High Power LED Driver Without Electricity Capacitor

LED driver has developed rapidly, but most of them have electrolytic capacitor to store energy. Electrolytic capacitor will severely limit the life of the LED driver, so it’s important to design LED drivers without using electrolytic capacitor. By analyzing the structure and performance of existed LED drivers, this article designs a LED driver of 250 W to fulfill the actual requirement. It has the features of long life, constant voltage constant current output and electrical insulation. The main work of this thesis is as follows:Firstly, the scheme of the LED driver is decided. This article introduces the types and performance index of LED drivers to illustrate that appropriate structure and drive mode of LED drivers can improve life and ability. After analyzing many implement methods of different parts of LED driver and comparing the advantages and disadvantages, the half-bridge structure with single capacitor is chosen and its performance and potential problems are analyzed with a simulation. The control circuit is well designed and its failures are analyzed. And the current loop compensation is improved to make better stability and wider bandwidth. According to the actual requirements, this article improves the start-up circuit and verifies its performance by a simulation.Secondly, this article finishes the analysis and calculation of circuit’s parameters to realize the performance. According to the parameter calculation results, appropriate components are selected for the power circuit, control circuit, drive circuit and compensating network circuit. The thesis also shows the derivation needed for transformer’s magnetic core selection and winding design. For the compensating networks, detail design steps are given and the result is proved by simulation. Finally, a prototype with expected features is build to verify the effectiveness of design.