Design Of Two-Stage Pulse Power Supply Based On Current Mode Control

Lasers are widely used in military,medical,industrial and other fields,in which laser power supply is an important part of laser devices.As one of the laser power sources,the size and working performance of pulsed laser power supply will affect the use range of the laser.The pulse power supply can improve its charging rate while achieving miniaturization.By comparing and analyzing the topology and control strategy of the laser pulse power supply,in order to reduce the volume of the power converter and improving the charging rate,this thesis adopts a two-stage circuit topology and a current-mode control method for the pulse power supply.Firstly,the two-stage main circuit topology and control method of pulse power supply are determined.According to the working requirements,the interleaved parallel boost APFC circuit is selected as the front stage of the power supply.On the one hand,the APFC circuit can improve the power factor at the power grid side and reduce the harmonic pollution to the power grid;on the other hand,the interleaved parallel structure can reduce the input current ripple,reduce the volume of the energy storage inductor and prolong the service life of the output capacitor.The isolated DC/DC circuit of the power supply stage can not only adjust the output voltage,but also quickly charge the storage capacitor.After comparing and analyzing the advantages and disadvantages of different current-type control strategies,the front stage of the power supply adopts the average current control with good correction effect;the post stage of power supply adopts the peak current control based on UC3846 control chip,which has a fast response speed and can effectively suppress the magnetic bias of transformer while improving the charging rate of capacitor.Then,the parameters of the main circuit and the components in the control circuit are calculated and designed.The two-stage main circuit includes the design of energy storage inductors,input capacitors,output capacitors and high-frequency transformers;selection of switching devices,diodes,and rectifier bridge devices.In order to improve the anti-interference ability of the circuit,an integrated control chip is used,and the control circuit mainly includes a frequency setting circuit,a sampling circuit,a soft-start circuit and a compensation circuit.The average current control of the front stage adopts the voltage and current closed-loop control,and the voltage and current loop compensation circuits need to be designed.Due to its inherent characteristics,the poststage peak current control needs to add a slope compensation circuit to avoid the instability of the circuit caused by the change of the switching duty cycle.Finally,the working principle of the pulse power converter is verified by simulation and experiment.The simulation model was built in Simulink simulation software to verify the feasibility of the circuit working principle.The power factor of the input terminal of the power converter was improved,and the charging time of the output terminal to the energy storage capacitor met the requirements.A prototype experimental platform was built,and the feasibility of the power supply working principle and control method was verified by experiments.