Research Of Power Supply Controller For Power Over Ethernet

In recent years, with the widely use of VoIP and WLAN, the technology of PoE has been pressed for supplying power, which can enable CAT5 Ethernet cable to carries both power and data to each device. PoE is an innovative technology which is widely applied to more and more powered device such as IP phone,IP Camera and wireless access point. Current PoE standard is IEEE 802.3af.In the current design of power over Ethernet system, power source equipment (PSE) is divided into two modules: power management module and monitoring module. Ethernet power management chip is used to detect and classify power device (PD). On the other hand, MCU is used to controll Ethernet power management chip, thus to realize the monitor of the working state of PD.This paper improves the design of the power source equipment after deep analysis of the PoE system. This paper proposes that power management module and monitoring module can be achieved by MCU simultaneously. This is to say, MCU can not only detect and classify power device, but also monitor the working state of PD. MCU integrates the function of traditional power management chip and the monitoring function, thus simplifying the design and saving the cost.This paper designs experimental system to verify the feasibility of the improved design. The experimental system consists of power source equipment and power device. Power source equipment concludes power supply, MCU and controll circuit. The key point of the design of the power source equipment is the program design of the MCU, which concludes the power management and monitor program. In addition, monitor interface of PC is designed. Thus, PC can monitor the working state of power device through MCU. The function of PD circuit is to provice reasonable load for the verification of MCU. It consists of the design of the interface chip LTC4267 and DC/DC converter.At last, experimental result is given. The result shows that the controller designed can realize power management and monitor function simultaneously.