Research On High Efficiency Combined Double Half Bridge DC Converter

In power electronic devices,soft switching technology can effectively reduce the power loss of switching devices and improve converter efficiency.Because of the rapid development of soft switching technology,switching power supplies can be developed in the direction of high frequency and small volume.Phase Shift Control The ZVSPWM full-bridge converter relies on the resonance between the leakage inductance of the transformer and the junction capacitance of the switch to achieve zero-voltage turn-off of the switch,which is widely used in medium and large power conversion applications.But at the same time,it also has several problems,such as the loss of zero voltage switching characteristics of the switching tube at light load,the circulation of the primary side,and the large voltage oscillation of the secondary side rectifier diode.These problems limit the further promotion of the converter.Aiming at the existing problems of traditional phase-shifted full-bridge converters,this paper studies a new type of combined double-bridge DC converter.Each half of the converter includes two switching tubes,a transformer and a DC blocking capacitor,and the two half bridges share a set of rectifier diodes.The converter adopts a phase shift control strategy to adjust the output voltage by controlling the phase shift angle of the driving signals of the two bridge arm switches.It can effectively expand the load range to achieve soft switching characteristics,reduce the oscillating voltage of the rectifier side diode,and solve the primary side circulation problem.Compared with the traditional phase-shifted full-bridge converter,the converter can be better applied to applications with a wide load range.In this paper,the effectiveness of the proposed control is verified by simulation software and experimental platform.By establishing the open-loop simulation model of the system,it is verified that the converter can realize soft switching characteristics in a wide load range.Secondly,the small signal is modeled on the converter,and the duty cycle to output voltage transfer function is obtained.The network has corrected the system;finally,the rationality of the controller design is verified in the closed-loop simulation system.Experiments show that the efficiency of the converter is up to 97.7%,and the efficiency is 92% when the load drops to 20%,which proves that the combined double-half bridge DC converter has high efficiency.