Research On The High Stable Constant Current Source Of 30A

As a kind of stable power supply,constant current source is widely used in scientific research and industrial field.In particular,the constant current source with high stability and large current has an urgent demand in the superconducting magnet,aerospace,DC charging and precision measurement.The large current measuring system developed by National Institute of Metrology needs a current more than 10 A with the stability better than 10 ppm as standard source.While at present,the output range of most constant current source is commonly small,and the stability is not good when outputting large current,so it is difficult to meet the requirement of high precision measurement and other applications.In this paper,a design scheme of high stable constant current source with 30 A maximum output is proposed,the main aspects of research work are as follows:1.In this paper,the domestic and foreign research status of constant current source is analyzed.Then a new design of constant current source is proposed after comparing the advantages and disadvantages of linear and switching circuits,which uses switching power supply module to regulate voltage and then adjust the current with a linear circuit.To ensure that the stability of output current is better than10 ppm,the design of linear constant current circuit based on series negative feedback is presented to guarantee the output current be adjusted in time,and the selection of key components and their influence on the stability of output current are also analyzed.2.A high stable reference voltage generator module is designed.The standard voltage is provided by the high stability reference chip,and the reference voltage output can be adjusted by the high precision DA conversion chip under the control of MCU.After testing,it is shown that the stability level of output reference voltage from 0.1V to 0.3V is better than 5ppm.3.In order to solve the problem of high power consumption,high heat output and difficulty of stabilizing the current,multiple power MOSFETs in parallelingconnection are used as the regulate tube,and systematic analysis on factors affecting MOSFETs in paralleling work are presented as well.At the same time,a special cooling device is designed,which can effectively improve the stability of the current.Finally,the output current of the constant current source is tested.The results in an hour show that the stability of 30 A output current is 7.25 ppm,which can meet the requirement of this project.