| LED as a new light source with high efficiency,long life,small size,energy saving,easy to dimmer,etc.,is gradually becoming a new generation of efficient green lighting.The design of a high reliability,high efficiency,high power factor,low cost and long life of driver has become the key to LED lighting system.Switching power supply due to meet its requirements is gradually becoming its first choice.However,the traditional switching power supply requires electrolytic capacitors to balance the input and output power,which is the main factor that restricts the life of the driver.In this thesis,we study a kind of single-stage LED driver without electrolytic capacitor.By analyzing the existing strategy of minimizing the storage capacitor,the research direction of the topology optimization is determined.In this thesis,the working principle of Flyback converter is briefly analyzed,and the power flow and the working principle of the three-port circuit are discussed.By studying the internal power flow of the circuit topology,a circuit topology based on the three-port structure is proposed.The new circuit topology adds an auxiliary winding,so that the power can flow between the input,output and auxiliary winding.The excess energy stores in the capacitor when the input power is greater than the output power,and the energy is released to the load when the input power is less than the output power.At the same time in order not to use electrolytic capacitor,the storage capacitor of auxiliary winding should be designed in the form of large voltage ripple.In this thesis,the working principle of the new circuit topology is analyzed in detail.According to the working principle of the circuit,a detail analysis of the working condition of the circuit is deduced.The key parameters and device parameters of the main circuit are determined by this condition,and the corresponding control circuit is proposed.The correctness and feasibility of the circuit are verified by the simulation results by Saber software. |
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