《毕业设计(论文)文献综述及外文文献翻译》.doc

华中科技大学文华学院毕业设计（论文）外文文献翻译（本科学生用）题 目：多功能报警器的设计与试验学 生 姓 名：王 辉 学号 070108041119学 部 （系）:信息学部（控制科学与技术系）专 业 年 级: 自动化074指 导 教 师：何兆湘 职称或学位：副教授 2011年 03月 21日 外文文献翻译（译成中文1000字左右）：【主要阅读文献不少于5篇，译文后附注文献信息，包括：作者、书名（或论文题目）、出 版 社（或刊物名称）、出版时间（或刊号）、页码。提供所译外文资料附件（印刷类含封面、封底、目录、翻译部分的复印件等，网站类的请附网址及原文】译文：应用TL494设计的开关稳压电源 标准线性与逻辑 摘要作者详细讨论了TL494的的电源控制器。作者对TL494的体系结构所作的一般概述呈现了包含在设备中的主要功能模块。作者对功能模块之间的相互关系的一项深入研究，突出了TL494的通用性和局限性。该TL494的电源控制器的作用通过几个基本应用展现出来，以及一个设计的例子如设计一个5-V/10-A电源供应也包括在内。 简介自从他们在1970年引进以来，用于开关电源控制的单片集成电路已经普及。TL494结合了许多功能，这些功能以前需要几个不同的控制电路。本应用报告的目的是使读者对TL494的功能、性能、特点，以及它的局限性有个全面的了解。基本设备TL494的设计不仅包含了主要的建设模块，我们需要用这些模块来控制电源开关，而且也也标记了许多基本问题的地址，并且减少在总设计中需要的额外电路的数量。图1:TL494的框图操作原理TL494是一个固定频率脉冲宽度调制（PWM）控制电路。输出脉冲调制是通过比较锯齿波形来完成的，这些锯齿波形是由两个中的任一个控制信号的定时电容上的内部振荡器创造的。输出级是在锯齿电压比电压控制信号更大期间启用的。由于控制信号增加，锯齿波输入的时间减少，因此，输出脉冲持续时间减少。一个脉冲转向触发器交替地指示对两个中的每个输出晶体管的脉冲调制器。图2显示了脉冲和信号之间的关系。图2：TL494的调制技术控制信号来自两个来源：死区时间（截止时间）控制电路，误差放大器。死区时间控制输入是通过死区时间控制器直接比较的。这个比较器有一个固定的100 mV的透印版印刷。随着偏置到地面控制输入，在锯齿波形低于110毫伏期间，输出过程就被禁止。这提供了约3的预置死区时间，这是能被编程的最少的死区时间。PWM比较器比较了由误差放大器的创造的控制信号，误差放大器的一个功能是用来监视输出电压和提供足够的增益，使在其输入的毫伏误差导致一个足够振幅的控制信号，以提供100%的调制控制。错误放大器也可用于监视输出电流和提供给负载的电流限制。5- V参考电压调节器TL494内部的5- V基准稳压器，如图3所示。它除了提供一个稳定的基准显示，还充当一个前置稳压器，并建立了稳定的供应量，从这些稳定的供应量中，输出控制逻辑，脉冲转向触发器，振荡器，死时间控制比较器和PWM比较器得以供电。该稳压器采用一个带隙电路作为它的主要参考，以维持低于100毫伏的变化通过经营自由空气的温度范围0C到70C内的热稳定性。短路保护被用来保护内部参考和前置稳压器，负载电流10毫安可用于额外的偏置电路。该参考是用来5的初始精度的内部编程，以及维护稳定低于25毫伏变化的一个多输入电压范围7 V至40 V的稳定性。对于少于7 V的输入电压，稳压器在输入的和跟踪它的1伏内饱和（参见图4）。图3：5- V参考电压调节器图4：参考电压与输入电压振荡器TL494的内部振荡器原理图如图五所示。振荡器提供了一个积极的锯齿波形的死区时间和对各种控制信号比较的PWM比较器。图5：内部振荡器原理图附录：原文Designing Switching Voltage Regulators With the TL494 Standard Linear & LogicABSTRACTThe TL494 power-supply controller is discussed in detail. A general overview of the TL494 architecture presents the primary functional blocks contained in the device. An in-depth study of the interrelationship between the functional blocks highlights versatility and limitations of the TL494. The usefulness of the TL494 power-supply controller also is demonstrated through several basic applications, and a design example is included for a 5-V/10-A power supply.IntroductionMonolithic integrated circuits for the control of switching power supplies have becomewidespread since their introduction in the 1970s. The TL494 combines many features thatpreviously required several different control circuits. The purpose of this application report is to give the reader a thorough understanding of the TL494, its features, its performancecharacteristics, and its limitations.The Basic DeviceThe design of the TL494 not only incorporates the primary building blocks required to control a switching power supply, but also addresses many basic problems and reduces the amount of additional circuitry required in the total design. Figure 1 is a block diagram of the TL494.Figure 1. TL494 Block DiagramPrinciple of OperationThe TL494 is a fixed-frequency pulse-width-modulation (PWM) control circuit. Modulation of output pulses is accomplished by comparing the sawtooth waveform created by the internal oscillator on the timing capacitor (CT) to either of two control signals. The output stage is enabled during the time when the sawtooth voltage is greater than the voltage control signals. As the control signal increases, the time during which the sawtooth input is greater decreases; therefore, the output pulse duration decreases. A pulse-steering flip-flop alternately directs the modulated pulse to each of the two output transistors. Figure 2 shows the relationship between the pulses and the signals.Figure 2. TL494 Modulation TechniqueThe control signals are derived from two sources: the dead-time (off-time) control circuit and the error amplifier. The dead-time control input is compared directly by the dead-time control comparator. This comparator has a fixed 100-mV offset. With the control input biased to ground, the output is inhibited during the time that the sawtooth waveform is below 110 mV. This provides a preset dead time of approximately 3%, which is the minimum dead time that can be programmed. The PWM comparator compares the control signal created by the error amplifiers. One function of the error amplifier is to monitor the output voltage and provide sufficient gain so that millivolts of error at its input result in a control signal of sufficient amplitude to provide 100% modulation control. The error amplifiers also can be used to monitor the output current and provide current limiting to the load.5-V Reference RegulatorThe TL494 internal 5-V reference regulator is shown in Figure 3. In addition to providing a stable reference, it acts as a preregulator and establishes a stable supply from which the output-control logic, pulse-steering flip-flop, oscillator, dead-time control comparator, and PWM comparator are powered. The regulator employs a band-gap circuit as its primary reference to maintain thermal stability of less than 100-mV variation over the operating free-air temperature range of 0_C to 70_C. Short-circuit protection is provided to protect the internal reference and preregulator, 10 mA of load current is available for additional bias circuits. The reference is internally programmed to an initial accuracy of 5% and maintains a stability of less than 25-mV variation over an input voltage range of 7 V to 40 V. For input voltages less than 7 V, the regulator saturates within 1 V of the input and tracks it (see Figure 4).Figure 3. 5-V Reference RegulatorFigure 4. Reference Voltage