The Design Of Buck-Boost LLC Converter With Wide Input Voltage Range And High Efficiency

With the rapid development of electric vehicles,data centers,communications and other fields,there is an increasing demand for DC-DC converters with wide input voltage range and high efficiency.The BuckBoost LLC converter has excellent performance in high-frequency and miniaturization.But how to impove the input voltage range and efficiency should be studied.The soft-switching of switches cannot be realized with the traditional control method of BBLLC.To solve this problem,firstly,determined the best bus voltage of BBLLC.Secondly,the model of duty and phase is established to ensure that the soft-switching of switches can be realized with wide input voltage range.In order to improve the efficiency of BBLLC,there are three methods used.(1)Calculate the number of inductance turns,and select the appropritate magnetic core.Second,according to the Dowell model,the optimal copper thickness of the winding is determined.Finally,according to the eddy current field simulation of different winding structures in Maxwell,and the suitable parallel structure of inductance windings can be determined,which reduce the copper loss of inductor.(2)According to the turns radio of transform,the winding structure of transformer of the smallest magnetomotive force and the optimal copper thickness can be determined which can reduce the copper loss of transform.(3)By simplifying the calculation expression of the phase shift P,the optimal phase shift P control strategy is proposed.The strategy reduce the current effective value and the loss of switches.Based on the above analysis,a prototype of Buck-Boost LLC converter with input voltage range of250V-425 V and output of 24V/10A-50 A is built.The soft-switching of primary switches can be realized with input voltage range from 250 V to 425 V.The peak efficiency of the BBLLC can achieve 95.3%.