最近霍尔效应电流感应的趋势

作者：John Cummings，Michael C. Doogue，Andreas P. Friedrich

抽象的

本文介绍了基于集成霍尔效应的电流传感器IC的最新进展。它涵盖了用于将主要电流路径集成到系统中的各种包装概念，IC参数的主要改进，以及用于不间断电源（UPS），逆变器和电池监控的典型应用电路的一些示例。

Introduction

在工业，汽车，商业和通信系统中，对低成本，准确，小型电流传感器解决方案的需求迅速增长。各种技术可用于将电流转换为比例电压。霍尔效应磁力检测器的优点是来自电流路径的固有电压隔离和霍尔元件和接口电子设备在单个硅芯片上的集成。[1]新的设计概念和高级BICMOS技术的系统使用允许进一步改善IC性能。这些也通过支持相同电流传感器IC的附加功能（例如电源保护）的集成来打开了新产品方法。本文介绍了Allegro™ACS电流传感器IC系列的基本包装和IC设计概念，并探讨了最近的趋势，使Allegro能够开发其下一代完全集成的低成本电流传感器设备。

包装概念

Allegro电流传感器IC器件的特点是整合整体线性霍尔IC和低电阻初级电流导通路径，以单次包覆成型包装。通过霍尔换能器相对于铜导体的近距离和精确定位进行优化器件精度。低功率损耗和高压隔离是包装概念的内在型。封装电流测量系统的最终尺寸，形状和附加部件取决于要测量的初级电流的幅度。本节详细介绍了针对不同电流测量范围的创新包装技术。

高达20 A的电流

对于小的标称电流，高达±20a，霍尔模具和初级电流路径在标准尺寸SOIC8表面安装封装中封装，如图1所示，这提供了兼容的紧凑，低轮廓解决方案具有大容量自动化板组装技术。使用倒装芯片技术允许在霍尔元件的主动面和被被感测电流产生的磁场之间的优化磁耦合。因此不需要磁通集中器。用于电流检测的铜路径的内阻通常为1.5MΩ，用于低功率损耗。电源端子也与低电压信号I / O引脚电隔离。仔细的IC和封装设计允许进一步提高装置的电压隔离，典型的直流隔离电压为5 kV，并且在初级电流之间具有1.6kV最小和2.5kV的RMS隔离电压为1.6kV路径和信号侧。

图1. ACS包装的内部结构，显示U形初级铜导体和单倒装芯片安装的Hall IC。

Figure 2. Internal structure of the CB package, showing the primary conductor (copper, left), the flux concentrator (red) and the linear sip Hall ic (black) and signal pins (copper, right).

图3.±20 A（LC封装）和±200a（CB封装）电流传感器IC的照片，如硬币所示。

Currents up to 200 A

For higher currents, the cross section of the copper conductor has to be increased to accommodate the current density within the material, which is provided in the CB package. Because of the magnetic coupling between this thicker conductor and the linear Hall element, a flux concentrator has to be used. The copper path, linear SIP Hall device, and concentrator are precisely assembled before being overmolded. Through careful design of the system, the primary conductor resistance is typically as low as 100 µΩ and a minimum rms isolation voltage of 3 kV (at 60 Hz for 1 minute) is achieved between primary path and signal sides. Figure 2 shows the internal structure of such a ±200 A current sensor, and figure 3 shows a photograph of both this and the ±20 A package types.

200 a上方的电流

If currents to be measured are higher than 200 A, the ICs can be used in a current divider configuration.[2] This method involves splitting the path of the current being sensed. The simplest approach is to design a notched bus bar such that only a well-controlled fraction of the current flows through the device, the other going through a shunt path (see figure 4). The current split ratio is determined by the geometry of the bus bar. An inherent disadvantage of this approach is that it reduces the current resolution by the same proportion as the current is divided.

如果电流平均分开，则可以增加电流检测系统的分辨率，并且并行使用两个设备（参见图5）。涉及级别换档和添加两个设备输出的简单电路可用于获得与总初级电流成比例的线性输出。[2]

图4.当前分频器配置。电流传感器IC可以直接连接到汇流条。

Figure 5. Equal current splitting with enhanced resolution. The outputs of the two devices can be combined to obtain a linear output proportional to the total current to be sensed.

IC设计

This section details the basic chip architecture and most important IC parameters.

框图该装置的中心元件是一种精确的低偏置硅霍尔IC。框图如图6所示。由初级电流产生的磁通量会影响霍尔元素。使用BICMOS斩波器稳定电路来减少信号偏移，并在其工作温度范围内稳定IC的输出。[3]片上电子器件产生与输入电流成比例的模拟电压。

Figure 6. Block diagram of the circuit.

The output is ratiometric, which means that both the offset and sensitivity scale with V_CC。设备精度优化到行尾trimming of the offset, sensitivity, and temperature response. The ICs are designed to measure both positive and negative currents, but the parameters can be trimmed for uni-directionality if required. The device is trimmed after packaging in order to reduce package stress effects on the Hall element. As shown in figure 6, an external bypass capacitor is recommended, to reduce noise. If the bandwidth of the application allows it, a simple rc filter can be used at the output to further improve signal-to-noise ratio.

±20型号主要功能虽然SOIC8器件设计为±20a，但它们可以承受高达100 A的大瞬态过度电流。确定器件的过电流能力的限制因素是IC的结温（T_J(max), which equals 165°C), and is therefore determined by the thermal design of the printed circuit board (PCB) in the application.

The main features and benefits are summarized as follows:

AC and DC current measurement
1.5 mΩ internal conductor resistance
1600 VRMS (min) isolation voltage
4.5 to 5.5 V supply operation
50 kHz带宽
室温下的总输出误差±1.5％
operating temperature range of –40°C to 85°C
small footprint, low-profile SOIC8 package
near-zero magnetic hysteresis
电源电压的比率输出
符合RoHS（倒装芯片高温PB的焊球目前免于RoHS）

±200 A模型主要功能The thickness of the copper conductor allows survival of the device at up to 5× overcurrent conditions. The main features and benefits are summarized as follows:

AC and DC current measurement
100µΩ内部导体电阻
3000 VRMS (min) isolation voltage
4.5 to 5.5 V supply operation
35 to 50 kHz bandwidth
±1.0% total output error at room temperature
工作温度范围-40°C至150°C（初级电流的功能）
small package size, easy mounting capability
电源电压的比率输出
lead (Pb) free

Filter Pin External Capacitor (nF)	Bandwidth （千赫）	峰顶 Noise (mV (Typ.))
1	50	40
4.7	20	24
47	2	10

Added Functionality

For large volume applications, it may be worth integrating some additional functions on the Hall IC that would usually be realized with external components. In the implementation described below, this approach resulted in a new protection IC with integrated hot-swap gate driver and internal Hall-effect based element.

The block diagram of this ACS760 device is shown in figure 7. The power supply load is measured without the use of an external sense resistor. The part uses an integrated 1.5 mΩ copper conductor and a Hall-effect element to accurately measure load currents up to 30 A. The device contains overcurrent protection circuitry that trips at a user-selectable level between 30 and 40 A. If an overcurrent condition is detected, the fault output of the part trips and the gate of the external mosfet is pulled to ground. The delay between the detection of an overcurrent condition and gate shutdown is set by an external capacitor.

图7.具有集成热插拔栅极驱动器和基于内部1.5Ω霍尔效应元素的保护IC的框图。

应用例子

本节提供了两个应用示例，其中ACS设备支持最佳亚博尊贵会员电流传感解决方案。

电池监控Smart battery systems require circuitry to monitor cell voltages, temperatures, and currents. For capacity monitoring applications, all of these measurements are critical. The most difficult to design-in properly, however, is current measurement. The reasons for this are the requirements for accuracy, power dissipation, and solution size.

Current measurement accuracy is essential to ensuring that the capacity monitoring algorithms are working well. The traditional method of measuring this current is with a shunt in the ground path or on the low side. The key problem with this method is that, to minimize I²R losses, the value of the shunt needs to remain very small. With this approach, low-current measurement accuracy becomes compromised. What it means for notebook computer applications is that during suspend, hibernate, or other low-power states, it is difficult for the battery to accurately monitor the current flowing into the system.

If the battery is using a 10 mΩ sense resistor to minimize power dissipation at nominal loads, when in a low-power state with only 50 mA of power draw, the voltage across the shunt would be only 500 pV. This voltage is very difficult to resolve, and complicated algorithms for estimating the residual capacity must be developed for the battery in order to compensate for this effect. These routines are conservative in nature, meaning that they tend to assume that the battery is losing a little more capacity than is actually calculated. The result can be an appearance of excessive loss in battery capacity over time.

Depending on the battery and the application, sense resistors in the range of 1 to 2 W would be required to monitor the currents. Typically in portable solutions, however, there is not enough space for 2 W resistors, so the solution is usually limited to 1 W resistors. For higher-current solutions, multiple resistors are used in parallel to keep the power ratings within the device limitations. Both solutions have a large impact on the board real estate required to fit these components.

By using a Hall-effect device as a shunt solution in the battery pack, the power dissipation in the pack can be reduced. The advantage of using Hall-effect devices is readily apparent with the low insertion loss of the device. In an SOIC8 package, the ACS712 lead-frame insertion loss is only 1.5 mΩ. The difference in power consumption over a range of load currents is shown in figure 8.

The use of a Hall-effect device as shown in figure 9 can increase the accuracy of current measurements. This block diagram shows a high current path and a low current path. The low-current path can be enabled for better accuracy at monitoring small currents. Not only does the solution shown in figure 9 provide higher accuracy for lower charge and discharge currents, but also it provides more signal than the shunt solution over the measurement range. Assuming that the Hall-effect device has a gain of 100 mV/A, this signal is much larger than the resulting signal across a shunt resistor, as shown below in figure 10.

图8，分流电阻，霍尔效应测量

Figure 8. Power loss in shunt versus Hall-effect current sensing solutions.

Figure 9, shunt resistor, hall effect measurement

Figure 9. Improved accuracy and efficiency in battery monitoring with Hall-effect devices.

图10中,上海unt resistor, hall effect measurement

图10.霍尔效应解决方案的输出电压与20mΩ分流器相比。

The step increase in gain with the Hall-effect solution assumes that the application enables the high current path shown in figure 9. The actual threshold for the transition and level of hysteresis desired will be a function of the application as well as the value of the shunt employed.

在电池系统中使用霍尔效应装置将有助于减少分流传感解决方案所需的PCB区域，并使高侧传感能够中断地面路径。使用霍尔效应装置的两个主要益处在更宽的电流范围内提高了电流测量精度，并通过显着减少1，从而降低功耗²失去分流器。

Hall Effect Devices in UPS and Inverter ApplicationsThe use of either Hall-effect devices or current transformers (CT) is common in UPS systems. While CTs are seen as low-cost solutions, they actually require more support components than a Hall-effect solution and are strictly limited to ac applications. Another secondary cost attributed to using CTs to monitor the AC line voltage is the additional circuitry to manage the effects of inrush and possible core saturation during an inrush event.

UPS解决方案需要使用线路电压为电池充电，该电池用于在电源故障发生时为系统提供线电压。UPS的目标是以最大效率提供尽可能多的能量。例如，2200 VA UPS需要典型的3小时充电时间。同样的UPS只能在半负载（990 W）的大约24分钟的功率下，在满载时6.7分钟（1980 W）。对保护的输入和输出电流进行保护，并能够以置信度显示电池充电状态。

由于几种原因，ACS712霍尔效应装置非常适合监控输入电源或电池充电电流。小型霍尔效应解决方案的显而易见的益处是所需的体积是等效CT溶液的一小部分，此外还有消除增益和附加保护部件。原因是ACS712不能在设备的隔离侧上过冲。

当在高负载下为逆变器阶段供电时，具有霍尔效应IC的最佳位置是线电压本身，直接监测负载电流。原因是线电压电流可以高达15到20 a_rms.，而电池采购电流可能超过50至60，这取决于电池堆的电压和转换器的效率。下面，图11示出了在UPS动力系中使用霍尔效应装置的示例。

Figure 11. UPS power train architecture.

This next generation of Hall-effect devices is helping to resolve known issues with CTs and to improve the reliability of systems. By using Hall-effect devices in the battery charging system and inverter power train, the efficiency of the converters can be optimized. This can help to reduce the overall size of the system and save costs.

结论

创新工业电流传感解决方案l, automotive, commercial, and communications systems were presented. The packaged devices consist of a low-resistance primary current path and a monolithic linear Hall-effect IC that integrates the Hall element and state-of-the art BiCMOS interface circuitry.

该器件覆盖高达±200a的测量范围，并且还可以使用当前分频器配置设计成更高的电流应用。亚博尊贵会员详细介绍了具有添加功能的低成本，高精度和小型电流测量系统的新方法，并提供了两个应用示例。

Notes

R.S. Popovic, "Hall Effect Devices", 2nd ed., IoP Publishing Ltd., 2004.
R. Dickinson and A. P. Friedrich, Using Allegro Current Sensors in Current Divider Configurations for Extended Measurement Range, Allegro MicroSystems, LLC , applications note AN295036, April 2005.
A. Bilotti, G. Monreal and R. Vig, "Monolithic Magnetic Hall Sensor Using Dynamic Quadrature Offset Cancellation," IEEE J. Solid-State Circuits 32, no. 6 (1997): 829-36.