應用於平板顯示電源管理晶片之低輸出電壓擾動直流直流轉換器

Abstract

目前平板移動裝置的產品需求量大,其顯示屏的功能需求也越來越高. 應用在平板裝置顯示屏上的電源管理系統頃向使用整合型的電源管理晶片, 也就是將多個電源單元整合於一個晶片當中, 包括降壓電路以及升壓電路. 但由於手持裝置電池的容量有限, 而效率的提升也有極限, 為了要讓手持裝置能夠長時間使用, 唯有將顯示電路的操作電壓降低以減少消耗. 但操作電壓降低的同時, 降低相對應的降壓電路的輸出電壓的擾動就變得十分重要, 因為過大的輸出電壓擾動有可能會造成系統的異常. 另外在手持裝置的顯示系統上, 升壓電路的輸出電壓擾動降低也很重要, 因為過大的輸出電壓擾動會影響到顯示屏上的輸出品質, 造成消費者在使用上有不好的影響. 因此本篇論文因此針對降壓電路以及升壓電路的輸出電壓擾動做改善, 在降壓電路輸出擾動的降低上, 藉由低點偵測技術來達到降低穩態時輸出電壓的變化, 再加上突波抑制技術, 來降低負載變化的所產生突波, 實驗結果顯示穩態時的輸出電壓變化可以縮小至3豪伏特, 而突波電壓變化可以小於10%以下, 約93豪伏特. 而在升壓電路的輸出電壓抑止上, 以動態開啟控制技術為基礎, 利用暫態改善技術控制工作週期, 使得在暫態時的輸出電壓變化能夠有效的降低. 實驗結果顯示和傳統的控制方式比較, 在輕載到重載以及重載到輕載可以分別改善30%以及44%.

Nowadays, the market requires lots of products manufactured with tablet mobile devices, and requires more and more functions in the display panels. In the display panel of tablet mobile devices, power management system prefers to using power management circuit chip, which means that the system integrates several power units in a chip, such as buck and boost DC-DC converters. However, with limited battery capacity and low efficiency of handheld devices, operation voltage of display circuits has to be lowered to decrease the consumption, and to keep the battery running longer. Meanwhile, when operation voltage is lowered, decreasing the disturbance of output voltage in the corresponding buck converter is very important. Since excessive disturbance of output voltage may cause the system abnormal. Besides, in the display system of handheld devices, decreasing the disturbance of output voltage variation in the boost converter is very important as well, because excessive disturbance of output voltage will degrade the display quality, and lead to bad experience of the products. Therefore, this thesis is about the improvement of output voltage variation in the buck and boost converters which are applied in tablet display system. Low output voltage variation will be achieved in buck converter by proposed valley detection and overshoot reduction technique. And, based on the hysteresis current control, duty cycle will be controlled by proposed technique in the transient state. Therefore, output voltage variation of load transient state in boost converter can be reduced efficiently. The experiment result shows load regulation can be improved to 3mV, and output voltage variation can be decreased to lower than 10%, about 93mV in buck converter. Moreover, the output voltage variation of boost converter can be lowered to 30% and 44%, compared to conventional control during load from light to heavy and heavy to light, respectively