A Study On The High Step-Down LED Driver Circuit

The research on effective and energy-saving power sources plays an important role since environment-friendly idea coming into our life. The LED lightning can provide many advantanges among economy and energy, which deserves deep research.This paper systematically discuss the circuit structure, and the operating mode of the conventional single-stage PFC technique. The analysis results show that the Buck-Flyback single-stage PFC converter provides the advantages of high power factor, wide input voltage range, low intermediate capacitance voltage, high step-down input-to-output voltage, which broaden extensive application prospects.Many high step-down converters in dc-dc provides a good step-down feature, but it also leads to the thermal problem of the switch and low efficiency.To overcome the drawbacks of the aforementioned S4(Single stage single switch) converters but preserve their advantages,this paper proposes a new topology that integrates a buck PFC and buck dc-dc cells,which features the reversed polarities among the dc-link capacitor and the output capacitor.It differs the traditional cascaded Buck converter and single switch cascaded Buck converter in circuit structure,then,a detailed analysis on the formation process of topology,the simplest structure, and working principle were analyzed,as well as its intermediate capacitance voltage characteristic, input-to-output voltage ratios and the auxiliary diode conduction conditions. Finally, a dc timing simulation model was set up, and the simulation and experimental results validate the correctness of theoretical analysis.Finally, the working principle and circuit charistics,such as the PFC,efficiency, intermediate capacitance voltage characteristic,of the converter in the ac input were introduced, and the establishment of a ac simulation model and the experiment prototype validate the correctness of the aforementioned analysis.The actual data results show that the maximum efficiency of the new converter can be up to 88.3% and the power factor is greater than 0.95, which can well meet the IEC61000-3-2 Class D harmonic standards. The experimental waveforms shows that the new converter has good step-down performance, low dc-link capacitor voltage and constant power factor among the ac input range, as well as its design flexibility and comparable large duty cycle among high step-down transfomerless converter.