The Research On Phase-shifted Full-bridge Soft-switching DC Converter

With the development of science and technology, we put forward higher request toswitching power supply power density, efficiency and dynamic performance. By increasingthe switching frequency, we can greatly reduce the size of switching converters to improvepower density, however, the switching losses increase, electromagnetic noise increases, theswitching device voltage or current stress increase too. In order to solve these problems, thesoft-switching technology was presented. Switching converters can achieve zero-voltageswitch or zero-current switching, significantly improve efficiency, reduce electromagneticinterference by using soft-switching technology. Compared with other soft-switchingcircuit,phase-shifted full-bridge converter has a simple structure, easy to control, easy toimplement, etc.It is widely used in practice.The emergence of the microprocessor promote the development of Power electronicsconverter control technology, digital control is gradually taking place of traditional simulationcontrol. It is characterized by flexible control, the anti-interference ability strong, easy torealize intelligent power electronics system etc, and become the trend of the development ofswitching power supply. Based on the digital phase-shift full-bridge soft-switching DC-DCconverter analysis,phase-shifted full-bridge soft-switching technology and digital controltechnology have been studied.High power density, high efficiency, intelligence has become the development trend ofmodern switching power. Soft-switching technology is the efficient and effective method ofimproving switching power, the soft-switching technology applied to switching power canachieve miniaturization and high efficiency.The appearance of digital signal processorsprovide the hardware conditions for the using of intelligent control theory in switchingconverter.In this paper, a fuzzy adaptive PID controller using phase-shifted full-bridgezero-voltage and zero-current DC-DC converter was designed, and related issues werestudied.First, it introduced several types of the phase-shifted full-bridge DC-DC converter usingsoft-switching and analysed several typical topological structures of phase-shifted full-bridgezero-voltage and zero-current DC-DC converter, summarized the characteristics of all thetopologies, selected the zero-voltage and zero-current-switching full bridge Converter usingtwo diodes in series with the lagging leg for the study.Secondly, a detailed analysis has been taken on zero-voltage and zero-current-switchingfull bridge converter using two diodes in series with the lagging leg and showed theconditions of soft-switching to meet zero-voltage and zero-current-switching full bridgeconverter using two diodes in series with the lagging leg.According to the subject ofperformance requirements, the parameters of main circuit components was designed, on thisbasis, using Saber simulation software to establish the main circuit simulation model for thesimulation analysis.The results show that the main circuit parameters is reasonable to meet thedesign requirements.Then,using state-space averaging method to establish a small-signal model ofzero-voltage and zero-current-switching full bridge converter using two diodes in series with the lagging leg.The fuzzy adaptive PID controller is applied to the converter, using theMATLAB software finish the simulation of this system, the results show that the fuzzyadaptive PID controller can get good dynamic and static performance.Finally, the design of DSP-based digital control system, including the main control circuitdesign, the driving circuit design and signal conditioning circuit design. A1000W prototypewas built in the laboratory to test it,experiments were carried out by the experimentalwaveform analysis.The results show that a successful soft-switching has been achieved, theresults meet the requirements.