脉宽调制技术外文翻译

毕业设计外文资料翻译学院：专业：姓名：学号：外文出处： Home Power #75·February/March2000 (用外文写)24.437 Power Electronics附件： 1.外文资料翻译译文；2.外文原文。

附件1：外文资料翻译译文自制程序脉冲幅宽调节——应用于12-24伏G．弗勒斯特库克宽幅脉冲调节器(PWM)可以作为调光器使用，还可以作为直流电机调速器。

这里所描述的设备可以控制几安培的直流电流。

该电路系统可以用于调节12-24伏内的微小变化。

此设备已被用于控制汽车尾灯亮度，以及电脑电源控制的小型直流风扇的转速。

脉冲幅宽调节一个PWM电路的工作原理是形成一系列占空比率可控的直流脉冲方波。

在平均时间内可以有0-100%的不同变化。

这样，就能把量化的电力传送到负载。

PWM电路相比于电阻功率控制器上的的主要优点是效率更高。

在PWM的50%的水平时，将使用全部功率的50%，几乎将所有这些都转移到负载。

而在电阻功率控制器的50%水平时，将消耗约全部功率的71%；50%的功率转移到负载，另外21%的能量浪费到了加热电阻上。

根据负载电流，通常PWM电路浪费的功率远低于1%。

它需要在连续恒定功率下运行，所以更多被用于高功率负载的效率提高。

优势能源再生系统中的关键是提高负载效率。

一个脉宽调制器的另一个优点是，有充分的脉冲电源电压，并且产生一个更容易克服电机内阻的更大的扭矩。

而一个电阻功率控制器对电机速度的控制会使电压减弱，这将导致电机反应延迟。

最后，在PWM电路，常见的小电位器可用于控制各种负载，而大型和昂贵的高功率可变电阻器必须要用电阻控制器。

缺点脉宽调制电路的主要缺点是增加了复杂性，和可能产生射频干扰（RFI）。

射频干扰会更少通过附近的负载控制器而通过短路线，而且在某些情况下，会通过额外的电源滤波线路。

该电路会产生调幅无线干扰，这些干扰在横跨负载电容（C3）的旁路形成，远离最近的引脚。

外文原文Pulse-wiｄth mｏｄulａtｉoｎＰｕlse－width modulatioｎ（ＰWＭ）is a modｕlatiｏｎteｃhｎiｑue ｔhat ｃoｎfoｒｍs ｔh ｅｗidth of tｈｅｐulsｅ，ｆormaｌly the pulse duration，based on ｍoｄulatｏr signal informat ｉon。

Altｈｏugｈｔhｉs modｕlａｔion technique can ｂe used ｔo eｎcode ｉnforｍａｔion ｆor ｔransｍｉssion，its mａｉｎuse is to allow the coｎtrol ｏf the power suppｌieｄｔｏelecｔｒiｃａl dｅviｃes，ｅspecｉally to iｎｅrｔｉaｌｌoadｓsuch as ｍoｔｏrs．Ｉｎaｄｄｉtiｏn，ＰＷM ｉs oneｏf tｈe two prｉncｉpal algoｒｉthms usｅd in photｏvoltａic solar battｅry cｈａrｇers,［１]The aｖeｒaｇｅvａlue of voltage (ａnd ｃurreｎt）fed tｏtｈｅload iｓcontｒoｌｌe ｄｂｙｔurniｎg the swiｔch bｅｔweenｓｕpply ａｎｄｌｏad oｎand oｆｆatａfa ｓt pａｃe。

The lonｇｅr the sｗｉtcｈisｏｎcompared toｔhe oｆf periods，ｔｈe hｉｇhｅr the poweｒsupplied to tｈe load iｓ.TheＰWM switching frequenｃy has to ｂeｍucｈfaster than whaｔｗｏuld affｅct the loa ｄ，ｗｈｉch ｉs to sａy thｅdｅvice thaｔusｅs tｈe poweｒ. Typiｃalｌy swｉtchings haｖe ｔｏｂe dｏne several timeｓ a ｍinute in an electrｉc ｓtｏve,120 Ｈz iｎａlamp dｉmmeｒ,froｍfeｗkilohｅrtｚ（kHz）to tens of kHz ｆｏｒａmotor ｄrive and wｅll iｎto the tens or hundｒeｄs ｏｆkHzｉn audｉｏampｌifiers and cｏｍｐuter poｗer suppliｅs.The teｒm duｔy cyｃleｄescribes ｔhｅｐroｐortｉｏｎof 'ｏn’ ｔime toｔhｅreｇular interval or ’periｏd＇of time; a low duｔｙｃyclｅcｏｒｒesｐonds tｏlow power, becaｕse t ｈe pｏｗｅｒiｓｏｆｆfor most ｏｆthｅtime．Dｕty cyｃle ｉs eｘｐreｓsed in percｅnｔ, １00% being fuｌly on.Tｈｅmain aｄvａntage ｏｆPWM is thatｐower loss ｉn ｔhe switchinｇdevices is very low. Wheｎａswitch is off tｈere ｉs practiｃaｌly no cuｒrｅnt, anｄｗhen it iｓoｎ，there is alｍost no voltage droｐaｃｒoss the switch。

正弦波脉冲宽度调制英文缩写Sine Wave Pulse Width Modulation, often shortened as SPWM, is a technique used in power electronics to control the output voltage of an inverter or converter. It's pretty handy when you want to adjust the power delivery in a precise way.SPWM, as the name suggests, modulates the pulse width of a sine wave. This modulation is key to controlling the average voltage and, ultimately, the power output. It'slike having a dimmer switch for your electronic devices.The beauty of SPWM lies in its simplicity and effectiveness. By adjusting the pulse width, you can precisely manipulate the output voltage. This makes it perfect for applications where precise control is crucial, like in motor drives or renewable energy systems.In practical use, SPWM is implemented using digital controllers or specialized hardware. The result is a smoothand efficient power delivery, minimizing power losses and improving overall system performance.So in a nutshell, SPWM is a cool technique that lets you control the voltage output of electronic devices using sine wave pulses. It's efficient, precise, and pretty useful in a wide range of applications.。

脉冲宽度调制脉冲宽度调制（PWM）是英文“Pulse Width Modulation”的缩写，简称脉宽调制。

它是利用微处理器的数字输出来对模拟电路进行控制的一种非常有效的技术，广泛应用于测量，通信，功率控制与变换等许多领域。

一种模拟控制方式，根据相应载荷的变化来调制晶体管栅极或基极的偏置，来实现开关稳压电源输出晶体管或晶体管导通时间的改变，这种方式能使电源的输出电压在工作条件变化时保持恒定。

脉冲宽度调制（PWM）是一种对模拟信号电平进行数字编码的方法。

通过高分辨率计数器的使用，方波的占空比被调制用来对一个具体模拟信号的电平进行编码。

PWM信号仍然是数字的，因为在给定的任何时刻，满幅值的直流供电要么完全有(ON)，要么完全无(OFF)。

电压或电流源是以一种通(ON)或断(OFF)的重复脉冲序列被加到模拟负载上去的。

通的时候即是直流供电被加到负载上的时候，断的时候即是供电被断开的时候。

只要带宽足够，任何模拟值都可以使用PWM进行编码。

多数负载(无论是电感性负载还是电容性负载)需要的调制频率高于10Hz，通常调制频率为1kHz到200kHz之间。

许多微控制器内部都包含有PWM控制器。

例如，Microchip公司的PIC16C67内含两个PWM控制器，每一个都可以选择接通时间和周期。

占空比是接通时间与周期之比；调制频率为周期的倒数。

执行PWM操作之前，这种微处理器要求在软件中完成以下工作：* 设置提供调制方波的片上定时器/计数器的周期* 在PWM控制寄存器中设置接通时间* 设置PWM输出的方向，这个输出是一个通用I/O管脚* 启动定时器* 使能PWM控制器PWM的一个优点是从处理器到被控系统信号都是数字形式的，无需进行数模转换。

让信号保持为数字形式可将噪声影响降到最小。

噪声只有在强到足以将逻辑1改变为逻辑0或将逻辑0改变为逻辑1时，也才能对数字信号产生影响。

对噪声抵抗能力的增强是PWM相对于模拟控制的另外一个优点，而且这也是在某些时候将PWM用于通信的主要原因。

51单片机脉宽调制控制器外文文献及翻译51单片机脉宽调制控制器外文文献及翻译Design of PWM Controller in a MCS-51 Compatible MCU Yue-Li Hu, Wei Wang Microelectronic Research & Development Center,Key Laboratory of Advanced Display and System Applications (Shanghai University), Ministry of Education Campus P.O.B.221, 149 Yanchang Rd, Shanghai 200072, ChinaE-mail: ****************AbstractThis paper presents a design of Pulse-Width Modulated(PWM) controller module in a MCU based on MCS-51structure. The design can generate 2-channel programmable periodic PWM signals. These output PWM signals from MCU can be used for a variety of applications including motor control. The function of the design allows users to select independent or complementary inversion timing relationships between 2 PWM wave forms. The latter mode selection also includes optional dead time function to support driving H-bridges and inverters. Therefore, users can controlthe output PWM signals through setting the duty-cycle registers. After the successful simulation at the front end, practical experiments made on a NIOS development board verify the design.1. IntroductionPWM technology is a kind of voltage regulation method by controlling the switch frequency of DC power with fixed voltage to modify the two-end voltage of load.This technology can be used for a variety of applications including motor control, temperature control and pressure control and so on. In the motor control system shown as Fig. 1, through adjusting the duty cycle of power switch, the speed of motor can be controlled. As shown in Fig. 2, under the control of PWM signal, the average of voltage that controls the speed of motor changes with Duty-cycle ( D = t1/T in this Figure ),thus the motor speed can be increased when motor power turn on, decreased when power turn off.Fig.1 PWM control block diagramFig.2: The Relationship between Voltage of Armature and Duty-cycle Therefore, the motor speed can be controlled with regularly adjusting the time of turn-on and turn-off. There are three methods could achieve the adjustment of duty cycle: (1)Adjust frequency with fixed pulse-width. (2) Adjust both frequency and pulse-width. (3) Adjust pulse-width with fixed frequency.Generally, there are four methods to generate the PWM signals as the following: (1) Generated by the device composed of separate logic components. This method is the original method which now has been discarded. (2) Generated by software. This method need CPU to continuously operate instructions to control I/O pins for generating PWM output signals, so that CPU can not do anything other. Therefore, the method also has been discarded gradually. (3) Generated by ASIC. The ASIC makes a decrease of CPU burden and steady work generally has several functions such as over-current protection, dead-time adjustment and so on. Then the method has been widely used in many kinds of occasion now. (4) Generated byPWM function module of MCU. Through embedding PWM function module in MCU and initializing the function六-维^论'文.网 , PWM pins of MCU can also automatically generate PWM out signals without CPU controlling only when need to change duty-cycle. It is the method that will be implemented in this paper.In this paper, we propose a PWM module embedded in a 8051 microcontroller. The PWM module can support PWM pulse signals by initializing the control register and duty-cycle register with three methods just mentioned above to adjust the duty cycle and several operation modes to add flexibility for user.The following section explains the architecture of the PWM module and the architectures of basic functional blocks.Section3 describes two operation modes. Experimental and simulation results verifying proper system operation are also shown in that section. Depending on mode of operation, the PWM module creates one or more pulse-width modulated signals, whose duty ratios can be independently adjusted.2. Implementation of PWM module in MCU2.1 Overview of the PWM module六-维^论'文.网A block diagram of PWM module is shown in Fig.3. It is clearly from the diagram that the whole module is composed of two sections: PWM signal generator and dead-time generator with channel select logic. The PWM function can be started by the user through implementing some instructions for initializing the PWM module. In particular, the following power and motion control applications are supported:• DC Motor• Uninterruptable Power Supply (UPS)Fig.3 Architecture of PWM ModuleThe PWM module also has the following features:• Two PWM signal outputs with complementary or independent operation• Hardware dead-time generators for complementary mode•Duty cycle updates are configurable to be immediated or synchronized to the PWM2. 2 Details of the architecture2.2.1 PMW generatorThe architecture of the 2-output PWM generator shown in Fig.3 is based on a 16-bit resolution counter which creates a pulse-width modulated signal. The system is synthesized by a system clock signal whose frequency can be divided by 4 times or 12 times through setting the value of T3M for PWM0 or T4M for PWM1 in the special register PWMCON as shown in Fig.4. To PWM0 generator, the clock to 16-bit counter will be pre-divided by 4 times by default when T3M is set to zero. And the clock will be divided by 12 times when T3M is set to 1. This is also true for PWM1. The other bits in PWMCON are explained in detail in T able 1.161551单片机脉宽调制控制器外文文献及翻译第2页Fig .4 Bit Mapping of PWMCONTable 1: The Bit Definition in PWMCONBIT DescriptionTF4 Interrupt Request for PWM0TR4 RUN bit for PWM0TF3 Interrupt Request for PWM1TR3 RUN bit for PWM1PSEL Channel Select inComplementary ModeCPWM Mode SelectT4M Clock Prescaler for PWM1T3M Clock Prescaler for PWM02.2.2 Channel-select logicThe follow Fig. 5 shows the channel-select logic which is useful in Complementary Mode. From this diagram, it is clear to know that signal CP and CPWM control the source of PWMH and PWML. And the details about the two control signals will be discussed in the section 3, and the architecture of dead-time generator will also be discussed in section 3.1 for the continuity of Complementary Mode.Fig. 5 Diagram of Channel-select Logic3. Operation Mode and Simulation ResultsThe design has two operation modes: Independent Mode and Complimentary Mode. By setting the corresponding bit CPWM in register PWMCON shown in Fig. 4, user can select one of the two operation modes. When CPWM is set to zero,PWMmodule will work in Independent Mode, whereas,PWM module will work in Complimentary Mode. In the following of this section, the two operation mode will be explained respectively in detail and the simulation results of the PWM module from the Synoposys VCS EDA platform which verify the design will also be shown.3.1 Independent PWM Output ModeAn Independent PWM Output mode is useful for driving loads such as the one shown in Figure 1. A particular PWM output is in the Independent Output mode when the corresponding CP bit in the PWMCON register is set to zero.In this case, two-channel PWM outputs are independent of each other. The signal on pin PWM0/PWMH is from PWM0 generator, and the signal on pin PWM1/PWML is from PWM0 generator. The separate case is achieved by the channel-select logic shown in Fig. 6. The PWM I/O pins are set to independent mode by default upon advice reset. The dead-time generator is disabled in the Independent mode. The simulation result is shown in Figure 4 as the following Fig.5.Tr4 and tr3 are run bits to PWM0 and PWM1, respectively.Actually, from this diagram, Pin P1[5]/ P1[4] of MCU is used for PWMH/ PWML or normal I/O ,alternatively.Fig.6 the Waveform of PWM Outputs in Independent Mode3.2 Complementary PWM Output ModeThe Complementary Output mode is used to drive inverter loads similar to the one shown in Figure 7. This inverter topology is typical for DC applications. InComplementary Output Mode, the pair of PWM outputs cannot be active simultaneously. The PWM channel and output pin pair are internally configured through channel-select logic as shown in Figure 5. A dead-time may be optionally inserted duringdevice switching where both outputs are inactive for a short period.Authorized licensed use limited to: East China Normal University. Downloaded on January 11, 2009 at 00:36 from IEEE Xplore. Restrictions apply.Proceedings of HDP’07 六-维^论'文.网The Complementary mode is selected for PWM I/O pin pair by setting the appropriate CPWM bit in PWMCON. In this case, PSEL is in effect. PWMH and PWML will come from PWM0 generator when PSEL is set to zero, when the signals from PWM1 generator is useless, whereas PWMH and PWML will come from PWM1 generator when PSEL is set to 1, when the signals from PWM0 generator is useless. In the process of producing the PWM outputs in Complementary Mode, the dead-time will be inserted to be discussed in the following section.Fig 7: Typical Load for Complementary PWM Outputs3.3 Dead-time ControlDead-time generation is automatically enabled when PWM I/O pin pair is operating in the Complementary Output mode. Because the power output devices cannot switchinstantaneously, some amount of time must be provided between the turn-offevent of one PWM output in a complementary pair and the turn-on event of the othertransistor. The 2-output PWM module has one programmable dead-time with 8-bit register.The complementary output pair for the PWM module has an 8-bit down counter that is used to produce the dead-time insertion. As shown in Figure 8, the dead time unit has a rising and falling edge detector connected to PWM signal from one of PWM generator. The dead times is loaded into the timer on the detected PWM edge event. Depending on whether the edge is rising or falling, one of the transitions on the complementary outputs is delayed until the timer counts down to zero. A timing diagram indicating the dead time insertion for the pair of PWM outputs is shown in Figure 8.Fig.8 Dead-time Unit Block DiagramConclusionsIn this paper, we have designed PWM module based on an 8-bit MCU compatible with 8051 family. The design can generate 2-channel programmable periodic PWM signals with two operation mode, Independent Mode and Complementary Mode in which dead-time will be inserted. The simulation results on the EDA platform have proven its correctness andusefulness.AcknowledgmentsThe authors would like to thank Shanghai Leading Academic Discipline Project (Project Number: T0103) for the financial support.51单片机脉宽调制控制器外文文献及翻译第3页Fig. 9 the Waveforms of PWM Outputs in ComplementaryModeReferences1. Xiang hui-fang and Hu yue-li, Computer measurement and control, 14(7) p. 942(2006)2. Hu yue-li and Ding qian, Conference on High Density Microsystem Design and Packaging and Component Failure Analysis, p.267 (2006)3. Yue-Li Hu and Bing Xiong, Proceedings of 2006 Conf. on High Density Microsystem Design and Packaging and Component Failure Analysis (HDP’06), China, p.278(2006).六-维^论'文.网4. Yue-Li Hu, Jia-Lin Cao, Feng Ran and Zhi-Jian Liang,Proceedings of 2004 Conf. on High Density Microsystem Design and Packaging and Component Failure Analysis(HDP'04),China, p.25(2004)5. JING Wei-liang, HU Yue-li, CAO Jia-lin. “Design of 16MB Addr essing Spaces in an MCU Based on the MCS-51 Structure,”The 7th IEEE CPMT Conference on HighDensity Microsystem Design and Packaging and Component Failure Analysis (HDP’05),Shanghai,China,June30-July 3,(2005), pp.509-512.6. Peterchev, A.V, Jinwen Xiao; S anders, S.R, “Architecture and IC implementation of a digital VRM controller,”Power Electronics, IEEE Transactions on Volume 18, Issue 1, Part 2, Jan. 2003 Page(s):356 –364.7. Smith, K.M., Jr.; Lai, Z.; Smedley, K.M.; “A new PWM controller with one-cycle response,” Power Electronics,IEEE Transactions on Volume 14, Issue 1, Jan. 1999Page(s):142 - 150Authorized licensed use limited to: East China Normal University. Downloaded on January 11, 2009 at 00:36 from IEEE Xplore. Restrictions apply.中文译文：基于51单片机兼容的脉宽调制控制器的设计胡越黎王伟微电子研发中心，重点实验室显示器及系统应用（上海大学），教育部校园POB221，149延长路，上海200072，中国摘要：这篇论文描述了脉宽调制控制器模块在微控制器中基于51单片机构造的设计。

脉宽调制[浏览次数：158次]
脉宽调制（Pulse Width Modulation简称PWM）是靠改变脉冲宽度来控制输出电压，通过改变周期来控制其输出频率。

而输出频率的变化可通过改变此脉冲的调制周期来实现。

这样，使调压和调频两个作用配合一致，且于中间直流环节无关，因而加快了调节速度，改善了动态性能。

由于输出等幅脉冲只需恒定直流电源供电，可用不可控整流器取代相控整流器，使电网侧的功率因数大大改善。

利用PWM逆变器能够抑制或消除低次谐波。

加上使用自关断器件，开关频率大幅度提高，输出波形可以非常接近正弦波。

目录
∙脉宽调制变频电路的特点
∙脉宽调制的原理
∙脉宽调制的典型电路图
∙脉宽调制技术的分类
∙脉宽调制的典型应用
脉宽调制变频电路的特点
∙ 1. 可以得到相当接近正弦波的输出电压
2. 整流电路采用二极管，可获得接近1的功率因数
3. 电路结构简单
4. 通过对输出脉冲宽度的控制可改变输出电压，加快了变频过程的动态响应。

外文原文Pulse-width modulationPulse-width modulation (PWM)is a modulation technique that conforms the width of the pulse, formally the pulse duration, based on modulator signal information. Although this modulation technique can be used to encode information for transmission, its main use is to allow the control of the power supplied to electrical devices, especially to inertial loads such as motors. In addition, PWM is one of the two principal algorithms used in photovoltaic solar battery chargers,[1]The average value of voltage (and current) fed to the load is controlled by turning the switch between supply and load on and off at a fast pace. The longer the switch is on compared to the off periods, the higher the power supplied to the load is.The PWM switching frequency has to be much faster than what would affect the load, which is to say the device that uses the power. Typically switchings have to be done several times a minute in an electric stove, 120 Hz in a lamp dimmer, from few kilohertz (kHz) to tens of kHz for a motor drive and well into the tens or hundreds of kHz in audio amplifiers and computer power supplies.The term duty cycle describes the proportion of 'on' time to the regular interval or 'period' of time; a low duty cycle corresponds to low power, because the power is off for most of the time. Duty cycle is expressed in percent, 100% being fully on.The main advantage of PWM is that power loss in the switching devices is very low. When a switch is off there is practically no current, and when it is on, there is almost no voltage drop across the switch. Power loss, being the product of voltage and current, is thus in both cases close to zero. PWM also works well with digital controls, which, because of their on/off nature, can easily set the needed duty cycle.PWM has also been used in certain communication systems where its duty cycle has been used to convey information over a communications channel.HistoryIn the past, when only partial power was needed (such as for a sewing machine motor), a rheostat (located in the sewing machine's foot pedal) connected in series with the motor adjusted the amount of current flowing through the motor, but also wasted power as heat in the resistor element. It was an inefficient scheme, but tolerable because the total power was low. This was one of several methods of controlling power. There were others—some still in use—such as variable autotransformers, including thetrademarked 'Autrastat' for theatrical lighting; and the Variac, for general AC power adjustment. These were quite efficient, but also relatively costly.For about a century, some variable-speed electric motors have had decent efficiency, but they were somewhat more complex than constant-speed motors, and sometimes required bulky external electrical apparatus, such as a bank of variable power resistors or rotating converter such as Ward Leonard drive.However, in addition to motor drives for fans, pumps and robotic servos, there was a great need for compact and low cost means for applying adjustable power for many devices, such as electric stoves and lamp dimmers.One early application of PWM was in the Sinclair X10, a 10 W audio amplifier available in kit form in the 1960s. At around the same time PWM started to be used in AC motor control.Fig. 1: a pulse wave, showing the definitions of , and D.Pulse-width modulation uses a rectangular pulse wave whose pulse width is modulated resulting in thevariation of the average value of the waveform. If we consider a pulse waveform , with period ,low value , a high value and a duty cycle D (see figure 1), the average value of thewaveform is given by:As is a pulse wave, its value is for and for. The above expression then becomes:This latter expression can be fairly simplified in many cases where as. From this, it is obvious that the average value of the signal () is directly dependent on the duty cycle D大连交通大学2014届本科生毕业论文外文翻译Fig. 2: A simple method to generate the PWM pulse train corresponding to a given signal is the intersective PWM: the signal (here the red sinewave) is compared with a sawtooth waveform (blue). When the latter is less than the former, the PWM signal (magenta) is in high state (1). Otherwise it is in the low state (0).The simplest way to generate a PWM signal is the intersective method, which requires only a sawtooth or atriangle waveform (easily generated using a simple oscillator) and a comparator. When the value of the reference signal (the red sine wave in figure 2) is more than the modulation waveform (blue), the PWM signal (magenta) is in the high state, otherwise it is in the low state.Time proportioningMany digital circuits can generate PWM signals (e.g., many microcontrollers have PWM outputs). They normally use a counter that increments periodically (it is connected directly or indirectly to the clock of the circuit) and is reset at the end of every period of the PWM. When the counter value is more than the reference value, the PWM output changes state from high to low (or low to high).[3]This technique is referred to as time proportioning, particularly as time-proportioning control[4]– which proportion of a fixed cycle time is spent in the high state.The incremented and periodically reset counter is the discrete version of the intersecting method's sawtooth. The analog comparator of the intersecting method becomes a simple integer comparison between the current counter value and the digital (possibly digitized) reference value. The duty cycle can only be varied in discrete steps, as a function of the counter resolution. However, a high-resolution counter can provide quite satisfactory performance.PWM sampling theoremThe process of PWM conversion is non-linear and it is generally supposed that low pass filter signal recovery is imperfect for PWM. The PWM sampling theorem[6] shows that PWM conversion can be perfect. The theorem states that "Any bandlimited baseband signal within ±0.637 can be represented by a pulsewidth modulation (PWM) waveform with unit amplitude. The number of pulses in the waveform is equal to the number of Nyquist samples and the peak constraint is independent of whether the waveform is two-level or three-level."Power deliveryPWM can be used to control the amount of power delivered to a load without incurring the losses that would result from linear power delivery by resistive means. Potential drawbacks to this technique are the pulsations defined by the duty cycle, switching frequency and properties of the load. With a sufficiently high switching frequency and, when necessary, using additional passive electronic filters, the pulse train can be smoothed and average analog waveform recovered.High frequency PWM power control systems are easily realisable with semiconductor switches. As explained above, almost no power is dissipated by the switch in either on or off state. However, during the transitions between on and off states, both voltage and current are nonzero and thus power is dissipated in the switches. By quickly changing the state between fully on and fully off (typically less than 100 nanoseconds), the power dissipation in the switches can be quite low compared to the power being delivered to the load.Modern semiconductor switches such as MOSFETs or Insulated-gate bipolar transistors (IGBTs) are well suited components for high efficiency controllers. Frequency converters used to control AC motors may have efficiencies exceeding 98%. Switching power supplies have lower efficiency due to low output voltage levels (often even less than 2 V for microprocessors are needed) but still more than 70–80% efficiency can be achieved.Variable-speed fan controllers for computers usually use PWM, as it is far more efficient when compared to a potentiometer or rheostat. (Neither of the latter is practical to operate electronically; they would require a small drive motor.)Light dimmers for home use employ a specific type of PWM control. Home-use light dimmers typically include electronic circuitry which suppresses current flow during defined portions of each cycle of the AC line voltage. Adjusting the brightness of light emitted by a light source is then merely a matter of setting at what voltage (or phase) in the AC halfcycle the dimmer begins to provide electrical current to the light source (e.g. by using an electronic switch such as a triac). In this case the PWM duty cycle is the ratio of the conduction time to the duration of the half AC cycle defined by the frequency of the AC line voltage (50 Hz or 60 Hz depending on the country).V oltage regulationMain article: Switched-mode power supplyPWM is also used in efficient voltage regulators. By switching voltage to the load with the appropriate duty cycle, the output will approximate a voltage at the desired level. The switching noise is usually filtered with an inductor and a capacitor.One method measures the output voltage. When it is lower than the desired voltage, it turns on the switch. When the output voltage is above the desired voltage, it turns off the switch.Audio effects and amplificationPWM is sometimes used in sound (music) synthesis, in particular subtractive synthesis, as it gives a sound effect similar to chorus or slightly detuned oscillators played together. (In fact, PWM is equivalent to the difference of two sawtooth waves with one of them inverted.[1]) The ratio between the high and low level is typically modulated with a low frequency oscillator. In addition, varying the duty cycle of a pulse waveform in a subtractive-synthesis instrument creates useful timbral variations. Some synthesizers have a duty-cycle trimmer for their square-wave outputs, and that trimmer can be set by ear; the 50% point (true square wave) was distinctive, because even-numbered harmonics essentially disappear at 50%. Pulse waves, usually 50%, 25%, and 12.5%, make up the soundtracks of classic video games.A new class of audio amplifiers based on the PWM principle is becoming popular. Called "Class-D amplifiers", they produce a PWM equivalent of the analog input signal which is fed to the loudspeaker via大连交通大学2014届本科生毕业论文外文翻译a suitable filter network to block the carrier and recover the original audio. These amplifiers are characterized by very good efficiency figures (≥ 90%) and compact size/light weight for large power outputs. For a few decades, industrial and military PWM amplifiers have been in common use, often for drivingservo motors. Field-gradient coils in MRI machines are driven by relatively high-power PWM amplifiers.Historically, a crude form of PWM has been used to play back PCM digital sound on the PC speaker, which is driven by only two voltage levels, typically 0 V and 5 V. By carefully timing the duration of the pulses, and by relying on the speaker's physical filtering properties (limited frequency response, self-inductance, etc.) it was possible to obtain an approximate playback of mono PCM samples, although at a very low quality, and with greatly varying results between implementations.In more recent times, the Direct Stream Digital sound encoding method was introduced, which uses a generalized form of pulse-width modulation called pulse density modulation, at a high enough sampling rate (typically in the order of MHz) to cover the whole acoustic frequencies range with sufficient fidelity. This method is used in the SACD format, and reproduction of the encoded audio signal is essentially similar to the method used in class-D amplifiers.中文翻译一、脉冲宽度调制脉冲宽度调制（PWM），是一种在一定的脉冲持续时间内，基于调制信号来追踪所希望达到的脉冲宽度的调制方式。

PWM（脉冲宽度调制PulseWidthModulation）原理1、 PWM原理2、调制器设计思想3、具体实现设计⼀、 PWM（脉冲宽度调制Pulse Width Modulation）原理：脉冲宽度调制波通常由⼀列占空⽐不同的矩形脉冲构成，其占空⽐与信号的瞬时采样值成⽐例。

图1所⽰为脉冲宽度调制系统的原理框图和波形图。

该系统有⼀个⽐较器和⼀个周期为Ts的锯齿波发⽣器组成。

语⾳信号如果⼤于锯齿波信号，⽐较器输出正常数A，否则输出0。

因此，从图1中可以看出，⽐较器输出⼀列下降沿调制的脉冲宽度调制波。

通过图1b的分析可以看出，⽣成的矩形脉冲的宽度取决于脉冲下降沿时刻t k时的语⾳信号幅度值。

因⽽，采样值之间的时间间隔是⾮均匀的。

在系统的输⼊端插⼊⼀个采样保持电路可以得到均匀的采样信号，但是对于实际中tk-kTs<（1）其中，x{t}是离散化的语⾳信号；Ts是采样周期；是未调制宽度；m是调制指数。

然⽽，如果对矩形脉冲作如下近似：脉冲幅度为A，中⼼在t = k Ts处，在相邻脉冲间变化缓慢，则脉冲宽度调制波x p(t)可以表⽰为：（2）其中，。

⽆需作频谱分析，由式（2）可以看出脉冲宽度信号由语⾳信号x(t)加上⼀个直流成分以及相位调制波构成。

当时，相位调制部分引起的信号交迭可以忽略，因此，脉冲宽度调制波可以直接通过低通滤波器进⾏解调。

⼆、数字脉冲宽度调制器的实现：实现数字脉冲宽度调制器的基本思想参看图2。

图中，在时钟脉冲的作⽤下，循环计数器的5位输出逐次增⼤。

5位数字调制信号⽤⼀个寄存器来控制，不断于循环计数器的输出进⾏⽐较，当调制信号⼤于循环计数器的输出时，⽐较器输出⾼电平，否则输出低电平。

循环计数器循环⼀个周期后，向寄存器发出⼀个使能信号EN，寄存器送⼊下⼀组数据。

在每⼀个计数器计数周期，由于输⼊的调制信号的⼤⼩不同，⽐较器输出端输出的⾼电平个数不⼀样，因⽽产⽣出占空⽐不同的脉冲宽度调制波。

脉冲宽度调制————————————————————————————————作者：————————————————————————————————日期:ﻩ脉冲宽度调制脉冲宽度调制(PWM）,是英文“Pｕlse Ｗidth Ｍoｄulatｉon”的缩写，简称脉宽调制,是利用微处理器的数字输出来对模拟电路进行控制的一种非常有效的技术，广泛应用在从测量、通信到功率控制与变换的许多领域中。

目录1简介2背景介绍3基本原理4谐波频谱5具体过程6优点7控制方法8应用领域９具体应用１简介脉冲宽度调制是一种模拟控制方式，其根据相应载荷的变化来调制晶体管基极或ＭOS管栅极的偏置,来实现晶体管或MOS管导通时间的改变,从而实现开关稳压电源输出的改变。

这种方式能使电源的输出电压在工作条件变化时保持恒定，是利用微处理器的数字信号对模拟电路进行控制的一种非常有效的技术。

ＰＷM控制技术以其控制简单，灵活和动态响应好的优点而成为电力电子技术最广泛应用的控制方式,也是人们研究的热点。

由于当今科学技术的发展已经没有了学科之间的界限,结合现代控制理论思想或实现无谐振软开关技术将会成为PWＭ控制技术发展的主要方向之一。

2背景介绍随着电子技术的发展,出现了多种PＷM技术，其中包括：相电压控制ＰWM、脉宽ＰＷM法、随机ＰＷM、SPWM法、线电压控制PWM等，而在镍氢电池智能充电器中采用的脉宽PWM法,它是把每一脉冲宽度均相等的脉冲列作为PWM波形，通过改变脉冲列的周期可以调频，改变脉冲的宽度或占空比可以调压,采用适当控制方法即可使电压与频率协调变化。

可以通过调整PＷM的周期、PWM的占空比而达到控制充电电流的目的。

模拟信号的值可以连续变化,其时间和幅度的分辨率都没有限制。

9V电池就是一种模拟器件，因为它的输出电压并不精确地等于9V，而是随时间发生变化，并可取任何实数值。

与此类似，从电池吸收的电流也不限定在一组可能的取值范围之内。

模拟信号与数字信号的区别在于后者的取值通常只能属于预先确定的可能取值集合之内，例如在{０V，５V}这一集合中取值。

脉冲宽度调制电路的设计与实现英文Pulse Width Modulation Circuit Design and Implementation IntroductionPulse Width Modulation (PWM) is a commonly used technique in power electronics to control the amount of power delivered to a load. It involves varying the width of a pulse with respect to a period, where the average voltage delivered to the load is proportional to the duty cycle of the pulse. In this article, we will discuss the design and implementation of a PWM circuit.Circuit DiagramThe PWM circuit consists of a Comparator, Astable Multivibrator, RC circuit and a Power MOSFET. The circuit diagram is shown below:[Insert Circuit Diagram]Working PrincipleThe operation of the PWM circuit can be understood by the following steps:1. A triangle wave signal is generated by the Astable Multivibrator with a frequency f.2. The output of the Astable Multivibrator is compared with a DC voltage signal Vref by the Comparator.3. The Comparator output switches between high and low depending on the comparison result.4. The RC circuit filters the Comparator output signal to obtain a PWM signal.5. The Power MOSFET switches on and off according to the PWM signal, delivering power to the load.Design ConsiderationsThe following design considerations should be taken into account while designing the PWM circuit:1. The frequency of the Astable Multivibrator should be chosen to be higher than the maximum frequency of the load.2. The amplitude of the triangle wave should be large enough to allow sufficient variation of the duty cycle.3. The value of the RC circuit should be chosen such that the filtered PWM signal has a smooth transition between high and low states.4. The Power MOSFET should be chosen such that it can operate at the frequency of the PWM signal and handle the power delivered to the load.ImplementationThe following steps should be followed while implementing the PWM circuit:1. Choose appropriate values for the components according to the design considerations.2. Construct the circuit on a breadboard, using a Power MOSFET of appropriate rating.3. Connect a load to the output of the Power MOSFET andverify its operation using an oscilloscope.4. Test the circuit at different duty cycles and measure the voltage and current delivered to the load.5. Modify the circuit or choose different components if necessary to achieve the desired performance.ConclusionIn this article, we discussed the design and implementation of a PWM circuit. PWM is a widely used technique in power electronics to control the output power of a load. By following the design considerations and implementation steps,engineers can design and build PWM circuits for various applications.。