解决无刷直流控制器设计挑战

解决无刷直流控制器设计挑战

这篇文章首先出现在Mouser Electronics网站，罗伯特亨特利，经常贡献者Mouser Electronics'blog.

无刷电机获得牵引力

Brushless DC (BLDC) motors have become the default choice of motor for a wide range of battery and line-powered equipment and appliances. More reliable and requiring significantly less maintenance than their brushed DC motor counterparts, brushless DC motors have also benefited from a broader industry understanding of how to control them using simple microcontroller algorithms. In today’s complex and sophisticated control applications, brushed motors also create too much electrical noise, which means designers need to employ substantial electromagnetic immunity mitigation techniques. Audible noise from brushed motors is also now considered undesirable, particularly for portable battery-powered appliances such as vacuum cleaners and personal power tools, including jigsaws and drills/drivers.

Manufacturers construct brushless DC motors using fixed permanent magnets on the rotor drive shaft and a series of field windings (typically three) on the inside of the motor casing. Switching the current through the three field windings in sequence results in rotation of the drive shaft. Controlling the pulse width and the switching frequency of the drive to each field coil provides control of motor speed, acceleration, and output torque. A closed-loop feedback of the rotor’s operation to the three-phase motor control algorithm is required to closely monitor and control the current state of the drive shaft’s rotation. The two most popular methods of providing this feedback are:

• Affixing an encoder disk or other form of rotational sensor to the rotor shaft.
• Sensing the back electromagnetic field induced by the rotor’s permanent magnets within the field windings. Field-oriented control (FOC) refers to using the induced field voltage.

无传感器方法有助于提高整体电机可靠性，减少材料清单（BOM）成本。

该Architecture of a BLDC Motor Controller

如上所述，无刷电机控制器需要三个不同的电路功能。这三个不同的电路功能通过：

• A microcontroller that runs the motor control algorithm
• 提供交换信号的脉冲宽度调制（PWM）电路
• A power output stage that drives the motor

模数转对于数字功能将轴旋转传感器信号转换为数字域以进行微控制器处理。设计嵌入式电机控制器时，有几个设计考虑因素。帮助塑造嵌入式电机控制器整体设计的初始因素是：

• 所需的电源/扭矩
• 电源源
• 轴速度

今天的快节奏原型到生产焦点倾向于劝阻设计工程师使用离散部件开发定制控制器。因此，更受欢迎的设计路线是使用从货架上的微控制器运行控制算法。除了不同的外围接口选项，时钟和定时器外，大多数微控制器还包含多种ADC / DAC转换功能。适当配备的微控制器可以提供大部分所需的电路功能，但是许多微控制器往往不优化电机控制应用或包含必要的半/全“H”桥电机驱动功能。此外，能源管理是当今大多数应用的必要功能，在电机控制应用中尤为重要，能源效率等级通常是客户的关键选择标准。电源管理IC可用，但这要求工程团队将另一个IC集成到设计中，提高了BOM成本和板空间要求。

As more consumer and industrial motor-based appliances adopted a brushless DC motor design, the need for a device that includes all of the necessary functions drove Qorvo to develop a full-featured power application controller (PAC^TM值）。QorvoPAC5556 Power Application Controller^®（Pac.^TM值）集成了所有必需的模拟，电源管理和栅极驱动信号源，在单个紧凑的封装中。

介绍Qorvo PAC5556

该Qorvo.PAC5556 Power Application Controller^®（Pac.^TM值）is supplied in a slim QFN-52 package, can operate motors up to 600V_DC.，并包含任何BLDC或智能能量应用所需的全面的功能和功能（图1）。高度集成的PAC架构使Qorvo PAC5556特别适用于PCB正在收缩的应用，例如白品，压缩机和电动工具。

图1：图像提供了Qorvo PAC5556电源应用程序控制器的简化功能框图。（来源：Qorvo）

150MHz 32位手臂^®Cortex^®-M4F microcontroller core with 128kB of user-programmable FLASH memory is at the heart of the device. A nested vectored interrupt controller (NVIC), capable of accommodating up to 25 external interrupts, provides a wake-up function to enable the device to come back from different sleep modes. Clock-gating of the 24-bit real-time clock permits low-power operation. The microcontroller unit (MCU) also incorporates a high-speed 12-bit ADC. Configured for little endian operation, PAC5556’s Arm^®Cortex^®核心包括硬件suppor -M4F单片机t for multiplication and division, DSP instructions, and an IEEE754 single-precision Floating Point Unit (FPU). The integrated FPU supports complex high-resolution control algorithms, such as the ones used with FOC. The high-performance features of this MCU enable design engineers to easily implement complex real-time algorithms, safety software, and diagnostics in their applications.

A pulse-width modulation (PWM) engine provides the drive signals for the motor gate drivers. Capable of fine motor control, down to 10ns, the PWM engine consists of four 16-bit timers and 14 channels.

该analog front end of the PAC5556 is highly configurable and offers both differential and single-ended programmable gain amplifiers, ten comparators, 10-bit DACs, programmable over-current protection, integrated VM ADC sampling, and I/Os for inter-connectible and programmable signal sampling, feedback amplification, and sensor monitoring of multiple analog input signals. These analog capabilities make the device suitable for use in field-oriented control or sensor-based BLDC control applications.

Qorvo Pac5556的其他突出属性包括可配置的电源管理器和特定于应用的电源驱动程序。可配置的Power Manager包含多模式开关电源转换器，允许IC和电机驱动电路使用降压转换器拓扑进行供电。片上线性稳压器提供IC电源轨，电源管理功能控制可用的睡眠和休眠模式。设计人员可以优化用于运行时和待机模式的Power Manager。PAC非常小的待机电流导致在不使用时的电池供电工具中的非常好的电池寿命。在始终连接到AC（如白品）的设备中，Power Manager可以帮助能源星等级。电源驱动器块提供适用于各种不同电机驱动配置的所有必要的高和低侧栅极驱动器，包括半桥和完整的“H”桥。

A simplified diagram of the Qorvo PAC5556 used to drive a BLDC motor is illustrated in图2。

图2: The image provides a simplified diagram of a Qorvo PAC5556 used to control a BLDC motor. (Source: Qorvo)

为了帮助原型化和开发过程，可以提供基于Qorvo PAC556的评估板。该qorvo pac5556evk1.is a complete fully-featured evaluation and prototyping platform for the PAC5556 (图3.）。评估板支持最多三个半桥逆变器的栅极驱动，具有高达220V的额定值_AC.或450V._DC.。A virtual COM port connection to a computer together with a GUI-based software suite permits configuration and control of any application running on the PAC5556EVK1.

图3.: The Qorvo PAC5556EVK1 evaluation board. (Source: Qorvo)

Conclusion

无刷直流电机已成为一个受欢迎的选择or use in a wide range of consumer and industrial appliances. As brushless motors are incorporated into a broader range of applications, the ability to quickly design, prototype, and test motor controllers is key to speeding the overall product design process. As a result, design engineers need a device that integrates all the required analog, power management, and gate drive signal sources within a single package. The highly integrated Qorvo PAC5556 Power Application Controller meets the need for a compact power control solution that reduces energy consumption, bulk, and noise in consumer and industrial motor applications. This design also meets tighter board space requirements and keeps the BOM cost to a minimum.