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保护自动驾驶汽车(AV)控制电路

作者:​Jim Colby时间:2021-03-24来源:收藏

  The mission-critical subsystems must be robust and reliable to ensure driver and passenger safety.

本文引用地址:http://www.eepw.com.cn/article/202103/423856.htm

  关键任务子系统必须高可靠性,以确保驾驶员和乘客安全。

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Circuit blocks in an AV camera subsystems(Fig.2).The camera power supply subsystem requires protection from overcurrents,high energy transients,and ESD.(Littelfuse)

AV摄像机子系统中的电路块(图2)。摄像机电源子系统需要保护以防止过电流,高能量瞬变和静电放电。(Littelfuse)

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A two-channel diode array protects both the high and low lines of a CAN transceiver(Fig.3).(Littelfuse)

双通道二极管阵列保护CAN收发器线路(图3)。(Littelfuse)

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Figure 4.Recommended ESD protection for an Ethernet transceiver

  图4.以太网收发器的推荐ESD保护

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The radar subsystem circuit has both low-noise and conventional DC power supplies(Fig.5)(Littelfuse)

雷达子系统电路同时具有低噪声和常规直流电源(图5)(Littelfuse)

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TVS and Schottky diodes give the ADAS communication/control circuit power-surge and reverse-polarity protection(Fig.6)(Littelfuse)

TVS和肖特基二极管为ADAS通信/控制电路提供浪涌和反极性保护(图6)(Littelfuse)

  The safety and convenience offered by autonomous vehicles(AVs)cannot be achieved unless the vehicle’s electronic circuits are highly reliable and robust to electrical shocks.Designers can substantially reduce the risk of circuit failures by providing overcurrent protection,transient surge protection,electrostatic discharge(ESD)protection,and reverse polarity protection.Strategies for circuit protection should begin with three mission-critical AV subsystems:camera,radar,and ADAS.

  除非车辆的电子电路具有高度的可靠性和抗电冲击能力,否则(AV)所提供的安全性和便利性无法实现。通过提供过电流保护,瞬态浪涌保护,静电放电(ESD)保护和反极性保护,设计人员可以大大降低电路故障的风险。电路保护的策略应从三个关键任务的AV子系统开始:摄像机,雷达和ADAS。

Protecting the camera subsystem

保护摄像机子系统

  In AVs,multiple cameras provide essential forward and backward vision,and work together to provide depth perception and convert visual light through a CCD/CMOS(charge coupled device/complementary metal-oxide semiconductor)image sensor into electronic signals sent to a communication and control circuit.The circuit blocks in a camera subsystem are shown in Fig.2.The key blocks that require protection components are the blocks that connect with external circuitry.

  在中,多个摄像机提供基本的前向和后向视觉,共同提供深度感知,并通过CCD/CMOS(电荷耦合器件/互补金属氧化物半导体)图像传感器将可见光转换为发送到通信和控制电路的电子信号。图2显示了摄像机子系统中的电路块。需要保护元件的关键模块是与外部电路连接的模块。

  The camera power supply subsystem requires protection from three potential sources of damage:overcurrents,high energy transients,and ESD.A fuse provides overcurrent protection.Designers can select either a conventional one-time-blow ceramic fuse or a polymer-based,positive temperature coefficient(PPTC)resettable fuse.Both components can have wide temperature ratings for automotive requirements.

  摄像机电源子系统需要防止三种潜在的损坏来源:过电流、高能量瞬变和静电放电。熔断器提供过电流保护。设计人员可以选择传统的一次性陶瓷熔断器或聚合物正温度系数(PPTC)可复位熔断器。两种元件均可满足汽车要求的宽温度额定值。

  The PPTC has the advantage of not needing replacement if an overcurrent condition occurs.This specialized fuse substantially increases in resistance in response to the heat generated by an overcurrent.When the overcurrent is removed,the PPTC recovers to a low resistance and resets the circuit.Both component types have surface-mount packages to save valuable PC board space.

  PPTC具有在发生过电流的情况下不需要更换的优点。这种专用熔断器在响应过电流产生的热量时,电阻会显著增加。消除过电流后,PPTC恢复到低电阻并重置电路。这两种元件类型都有表面贴装封装,以节省宝贵的PC板空间。

  Besides overcurrents,power supply circuits need protection from high energy transients caused by in-vehicle sources such as motors energizing and de-energizing.The circuitry must be capable of withstanding transients defined by ISO Standards 7637 and 16750.Compliant components include transient voltage suppressor(TVS)diodes,which can safely absorb both low-energy transients and high-energy transients as specified in Pulses 1,2,3 and 5 in the above-referenced standards.

  除了过电流外,电源电路还需要保护,以防车内电源(如电机通电和断电)引起的高能、能量瞬变。电路必须能够承受ISO标准7637和16750定义的瞬变。兼容元件包括瞬态电压抑制器(TVS)二极管,它可以安全地吸收上述参考标准中脉冲1、2、3和5中规定的低能量瞬态和高能量瞬态。

Transceiver solutions

收发器解决方案

  To avoid catastrophic failure if the polarity of the voltage to the power supply is accidently reversed,designers can insert a Schottky diode in series with the fuse.While providing reverse polarity protection,the diode’s low forward voltage drop will have a minimal impact on power supply performance.

  为避免电源电压极性意外反转时发生灾难性故障,设计人员可以让保险丝串联一个肖特基二极管。在提供反极性保护的同时,二极管的低正向电压降对电源性能的影响最小。

  The Controller Area Network(CAN)protocol transceiver needs protection from ESD,fast electrical transients,and other overvoltage transients.Diode arrays have high ESD robustness with models having 30-kV air and 30-kV contact discharge capabilities.These devices are used to help designers meet the ISO 10605 standard for ESD in road vehicles.Furthermore,with the capacitance of about 15 pF and leakage current under 1µA,the diode arrays do not interfere with protocol transmissions.These devices also survive the automotive environment with a temperature operating range of-40°C to+150°C.

  控制器局域网(CAN)协议收发器需要针对静电放电,快速电气瞬变和其它过电压瞬变的保护。二极管阵列具有较高的静电放电可靠性,其模型具有30 kV空气和30 kV接触放电能力。这些器件用于帮助设计人员满足道路车辆静电放电的ISO 10605标准。此外,二极管阵列的电容约为15 pF,漏电流低于1µA,因此不会干扰协议传输。这些器件还可以在-40°C至+150°C的温度范围内工作,以适应汽车环境。

  The recommended circuit for protecting a CAN transceiver is shown in Fig.3.A two-channel diode array protects both the high and low lines.A single protection component helps to reduce pick-and-place costs in production.The Ethernet transceiver,like the CAN transceiver,needs ESD protection.Diode arrays and polymer ESD suppressors can provide the necessary protection for the high-speed differential data lines.Models of these diode arrays can provide up to±30 kV ESD protection and can protect a differential line pair in a single package for space savings.An 0402 version is also available as a discrete component to allow for the PC board layout flexibility.

  保护CAN收发器的推荐电路如图3所示。两通道二极管阵列可以保护CAN总线2根数据线。单个保护元件有助于降低生产中的取放成本。像CAN收发器一样,以太网收发器也需要ESD保护。二极管阵列和聚合物ESD抑制器可为高速差分数据线提供必要的保护。这些二极管阵列的型号可以提供高达±30 kV的ESD保护,并可以在单个封装中保护差分线对以节省空间。0402版本也可作为分立元件提供,以实现PC电路板布局的灵活性。

  In systems where the capacitance must be absolutely the lowest,the polymer ESD suppressor(AXGD1 series)with 0.04pF can be considered.With capacitance this low,it does not impede 1-Gbit Ethernet transmission rates.An example of the configuration and component that is consistent with recommendations from the OPEN Alliance Ethernet organization is shown in Fig.4.

  在结电容必须是绝对最低的系统中,可以考虑使用0.04pF的聚合物静电抑制器(AXGD1系列)。在电容如此低的情况下,它不会阻碍1千兆位以太网的传输速率。图4中显示了与OPEN Alliance以太网组织的建议相一致的配置和元件的示例。

  The most important circuit block is the image sensor block–a bipolar,low-capacitance protection component.This diode can withstand an ESD strike of up to±30 kV and has extremely low leakage current(typical values of under 10 nA)and capacitance around 0.35 pF.For space efficiency,this ESD diode is available in an ultra-small,1.0-mm x 0.5-mm SOD882 package.

  最重要的电路模块是图像传感器模块,需要一种双极性低电容保护元件。该二极管可承受高达±30kV的ESD冲击,具有极低的泄漏电流(典型值低于10nA)和约0.35pF的电容。为了节省空间,这种ESD二极管采用1.0 mm x 0.5 mm的超小型SOD882封装。

  Protecting the camera subsystem’s four circuit blocks that interface with external circuitry and the external environment will ensure a robust,reliable,visible light detection system.Using the recommended components as close as possible to the circuit inputs will keep extraneous energy from damaging critical circuits.

  保护摄像机子系统与外部电路和外部环境相连接的四个电路模块将确保一个强大、可靠的可见光探测系统。尽可能靠近电路输入端使用推荐的元件将防止外来能量损坏关键电路。

Protecting the radar subsystem

保护雷达子系统

  The radar subsystem provides the input for the important forward and side pedestrian detection and collision-avoidance functions.As shown in the Fig.5 block diagram,the radar subsystem circuit has two DC power supplies.A low-noise supply powers the analog radar transmitter and the radar receiver circuit blocks.A conventional power supply powers the logic and communication circuits.Like the camera subsystem power supply,the radar subsystem power supplies need overcurrent protection,transient surge protection,reverse polarity,and ESD protection.

  雷达子系统为重要的前方和侧面行人检测和避撞功能提供输入。如图5所示,雷达子系统电路有两个直流电源。低噪声电源为模拟雷达发射机和雷达接收机电路模块供电。传统电源为逻辑和通信电路供电。与摄像机子系统电源一样,雷达子系统电源也需要过电流保护、瞬态浪涌保护、反极性保护和ESD保护。

  One set of components can protect both supplies from overcurrents and reverse polarity.Again,the designer can select from either a conventional surface-mount fuse or a PPTC resettable fuse.A low forward voltage,Schottky diode,in series with the input line to both supplies will provide reverse polarity protection for the power supplies and for all the radar subsystem circuit blocks.Designers should provide individual supplies with surge protection at the input to each supply.

  一组元件可以保护两个电源免受过电流和反极性的影响。同样,设计者可以从传统的表面贴装保险丝或PPTC可复位保险丝中进行选择。低正向电压肖特基二极管与两个电源的输入线串联,将为电源和所有雷达子系统电路块提供反极性保护。设计人员应在每个电源的输入端为每个电源提供浪涌保护。

  TVS diodes are the recommended surge protection component.Designers choose the TVS diode based on its transient power rating(400W/600W for low power transients and 1,500W to 7,000W for high power transients)to protect the power supplies.The waveform generator and the analog front-end are part of the radar transmitter and radar receiver,respectively.They are separated from the transmitter and receiver blocks(in Fig.5)since the addition of protection components on the transmitter output and receiver input blocks would alter their transmission and reception impedance.The protection components safeguard as much of the circuits as possible.

  建议使用TVS二极管作为浪涌保护元件。设计人员根据TVS二极管的瞬时额定功率(400W/600W适用于低功率瞬变,1500 W至7000W适用于高功率瞬变)选择TVS二极管来保护电源。波形发生器和模拟前端分别是雷达发射机和雷达接收机的一部分。它们与发射器和接收器模块(在图5中)分开,因为在发射器输出和接收器输入模块上添加保护元件会改变它们的传输和接收阻抗。保护元件可以保护尽可能多的电路。

  A bipolar component similar to the ESD diode recommended for the image sensor in the camera subsystem will provide the necessary ESD protection.As with the camera subsystem,the radar subsystem transmits its information to the vehicle’s central processing subsystem.Bipolar diode arrays provide ESD protection for both the high and low side of CAN I/O lines.The Ethernet transceiver can use either diode arrays or polymer ESD suppressors to minimize signal distortion and not impact the Ethernet transmission rate.

  与摄像机子系统中推荐用于图像传感器的ESD二极管类似的双极性元件将提供必要的ESD保护。与摄像机子系统一样,雷达子系统将其信息传输到车辆的中央处理子系统。双极二极管阵列为CAN I/O线的高侧和低侧均提供ESD保护。以太网收发器可以使用二极管阵列或聚合物ESD抑制器来最大程度地减少信号失真,并且不会影响以太网传输速率。

Protecting ADAS communication and control

保护ADAS通信和控制

  The signal processing,communication,and control subsystem(Fig.6)operate the vehicle.It must be robust,reliable,and failsafe.The circuit must identify other vehicles in traffic,may need to make fast stops due to an animal or person obstructing the vehicle’s path,and needs to have a fail-safe response to a failed sensor.Failsafe firmware is critical but so is hardware that is capable of surviving transient energy strikes.All the circuit blocks that supply information to the controller need protection from ESD.

  信号处理,通信和控制子系统(图6)操作车辆。它必须是高可靠性的和无故障的。该电路必须识别出正在行驶的其它车辆,可能由于动物或人挡住车辆的路径而需要快速停车,并且需要对故障传感器做出故障安全响应。故障安全固件至关重要,但能够承受瞬态能量冲击的硬件也至关重要。向控制器提供信息的所有电路模块都需要防静电放电保护。

  The power supply requires overcurrent protection,surge protection,and reverse polarity protection.The fuse for this supply can be located within the module or further upstream in the vehicle’s low voltage junction box.A TVS diode,selected by its surge power rating,provides the necessary surge transient protection.A Schottky diode in series with the power supply input line provides reverse voltage polarity protection.

  电源需要过电流保护、浪涌保护和反极性保护。该电源的熔断器可以位于模块内,也可以位于车辆上游的低压接线盒。通过浪涌功率额定值选择的TVS二极管可提供必要的浪涌瞬变保护。与电源输入线串联的肖特基二极管可提供反向电压极性保护。

  Each communication link requires ESD protection that is designed for the unique performance and configuration of each port.The table below lists the communication protocols used in the ADAS communication and control subsystem and their different data rates.Designers can select from a wide range of diode arrays and polymer ESD suppressors with unique characteristics to protect each communication link without compromising its data rate or its high-to-low voltage differential.

  每条通信链路都需要针对每个端口的独特性能和配置而设计的ESD保护。下表列出了ADAS通信和控制子系统中使用的通信协议及其不同的数据速率。设计人员可以从各种具有独特特性的二极管阵列和聚合物ESD抑制器中进行选择,以保护每条通信链路,而不会影响其数据速率或其高至低电压差。

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  Any signal lines connecting directly to the DSP circuit block should have ESD protection.Designers can use diode arrays or polymer ESD suppressors that provide bipolar protection for both the high and low signal lines.Designers have a broad range of components that they can use to protect circuitry from the potential stresses noted above.Reliance on AEC-Q qualified components can both accelerate compliance with standards certification bodies while giving the designer confidence that the components will provide the necessary level of protection.

  任何直接连接到DSP电路模块的信号线都应具有ESD保护。设计人员可以使用二极管阵列或聚合物ESD抑制器,为差分信号线提供双极保护。设计人员有多种元器件可用来保护电路免受上述潜在应力的影响。依靠AEC-Q合格元件既可以加速符合认证机构的标准,又能让设计人员确信元件将提供必要的保护级别。



关键词: 自动驾驶汽车

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