Primary-Side, Constant-Voltage Regulation Enables Two-Stage LED Driver With High-Performance And Low Cost
by Jin Zhu, Fairchild Semiconductor, Zhejiang, China and Yupu Tao, Fairchild Semiconductor, Shanghai, China, How2Power Today, Sep 15 2013
Focus:
A new two-stage dimmable LED driver solution based on primary-side regulation and constant voltage output (PSR-CV) in the first stage is proposed in this article. This LED driver design eliminates low-frequency current ripple yet maintains high power factor (PF) and low cost compared with existing solutions. To explain the need for this new topology, the authors devote the first few pages of the article to a discussion of market requirements for LED drivers and the existing LED driver topologies. These include the single-stage flyback with primary-side constant-current regulation (PRS-CC), the three-stage solution (PFC+flyback+dc-dc converter), and the two-stage PSR-CC (PFC stage + flyback). The pros and cons of these topologies and reasons they were developed are discussed, which sets the stage for the detailed discussion of the two-stage PSR-CV (PFC/flyback stage + dc-dc converter). The advantages and operating principles are explained and experimental results are presented for a prototype design based on the FL6961 PFC controller and the FL7701 high-voltage buck controller. Article also includes a table outlining Energy Star requirements for LED lamps with an integrated driver.
What you’ll learn:
- How to understand market requirements and topology options when designing LED drivers for LED lighting applications
- How to design a dimmable LED driver that eliminates low-frequency current ripple while achieving high power factor and low cost
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