為下一代電動(dòng)汽車創(chuàng)建安全可靠的電路

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)

圖1 在混合動(dòng)力電動(dòng)汽車電氣結(jié)構(gòu)中，車載充電器必須與交流電源線及其可能產(chǎn)生的過載和瞬態(tài)過壓相匹配。（Littelfuse）　　       Design considerations for building robust circuit protection in electrified and increasingly automated vehicles.

　　在電動(dòng)化和自動(dòng)化程度更高的車輛中建立可靠電路保護(hù)的設(shè)計(jì)注意事項(xiàng)。

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

　　圖2 車載充電器框圖和推薦的保護(hù)和功率控制器件。(Littelfuse)

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

圖3 用于保護(hù)CAN總線的TVS二極管陣列。(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 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.

　　為電動(dòng)車輛設(shè)計(jì)電路極具挑戰(zhàn)性。為了確保能夠承受過載，瞬態(tài)和靜電放電（ESD）的可靠和安全設(shè)計(jì)，設(shè)計(jì)人員需要確保其電路具有必要的器件以防止損壞。本文以車載充電器為例，提出了電路保護(hù)和高效功率控制的建議。

　　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.

　　如圖1示意圖所示，對(duì)于必須開發(fā)能夠承受來自內(nèi)燃發(fā)動(dòng)機(jī)和大功率電動(dòng)機(jī)瞬變的電路設(shè)計(jì)人員而言，混合動(dòng)力汽車代表了最壞的情況。在這種環(huán)境下，車載充電器必須與交流電源線及其可能產(chǎn)生的過載和瞬變相匹配。

　　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.

　　設(shè)計(jì)人員應(yīng)該保護(hù)車載充電器，就像保護(hù)任何線路供電產(chǎn)品一樣。他們還希望保護(hù)通信電路以避免數(shù)據(jù)損壞，同時(shí)將內(nèi)部功耗降至最低，從而使電池充電時(shí)間盡可能短。

　　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.

　　車載充電器將交流線路電壓轉(zhuǎn)換為主電池組充電所需的直流電壓，當(dāng)電池充滿時(shí)，主電池組的電壓范圍為300至500 V。消費(fèi)者希望電動(dòng)汽車充電更快，因此需要更高功率的充電電路，包括三相電源。

　　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.

　　圖2顯示了車載充電器的框圖。在此例子中，表示了一個(gè)單相電路。每個(gè)電路子框圖都需要保護(hù)元件，兩個(gè)電路子框圖需要功率控制元件來優(yōu)化充電器的效率。

MOVing to transient protection

轉(zhuǎn)到瞬態(tài)保護(hù)

　　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.

　　輸入電壓部分容易受到瞬變的影響，如雷擊和交流線路上的浪涌。第一種線路保護(hù)是提供過載保護(hù)的熔斷器。設(shè)計(jì)人員應(yīng)考慮具有高中斷電流額定值和高電壓額定值的保險(xiǎn)絲，以確保保險(xiǎn)絲在最壞的電流過載情況下斷開。為了防止電涌瞬變或雷擊，設(shè)計(jì)人員應(yīng)將金屬氧化物變阻器（MOV）放置在盡可能靠近充電器輸入連接的位置。MOV將吸收瞬態(tài)能量，并可防止其損壞下游電路。

　　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.

　　如果車載充電器使用三相電源，則設(shè)計(jì)人員應(yīng)考慮添加MOV進(jìn)行相-相瞬態(tài)保護(hù)以及相-中性點(diǎn)瞬態(tài)保護(hù)。為了更好地保護(hù)下游電路，設(shè)計(jì)人員可以將半導(dǎo)體放電管與MOV串聯(lián)。半導(dǎo)體放電管的箝位電壓非常低，約為5 V。半導(dǎo)體放電管的使用允許設(shè)計(jì)者選擇具有較低工作電壓的MOV。好處是可以降低下游電路瞬間承受的峰值瞬態(tài)電壓。

　　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.

　　用于高級(jí)電路保護(hù)的第四種保護(hù)元件是氣體放電管。氣體放電管在火線和中性線與車輛底盤接地之間提供高電阻電氣隔離。氣體放電管可提供更高級(jí)別的保護(hù)，以防止雷電干擾引起的快速上升的瞬變。

IGBTs to the rescue

IGBT保護(hù)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.

　　對(duì)于快速、大功率充電，設(shè)計(jì)者應(yīng)選擇具有足夠電流處理能力的整流塊晶閘管來提供必要的電源。晶閘管還可以安全地吸收可能通過輸入電壓和EMI濾波器級(jí)的浪涌電流瞬變。

　　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.

　　功率因數(shù)校正（PFC）電路通過降低從交流電源線吸取的總功率來提高充電效率。設(shè)計(jì)人員可以使用柵極驅(qū)動(dòng)器和絕緣柵雙極晶體管（IGBT）來控制電路中的電感量。設(shè)計(jì)人員應(yīng)確保選擇具有足夠工作電壓范圍的柵極驅(qū)動(dòng)器來控制IGBT。設(shè)計(jì)人員還應(yīng)考慮選擇一個(gè)具有高抗擾度的柵極驅(qū)動(dòng)器來鎖定，并具有快速上升和下降時(shí)間來快速切換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.

　　快速上升和下降時(shí)間與較低的電源電流相結(jié)合，最大限度地降低了該電路塊的功耗。柵極驅(qū)動(dòng)器應(yīng)提供防靜電保護(hù)。設(shè)計(jì)人員應(yīng)該選擇具有內(nèi)置ESD保護(hù)的柵極驅(qū)動(dòng)器，或者添加一個(gè)外部ESD二極管。ESD二極管可以是雙向的也可以是單向的，并且可以承受高達(dá)30 kV的ESD瞬變。

Know the key diodes

了解關(guān)鍵二極管

　　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.直流鏈路由電容器組組成，用于穩(wěn)定大功率直流/直流變換器產(chǎn)生的紋波。擔(dān)心到達(dá)直流鏈路的大電壓瞬變的設(shè)計(jì)人員可以采用高壓TVS二極管來保護(hù)電容器組。

　　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/直流部分會(huì)提高輸出充電電壓，并為電池產(chǎn)生充電電流。該電路模塊需要與PFC電路模塊相似的可靠的柵極驅(qū)動(dòng)器。如果柵極驅(qū)動(dòng)器選擇不包括內(nèi)部ESD保護(hù)，則設(shè)計(jì)人員可以選擇一個(gè)ESD二極管來保護(hù)柵極驅(qū)動(dòng)器。添加外部ESD二極管不會(huì)降低柵極驅(qū)動(dòng)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.

　　設(shè)計(jì)人員還應(yīng)確保其電源IGBT免受電壓瞬變的影響。除了防止外部瞬變，由于內(nèi)部寄生電感的L·di/dt效應(yīng)（L是電感，di/dt是電流變化率），IGBT還會(huì)產(chǎn)生關(guān)斷開關(guān)瞬變。為了消除這種瞬態(tài)對(duì)IGBT的潛在損害，設(shè)計(jì)人員應(yīng)該在每個(gè)IGBT的集電極和柵極之間放置一個(gè)TVS二極管。

　　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二極管通過提高柵極電壓來降低電流瞬變的di/dt。當(dāng)集電極-發(fā)射極電壓超過TVS二極管的擊穿電壓時(shí)，電流通過TVS二極管流入柵極以提高其電勢(shì)。TVS二極管繼續(xù)導(dǎo)通，直到瞬態(tài)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二極管作為集電極-柵極反饋元件被稱為有源鉗位，并可將IGBT保持在穩(wěn)定狀態(tài)。有關(guān)有源鉗位的更多信息，請(qǐng)參閱參考應(yīng)用說明1。一些IGBT具有內(nèi)置有源鉗位TVS二極管。設(shè)計(jì)人員應(yīng)選擇該類型的IGBT或在其電路中添加TVS二極管。

Protecting CAN bus signals

保護(hù)CAN總線信號(hào)

　　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.

　　當(dāng)電機(jī)打開和關(guān)閉或電流因電纜斷裂而瞬時(shí)中斷時(shí)，輸出電壓側(cè)需要提供保護(hù)，以防止電流過載和車內(nèi)電壓瞬變。設(shè)計(jì)人員應(yīng)考慮使用熔斷器，以防止因電池組或承載電池電壓的電纜短路而引起的過電流。使用MOV或TVS二極管可防止?jié)撛诘钠茐男噪妷核沧儭?/p>

　　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.

　　充電器的控制單元通過CAN總線與數(shù)據(jù)網(wǎng)絡(luò)聯(lián)系。為避免通信電路塊和數(shù)據(jù)損壞，設(shè)計(jì)人員應(yīng)提供ESD和瞬態(tài)保護(hù)。他們可以使用單個(gè)節(jié)省空間的元件來實(shí)現(xiàn)保護(hù)。圖3顯示了設(shè)計(jì)用于保護(hù)CAN總線信號(hào)線的雙線TVS二極管陣列。設(shè)計(jì)用于保護(hù)通信線路的二極管陣列包含較小的電容，并且不會(huì)降低發(fā)送器/接收器的I/O狀態(tài)。

　　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.

　　遵循保護(hù)和功率控制建議的設(shè)計(jì)人員將為其公司的電動(dòng)汽車客戶提供可靠和安全的電路。設(shè)計(jì)人員應(yīng)盡可能使用經(jīng)AEC-Q認(rèn)證且可在汽車環(huán)境中使用的合格元件。例如，AEC-Q101覆蓋分立半導(dǎo)體，和AEC-Q200覆蓋無源元件，如壓敏電阻。此外，設(shè)計(jì)人員應(yīng)考慮利用制造商的專家的幫助來選擇合適的保護(hù)元件。