Design of High Performance Regulated Charge Pump Circuit

高效率，低輸入電壓直流-直流轉換在可攜式設備的應用中是關鍵的電子裝置，電池的使用時間可因此而最佳化。在低電池電壓的彩色顯示行動裝置中，電荷幫浦電路已是最普遍且重要的直流-直流轉換器。 本論文介紹並實現一系列的調節式電荷幫浦設計技巧，使得行動裝置顯示器的電源系統具有高效率、高性能和小體積。論文描述包含行動顯示器之電源系統、個別控制方法、及各階層電路，並總結了高性能、高效率之調節式電荷幫浦設計之挑戰，且加以突破。而主要設計的目標專注於高效率、高性能、小體積、低成本使其適用於行動顯示器驅動之應用。 文中成功地展現出三種創新之調節式電荷幫浦電路包含了電壓及電流調節式設計技巧及量測結果，分別為 : 一、正及負六倍壓之高壓電荷幫浦及其電壓調節電路，可使用在薄膜電晶體液晶顯示器之閘極驅動電源，在行動裝置電池電壓範圍內並滿足驅動閘級所需負載下可使輸出電壓調節在+17.5V及-14.5V。新提出的九個相位控制法可減少一個外接幫浦電容(flying capacitor)使得系統成本降低。特別設計之比較器可使負壓調節方法比傳統方法來得具有更高的準確度、低晶片面積及功耗。 二、低輸出漣波設計於兩倍壓調節式電荷幫浦內可有效降低輸出漣波，故可用於液晶顯示器之源極驅動電路的電源供應。多相位操作方法可進一步降低輸出漣波至28mV在20mA負載、1μF之幫浦及負載電容之下其可輸出4.5V至5V電壓。此外更推導出此設計之回路方程式可用來預測漣波相對於負載之變化 三、提出高效率電流調節式電荷幫浦可使用於驅動白光發光二極體，新的架構可較傳統省去電流調節電路，進一步縮小晶片面積。 總體而言，論文提出之方法已證實可實現一個用於行動裝置顯示器驅動電路的電源系統之高效率及小體積的直流-直流轉換器。Motivated by emerging portable applications that demand ultra-low-power hardware to maximize battery run-time, and high-efficiency low-voltage DC-DC conversion is presented as a key electrical device. Charge pump circuit has been shown to be a critical DC-DC converter for low-battery voltage technology in mobile equipments with color displays. This thesis introduces and demonstrates an array of regulated charge pump design techniques which make the power system of display high efficiency, high performance, and compact. The primary design challenges to high-efficiency high-performance regulated charge pump are summarized. Design techniques at the power delivery system, individual control system, and circuit levels are described which help meet the stringent requirements imposed by the portable environment. The research is focused on portable display-driving applications, where small size, low cost, and high energy efficiency and performance are the primary design objectives. The design and measured results are reported on three regulated charge pumps which include voltage and current regulations, and successfully demonstrate the design techniques of this thesis. Description as follows: 1. High-voltage positive and negative charge pump as ± 6×VDD with voltage regulated to powering gate drivers of TFT-LCD drivers for their individual loads, can provide up to 17.5V and -14.5V in overall input voltage range of mobile equipments. Nine-phase clocks pumping is proposed to reduce one external flying capacitor for cost-efficient. Special design for the negative regulated scheme using differential difference comparator has been introduced, which increases accuracy of the negative regulated voltage, and reduces power consumption and chip area. 2. The lowest voltage-ripple design applied to a regulated voltage doubler is used to reduce the output ripple voltage for powering source drivers of TFT-LCD drivers. Multi-phase operation is proposed to minimize the output voltage-ripple, and this is with a 28 mV output voltage-ripple by up to 20mA load current. It delivers a regulated voltage from 4.5V to 5V with 1μF flying and load capacitors. Design equations and closed-form expressions for low ripple regulated charge pump are presented. 3. The high power-efficiency current-regulated charge pump is proposed to drive WLED for extension at low battery voltage and decreasing chip area. As the result, the approach presented in this thesis is evidently viable for realizing compact and highly efficient DC-DC converters for used as low battery-voltage power systems to powering display drivers in portable electronic applications