本論文提出一具鎖相迴路控制之全橋LLC諧振式直流電源轉換器，其係利用鎖相控制技術，使功率開關工作於零電壓切換狀態。

當輸入電壓、輸出電壓以及輸出功率相同時，相較於半橋LLC諧振式轉換器，全橋式電路除具低切換損失、高效率之優點，且適用於較大功率之應用。當其負載電流改變時，將造成諧振槽之諧振頻率點與電壓增益隨之變動。然而，傳統變頻控制方式，無法精確的調控功率開關之操作頻率，甚至使操作頻率低於諧振頻率點，導致功率開關失去零電壓切換之特性，增加切換損失，降低轉換器之效率。本論文所採用之鎖相迴路控制技術，係藉由鎖定LLC諧振槽之輸入電壓以及並聯諧振電感之電壓相位訊號。再依據此電壓相位關係，鎖定諧振槽之諧振頻率，作為最低操作頻率基準點，來調整操作頻率，以得到所需之輸出電壓，且使操作頻率高於諧振頻率，確保功率開關元件恆具有零電壓切換之特性。

此外，本論文將植基於諧振槽之功率因數、電壓増益以及電感比例三者之間的關係，提出LLC諧振槽元件之設計流程。藉由此設計方式可確保輸入電壓改變時，電源轉換器依然能維持較佳的效率。

最後，實做一輸入電壓300V～400V、輸出電壓48V、輸出電流12A之雛型電路，俾以驗證本論文所提出之鎖相控制迴路應用於全橋LLC諧振式直流電源轉換器之可行性

This thesis presents a full-bridge LLC DC-DC resonant converter with phase-locked-loop control (PLL) scheme, which is able to track the resonant frequency of the LLC resonant tank as the reference frequency point for the control of the frequency-modulation.

Since the resonant frequencies of the LLC resonant tank are dependent on the load conditions and component deviations, unlike conventional frequency-modulation control, PLL control is utilized to ensure that the operating frequency keeps in the zero-voltage-switching (ZVS) region for obtaining low switching loss. Furthermore, in order to fulfill in high-power applications, the full-bridge converter is required instead of half-bridge circuit in this thesis.

Moreover, in order to have high efficiency within wide input voltage range, high power factor for the LLC resonant tank should be ensured. The parameters of the LLC resonant tank are designed according to the voltage gain and input-power factor of the LLC resonant tank.

Finally, the prototype circuit of the full-bridge LLC resonant converter, with 48V output voltage at 12A output current, is built to verify the performance of this proposed full-bridge LLC DC-DC resonant converter with PLL control.

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