CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority of Taiwanese Patent Application No. 110112754, filed on Apr. 8, 2021.

FIELD

The disclosure relates to power-over-Ethernet (PoE) techniques, and more particularly to a PoE device and a PoE system using the same.

BACKGROUND

Referring toFIG. 1, a conventional security monitoring system includes a computer91, a local area network (LAN) hub92and multiple Internet Protocol (IP) cameras93. The LAN hub92is coupled to the computer91and the IP cameras93through multiple LAN cables. Images captured by each of the IP cameras93are transmitted first to the LAN hub92and then to the computer91. Electric power required for operation of each of the IP cameras93is supplied by a respective one of multiple adapters94. It costs money to purchase the adapters94and labor is also required to wire the adapters94respectively to the IP cameras93.

SUMMARY

Therefore, an object of the disclosure is to provide a power-over-Ethernet (PoE) device and a PoE system using the same. The PoE system can alleviate the drawback of the prior art.

According to an aspect of the disclosure, the PoE device includes a first interface, a second interface, a first switch, a second switch, a first rectifier, a second rectifier, a third rectifier, a fourth rectifier, a switch controller, a powered device (PD) controller, a third switch and a power sourcing equipment (PSE) controller. The first and second interfaces are adapted to be respectively coupled to a first network cable and a second network cable. The first switch has a plurality of first terminals that are coupled to the first interface, a plurality of second terminals, a plurality of third terminals, and a control terminal that is to receive a first control signal. The second switch has a plurality of first terminals that are coupled to the second interface, a plurality of second terminals, a plurality of third terminals, and a control terminal that is to receive a second control signal. Each of the first and second switches normally stays in a first state where the first terminals thereof are respectively coupled to the second terminals thereof, and, when being actuated by the corresponding one of the first and second control signals, stays in a second state where the first terminals thereof are respectively coupled to the third terminals thereof. The first rectifier is coupled to the first interface and the second terminals of the first switch. The second rectifier is coupled to the second interface, the second terminals of the second switch, and the first rectifier. The first rectifier, when receiving electric power from the first network cable through the first interface or through the first switch and the first interface, rectifies the electric power received by the first rectifier, and the second rectifier, when receiving electric power from the second network cable through the second interface or through the second switch and the second interface, rectifies the electric power received by the second rectifier, so that an input voltage is provided at a common node of the first and second rectifiers. The third rectifier is coupled to the second terminals of the first switch, and, when receiving electric power from the first network cable through the first switch and the first interface, rectifies the electric power received by the third rectifier to generate a first rectified voltage. The fourth rectifier is coupled to the second terminals of the second switch, and, when receiving electric power from the second network cable through the second switch and the second interface, rectifies the electric power received by the fourth rectifier to generate a second rectified voltage. The switch controller is coupled to the third and fourth rectifiers to receive the first and second rectified voltages, and is further coupled to the control terminals of the first and second switches. The switch controller generates the first and second control signals for receipt by the control terminals of the first and second switches and an enable signal based on the first and second rectified voltages. The PD controller is coupled to the common node of the first and second rectifiers to receive the input voltage, and is to output the input voltage to serve as a supply voltage that supplies electric power required for operation of the PoE device. The third switch has a first terminal that is coupled to the common node of the first and second rectifiers, a second terminal, and a control terminal that is coupled to the switch controller to receive the enable signal. Based on the enable signal, the third switch transitions between a conduction state, where the first and second terminals thereof are coupled to each other, and a non-conduction state, where the first and second terminals thereof are not coupled to each other. The PSE controller is coupled to the second terminal of the third switch and the third terminals of the first and second switches, is to receive the input voltage from the common node of the first and second rectifiers through the third switch, and is to output the input voltage to serve as an output voltage for receipt by the third terminals of each of the first and second switches. The switch controller, when determining that the PoE device receives electric power from the first network cable, generates the first and second control signals and the enable signal in such a way that the first switch, the second switch and the third switch respectively stay in the first state, the second state and the conduction state, so that the output voltage is generated, and supplies electric power to the second network cable through the second switch and the second interface. The switch controller, when determining that the PoE device receives electric power from the second network cable, generates the first and second control signals and the enable signal in such a way that the first switch, the second switch and the third switch respectively stay in the second state, the first state and the conduction state, so that the output voltage is generated, and supplies electric power to the first network cable through the first switch and the first interface.

According to another aspect of the disclosure, the PoE system includes a plurality of PoE devices and a hub that are coupled in a ring configuration through a plurality of network cables. The hub is coupled to two of the network cables, and provides electric power to at least one of said two of the network cables. Each of the PoE devices includes a first interface, a second interface, a first switch, a second switch, a first rectifier, a second rectifier, a third rectifier, a fourth rectifier, a switch controller, a PD controller, a third switch and a PSE controller. The first and second interfaces are respectively coupled to one and another one of the network cables. The first switch has a plurality of first terminals that are coupled to the first interface, a plurality of second terminals, a plurality of third terminals, and a control terminal that is to receive a first control signal. The second switch has a plurality of first terminals that are coupled to the second interface, a plurality of second terminals, a plurality of third terminals, and a control terminal that is to receive a second control signal. Each of the first and second switches normally stays in a first state where the first terminals thereof are respectively coupled to the second terminals thereof, and, when being actuated by the corresponding one of the first and second control signals, stays in a second state where the first terminals thereof are respectively coupled to the third terminals thereof. The first rectifier is coupled to the first interface and the second terminals of the first switch. The second rectifier is coupled to the second interface, the second terminals of the second switch, and the first rectifier. The first rectifier, when receiving electric power from said one of the network cables through the first interface or through the first switch and the first interface, rectifies the electric power received by the first rectifier, and the second rectifier, when receiving electric power from said another one of the network cables through the second interface or through the second switch and the second interface, rectifies the electric power received by the second rectifier, so that an input voltage is provided at a common node of the first and second rectifiers. The third rectifier is coupled to the second terminals of the first switch, and, when receiving electric power from said one of the network cables through the first switch and the first interface, rectifies the electric power received by the third rectifier to generate a first rectified voltage. The fourth rectifier is coupled to the second terminals of the second switch, and, when receiving electric power from said another one of the network cables through the second switch and the second interface, rectifies the electric power received by the fourth rectifier to generate a second rectified voltage. The switch controller is coupled to the third and fourth rectifiers to receive the first and second rectified voltages, and is further coupled to the control terminals of the first and second switches. The switch controller generates the first and second control signals for receipt by the control terminals of the first and second switches and an enable signal based on the first and second rectified voltages. The PD controller is coupled to the common node of the first and second rectifiers to receive the input voltage, and is to output the input voltage to serve as a supply voltage that supplies electric power required for operation of the PoE device. The third switch has a first terminal that is coupled to the common node of the first and second rectifiers, a second terminal, and a control terminal that is coupled to the switch controller to receive the enable signal. Based on the enable signal, the third switch transitions between a conduction state, where the first and second terminals thereof are coupled to each other, and a non-conduction state, where the first and second terminals thereof are not coupled to each other. The PSE controller is coupled to the second terminal of the third switch and the third terminals of the first and second switches, is to receive the input voltage from the common node of the first and second rectifiers through the third switch, and is to output the input voltage to serve as an output voltage for receipt by the third terminals of each of the first and second switches. The switch controller, when determining that the PoE device receives electric power from said one of the network cables, generates the first and second control signals and the enable signal in such a way that the first switch, the second switch and the third switch respectively stay in the first state, the second state and the conduction state, so that the output voltage is generated, and supplies electric power to said another one of the network cables through the second switch and the second interface. The switch controller, when determining that the PoE device receives electric power from said another one of the network cables, generates the first and second control signals and the enable signal in such a way that the first switch, the second switch and the third switch respectively stay in the second state, the first state and the conduction state, so that the output voltage is generated, and supplies electric power to said one of the network cables through the first switch and the first interface.

