Research On The Parallel Current-sharing System Of Switching Power Supply

With the power increasing of the electrical equipments, the output power of switchingpower supply is also increasing. In order to meet the needs of high-power, the parallel modularpower supply is often used in practical applications. This way reduces the current and thermalstresses of MOS tube, and improves the stability and reliability of the power system. However,only a simple parallel way can’t guarantee stability and reliability of the power system. Thereexists current-sharing problem between these modules. So, the effective current sharingcontrol strategy must be introduced in the parallel power system. Therefore, the digital parallelcurrent-sharing system of switching power supply is studied and designed.First of all, a single-ended flyback switching power supply is designed as the powermodule in the parallel circuit，based on the research and analysis the related theory andimportant technology of switching power supply. Mainly to complete the design of specificcircuit parameters, including pre-stage circuit and rectifier filter circuit、EMI filter circuit、RCDclamp circuit、high-frequency transformer、secondary rectifier filter circuit、LC filter circuit etc.Secondly, in order to prevent power oscillation caused by the load mutation or variation ofthe input voltage, it is proposed one kind of the feedback compensation network based on smallsignal transfer function. In this process, through Matlab software the frequency domainsimulation is used to get the best parameters of the feedback compensation circuit. The circuit issimulated by the software of Cadence16.3and the rationality of the parameters is validated.The power supply prototype is set up according to the design parameters, it is tested andresearched through experiment.Finally, several common parallel switching power supply current control methods areintroduced and analysed. MCU ATmega16is selected as the current controller, and thehardware circuit and part of the program is designed to realize the current-sharing control. Itcan be seen that the system is stable and the current-sharing performance is good throughsimulation and experimental analysis. So the system achieve the expected design requirements.