Development Of Soft-Switching Converter With Synchronous Rectification

In recent years,with the rapid development of the electronic information industry,various electrical devices have gradually become smaller and lighter.At the same time,switching power supplies as their core components are also evolving toward high frequency,high efficiency,and high power density.In order to improve the efficiency of the switching power supply,reduce the losses generated inside the power supply,and make it applicable to low-voltage,high-current applications,this paper studies a soft-switching converter with synchronous rectification.The converter adopts a phase-shifted full-bridge circuit as a topology,and utilizes a soft-switching technology to realize the zero voltage turn-on of the primary side switch tube to reduce the switching loss of the circuit.For the low-voltage and high-current output characteristics of the converter,three rectification circuits are compared and the full-wave rectification is finally selected as the output rectification circuit topology.And synchronous rectification technology is applied to it to reduce the rectification loss of the circuit.In this paper,the working state of the converter in various stages is introduced in detail,and the key issues are studied.The influence of resonant inductance,dead-time and light-load conditions on soft-switching is analyzed,and the corresponding design method is given.A MOS tube with a low on-voltage drop is used instead of an uncontrolled diode to perform the rectification function,and a control logic for a synchronous rectification drive signal is designed so that the rectification can be achieved in the conduction and commutation phases of the rectifier tube.The problem of voltage oscillation and voltage spikesin the synchronous rectifier are analyzed,the cause of the oscillation is found,and several methods for solving the voltage oscillation and spikesare proposed.Then the system software and hardware were designed.To output a stable DC voltage,a PID control algorithm was used to close the system through the DSP28335 minimum system board,and a simulation model was built in MATLAB.Finally,according to the design content,an experimental platform of lkW/30V output was built,and the experimental results were analyzed.Among them,the full-bridge circuit realizes soft switchto reduce the switching loss;synchronous rectification also greatly reduces the rectification lossof circuit.The overall efficiency of the final converter is significantly improved,which verifies the feasibility of the above theoretical analysis.