以太网供电（PoE）技术白皮书：标准、应用与未来趋势（中英文）

概述

Overview

随着从交通路口机柜到灯杆等各种互联设备的日益普及，以太网供电 (PoE) 的需求也随之激增。PoE 技术允许通过单根以太网线缆传输数据和电力，从而减少了对独立电源的需求。本文探讨了 PoE 的优势、技术细节和常见用例，并强调了其在现代基础设施和物联网应用中日益增长的重要性。敬请关注 PoE 如何改变各行各业的连接方式。

With the growing proliferation of connected devices, ranging from traffic intersection cabinets to light poles, the demand for Power over Ethernet (PoE) has surged. PoE technology allows both data and power to be transmitted through a single Ethernet cable, reducing the need for separate power sources. This article explores the benefits, technical aspects, and common use cases of PoE, highlighting its increasing importance in modern infrastructure and IoT applications. Stay informed on how PoE is transforming connectivity across industries.

PoE 的基础知识和优势

The Basics and Benefits of PoE

以太网供电 (PoE) 技术可通过单根以太网线缆同时传输电力和数据，无需单独的电源线。这简化了安装过程，尤其是在难以触及的区域，并且允许企业使用现有的 Cat5 至 Cat6a 线缆，而无需对基础设施进行改造。PoE 的高效性简化了网络设置，降低了成本，并改善了安全摄像头、接入点和物联网设备等设备的连接性。下图展示了 PoE 连接与使用单独电源线和数据线的非 PoE 连接的工作原理对比。

Power over Ethernet (PoE) technology enables both power and data transmission through a single Ethernet cable, eliminating the need for separate power wiring. This simplifies installation, especially in hard-to-reach areas, and allows businesses to use existing Cat5 to Cat6a cabling without infrastructure modifications. PoE’s efficiency streamlines network setups, reducing costs and improving connectivity for devices like security cameras, access points, and IoT devices. Below shows how a PoE connection would work compared to a non-PoE connection that uses separate power and data wiring.

在 PoE 应用中，PSE（供电设备）为 PD（受电设备）供电。一个常见的例子是连接到 PoE 交换机 (PSE) 的 IP 摄像头 (PD)。

In a PoE application, a PSE (power sourcing equipment) provides power to a PD (powered device). A common example would be an IP camera (PD) connected to a PoE switch (PSE).

PoE 的主要优势

• 节省成本和时间：无需电工或单独布线，降低安装成本和时间。

• 安装灵活性：设备可放置在距离电源最远 100 米的位置，实现灵活的设置。

• 可扩展性：可根据需要轻松添加 PoE 设备，并通过网线直接供电。

Key Benefits of PoE

• Cost and Time Savings: No need for electricians or separate power wiring, reducing installation costs and time.

• Installation Flexibility: Devices can be placed up to 100 meters from the power source, allowing for versatile setups.

• Scalability: Easily add PoE devices as needed, powered directly through network cables.

PoE 市场与应用

PoE Markets and Applications

各种市场趋势数据表明，PoE 的使用量逐年增长。

Various market trend data has shown that the PoE usage continues to grow year over year.

以太网供电 (PoE) 技术的快速发展可归因于几个关键因素，这些因素正在重塑设备的供电和管理方式。其中一个最重要的驱动因素是兼容 PoE 的设备数量的不断增长。PoE 最初用于为 IP 摄像头供电，现在支持各种设备，包括接入点、智能照明、传感器等等。这种扩展的兼容性使 PoE 成为各行各业的必备解决方案，提供了一种经济高效的方式，通过单根线缆传输电力和数据。

PoE 兴起的另一个主要因素是其供电功率的显著提升。在过去的二十年中，PoE 的供电功率已从 4W 飙升至 90W，为更复杂的设备供电开辟了新的可能性。随着数据速度的不断提高，越来越多的联网设备将采用 PoE，这使得 PoE 对企业来说更具吸引力。能够为更广泛的设备（包括需要更高功率的设备）供电，是 PoE 成为现代网络基础设施不可或缺的一部分的原因之一。

PoE 的日益普及也促成了多个 IP 设备在集中管理系统下的融合。这种转变使企业能够通过一个统一的平台控制各种系统，例如照明、暖通空调、门禁、监控、传感器、数字标牌、Wi-Fi 和 VoIP。集中管理可提高效率、增强可扩展性并节省成本，使 PoE 成为智能楼宇解决方案和物联网生态系统的关键组成部分。随着 PoE 技术的不断发展，其在现代基础设施供电和管理中的作用将不断扩展，为企业提供满足其网络需求的面向未来的解决方案。

The rapid growth of Power over Ethernet (PoE) technology can be attributed to several key factors that are reshaping the way devices are powered and managed. One of the most significant drivers is the increasing number of PoE-compatible devices. Initially used for powering IP cameras, PoE now supports a wide array of devices, including access points, smart lighting, sensors, and more. This expanded compatibility has made PoE an essential solution for a variety of industries, providing a cost-effective and efficient way to deliver both power and data over a single cable.

Another major factor contributing to the rise of PoE is the significant increase in the power it can deliver. Over the past two decades, PoE power delivery has surged from just 4W to as much as 90W, opening up new possibilities for powering more complex devices. As data speeds continue to increase, more networked devices will incorporate PoE, making it an even more attractive option for businesses. The ability to power a wider range of devices, including those requiring higher wattages, is one of the reasons PoE has become integral to modern network infrastructure.

The growing adoption of PoE has also resulted in the convergence of multiple IP devices under centralized management systems. This shift enables businesses to control various systems, such as lighting, HVAC, access control, surveillance, sensors, digital signage, Wi-Fi, and VoIP, all from one unified platform. Centralized management offers enhanced efficiency, scalability, and cost savings, making PoE a key component of smart building solutions and IoT ecosystems. As PoE technology continues to evolve, its role in powering and managing modern infrastructure will only expand, offering businesses a future-proof solution for their networking needs.

主动 PoE 与被动 PoE

Active PoE vs. Passive PoE

如前所述，PoE 供电是通过传输数据的同一根线缆进行的。PoE 协议有两种：主动 PoE 和被动 PoE。下表列出了主动 PoE 和被动 PoE 之间的区别。

As mentioned previously, PoE provides power over the same cabling used for data. There are two types of PoE protocols – active and passive. Below is a comparison table of the differences between active and passive PoE.

主动式 PoE 为插入 PoE 端口的非 PoE 设备提供保护。如果端口为被动式 PoE，则无论设备是否支持 PoE，它都会为其供电。

Active PoE provides protection for non-PoE devices that get plugged into a PoE port. If a port is passive PoE, it will provide power to the device regardless of it being PoE-enabled or not.

PoE流程

PoE Process

那么，主动式 PoE 如何为启用主动式 PoE 的设备供电呢？

1. 当设备 (PD) 插入时，PSE 会检测 PD 是否具有正确的电阻值，以便将其正确归类为 PoE 设备。

2. 根据 PD 的类别特征，对 PD 进行分类以确定其额定功耗。

3. 在启动期间，PSE 会根据 PD 的类别，将浪涌电流限制在适当的值。

4. PSE 会定期与 PD 执行“保持连接”功能，以维持其正常运行。

5. 当 PD 与 PSE 断开连接时，PSE 必须在线缆断开后的 15-20 毫秒内移除电压。

So then, how does active PoE provide power to a device that is active PoE enabled?

1. When a device (PD) is plugged in, the PSE will detect if the PD has the correct resistance value to correctly categorize it as a PoE device.

2. The PD will be classified to determine its rated power consumption, based on its class signature.

3. During startup, the PSE will limit the inrush current with the appropriate value based on the PD class.

4. The PSE will periodically perform a keep alive function with the PD to maintain operation.

5. When a PD is disconnected from the PSE, the PSE must remove voltage within 15-20ms of the cable being disconnected.

PoE 标准

PoE Standards

在上面的主动与被动 PoE 对比表中，主动 PoE 指的是 IEEE 802.3af/at/bt。这些标准由 IEEE 组织定义。这些标准按类型定义，并根据每个类别分配相应的功率。PoE 共有 4 种类型，由 8 个等级组成。

802.3af = 1型，1-3级

802.3at = 2型，4级

802.3bt = 3型和4型，5-8级

下表显示了每个等级 PSE 可提供的功率以及 PD 接收的最小功率。

In the Active vs. Passive comparison table above, Active PoE is referring to IEEE 802.3af/at/bt. These are standards defined by the IEEE organization. These standards are defined by types with the amount of power that’s provided allocated per class. There are 4 types, made up by 8 classes.

802.3af = Type 1, Class 1-3

802.3at = Type 2, Class 4

802.3bt = Types 3&4, Class 5-8

The chart below shows the power that the PSE can provide along with the minimum power that the PD receives, per class.

五类或六类网线有 4 对线。

802.3af 和 802.3at 标准使用 2 对线。引脚排列有两种可能的模式（A 和 B）。在这两种模式下，电源部分均不使用 4 对线。下图显示了这两种模式的引脚排列。

In a cat5 or cat6 cable, there are 4 pairs of wires.

802.3af and 802.3at operate over 2 pairs of the wires. There are 2 possible modes (A and B) for the pinouts. In both modes, 4 wires are not utilized for the power portion. The diagram below shows the pinouts for both modes.

802.3bt 通过 4 对线运行。在这种情况下，所有 4 对线都用于供电。与 802.3af/at 相比，802.3bt 主要有四项改进：

• 支持 Type 3 (60W) 和 Type 4 (90W)

• 支持双特征 PD。这意味着设备可以拥有两个独立的检测和分类电路。这对于带加热器的 IP 摄像头等设备非常有用。

• 更低待机功率 – 最小待机功率为 20mW，比 802.3at 的 200mW 低 10 倍。这可以节省大量能源，尤其是在 PoE LED 照明领域。

• 自动分类 – 向 PD 输送的最小功率为 71W，但 PSE 可以自动检测 PD 的实际最大功耗并进行相应调整。

802.3bt operates over 4 pairs of wires. In this case, all 4 pairs are used to deliver power. There are 4 main improvements made in 802.3bt, compared to 802.3af/at:

• Support for Type 3 (60W) and Type 4 (90W)

• Support for dual-signature PDs. This means that a device can have two separate detection and classification circuits. This would come in useful for a device such as an IP camera with a heater.

• Lower standby power – minimum standby power is 20mW, which is 10 times lower than the value for 802.3at, which is at 200mW. This can save a lot of energy, especially in PoE LED lighting.

• Autoclass – a minimum of 71W is delivered to the PD, but the PSE can automatically detect the actual max power drawn by the PD and adjust accordingly.

补充说明

Additional Notes

以下是需要了解的重要因素：

• PD 功率 – 请务必参考传输至 PD 的功率，而不是 PSE 的输出功率。例如，如果摄像机需要 28W 的功率，那么使用 802.3at 标准为摄像机供电是不够的，因为 PSE 的输出功率为 30W，而传输至 PD 的功率仅为 25.5W。

• 电压 – 对于需要直流输入才能启动的 PSE 设备，请注意不同标准的输入电压范围。例如，Type 4 要求的电压范围为 52V 至 57V。48V 电源非常常见，这意味着电源至少需要能够升压至 52V 才能为 802.3bt PD 供电。下表列出了每种类型所需的电压范围：

Below are important factors to know:

• PD power – Make sure to refer to the power that is delivered to the PD, rather than the power that is output from the PSE. For example, if a camera needs 28W of power, it will not be sufficient to power the camera with 802.3at, which outputs 30W from the PSE, but only 25.5W is delivered to the PD.

• Voltage – for PSE devices that require a DC input to power up, be aware of the input voltage range of the different standards. For example, Type 4 requires a voltage range of 52 – 57VDC. 48VDC power supplies are very common, which means that the power supply needs to be able to be cranked up to 52V at a minimum to be able to power up an 802.3bt PD. Below is a table of the voltage ranges needed for each Type:

• 专有协议——在 IEEE 批准 802.3bt 标准之前，有些设备所需的功率超过了 802.3at 标准 (30W) 所能提供的功率。当时开发了几种专有协议来解决这个问题。这些协议主要以注入器的形式实现。其基本工作原理是，协议将协商为 802.3at 标准，但不是通过 2 对线供电，而是通过 4 对线供电，从而使 PSE 的供电功率高于 30W。

• 向后兼容——所有 IEEE PoE 标准/协议均向后兼容。归类为 802.3af PD 的设备仍可在 802.3bt PSE 上正常工作。

• Proprietary protocols – before 802.3bt was ratified by IEEE, there were devices that required more power than what 802.3at (30W) could provide. There were several proprietary protocols that were developed at that time to handle this issue. This was implemented mostly in the form of an injector. The basic mechanism of the operation was that the protocol would be negotiated to be 802.3at, but instead of delivering power over 2 pairs, it would deliver power over 4 pairs, allowing the power to be higher than 30W out of the PSE.

• Backward compatibility – all IEEE PoE standards/protocols are backward compatible. A device classified as an 802.3af PD will still work without any issue on an 802.3bt PSE.

托管型 PoE 交换机功能

Managed PoE Switch Features

PoE 交换机是最常见的供电设备 (PSE) 类型之一，托管型 PoE 交换机比非托管型交换机提供更多高级功能。非托管型 PoE 交换机本质上是即插即用设备，而托管型 PoE 交换机则能够同时配置网络和交换机本身。例如，EtherWAN Systems 的托管型 PoE 交换机提供了专门为优化 PoE 功能而设计的额外配置选项。

• PoE 调度 – 托管型 PoE 交换机支持高级 PoE 调度功能，允许用户配置单个 PoE 端口在特定日期和时间供电。这种灵活的调度功能可帮助企业优化用电情况，并通过仅在需要时为设备供电来降低能耗。

• 专有模式 – 该模式允许高功率受电设备 (PD) 通过 PoE 端口以高于 30W 的功率供电，同时仍协商为 802.3at 标准。此功能非常适合需要更高功率的设备，可确保高效可靠的性能。

• PoE 看门狗和恢复 – PoE 看门狗和恢复功能允许将单个 PoE 端口配置为 ping 连接的 PoE 设备。如果设备在指定时间内未响应，端口将自动重启，从而有效地完成设备的电源循环。这种自我修复功能无需人工干预即可恢复设备，从而显著减少停机时间并最大限度地降低维护成本（例如上门服务的需求）。

One of the most common Power Sourcing Equipment (PSE) types is the PoE switch, with managed PoE switches offering more advanced features compared to unmanaged switches. While an unmanaged PoE switch is essentially a plug-and-play device, a managed PoE switch provides the ability to configure both the network and the switch itself. A managed PoE switch from EtherWAN Systems, for example, offers additional configuration options specifically designed to optimize PoE functionality.

• PoE scheduling – Managed PoE switches enable advanced PoE scheduling, allowing users to configure individual PoE ports to provide power on specific days and times. This scheduling flexibility helps organizations optimize power usage and reduce energy consumption by powering devices only when needed.

• Proprietary mode – this allows high-power Powered Devices (PDs) to be powered by PoE ports at greater than 30W, while still being negotiated as 802.3at. This feature is ideal for devices that require higher power, ensuring efficient and reliable performance.

• PoE watchdog and recovery – The PoE watchdog and recovery feature allows individual PoE ports to be configured to ping connected PoE devices. If a device fails to respond within a specified time, the port will automatically reboot, effectively power cycling the device. This self-healing capability can recover devices without the need for manual intervention, significantly reducing downtime and minimizing maintenance costs, such as the need for truck rolls.

结论

Conclusion

随着 PoE 标准的不断扩展，将会有新的设备和应用利用这些新技术。PoE 将稳步普及，比以往任何时候都更加普及。EtherWAN 的强化级 PoE 交换机系列能够满足最新的 802.3bt 标准，即使在极端温度（-40°F 至 167°F 环境温度）下也能不间断运行，并具备专有模式和 PoE 看门狗等优质功能。

As PoE standards continue to expand, there will be new devices and applications to take advantage of the new technologies. PoE will steadily become more widespread than ever. EtherWAN’s range of hardened-grade PoE switches provide power to handle the latest 802.3bt standard, uninterrupted operation even in extreme temperatures (-40F to 167F ambient), and quality of life features such as proprietary mode and PoE watchdog.