What standard does Hikvision adopt for poe-powered cameras?

Use IEEE? 802.3af protocol and IEEE 802.3at protocol.

1、IEEE？ 802.3af

IEEE？ 802.3af( 15.4W) became the first PoE power supply standard, and stipulated the Ethernet power supply standard, which is the mainstream implementation standard of PoE application now.

IEEE began to formulate this standard in 1999, and the earliest participating manufacturers were 3Com, Intel, Powersine, Nortel, Mitel and National Semiconductor. However, the shortcomings of this standard have been restricting the expansion of the market.

Until June 2003, IEEE approved 802. The 3af standard clearly specifies the matters of power detection and control in remote systems, and specifies the way that routers, switches and hubs supply power to IP phones, security systems and wireless LAN access points through Ethernet cables. The development of IEEE 802.3af involves the efforts of many company experts, which also enables the standard to be tested in all directions.

Typical Ethernet power supply system. Keep the Ethernet switch equipment in the wiring cabinet, and use the power hub (mid-span hub) to provide power for the twisted pair of LAN. At the end of twisted pair, the power supply is used to drive telephones, wireless access points, cameras and other devices. To avoid power failure, you can choose UPS.

2、IEEE 802.3at

IEEE802.3at(25.5W) came into being in response to the demand of high-power terminals. IEEE 802.3AT (25.5W) is compatible with 802.3af, which provides greater power demand and meets new requirements.

In order to comply with the IEEE 802.3af specification, the power consumption of PoE on power receiving equipment (PD) is limited to 12.95W, which is enough for traditional IP phones and webcams. However, with the emergence of high-power applications such as dual-frequency access, videophone and PTZ video monitoring system, the power supply of 13W obviously cannot meet the demand, which limits the application scope of Ethernet cable power supply. In order to overcome the limitation of PoE on power budget and push it to new applications, IEEE has set up a new task force to explore ways to improve the power limitation of this international power standard.

IEEE802.3？ In order to evaluate the possibility of implementing IEEE802.3at technically and economically, the working group established the PoEPlus research group in June 2004.

Later, in July 2005, the plan to set up an investigation committee of IEEE 802.3at was approved. The new standard, named Power-Over-Ethernet Plus (POEP) IEEE 802.3at, defines devices with power requirements higher than 12.95W as four categories (this level is described in IEEE 802.3af, but reserved for future use), and can extend the power level to 25W or higher.

Extended data:

Ethernet power supply system is mainly composed of PTL, PSE and PD. The basic situation and performance of the system should include the composition, structural layout and working mode of the system, the transmission performance of PTL in the system, the load capacity of PSE, the number of PD receiving power supply and the overall performance parameters of the power supply system that can be achieved.

According to the overall performance requirements of the power supply system, the standard specifies the performance of all components in the power supply system, namely PTL and PSE, and the performance of power receiving equipment. On the contrary, only when the performance of these components in the power supply system meets the requirements of the standard, the performance index of the power supply system can meet the overall performance requirements of the IEEE 802.3af standard specification.

IEEE began to implement standardization in 1999. Early advocates included 3Com, Intel, PowerDsine, Nortel, Mindy and National Semiconductor. These companies realize that people need to supply power through Ethernet cables, and there are a large number of proprietary applications in the market, but the lack of standards hinders the development of the market.

Experts from many companies participated in the process of IEEE standardization, which also benefited the specification, because it examined problems from many different angles. In addition, the draft specification was sent to all IEEE members for approval by voting. During this period, IEEE members can raise and negotiate to resolve any objections.

The standardization process of IEEE802.3af has now ended. The IEEE Standards Committee formally approved the standard on June 12, 2003.

There are many products on the market that claim to meet the standard before the standard officially appears. Because in the months before June 2003, the draft specification has been changing, and some final changes were made when the standard was approved, some products on the market may not actually meet the final standard, so we should be cautious when dealing with these products. Generally speaking, recently designed products will reasonably meet the final standards.

The main equipment powered by Ethernet is PSE, which is responsible for detecting, grading and controlling the power supply to meet the power supply requirements of 802.3af PD in the network. In the detection process, PSE measures two V-I points and calculates the resistance according to the slope between them to judge the * * * mode terminal of the port. As long as the difference between the two voltages is greater than 1V and both are in the range of 2.8V~ 10V, PSE can measure the forced current or forced voltage, so there is room for the series diode of PD.

For Ethernet power supply, detection is very important, because it can ensure that the DC voltage of 48V is only applied to the effective PD, and it will never damage those devices that do not need to receive 802.3af power supply. Like other parts of Ethernet power supply, the * * * mode suppression of Ethernet cable is not conducive to detection. PSE must suppress the 50/60Hz signal by accumulating multiple AC cycles, and the detection must be completed within 500 ms. After the detection is successful, PSE will provide 15.5V-20.5V to the port, and put PD in hierarchical mode.

Before grading (measuring port current), PSE will give PD 10ms a stable time. In order to maintain reasonable power consumption, the classification must be completed within 75 ms If PSE can provide the power required for PD level, PSE will provide power for PD. For power requirements, please refer to the column "Minimum PSE Power" in the table.

If PSE can provide 16W power to each port, you can choose to skip the classification completely. Classification can make more effective use of power supply and reduce power supply cost, so most PSEs should adopt classification. Regardless of whether PD is classified or not, PSE must complete effective detection within 400ms before it can supply power to PD, otherwise, the waiting time of PSE will be too long, which will damage the Ethernet equipment plugged in the original PD position and not needing power supply.

References:

Baidu encyclopedia IEEE802.3af