Research On Current Sharing Technology Of Linear Constant Current Source Based On MOSFET

In some special application fields such as PV,lasers and micro-thrusters,because of characteristics or some physical indicators such as temperature,the impedance of the load changes very fast,which puts higher requirements on the drive power supply.The drive power supply needs to have lower ripple and pole Good dynamic output performance.Linear-constantcurrent-sources have the advantages of high output stability,low ripple,and excellent dynamic characteristics.and occupies an important position in laser driving and other fields.In this application,for improve the output capability of the linear constant current source,a structure in which multiple MOSFETs are connected in parallel is used.However,due to the difficulty of unifying the operating point of the MOSFET and the physical characteristics of the device,this structure has the current unevenness problem of the MOSFETs in parallel,which leads to the unsatisfactory effect of the method of improving the output capability of the linearconstant-current-sources through the MOSFETs in parallel.Aiming at this problem,this paper has conducted an in-depth study on the current sharing technology of parallel linear MOSFETs.First,through the analysis and modeling of MOSFET parameters,the mechanism of line current imbalance in MOSFET parallel structure is theoretically analyzed,it also demonstrates that the main cause of current imbalance is the inconsistency of MOSFET physical parameters caused by process and manufacturing errors.Combined with thermal simulation analysis,the necessity of taking effective current sharing measures is demonstrated,and the single-MOSFET overheating burnout caused by the uneven current sharing of MOSFETs can be effectively improved only by branch closed-loop feedback.Secondly,in order to solve this problem,this paper quantified the degree of MOSFET parallel uneven current problem through simulation,and modeled a linear-constant-currentsources,on this basis,proposed a solution to the uneven current problem: source resistance Law and branch closed loop method.Through simulation,the effectiveness of the proposed source resistance method and branch closed-loop method is verified.Finally,a linear-constant-current-sources experimental platform of 5 MOSFETs in parallel was built,and a comparative experiment without current sharing measures,source resistance method and branch closed loop method was conducted,its verify that there is a serious uneven current problem when MOSFETs are connected in parallel,and The branch closed-loop method has obvious effect of current sharing,and this method has high innovation and practical value.