POE Switch
PoE is a wired Ethernet power supply technology, which is used for data transmission and has the ability of DC power supply. PoE power supply has the advantages of reliability, simple connection, and unified standards. More and more industrial IoT devices are adopting PoE power supply, such as IP phones, network video surveillance, and wireless Ethernet devices.应用框图
With the rapid development of technologies such as the Internet of Things, big data, 5G, and artificial intelligence, industrial automation and industrial Internet of Things have become development trends. The demand for industrial Ethernet switches is rapidly expanding, and the demand is growing rapidly, especially in industrial automation application scenarios such as manufacturing execution systems (MES), production scheduling systems (PLC), and process control systems (FCS).1、 Ethernet powered PoE applications
In most cases, terminal devices require direct current power supply, and terminal devices are usually installed on ceilings or outdoors that are relatively high from the ground. It is difficult to have suitable power sockets nearby, and even if there are sockets, the AC/DC converters required by terminal devices are difficult to have a location to install; Therefore, the demand for power support through Ethernet itself is becoming increasingly urgent, and Ethernet powered PoE precisely solves this problem.
PoE is a wired Ethernet power supply technology, which is used for data transmission and has the ability of DC power supply. PoE power supply has the advantages of reliability, simple connection, and unified standards. As shown in Figure 1, more and more industrial IoT devices are adopting PoE power supply, such as IP phones, network video surveillance, and wireless Ethernet devices.
2、 PoE Switch Power Management Architecture
A PoE switch is a commonly used device for providing PoE power, commonly known as a Power sourcing Equipment (PSE). It uses a PSE controller chip internally, and according to the three PoE standards published by the IEEE Standards Committee, the power supply voltage range is 44V~57V DC, usually 48V or 53V, and is usually powered by an AC to DC adapter. The adapters of common PoE switches are divided into three types:
1. 12V adapter
To use a 12V adapter for power supply, it is necessary to increase the 12V voltage to 48V/53V to power the input of the PSE chip.
2. 48V/53V adapter
Using a 48V/53V adapter for power supply can directly provide 48V/53V power to the PSE chip, but requires a step-down IC to reduce the 48V/53V to voltages such as 12V, 5V, 3.3V, etc. For high-power scenarios, the voltage is usually first reduced to 12V; Then use a secondary power supply medium voltage high current or low current step-down converter to reduce the voltage to 5V, 3.3V, etc.
3. 48V/53V+12V adapter
The 48V/53V adapter serves as the input power supply for the PSE chip, while the 12V adapter uses a medium and low voltage high current or low current step-down converter to reduce the voltage to 5V, 3.3V, and other voltages.
In addition to adapters, in the power architecture of POE switches, some PSE chips are integrated with LDO, which can directly support 48V/53V as the working voltage, while others require a step-down IC to reduce to 3.3V for power supply; At the same time, the number of output ports of POE switches increases from few to many, the transmission speed increases from hundreds to gigabits, the output power increases from small to large, and the required power supply current gradually increases. Usually, high current buck ICs are used.
3、 Solution Analysis
In summary, for the power scheme of POE switches, the following are usually used:
1) Boost controller with a range of up to 65V;
2) A step-down converter with an input voltage range of 60V-1A/2A/3A;
3) Medium voltage 18V-2A/3A step-down converter.
For high-power POE switches, a step-down controller with a primary power supply input voltage range of 60V and high current will also be used, and a step-down converter with a secondary power supply medium voltage of 18V-5A/6A/8A will be used.
SCT can provide a wide range of power solutions for PoE switches suitable for any front-end adapter, including Boost Controller, Buck Controller, and Mid High Voltage Buck Converter. The list of power management products for POE switch applications is shown in Figure 2.
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