| At present,the performance of multi-output flyback converter has been well improved.However,in many applications,how to solve or balance the contradiction between the volume of power and the output and the number of isolated output terminals,the contradiction between the output voltage precision and the cross adjustment rate and efficiency is still the difficulty in the design process.In order to effectively solve or balance the two contradictions mentioned above,based on the optimization of the traditional multi-channel output weighted feedback circuit,a design method of multi-channel output isolated switching converter with multi-optical coupling isolated weighted feedback control is proposed.And the way to do that is,Use weighted control and LDO(Low Drop Regulator)combined control method of low dropout linear regulators)to balance the precision of output voltage and the contradiction between the cross regulation and efficiency,the photoelectric coupler union control to achieve the original between side and the side and the output of isolation,flyback structure used to balance the bulk of power source and the nominal power and the contradiction between isolated output number.The emphasis of the design method is the reasonable design of the weighted coefficient of each channel.The weighted coefficient of each channel depends on the number of output terminals and the output power of each channel.For the convenient design of flyback converters with various requirements,a relation expression between the weighting coefficient and the output power of each channel is deduced and fitted.A four-channel isolated output flyback converter is designed.The main circuit uses a larger weight coefficient to ensure higher accuracy,and the secondary circuit uses a smaller weight coefficient to ensure that the voltage at both ends of the LDO input and output whether it’s in the stable range of low voltage difference,and the final output accuracy is guaranteed by LDO.In terms of hardware design,devices such as planar transformers,SIC switches and diodes are used,which efectively improves the overall efficiency of the power supply and reduces the volume of the power supply.The simulation results of the proposed multichannel output flyback converter under the simulation environment of PSIM circuit show that the multichannel isolated output is realized,the cross adjustment rate of the multichannel output flyback converter is less than 1%,and well achieved the goal of precision and efficiency.A prototype of a four-way isolated output flyback converter was made and the performance test was completed.The cross-regulation rate was less than 3%,and the output voltage accuracy and power efficiency met the design specifications. |
