Research On High Voltage DC Power Supply With Cascade Topologies

Since the high voltage DC switching power supply(HVPS)has the advantages of high efficiency,small size,fast re sponse,safe and reliable,etc.Hence it is widely used in the research of engineering and experiments,like medical X-ray machine,traveling wave tube and electronic accelerator and others.The current research status of HVPS is analyzed in this thesis,a HVPS with hig h variat ion rat io and low ripple is proposed based on the existed scheme of HVPS.In this thesis,cascade topology is used as the main power circuit to achieve the power transmissio n,the Buck cascade Push-Pull converter and voltage mult iplier circuit is used to raise the voltage.The cascade topology is used to solve the interference problem that exists in the single-stage topology when the duty cycle changes.The working principle of the ent ire topology is analyzed in detail,whose small sig nal model is also established to provide the theoretical basis for the stabilit y analysis of the control circuit.The factors that affect the peak voltage of the Push-Pull converter are analyzed,and it is pointed out that the high peak voltage is caused b y the high parasit ic parameter of the transformer.Based on this,it is proposed to use the resonant capacitor to discharge the leakage inductance of the transformer,which can achieve ZVSZCS-t ype soft-switching,so as to achieve the purpose of reducing the peak voltage.The corresponding simulation and experimental platform are built to verify the feasibilit y of the soft-switching circuit.For the half-wave voltage doubler exists the problem that the ripple of it s output voltage is huge,the working principle of using linear regulator source to reduce the ripple under the low voltage condit ion is analyzed,and it is pointed out that its effect of ripple suppression is not obvious.Hence this thesis proposes a scheme which uses a linear regulator to suppress the output ripple under the high voltage condit ion,and a ripple measurement circuit of high voltage is designed.The experimental results verify the suppression effect of the output ripple.In this thesis,the stabilit y of the designed HVPS is analyzed a nd deduced,and the compensation network of the pre-stage circuit is designed to improve the stabilit y of the system.On the basis of the above theory,the experimental prototype is developed.The correctness of the designed circuit is veri fied by the experimental.