Research On Wide Input Low Voltage High Current Output Converter

Distributed power supply had more and more applications in the field of communications,country defense and military.As a bridge connecting high-voltage bus and low-voltage bus,the middle bus converter has a wide input voltage,low output current characteristics,so the need to develop a Small volume,high efficiency intermediate bus converter.The main topology of the power supply is Buck cascade push-pull while the secondary side using synchronous rectification.The pre-Buck is the pre-regulator,which is used to output the stable voltage so that the post-stage push-pull converter can be based on the fixed input voltage to optimize.In this paper,the principle of Buck-cascade push-pull topology is analyzed in detail,and the topology principle is verified by simulation.The design of the main circuit parameters is carried out.It is necessary to optimize the design of the transformer and have some requirements for the winding method.The output capacitance by using tantalum capacitors and ceramic capacitors in parallel,both to ensure the value,but also reduce the ESR on the output.A small signal model of the system is established,and the average current control mode is adopted to control the converter in closed loop.Push-pull converter MOSFETs voltage stress is usually twice the input voltage,in order to reduce the spike voltage of push-pull MOSFETs,a resonant soft-switching push-pull circuit is proposed.By using the resonant capacitor and the leakage inductance of the transformer,the switch is working in the soft switch state and the advantages of soft-switching push-pull and ordinary push-pull circuit are proved.The principle analysis of the hardware circuit is verified by the construction of the hardware circuit.A prototype of 180 V-400 V input and 12 V/600 W output is built and the cutting and starting characteristics of the prototype are analyzed,it proved that the circuit has good dynamic performance.The efficiency of the circuit in the case of rated input voltage full load output is 92% or more,in the half load output is reached 93.5%,have a good realization of the power supply requirements.