應用於光電能量擷取且具最大功率追蹤之單電感雙輸出升壓轉換器

Abstract

本篇論文提出一個針對光電能源擷取之低功耗單電感雙輸出之直流轉直流升壓轉換器以應用在無線感測網路。將太陽能電池(在不同照度下開路電壓在0.95V 至 1.25V 範圍之間)所擷取到的最大功率提供給輸出負載做使用。該轉換器可提供 1.8V 的穩定電壓給後端的類比及數位電路，並同時將多餘的能量儲存在另外一路的儲存電容或 3.7V 鋰電池。本篇論文使用自適應峰值電感電流脈寬頻率調變控制方式，此控制方式可抑制輸出電壓漣波會隨輸入電壓增加而增加的現象。此外，本篇論文亦使用二階段啟動方式來節省晶片面積以適用在單系統晶片的應用。透過所提的啟動機制，啟動時間可大幅縮短至 10 毫秒以下。此電路在量測上最高可達到 78%的轉換效率、同時搭配一開路電壓法的最大功率點追蹤電路(MPPT)來獲取最多之光能源，可達到最大功率點的追蹤效率高於 99%。此晶片是以聯華電子公司零點一八微米互補式金氧半製程來實現，並且晶片面積僅1.4 mm2，切換頻率為 10-20KHz。

A solar-powered on-chip low-power single-inductor dual-output (SIDO) DC-DC boost converter was implemented for a wireless sensor node system. It manages power from a photovoltaic (PV) cell with open voltage from 0.95 V-1.25 V under different lux.The converter provides regulated 1.8 V output for the analog and digital circuits while storing the excess energy in a storage capacitor or 3.7 V Li-on battery (VSTOR). The adaptive-peak-inductor-current (APIC) control method is used to mitigate the output voltage ripple variation issue at different input voltage. Besides, a two-step startup procedure is proposed to reduce the chip area for SoC application. By the proposed startup mechanism, the start-up time could be shorten to under 10 milliseconds. A fractional open circuit voltage (FOCV) algorithm was implemented as a maximum power point tracking (MPPT) control. With this MPPT control, its peak tracking efficiency can be higher than 99%. The measurement result of the boost converter achieves a peak efficiency of 78%. The chip is implemented by UMC 1P6M 0.18μm process technology with a small area size of just 1.4 mm2, and the switching frequency is 10-20 KHz.