Rethink What Is Possible for PCB Current Sensing

Rethink What Is Possible for PCB Current Sensing

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By Motaz Khadar, Strategic Marketing Manager, Allegro MicroSystems

介绍

Across all markets, from renewable energy and motor drives to electric vehicles, electronic devices are challenged to be smaller, more efficient, and less expensive. This increases the complexity of printed circuit board (PCB) designs and pushes engineers to find innovative solutions. Because all these solutions require power, electrical current (I) and voltage (V) must be sensed and are mission critical in these applications. Having accurate current sensing makes controlling, protection, and monitoring feasible at various levels in the system.

当谈到选择正确的现在的感觉r for PCB designs, current handling capabilities becomes increasingly important. Current measurements in PCBs often max out at about 100 A due to thermal limitations within the PCB. Going higher than 100 A generally requires a complex solution that can translate into a bigger size and higher associated costs. However, being able to measure PCB currents reliably above 100 A can also offer great advantages such as efficiency improvements and overall system-level cost reductions.

Two common current sensing methods used today are shunt resistors and magnetic sensors. Both solutions use the voltage developed across a small-valued resistor (shunt) or a magnetic sensing element (such as Hall effect) with an integrated conductor to interpret the current value. While shunt methods usually offer very good resolution and accuracy, they suffer from energy inefficiency due to their ohmic losses and increased layout complexity associated with the shunt resistor connection and changing solder resistance over lifetime. Newer magnetic sensor options overcome these limitations – by offering standalone integrated solutions that make PCB current measurements up to 600 A possible due to their very small ohmic losses and compact size.

This article will discuss two new innovative approaches to measure currents up to 600 A in PCB: a near lossless Hall-based current sensor with an integrated conductor and a non-invasive standalone core-free and shield-free differential Hall current sensor.

Near lossless Hall-based current sensors with an integrated conductor

Electronic devices in various markets are seeing increasing needs for higher current density solutions to increase their overall efficiency and lower their cost. For example, power conversion applications such as DC/DC converters and on-board chargers are seeing a rapid increase in their current density due to the increased adoption of wide bandgap transistors like silicon carbide (SiC) to enable circuit miniaturization and improve the overall efficiency of the system. Current sensors in these applications ideally need to be compact, efficient, accurate, and offer high bandwidth to capture the very fast current wave that these high switching transistors produce.

There are two popular solutions to this challenge today – shunt resistor-based solutions and magnetic sensors. For magnetic sensor options, Allegro MicroSystems offers a broad range of very low resistance, highly integrated current sensor packages with different current and voltage handling capabilities. Existing shunt solutions require complex layout and circuit implementation to achieve high current and voltage levels and typically have higher resistance. In contrast, Allegro’s current sensors are differentiated by their compact size and ease of use, as highlighted in Figure 1.

近日，Allegro推出了两种新的表面贴装封装选项，可以测量最多500 A的电流。首先是一种模块状的定制包，可以检测高达500 A的电流，具有非​​常小的电阻（100μΩ），同时提供优异的工作隔离电压额定值 - 1350 V基本工作电压。被称为“CB”封装，这具有一个集成的内部铁磁聚光器，将场从承载迹线引导到霍尔元素的敏感平面中。图2表示将组成CB包装的不同组件。通过引线框架的电流产生由聚光器指向IC的磁场。信号销退出超模包以连接到外部电路。基于霍尔效应的电流传感器的性质允许固有隔离，因为电流承载引线框架不需要电连接到IC。CB封装内的塑料模具化合物还从引线框架中绝缘和信号引脚。CB封装已被认证至UL规范60950。

This package is a unique solution for high-density PCB design that allows customers to shrink their overall size with a simple, easy-to-use current sensor compared to other expensive, bulkier, and more complicated solutions such as shunts or larger modules. More details about the thermal performance can be found in this应用笔记. Other alternative high current density packages include Allegro’s tiny (6.4 × 6.4 mm2) custom LR package, which can handle up to 500 V DC working voltage and 100 A+ current. A third offering is the new custom SOIC16W (MC) package that has a thick leadframe that allow this package to pass 80 A+ while offering excellent 1600 V basic isolation voltage. Figure 3 highlights the different packages temperature rise as various continuous current levels.

独立，无侵入性，无核和无屏蔽电流传感器

对于需要雷竞技最新网址非侵入性，高电流密度解决方案的应用，Allegro最近推出了一个新的无芯电流传感器系列，包括新的ACS37612。本产品系列为当前测量提供真正的独立解决方案;这些解决方案使设计人员能够从其设计中删除核心和屏蔽。这些传感器测量高达600A流过PCB的电流，典型精度为1％。用于测量磁场的差分霍尔元件为杂散磁场提供了很大的免疫，而不需要竞争解决方案所需的层压屏蔽，这减少了设计尺寸和材料清单（BOM）。有关操作和实施原则的基本概述，请参见图4。

A: Basic theory of operation
B: Implementation method in a PCB

A typical application for such a solution is a traction inverter in electrical vehicles. During acceleration, hundreds of amps flow through the traction motor inverter. A precise measurement of such high currents is vital for safe operating performance. Engineers have traditionally relied on a low-hysteresis laminated core for such measurements—using three to six cores, depending on the number of phases in the motor.

确定电流动态范围的系统耦合因子由ACS37612和PCB的金属迹线的灵敏度水平确定。对电流承载迹线的所需修改增加了非常小的电阻，〜50μΩ。这为设计人员提供了许多制造灵活性，并且能够在设计的任何阶段轻松增加电流传感范围。

通过ACS37612消除核心允许制造商降低逆变器的空间和重量，从而提高了电动车辆的效率。这种无侵入性的非接触式电流传感器旨在提高相对于分流溶液的热效率，因此是在48 V电子电机平台和高压逆变器中降低系统能耗的理想选择。

Conclusion

随着电子系统的进步，需要高效，高电流，高效的PCB电流传感器的越来越重要，因为当前测量播放的关键作用是常见的。简单，易于使用的表面贴装电流传感器，Allegro集成导体解决方案的线路在电流和电压隔离功能方面解决了市场需求。为了更具灵活性，设计人员可以倾向于Allegro的新无芯电流传感器，用于真正独立，无损，无侵入式电流测量。这两种解决方案都在PCB电流检测中设置了新标准，允许系统设计人员实现新的效率和功率密度。

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