本文提出一個高功率半橋LLC諧振轉換器空載待機效率改善的新方案，此新型電路可適用於分散式電力系統中再生能源發電系統之效率提升，主要目標是使太陽能與風力發電在各種不同的負載情況下皆可以產生高效率且穩定的輸出供應負載使用。為了達到上述目的，本文將進一步地研究串並聯諧振式電源轉換器並提出空載待機控制策略。串並聯諧振式電源轉換器主要係由對稱半橋電路搭配諧振槽及變壓器所組成，利用變頻控制改變諧振槽特性以達到輸出電壓調變之目的。相較於傳統的定頻硬切式電源供應器，串並聯諧振式電源轉換器可達到零電壓切換或是零電流切換以減少切換損耗。在實際應用中，電源供應器經常處於待機無載的狀況下，串並聯諧振式電源轉換器在此種情形下效率並不佳。而本文所提出的新型電路控制架構，可降低切換損失，提高空載待機效率。此控制電路除了以輸出電壓感測電路做為回授外，尚有偵測同步訊號的回授，可使輔助控制電路與一次側切換頻率同步操作。最後，由模擬軟體SIMetrix/SIMPLIS模擬此電路，驗證此方法確實可使LLC諧振轉換器提高空載待機效率。

This thesis presents a novel solution of improving standby efficiency applied to half-bridge high power LLC resonant converter which can be used in the renewable generation systems of the distributed power systems. The main goal is that solar and wind power can be produced in both high-efficiency and stable output to supply loads in various conditions of loads. In order to achieve the above objectives, this thesis will further study the series and parallel resonant power converters and propose light load control strategies. Series and parallel resonant power converters are mainly composed by the symmetrical half-bridge circuit with a resonant tank and transformers. Using frequency control changed the characteristics of the resonant tank to achieve the purpose of the output voltage modulation. By comparing to the traditional fixed- frequency hard cut power supplies, series and parallel resonant power converters can achieve zero-voltage switching or zero-current switching to reduce switching losses. In practical applications, the power supply is often under light load or no-load conditions. The efficiency of series and parallel resonant power converters is poor in both cases. In this thesis, the proposed control circuit can reduce switching loss and improve the standby efficiency. Except using the output voltage sensor as a feedback signal in this control circuit, there is even a synchronizing detector as a feedback signal which can make the auxiliary control circuit synchronizing with the primary side. Finally, the way to improve the LLC converter efficiency in standby mode is verified with software simulation by SIMetrix/SIMPLIS.

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