电子类专业英语电子教案第二.ppt

学习重点： （1）掌握有关电源的基本单词、词组和缩略语的基本含义及用法 （2）培养阅读翻译有关电源科技文献和产品说明书的能力 （3）学习科技英语中的名词化结构，掌握由动词、形容词、过去分词、动名词等派生或转化来的抽象名词,2 Power Supplies,生词 bypass bai.p:s n. 支路，道 coil kil n. 卷，线圈 discharge dist:d v. & n. 放电,Passage A Basics of Power Supply,filter filt n. 滤波器，过滤器 v. 过滤 heatsink hi:t sik n. 散热器 magnetic mgnetik a. 磁的 mains mein n. 电网 outlet autlet n. 电源插座 passive psiv a. 被动的, 消极的；无源的 pulsating plstia. 脉动的 rated reitid a. 标称的 ripple ripl n. 纹波 sample smpln. 样品；标本v. 抽取样品,smooth smu: a. 平稳的，流畅的 v. 使.光滑，滤波 transformer trnsf:m(r), tr:- n. 变压器 bridge rectifier 桥式整流器 magnetic field .磁场 overheating 过热 Pulse Width Modulated (PWM) Regulator 脉冲宽调制调节器 Pulse Rate Modulated (PRM) Regulator 脉冲速率调节器 RMS (=Root-Mean-Square) 均方根,2. 课文翻译讲解,When working with electronics, you always need power supply, a device that transfers electric power from a source to a load using electronic circuits.,现在分词短语，作时间状语,同位语，进一步说明power supply,翻译：当你工作中用到电子学时 ，你就需要电源装置。电源是一 用电路把电能从电源输送给负载 的设备。,A typical application of power supplies is to convert utilitys AC input power into regulated DC voltage(s) required for electronic equipment. Depending on the mode of operation of power semiconductors power supply can be linear or switching.,Application是动词转化 过来的名词,不定式短语作表语,过去分词短语，修饰DC voltage(s）,翻译：电源的主要用途是将有效的 交流输入功率转换为电子设备所需 的直流电压。根据电源功率半导体 器件的工作方式电源装置可以是线 性或开关式的。,Linear voltage power supplies are commonly used for both step-up (output supply voltage is greater than input source voltage) and step-down (output supply voltage is lower than input source voltage) applications. Linear power supplies are also available with either a fixed output voltage or a variable output voltage when using external biasing.,翻译：线性稳压器常用于电压的提升（输出供电电压大于输入源电压） 和降低（输出供电电压低于输入源电压）。使用外部偏置，线性稳压 器也可产生恒定输出电压或可变输出电压。,The basic block of a linear power supply is shown in Figure 2-1, which includes: Transformer, which steps down high voltage AC mains to low voltage AC; Rectifier, which converts AC to DC, but the DC output is varying; Filtering, which filters the DC from varying greatly to a small ripple; Regulator, which eliminates ripple by setting DC output to a fixed voltage.,翻译：线性电源可以分解为一系列基本模块，如图2-1所示，该图包括：变 压器把电网高压交流电转换为低压交流电；整流器把交流电转换为 直流电，但是直流输出是变化的；滤波器从直流电流中滤掉变化较大的 成分使之仅有小的纹波成分；稳压器消除纹波，输出固定值的直流电压 。,Transformer converts the voltage from the wall outlet (mains) to a different, usually a lower voltage. The input coil is called the primary and the output coil is called the secondary. There is no electrical connection between the two coils; instead they are linked by an alternating magnetic field created in the soft-iron core of the transformer.,翻译：当一个小的电压V正向加到二极管时， 就会有一个小的电流流过，并产生一个大约 为0.6V到1V的电压降Von，这常被认为是二 极管的“正向电压降”，若为硅二极管， 大约为0.7V。,alternating magnetic field为动名词短语,A bridge rectifier circuit is employed to produce DC output and can be made by four individual diodes or a single chip, on which an array of four diodes is integrated, for full wave rectification, and also can be made by a single diode yielding a half wave (pulsating) output. 1.4V is used up in the bridge rectifier because each diode uses 0.7V when conducting and there are always two diodes conducting.,翻译：桥式整流器线路用 于产生直流输出，它可以 由四个单个的二极管或集 成有四个二极管的单个芯 片构成以用于全波整流， 也可用产生半波（脉冲） 输出的一个二极管构成。 1.4伏电压被消耗在桥式 整流器中，因为在导通时 每个二极管用掉0.7伏， 而在在桥式整流器中总是 有两个二极管同时导 通。,rectification是由动词 转化来的抽象名词 ， pulsating 和 conducting 为动词转化来的动名词,Bridge rectifiers are rated by the passed maximum current and the maximum reverse voltage they can withstand (this must be at least three times the supply RMS voltage so the rectifier can withstand the peak voltages).,翻译：桥式整流器是由它能通过的最大电流值和所能承受的最大反向电压 （这一电压值至少是均方根电压的三倍，这样整流器才能承受住峰值电压 ）来标称的。,A filter, consisted of capacitors or resistors or inducers or their combinations, is used to filter part of the pulses giving a smoothed DC voltage. However, filtering is not perfect and small pulses, known as ripple, are still remained. For many circuits a ripple, which is 10% of the supply voltage, is satisfactory.,翻译：由电容器，或电阻 器，或电感器，或它们的组 合而构成的滤波器可过滤部 分脉冲而得到平滑的直流电 压。然而，滤波器不是完美 的，仍然存在小脉冲，常称 之为纹波电压。对于许多电 路来说，纹波电压大小为电 源电压的10是合适的。,combination是由动词转化来 的抽象名词 ， filtering为动词 转化来的动名词,A simple voltage regulator for low current power supplies can be made up of a resistor and a Zener diode connected in reverse. But nowadays, many types of voltage regulator ICs can be available with fixed (typically 5, 12 and 15V) or variable output voltages, largely simplifying the regulator designs. Most regulators include some automatic protection from excessive current (overload protection) and overheating (thermal protection).,翻译：用于低电流电源，稳压器可以简单地由一个电阻和一个反向连接的齐 纳二极管构成。但是目前，许多类型的集成稳压器的输出可以为固定值（通 常为5伏，12伏和15伏）或可变值，大大简化了设计过程。大部分稳压器都 具有一些过电流(过载保护)和过热（热保护）自动保护功能。,Many of the fixed voltage regulator ICs has 3 leads and look like power transistors, such as the 7805 +5V 1A regulator. They include a hole for attaching a heatsink if necessary.,The advantage of linear regulators is simple implementation and minimal parts (just the IC in the case of fixed output) and low output ripple. The major disadvantage of linear regulators is low efficiency.,翻译：许多固定输出的集 成稳压器有3根引线，看 起来像功率晶体管，例如 7805+5V 1A稳压器。它 们包含一个孔，如果必要 的话，在此孔上可以附加 一个散热片。,翻译：线性稳压器的优点 是实现简单、部件体积小 （就固定输出而言恰好是 集成电路）和输出纹波低。 线性稳压器的主要缺点是 效率低。,Switch mode power supply are continuously switching on and off with high frequency from 20 kHz to several MHz to provide the transfer of electric power via energy storage components (inductors and capacitors).,翻译：开关式电源装置连续不断地以20千赫至几兆赫的高频率进行开关操作 ，通过储能元件（电感器和电容器）提供电能的转换。,A basic switch mode power supply is consisted of a rectifier, a switching transistor, a step up/down transformer, and a switching controller-Pulse Width Modulated (PWM) Regulator or Pulse Rate Modulated (PRM) Regulator, a high speed switching diode, and a capacitor, as shown in Figure 2-2, in which the heart is the switching transistor and switching transformer.,翻译：一套基本的开关 式电源由一个整流器、 一个开关晶体管、一个 升压/降压变压器、一个 开关控制-脉冲宽度调制 （PWM）调节器或脉冲 速率调制（PRM）调节 器、一个高速开关二极 管和一个电容器组成。 如图2 -2所示，其中核 心器件是开关晶体管和 开关变压器。,Figure 2-2 a basic schematic of a switch mode power supply,By controlling the amount of “on time” and “off time” of the switches, the amount of power delivered to the transformers load can be controlled. PWM regulators vary the “on” or conduction time of the switching transistor, while the PRM regulator varies the modulation rate (frequency) at which the switching transistor is turned off and on, and these regulations are achieved by sampling the DC output voltage and comparing it to a reference voltage.,翻译：控制开关的打开时 间和关闭时间的总数，可 以控制传递到变压器负载 上的电量。PWM改变开关 晶体管打开或导通的时间， 而PRM改变调制速率，此 调制速率是开关晶体管关 闭和开启的速率（频率）， 这些调节是把采样到的直 流输出电压和参考电压相 比而达到 的 。,cntrolling sampling comparing 均为动名词短语 动名词虽起名词的作用，但仍具 有动词的若干特点，可以 有宾语和状语,As the transistor is switched on and off the magnetic field alternately expands and collapses in the transformer windings. By designing the transformer with different secondary turns ratios, various amplitude pulses are produced at the output of each secondary winding. The output of each winding is applied to high speed switching diodes and filters (capacitors or inducers) which produce the DC output voltages of the switch mode power supply.,翻译：随着晶体管的打开和关闭，变压器绕组中的磁场交替增强和减弱。用设计 具有不同的次级匝数比的变压器，就会在每个次级绕组的输出端产生不同的幅度 脉冲。每个绕组的输出端连接到高速开关二极管和滤波器（电容器或电感器）上 ，以产生出开关式电源的直流输出电压。,A switch mode power supply offers three main advantages over a conventional linear power supply: 1) high efficiency & less heat generation 2) tighter regulation 3) smaller size and weight.,The disadvantage of switching regulators is complexity, as several external passive components are required on board. Output voltage ripple is another disadvantage, which is generally handled with bypass capacitance near the supply and at the load.,翻译： 图2-2 开关式电源装 置的基本原理图与传统的线 性电源相比，开关电源有三 个主要优点： 1）高效低热 2）更为严密的调节 3）尺寸小、重量轻,翻译：复杂性是此开 关稳压器的一个缺点 ，因为板上需要几个 外部附加元件。另一 个缺陷是输出电压有 纹波，它一般是用电 源和负载附近的旁路 电容来处理的。,3.疑难解析,1). A simple voltage regulator for low current power supplies can be made up of a resistor and a Zener dio