标签: diode

二极管（Diode）具有单向导电性，即只允许电流沿着一个方向流动，而阻挡反向电流流动。二极管是电子电路中最基本的元件之一，广泛应用于各种电子设备中。 单向导通性的实验说明： 当输入电源电压Vi比稳压二极管的稳定电压VZ低时，稳压二极管没有击穿而处于反向截止区，此时电路回路中只有比较小的反向漏电电流IR（reverse leakage current），这种工作状态不是稳压二极管的正常工作状态，因为输出电压Vo是随输入电压Vi变化的，没有达到输出稳定电压的目的，如下图所示： 当输入电源电压 Vi 比稳压二极管稳定电压 ZT 高时，稳压二极管被反向电压击穿，此时回路电流急剧增加，如下图所示： 一、二极管的功能 二极管的主要功能是将交流电转换为直流电，也可作为整流器、限流器、稳压器等电路中的关键元件。另外，二极管还可用于振荡电路、开关电路、放大电路等电路中，起到重要的作用。 二、二极管的作用 整流：二极管可以将交流电转换为直流电，实现整流功能。当正向电压施加在二极管上时，电流可以自由通过，而当反向电压施加在二极管上时，二极管则处于截止状态，阻止电流通过。 实现单向导通的示意图 原理就是两个管子分别导通 首先，是正半周期D2,D3工作 然后，是负半周期D1,D4工作 保护：二极管可用于保护电路免受电压峰值和电磁干扰等影响。在电路中加入二极管后，可以有效地限制电压，保护电路不受损坏。 稳压：二极管还可以作为稳压器使用，它可以在电路中提供一个固定的电压，使电路的工作更加稳定。 稳压二极管的典型应用电路如下图所示： 三、二极管的实际案例解说 整流器：二极管被广泛应用于整流电路中，如桥式整流电路、半波整流电路和全波整流电路等。 稳压器：二极管稳压器是一种常见的稳压电路，它可以提供一个恒定的电压输出。 光电二极管：光电二极管是一种具有光电转换功能的二极管，可以将光能转换为电能，广泛应用于光电传感器、光电开关、光电显示等领域。 对单颗LED 的驱动 图 1：灌电流方式驱动LED 此电路通过单片机I/O 口直接驱动LED。当I/O 口输出高电平时，LED 两端等电位，无电流，LED 熄灭；当I/O 口输出低电平时，电流从电源经R1、LED1、I/O 口流进单片机，LED 亮。LED 的亮度与流经它的电流大小成正比，而电流大小由R1 阻值决定。此驱动方式可称为灌电流驱动。 图 2 ：拉电流方式驱动 LED 此电路通过单片机 I/O 口直接驱动 LED 。当 I/O 口 输出低 电平时， LED 两端等电位，无电流， LED 熄灭；当 I/O 口输出高电平时，电流从单片机 I/O 经 R2 、 LED2 流到地， LED 亮。 LED 的亮度与流经它的电流大小成正比，而电流大小由 R2 阻值决定。此驱动方式可称为拉电流驱动。 Zener二极管：Zener二极管是一种具有特殊稳压特性的二极管，可以在一定范围内稳定地维持电压输出，广泛应用于电源稳压器、电路保护器等领域。 总之，二极管在电子领域中应用非常广泛，不同类型的二极管在不同的电路中都有不同的作用和功能。

From the beginning of my career in electrical engineering, I have noticed that engineers have a penchant for naming things. Names like Hewlett-Packard, Wang, and Rand Corp. have obvious etymologies, but others can be somewhat obscure or subject to cultural sensitivities. Obscure names for companies like Accenture, Ampire, and n*Ask, seem to be on the rise. So what is an “accenture” -- an accent, a venture?   Other names that are now ubiquitous in the public landscape may have turned out differently in an earlier generation: Microsoft might have been a lingerie company; Yahoo and Google could have been “girly” magazines; and FireFox would likely have been banned by PETA.   Strangely enough, Compaq Computer actually made computers that were compact; Bell Labs did research related to things with bells (telephones); International Business Machines (IBM) internationally sold business machines; and Advanced Micro Devices (AMD) made advanced micro devices. One could make the case that company names are driven more by marketing types than by engineers, so let’s explore names that arise within the field of hardware design.   Thirty years ago, I was developing a high-speed image memory plane. In order to “pipeline” writes to the memory and prevent flicker on the display, there were two banks in the memory plane. When one was being displayed, the other was being written to. When writes were complete, the display was “ping-ponged” to the other bank. The signal that gave the status that this transition was about to occur was aptly named PPP (ping-pong pending). One of my early successes as a hardware design engineer was selling that name to the lead engineer.   Later, I worked on a team that developed interface boards that adhered to the VME Bus standard. Every read and write cycle was completed by asserting the DTACK (DaTa ACKnowledge) signal. The timing was a “pain in the rear,” hence the name “DTACK” would have been memorable (if you get my “point”).   Another issue that we had with the VME bus standard was that, although there was a priority scheme that VME bus masters used to adjudicate priority, there was no way to tell exactly when a bus master would relinquish the bus after a higher-priority bus master requested priority.   Given the nature of our system, my old boss, Bob Buxton, thought it wise to implement all bus masters in a manner that would limit how many transfers they could do in one bus priority request interval. He chose 32 transfers (128 bytes) for the size of these “Buxton Blocks,” as we soon nicknamed them. Fifteen years later, I was debugging some built-in test equipment (BITE) code and ran across the term “Buxton Blocks” in the comments… definitely gave me a chuckle after all those years.   I think every hardware designer has had the experience of overdriving a zener diode, thereby creating a NED (noise emitting diode). When I was at Georgia Tech, someone in the switching lab used a capacitor with too low a voltage rating in his power supply. The loud “POP!” gave us the impression that he had created a very efficient signal-to-noise converter.   Think back over your own career and see what funny names you recall using in your own designs. Who says engineers don’t have a sense of humor?   Dwight Bues is a Georgia Tech Computer Engineer with 30 years' experience in computer hardware, software, and systems and interface design.

Engineering is central to my relationship with my wife. That's becuase I am continually fixing everything, a trait that won her over on only our second date. It is engineering that makes the world and our relationship go round. More specifically, it's my real-world application of the problem-solving process. In 2005 as 19-year-old college sophomores at the University of California, Irvine, my wife and I went on our second date to a party at my wife's friend's flat. A typical location for a party—a poorly decorated, sparsely furnished, sad excuse for domicile, but nevertheless, a place of freedom for kids our age. Since we had gone early to help setup, I being a college guy sat down on the couch to watch TV because I didn't cook and was therefore useless. That is, until I saw a strand of Hawaiian lights hanging in the window. Being a lover of electricity (yep, I'm an electrical engineer), I immediately noticed that the strand was burnt out. It was a typical condition for a single strand of twinkle lights poorly maintained by college-aged youth. I asked for replacement lights and guess what, there weren't any. (When have there ever been replacement bulbs when you really needed them?) Without time to take a quick trip to Ace, Home Depot, or even CVS, me having a never-quit, stubborn attitude (another trait that helped win my wife over—cue eye-rolling), I asked if they had any tools. Another "No" along with an eyebrow furrow. Sure they're college girls, but who knows, maybe a handyman parent left a tool-box with a wire stripper and some electrical tape. That answer still didn't stop me, so I asked for any scissors and tape and received just what I expected—a roll of Scotch tape, a pair of pink schoolgirl Fiskar scissors, and a sarcastic "good luck" (the sarcasm coming from my wife's friend). I'm not sure if it was the stubborn guy in me or the guy trying to impress the girl, but I knowingly went against any vague recollection of electrical or UL safety codes: I cut right into the strand of lights (yes, I unplugged it first) to bypass the one light whose semi-transparent brownish tint around the base of the bulb disallowed full transmittance of the backlight I held the bulb up to. Once the wires were stripped and twirled together, I was surprised at how well the Scotch tape actually held everything together, and I did try to put a big glob of tape on there to minimise any shockage. At the moment of truth, no fireworks, no blown fuses, just a beautifully lit strand of Hawaiian Christmas lights and a cool, demure "need anything else?" I was pleasantly satisfied by the looks of surprised amazement when the girls glanced up to a glistening decoration successfully resurrected from the dead. Triumph. Whether it's soldering a faulty diode into the back of a supposedly broken TV, swapping car window motors so it's not an icebox driving down the freeway, or problem-solving a disappointment, my engineering training and passion for the solution keeps it all going in the right direction. Eight years later and the journey continues. Chris Higgins is the CEO of SparqEE, the start-up that brought you the SparqEE CELLv1.0 on Kickstarter. He is a computer and electrical engineer who loves innovating across hardware, software, systems, networking—anything that advances technology in the world. He submitted this article as part of Frankenstein's Fix, a design contest hosted by EE Times (US).

My relationship with my wife is centred on engineering. That's becuase I am continually fixing everything, a trait that won her over on only our second date. It is engineering that makes the world and our relationship go round. More specifically, it's my real-world application of the problem-solving process. In 2005 as 19-year-old college sophomores at the University of California, Irvine, my wife and I went on our second date to a party at my wife's friend's flat. A typical location for a party—a poorly decorated, sparsely furnished, sad excuse for domicile, but nevertheless, a place of freedom for kids our age. Since we had gone early to help setup, I being a college guy sat down on the couch to watch TV because I didn't cook and was therefore useless. That is, until I saw a strand of Hawaiian lights hanging in the window. Being a lover of electricity (yep, I'm an electrical engineer), I immediately noticed that the strand was burnt out. It was a typical condition for a single strand of twinkle lights poorly maintained by college-aged youth. I asked for replacement lights and guess what, there weren't any. (When have there ever been replacement bulbs when you really needed them?) Without time to take a quick trip to Ace, Home Depot, or even CVS, me having a never-quit, stubborn attitude (another trait that helped win my wife over—cue eye-rolling), I asked if they had any tools. Another "No" along with an eyebrow furrow. Sure they're college girls, but who knows, maybe a handyman parent left a tool-box with a wire stripper and some electrical tape. That answer still didn't stop me, so I asked for any scissors and tape and received just what I expected—a roll of Scotch tape, a pair of pink schoolgirl Fiskar scissors, and a sarcastic "good luck" (the sarcasm coming from my wife's friend). I'm not sure if it was the stubborn guy in me or the guy trying to impress the girl, but I knowingly went against any vague recollection of electrical or UL safety codes: I cut right into the strand of lights (yes, I unplugged it first) to bypass the one light whose semi-transparent brownish tint around the base of the bulb disallowed full transmittance of the backlight I held the bulb up to. Once the wires were stripped and twirled together, I was surprised at how well the Scotch tape actually held everything together, and I did try to put a big glob of tape on there to minimise any shockage. At the moment of truth, no fireworks, no blown fuses, just a beautifully lit strand of Hawaiian Christmas lights and a cool, demure "need anything else?" I was pleasantly satisfied by the looks of surprised amazement when the girls glanced up to a glistening decoration successfully resurrected from the dead. Triumph. Whether it's soldering a faulty diode into the back of a supposedly broken TV, swapping car window motors so it's not an icebox driving down the freeway, or problem-solving a disappointment, my engineering training and passion for the solution keeps it all going in the right direction. Eight years later and the journey continues. Chris Higgins is the CEO of SparqEE, the start-up that brought you the SparqEE CELLv1.0 on Kickstarter. He is a computer and electrical engineer who loves innovating across hardware, software, systems, networking—anything that advances technology in the world. He submitted this article as part of Frankenstein's Fix, a design contest hosted by EE Times (US).