A LED Driver Circuit With High Efficiency, High Power Factor And High Performance

Since incandescent lamps’ gradual exiting from the lighting market is under way, the LED lamps’popularity is burgeoning. Because of its nonlinear characteristic, the LED lamps need special power supply to drive. Whether the power supply is good or not, will affect the lifespan and performance of the LED. So it is significant to do more research on LED power supply. Therefore, the LED power supply with high efficiency, high power factor and high performance is becoming more and more popular. In this article, a configured LED lighting system will be introduced, which includes the power supply and dimming module. The power of the power supply is100watt. The input voltage is100-200v (AC), the output is36v (DC). In this article, two types of LED power supplies will be presented. The first type is an isolated converter with two stages. The second power supply is a single Buck circuit. And then a double excitation power supply is presented as the the prioritization scheme of the single Buck circuit. As to the dimming module, a PWM dimming scheme has been designed to achieve a wide dimming range from0to255.What’s more, SPWM dimming scheme has been simulated and verified to realize constant curreut.This project has completed the following tasks:(1) At the beginning of this article, comparison was taken between several types of lighting sources. Then the advantages of LED and the present situation of LED power supplies were raised. After that, the optical properties, thermal properties and electrical characteristics of LED were introduced. Based on this, the connection types and the dimming methods were presented and strongpoints and defects were listed respectively.(2) Presented two types of power supplys.The first type is an isolated converter with two stages-the first stage is a boost circuit to realize PFC, and then a half bridge circuit to step-down the voltage and isolation. For the second power supply, only a single Buck circuit was designed to achieve high PF and low output voltage. Considering the non-isolated of the second power, another double excitation power supply is provided. Their working principles were elaborated. The selection of the key parameters was presented. What’s more, simulations were conducted for all the power supplies by Psim and experiments were taken on the prototypes for the two types of power supplys respectively. The experimental results are consistent with the simulation very well. Contrasted the two power supplies and summarized in the end.(3) Designed a PWM dimming scheme based on single chip microcomputer, which can realize the local and remote control at the same time, and achieve a wide dimming range and constant current. Both the hardware and software design were provided.To attain constant currut, SPWM dimming scheme is introduced.