Design Of Four Switch Buck-boost Digital Power Module

In the communication power supply structure, the undetermined voltage drop caused by the different bus length in output side of the AC-DC converter makes the rear DC-DC converter worked in a wide input voltage range and the power transformers harder to design. To solve the problem, the non-isolation circuit called the Pre-regulated module(PRM) power supply usually be used to transform and stable voltage before the isolation circuit. This paper design a PRM controlled by DSP and based on the Four Switch Buck-Boost(FSBB) to make sure it’s high energy density. The main contents are as follows:The principle of operation and the zero voltage switch(ZVS) control strategy of the FSBB are introduced in the first. And the upper limit of inductance is design to ensure the working of pseudo discontinuous mode which can solve the ZVS problem. The presented simulation proved the design’s right. The average state space method is used to deduce the small-signal model of the FSBB worked in the pseudo discontinuous mode. And the closed loop will be design to make sure the FSBB can work stably in the three states. Bilinear method of transformation is used in this paper to discrete compensation function for the digital control.The system control strategy has been design to make sure the ZVS. In order to achieve the soft-switching, the control strategies of software and hardware will be design to make sure that FSBB will work in pseudo discontinuous mode. And those designs have been verified in the last.An experiment model machine has been made based on the above study and design. And those design and function have been verified by the results of the machine’s working. The efficiency of the power module, general higher than 96%, also has been measured to achieve the intended objectives.