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June 26, 2012

Driving COB Led

COB, (Chips on Board) , multi LED (light emitting diode)chips are packaged together as one lighting module. When it light up, it looks like a lighting panel. COB LED is multi chips packaged, it can 10 times more increase lighting area,so it avoid uncomfortable glare by the maximum extent.By now, for small size chip, some famous LED chip manufacturer can reach 249lm/watt @ 20mA. But big size LED chip can only reach 161lm/watt @350mA.The light efficacy decrease when chip size is bigger. Also when LED driver increase current to LED, the light efficacy per watt is even low.COB technology provides significant advantages over surface mount technology (SMT) components in the design with better temperature management, smaller size of lumen packages and lower production costs. In general the life span of COB LED can be 40000-50000 hours.

COB led as shown above compose of seven (7) led in series and requires again a constant current driver, from tha specification found all over the net requires 12v driving them at 300mah of current.From the previous page that can be found here PROJECT LED HEADLIGHT . I still use the same DIY led driver so that the voltage of the led in series will float depending on the forward voltage of each led and the current to the led will then remain constant.
Actually, there are so many led driver being offered all over the net, i myself  wanted to have one of them at least, but due to lack of resources, i just make my own out from those datasheet of every semiconductor that performs the same function for led lighting. And from the schematic, will make PCB for those components to make the circuit work. Pre testing is required not to waste every component.

Schematic of the led driver can be found here led boost constant current driver . For Pcb, you really have to make it on your own since i am just making mine using pen. But to make it easier, there are lots of downloadable PCB software available for all of you to test.

COB led connected to the led current driver (sorry for the photo, grayscale color :(

Beam shot was taken at a 90 degrees, note that the surrounding do not have any other lights on, only the COB led itself..hmmm too powerful for me, wide beam actually cover lots of area than my previous attempt using seven (7) x 3 watts power led in series.

Shot taken now at 45 degree from the actual beamshot, too much glare is obvious, (disclaimer), when doing such experiments on high power leds, avoid prolong exposure of the eye to the actual beam, you may temporary have a blur vision after, and may cause eye disorder.

Actual beamshot towards the floor at my garage, very interesting that due to the wide cover area of the led the beamshot was as if i am using a CCFL energy saving lamp, so that is why manufacturers use it for household lighting. :)


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