Research On Multi-output Switching Power Supply With Low Load Regulation

AC-DC switching power converters are widely used in a variety of household or industrial electronic equipment due to their high efficiency,small size,low power consumption,high reliability and large output voltage range.Sometimes we will need the same power supply device with multiple different output voltage capabilities,so multi-output technology has emerged.This technology can reduce the amount of magnetic components used in the power supply,and to some extent reduce the power supply volume and reduce the power production cost.In addition,since the flyback switching power supply topology has the advantages of large input voltage range and increased transformer windings,the flyback converter is used as the main power topology.In order to avoid saturation of the magnetic core in the circuit(the primary coil inductance decreases when the core is saturated and the current on the primary coil increases,the core heat is also increased),and an air gap is required between the transformer cores.The leakage inductance of the transformer cannot be avoided.The preliminary simulation and research show that the leakage inductance of the transformer has a great influence on the load regulation rate of the power supply,and the two have a negative correlation.Therefore,designing a flyback switching power supply with a wide input voltage range and low load regulation has become a research hotspot in academia and industry.Based on the above analysis,this paper studies the four-output flyback switching power supply.The research method is to simulate the dual output switching power supply first,and then apply the structure with better effect in the dual output power supply to the four output switching power supply.However,various multi-output technologies have different advantages and disadvantages when they are used alone in terms of load regulation.Therefore,by combining these technologies,it is possible to obtain better design performance.Based on this idea,this paper proposes the idea of combining multiple multi-output technologies.The specific method is: using the transformer coupling technology for the main power topology part,designing four power output loops and one auxiliary power loop.Linear regulation technology is applied to the output loop to improve the voltage adjustment accuracy.In addition,the output loop has been improved in order to be able to obtain a large current of the normal output 2A.Weighted feedback is used for the feedback loop part to further improve the control accuracy.Considering that the circuit has four output loops and one auxiliary power loop,if all of them are included in the closed-loop feedback system,the complexity of the feedback loop will be greatly increased,and the interference between the output loops will increase.Therefore,this paper uses partial weighting.The way of feedback.From the comparison of several sets of simulation results,it is known that in the high-frequency switching circuit,the leakage inductance of the transformer is an important factor in the voltage adjustment accuracy control.Therefore,this paper also studies the parasitic parameters of transformer leakage inductance.By selecting the simulation model of the transformer,it is more practical.Based on Saber software simulation and comparison of different leakage inductance parameters,the results show that the four-output power supply designed in this paper has a load regulation rate of less than 2% at the four output terminals under the wide input voltage of 200-285 V.