A family of isolated Buck-Boost converters is proposed to be suitable for the application,where the input voltage range is wide and galvanic isolation is required in this paper.Full-Bridge（FB）-Boost converter is analyzed as one of the typical topologies.Considering the duty cycle loss,an improved two-edge modulation strategy based on phase-shift control is proposed to minimize the inductor current ripple over the input voltage range.In order to achieve the reliability and efficiency of this converter,a 3-mode dual-frequency control scheme is proposed.Under the 3-mode dual-frequency control scheme,the input voltage is divided into three regions,i.e.the low,medium and high voltage rang,and corresponding operating modes are Boost,FB-Boost and FB modes respectively.As the inductor current ripple in FB-Boost mode is much smaller,the switching frequency of the boost cell in this mode can be lowered to reduce the switching loss and further improve the efficiency.To verify the effectiveness of the design and control,a 250～500V input,360V output and 6kW rated power prototype is fabricated.High efficiency can be achieved all over the input voltage range,and the highest efficiency is 97.2%.%本文提出了一族隔离型的Buck-Boost变换器以适应宽输入电压范围并要求隔离的应用场合,以全桥（Full-Bridge,FB）Boost变换器作为其典型电路之一在文中展开分析。考虑占空比的丢失,提出了基于移相控制的双沿调制策略以减小整个输入电压范围内的电感电流脉动。为实现变换器可靠高效的工作,提出了三模式双频控制策略。三模式双频控制策略下,输入电压被分为低、中、高三个电压区间,分别对应于FB-Boost变换器的Boost、FB-Boost和FB三个工作模式。由于FB-Boost模式下电感电流脉动较小,可以降低该模式下Boost单元的开关频率以减小开关损耗,进一步提高效率。为验证设计和控制策略的有效性,搭建了一台输入电压250～500V,输出电压360V,额定功率6kW的原理样机,整个输入电压范围内变换器都具有较高的效率,最高效率为97.2%。
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