[電力電子] Cuk Converter的設計

在Converter的設計中，Cuk converter是很一個很好的例子，它利用兩個電感跟一個電容以及二極體和類比開關，可以成功地達到：
1.   增加或減少DC voltage。
2.   顛倒電壓的極性。
下圖所示為一個典型的Cuk converter電路，我們可以很由開關的兩種狀態，來分析這個電路的行為：

我將分析這個電路的過程，整理為三個步驟：
(i) 先將MOSFET開關切換分成兩種狀態，每一種狀態電感被充電時的跨壓，以及電容被充電時流過電容的電流。
(ii)  再由開關切換的Duty Ratio，還繪製電感跨壓對時間的作圖，以及流過電容的電流對時間的作圖。
(iii)   對於電感，可以Apply “volt-second balance principle”，對於電容可以apply “capacitor amp-second balance”，來求出平衡狀態下，電感電流跟Duty Ratio的關係，和求出電容跨壓跟Duty Ration的關係。我的想法是：之所以感興趣的是電容跨壓，是因為右邊C2電容充多飽，會影響最終輸出的電壓值。
(iv)   有了(iii)所分析的數據，DC conversion ratio當然可以畫出。由DC conversion ratio跟Duty ratio的關係，可以知道理論上可以控制MOSFET開關切換的速度，來達到任意大小的電壓輸出，但輸出的電壓極性跟輸入電壓相反：

(v)   上面幾點討論直流，接下來必須討論直流成分之外的震盪。利用以下的公式：

如此就可以分析在直流成分上震盪的ripple斜率。

整體而言，以我對這個電路的想法，我將此電路理解為，如果在MOSFET的Source跟Drain導通的狀態下：

C1放電。
若MOSFET在OFF的情況下：

C1電容跑到左邊去充電了。

[電子學] 把BJT當Diode

在上圖中，兩個BJT從地往上拉了兩倍，假設 = 0.7V，總共就可以將電壓拉高1.4V。

[電子學] MOSFET的Channel Length Modulation

趁著休息的時間，記錄一下MOSFET中的高階效應。
Channel Length Modulation即為MOSFET中的Early Effect。MOSFET在Saturation區可以作為電流源，然而由於Channel長度跟Drain端與Source端的電壓差有關，造成Drain跟Source電流也會跟著改變：

由於Body跟Source接在一起，所以當加大，Drain端跟P-substrate之間的空乏區會加大(因為逆偏)。所以造成通道長度下降，因此數值加大，於是造成提高。因此I-V特性線通過pinch off point時，並非水平線：

[新詩] 依然擁有快樂

不記得我有拋棄過樂趣，

不記得我曾在哪裡拾起悲傷的碎片。

心中沒有傷痕，

依然擁有快樂。

A Story About Hero

Have you ever felt proud and happy that people like you and trust you so much?

Once upon a time, there was a hero lived in a high high mountain. Whenever he was aware of the danger people encountered, he showed himself. All the children and adults like him , people just cannot imagine their city without him. He can use power of fire, water and air to destroy and create everything, he is so strong that all the evil things afraid of him, and his kindness and goodness made everybody respect and trust him.

One night a girl in the village woke up and heard a soft noise, she thought there was something standing outside, she looked outside from the window, there was a man bending down to the floor, she saw some smoke was coming from his body , the situation seemed cannot be controlled and the man seemed helpless. The little girl walked outside and poured the stranger some water, she asked “Are you all right?” the man looked at the girl who saved him and fainted before he can say a word.

Three days later, the man recovery from the illness and told the little girl an amazing story. He was the hero that everybody admired and respected. “But how can you be hurt ? you have superpower!” the girl asked. “There isn’t superpower in this planet, all my abilities are relatively common.” The man said.

“But they saw --- “ girl said.

“It just some chemical and physical tricks, and I always appeared in the strong winds and powerful storm, especially when an hurricane hit .” the man said.

“No ! you’re lying !”the girl looked angry and frightened.

“You saved my life, I must tell you the truth.” man said.

“But so many magic things you’ve done ---“ girl said.

“All the magic need lots of hard work, I always prepared a very long time to fulfil a task.” man said.

“So you say you’ve done so many goodness for us by risking your life?” girl said.

“I am afraid so.” man said.

“Why ? girl asked.

“There are always good and evil exist simultaneously, I believe I am standing on the right side, by helping sad and weak people, I felt peace in my mind. I have knowledge and I am strong, It’s must be my duty to be a hero ---“ man said.

“But someday you’ll be getting old ---“ girl said.

“Don’t be worried, little girl, there’s always superheros in every generation.” man said.

The girl was crying and crying, for the nonexistence of superpower? Or for the kindness the man did? Nobody knowed.

It was said the hero change his outlook for sometime. Last time people saw the hero got long shiny black hair, brown eyes and fair skin standing in the strong winds .