以DSP晶片控制300W LLC諧振轉換器

Abstract

近幾年來，諸多電子產品都朝著小型化發展，因此要提高開關的切換頻率，可使直流轉換器中的磁性元件的面積變的更小。在維持良好效率的前提下，如何減少功率開關切換的能量損耗，便成為一個重要的課題。 本文所探討的為LLC半橋式同步整流諧振轉換器，其最大特性在開關導通的時候，可進行零電壓或零電流切換，使得開關切換損耗減少很多，其效率就可提升。架構採用分散式變壓設計，使用的DSP晶片為TMSF28027，透過數位控制器改變上下橋訊號和同步整流訊號，其輸出功率最大為300 W，輸出電壓為12 V，最大輸出電流高達25 A，最大切換頻率為160 KHz，並用兩種不同的整流策略來討論其效率的變化，電流感測同步整流法的最大效率可到達到91%左右，滿載下的平均效率也可達到84%左右。

In recent years, many electronic products development towards miniaturization, it’s necessary to increase switching frequency, so that the magnetic element in the DC-DC converter becomes smaller. How to reduce the switching loss and keep high efficiency, it will become an important issue. In this thesis investigates the LLC half-bridge resonant circuit with synchronous rectification, when the switch turns on can achieve zero voltage switching or zero current switching, and decreases the switching loss. The system based on TMSF28027 DSP chip, and use digital PID controller. The maximum output power is 300 W, the average output voltage is 12 V, and the output current as high as 25 A. The maximum switching frequency is 160 KHz, and use two different measures to realize synchronous rectification. In current sensing measure, the maximum efficiency can reach about 91%, the average efficiency can reach about 84% under the full load.