| Due to the inherent advantages,including the ability of both voltage step-up and step-down,positive output voltage,and reduced number of passive components and voltage stress of the power devices,the four switch buck-boost(FSBB)converter has been attracting people's attention.It is suitable for wide range of input voltage occasion,and it also has been widely used in the telecom power supply.So,How to control the converter to make sure it has high efficiency and good dynamic response in the whole input voltage range is one of the hot research spots.The traditional control strategy of FSBB converter has many problems such as multi-mode switching,dual-frequency drive and soft-switching implementation.Based on the traditional control strategy,this paper proposes a control strategy "Mixed One Mode ZVS" of the four-switch Buck-Boost converter,which work in only one mode,there is no problem of multi-mode switching,and can achieve zero-voltage switching of the four switches,enabling high frequency operation while minimizing switching losses and maximize efficiency.For the proposed control strategy,this paper presents three frequency mode control methods:constant frequency,frequency conversion and segmented frequency conversion.The advantages and disadvantages of these three frequency mode control methods are analyzed and compared,and the key parameters of each frequency mode control method and the realization scheme of digital control are introduced in detail.And a 48V(36?75V)input,48V(20?60V)output and 300W rated power prototype is built and tested to verify the effectiveness of this proposed control strategy.The experimental results show that in the control strategy the four-switch Buck-Boost converter work on only one mode and can achieve zero voltage switching of the four switches in the full input voltage,the full output voltage and the full load range.The circuit in the high-frequency operation at the same time switching loss is low,high efficiency,dynamic performance. |
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