Building simple constant current power LED driver

Normally when we need to drive low power LEDs we don’t care much about power losses. What we do we add a current limiting resistor and that’s enough. For instance for 20mA LED we choose between 300Ω-1kΩ resistor when powering from 5V. But different situation is with power LEDs. The currents are much bigger here like 1A and more. Adding resistor to limit the current isn’t an option, because power losses become significant. Here you need a constant current driver to drive it safely without wasting energy. It happens that I have Cree XR-E Q5 XLAPM-7090 LED lying around. It requires 3.7V driving voltage and can take up to 1A current. There are several light intensities given at specific currents:

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LED lamps will replace light bulbs in near future

Seems this can be true. Faiz Rahman who is a nano electronics researcher at Glazgow university states that low-energy bright LED light Bulbs are almost here. As matter of fact LEDs are very energy efficient, but fact is that about 70% of electrical energy is converted to light, and only about 20% of it getting out. The rest of light is trapped inside semiconductor due to high refractive index of LED-air surface. But as Faiz says by making LEDs to let more light out their brightness can be compared to ordinary light bulbs. How to make this happen? This can be done by making series of holes on the surface of LED. Rahman has already made several LED prototypes where holes on surface are about 200nm in diameter (400 times narrower than human hair) and 100nm deep. As LED chip is about 0.3×0.3mm there is enough space for hundreds of…

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