The Parameter Selection Of Flyback Switching Power Supply's Main Circuit

Switching power supply is often called the high efficiency and energy saving power. It can keep the output voltage stable by controlling the switch-off time ratio and has many excellent features, such as small volume, light weight, high efficiency, low power, small ripple, low noise, easy expansion, high degree of intelligence. As one kind of switching power supply, the flyback swithing power supply has the advantages of simple structure and low cost. The topology of flyback is widely used in the output power between 5W and 150W. However, there are still many problems to be solved on the flyback switching power supply, such as, the choice between continuous mode and discontinuous mode, high output ripple voltage and noise voltage, serious electromagnetic interference problems, etc. These problems are caused by several factors, including the main reason of setting the main circuit parameters. Therefore, it is very important to select and optimize the parameters of the flyback switching power supply's circuit reasonably, which can improve the application performance of switching power supply and achieve the goal of saving energy.First of all, this thesis explains the background and significance of the topic of this research. Meanwhile, the classification of switching power supply, the application and development of flyback swithing power supply is introduced. Then, this thesis does some research on several important problems such as continuous conduction mode and discontinuous conduction mode, and analysizes the advantages and disadvantages of two modes by selecting the power devices, the size of transformer volume and output filter, etc. In the meantime, this thesis introduces the selection of switch devices, the capacitance parameters of filters and the design of transformer. Besides, this thesis simply analysizes the parameters selection of primary and secondary circuit's design of flyback switching power supply.Finally, this thesis takes an example of flyback switching power supply with 30W and 12V. And corresponding simulation is done by using POWER 4-5-6 and verifys the feasibility and superiority of selected parameters.