The use of Power over Ethernet (PoE) powered by Power over Ethernet is growing (Figure 1). In fact, since the standard specification "IEEE802.3af" was established in PoE in June 2003, the scope of application has begun to expand. The IEEE802.3af has a maximum voltage of 57V, and one port can output 15.4W of power and can supply 12.95W to the power receiving side. Later, in June 2009, a "IEEE802.3at (PoE+)" standard with a port that can be powered by 25.5W was developed, and the support model was further increased. At present, the use of IP phones, surveillance cameras and wireless LAN access points in office buildings is increasing. 
Recently, PoE technology that can supply more than 25.5W of power specified by IEEE802.3at has been put into practical use. Among them, the "LTPoE++" of Linear Technology, Inc., which can supply about 100W of large power. One port on the power supply side can output 125W and receive 90W of power.
IEEE 802.3af and IEEE 802.3at utilize two of the four pairs of twisted pairs in the Ethernet cable. LTPoE++ improves the supply of electricity by using all four pairs (Figure 2). As power is increased, the company has introduced a function of detecting voltage and current values ​​in the power supply control IC in order to improve reliability. In addition, to reduce the amount of heat generated, an external standard that selects a low-loss MOSFET is used. According to Linear Technology, as power increases, it can be used in small base stations for mobile communications. It is expected that small base stations equipped with LTPoE++PoE control ICs will be unveiled from the end of 2012 to 2013.
No need for AC-DC converter
Among the applications that have expanded with the increasing power of PoE, LED lighting has been the most concerned. Because PoE has two major advantages, it is suitable for driving LED lighting fixtures.
First, there is no need to drive the AC-DC converter required for LED illumination. LED lighting products are more efficient than bulbs and fluorescent lamps, and have a long life. Therefore, in order to reduce environmental load, LED lighting has begun to replace other lighting products.
LED lighting is generally different from previous fluorescent lamps and is driven by DC. Therefore, an AC-DC converter must be used, and the AC-DC converter "sometimes causes the LED illumination to flicker" (Cisco Systems Japan). PoE uses DC power, so it is easy to avoid such problems.
Another advantage of the PoE drive is that it can send and receive control signals. PoE is easy to control the brightness of the LED by exchanging data signals, and it is expected to reduce power consumption.
With these two advantages, some pioneering companies have begun to promote the practical use of PoE systems that support the driving and control of LED lighting. The first to take action is the US Cisco system.
The company has developed a "Universal PoE (UPoE)" that can supply 60W of power on one side of the power supply side and 51W of power on the power receiving side. UPoE-enabled products such as network switches have been released in the fall of 2011. Cisco developed the LED lighting system that utilizes the UPoE and imported it into the Osaka office of its Japanese company, Cisco Systems Japan (Figure 3).
The system was proposed in Japan and was jointly developed by Cisco Systems Japan and Japanese companies. It can be said that this is a product that can only be born in Japan that promotes the popularity of LED lighting. Among them, the DEP and three-machine industrial control server and the DEP LED lighting DC-DC converter are utilized.
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