具有高速電流感測器及晶片電感之極小尺寸直流對直流降壓式轉換器

Abstract

本論文的內容是設計一個具有內含電感且操作於虛擬連續導通模式之降壓式直流電壓轉換器。由於可攜式電子產品的設計越來越小型化，電路的各式零組件無一不是朝此設計方向推衍。在高效能切換式直流電壓轉換器中，電感元件一直佔有相當比例的電路體積，本論文將說明利用積體電路製程中的金屬層實現轉換電感於矽晶片上以縮減整體電路體積，實務上選擇UMC 1P6M 0.18μm製程來實現晶片電感。由於晶片電感實現的電感值約為0.2μH，我們以20MHz的切換頻率避免操作於過大的電感漣波電流以及輸出漣波電壓。另外考慮到輸出電流供應能力，使用2 phase的系統架構提升整體輸出電流。系統在輕載狀態選擇脈波頻率調變模式以提升輕載效率，重載則選擇脈波寬度調變模式提供較快的反應速度。開關切換策略選擇虛擬連續導通模式，使之擁有近似連續導通模式中較小的電感漣波電流，又同時攫取非連續導通模式容易補償的優點。

This paper proposes a compact size DC-DC buck converter because of on-chip inductors and minimized external components. Multi-phase, high switching frequency and pseudo continuous conduction (PCCM) techniques achieve the possibility to implement on-chip inductors. The effective inductance is about 0.2μH. Due to high switching frequency above 20MHz, it is a challenge to have a highly accurate current sense for high performance of converters. Simulation results demonstrate that the accuracy of high-speed current sensor is about 95%. Besides, mode switch between pulse width modulation (PWM) and pulse frequency modulation (PFM) alleviates the limitation of high-speed current sensor in case of light load condition. Compact size converters’ design is an advanced technique as a power module for system-on-chip (SOC) designs.