全電流控制高頻切換直流轉直流降壓式電源轉換器

Abstract

在可攜式電子產品的應用上，高效能和小型的電壓轉換器在提供系統電源上扮演非常重要的角色。為了減少輸出級濾波器的面積，提出高頻切換的直流轉直流降壓轉換器來達到元件整合的功能。然而，對傳統電流控制模式之直流轉直流降壓轉換器來說並不適合在高頻切換的操作，因為使用到運算放大器之子電路其頻寬會被限制住。也就是說，由於電路頻寬的極限造成不正確的操作且無法跟上系統的操作頻率。為了保證電壓轉換器可以操作在高切換頻率下，全電流脈波寬度調變控制器在本論文中被提出了。

由於使用了全電流脈波寬度調變控制器，因為少了外部補償元件使得操作電路將會變的較簡單，且控制訊號全都轉換成電流形式讓訊號相加變得直接。為了能提供高效能電源電壓，也是其中一種電流模式控制技術的全電流脈波寬度調變控制器將可得到較佳的線調節率和負載調節率。

本篇論文實現了20MHz的全電流控制高頻切換直流轉直流降壓式電源轉換器，且以台灣積體電路製造股份有限公司點三五微米互補式金氧製程來實現，輸入電壓範圍從3.0伏特到4.0伏特，其負載調節率及線調節率分別為0.18356mV/mA和48.5V/V。系統特色為可使用較小的外部濾波元件且得到較快的暫態響應，其中電感大小只需200nH、輸出電容值只需5μF。非常適合於可攜式電子產品之電源管理。

For portable electronic device applications, high performance and compact size voltage regulator plays an important role to provide system power. To reduce the size of output filter, a high switching dc-dc buck converter is presented to achieve high integration. However, the conventional current mode DC-DC buck converter is not suitable to high switching design because the sub-circuits, which uses operational amplifier, restrict the bandwidth. That is to say, the limitation of circuit bandwidth causes incorrect operation and can not follow the system switching frequency. To ensure the switching regulator can operate at high switching frequency, the current domain PWM controller is presented in this thesis.

Owing the current domain PWM controller, the circuit implementation becomes simple and there are not any external compensation components. The control signals are transformed to current form to process addition of control signal directly. For providing a high performance supply voltage, the current domain PWM control is one of current-mode technique to get good line and load regulations.

In this thesis, a high switching DC-DC buck converter in current domain control with frequency 20MHz is implemented. The test chip was implemented by TSMC 2P4M 0.25-μm CMOS technology. Input operation range varies from 3.0V to 4.0V. The load regulation and line regulation are 0.18356mV/mA and 48.5mV/V respectively. The system features smaller output filter. That is, the inductor and output capacitor values are only 200nH and 5μF respectively. Fast transition response is achieved and demonstrates the design suitable for power management in the portable devices.