Fully Integrated Hall-Effect Motor Driver for Brushless DC Vibration Motor Applications
Fully Integrated Hall-Effect Motor Driver for Brushless DC Vibration Motor Applications
By Shaun Milano, Allegro MicroSystems, LLC
Abstract
振动电机用于各种应用，包括手机手机，游戏操纵杆，手持式视频游戏，寻呼机，牙刷和剃须刀雷竞技最新网址只有几个。特别感兴趣的是移动手机市场，随着2007年的全球产量预计大于10亿手机。手机市场在微型振动电机的设计和制造技术方面推动了创新。较小的手机需求电机消耗较少的PCB区域，需要薄的电机设计。电机功能对于呼叫者ID振动音调以及游戏应用程序也被添加到手机上。雷竞技最新网址本文将讨论一个先进的Hall效果技术Allegro™MicrosystemsA1442无刷直流BLDC电机驱动器非常适合提供先进的手机振动电机功能。
Vibration Motor Designs
Most vibration motors consist of a small electrical motor that drives an unbalanced weight, as shown in figure1。
图1.硬币型振动电机。在保护外壳中相对平坦的偏心重量旋转。（1）外壳，（2）转子底座，（3）重量和（4）轴。
电机是直流（DC）刷或无刷电机，并配置为两个基本品种：coin（或者Flat) andcylinder（或者酒吧).
气缸型电机是具有传统轴向设计的简单刷电机，如图2所示。圆柱电机在各种应用中使用，但由于其大尺寸而在移动手机应用中是不希望的。雷竞技最新网址气缸型电动机要求手机内最大的体积，通常是所有振动电机的最大直径空间。
图2.气缸（条）型振动电机，外部重量旋转垂直于身体。
所有刷子电机在换向点产生火花，因为画笔在电机线圈中切换电流。这些火花是宽带射频干扰（RFI）的优异发射机。刷子磨损并被证明是电机故障的主要原因。
需要更小的，更薄的设计导致刷电机技术的适配到硬币型电机中，如图3所示。与刷子接触的换向器点激励转子中的电线箱。激励线圈建立足够强的磁场，以与集成在定子中的环形磁铁相互作用，导致旋转。
As shown in figure 3, the commutation points are arranged in alternating polarity pairs, so as the rotor moves, the coils are constantly reversing polarity as they pass over commutation points. In this way the motor continually rotates, and at a speed that is proportional to the applied voltage. The more complex brushes in coin designs are generally less reliable than their equivalent brush cylinder motors.
图3.. Brush coin-type vibration motor exploded view. (1) enclosure top, (2) rotor (view as mounted), (3) rotor (inverted view), (4) enclosure bottom, (5) coils, (6) commutation points, (7) alternating power supply circuits, (8) ring magnet (showing representative polar zones), (9) power supply brushes.
无刷振动电机
如所讨论的，无刷电机带来了延长的电机寿命，并通过缺乏火花来消除RFI。BLDC设计还提供行业中最小的直径和最薄的币式电动机。图4示出了这种电动机的基本结构。
图4.无刷硬币式振动电机爆炸视图。刷子和换向触点由霍尔效应传感器IC（显示的Allegro Microsystems A1442）取代，线圈被重新安置到定子。雷竞技竞猜下载（1）外壳顶部，（2）转子（视图为安装），（3）转子（倒视），（4）外壳底部，（5）环形磁铁（显示代表极性区域），（6）偏心重量，（7）线圈。
在这种设计中，转子组件包括磁铁以及在旋转期间提供振动的重量。相对庞大的线圈移动到定子，在那里它们连接到控制IC。
Digital commutation and linear soft-switching eliminates the sparks and therefore RFI interference. The fully integrated A1442 Hall-effect device and precision amplifier are coupled to an internal full bridge output through comparator circuitry that determine the proper commutation points. The third wire shown in the motor of figure 4 is optional, connecting to an enable pin on the A1442 that can be used to control the active braking and sleep functions. This third wire can be eliminated by tying the IC pin to VCC on the PCB.
A1442是驱动电机所需的唯一IC。图5中的功能框图说明了设备操作和高级功能。在图4和5中通知，集成霍尔元件消除了对外部霍尔元件的需求，从而将电动机PCB组件计数降低到A1442。所需的唯一外部元件是标准电路特征，位于应用电机支架PCB上的0.1μF旁路电容，用于最小化电源时产生的电压尖峰。
图5。A1442BLDC vibration motor driver functional block diagram.
软切换和换向
当器件为向上电时，它会感应磁场并激活桥接器。根据磁极设置有源晶体管。南极性磁场激活输出晶体管Q1和Q4，驱动V的电流OUT1到V.OUT2. As a north polarity magnetic pole approaches (due to rotation), Q1 and Q4 are turned off and Q2 and Q3 are turned on. This drives current from VOUT2到V.OUT1从而反转在线圈中流动的电流方向。
Motor designs vary, but maximum rpm ranges from 9 000 to 15 000 rpm. Most designs employ a 4-pole rotor magnet, with a few designs using 6-pole magnets. Using these parameters, it is easy to calculate the commutation switching frequency (fCS，Hz）使用以下公式：
FCS= RPM × PP / 60 ,
where PP is the quantity of pole-pairs. For a 4-pole magnet at 9 000 rpm, fCS是300 Hz，对于6杆磁铁，为15 000 rpm，它是750 Hz。因此，换向信号和线圈电流切换事件发生在可听频率范围内。软切换驱动算法最佳，可通过逐渐减少通过切换电感电机线圈负载而产生的可听噪声和EMI，然后在线圈中反转电流来最小化。图6中的时序图说明了切换行为。
图6. A1442 BLDC振动电机驱动器时序图。（1）由A1442，（2）霍尔电路内部信号感测的转子磁体场，用于换向，（3）全桥接信号，（4）A1442输出，（5）诱导电机线圈电流。
主动制动，睡眠模式和防摊位
Allegro A1442具有集成的主动制动功能，可用于快速停止循环。快速停止启动周期可用于振动铃声的移动手机，当手机处于静音模式时的来电显示，以及用于游戏应用程序。雷竞技最新网址使用/睡眠引脚激活制动功能，如图5所示。
当向/睡眠引脚施加低信号时，A1442通过反转输出桥的极性并通过电动机线圈启动主动制动功能。反转电流和因此该领域的效果是施加力以沿反向旋转电动机，这将迅速减速电动机。制动后，A1442通过关闭IC的有源电路来进入睡眠模式。
在睡眠模式期间，IC的电流消耗通常小于1μA。/睡眠引脚可以消除客户PCB上的FET晶体管，否则将有必要打开和关闭电机的电源;结果，电动机可以永久地连接到电池。
如果电机档位，A1442将启动防失速算法。发生失速事件时，输出将不断打开和关闭以重新启动电机。开关周期产生扭矩循环，摇动电机并提高开始的概率。它还防止了可能损坏电机线圈的连续失速电流。
保护和超薄包装
反向电池保护融合在A1442上以保护装置，以防电动机导线在PCB上无意中焊接，使返工成为可能。
如果设备通电时，线圈的输出无意中短路，则A1442具有热关断保护，可以随着IC加热而禁用输出。反向电池保护功能和热关机已被证明是装配厂和OEM板组件的返工非常稳健的功能。
With the advent of very thin designs, such as the Motorola®MOTORAZRTM值phone, the thickness of the vibration motor has become an important selling feature. The Allegro A1442 device is available in one of the world’s thinnest MLP packages. With present finished motor thickness trending toward 1.5 mm and below, additional design flexibility is obtainable using the Allegro EW package, an MLP (DFN) with an overall package height of 0.4 mm maximum, and length and width dimensions of only 1.5 mm × 2.0 mm. The A1442 EW package is shown in figure 7.
图7. EW包装中的A1442。
概括
The A1442 is a full-bridge motor driver designed to drive low-voltage, brushless DC (BLDC) motors. Commutation of the motor is achieved by use of a single Hall element to detect the rotational position of an alternating-pole ring magnet. The device integrates all the necessary electronics. This includes the Hall element circuit used for commutation, the motor control circuitry, and the full output bridge.
This fully integrated single chip solution provides enhanced reliability (including reverse battery protection and output short circuit protection) and eliminates the need for any external support components besides the standard external 0.1 µF bypass capacitor.
The A1442 employs a soft-switching algorithm to minimize audible switching noise, and RFI and EMI interference. An active braking function is available on a third pin that can be used for fast stop-start cycles for caller ID and gaming functions. The third pin also enables a micropower sleep mode to reduce current consumption for battery management in portable electronic devices. The small footprint and low profile EW package enables extremely thin motor designs.
Allegro A1442 BLDC电机驱动器非常适合在便携式手机和其他产品中提供高级功能和包装，如寻呼机，手持式视频游戏控制器，电子牙刷和剃须刀。雷竞技最新网址