2022年自动化专业毕业外文翻译 .pdf

外文翻译原文：NC switching power supply design ForwardEvery new electronic product, except those that are battery powered, requires converting off line 115 Vac or 230 Vac power to some dc voltage for powering the electronics. The availability of design and application information and highly integrated semiconductor control ICs for switching power supplies allows the designer to complete this portion of the system design quickly and easily. Whether you are an experienced power supply designer, designing your first switching power supply or responsible for a make or buy decision for power supplies, the variety of informational the SWITCHMODE Power Supplies Reference Manual and Design Guide should prove useful. ON Semiconductor has been a key supplier of semiconductor products for switching power supplies since we introduced bipolar power transistors and rectifiers designed specifically for switching power supplies in the mid 70. We identified these Semiconductor components can rightfully be called a SWITCHMODE power supply or SMPS. This brochure contains useful background information on switching power supplies for those who want to have more meaningful discussions and are not necessarily experts on power supplies. It also provides real SMPS examples, and identifies several application notes and additional design resources available from ON Semiconductor, as well as helpful books available from various publishers and useful web sites for those who are experts and want to increase their expertise. Introduction: Efficient conversion of electrical power is becoming a primary concern to companies and to society as a whole. Switching power supplies offer not only higher efficiencies but also offer greater flexibility to the designer. Recent advances in semiconductor, magnetic and passive technologies make the switching power supply an ever more popular choice in the power conversion arena today. 名师资料总结 - - -精品资料欢迎下载 - - - - - - - - - - - - - - - - - - 名师精心整理 - - - - - - - 第 1 页，共 7 页 - - - - - - - - - This Guide is designed to give the prospective designer an overview of all the issues involved in designing switch mode power supplies. It describes the basic operation of the more popular topologies of switching power supplies, their relevant parameters, provides circuit design tips, and information on how to select the most appropriate semiconductor and passive components. This Guide lists the ON Semiconductor components expressly built for use in switching power supplies. Basic ConvertersThe most elementary forward-mode converter is the Buck or Step-down Converter. Its operation can be seen as having two distinct time periods which occur when the series power switch is on and off. When the power switch is on, the input voltage is connected to the input of the inductor. The output of the inductor is the output voltage, and the rectifier is back-biased. During this period, since there is a constant voltage source connected across the inductor, the inductor current begins to linearly ramp upward During the “on” period, energy is being stored within the core material of the inductor in the form of flux. There is sufficient energy stored to carry the requirements of the load during the next off period. The next period is the “off ” period of the power switch. When the power switch turns off, the input voltage of the inductor flies below ground and is clamped at one diode drop below ground by the catch diode. Current now begins to flow through the catch diode thus maintaining the load current loop. This removes the stored energy from the inductor. This period ends when the power switch is once again turned on. Regulation is accomplished by varying the on-to-off duty cycle of the power switch. The buck converter is capable of kilowatts of output power, but suffers from one serious shortcoming which would occur if the power switch were to fail short-circuited, the input power source is connected directly to the load circuitry with usually produces catastrophic results. To avoid this situation, a crowbar is placed across the output. A crowbar is a latching SCR which is fired when the output is sensed as entering an overvoltage condition. The buck converter should only be used for board-level regulation. The most elementary fly back-mode converter is the Boost or Step-up Converter. Its schematic can be seen in Figure 2. Its operation can also be broken into two distinct periods where the power switch is on and off. When the power switch turns 名师资料总结 - - -精品资料欢迎下载 - - - - - - - - - - - - - - - - - - 名师精心整理 - - - - - - - 第 2 页，共 7 页 - - - - - - - - - on, the input voltage source is placed directly across the inductor. This causes the current to begin linearly ramping upwards from zero 。Once again, energy is being stored within the core material. The amount of energy stored during each cycle times the frequency of operation must be higher than the power demands of the load 。The power switch then turns off and the inductor voltage fly back above the input voltage and is clamped by the rectifier at the output voltage. The current then begins to linearly ramp downward until the energy within the core is completely depleted. Its waveform 。The boost converter should also be only used for board-level regulation. Common Topologies A topology is the arrangement of the power devices and their magnetic elements. Each topology has its own merits within certain applications. Some of the factors which determine the suitability of a particular topology to a certain application are: 1) Is the topology electrically isolated from the input to the output or not. 2) How much of the input voltage is placed across the inductor or transformer. 3) What is the peak current flowing through the power semiconductors. 4) Are multiple outputs required? 5) How much voltage appears across the power semiconductors? The first choice that faces the designer is whether to have input to output transformer isolation. Non-isolated switching power supplies are typically used for board-level regulation where a dielectric barrier is provided elsewhere within the system. Non-isolated topologies should also be used where the possibility of a failure does not connect the input power source to the fragile load circuitry. Transformer isolation should be used in all other situations. Associated with that is the need for multiple output voltages. Transformers provide an easy method for adding additional output voltages to the switching power supply. The companies building their own power systems are leaning toward transformer isolation in as many power supplies as possible since it prevents a domino effect during failure conditions. Power Factor CorrectionThe present day power supplies use a capacitive input filter when powered from the AC power line. A resulting shortcoming is that the AC line is rectified which results in high peak currents at the crests of the AC voltage .These peak currents are typically three to five times higher than the average current drawn by the power 名师资料总结 - - -精品资料欢迎下载 - - - - - - - - - - - - - - - - - - 名师精心整理 - - - - - - - 第 3 页，共 7 页 - - - - - - - - - supply. This causes excessive voltage drop in the wiring and imbalance problems in the three phase delivery system. Also the full energy potential of the AC line is not utilized. The task is to increase the conduction angle of the AC rectifiers and to make the resulting current waveform look as sinusoidal and in phase with the voltage waveform as possible. In this way, the power drawn by the power supply from the line is maximized for real power as shown in Figure 14. A popular method of accomplishing this is by using a boost converter prior to the actual power supply. Boost-mode supplies exhibit the largest input dynamic range of all the switching power supply topologies. Input voltages down to 30 volts can be boosted to 370 volts on its output (higher than the highest expected peak operating AC crest voltage). The bulk input filter capacitor is now placed on the output of the boost converter. The input capacitor, just following the 50/60 Hz Rectifier Bridge is now less than 1 uF. 名师资料总结 - - -精品资料欢迎下载 - - - - - - - - - - - - - - - - - - 名师精心整理 - - - - - - - 第 4 页，共 7 页 - - - - - - - - - 译文：开关电源设计前言每一个新的电子产品，除那些有电池供电， 一些直流电压为电源的电子产品，都需要将电压转换成115 V 转接或 230 V。可得到的设计和应用的信息及高度集成的半导体开关电源供应控制芯片使得设计师来完成这一部分的系统设计更加迅速和容易。 无论你是一位经验丰富的电力供应设计师，设计你的第一个开关电源供应或负责一个或做出购买决定，各种各样的信息， 开关电源供应器参考手册和设计指南都是有益的。在 70 年代中期，自从我们介绍了双极功率晶体管和整流器专为交换式电源供应器，半导体已成为主要供应商为交换式电源供应器的半导体产品。我们定义这些东西作为开关模式的产品。一个在设计上使用半导体元件的开关电源，以理所当然地被称为开关电源或者 SMPS 。对于那些想要在开关电源方面做更多有意义的讨论而且不是专家的人来说，这本小册子提供了很多关于开关电源的有用的背景资料。它也提供了一个真实的SMPS 例子，并确定了几个来自半导体的应用笔记和额外的设计资源，对于那些专家和想要增加他们的专业知识的人，也可以从不同的出版商和有用的网站获得有用的书籍。介绍作为一个整体的企业和社会对把电力的高效转化作为首要关注。对设计者来说，开关式电源不仅提供更高的效率，而且提供更大的灵活性。 在今天的电源转换舞台上， 在半导体， 磁场学和动力技术的最新进展，使开关电源比以往任何时候都更受欢迎。 本指南旨在向设计师提供一个设计开关电源的基本方法。它描述了开关电源技术中一些很受欢迎的基本操作。他们的相关参数， 提供电路设计的窍门以及一些关于怎样选择最合适的半导体和元器件。本指南中列出了对半导体元件明确建成使用在交换式电源供应器。基本转换器最基本的前向模式变换器是BUCK 变换器或叫 STEP-DOWN变换器。当各种电源开关在关断或是导通时， 其运作可以被看作是有两个截然不同的时段。当电源开关闭合时， 输入电压被连接在输入电感上。电感的输出就是输出名师资料总结 - - -精品资料欢迎下载 - - - - - - - - - - - - - - - - - - 名师精心整理 - - - - - - - 第 5 页，共 7 页 - - - - - - - - - 电压，而且整流器是可返回的。 在这个阶段， 因为有一个不变的电压源接在电感上，电感电流开始线性的上升。在这个“开”的阶段里面， 能量以磁场的形式储存在电感器件的核心部分里面。这里储存了下一个断开阶段供给负载的足够的能量。电源开关的下一个阶段是“关”。当电源开关断开时，电感的输入电压降到0V一下，且是在一个很短时间里下降到0V一下。电流开始通过二极管降低，以保持电流的连续。 这样移走了电感中储存的能量。当开关再次合上时， 这个阶段就结束了。改变电源开关的占空比就完成了电源的调节。BUCK 变换器的输出容量可达数千瓦，但是如果电源开关在短时间内动作，可能会带来很大的麻烦， 因为输入电源与可能造成灾难性后果的负载线路直接相连。为了避免这种情况的发生，通常在输出端接上保护装置（CROWBAR），这个保护装置可以在系统进入过电压条件下自动动作。BUCK 变换器应该只使用在大范围调节中。反激式或升压模式转换基础最基本的反激式变换器是BOOST 变换器或 STEP-UP 变换器。它的工作过程也可以分成两个不同的阶段，即电源开关处于 “开”或 “关”。当电源开关处于开状态时， 输入电压源直接被接在电感器两端。这导致电流开始线性的从零开始上升。可由下式给出。同样能量被储存在电感线圈中。在每一个周期中所储存的能量都要比负载所需的能量多。当电源开关关断是， 电感电压反馈上述输入电压同时被整流器整流成输出电压最后输出。电流开始线性下降，直到电感线圈中的能量不足。BOOST 变换器也应该仅仅被用于大范围调节中。通用拓扑这里所谓的拓扑结构就是电源设备及其磁性元件的布局。在实际应用中， 每一种拓扑结构都有其最近的特点。在实际应用中， 有如下因素决定如何选择一种比较合适的特定的拓扑结构：1）输入与输出在电力上的拓扑结构是不是独立的。2）有多大的输入电压加在电感或是变压器上。3）什么是峰值电流流过功率半导体。4）是否需要多路输出。5）多大的电压加在功率半导体两端。第一种选择将使得设计者决定是否要在输入和输出之间置一个独立的变压器。非独立开关电源的典型应用之一是，将其用于大范围调节系统中， 在这种系名师资料总结 - - -精品资料欢迎下载 - - - - - - - - - - - - - - - - - - 名师精心整理 - - - - - - - 第 6 页，共 7 页 - - - - - - - - - 统中到处设置了绝缘层。 非独立拓扑结构应该被用于电源的异常不至于将输入电源与脆弱的负载电路联系起来。 在其它所有情况下都应该使用独立的变压器。在多输出电压的系统中更是如此。 变压器为开关电源设备提供了一种非常容易增加附加输出电压的方法。 企业在构建他们的电力系统时， 总是尽可能的设置和他们的电源共给一样多的独立的变压器， 因为这样可以在异常情况下起到很好的保护作用。功率因数校正目前，来自交流电力系统的电压共给设备都在输入端使用了一个滤波电容。这样造成的直接后果就是， 被整流的交流通路上造成了在电压峰值出现很高的峰值电流。这峰值电流普遍是正常供电系统平均电流的3-5 倍。这样在三相系统中造成了在绕组处额外的电势降和出现不平衡问题。这也造成了交流通路上潜在的电能没有被利用。功率校正的任务就是增加交流整流的整流角，使得整流出来的电流波形看起来尽可能与正弦波一致， 而电流波形相位尽可能与电压波形相位一致。这样，使得来自交流端的功率与实际功率最大程度相等。实现功率因数校正比较常用的方法， 是使用一个 BOOST 变换器改善实际电源。BOOST 模式的变换器提供了所有开关电源拓扑结构中最大的动态输入范围。输入30V经过 BOOST 变换器变换后输出电压可以升至370V （这个电压比最高期望的交流峰值电压更高）。 BULK 输入端滤波电容接在BOOST 变换器的输出端。并连在50/60HZ整流桥两端的输入电容应该小于1uF。名师资料总结 - - -精品资料欢迎下载 - - - - - - - - - - - - - - - - - - 名师精心整理 - - - - - - - 第 7 页，共 7 页 - - - - - - - - -