單電感雙輸出直流降壓轉換器與雙電源自適應截止時間發光二極體驅動器

Single Inductor Dual Output DC-DC Buck Converter and Twin Bus Adaptive Off-time LED Driver

林瑞民(Rui-Min Lin)

指導教授 ： 陳信樹

國立臺灣大學/電機資訊學院/電子工程學研究所/碩士(2017年)

https://doi.org/10.6342/NTU201700097

摘要

在傳統DC-DC電源供應電路中，若需要使用兩組電源，就必須使用兩組DC-DC轉換器來供應電源，但隨著目前3C產品逐漸縮小大小，在電路板上的外部被動元件勢必需要做簡化或是進一步地做到IC中，而常見的做法就是將電阻或是電容做到IC當中，而電感部分因為準確度的關係，通常不會做到IC中，因此為了節省電感的面積，則會使用共用的方法來減少額外面積消耗，單電感雙輸出的DC-DC轉換器因此而產生。然而共用同個電感會造成許多的問題，其中最大的問題就是輸出電壓會有漣波產生，若是發生在穩態時稱做穩態交錯漣波，若是發生在暫態時則稱作暫態交錯漣波。此篇論文在第二章結提出了方法來減少這兩個輸出電壓漣波，藉由兩個輸出的回授比較與控制，適當的在穩態與暫態上調整兩者的責任週期，即可減少這兩種漣波的影響。此晶片是以台積電 0.35μm 2P4M 3.3V/5V Mixed Signal CMOS 製程製作。依據實驗結果，本晶片操作在切換頻率為1 MHz；暫態回復時間為34.28 μs；穩態交錯漣波大小皆小於50 mV；暫態交錯漣波則小於6.8%；當負載電流為460 mA時，最高效率為90%。
第三章節提出了雙電源SAR邏輯控制之自適應截止時間發光二極體驅動器。
近年來環保節能的意識在社會上越來越被注重，因發光二極體比傳統的日光燈更加省電，近年來已將許多電燈產品改成發光二極體做使用。而在驅動發光二極體時，最注重的就是其效率與精準度，因發光二極體為長時間使用之用品，若效率不良反而會造成許多能量的損耗，且違背省電節能的出發點；另外，發光二極體的亮度與上頭流過的電流呈現指數性的關係，如果要精準地控制發光二極體之亮度，勢必得控制好其流過的電流。一般發光二極體之驅動方式常見的有線性控制與切換式控制，其中兩者的效率以後者較為勝出。而在切換式控制方法下，主要又分成遲滯電流控制與峰值電流控制，前者擁有高精準度的優點，但卻有效率差的缺點；後者擁有高效率的優點，但卻有精準度差的缺點。因此為了改善峰值電流控制精準度差的缺點，在第三章提出了自適應截止時間控制方法來做動態調整精準度，另外也使用雙電源的架構來進一步提升發光二極體驅動器的效率。此晶片是以台積電0.25μm 1P5M 2.5/5/7/12/20/24/40/45/60V High Voltage Mixed Signal CMOS製程製作。依據實驗結果，本晶片低頻切換頻率為5 kHz，高頻切換頻率約為1 MHz；電流精準度誤差也在4%以內；當輸出功率大於8 W時，效率皆可以達到 91.8%。

關鍵字

單電感雙電流直流降壓轉換器 ； 發光二極體驅動器

並列摘要

In traditional DC-DC converter, if we need two power supplies, we should use two DC-DC converters to do it. But the products of 3C are smaller than before, the elements which are resistors and capacitors should be simplified or made on chip. However, not all elements are suitable for making on chip. For example, the inductor, if we make it on the chip, the quality factor of it would be worse than the one of off-chip. To reduce the area used by inductor, the single inductor dual output DC-DC converter has been produced. By sharing the same inductor on the circuit, it can reduce the area of PCB. However, this will cause some problems which are called cross regulation ripple. If the ripple happened in the steady-state, it will be called steady-state cross regulation ripple. If the ripple happened in the transient, it will be called transient cross regulation ripple. In chapter 2, we propose one control method to reduce these output voltage ripple. By the feedback and comparing of two output voltages, it can adjust the duty cycle of each output to reduce the effect of these two ripples. This chip is implemented in a TSMC 0.35-μm 2P4M 3.3V/5V Mixed Signal CMOS process. According to measurement results, this chip operates at 1 MHz, transient recovery time is 34.28 μs, steady-state cross regulation ripple is small than 50 mV, and transient cross regulation ripple is small than 6.8 %. The maximum efficiency is 90% when load current is 460 mA.
In chapter 3, we propose the Twin bus SAR controlled adaptive off-time LED driver. In recent years, there are more and more attention for environmental protection and energy conservation. Because the LED is more efficiently than traditional fluorescent, the used of it is popular than before. The most important of driving LED is efficiency and accuracy. The lightness of LED has the relationship with the current on it. To control the lightness of LED more accuracy, we should control the current flowed through it. There are two methods to drive LED, one is linear control and the other is switching control. The last one has high efficiency than the former one. In switching control, it can be separate into two methods, one is hysteretic current control and the other one is peak current control. The former has the advantage of high precision, but there are disadvantage of poor efficiency; the latter has the advantage of high efficiency, but there are disadvantage of poor accuracy. Therefore, in order to improve the disadvantage of peak current control, we propose a control method which is called SAR controlled adaptive off-time to enhance the accuracy of it. We also use the architecture of twin bus circuit to enhance the efficiency of LED driver. This chip is implemented in a TSMC 0.25μm 1P5M 2.5/5/7/12/20/24/40/45/60V High Voltage Mixed Signal CMOS process. According to measurement results, the lower frequency is operated at 5 kHz, the higher frequency is operated at 1 MHz, and the accuracy error is small than 4%. When output power is larger than 8W, the efficiency can achieve 91.8%.

並列關鍵字

SIDO DC-DC buck converter ； LED Driver

參考文獻

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