Research On High Current Multi - Output Switching Power Supply

With the rapid development of power electronics technology,more and more electrical equipment are applied to the computer,communications,aerospace and other industrial fields.In order to provide a more reliable and stable power supply system in electrical equipment,the same power supply equipment can provide multiple levels of output voltage at the same time,as the output voltage is decreasing and the load current is increasing.In this situation,for the traditional single-stage converter,a big gap is appeared between the input and output voltage,resulted in transformer coil coupling large leakage inductance,the converter efficiency is too low and so on,it is detrimental to the circuit optimization design.Obviously,it has been unable to meet the high-voltage input low-voltage high-current multi-output circuit design requirements.According to the analysis of several typical circuits for multi-output power supply,this paper gives a two-stage circuit structure composed of two kinds of isolated and non-isolated topologies.The half-bridge inverter circuit with isolation topology and buck circuit with a non-isolated topology are selected though mathematical theories analysis.Two stages are mentioned with the procession of the DC/DC conversion.Firstly,the pre-isolated converter reduces the high input voltage to a certain range by a fixed duty cycle,making it the bus input voltage of the post-stage circuit.Secondly,the step-down circuit reduces the output to the desired waveform by re-buck and closed-loop regulation,and finally,the paper completes the conversion process of the high-voltage input low-voltage output.In order to cope with the problem of low efficiency at high current output,synchronous rectification technology is introduced in the double rectifier circuit and buck circuit.Replace the commonly used rectifier diodes with MOSFET to reduce the line loss.SG3525 and TL494 are used before and after the two-stage circuit control chip respectively.The proposed two classic pulse generation controller verified by simulation.Finally,in order to verify the reliability of the proposed structure,this paper gives a trial input of a 150V~180V DC,the switching frequency of 100 k Hz,three output were 24V/2.4A,9V/4.5A,5V/2.5A.Experiments show that the output voltage,current ripple small,stable and dynamic performance are well,which is consistent with the theoretical analysis.