Power Supplies (PSUs) provide electrical energy to devices, categorized as external (AC adapters) or internal (mounted within devices). Power over Ethernet (PoE) integrates data and power delivery over Ethernet cables, enabling efficient power management for networked devices. PoE eliminates redundant cabling, reduces installation costs, and supports flexible device deployment in modern applications like IoT, surveillance, and smart buildings.
| Type | Functional Features | Application Examples |
|---|---|---|
| PoE (IEEE 802.3af) | Up to 15.4W, legacy devices | IP phones, basic surveillance cameras |
| PoE+ (IEEE 802.3at) | Up to 30W, dynamic power allocation | PTZ cameras, video phones |
| PoE++ (IEEE 802.3bt Type 3/4) | 60W (Type 3), 90W (Type 4), 4-pair power | Wireless APs, LED lighting, thin clients |
| UPoE (Cisco Universal PoE) | Up to 60W, proprietary protocol | Digital signage, high-power sensors |
PoE systems consist of Power Sourcing Equipment (PSE) and Powered Devices (PD). PSEs (e.g., switches, injectors) include controllers for power negotiation, isolation transformers, and protection circuits. PDs (e.g., cameras, APs) feature rectifiers, DC-DC converters, and signature detection circuits. External PSUs typically use AC-DC conversion, while internal PSUs integrate DC-DC modules.
| Parameter | Importance |
|---|---|
| Power Output (W) | Determines device compatibility (e.g., 15.4W for VoIP phones) |
| Efficiency (80 PLUS Rating) | Reduces energy waste and operational costs |
| Input Voltage Range | Ensures adaptability to global power standards (100-240V AC) |
| Protection Features | Overcurrent, overvoltage, and short-circuit protection |
| Compliance Standards | IEEE 802.3af/at/bt, UL 62368-1 |
| Vendor | Representative Product |
|---|---|
| Cisco Systems | Catalyst 9200L Series PoE switches |
| Microchip Technology | PoE++ (90W) controllers for PDs |
| TP-Link | TalkTalk L2+ PoE managed switches |
| Dell Technologies | PowerEdge R760xa with integrated PoE+ |
Future developments include higher power delivery (90W+), improved energy efficiency (80 PLUS Titanium), and integration with IoT ecosystems. Standards like IEEE 802.3bt enable multi-gigabit PoE for 5G small cells and edge computing devices. Smart PoE systems with AI-driven power allocation are emerging for dynamic load management in data centers.