Delivering Futuristic Vehicle Features with Comfort Motor Drive

What you'll learn:

The move to more integrated solutions for next-gen power-lift applications.
Details of the development of multi-MOSFET ICs to meet today's automotive design demands.
效率和EMC之间的妥协。

从驾驶员的援助系统和智能照明到娱乐和舒适系统，在新闻活动和自动演示中，概念车和新的模型演示展示了个人车辆的令人兴奋的未来外观和功能。这些概念背后，对它们的实现至关重要，是一系列自动机械特征。门平滑地滑动到位，窗户滑动打开，坐着静静地将自己塑造成乘客的首选位置。这些和许多其他功能依赖一系列舒适的运动驱动技术。

While mechanical systems such as power windows have long been standard features of the modern car, power seats and power lift gates are now making the move from optional extras to standard equipment. Approximately 60% of U.S. vehicles already have such equipment fitted, and in the Chinese automotive market, electric seats without recourse to any manual adjustment are standard.

As the drivetrain moves to hybrid and fully electric, and the dashboard and user interface morphs to match 21^st-century visions, consumer expectations for electric-everything are growing rapidly. In turn, we’re seeing rapid evolution in the technology required to implement these comfort features.

Comfort Motor-Drive Requirements

使大众市场可用性的舒适性功能的许多要求很简单。溶液的物理体积以及一定程度的重量起作用。系统效率（低功耗）在活动和待机时都很重要，尤其是对于电动汽车而言。此外，还有一个动力来减少可听见的噪音，尤其是在高级和电动汽车方面。必须从一开始就考虑电磁兼容性（EMC）。最重要的是，鲁棒性，可靠性和安全性是中心阶段。

为了满足这些要求，该行业正在远离早期电动机驱动应用程序中使用的基于机械的开关和继电器。所有电子设备组件都必须处理粗糙的机械和嘈杂的电气环境，这一点至关重要。诊断也是一个关键方面，要求每个舒适的电动机驱动电子控制单元（ECU）可以在车辆内网络上进行询问。最后，必须满足ASIL安全要求，以确保乘员免于捏或压碎，即使在失败条件下也是如此。

To keep pace with the increasing adoption rate, electronics suppliers are rapidly developing greater levels of chip-level integration to achieve the reduced size, increased reliability, and robust feature sets needed for the next generation of power-lift technologies（图。1）。Improvements aren’t limited to bringing discrete technologies into a single package and enhancing existing features. Newer system designs now benefit from simplified development and testing, improved in-vehicle diagnostics, greater system efficiency, and an overall better customer experience.

Major system blocks include a microcontroller (providing control, networking, and implementation of the safety concept), power converter, as well as transceivers used for LIN, CAN or CAN-FD. The power control block is protected by a reverse-battery MOSFET. From here, gate drivers link the microcontroller with the power MOSFETs in an H-bridge configuration that offers the required directional and speed control.

拉丝直流电动机仍然是流行的选择，尽管无刷直流电动机（BLDC）提供了降低的听觉扭矩噪声，更高的效率和紧凑的尺寸。位置传感和局部控制按钮，以及供应感测，绕开设计。当然，给定电动机控制器中的每个设备都是AEC-100合格的。

增加集成，设计复杂性降低

为了追求近乎电力的动力运营，汽车工程师正在使用机电继电器转向纯固态解决方案，从而消除了点击噪声。为此，Infineondeveloped multi-MOSFET driver ICs that can be used to replace all relays with N-channel MOSFETs, including the reverse-battery protection circuitry（图2）。结果是无声切换，继电器是不可能的。

New integrated driver ICs supporting up to 16 N-channel MOSFETs, thus controlling eight half-bridges within a single packaged device, can power up to four dc motors under independent control, or up to seven if a cascading approach is allowed in the design. A similar device for control of up to four half-bridges shares the same package and pinout. A further charge-pump is available to control a reverse-battery MOSFET.

主机访问驱动器集成电路的单片机functionality via a 24-bit SPI interface. This can also be interfaced with ease to devices that operate with fixed 32-bit frame sizes. In addition, the driver integrates a watchdog function, protection and diagnostics, and an adaptive driver capability. Diagnostics allow all 16 gate drivers to be monitored individually, as well as monitoring of the supply voltage, charge pump voltage, and temperature for both warning and shutdown conditions for the IC.

多MOSFET驱动程序不会损害功率效率。在电源上，它立即以睡眠状态开始，当启用输入较低时，绘制小于8 µA。在这种状态下，门驱动程序也关闭了。一旦启用输入变高，设备将进入正常模式状态，除非禁用，否则要求监管机构定期维修。

An active free-wheeling control scheme also helps to reduce power losses. Power is typically lost in the free-wheeling MOSFET during pulse-width-modulation (PWM) operation. Active free-wheeling enables the MOSFET associated with the free-wheeling, allowing current to flow through the MOSFET rather than its body diode. This can result in a 4-W power saving (70% duty cycle at 15 A) compared to a passive free-wheeling approach（图3）。It also helps reduce the temperature rise caused by this type of loss in the MOSFETs.

Housed in a 7- × 7-mm VQFN-48 package with an exposed pad, Infineon’s driver supports optical lead tip inspection and offers optimal thermal characteristics. The high level of integration translates to an exceptionally high level of density and cost efficiency with minimal BOM and PCB area for the high number of motors supported.

Variants also are available with permanent motor brake capability that hinders unintentional movement even in sleep mode. This supports an increasingly popular smart closure feature to prevent accidental injury. Moreover, it can be configured to activate in situations of supply overvoltage that result from the motors operating in generator mode.

Ensuring Safety by Diagnosing Failures

驱动程序IC的标准集成安全功能是一个监管机构，在电源上启用。在开发过程中，可以通过遵循确保不会意外打开的过程来禁用它。如果SPI通信发生物理错误，例如短路信号线，多MOSFET驱动程序将进入故障安全模式。

Furthermore, the SPI communication is monitored continuously for errors. Detectable errors range from an incorrect number of bits and protocol errors, such as addressing unused addresses, to clock polarity errors or accesses in fail-safe mode that don’t belong to the specified exit sequence. Protection also is enabled when operating in daisy-chain mode. Here the communication with the microcontroller is monitored to ensure that data frames are always a multiple of 8 bits in length.

Ending the Compromise Between Efficiency and EMC

实施完全固态解决方案的挑战之一是在电效率，保持低损失和满足EMC要求之间达到最佳平衡。最佳的负载管理技术和使用高速PWM信号在座椅和闭合上的软启动/停止是常见的。但是，负载时的高速过渡可能会导致EMC挑战。这导致了通过寄存器中的降速控制引脚或有限的配置选项进行妥协的现状。

Adaptive MOSFET gate control addresses this with a truly unique level of granularity. Not only is it possible to modify the switching slope without affecting the dead time, preserving the widest range of duty cycles, it also allows differing slew rate for both the ON and OFF cycles. Fully configurable through software via the SPI interface, it allows designers to compensate for the difference in current required between turning a MOSFET on and off. The feature is also “self-adapting，，，，” in that the driver IC recognizes and compensates for lot-to-lot variations of MOSFETs.

Quick Response to “Soft” Short Circuits

Another challenge in such motor-control applications is differentiation between failure cases. Shorts to ground or battery, or the case of open load, ideally need to be detected before turning on the MOSFETs. Next, there’s the challenge to determine the difference between hard short circuits and soft short circuits. The latter appear as higher-than-normal current draw caused by motor problems or wiring harness issues, but they’re not high enough to trigger typical short-circuit protections.

在本文讨论的驱动程序IC中，这些条件由两个功能处理。第一个涉及集成的上拉和下拉电流来源，这些电源可检测到电池或地面的短裤以及开放式负载箱。第二个功能利用了集成的电流传感操作放大器。这些都是可配置的，可以定义“软短路”阈值。因此，该设备可以在微秒的问题上独立响应此类故障以及硬短路。这可能比等待主机微控制器识别故障并通过软件做出响应要快得多，并且可以使MOSFET缩小尺寸。

Sensing of the drain voltage of the high-side MOSFETs can be configured in many different ways, even when the motors are cascaded. For example, in a six-motor configuration, high-side shunt resistors may be implemented to monitor two groups of three motors. Alternatively, the shunt resistors could be placed in series to the two groups of motors. In a four-motor configuration controlled by eight half-bridges, monitoring in both the high and low side also can be used.

即使使用精确的布局和组件，通常用于在系统电源上配置半支架的双40-V MOSFET可能会在PCB痕迹中表现出散落的电感，必须用外部过滤组件来控制。新的双MOSFET(Fig. 4)are wired internally in a half-bridge configuration in a single package, thus reducing layout issues and required external filters.

System Basis Chip to Round Off the Implementation

在Figure 1are commonly implemented today in system basis chips (SBCs). A typical device(Fig. 5)provides three low-dropout voltage regulators (LDOs) for the microcontroller, transceivers, and sensors used. It also features a CAN-FD transceiver and up to two LIN transceivers that conform to the latest automotive standards and OEM requirements. In addition, there are devices that support Partial Networking (PN).

完整的功能集是一对高压通用I/OS（GPIO）和为提供LED，板外传感器或开关输入而实施的高端输出。低静态电流有助于系统设计的总体效率，当通过Can和WK插头唤醒时，在睡眠模式下的15 µA范围为19.7 µA（例如，启用了从句柄/开关的直接信号）。