| Summary: | 碩士 === 國立成功大學 === 電機工程學系 === 106 === In this paper, the research topic is study and design of digital primary-side controlled flyback LED drivers. The main functions of LED drivers in analog: constant on-time control power factor improvement, quasi-resonant efficiency improvement and constant current control, are discussed in detail. Then, change the issue to digital control, and explore the differences between the various implementation methods.
According to the results of the literature research, a digital primary-side feedback LED driver, which conforms to the functions and specification standards of commercial products, is proposed in this paper. For the delay error compensation, this work proposes a new implementation method. Compared with the past practice, On-Time Compensation can fully exploit the advantages of the constant on-time control, directly adjust the switch on-time to solve the delay problem. It can not only omit the complex operations required by past practices but also achieve the same effect. In addition, the constant on-time control is improved by digital frequency limit mechanism. The optimization effect can be achieved without detecting other signals to reduce the cost. Finally, the verification is completed with the FPGA and the PCB system.
This work is the first fully digital control LED driver in the academia, including the main functions required for today's commercially available products. In terms of performance, power factor (PF) and total harmonic distortion (THD) of this work are better than industry's digital products; Line Regulation is ±3% and Load Regulation is ±2%. Both of them are nearly the same to other products, but there is still room for improvement
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