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为下一代电动汽车创建安全可靠的电路泰安

发布时间:2022-09-27 14:05:40

为下一代电动汽车创建安全可靠的电路

本文引用地址:article/202103/423865.htm

Fig.1.In hybrid-electric vehicle electrical architectures,the on-board charger must contend with the AC power line and its potential for generating overloads and transients.(Littelfuse)

图1 在混合动力电动汽车电气结构中,车载充电器必须与交流电源线及其可能产生的过载和瞬态过压相匹配。(Littelfuse) Desi插秧机gn considerations for building robust circuit protection in electrified and increasingly automated vehicles.

在电动化和自动化程度更高的车辆中建立可靠电路保护的设计注意事项。

Fig.2.On-board charger block diagram and recommended protection and control components.(Littelfuse)

图2 车载充电器框图和推荐的保护和功率控制器件。(Littelfuse)

Fig.3.TVS diode array for protection of CAN bus lines.(Littelfuse)

图3 用于保护CAN总线的TVS二极管阵列。(Littelfuse)

Designing circuits for electrified vehicles is extremely challenging.To ensure robust and safe designs that can withstand overloads,transients,and electrostatic discharge(ESD),designers need to ensure their circuits 模温机have the necessary components that will prevent damage.This article presents recommendations for both circuit protection and efficient control using the on-board charger as an example circuit.

为电动车辆设计电路极具挑战性。为了确保能够承受过载,瞬态和静电放电(ESD)的可靠和安全设计,设计人员需要确保其电路具有必要的器件以防止损坏。本文以车载充电器为例,提出了电路保护和高效功率控制的建议。

Hybrid vehicles,as seen in the Fig.1 schematic,represent the worst-case scenario for designers who must develop circuitry that can withstand transients from both the internal combustion engine and the high-power electric motors.In this environment,the on-board charger must contend with the AC power line and its potential for generating overloads and transients.

如图1示意图所示,对于必须开发能够承受来自内燃发动机和大功率电动机瞬变的电路设计人员而言,混合动力汽车代表了最坏的情况。在这种环境下,车载充电器必须与交流电源线及其可能产生的过载和瞬变相匹配。

Designers should protect the on-board charger just as they would protect any line-powered product.They also will want to protect communication circuits to avoid corruption of data while minimizing internal power consumption,so that battery charge time is as short as possible.

设计人员应该保护车载充电器,就像保护任何线路供电产品一样。他们还希望保护通信电路以避免数据损坏,同时将内部功耗降至最低,从而使电池充电时间尽可能短。

The on-board charger converts the AC line voltage into the DC voltage required for charging the main battery pack which,when fully charged,can contain voltage in the range of 300 to 500 V.Consumers want faster EV charging,thus the demand for higher-power charging circuits which can include 3-phase power.

车载充电器将交流线路电压转换为主电池组充电所需的直流电压,当电池充满时,主电池组的电压范围为300至500 V。消费者希望电动汽车充电更快,因此需要更高功率的充电电路,包括三相电源。

Fig.2 shows a block diagram of an on-board charger.In this example,a single-phase circuit is represented.Each circuit block requires protection components,and two blocks require control components to optimize the charger for efficiency.

图2显示了车载充电器的框纸成型机图。在此例子中,表示了一个单相电路。每个电路子框图都需要保护元件,两个电路子框图需要功率控制元件来优化充电器的效率。

MOVing to transient protection

转到瞬态保护

The input voltage section is susceptible to transients such as a lightning strike and surges on the AC line.The first line protection is a fuse to provide overload protection.Designers should consider fuses with a high interrupting current rating and a high voltage rating to ensure the fuse will open under the worst-case current overload.To protect against a surge transient or a lightning strike,designers should place a metal oxide varistor(MOV)as close to the input connections of the charger as possible.The MOV will absorb the transient energy and can prevent it from damaging the downstage circuit blocks.

输入电压部分容易受到瞬变的影响,如雷击和交流线路上的浪涌。第一种线路保护是提供过载保护的熔断器。设计人员应考虑具有高中断电流额定值和高电压额定值的保险丝,以确保保险丝在最坏的电流过载情况下断开。为了防止电涌瞬变或雷击,设计人员应将金属氧化物变阻器(MOV)放置在尽可能靠近充电器输入连接的位置。MOV将吸收瞬态能量,并可防止其损坏下游电路。

If the on-board charger uses 3-phase power,the designer should consider adding MOVs for phase-phase transient protection as well as phase-neutral transient protection.For even greater protection of downstream circuits,designers can place a bipolar thyristor in series with the MOV.A thyristor has a very low clamping voltage of around 5 V.Use of a thyristor allows a designer to select an MOV with a lower standoff voltage.The net effect is the reduction of the peak transient voltage to which the downstage circuitry is momentarily subjected.

如果车载充电器使用三相电源,则设计人员应考虑添加MOV进行相-相瞬态保护以及相-中性点瞬态保护。为了更好地保护下游电路,设计人员可以将半导体放电管与MOV串联。半导体放电管的箝位电压非常低,约为5 V。半导体放电管的使用允许设计者选择具有较低工作电压的MOV。好处是可以降低下游电路瞬间承受的峰值瞬态电压。

A fourth protection element for superior circuit protection is a gas discharge tube.The gas discharge tube provides high resistance,electrical isolation between the hot and neutral lines and the vehicle’s chassis ground.Gas discharge tubes provide an additional level of protection against fast-rising transients from lightning disturbances.

用于高级电路保护的第四种保护元件是气体放电管。气体放电管在火线和中性线与车辆底盘接地之间提供高电阻电气隔离。气体放电管可提供更高级别的保护,以防止雷电干扰引起的快速上升的瞬变。

IGBTs to the rescue

IGBT保护和控制

For fast,high power charging,designers should select rectifier block thyristors with sufficient current handling capacity to supply the necessary power.Thyristors also can absorb safely surge current transients that may have passed through the input voltage and EMI filter stages.

对于快速、大功率充电,设计者应选择具有足够电流处理能力的整流块晶闸管来提供必要的电源。晶闸管还可以安全地吸收可能通过输入电压和EMI滤波器级的浪涌电流瞬变。

The power factor correction(PFC)circuit improves the efficiency of the charge by reducing the total power drawn from the AC power line.Designers can use a gate driver and an insulated gate bipolar transistor(IGBT)to control the amount of inductance in the circuit.Designers should ensure that they select a gate driver with a sufficient operating voltage range for control of the IGBT.Designers also should consider selecting a gate driver with high immunity to latch-up and with fast rise-and-fall times to quickly switch the IGBT.

功率因数校正(PFC)电路通过降低从交流电源线吸取的总功率来提高充电效率。设计人员可以使用栅极驱动器和绝缘栅双极晶体管(IGBT)来控制电路中的电感量。设计人员应确保选择具有足够工作电压范围的栅极驱动器来控制IGBT。设计人员还应考虑选择一个具有高抗扰度的栅极驱动器来锁定,并具有快速上升和下降时间来快速切换IGBT。

Fast rise-and-fall times combined with a low supply current minimize power consumption of this circuit block.The gate driver should be protected from ESD;designers should either select a gate driver with built-in ESD protection or add an external ESD diode.Versions of ESD diodes can be either bi-directional or uni-directional and can withstand ESD transients as high as 30 kV.

快速上升和下降时间与较低的电源电流相结合,最大限度地降低了该电路块的功耗。栅极驱动器应提供防静电保护。设计人员应该选择具有内置ESD保护的栅极驱动器,或者添加一个外部ESD二极管。ESD二极管可以是双向的也可以是单向的,并且可以承受高达30 kV的ESD瞬变。

Know the key diodes

了解关键二极管

The DC link consists of the capacitor bank that stabilizes the ripple generated by the high-power DC/DC converter.Designers concerned about large voltage transients reaching the DC link can employ a high-voltage TVS diode to protect the capacitor bank.直流链路由电容器组组成,用于稳定大功率直流/直流变换器产生的纹波。担心到达直流链路的大电压瞬变的设计人员可以采用高压TVS二极管来保护电容器组。

The DC/DC section steps up the output charge voltage and generates the charge current for the battery.This circuit block requires a robust gate driver similar to the PFC circuit block.If a gate driver selection does not include internal ESD protection,designers can select an ESD diode to protect the gate driver.Addition of an external ESD diode does not degrade the performance of the gate driver.

直流/直流部分会提高输出充电电压,并为电池产生充电电流。该电路模块需要与PFC电路模块相似的可靠的栅极驱动器。如果栅极驱动器选择不包括内部ESD保护,则设计人员可以选择一个ESD二极管来保护栅极驱动器。添加外部ESD二极管不会降低栅极驱动器的性能。

Designers should also ensure that their power IGBTs are protected from voltage transients.In addition to protection from external transients,the IGBT creates turn-off switching transients due to L·di/dt effects from internal parasitic inductance(L being the inductance and di/dt the rate of current change).To eliminate the potential damage to an IGBT from this transient,designers should place a TVS diode between the collector and gate of each IGBT.

设计人员还应确保其电源IGBT免受电压瞬变的影响。除了防止外部瞬变,由于内部寄生电感的L·di/dt效应(L是电感,di/dt是电流变化率),IGBT还会产生关断开关瞬变。为了消除这种瞬态对IGBT的潜在损害,设计人员应该在每个IGBT的集电极和栅极之间放置一个TVS二极管。

The TVS diode reduces the di/dt of the current transient by raising the gate voltage.When the collector-emitter voltage exceeds the breakdown voltage of the TVS diode,current flows through the TVS diode into the gate to raise its potential.The TVS diode continues to conduct until the transient is eliminated.

TVS二极管通过提高栅极电压来降低电流瞬变的di/dt。当集电极-发射极电压超过TVS二极管的击穿电压时,电流通过TVS二极管流入栅极以提高其电势。TVS二极管继续导通,直到瞬态消除。

Use of a TVS diode as a collector-gate feedback element is known as active clamping and keeps the IGBT in a stable state.More information on active clamping is available in the referenced application note.1 Some IGBTs have built-in active clamping TVS diodes.Designers either should select that type of IGBT or add TVS diodes to their circuit.

使用TVS二极管作为集电极-栅极反馈元件被称为有源钳位,并可将IGBT保持在稳定状态。有关有源钳位的更多信息,请参阅参考应用说明1。一些IGBT具有内置有源钳位TVS二极管。设计人员应选择该类型的IGBT或在其电路中添加TVS二极管。

Protecting CAN bus signals

保护CAN总线信号

The output voltage stage requires protection from current overloads and in-vehicle voltage transients when motors turn on and off or when current is instantaneously interrupted by a break in a cable.Designers should consider employing a fuse to protect from an overcurrent resulting from a short in the battery pack or in the cables that carry the battery voltage.Use of an MOV or a TVS diode protects against the potentially damaging voltage transients.

当电机打开和关闭或电流因电缆断裂而瞬时中断时,输出电压侧需要提供保护,以防止电流过载和车内电压瞬变。设计人员应考虑使用熔断器,以防止因电池组或承载电池电压的电缆短路而引起的过电流。使用MOV或TVS二极管可防止潜在的破坏性电压瞬变。

The control unit for the charger communicates with the data network via the CAN bus.To avoid damage to the communication circuit block and avoid corruption of data,designers should provide ESD and transient protection.They can implement the protection with a single,space-saving component.Fig.3 shows a dual-line TVS diode array designed for protection of CAN bus signal lines.Diode arrays designed for protecting communication lines contain minimal capacitance and do not degrade the transmitter/receiver I/O states.

充电器的控制单元通过CAN总线与数据网络联系。为避免通信电路块和数据损坏,设计人员应提供ESD和瞬态保护。他们可以使用单个节省空间的元件来实现保护。图3显示了设计用于保护CAN总线信号线的双线TVS二极车刀管阵列。设计用于保护通信线路的二极管阵列包含较小的电容,并且不会降低发送器/接收器的I/O状态。

Designers who follow the recommendations for protection and control will have robust,reliable and safe circuits for their companies’EV customers.Whenever possible,designers should use AEC-Q qualified components that have been certified for use in the automotive environment.For example,AEC-Q101 covers discrete semiconductors,and AEC-Q200 covers passive components such as varistors.Furthermore,designers should consider taking advantage of the manufacturers’experts for assistance in selection of appropriate protection components.

遵循保护和功率控制建议的设计人员将为其公司的电动汽车客户提供可靠和安全的电路。设计人员应尽可能使用经AEC-Q认证且可在汽车环境中使用的合格元件。例如,AEC-Q101覆盖分立半导体,和AEC-Q200覆盖无源元件,如压敏电阻。此外,设计人员应考虑利用制造商的专家的帮助来选择合适的保护元件。

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