# 論文筆記: A Fourth Generation of LCD Backlight Technology

###### tags: `問題記錄`, `lab 專案`, `論文筆記`

Update date: 2023-04

## 📌 The problem to solve
CCFL-背光 LCD 顯示器在改變放置條件下的均勻度問題
試圖探討: 均勻度差異極大（現象）的可能原因

## Paper information
* Publication Date: November 1995
* Author Bio of "Jim Williams"

James M. Williams（1948 年 4 月 14 日 - 2011 年 6 月 12 日）
是一位模擬電路設計師和技術作者，
曾在麻省理工學院（1968-1979）、Philbrick、美國國家半導體（1979-1982）和凌力爾特公司工作 (LTC) (1982–2011).[1] 
他撰寫了超過 350 篇與模擬電路設計相關的出版物[2]，
其中包括五本書、21 篇美國國家半導體應用筆記、62 篇凌力爾特應用筆記，以及超過 125 篇 EDN 雜誌文章。

威廉姆斯於 6 月 10 日中風，並於 2011 年 6 月 12 日去世。 [3]

## 📌 Performance / Power Trade-Off: The balance between the performance and power of the lamp
The only viable solution is to determine lamp performance with the display of interest.
This is the only practical way to maximize performance and ensure against overdriving the lamp, which wastes power and shortens lamp life.
##
========== 以下是翻譯 & 筆記整理 ==========
##
唯一可行的解決方案是根據感興趣的顯示器來確定燈的性能。
這是【最大化性能】並確保【不會過度驅動燈泡】的唯一實用方法，過度驅動會浪費功率並縮短燈泡壽命。

## 📌 Currents: low excitation currents
Some lamps may display nonuniform light emission at very low excitation currents.
=====
有些【燈】在【非常低的激勵電流】下可能會顯示【不均勻的光發射】。

## 📌 Wiring: The effects of heavily asymmetric wiring
Heavily asymmetric wiring to or within the display can sometimes make floating drive more lossy than grounded drive. In such cases testing in both modes is necessary to determine which type drive is most efficient.
A second advantage of floating operation is extended illumination range.
“Grounded” lamps operating at relatively low currents may display the “thermometer effect,” that is, light intensity may be nonuniformly distributed along lamp length.
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========== 以下是翻譯 & 筆記整理 ==========
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顯示器上或顯示器內【嚴重不對稱的接線】有時會使【浮動驅動器比接地驅動器損耗更大】。
在這種情況下，有必要在兩種模式下進行測試以確定哪種類型的驅動器效率最高。
浮動操作的第二個優點是擴展了照明範圍。
在【相對較低的電流下】工作的【“接地”燈】可能會出現【“溫度計效應”：即光強度可能沿燈長分佈不均勻】。
// ^ ^ ^
// 實驗條件 1 + 實驗條件 2 → 實驗結果 (現象)

## 📌 Field: The effects of imbalanced and low-intensity field
Figure 47 shows that although lamp current density is uniform, the associated field is imbalanced.
The field’s low intensity, combined with its imbalance, means that there is not enough energy to maintain uniform phosphor glow beyond some point.
Lamps displaying the thermometer effect emit most of their light near the driven electrode, with rapid emission fall-off as distance from the electrode
##
========== 以下是翻譯 & 筆記整理 ==========
##
圖 47 顯示，雖然燈電流密度是均勻的，但相關的場是不平衡的。 場的低強度，加上它的不平衡，意味著沒有足夠的能量來維持超過某個點的均勻磷光。
顯示溫度計效應的燈在驅動電極附近發射大部分光，隨著與電極的距離的增加，發射迅速衰減

##
========== 以下是翻譯 & 筆記整理 ==========
##

Dada 的歸納:

實驗條件 | associated field is imbalanced + field’s low intensity
| (相關場是 "不平衡的") (場的 "低強度")

↓

結果 | 非 "均勻磷光"： 能量 "無法" 持續地 (維持) 超過某個點 (臨界值)

↓

現象 | 具有 "溫度計效應" 的燈，
(a) 在驅動電極 (LCD 驅動 IC) 的附近發射大部分光
(b) 但隨著與電極的距離的增加，發射迅速衰減

↓ |

可能問題 | (非論文提及, 只是基於 Dada 的假設)
| 亮度不均勻

## 📌 Heat: Avoiding Heat Buildup in the Display
Avoiding Heat Buildup in the Display Several of the display components are sources for heat problems. Thermal management must be taken into account in the design of the display bezel.

[A heated display may be adversely affected; a loss of contrast uniformity usually results.]

[The cold cathode fluorescent tube (CCFT)]
(1) itself gives off a small amount of heat relative to the amount of power dissipated in its glow discharge.
(2) Likewise, even though the inverters are designed to be extremely efficient, there is some heat generated.

[The buildup of heat in these components will be aggravated by the typically “tight” designs currently being introduced.]
There is little ventilation designed into most display bezels. To compound the problem, the plastics used are poor thermal conductors, thus causing the heat to build up which may affect the display. Some current designs suffer from poor placement of the inverter and/or poor thermal management techniques. These designs can be improved even where redesign of the display housing with improved thermal management is impractical. [One of the most common mistakes in current designs is that there has been no consideration for the buildup of heat from the CCFT.]

Typically, the displays for notebook applications have only one CCFT to minimize display power requirements. The lamp is usually placed along the right edge of the display. Since the lamp is placed very close to the display glass, it can cause a temperature rise in the liquid crystal.
[It is important to note that variations in temperature of as little as 5°C can cause an apparent non-uniformity in display contrast.]

[Variations caused by slightly higher temperature variations will cause objectionable variations in the contrast and display appearance.]
To further aggravate the situation, some designs have the inverter placed in the bottom of the bezel.
This has a tendency to cause the same variations in contrast, particularly when the housing does not have any heat sinking for the inverter.
This problem manifests itself as a “blooming” of the display, just above the inverter. This “blooming” looks like a washed out area where, in the worst case, the characters on the display fade completely.

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========== 以下是翻譯 & 筆記整理 ==========
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不平衡和低強度場的影響

避免顯示器中的熱量積聚 顯示器的幾個組件是產生熱量問題的根源。 在顯示屏邊框的設計中必須考慮熱管理。

[加熱的顯示器可能會受到不利影響； 通常會導致對比度均勻性下降。]

[冷陰極熒光管（CCFT）]
　(1) 相對於其輝光放電中消耗的功率量，它本身會發出少量熱量。
　(2) 同樣，即使逆變器設計得非常高效，也會產生一些熱量。

[當前引入的典型“緊湊”設計將加劇這些組件中的熱量積聚。]
大多數顯示器邊框幾乎沒有通風設計。 使問題更加複雜的是，所使用的塑膠是不良的導熱體，因此會導致熱量積聚，從而影響顯示器。 當前的一些設計存在逆變器放置不當和/或熱管理技術不佳的問題。 即使在重新設計具有改進的熱管理的顯示器外殼不切實際的情況下，也可以改進這些設計。 [當前設計中最常見的錯誤之一是沒有考慮 CCFT 的熱量積聚。]

通常，筆記本應用的顯示器只有一個 CCFT，以最大限度地降低顯示功率要求。 燈通常沿著顯示器的右邊緣放置。 由於燈離顯示屏玻璃很近，會導致液晶溫度升高。
[重要的是要注意，小至 5°C 的溫度變化都會導致顯示對比度出現明顯的不均勻性。]

[由稍高的溫度變化引起的變化會導致對比度和顯示外觀出現令人反感的變化。]
為了進一步加劇這種情況，一些設計將逆變器放置在邊框的底部。
這傾向於導致相同的對比度變化，特別是當外殼沒有任何用於逆變器的散熱裝置時。
這個問題本身表現為逆變器上方的顯示器“泛光”。 這種“暈染”看起來像一個褪色區域，在最壞的情況下，顯示屏上的字符會完全褪色。

## 📌 Placement of the Display Components

One of the things that can be done is to design the inverter into the base of the computer with the motherboard. In some applications this is impractical because this requires the high voltage leads to be mounted within the hinges connecting the display bezel to the main body. This causes a problem with strain relief of the high voltage leads and thus with UL certification.

### Design / Experimental Condition
[One mistake made most often is placing the inverter at the bottom of the bezel next to the lower edge of the display. ]
It is a fact that heat rises, yet this is one of the most overlooked problems in new notebook designs.

### Result / Problem
Even though the inverters are very efficient, some energy is lost in the inverter in the form of heat.
Because of the insulating properties of the plastic materials used in the bezel construction, heat builds up and affects the display contrast.

### Solution
Designs with the inverter at the bottom can be improved in one of three ways. The inverter can be relocated away from the display, heat sinking materials can be placed between the display and the inverter, or ventilation can be provided to remove the heat.
... (Skip) ...

However, [when the inverter is placed at the bezel bottom, some designs experience a loss of contrast aggravated by the heat from the CCFT and inverter.]

### Alternatives
In cases where the inverter must be left at the bottom, and the CCFT is causing a loss of contrast, the problem can be minimized by using an aluminum foil heat sink. This does not remove the heat from the display but dissipates it over the entire display area, thus normalizing the display contrast. The aluminum foil is easy to install and in some present designs has successfully improved the display contrast.

[Remember that the objection to the contrast variation stems more from nonuniformity than from a total loss of contrast.]

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========== 以下是翻譯 & 筆記整理 ==========
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### 顯示組件的放置

可以做的事情之一是將逆變器設計到帶有主板的計算機底座中。 在某些應用中，這是不切實際的，因為這需要將高壓引線安裝在將顯示屏邊框連接到主體的鉸鏈內。 這會導致高壓引線的應變消除問題，從而影響 UL 認證。

### 設計/實驗條件
[最常犯的一個錯誤是將逆變器放在顯示器下邊緣旁邊的邊框底部。 ]
熱量升高是事實，但這是新筆記本設計中最容易被忽視的問題之一。

### 結果/問題
即使逆變器非常高效，逆變器中也會以熱量的形式損失一些能量。
由於邊框結構中使用的塑料材料的絕緣特性，熱量會積聚並影響顯示對比度。

### 解決方案
逆變器位於底部的設計可以通過以下三種方式之一進行改進： ... （跳過） ...

然而，[當逆變器放置在邊框底部時，某些設計會因 CCFT 和逆變器的熱量而加劇對比度損失。]

### 備擇方案
如果逆變器必須留在底部，並且 CCFT 導致對比度損失，則可以通過使用鋁箔散熱器將問題降至最低。 這不會消除顯示器的熱量，而是將其消散到整個顯示區域，從而使顯示對比度正常化。 鋁箔易於安裝，在一些現有設計中已成功提高顯示對比度。

[請記住，對對比度變化的反對更多地源於不均勻性，而不是完全失去對比度。]