LED工作原理中英文翻译(精)

英文原文

How Light Emitting Diodes Work

Light emitting diodes, commonly called LEDs, are real unsung heroes in the

electronics world. They do dozens of different jobs and are found in all kinds of devices.

Among other things, they form the numbers on digital clocks, transmit information from

remote controls, light up watches and tell you when your appliances are turned on.

Collected together, they can form images on a jumbo television screen or illuminate a

traffic light. Basically, LEDs are just tiny light bulbs that fit easily into an electrical

circuit. But unlike ordinary incandescent bulbs, they don't have a filament that will burn

out, and they don't get especially hot. They are illuminated solely by the movement of

electrons in a semiconductor material, and they last just as long as a standard transistor.

In this article, we'll examine the simple principles behind these ubiquitous blinkers,

illuminating some cool principles of electricity and light in the process.

What is a Diode? A diode is the simplest sort of semiconductor device. Broadly

speaking, a semiconductor is a material with a varying ability to conduct electrical

current. Most semiconductors are made of a poor conductor that has had impurities

(atoms of another material added to it. The process of adding impurities is called doping.

In the case of LEDs, the conductor material is typically aluminum-gallium-arsenide. In

pure aluminum-gallium-arsenide, all of the atoms bond perfectly to their neighbors,

leaving no free electrons (negatively-charged particles to conduct electric current. In

doped material, additional atoms change the balance, either adding free electrons or

creating holes where electrons can go. Either of these additions make the material more

conductive. A semiconductor with extra electrons is called N-type material, since it has

extra negatively-charged particles. In N-type material, free electrons move from a

negatively-charged area to a positively charged area. A semiconductor with extra holes is

called P-type material, since it effectively has extra positively-charged particles.

Electrons can jump from hole to hole, moving from a negatively-charged area to a

positively-charged area. As a result, the holes themselves appear to move from a

positively-charged area to a negatively-charged area. A diode comprises a section of N-type material bonded to a section of P-type material, with electrodes on each end. This

arrangement conducts electricity in only one direction. When no voltage is applied to the

diode, electrons from the N-type material fill holes from the P-type material along the

junction

between the layers, forming a depletion zone. In a depletion zone, the semiconductor

material is returned to its original insulating state -- all of the holes are filled, so there are

no free electrons or empty spaces for electrons, and charge can't flow. To get rid of the

depletion zone, you have to get electrons moving from the N-type area to the P-type area

and holes moving in the reverse direction. To do this, you connect the N-type side of the

diode to the negative end of a circuit and the P-type side to the positive end. The free

electrons in the N-type material are repelled by the negative electrode and drawn to the

positive electrode. The holes in the P-type material move the other way. When the

voltage difference between the electrodes is high enough, the electrons in the depletion

zone are boosted out of their holes and begin moving freely a result, the

depletion zone the negative end of the circuit is hooked up to the N-type layer and the positive end is hooked up to P-type layer, electrons and holes start

moving. If the P-type side is connected to the negative end of the circuit and the N-type

side is connected to the positive end, current will not flow. No current flows across the

junction because the holes and the electrons are each moving in the wrong direction.

When the positive end of the circuit is hooked up to the N-type layer and the negative end

is hooked up to the P-type layer, the depletion zone gets bigger. The interaction between

electrons and holes has an interesting effect -- it generates light! In the next section, we'll

find out exactly why this is.

How Can a Diode Produce Light? Light is a form of energy that can be released by

an atom. It is made up of many small particle-like packets that have energy. These

particles, called photons, are the most basic units of light. Photons are released as a result

of moving electrons. In an atom, electrons move in orbitals around the nucleus. Electrons

in different orbitals have different amounts of energy. Generally speaking, electrons with

greater energy move in orbitals farther away from the nucleus. For an electron to jump

from a lower orbital to a higher orbital, something has to boost its energy level.

Conversely, an electron releases energy when it drops from a higher orbital to a lower

one. This energy is released in the form of a photon. A greater energy drop releases a

higher-energy photon, which is characterized by a higher frequency. As we saw in the

last section, free electrons moving across a diode can fall into empty holes from the P-type layer. This involves a drop from the conduction band to a lower orbital, so the

electrons release energy in the form of photons. This happens in any diode, but you can

only see the photons when the diode is composed of certain material. The atoms in a

standard silicon diode, for example, are

arranged in such a way that the electron drops a relatively short distance. As a result,

the photon's frequency is so low that it is invisible to the human eye -- it is in the infrared

portion of the light spectrum. This isn't necessarily a bad thing, of course: Infrared LEDs

are ideal for remote controls, among other things. Visible light-emitting diodes (VLEDs,

such as the ones that light up numbers in a digital clock, are made of materials

characterized by a wider gap between the conduction band and the lower orbitals. The

size of the gap determines the frequency of the photon -- in other words, it determines the

color of the light. While all diodes release light, most don't do it very effectively. In an

ordinary diode, the semiconductor material itself ends up a lot of the light energy. LEDs

are specially constructed to release a large number of photons outward. Additionally, they

are housed in a plastic bulb that concentrates the light in a particular direction.

LEDs have several advantages over conventional incandescent lamps. For one thing,

they don't have a filament that will burn out, so they last much longer. Additionally, their

small plastic bulb makes them a lot more durable. They also fit more easily into modern

electronic circuits. But the main advantage is efficiency. In conventional incandescent

bulbs, the light-production process involves generating a lot of heat. This is completely

wasted energy, unless you're using the lamp as a heater. LEDs generate very little heat,

relatively speaking. A much higher percentage of the electrical power is going directly to

generating light, which cuts down on the electricity demands considerably. Up until

recently, LEDs were too expensive to use for most lighting applications. The price of

semiconductor devices has plummeted over the past decade, however, making LEDs a

more cost-effective lighting option for a wide range of situations. While they may be

more expensive than incandescent lights up front, their lower cost in the long run can

make them a better buy. In the future, they will play an even bigger role in the world of

technology.

TRANSIENT VOLTAGE SUPPRESSOR(TVS Diode PRESENTATION

• High protection on sensitive mobile electronic devices

• Follow strictly to the IEC 61000-4-2 ESD test standard

• Using the behavior of diode P/N junction to achieve ESD protection

What are Transient Voltages?

• These are faults which caus e the voltage to go outside normal limits for a period

of time. Transient voltages are characterized by three things:

VeryHigh Voltage, Occur For A Very Short Period of time (in nanoseconds and

High Occurrence. Many transients cause damage to micro-semiconductor chipsets by

degra ding their performance. This damage is cumulative and eventually reaches apoint

where sudden and complete failure of

the component results. Moreover, some transients are capable of causing immediate

equipment failures. Equipment failures caused by transients are hard to detect and are

often incorrectly blamed on other ‘perceived’ causes. Micro semiconductor chipsets

damaged by transients often require sophisticated instrument to replace them which make

them expensive to repair. The only cure is to clamp transients to a safe level where the

protected load can withstand.

TVS diode’s Advantages

• TVS Diode vs. Zener Diode

Compared with the traditional Zener diode, TVS diode has a larger P/N cross section.

TVS diode component is constructed and designed to absorb larger amounts of energy,

joules, with a faster response time than Zener diode. Zener diode has a higher clamping

voltage and heat dissipation is slower.

• TVS Diode vs. Multilayer Metal oxide Varistor, MLV

A major difference between TVS diode and MLV is, as MLV absorbs transient

energy, its electrical parameters such as Leakage current and Breakdown voltage tend to

drift away from their original specifications which exhibits an inherent wear out

mechanism within the structure. Because of its high impedance, its clamping ratio can

reach as high as 3. Therefore MLV is more suitable to be applied on less sensitive

lines where its high clamping voltage can be tolerated.

• TVS Diode vs. Ceramic Capacitor

Ceramic capacitor is not able to withstand a high transient voltage. A 10kV transient

voltage will destroy about 60% of the component of the ceramic capacitor while TVS

diode is able to withstand up to 15Kv transient voltage. Ceramic capacitor is also not able

to dissipate heat efficiently like what TVS diode does when transient occurs.

• TVS Diode vs. Gas Discharge Tubes, GDTs

TVS diode limits voltage spike to acceptable level by clampingwhile GDT limits

voltage spike by crowbar action. GDT conducts when its threshold voltage is exceeded

and then trigger to an on-state voltage of only a few volts. A drawback of GDT protection

is that the trigger on state voltage is below the operating voltage of the protected load.

The protected load will be shut down temporarily.

LED 是如何工作的

通常被称为LED 的发光二极管，是电子世界中真正的无名英雄。LED 的功能多达几十种，被广泛的应用于各种装置之中。在其他应用场合，LED 可以作为数字钟的数码显示、传送来自遥控装置的数据、手表的背光灯以及指示各种器械何时开启。归纳起来，LED 可以在巨大的电视荧屏上形成各种图像或者点亮交通灯。从本质上讲，LED 就是一些小灯泡，所以很适合用于电子线路中。但与普通白炽灯泡不同的是，LED 没有能烧尽的灯丝，而且使用过程中也不会变得很热。它们仅仅依靠半导体材料的电子运动来发光照明，并且其寿命和标准晶体管的一样长。在这篇文章里，我们将一起来探究一下这些普遍存在的有色眼镜后面的简单原则，对于揭示该过程中电气光学方面的潜规则具有一定的启发。

那么什么是二极管呢？二极管是最简单的一种半导体元件。一般来说，半导体是在电流传导方面特性不唯一的一种材料。多数半导体是由内含杂质（其他材料的原子）的导体制成的。添加杂质的过程被称为掺杂。在LED 中，传导材料通常选用铝—镓—砷化物（AIGaAs ）。在纯净的铝—镓—砷化物中，所有的原子和相邻原子间都非常完美地结合在一起，没有能自由运动的电子（带负电的粒子）传导电流。在掺杂过的材料中，添加的原子改变了原有的平衡，产生了自由电子或空穴。增加的这两种粒子都能增强该材料的传导性。因为电子带负电，故有多余电子的半导体被称为N 型半导体。在N 型半导体中，自由电子从负电区域移向正电区域。因为空穴带正电，故有多余空穴的半导体被称为P 型半导体。电子可以在两个空穴之间来回移动，从负电区域移向正电区域。这样，从表面上看空穴是从正电区域移向负电区域。二极管是由制作在同一硅片上的P 型半导体和N 型半导体所组成，电极在两端引出。这种制作工艺使得二极管具有单向导电性。二极管两端不加

电压是，N 区的自由电子和P 区的空穴在两层的结合处进行复合形成耗尽层。在耗尽层中，半导体材料还原为绝缘状态—所有的空穴都和电子发生复合，所以没有自由移动的电子或存有电子的空间，电荷便不再流动。要去除耗尽，就必须获得由N 区移向P 区的自由电子和向相反方向移动的空穴。要达到这个目的，可以把二极管N 区一端和P 区一端分别和电路的负极和正极相连接。N 区的自由电子被负极所排斥并推向正极。P 区的空穴沿另一路径移动。当电极之间的电位差足够大时，耗尽层的电子和空穴分离又开始自由移动。结果，耗尽层消失。如果电路的负极连到N 区，正极连到P 区，那么电子和空穴就开始移动。如果P 区一端连到电路的负极，N 区一端连到电路的正极，则电流将停止流动。因为空穴和电子都向相反的方向移动，所以没有电流穿过PN 结。当电路的正极和负极分别连接到二极管的N 区和P 区时，耗尽层加宽。有趣的是，在电子和空穴相互作用的过程中产生了光！接下来，我们将讨论一下其中的奥妙。

二极管是怎样发光的呢？光是原子释放能量的一种形式。光有许多像存有能量的包裹一样的小微粒组成。这些微粒被称为光子，是光的基本单元。光子由移动的电子所释放。在一个原子中，电子沿特定的轨迹绕原子核作圆周运动。处于不同轨道的电子所含能量有所不同。一般而言，具有较高能量的电子在离核较远的轨道中运行。如果一个电子从低轨道进入高轨

道，则一定有外界因素促使其能级发生变化。相反，电子从高轨道跃迁到低轨道时会释放能 量。这种能量是以光子的形式释放出来的。能级差越大，跃迁时释放的光子能量越高，即频 率越高。正如前面一段提及的那样，穿越二极管的自由电子能进入 P 区的空穴。这相当于 一个微粒从传送通道落入较低的轨道，所以电子以光子的形式释放能量。事实上，任何二极 管都存在这种现象，但只有特殊材料制成的二极管才能发出可见光。比如，在一个标准硅二 极管中的原子按某种方式方式排列起来，这种方式使得电子跃迁的距离相对较短。结果，光 子的频率就很低以至于人眼无法看到，这种频率的光子处于光谱中的红外线区域。当然，这

未必很糟糕：和其他元器件相比，红外 LED 是遥控装置的首选。用于数字钟的数码显示的 能发出可见光的二极管是由一种特殊材料制成，其特点是传导通道和低

轨道间的沟道较宽。 沟道的尺寸决定了光子的频率—换句话说，它决定了光的颜色。虽然所有的二极管能发光， 但大多数并非有效。对于一个普通的二极管，半导体材料自身会消耗许多光能。LED 特殊 的构造使其易于向外射放大量的光子。

再者， 它们被封装在塑胶球状物中使得光子集中到一 个特定的方向。 同传统的白炽灯相比，LED 有以下几点优势。首先，LED 内没有回烧尽的灯丝，所以 其寿命要长得多。其次，小体塑胶球形封装使 LED 更耐用。对于传统的白炽灯而言，在其 工作过程中会产生大量的热。 这完全是一种能源浪费， 除非你想用灯泡作发热器。 相对而言， LED 产生的热量非常少。大部分电功率将直接用于发光，这在很大程度上降低了电力需求。 以前，LED 的成本较高以至于无法将其广泛地用于照明。但在过去的十年里，半导体元件 的成本急剧下降，使得 LED 在许多情况之下的照明元件选择上很划算。虽然到现在为止， LED 的造价仍比白炽灯的高，但从长远来看其应用前景非常广阔。在不久的将来，LED 会 在技术领域里发挥更大的作用。 瞬态电压抑制二极管介绍 • 有效保护高感应可携式设备 • 根据及通过 IEC

国际静电测试标淮 • 应用二极管 P/N 结面的特性来达到静电保护原理 什么是瞬态电压? 瞬态电压是交流电路上电流与电压的一种瞬时态的畸变。 浪涌、 谐波为主要的表现形式。 瞬态电压最主要的特点有三个: 超高压, 瞬时态, 高频次。 超高压是指通常的瞬态电压尖峰， 高出正常电路电压幅值的 好几倍。 瞬时态是指瞬态电压持续的时间非常之短， 它可以在数亿分之一秒内完成迸发到消 失的过程。高频次是指瞬态电压的活动十分频繁，可以说无时不有、无处不在。瞬态电压是 会对微电子半导体芯片造成损坏的。虽然有些微电子半导体芯片受到瞬态电压侵袭后,它的 性能没有明显的下降， 但是多次累积的侵袭会给芯片器件造成内伤而形成隐患。 瞬态电压对 芯片器件造成的损伤难以与其它原因造成的损伤加以区别, 从而不自觉地掩盖了失效的真

正原因。由于微电子半导体芯片的精、细、结构, 如要替换或修理需要使用高度精密仪器, 是非常费财的。为一的有效方法就是把瞬态电压抑制在被保护元件能承受的安全水平。 瞬态电压抑制二极管的优势 • 瞬态电压抑制二极管与齐纳二极管 与传统的齐纳二极管相较,瞬态电压抑制二极管的P/N结面积更大。这一结构上的改进 使瞬态电压抑制二极管具更强的高压承受力和更快的效率。 相较之下齐纳

二极管也有较高的 抑制电压和较慢的散热速度。 • 瞬态电压抑制二极管与多层金属氧化物突波吸收器 瞬态电压抑制二极管与多层金属氧化物突波吸收器最大的不同是多层金属氧化物突波 吸收器的功能会在瞬态电压的冲击下衰退。当瞬态电压侵袭时,多层金属氧化物突波吸收器 的相关参数如漏电电流值和中止电压值都会偏离原来的参数而变得不准确。 还有多层金属氧 化物突波吸收器有较高的阻抗所以它的抑制电压可达最初中止电压的3倍,这种特性只適合 用于对电压不太感应的线路和元件的保护。 • 瞬态电压抑制二极管与陶瓷电容器 陶瓷电容器这类元件对高压的承受力比较弱。如有10kV的瞬态电压冲击时,会对陶瓷电 容器造成约60%的损坏,而瞬态电压抑制二极管能承受到15kV的瞬态电压。在瞬态电压侵袭 时所产生的热量,陶瓷电容器也没有办法象瞬态电压抑制二极管那样很有效的把它散去。 •

瞬态电压抑制二极管与离子气体放电管 瞬态电压抑制二极管是以抑制电压的方式来达到瞬态电压保护,而离子气体放电管是以 铁橇动作的方式来达到瞬态电压保护。 离子气体放电管的缺点是在启动后保持在非常低的电 压壮态,电压低于负载的正常工作电压。在这种情形下,负载没有办法绩续工作,会暂时的关 闭。