Research And Design Of PFC Converter Suitable For Low Power Occasion

Currently,notebook computers and other electrical equipment using low-power power sources are widely used,causing certain harmonic pollution to the power system.Therefore,the International Electrotechnical Commission has issued the IEC60000-3-2 current harmonic standard.There are many power factor correction(PFC)technical solutions that can suppress current harmonics,but each has its own advantages in terms of performance and cost.In low-power situations,how to comprehensively consider factors such as performance and cost to determine an appropriate PFC technical solution has important research significance.Based on this application requirement,this topic explores PFC technology solutions suitable for low-power applications,aiming to provide a design reference for the application of PFC converters in low-power applications.The main work and research methods are as follows:Based on the two-stage PFC technology scheme,a two-stage PFC converter composed of a pre stage Boost PFC converter and a post stage flyback converter is studied.Its operating principle is analyzed in detail,the advantages and disadvantages of its operating mode are sum-marized,and the pre and post stage control schemes are designed.Finally,the correlation anal-ysis is verified by simulation in PSIM software.Based on the single stage PFC technology scheme,a single switch single stage(S~4)PFC converter with Boost Flyback structure,namely BF-S~4 single stage PFC converter,is studied.The principle that its PFC level can achieve automatic PFC function is analyzed,and the reason why its intermediate bus capacitance inevitably bears high voltage stress under light load is explained by numerical analysis from both steady-state and transient state.Research has con-firmed that the root cause of high voltage stress in the bus lies in the negative feedback mech-anism of the output current.Based on this,a high-voltage stress optimization circuit is proposed.Finally,relevant conclusions and optimization schemes are simulated and verified in PSIM software.In order to further verify the applicability of the above two PFC schemes in low-power situations,two 90W power supply prototypes were designed based on the design criteria of 100to 240V AC input and 12V/7.5A DC output.The parameter design and device selection process of the prototype are given,and the stability of the control loop is verified using Mathcad and Saber software.Finally,an experimental platform is built to test the input and output perfor-mance of the prototype.The experimental results show that both schemes can meet the design criteria.The power factor of the two-stage PFC converter is up to 0.991,and the total harmonic distortion is 9.602%It is suitable for power supply devices that focus on PFC performance in low-power applica-tions;The BF-S~4 single stage PFC converter has a power factor of 0.929 and a total harmonic distortion of 39.5%,which is 6.3%lower in cost and 2%higher in efficiency than a single two-stage structure.It is suitable for low power applications where cost and efficiency are important.In addition,the BF-S~4 single stage PFC converter reduces the bus voltage sudden increment by45.6%at light load,verifying the feasibility of the voltage stress optimization circuit proposed in this paper.The research results of this topic provide certain reference value for the application of PFC technology low-power applications.