abstract: Switch mode DC/DC converters are suited for battery powered applications, due to their high efficiency, which help in conserving the battery lifetime. Fixed Frequency PWM based converters, which are generally used for these applications offer good voltage regulation, low ripple and excellent efficiency at high load currents. However at light load currents, fixed frequency PWM converters suffer from poor efficiencies The PFM control offers higher efficiency at light loads at the cost of a higher ripple. The PWM has a poor efficiency at light loads but good voltage ripple characteristics, due to a high switching frequency. To get the best of both control modes, both loops are used together with the control switched from one loop to another based on the load current. Such architectures are referred to as hybrid converters. While transition from PFM to PWM loop can be made by estimating the average load current, transition from PFM to PWM requires voltage or peak current sensing. This theses implements a hysteretic PFM solution for a synchronous buck converter with external MOSFET's, to achieve efficiencies of about 80% at light loads. As the PFM loop operates independently of the PWM loop, a transition circuit for automatically transitioning from PFM to PWM is implemented. The transition circuit is implemented digitally without needing any external voltage or current sensing circuit. / Dissertation/Thesis / M.S. Electrical Engineering 2014

細數過去數十年，台灣類比IC設計產業發展從無到有，從客戶不相信台灣類比IC設計公司的能力，到現在彼此成為合作夥伴，從外商完全看不起台商，到現在大家同場競技，從沒有一家類比IC設計公司上市、櫃掛牌，到現在已有近十家類比IC設計公司掛牌，台灣類比IC設計產業實在值得更多的喝采與投資人的注意。 目前為止，台灣共有二十幾家類比IC設計公司，本研究主要以民國九十四年十二月底以前上市、櫃之茂達、立錡、沛亨、安茂、富鼎先進、致新、崇貿、點晶、圓創等九家類比IC設計公司為樣本 依其八十九年至九十三年之財務報表做為預估個案公司未來成長率及獲利率的依據，利用現金流量折現法採銷售導向及盈餘導向等兩種模式，依最樂觀、最可能發生及最悲觀等三種情境，估算其實質價格區間，並與各股目前之實際股價相比較，以推論目前股價的合理性以及目前股價可能隱含的銷售成長率及盈餘成長率，另以敏感度分析將各個評價因子繪製成龍捲風圖，來觀察個別關鍵評價因子對股價的影響程度。 此外，本研究依Aaker的分析架構，針對此依產業進行外在與內在分析，包括整個產業的環境分析、產業分析、競爭對手分析、顧客分析與關鍵成功因素(SWOT)分析，以期本研究能在財務分析之外，提供投資人對類比IC設計產業ㄧ全面通盤性之分析。 最後，根據本研究之實證結果，發現過去五年個股與大盤股價作分析，ϐ值均偏高，其可能原因: 1. 類比IC設計產業(相對於數位IC設計產業)，為一新興產業，市場給予之本益比較高， 2. 進口替代效應之潛在業績成長題材，持續發酵。