完善的共振式轉換器，包含了電路結構簡單，易於控制，低切換損失，低電磁干擾(EMI)，其中還導致吸收到更多增益。本論文研發高效率共振式轉換器採用改良型串聯負載共振式轉換器為直流電源供應器，改善傳統切換型直流電源供應器的性能。LLC轉換器可做為直流電源供應器，由於低噪音、高功率與高效率。實現零電壓切換(ZVS)的功率開關與零電流切換(ZCS)的整流二極體於滿載時，LLC共振式轉換器操作在串聯共振頻率，由於共振的行為，如果切換頻率小於串聯共振頻率時，所有開關都在零電壓切換時打開與整流二極體在零電流切換時閉合。驗證所提出的一個輸入150 V與輸出 169 W的轉換器做為標準給出模擬結果與實際結果做比較。提出的LLLC拓樸的能量轉換效率高達98.85%。提出的LLC共振式轉換器具有結構簡單成本低易於控制效率高。它特別適用於能量轉換效率高的電源供應器上。 The well-established advantages of resonant converters, including simplicity of circuit configuration, ease of the control scheme, low switching losses, and low electromagnetic interference (EMI), among others, have led to their attracting more interest. This thesis develops a highly efficient resonant converter with an improved series-loaded resonant converter for dc power supplies to improve the performance of traditional switching-mode dc power supplies. A LLC converter can be used as a dc power supply due to its low EMI noise, high power integration and high efficiency. To realize zero voltage switching (ZVS) for power switches and zero current switching (ZCS) for rectifier diodes at full load, the LLC resonant converter are operated below the series resonant frequency. Based on the resonant behavior, all switches are turned on at ZVS, and rectifier diodes are turned off at ZCS if the switching frequency is less than the series resonant frequency. The feasibility of the proposed converter is verified with a 150 V input and 169 W output prototype. A comparison between the simulations and the practical results is also presented. The energy conversion efficiency of the proposed LLC topology is as high as 98.85%. The proposed LLC resonant converter has a straightforward structure, low cost, easy control, and high efficiency. It is particularly suited to the energy conversion applications in high efficiency dc power supply systems.