Common Driver Platform for 12V and 48V Systems Simplifies EV Starter Generator Designs

Common Driver Platform for 12V and 48V Systems Simplifies EV Starter Generator Designs

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介绍

Belt-driven starter generators are an integral part of hybrid electric vehicle (HEV) and electric vehicle (EV) systems as they help reduce carbon emissions generated by internal combustion engines. Starter generator systems play multiple roles in electrified vehicle architectures. They are responsible for starting the engine, supplying electrical boost to the engine, and generating charge voltage during deceleration or coasting, which reduces wear on mechanical braking systems while improving overall system efficiency.

无论它们的架构还是所在的位置,都已经证明了Starter Generator Systems是车辆电气化的一个组成部分。起动发生器可用于车辆内的多个位置。图1显示了主起动发生器系统的位置。P0和P1位置通常小于20 kW。P0系统正变得非常普遍,因为它们是最容易实现的,需要更少的重新设计并且具有成本效益。P1位置具有类似的益处,同时消除皮带损耗,从而产生更高的性能和更少的磨损。

图1:带电车辆中的起动发生器和EBOOST位置。

Starter Generator Circuit Implementations

起动发生器系统由多种电气和机械部件组成。逆变器提供电气升压和DC-DC转换器,以将转子中的机械能转换为能量收集模式的电能。该系统还负责怠速停止系统中的曲柄位置以及冷启动所需的高启动扭矩。机械地,起动发生器包括定子,该定子连接到三相逆变器,转子通过通过滑环和刷子通过转子绕组通过转子绕组来产生场。使用永磁机的新设计可以消除对现场线圈的需求,但这种方法呈现出其他安全挑战,因为在故障情况下不能关闭磁化。图2显示了五相机的典型电路实现。

图2:五相启动器发生器的示例。

用于12V和48V系统的公共驱动器,电流传感器和电机位置角度传感器解决方案

Belt-driven starter generator (BSG) systems are used on both 12V and 48V power rails. A 12V BSG system is not able to provide the same power advantage as a 48V starter generator. Typically, the 12V systems are limited to < 10 kW while 48V systems can generate up to 25 kW or more. As power increases, so do the demands on the gate drivers, as well as the current sensors. For P0/P1 locations, it is advantageous to use a common architecture for both 12V and 48V batteries with minimal additional components or redesign required. Using a common architecture reduces design time and bill-of-material (BOM) cost and enables a single platform for bolt-on BSG systems in both 12V and 48V systems.

TheAMT49502Allegro Microsystems的半桥门驱动器可以亚博棋牌游戏从5.5 V到80 V操作,使其成为在12V轨或48V轨上运行的BSG应用程序的多功能平台。亚博尊贵会员该器件的电荷泵调节器为两个N通道MOSFET提供栅极驱动器。图3显示了半桥设计的功能框图。只需要单个电源,所有内部逻辑都由由电荷泵调节器提供动力的片上逻辑供应稳压器。The regulator is responsible for providing regulated 11 V to the floating bootstrap capacitor, which ensures the high-side MOSFET has 11 V on the gate with a battery voltage of 5.5 V. The charge pump regulator also supplies the internal logic, which reduces the chip’s overall power dissipation. Minimizing power consumption is key to operating at 48V without requiring buck regulation. In addition, a small integrated charge pump is responsible for holding the high-side switch on at 100 percent duty cycle.

Allegro also offers a wide range of options for current sensing, which all have similar analog interfaces that can be fed back to a microprocessor, allowing for full field-oriented control (FOC) with redundancy. For lower power systems, the AMT49502 has an integrated, high-performance current sense amplifier that measures current through a low-side current shunt. As the power increases, Hall-effect-based current sensors provide much lower power dissipation and smaller size than the necessary shunt resistor. Their galvanic isolation also means they can be placed on the high side, low side, or in phase, providing flexibility at the system level for both control and short-circuit detection. For the typical currents seen in the rotor coils, Allegro’s integrated conductorACS71240提供精确,高效,小的解决方案。对于在电机阶段看到的更高的电流,最常见的解决方案是ACS70310 / 1在C核心内或ACS37612 / 10.无芯解决方案。所有这些解决方案都提供了冗余的手段,以及内置诊断。ACS71240和ACS37610都提供内置过电流检测,ACS37610提供过温度检测。AMT49502中的每个MOSFET可以使用逻辑输入和辅助启用输入独立控制,该输入提供独立的路径以禁用桥梁或激活睡眠模式。然后,串行外围接口(SPI)端口可用于读出诊断并设置功能参数。

Further supporting starter generator designs, Allegro offers a complete portfolio of magnetic angle sensors for a wide variety of motor position sensing applications. The high-resolutionA1333AAS33001angle sensors provide rotational motor position information which can be used as part of a sinusoidal commutation motor control scheme. This type of motor control scheme brings high efficiency and improved torque performance to the starter generator. Additionally, Allegro can also support traditional block commutation motor control approaches with a full magnetic Hall sensors portfolio.

Overall, a BSG designed using the AMT49502, Allegro current sensor ICs, and motor position sensors can work for both 12V and 48V systems and be easily scaled for power.

Figure 3: Functional block diagram for the AMT49502 gate driver.

Designed for Demanding Environments

起动器发生器系统可以在逆变器桥上产生高电压。当在发电机模式下时,逆变器的目的是将三相电流转换为直流电压和电流,可以应用于12V或48V电池系统作为充电。最终,电动机产生的电压基于转速。逆变器桥对高速旋转期间存在的电压瞬变以及驱动器和发电机模式的过渡期间非常重要。栅极驱动器必须足够强大,以处理系统中存在的高电流和电压瞬变。通过设计栅极驱动程序来存活这些瞬变,开发人员可以节省宝贵的设计时间并最大限度地减少添加高压夹具以保护系统的额外成本。当高侧MOSFET在发电机模式下关闭时,桥上的电压瞬变可以在低端驱动器上产生超过5V的负电压,相位节点上的10 V超过10V。

AMT49502栅极驱动器可以在高侧栅极和-18V上相对于相位节点存活-8V,如图4所示。确保即使是高功率系统也不会损坏变频器。EV组件必须足够强大,以处理负电压瞬变并通过制造商的电磁排放要求。起动发生器逆变器需要快速切换以保持效率,同时提供最佳排放量。它们还必须限制电磁排放的大小,以满足严格的OEM要求。

为了满足高效率和低电磁排放之间的权衡,AMT49502驱动器具有分段可编程电流栅极驱动拓扑,允许系统中所有MOSFET的控制接通和关闭。MOSFET离线到ON和开关过渡如图5所示。通过SPI端口编程所有参数。

Figure 4: Typical transient performance for a 48V architecture.

当栅极驱动器被命令打开时,电流,i1, is sourced on the high-side or low-side gate terminal for a duration, t1。这些参数通常应设置为quickly charge the MOSFET input capacitance to the start of the Miller region as drain-source voltage does not change during this period. Thereafter, the current sourced on GH or GL is set to a value of I2并且在MOSFET通过米勒区域转换并达到完全达到状态的同时保持该值。

图5:描绘了可编程分段栅极驱动器。

MOSFET on-to-off transitions are controlled as shown in Figure 5. When a gate drive is commanded to turn off, a current, I1,由高端或低侧门终端沉入持续时间,t1。These parameters should typically be set to quickly discharge the MOSFET input capacitance to the start of the Miller region as drain-source voltage does not change during this period. Thereafter, the current sunk by the high-side or low-side gate terminal is set to a value of I2和remains at this value while the MOSFET transitions through the Miller region and reaches the fully off state.

Full control of MOSFET switching increases efficiency and reduces EMI. Reducing deadtime and the time required for the MOSFET to reach its Vt enhances inverter performance by minimizing the time for high-side and low-side MOSFET switching and improves the fidelity of the sinusoidal current. Programmable current during the Miller region controls the MOSFET slew, which limits emissions while maintaining efficient switching times.

Allegro’sAMT49100three-phase gate driver with ASIL D certification is available for purely 48V systems. Using a three-phase driver onboard shrinks package content, enabling even smaller system designs. The AMT49100 offers additional diagnostics and the ability to verify each diagnostic with built-in test circuitry. For single-driver designs, this additional diagnostic and verification function provides a level of functional safety that can notify the engine control unit (ECU) of a variety of failures.

Some 48V designs may benefit from ultra-small gate drivers. For example, the 10 to 100 VA89500.half-bridge gate driver in a 3 mm × 3 mm DFN package is so small, it can reduce overall printed circuit board (PCB) space. The device can be used in a field coil drive, as well as the inverter with proper safety analysis. The driver is suppled directly with an 8 to 13 V gate supply, and the field effect transistor (FET) bridge connects directly to a 48V battery. See block Figure 6 for details.

图6:A89500栅极驱动器功能框图和包装。

Designed for Safety

Starter generator failures can result in overcharge of the lithium-ion battery pack, which can be dangerous should cells short. Therefore, starter generator circuits must comply with the ISO 26262 standard, typically requiring a “B” level certification. For example, a failure in the inverter bridge while the generator is still spinning at high speed can cause overcharge condition. In a five-phase system, one solution is to effectively remove the magnetic field on the rotor by disabling the field coil driver. In this implementation, the design is paramount to developing a failsafe system. The gate drivers in this system can make the requirement easier to achieve if they are designed for safety. The AMT49502, for example, was designed on an ISO 26262-certified development process, and the device is certified as ASIL B compliant.

Featuring a suite of advanced diagnostics, each half-bridge driver contains nearly twenty diagnostic functions, including load dump detection, MOSFET short-circuit protection, gate drive undervoltage, bridge supply overvoltage, temperature warning, and other conditions. IC diagnostics provide the system controller with necessary information to monitor operation and make decisions on actions taken by the system to ensure failsafe operation. Figure 7 shows the diagnostic features supported by the AMT49502 gate driver.

同样,当前传感和贴切的霍尔效应or position solutions provided by Allegro are designed with safety in mind. From the current sensor portfolio, the ACS71240, ACS70310/1, and ACS37612/10 are QM, have safety-related documentation available, and are used in applications with system-level ratings as high as ASIL D. From the angle sensor portfolio, the A1333, and AAS33001 can function as safety elements out of context with an ASIL B or D rating for the single and dual die products respectively.

Figure 7: Diagnostic functions on the AMT89502 half-bridge gate driver.

结论

BSG systems are becoming more common in HEV motor control designs due to their easy implementation, similar footprint to existing alternator systems and the elimination of major modifications to the powertrain (in P2 – P4 locations). As starter generator systems continue to evolve, further integration may impact the role of BSGs over time. Going forward, 48V systems will likely dominate in P3 – P4 locations.

As the electrical revolution continues to transform the automotive industry, electrification will continue to gain market share, and 12V solutions will give way to higher battery voltages. Using a common platform for both 12V and 48V systems will simplify and ease the transition to 48V solutions. Starter generator systems will also benefit from industry-leading safety diagnostics, redundancy offered by independent bridge control, current sensing, and motor position sensors with robust transient performance.

This article was adapted from the articleCommon Driver Platform for 12V and 48V Systemsby Dan Jacques, published in电力系统设计1月2021年出版物。可以找到原始文章这里