With the rapid development of technologies such as the Internet of Things (IoT), Big Data, 5G, and Artificial Intelligence, industrial automation and Industrial IoT have become the emerging trends. The demand for industrial Ethernet switches is rapidly expanding, especially in industrial automation applications like Manufacturing Execution Systems (MES), Production Control Systems (PLC), and Process Control Systems (FCS), where they are widely used.

Ethernet Power over Ethernet (PoE) Applications

In most cases, terminal devices require DC power, and they are often installed high up on ceilings or outdoors where suitable power outlets are scarce. Even when outlets are available, it can be difficult to place AC-DC converters near the terminal equipment. Therefore, the demand for powering through the Ethernet itself has become increasingly urgent, and Power over Ethernet (PoE) is the perfect solution.

Figure 1: Common PoE Power Supply Applications

PoE is a wired Ethernet power supply technology that uses the same Ethernet cables for data transmission and DC power supply. PoE provides reliable, simple connections and unified standards. As shown in Figure 1, more and more industrial IoT devices are using PoE for power, such as IP phones, network video surveillance, and wireless Ethernet devices.

PoE Switch Power Management Architecture

PoE switches are commonly used devices that provide PoE power and are typically referred to as Power Sourcing Equipment (PSE). They use PSE controller chips inside, which supply power according to the IEEE PoE standards. The power supply voltage is typically in the range of DC 44V–57V, usually 48V or 53V, and is often powered by an AC-to-DC adapter. There are three main types of PoE switch adapters:

1. 12V Adapter
   Uses a 12V adapter to power the device, stepping the 12V up to 48V/53V to supply power to the PSE chip.

2. 48V/53V Adapter
   Uses a 48V/53V adapter to directly provide power to the PSE chip. However, a step-down IC is required to reduce the voltage from 48V/53V to 12V, 5V, 3.3V, etc. In high-power scenarios, the voltage is first reduced to 12V, and then a secondary step-down converter is used to convert to 5V, 3.3V, etc.

3. 48V/53V + 12V Adapter
   The 48V/53V adapter serves as input to the PSE chip, while the 12V adapter uses a step-down converter to reduce to 5V, 3.3V, etc.

n addition to the adapters, some PSE chips integrate LDOs that can directly support 48V/53V as the working voltage, while others require a step-down IC to reduce the voltage to 3.3V for powering. Furthermore, as the number of outputs in PoE switches increases, and transmission speeds range from 100Mbps to 1Gbps, the required power output also increases, typically using high-current step-down ICs.

SCT Solutions

As discussed, PoE switch power solutions often involve:

1. Boost controllers with voltage ranges up to 65V.
2. Buck converters with input voltage ranges of 60V and output currents of 1A/2A/3A.
3. Mid-range 18V Buck converters (2A/3A output).

For high-power PoE switches, a primary power input voltage range of 60V is used with high-current buck controllers, while secondary power is provided by mid-range 18V converters (5A/6A/8A output).

SCT provides a wide range of power solutions for PoE switches, suitable for any front-end adapter, including Boost controllers, Buck controllers, and Mid-to-high voltage Buck converters. The product list for PoE switch power management applications is shown in Figure 2.

Figure 2: PoE Switch Power Product Application Selection Table