-voltage-gain,which broadens the output voltage range,and has the advantages of soft switching and small circulating current in the full load range.The working principle of the converter in three modes was introduced in detail.The gain for-mula was derived by the time-domain method,and the device parameters and closed-loop control method were designed.Finally,an experimental prototype with input of 400 V and output of 125-500 V was built and verified feasibility of the theory.
DC-DC converterhigh gainthree-bridgemulti-modewide range outputsoft-switching
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万方数据
维普
