Low power, high brightness, long cable solution combining PoE and LED

introduction

Compared with bulbs or fluorescent tubes, LEDs are not only smaller in size, but also more directional in light, and can be driven with low voltage DC. IEEE-approved Power over Ethernet (PoE) can provide power using standard Ethernet cables, and these cables also provide network services. The PoE power supply can deliver up to 15W of power over a cable of up to 100 meters. Distributing low-power, high-brightness light at the end of a long cable is naturally not a 48 VDC. In addition, for LED drivers, the use of DC-DC converters is better than AC-DC converters because the latter requires more components and space and is less efficient. In fact, both LED and PoE seem to be born for each other. Together with PoE and high-power LEDs, you can create an impeccable solution.

Targeted solution

IEEE 802.11af specifies a maximum power of 15W at the power source. At a typical voltage of 48V, the output current is 350mA.

However, the CAT5 Ethernet cable itself is not designed for transmission applications, so it is generally only a thinner 24-wire copper wire. Therefore, long-distance power loss (PoE cable lengths up to 100 meters) can reach 2W, leaving only about 13W for the load. To solve this problem, you need to use 10 1W LEDs to form a light source and connect the bulb to the power supply with a 12-foot CAT5 cable. In this way, the LED's lighting performance can be greatly improved, the standard 1W device can emit 50 lumens per watt, and the best device can reach 100 lumens per watt, and will continue to improve.

1W power LEDs from North American LED manufacturer Cree use surface mount technology in LED dies, with a lens that provides a lambertian viewing angle and a die-cooled copper sleeve with a low thermal resistance interface . These models are 1W LED devices in the XLamp series and are available in seven colors: red, red-orange, yellow, green, cyan, blue, and ink blue, and three white color temperatures: cool white (5000K to 10000K). Soft white (3500K to 5000K) and warm white (2600K to 3500K). The PoE “Feeder” is a Power Supply Unit (PSE) that extracts data from an Ethernet cable and adds power to an idle twisted pair. A feeder with eight output ports is available from several telecommunications equipment manufacturers, so the lighting system under this “scenario” features a PoE LED light for each color, at any given time. Power is supplied to eight LED lights.

Figure 1 Schematic diagram of the PoE LED lamp