| Ethernet is mostly used in data transmission previously, so that the Ethernet device must work with own battery or external supply adapter. The standard which Ethernet can also transfer DC power supply in data transmission line is defined in IEEE 802.3af, promulgated in June, 2003, and it expands new area for Ethernet application, and the technique of PoE (Power over Ethernet) becomes the novel and potential area with good practical future.The background and significance of Ethernet power supply is introduced in this paper firstly. Correspondingly the overview of PoE development is presented, including the characteristics and function of product and control chip of relative semiconductor company.Secondly, the standard PoE system is designed based on the comprehension about the feature of Ethernet signal and high-frequency network transformer. Following IEEE 802.3af standard, the complete design strategy of PoE system containing PSE (Power Sourcing Equipment) and PD (Power Device) is proposed by means of novel control management chip of power sourcing. In addition, hardware design, idea of software flow control and relative experimental record are presented.Finally, because the power problem, which the maximum supply power is 13W in IEEE 802.3af standard, restricts the application range of Ethernet power supply. Based on previous research, a novel PoE system plan, transformer parallel mode is proposed in power expansion. The PoE system after power expansion is designed according to the previous progress, and the suitable design parameters suitable for expanded system is given. |
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