具適應性電壓調控之電阻式平衡超級電容充電器

本論文提出一具適應性電壓調控技術的充電器，並結合了電阻式平衡方法。適應性電壓調控技術的概念為偵測充電負載的電壓，以動態地調整降壓直流-直流轉換器的輸出電壓。由於轉換器的輸出做為充電電路的電源，因此可降低充電路徑上元件的功率消耗，而有效的提升能量轉換效率。本充電器有三種充電模式：涓流(TC)-定電流(CC)-定電壓(CV)。依據負載的電壓不同，充電器將自動切換到相對應的充電模式，如此可以避免超級電容溫升。本論文採用串聯方式同時對多顆超級電容充電，如此可節省電路面積，抑或可減少充電時間。由於每顆超級電容的特性不同，將導致充電電壓不平衡的問題。本篇所提出的平衡機制是將各個超級電容與開關並聯。當每一超級電容的電壓充到額定值時，藉由其並聯開關的導通，不讓該顆超級電容繼續充電以避免電壓過充。本論文晶片以TSMC 0.35μm Mixed-Signal 2P4M Polycide 3.3/5 V製程實現。轉換器的輸入電壓為5 V，外接電容及電感分別為10 μF及4.7 μH，操作頻率為1 MHz。超級電容的額定電壓為1.8V，涓流充電電流為50 mA，定電流充電電流為500 mA。從模擬結果顯示超級電容的過充電壓可有效地被抑制在20 mV以內。轉換器的輸出則會隨著超級電容電壓上升而跟著增加，最後穩壓在3.65 V。具適應性電壓調控之充電電路最高效率達87.22%。適應性電壓調控技術與電阻式平衡方法可有效地提升充電電路的效率，並避免超級電容有過度充電的問題。

關鍵字

充電器；適應性調控；電阻式平衡；超級電容

並列摘要

This paper proposes a charger circuit with an adaptive voltage control technique and resistive-balancing method. The concept of the adaptive voltage control technique is to detect the voltage of the charged load, leading to dynamically adjust the output voltage of the buck converter. Since the output voltage of converter is as a supply voltage for the charger, the power consumption of the component on the charged path can be reduced for enhancing the efficiency of power conversion. The charger has three charging modes: trickle current (TC), constant current (CC), and constant voltage (CV). According to the voltage of the charged load, the charger automatically swaps the corresponding mode, resulting in preventing super-capacitors from temperature rising. A series charging schematic is used to charge multiple super-capacitors simultaneously to reduce the area of the charger or save total charging time. However, the properties of each super-capacitor are different, making charging voltage unbalancing issue of the super-capacitors. A proposed balancing mechanism is to use a switch in parallel with a super-capacitor. When the voltage of every super-capacitor reaches the nominal rating, its corresponding parallel switch will be turned on to stop charging for preventing the super-capacitor from overshoot voltage. The chip is implemented with TSMC 0.35 μm Mixed-Signal 2P4M Polycide 3.3/5 V CMOS process. The input voltage of the converter is 5 V. The off-chip inductance and capacitance are 4.7 μH and 10 μF, respectively. The switching frequency is 1 MHz. The rating voltage of the super-capacitor is 1.8 V, and the trickle and constant charging currents are 50 mA and 500 mA, respectively. The simulation results show that the overshoot voltage of the super-capacitors can be effectively restricted in 20 mV. The output voltage of the converter is increased with the rising voltage of super-capacitor. Finally, the output voltage of the converter is 3.65 V. The maximal efficiency of charger circuit with adaptive voltage control achieves 87.22%. The adaptive voltage control technique and resistive-balancing method can effectively improve the efficiency of charger circuit and prevent super-capacitor from overcharged issue.

並列關鍵字

charger ； adaptive control ； resistive-balancing ； super-capacitor

參考文獻

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具適應性電壓調控之電阻式平衡超級電容充電器

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