摘要
针对传统LLC谐振变换器在宽电压范围应用中存在开关工作频率范围宽、整体效率较低等问题,该文提出一种多模态超宽输出双LLC谐振变换器。该变换器基于可变拓扑思想,通过一次侧半桥、全桥逆变切换以及二次侧桥式、倍压整流切换,构造出四种不同增益范围的工作模式,实现了超宽输出电压范围,所用开关管在全功率范围内均具有较好的软开关特性。为进一步提高工作效率,针对所提变换器设计一种脉冲频率调制与脉冲宽度调制相结合的混合控制策略。基于SiC开关器件,设计并搭建一台输出电压40~480 V,最大功率为480 W的原理样机,验证了所提变换器的可行性和有效性。
LLC resonant converters have become a research hotspot in wide-voltage DC-DC converters with superior soft-switching characteristics,high efficiency,and high power density.Due to the wide switching operating frequency range and low overall efficiency,traditional LLC resonant converters are unsuitable for wide voltage gain applications.Designing an LLC resonant converter is imperative.This paper proposes a variable-mode ultra-wide LLC resonant converter based on the topology reconfiguration concept,achieving an ultra-wide output voltage gain range of up to 12∶1.By reconfiguring half-bridge/full-bridge circuits and full-bridge/voltage-doubler rectifiers,the converter contains four operating modes with different voltage gain ranges:series-connected half-bridges(SCHB),single half-bridge(SHB),dual half-bridge(DHB),and mixed bridge(MB).The converter’s efficiency is improved while the cost is reduced through the multiplexing of power devices.The equivalent circuits are presented for its four operating modes,and the operating stages and waveforms of the MB mode are analyzed.The voltage and current relationship equations in the MB mode are derived.Subsequently,the voltage-gain expressions for each operating mode are deduced,the voltage gain curve of the converter is plotted,and the voltage gain range is determined.The converter contains five power MOSFETs,and each can achieve zero voltage switching(ZVS)turn-on in all operating modes.To further enhance the overall efficiency of the proposed converter under the operating conditions of a wide output voltage gain range,a hybrid control strategy tailored to this converter is proposed.The hybrid control strategy introduces pulse width modulation(PWM)based on the traditional pulse frequency modulation(PFM).The converter operates with PFM in SCHB,SHB,and DHB modes and PWM in MB mode.The converter determines the operating mode according to the load conditions and then determines the MOSFETs’operating frequency and duty cycle.In practice,the converter must operate in a continuous gain range,and mode switching is required when the output voltage reaches the switching point.Considering the existence of ripple and jitter in the output voltage,adding a hysteresis loop comparison in the switching process is necessary.Adding PWM simplifies the design of the resonant parameters and minimizes the variations in output voltage gain caused by load changes.Finally,based on the working principle of the converter,the design method for key parameters is given.An experimental prototype with a maximum power of 480 W and an input voltage of 200 V is designed and constructed based on silicon carbide(SiC)devices.Experimental results show that the proposed converter can realize an ultra-wide output voltage range of 40 V to 480 V,with a peak efficiency of 94.9%;each of the power MOSFETs can realize ZVS turn-on in all operating modes,which verifies the feasibility of the topology and control strategy.The proposed converter can be adapted to applications with a wide output voltage gain,such as electric vehicle charging under the CHAdeMO standard or similar standards.
作者
张俊涛
林国庆
Zhang Juntao;Lin Guoqing(Fujian Key Laboratory of New Energy Generation and Power Conversion Fuzhou University,Fuzhou 350116 China)
出处
《电工技术学报》
北大核心
2025年第24期8052-8065,8079,共15页
Transactions of China Electrotechnical Society
基金
福建省发改委科技项目(00389102)
晋江市福大教园区发展中心科研项目(2019-JJFDKY-37)资助。
关键词
LLC谐振变换器
多模态
宽输出电压范围
双变压器
LLC resonant converter
variable-mode
wide output voltage gain range
dual-transformer
