外文资料翻译.doc

南京理工大学泰州科技学院毕业设计(论文)外文资料翻译学院 (系)： 专 业： 姓 名： 学 号： (用外文写)外文出处：Switching Power Supply Design , Third Edition. McGraw-Hill. 附 件： 1.外文资料翻译译文；2.外文原文。 指导教师评语：本文译者就开关模式中功率半导体的应用一文进行了翻译。从译文看，文章翻译语句通顺，语言表达清楚，较好反映原文内容，符合本次毕业设计外文翻译要求。 签名： 年 月 日注：请将该封面与附件装订成册。附件1：外文资料翻译译文开关模式中功率半导体的应用电能通常不会用在其生产或分布的形式。几乎所有的电子系统需要某种形式的能量转换。通过电路把电能从一个特定源转移到一个特定负载所用的设备称作为电源。电源装置(PSU)的典型应用是将交流电转换成电子设备所需直流电。如今在电源装置，能量流通过不间断高频半导体开关来控制。这种装置被称为开关电源。与线性电源相比，他们能提供更大的效率，因为开关可以低损耗地控制能量：当开关关闭时，它会阻止电压和电流的流动，在两种状态中均比较低。同时，开关电源的尺寸较小，重量较轻，从而减少了无源元件的尺寸，降低了热量的产生。小型化倾向的行业，随着半导体技术的发展进步，同时各种能量效率的控制使得“开关” 得到了全方位的应用，在压力-状态-响应中占主导地位。大部分的切换开关早就了今天包括PFC前端末端在内的交流输入的应用。 电源供应器出现在70年代中期。我们把这些定义为开关模式产品。开关电源的设计采用了安森美半导体元件，因此直接的称之为开关电源或SMPS。 一情况下，开关电源根据输入和输出波形可分为四种类型： 交流输入，直流输出：整流器，离线转换器输入级 直流输入，直流输出：电压转换器，或电流转换器，或直流到直流转换器 交流输入，交流输出：变频器，交交变频，变压器 直流输入，交流输出：逆变器多年来，电源设计的世界见证了从线性电源的应用逐步走向更实用的开关模式电源(SMPS)的发展过程。线性电源包含一个电源变压器和耗散系列稳压器。这意味着供应器有着非常大且沉重的50/60赫兹变压器，同时，能量转换效率非常的低，两者都是严重的缺陷。30的典型效率是线性的标准关系。相比较70至80的效率，目前可使用开关电源设计。 此外，通过采用高开关频率，电力变压器的大小和开关电源中相关的滤波组件大大减少了比较线性。例如，一个开关电源在20 kHz的条件下工作，所产生的元件尺寸减少了4倍，使得增加了约8倍，在100千赫或者以上。这意味着开关电源的设计可以产生非常紧凑和轻重量的供应。这是现在大部分电子系统的基本要求。供应必须插入到电子系统设计师为它留下的不断缩小的空间。 转换器的核心是高频逆变器部分，高频逆变器的输入电源在极高的频率下切换(使用现有技术20 to 200kHz)，然后过滤，产生平滑的直流输出。可以决定如何转移能量的电路结构被称为开关电源拓扑结构，这是设计过程中极其重要的组成部分。拓扑的组成包括一个变压器，电感，电容和功率半导体元件。 规律的输出提供了一个稳定的在控制/反馈块进行的直流电源。一般而言，大多数开关电源系统运行在固定频率的脉冲宽度调制的基础上，电源开关驱动器的时间范围在一个循环周期的基础上是不尽相同的。这个办法弥补了输入电源和输出负载产生的变化。把输出电压与准确的参考供应进行比较，由比较所产生的误差电压，可使用专门的控制逻辑来终止在正确实例中主电源开关的驱动器脉冲。正确的设计，将能提供一个非常稳定的AC输出供应。 在大多数应用中，开关电源拓扑结构包含一个电源变压器。电源变压器提供隔离，电压通过转率缩放，并能提供多种输出电压。当然，也有非隔离拓扑(没有变压器)，例如降压和升压转换器，功率处理通过感性能量的单独转移达到。所有更复杂的安排，都是以这些非隔离类型作为基础的。 自从我们引进双极功率晶体管和专门设计的开关整流器以来，安森美半导体一直是开关电源的半导体产品的主要供应商。 高效的电力转换正逐渐成为公司乃至整个社会首要关注的话题。开关电源不仅提供更高的效率，并为设计者提供了更大的灵活性。半导体的最新发展，磁和无源技术，使得开关电源在如今的电源转换舞台上日益成为更加普遍的选择。 历史上，线性稳压器是产生稳定输出电压的主要方法。通过线性控制针对其负载变化的一系列功率器件的导电，从而减少较高的输入电压降低到较低的输出电压，进而使得线性稳压器得以运行。这导致一个大的电压被放置在整个传递单位，同时伴随着负载电流流过传递单位。这种余量亏损导致线性稳压器只有百分之三十至五十的效率。这意味着每传递给负载一瓦功率，至少每瓦在热上都有消退。散热器的成本实际上使线性稳压器在10瓦以上的小型应用中变得不经济。下面这一点，然而，它们在降压应用中符合成本效益。开关稳压器作用于电源设备整版和截止的状态。这就导致了，当大的电流流过电源设备时“接通”电压低，或者当没有电流流过时，有大的电压通过设备。这导致了在供应上消耗了更低的动力。无论输入电压，开关电源的显示平均效率在百分之七十到百分之九十之间。更高的集成度迫使开关电源的费用下降，使之在输出功率高于10瓦或期望得到多重输出的场合成为具有吸引力的选择。 拓扑是功率器件和他们的磁性元件的排列。每个拓扑在某些应用上有它自身的优点。决定着一个特定的拓扑结构是否适合某一个应用的因素有： (1) 拓扑结构从输入到输出所用的电是不是孤立的。 (2) 穿过电感或变压器所安置的输入电压的大小。 (3) 通过功率半导体的峰值电流是什么。 (4) 是否需要多个输出。 (5) 出现在功率半导体两端的电压的大小。 设计者面临的第一个选择是，是否有输入到输出变压器的隔离。非隔离开关电源，通常被用于系统内其他地方提供的介质阻抗的板级调节。非隔离拓扑结构也应该用在出现故障有可能无法连接输入电源的易损坏负载电路。隔离变压器应该用在其他所有情况。多重输出电压需要与隔离变压器相结合。变压器为增加额外的输出电压的开关电源提供了一个简单的方法。该公司建立自己的电力系统倾向于在尽可能多的电源中配置隔离变压器，因为它可以在故障条件中防止多米诺骨牌效应。其余的因素包含了功率半导体正遭受了多大的压力。各种拓扑结构的差异过去常用在开关电源内。变压器隔离拓扑通常应用在各种功率和电压水平的电力工业中。在降低直流输入电压，提高功率的情况中，电源开关逐渐增大然后影响到他们必须承受压力，使得峰值电流能够始终保持。各个领域证明，适合的拓扑结构，在输入电压和输出功率的变化范围内，展示了功率半导体承受最小压力。 现今，当电是由交流电源线提供时，电源使用电容输入滤波器。造成的缺点是，交流线是用来整流，导致当交流电压达到峰值时，电流也达到峰值。这些峰值电流通常是电源所提供的平均电流3到5倍。这会造成线路系统中电压过度下降，三相传递系统中的不平衡问题。此外，交流线路的全部能量潜力尚未完全利用。 我们的任务是增加交流整流器的传导角度，使最终产生的电流的波阵面随着电压波形的位相的变化尽可能看起来像正弦。通过这种方式，电源通过线提供的电力使真正电力增至最大限度。完成这个的一个普遍方法是对实际的电力供应使用一个升压转换器。升压模式供应显示了所有开关电源拓扑结构的最大输入动态动态范围。输入电压降至30伏，它的输出电压可以提升至370伏(高于预期的最高峰值交流工作电压)。大容量输入滤波电容，如今被放置在升压转换器的输出。输入电容，随着50/60赫兹整流桥出现，如今小于1微法。这将产生一个输入电压波形的PFC电路，具有更高层次的纹波电压，升压转换器直接通过线得到它的电力。 半导体在功率因数校正阶段内有一些特殊的要求。首先，50/60赫兹整流器如今必须超快速整流，因为快速电流脉冲是通过它们提供的。如果升压转换器是在连续模式下运行，那么升压输出整流器必须超快。电源开关已清除了二极管的反向恢复电荷。在非连续模式(引脚200瓦)下，输出整流器不必超快，因为在开启电源优先开启的情况下，没有电流流过前二极管。附件2：外文原文Using Power Semiconductors in Switched Mode TopologiesThe electric energy is not normally used in the form in which it was produced or distributed. Practically all electronic systems require some form of energy conversion. A device that transfers electric energy from a given source to a given load using electronic circuits is referred to as Power Supply.A typical application of a power supply unit (PSU) is convert utility AC voltage into regulated DC voltage required for electronic equipment. Nowadays in PSU the energy flow is controlled with semiconductors that are continuously switching on an off with high frequency. Such devices are referred to as switch mode power supplies or SMPS. They offer greater efficiency compared with linear supplies because a switch can control energy flow with low losses: when a switch is off, it blocks the flow of voltage and current, can be relatively low in both states. SMPS are also smaller in size and lighter in weight due to the reduced size of passive components and lower heat generation. The industry tended toward miniaturization, advancements in semiconductor technology, as well as various energy efficiency regulations have made switch the dominant type of PSR across practically the full spectrum of applications. Most of the switchers manufactured today for AC input applications include a PFC front end.Power supplies in the mid70s. We identified these as SWITCHMODE products. A switching power supply designed using ON Semiconductor components can rightfully be called a SWITCH MODE power supply or SMPS.In general, SMPS can be classified into four types according to the input and output waveforms:AC in, DC out: rectifier, off-line converter input stage DC in, DC out: voltage converter, or current converter, or DC to DC converter AC in, AC out: frequency changer, cycloconverter, transformer DC in, AC out: inverterFor many years the world of power supply design has seen a gradual movement away from the use of linear power supplies to the more practical switched mode power supply (S.M.P.S.). The linear power supply contains a mains transformer and a dissipative series regulator. This means the supply has extremely large and heavy 50/60 Hz transformers, and also very poor power conversion efficiencies, both serious drawbacks. Typical efficiencies of 30% are standard for a linear. This compares with efficiencies of between 70% and 80%, currently available using S.M.P.S. designs. Furthermore, by employing high switching frequencies, the sizes of the power transformer and associated filtering components in the S.M.P.S. are dramatically reduced in comparison to the linear. For example, an S.M.P.S. operating at 20 kHz produces a 4 times reduction in component size, and this increases to about 8 times at 100 kHz and above. This means an S.M.P.S. design can produce very compact and lightweight supplies. This is now an essential requirement for the majority of electronic systems. The supply must slot into an ever shrinking space left for it by electronic system designers.At the heart of the converter is the high frequency inverter section, where the input supply is chopped at very high frequencies (20 to200kHz using present technologies) then filtered and smoothed to produce dc outputs. The circuit configuration which determines how the power is transferred is called the TOPOLOGY of the S.M.P.S., and is an extremely important part of the design process. The topology consists of an arrangement of transformer, inductors, capacitors and power semiconductors.Regulation of the output to provide a stabilized DC supply is carried out by the control / feedback block. Generally, most S.M.P.S. systems operate on a fixed frequency pulse width modulation basis, where the duration of the on time of the drive to the power switch is varied on a cycle by cycle basis. This compensates for changes in the input supply and output load. The output voltage is compared to an accurate reference supply, and the error voltage produced by the comparator is used by dedicated control logic to terminate the drive pulse to the main power switch/switches at the correct instance. Correctly designed, this will provide a very stable AC output supply.In most applications, the S.M.P.S. topology contains a power transformer. This provides isolation, voltage scaling through the turns ratio, and the ability to provide multiple outputs. However, there are non-isolated topologies (without transformers) such as the buck and the boost converters, where the power processing is achieved by inductive energy transfer alone. All of the more complex arrangements are based on these non-isolated types.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 switchingEfficient 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.Historically, the linear regulator was the primary method of creating a regulated output voltage. It operates by reducing a higher input voltage down to the lower output voltage by linearly controlling the conductivity of a series pass power device in response to changes in its load. This results in a large voltage being placed across the pass unit with the load current flowing through it. This headroom loss causes the linear regulator to only be 30 to 50 percent efficient. That means that for each watt delivered to the load, at least a watt has to be dissipated in heat. The cost of the heatsink actually makes the linear regulator uneconomical above 10 watts for small applications. Below that point, however, they are cost effective in step-down applications. The switching regulator operates the power devices in the full-on and cutoff states. This then results in either large currents being passed through the power devices with a low “on” voltage or no current flowing with high voltage across the device. This results in a much lower power being dissipated within the supply. The average switching power supply exhibits efficiencies of between 70 to 90 percent, regardless of the input voltage. Higher levels of integration have driven the cost of switching power supplies downward which makes it an attractive choice for output powers greater than 10 watts or where multiple outputs are desired.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. The remainder of the factors involves how much stress the power semiconductors are being subjected to. The differences between the various topologies used within switching power supplies. The transformer-isolated topologies are typically used within the power industry at various power and voltage levels. At reduced DC input voltages and at higher powers, the peak currents that must be sustained by the power switch grow higher which then affects the stress they must endure. The various areas show which topology best fits within that range of input voltage and output power that exhibits the least amount of stress on the power semiconductors.The 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 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 sinuso