應用在供給射頻積體電路電源系統之具有快速參考電壓追蹤技術的電流模式升-降壓直流-直流轉換器

Abstract

在無線通訊市場近幾年來發展迅速，在各種無線通訊產品中，不論是系統的家用無線電話、無線區域網路、個人無線通訊系統、及藍牙應用產品等等，射頻功率放大器在整個無線通訊系統都是非常重要的關鍵性元件。在傳統發射器系統，功率放大器都採用固定偏壓的方式。當輸入訊號為時變的波包訊號時，無論波包振福大小都維持相同的供應電壓會造成低振幅區過大的直流功率損耗，以致效率低落，因此隨波包訊號改變供給電壓即可提高功率放大器的效率， 切換式直流/直流電壓轉換器具有極高的轉換效率，但是其頻寬受限於切換式轉換器的切換頻率，相對的，線性電壓調變器具有相當高的頻寬，但其效率比切換式直流/直流電壓轉換器低許多。因此前人提出了利用切換式直流/直流電壓轉換器和線性電壓調電器並聯或是串聯的方式來提高功率放大器的效率，這有效的提升了PA供應電源的效率，但目前提出的方法中切換式轉換器都是單純的降壓轉換器，因此在PA的輸入電壓比電池電壓高時，這些電路都無法工作，為了增加電池的使用時間，因此電池的可以利用的電壓範圍變的極為重要。 本論文實現一個應用在供給射頻積體電路電源系統之具有快速參考電壓蹤技術的電流模式升-降壓直流-直流轉換器，利用內部補償來達到節省成本、縮小體積、整合度高的目標。控制器會偵測目前電池輸入電壓以及設定輸出電壓自行調變在降壓、升壓，並在轉換期間輸出可以平穩而不受影響。此外轉換器操作在高切換頻率來使整體系統頻寬增加，並具有快速的根據參考電壓來改變輸出電壓的功能以提高功率發射效率。此轉換器以台灣積體電路製造股份有限公司點二五微米互補式金氧製程來實現，輸入電壓範圍從4.5伏特到2.7伏特，輸出電壓範圍從4.5伏特到1伏特，此外轉換器操作在5MHz。

Recently, wireless communication portable devices are increasing. High efficiency radio frequency power amplifiers (PAs) are critical components in many products, like wireless LAN, personal wireless communication system, manufactures using Bluetooth, and so on. Traditionally, linear PAs are implemented by “backing off” the PA, so that their average output power is well below the amplifier saturated power. Unfortunately, this decreases the average efficiency. Therefore, technique like envelope tracking could increase the efficiency of PAs. High efficiency voltage conversion can be obtained with a switch-mode inductive DC/DC converter, but its bandwidth is limited due to practical switching frequency. Alternately, linear regulators enable higher bandwidth at the cost of efficiency. Therefore, someone propose a modulator which combines linear regulator with a switch-mode converter in series connection or parallel connection. This method increase efficiency successfully. However, the switch-mode converter in this modulator is only a pure buck converter. When the supply voltage is higher than the battery voltage, this modulator could not work normally. In other words, extending battery life becomes an important issue. In this thesis, the proposed Current Mode Buck-Boost Converter with Fast Reference Tracking Technique in RF Amplifier Supplying Systems aims to lower down cost, reduce the chip size and increase the integration, inner compensation and high switching frequency. The regulated output and enhanced control accuracy are guaranteed during mode transition. Besides, the converter could modulate the output voltage fast. This converter is implemented in TSMC 1P4M 0.25-μm CMOS technology. The input voltage ranges from 2.7 to 4.5V and adjustable output voltage option from 1V to 4.5V. The switching frequency is designed as 5 MHz.