一个灵活的LED驱动汽车照明应用集成电路设计和实验特征毕业设计文献翻译

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1、 毕业设计文献翻译院系： 电子电气工程学院 学 号： 021309208 姓 名： 吴骁奕 指导教师： 曾国辉 完成时间： 2013/2/15 文献翻译021309208 吴骁奕A Flexible LED Driver for Automotive Lighting Applications: IC Design and Experimental Characterization一个灵活的LED驱动汽车照明应用:集成电路设计和实验特征AbstractThis letter presents a smart driver for LEDs, particularly摘要：这文章提出了一个智能驱

2、动发光二极管，for automotive lighting applications, which avoid ringing尤其是用于避免振荡和超调现象的汽车照明应用上，and overshoot phenomena. To this aim, advanced Soft Start and为了这个目的，在芯片上集成了优化软启动和电流升降控制技术。Current Slope Control techniques are integrated on-chip. This letter这篇文章讨论了设计于集合于高电压的互补金属氧化半导体上的驱动技术，discusses the driver d

3、esign integrating in high voltage CMOStechnology, the digital circuitry for programming and electronic用于编程和电子控制单元连接的数字电路以及功率元件提高到10瓦特。control units interfacing, and the power devices up to 10W. Experimental同时也展示了不同功率等级使用的发光二极管和与不同类型的连接时的实验特征。characterizations with LEDs of different power levels andw

4、ith different types of connections are showed. The smart driver这个智能的驱动适用于可调节的温度和电压需求。sustains automotive temperature and voltage requirements; moreover此外，它有很高的功率效率，它是可编程的，还可以配置用于线性的调节器。it has high power efficiency, it is programmable, and can beconfigured to work as a linear regulator (for low curre

5、nt LEDs) orin switch mode (for higher power LEDs).（用于弱电流发光二极管）或转换模式（用于高功率发光二极管）IndexTermsAutomotive electronics, high voltage (HV)CMOS,integrated circuit (IC), LED driver.关键词汽车用电子设备，高电压互补金属氧化物半导体，集成电路LED驱动I. INTRODUCTION1：介绍IN the last few years LED technology experienced a very fast在过去的几年中，发光二极管技术在

6、汽车照明应用中替代普通灯泡经历了一个非常快速的进步时代，and important growth, superseding the bulb technology inautomotive lighting applications 1. To achieve the harsh requirementof CO2 emission and reduce the fuel consumption,car manufacturer must reduce the total power consumption. The为了实现了严格的二氧化碳排放要求和降低了燃料的消耗,汽车制造商必须减少总的功率

7、消耗。adoption of LEDs in place of bulbs permits to have about fivetimes less power consumption at equal output lighting intensity.采用发光二极管代替灯泡在同等输出功率照明强度下损耗将降低五倍。LEDs have reached quality and reliability factors that permittheir use in automotive harsh environment and in addition发光二极管已达到质量和可靠性因素,可保证他们可

8、使用在汽车的严酷环境下并且他们的成本是降低的。their cost is decreasing. However, LEDs are pretty difficult to事实上，发光二极管是很难驱动，因此相比较普通灯泡，发光二极管驱动要求更多的技巧和控制功能。drive and therefore LED-drivers require many tricks and controlfunctions compared to bulb drivers. Moreover, automotive而且，汽车应用程序需要紧凑和低成本的解决方案,灵活足够的数字电子控制单元界面， applicatio

9、ns require compact and low-cost solutions, flexibleenough to be interfaced to digital electronic control units (ECU)and to cope with different wiring configurations and relevant同时需要应付不同的布线配置和相关拓展。parasitics 2. Automotive lighting systems should be also robust汽车照明系统也应该对电磁干扰(EMI)和超温、过流以及过电压现象有应变能力。wit

10、h respect to electromagnetic interference (EMI) andto overtemperature, overcurrent, and overvoltage phenomena,such as those due to ringing effects generated by resonance of例如那些由于激振效应所产生的共振的线电感和连接器电容。wire inductance and connector capacitance. Usually, in car environment通常,在汽车环境中，几米长电线使用,就会生成强烈振荡。few

11、meters long wires are used, generating dumpedoscillations. Such oscillations and the associated overcurrentand overvoltage levels reduce the LED life time and its efficiency这种振荡和与之相关的过电流和过电压会降低发光二极管寿命及其效率。3. To avoid or limit these effects the LED cannot bedriven by a mechanical relay but a smart dr

12、iver is required tocontrol the slope of the LED current during transient, keeping it为了避免或限制这些影响发光二极管不能由一个机械继电器控制但智能的驱动被要求需要在瞬态控制LED电流的斜率，以保持它在电线的特征频率以下。below the characteristic frequency of the wire. A compact andefficient LED driver is needed, overcoming the above issues andfeaturing a high flexibi

13、lity to face different LED power levels,一个紧凑和高效的LED驱动程序是必要的,是为了克服上述问题和具有高灵活性，去面对不同的发光二极管功率级别，连接拓扑和电线寄生。connections topology, and wiring parasitics. Hereafter, Section此后，在第二部分，分析了振荡和电磁干扰在放光二极管驱动中的影响。II analyzes ringing and EMI problems in LED driving. SectionIII presents the design of the new LED sma

14、rt driver focusing on第三部分介绍了一款新设计的智能发光二极管驱动的显著特征。its distinguishing features. Section IV presents its experimental第四部分介绍了发光二极管在不同功率等级下的实验特征，从几十毫瓦特characterization with LEDs of different power levels, from tensof milliwatts to several watts, used stand-alone, or connected in到几瓦特在独立或几个连接下的状态。strings.

15、Temperature and voltage range operating conditions are温度和电压等级的工作条件也被测量判断。also measured. Conclusions are drawn in Section V.第五部分将引出结论。II. RINGING AND EMI PROBLEMS IN LED DRIVING二.振荡和电磁干扰在发光二极管驱动中的影响At state-of-the-art LED, driving is implemented using lowdropout linear regulators, which are limited t

16、o LEDs of few tensof milliamperes, or more power-efficient switching solutions athigher current levels 在最开始的LED,开车是使用低输出线性稳压器,仅限于几十毫安级的发光二极管,或更省电转换解决方案用在更高的电流水平。310. However, a compact solution integrating然而,一个紧凑的集成解决方案在一个单芯片数字ECU接口,on a single chip a digital ECU interface, a low-powerconfigurable l

17、ogic core, a power part able to work in linear modeor switching one, as well as advanced techniques such as SoftStart and Current Slope Control, has not been proposed yet in一个低功耗可配置的逻辑核心,电源部分能够工作在线性模式或转换它,以及先进的技术,如软开始和电流升降调节，还没有在文献中被提出。the literature. The main difficulties in the design of a univers

18、al设计一个足够的灵活的发光二极管驱动应用在不同的接线配置最大的难题是振荡和电磁干扰问题。LED driver, flexible enough to be applied to different wiringconfigurations, are the ringing and EMI issues. These problems这些问题取决于环境因素和寄生组件，这些因素很难去假设和模仿。depend on environmental and parasitic components that are difficultto predict and simulate.While bulbs

19、 are easily modeled as而电灯泡却很容易模仿因为它有线性的正温度系数并且寄生成分对它的影响比较小。linear positive temperature coefficient (PTC) resistors, and areless sensitive to parasitic components, a LED is a special diode发光二极管是一种特殊的二极管，它满足肖克利指数电流-电压法。and follows the Shockley exponential IV law. A very smallfluctuation on the voltage

20、 across the LED can generate a very一个很小的电压起伏通过发光二极管可能引起一个很大的电流变化影响。high variation on its current affecting, as proved in 3, both efficiency经证明，效率和照明设备的寿命都将被影响。and life time and creating lighting disturbs. This behavior如果发光二极管没有恰当的被驱动的话这个行为会导致振荡和高强度的电流尖脉冲。can generate ringing and high current spikes

21、if the LED is not properly driven. By the same token, a bulb-designed driver, as出于同样的原因，灯泡的驱动，正如10-12中说的，不能被直接用于驱动发光二极管。shown in 1012, cannot be directly used to drive efficientlyLEDs. This is particularly true when the LED and the driver are这一点是完全正确的当发光二极管和驱动在汽车连接中被几米的电缆分割的时候。separated by a few met

22、er cables as in automotive connections.In this case, the wiring parasitics can generate ringing and EMI.出于这个原因，电线的寄生将引起振荡和电磁干扰。A comparison based on experimental measurements, between一个在二瓦特的灯泡和0.1瓦特的连着很短的线（大概10厘米长）发光二极管的比较实验中显示在图1和图2中。a 2-W bulb lamp and a 0.1-W LED turn-on transient with veryshort

23、wire (about 10 cm long) and with very long wire (about3m long) is shown, respectively, in Figs. 1 and 2. A simplerelay is used as a switch to highlight the different behavior一个简单的继电器被用来切换到这些负载不同的状态。of those loads. Those pictures show the necessity of using a这些图片展示了使用一个设计良好的LED驱动从而避免寄生电路的重要性。well-des

24、igned driver for LEDs, to avoid unwanted effects dueto wiring parasitics. In fact, the behavior of the current in the事实上，灯泡的电流状态不随着线的长度而变化。从图1a图2a可以看出bulb does not change significantly with the wire length seeFigs. 1(a) and 2(a) while the transient of the current in the而发光二极管的瞬间电流缺有显著的差异。从图1b和2b可以看出

25、LED shows significant differences see Figs. 1(b) and 2(b). Toovercome this issue we propose a compact solution, integrating为了解决这个问题我们计划了一个简洁的方案：in 0.35-mHVCMOStechnology the digital circuitry for driverinterfacing/configuration and power devices up to 10W, with采用高压CMOS技术数字电路的驱动程序，接口/配置和功率设备提高到10 瓦特H

26、V protection up to 55V. The LED driver can be interfaced to同时高压保护提高到55伏特。LED驱动可以被显示到数字电子控制单元，digital ECU 1315 and is able to cope with different wiring从而它可以处理各种长度的电线配置和寄生电路。configurations some meters long and their parasitics 2, and to使其适应作为线性稳压器和开关的表现，取决于编程的精度。adapt its behavior working as linear r

27、egulator or as a switchingone, depending on a programmable threshold.III. FLEXIBLE LED DRIVER IC三. 灵活的发光二极管驱动集成电路With respect to the bulb lamp driver shown in 11, 12 the关于指示灯驱动器了，智能LED驱动必须满足严酷的汽车环境约束。smart LED driver needs to fulfill the same harsh automotive environmentconstraints, as well as more

28、power demanding loads,同时也要满足更多的功率负载需求用于串联和并联配置下的发光二极管。as series and parallel configuration of LEDs. Low power LEDs,like those employed in the car dashboard, absorbing 3050mW,像那些30-50毫瓦的用于汽车仪表盘的低功率发光二极管，包括那些排列在一起的总功率到10瓦特的发光二极管或灯泡，能被提议的设计驱动。as well as arrays of power LEDs or lamps up to 10W, can bedr

29、iven properly by the proposed design. 图1.（a）灯泡（b）发光二极管 在没有任何电流电压控制的10厘米电缆下状态图2 （a）灯泡（b）发光二极管 在没有任何电流电压控制3厘米电缆下状态图3. 方案一允许的负载配置,加强了布线寄生现象,发光二极管,和串联的电池中的开关。图4.LED驱动集成电路的体系结构和详细电路The driving of LEDs has required the implementation of specific techniques to limit the undesired effects of wiring parasiti

30、cs, 发光二极管的驱动要求实施特定的技术来限制布线寄生现象带来的不良影响。such as ringing andconsequent overshoots and undershoots如振荡和随之引起的超调量和脉冲信号。.In Fig. 3, the scheme of the wiring parasitic and of a possible connection betweenthe driver and the load is shown: the output pin of the driver,在图三中，该计划的布线寄生和可能的在驱动和负载的连接中显示:输出的驱动程序，其功能可

31、以用一个简单的开关描述，是连接发光二极管，并且和汽车的whose functionality can be represented by a simple switch tothe ground, is connected to a LED, in series with the car batteryand another switch, controlled by the user through a button or电池和另外一个开关连接，而用户通过一个按钮或点火钥匙来控制它。the ignition key. The basic scheme of the flexible LED

32、driveris shown in Fig. 4, together with circuit details of the operational这个灵活的发光二极管驱动基本方案以及电路详细的步骤和跨导放大器块如图四所示。transconductance amplifier (OTA) block: the architecture这个设计基于一个is based on a voltage regulation loop inserted inside a linear loopproviding the current control capability.插入在一个线性循环的电压调节回路

33、以提供当前的控制能力。The voltage regulationloop forces the output on a reference voltage, Vref , when 电压调节回路控制输出的是参考电压当低压测主电源开关串联二极管以提供反极性的容量给装置，是开启了。the low side main power switch (power MOS in Fig. 4), in series withthe Diode that provides reverse polarity capability to the device,is turn ON. The LED driver

34、 has been integrated as hard macrocellLED驱动程序已经被集成在一个复杂的大容量的电池汽车控制单元集成电路中in a complex automotive control unit IC, implemented inAustria micro systems (AMS) 0.35 m CMOS technology. Fig 5被用在AMS0.35UM的互补金属氧化物半导体技术中。从图5中可以看出，shows the layout and the photo of the whole control unit IC,布局和图片的整个控制单元集成在电路中，

35、使得发光二极管驱动电子电路增强。highlighting the LED driver circuit, and particularly the powerMOS and its protection diode in Fig. 4, which occupy most ofthe LED driver area.特别的在图四中的MOS材料和二极管的保护，占绝了绝大部分的发光二极管驱动电路。By regulating the output voltage on a reference level the stateof the load and of the power switch can

36、 be easily detected.通过调节输出电压在一个参考电平状态的负载和电源开关可以很容易地被检测到。When the LED is ON (user switch and power switch in Fig. 3当发光二极管打开，（用开关或者图3的电源开关都可以使运转）both enabled), the regulation loop is activated and the output调节回路是激活的，输出电压是控制为参考电压的。Vo is forced on the reference voltage, Vref . If the user switch同时强制发光二极

37、管也关闭，如果关闭开关,因此发光二极管也关闭is OFF, and hence also the LED is OFF, the output pin of thedriver is pulled down even when the power switch is OFF, by输出引线驱动被损坏甚至电源总开关也关掉，意味着编的程序没有应变能力。means of a programmable resistive path to ground. That pathis highly resistive to limit to very low value the current flowing

38、through the LED. Finally, if the user switch is ON but the这条道路的高电阻是用来限制非常低的电流来通过发光二极管，如果用户开关打开但电源开关关闭，那么输出电压将强迫输出为电源的额定电压。power switch is forced OFF, then the output Vo is pulled up tothe battery voltage, Vbatt , and the LED is OFF since no noticeable发光二极管也将关闭直到没有明显的电流通过。current is flowing. Summariz

39、ing, depending on the statusof the switch devices in Fig. 3, the output voltage Vo can bepulled down to ground, or pulled up to Vbatt or forced to Vref .根据不同开关设备的状态，如图3所示,输出电压可以接地,或者强迫为电源的额定电压。A comparator can reveal the status of the driver and also potentialovervoltage conditions by comparing the

40、output voltageto proper thresholds. Similarly overcurrent and overtemperature一个比较器可以显示驱的状态和通过比较输出电压合适的阈值看出潜在的过压条件。phenomena can be detected by comparing the measured currentand temperature values (through an on-chip temperature sensor)with proper thresholds. All reference and threshold levels are同样的

41、过电流和超温现象是可以探测到的测量的电流和温度的值(通过一个芯片上的温度传感器)和适当的阈值比较。internally generated by a digital-programmable band-gap unit.所有的引用和阈值水平是由内部产生的数字通过可编程的带隙装置。The measurements shown in this letter are obtained with a Vref这篇文章中的测量值是通过额定电压获得，1.2伏特。of 1.2V. The detected driver and load status are used by theinternal logi

42、c as feedback signals to properly drive the powerMOS in Fig. 4, acting as linear regulator or ONOFF switch,检测到的驱动和负载状态使用内部逻辑作为反馈信号正确驱动动力在图四中的金属氧化物半导体,是作为线性调节器或开关and implementing advanced Soft Start or Current Slope Control techniques.和实施先进的软启动或电流升降控制技术The working mode of the LED driver, as linear re

43、gulator orONOFF switch, is determined by the user by proper configuringthe Current level Iref in Fig. 4. The MOSMA mirrors a small工作模式的LED驱动,线性调节器或通断开关,是由用户通过适当的配置在图4按图四的电流是水平。fraction of the power MOS output current and, through the HVand Low-Voltage (LV) current mirrors in Fig. 4, MOSMA反射小部分功率从MOS

44、输出电流,如图四通过高压和低压(LV)电流反射镜镜，compares it to the Iref current value (generated through on-chip band-gap circuit).比较其当前值(通过芯片上的带隙电路生成Iref)。The HV PMOS current mirror is connected to the outputvoltage, which is up to 12V, while the LV PMOS current mirroris connected to Vdd = 3.3V. The difference between I

45、mir and高压PMOS的电流反射连接到输出电压提高到12伏特,而低压PMOS电流反射连接到Vdd是3伏特。Iref drives the gate of MOS MB : if Imir is lower than Iref , thenImir和Iref之间的在MOS驱动上的区别是：如果Imir低于Irel，那么MB是关闭的MB is OFF and the power MOS, driven by the OTA in Fig. 4,并且MOS的能量是由如图四中的OTA驱动的，通过线性的电流调节器。acts as a linear current regulator. Otherwis

46、e, MB is ON and the反之，如果MB是打开的而电流环路控制开关关闭，那么MOS MB将会被强制关闭。current loop control switches to the OFF state the power MOS.The MOS MB can be forced back in OFF state, and hence the同时强制电源MOS起作用，如图四用来进行逻辑控制。powerMOS reactived, by the control logic in Fig. 4. The controllogic determines the times Ton and T

47、off when MB is OFF (i.e.,这个控制逻辑决定什么时候开什么时候关分别当MB关掉的时候（MOS开着）power MOS is ON) or MB is ON (i.e., power MOS is OFF), respectively.或者MB开着（MOS关闭）In this case, the driver is working in ONOFF switch因此，这个驱动工作在关或开的模式为了满足控制逻辑不停的变换开关。mode with duty cycle and frequency depending on the Ton andToff times set by

48、 the control logic.Summarizing, in linear regulator mode Iref is configured sothat the current loop control is activated only for output currentsof several amperes, much higher than the operating load currents总结,在线性调节器模式Iref是如此配置的为了电流环路控制输出电流只有安培。foreseen for this LED driver (see Section IV). In lin

49、ear mode,远高于操作负载电流的LED驱动程序(见第四部分)。在线性莫模型中，Iref acts as a protection threshold: if Imir is over Iref then MB isIref担当着一个保护的临界值：当Imir超过了Iref，那么MB会打开，电源MOS会关闭。switched ON and the power MOS is switched OFF.In ON/OFF switching mode, Iref is configured at levels lower在开/关模式下，Iref是按从低到高电流等级配置的。than normal

50、operating currents: the power MOS is no directlydriven by the OTA and the combined action of the current loopcontrol and of the control logic on the MOS MB determines theTon and Toff periods (and hence the switching duty cycle andfrequency) of the power MOS. To be noted that in switching电源MOS没有直接被OT

51、A和联合作用的电流环路控制。同时控制逻辑在MOS MB上决定了开或者关的周期(因此切换工作周期和频率)。mode Iref is not acting as the sole current limitation level; thedetection of overcurrent phenomena is carried out by the Over-I and Over-V detect block in Fig. 4. The described approach注意,在切换模式Iref不是作为唯一的电流限制水平;检测过流现象是被运用于过压过流检测块,如图4所示。allows to i

52、mplement two functions in the same LED driver IC atminimal hardware overhead: linear regulator mode, useful for所述方法可以实现两个功能相同的LED驱动集成电路在最小的硬件开销:线性稳压器，用于瞬间的变化和低电流低功率LED，当电源效率不是问题的时候。fast transient and low-current/low-power LEDs, where powerefficiency is not an issue; switch driving mode, useful for h

53、igher开关驱动方式，用于高电流和高功率LED，当电源效率是关键问题所以current and higher power LEDs where the power efficiency is akey issue and therefore a switching regulator has to be preferredto a linear one.线性的开关稳压器将被成为首选。The driving of a LED calls also for specific strategies toavoid the ringing phenomenon on the connecting w

54、ire withthe consequent current overshoot. The Soft Start and Current发光二极管的驱动也要求具体策略在连接线上避免振荡现象与随之产生的电流超调。Slope Control techniques, proposed by the authors in 12 forbulb lamp driving (low-power dashboard indicator), have beenimproved to maintain the same proper behavior also with arraysof LEDs and hi

55、gh luminosity up to 10W. The design has taken软启动和电流斜率控制技术,作者在12中提出的灯泡驱动(低功耗仪表板指示器),被用来保持适当的状态，同时也排列二极管把光度提高到10瓦特。into account the variability of parasitic capacitors and inductors,设计已经考虑到可变性的寄生电容和电感,as well as of the load and all process-voltage-temperature (PVT)以及负载和所有过程电压温度(PVT)的部分。corners. As sho

56、wn in Fig. 6, by sweeping through different如图六所示，通过不同的布线寄生现象和等效电阻对不同负载配置的发光二极管，values of the wiring parasitics and of the equivalent resistancefor different LED-based load configurations, the phase margin电压调节回路的相位补角,如图4所示，在一个相关的方式下变化。of the voltage regulation loop in Fig. 4 changes in a relevantway.

57、As a consequence, the susceptibility to instability of the overall因此，circuit varies, along with the entity of the ringing, as illustrated不稳定的磁感系数的整体电路的变化,随着实体振荡，在图7中阐述的那样。in Fig. 7. To deal with the wider range of possible values for theload, compared to the previous bulb case study 12, the Current处

58、理各种复杂的负载的可能值,相比前一个灯泡案例研究12,Slope Control, previously realized as a fixed technique, hasbeen tuned and made programmable through a digital interface.当前电流控制,先前意识到作为一个完善的技术,已经被调整好并通过数字接口使其可编程。The output current slope during the turn-on phase of the loaddepends on how fast that power MOS is switched ON.

59、 输出电流斜率在开机阶段的负载取决于MOS的开关开启的速度。Sincethe power MOS in Fig. 4 is driven by the output of the OTA, by因为操作系统的是由OTA的输出驱动的，如图4，controlling its slew rate it is possible to control the load currentslope. The slew rate of the OTA can be controlled by tuningthe dimensions of the transistors that compose the OT

60、A (fixedmode implemented in 12) or by regulating its bias current, Ibias通过斜率。转换速率可以控制通过调整控制它的转换速度,可以控制负载电流晶体管的尺寸组成OTA(固定模式实现在12)或通过调节其偏置电流。in Fig. 4, as done in this letter. Ibias is a configurable current在图四，像这文章中说的，偏置电流是一个可配置的电流所产生的一个芯片上的带隙电路。generated by an on-chip band-gap circuit. The programma

61、bilityof the Current Slope Control allows the employment of the smartdriver with different LEDs configuration, in order to keep downthe ringing.这个可编程的电流升降控制允许使用的智能与不同的发光二极管驱动配置,为了降低偏振。The supported switch driving mode is also useful to enablethe implementation of a Soft Start strategy against in-rus

62、h currentsthat can cause overshoots and ringing phenomena. When被支持的开关驱动方式也是用于启用实现软启动战略应对在高峰电流可引起超调量和偏振现象。the output current lasts over a configurable current limit formore than a configurable lapse of time, a Soft Start strategy is当输出电流持续超过一个可配置一段时间的电流限制时,一个软启动策略将被采用，adopted, switching the load by modulating the duty cycle and thefrequency (i.e., Ton and Toff ) parameters and hence controllingthe length of the turn-on phase.开关负载的调制周期频率频率(即T开和T关)参数,从而控制开机阶段的相位。As application example in Fig. 8, the time necessary to reachthe steady luminous state of a 10W