电子产品设计的EMC原则

从研发到最终认证, electromagnetic compatibility (EMC) principles should be a key focus of electronics product design. 除了确保 产品安全 和 无线共存, considering EMC principles in the early stages helps smooth the path to compliance 和 prevents costs 和 time associated with redesign.

EMC原则变得简单

Electromagnetic Compliance (EMC) is often described as a ‘Black Art’ but the key to unlocking it is underst和ing its basic principles. Once these EMC principles have been learned, EMC can suddenly appear much simpler. 理解是很重要的 EMI和EMC的区别.

EMC电磁干扰基础

When a product is being designed – be it a physical product or 一个系统 – it is important to ask what needs to be considered to ensure EMC is achieved. 要做到这一点, it is essential to take a step back to basics 和 consider how EMC interference is generated.

In the simplest of terms, interference is caused by moving from one state of energy to another. As with the flick of a light switch, we expect this transfer of energy to be instantaneous.

EMC法规，来自 商业 to 医疗 to 军事, are essentially all asking how to stop the voltage overshoot or undershoot during energy transfer so that a product can function without interference.

EMC原则—提出正确的问题

必须确定的是这种干扰的可能性. 不管产生多少电磁噪声, it must be remembered that there has to be someone or something receiving that noise for interference to occur. 必须提出的关键问题是:

• 这个产品会用在哪里?
• 它会干扰什么/谁?
• 能量如何从产品传递到“受害者”
• 能量要么沿着电缆传播，要么通过空气传播, 两种机制, 因此, 是辐射和传导. 使用的标准是基于辐射和传导测试. 

EMC耦合

There are mechanisms of which to be aware, such as capacitive coupling 和 induction. 这些更不寻常, even though induction is predicted to increase in significance as new technologies, 例如电动汽车和电器的无线充电, 不断涌现并被更广泛地采用, 它们造成的潜在干扰是有限的.

“With our experience getting thous和s of products successfully through final compliance 和 certification, we have identified the three most essential elements of EMC on product design: filtering, 屏蔽, 和接地/接地.”

产品设计人员在EMC中需要考虑的三个问题

考虑三个关键因素.

是否是一种产品, 一个系统, 或者印刷电路板, 基本的EMC原则保持不变. When considering how the design of the product could ensure greater electromagnetic compatibility, 有三个关键因素需要考虑:

1. 屏蔽
2. 接地/接地
3. 过滤

电磁兼容屏蔽 

Depending on a product’s function, some devices produce unwanted electrical noise. 最好的方法是防止这种噪音传播到其他, more effective radiators (such as cables) is to create a containment strategy.

A screening can (which is only solder fixed at each corner) may not be sufficient 和 having a weld along the full length of the folds is critical to ensure metal-to-metal contact, 所以槽天线不是无意中产生的.

If 屏蔽 is used, then ensuring a complete Faraday Cage is important. 布线孔, 监控, 通风会影响防护罩的完整性, so EMC honeycomb mesh 和 screened cables or metal-to-metal contact will help with a 360-degree termination of enclosures for 屏蔽. Thicker shield material will attenuate better by either reflection 和/or absorption.

EMC接地/接地技术

接地是对“电位差”的处理.’ 

接地的例子: 发生静电放电(ESD)时, a voltage exposed to a product is simply trying to find the quickest route to the ground. 如果线缆发生了静电事件, 同样的电缆直接连接到PCB上, the energy will travel along the cable 和 cause the ground plane on the PCB to jump up to the potential of the ESD level, 可能造成损坏或故障的. If that same cable was terminated on the board where the earth/ground connects to the mains entry point, 这个问题将得到解决.

Earthing/grounding can be achieved through various methods which can include:

• 灵活的电线
• 灵活的辫子
• 金属电镀

Flexible ground straps can be more usable, but this comes at the expense of effectiveness.

EMC滤波器和滤波

Filters are typically passive components that suppress RF noise 和 can be used internally on PCBs or externally on cables. The amount of electrical noise a product emits is not important; it needs to be connected to an antenna (i.e. 电缆、PCB轨道等.)，使其辐射或接收并引起问题. 因此, 所有信号线, 尤其是那些与外界有联系的人, 应该给予特定的治疗吗. This means filtering either at the point of source (emissions) or the point of entry (susceptibility). 

过滤的方法有很多种，包括:

• 电容器或电感元件
• 从信号到地有少量电容
• 铁氧体珠在整个信号/电缆束上起电感作用

Filters can be a simple retrofit installation but can be expensive if required to be added to a significant production run. 不同的材料在频率方面有不同的特性, 和 the manufacturer's literature helps you to select the most effective material for the frequency range. Design improvements during the product 和 pre-testing stage can reduce reliance on filters.

“通过在设计阶段进行测试, most of the potential issues 和 failures found in compliance testing can be mitigated.”

高性价比的电子原型设计

尽早确定原型设计

The most cost-effective approach to product development will always be to qualify the prototype design early in the development cycle. 

A key target should be to achieve success the first time at the testing, 批准, 认证阶段. 如果一款产品必须重新设计，成本可能会高得令人望而却步, 导致延迟上市和消费者信心的丧失.

考虑一下你的产品要出口到哪些国家

虽然许多国家采用了几乎相同的法规 CE标志, 一旦产品要出口, it is much more likely that m和atory third-party testing will also be required to gain 全球市场准入.

It is vital to consider where the product may be exported to as early as possible in the design process, 必要时听取建议. Modifying a product later to meet unforeseen export requirements can be a costly 和 time-consuming exercise, 一个常见的错误.

二十多年来，CE标志一直是法律要求, 然而，每年仍有成千上万的产品失败 不正确的CE标志.

我们的EMC专家随时为您提供帮助

Test houses such as im体育APP, are asked to provide guidance 和 advice on EMC合规，无论是在设计过程的开始还是结束. 通过及早提出建议，我们可以防止以后出现问题, 这是一种更安全、更具成本效益的选择.

有关我们的更多信息 EMI / EMC测试服务,请 今天就im体育APP的专家.