I want to make a 100W high power LED headlight for bike, but the problem is that LED releases a lot of heat, and I'm using a 150W boost converter to convert 12V to 30V ( minimum operating voltage of 100W LED), to reduce the heat I have to reduce the current to 1A(from battery it is 6A), and for that I'm thinking to use l7812 which is a 12V linear voltage regulator but, it will not be able to handle that much amount of current I think so. Can I ue linear voltage regulator or sothing else? I'm experienced with printing PCBs using toner transfer and also with soldering. I'm confused what to do please suggest me a solution LED specs- 100W 32-35V 3000mA Genesis's 30Mil
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\$\begingroup\$ Why do you want a boost converter and a linear regulator? Why 30V? Obviously you're aware that if you have 1A at 30V that's not 100W any more? What's the power supply for all this, batteries? \$\endgroup\$– pjc50Jul 28, 2015 at 10:01
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\$\begingroup\$ If I read your question as it is written now, you boost 12V to 30V and are asking how to solve turning that back into 12V with an LM78-series without the heat. I'd think not boosting the original 12V would accomplish that. \$\endgroup\$– AsmyldofJul 28, 2015 at 10:02
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\$\begingroup\$ Boost converter because 100W led operates on 30V \$\endgroup\$– Tanishq JaiswalJul 28, 2015 at 10:03
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\$\begingroup\$ Can we get LED specs? How did you get that the battery you will draw 6A? That is entirely dependant on the load. \$\endgroup\$– Josh JobinJul 28, 2015 at 10:12
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\$\begingroup\$ When I connect the LED with boost converter in series with my multimeter then I get that reading \$\endgroup\$– Tanishq JaiswalJul 28, 2015 at 10:15
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When you measured your LED drawing 6 A from a 30 V supply (if I understand right), that was 180 W. Your LED would not last long at that power. You do need a way to limit the current.
Best would be to find a 100 W current-regulated boost LED driver instead of a voltage-regulated boost regulator. Then you don't need any other components.
If you want to use a linear regulator, get a low-dropout regulator configured as a current and not as a voltage regulator. Then set the boost voltage as close to the LED voltage as the regulator dropout voltage will allow. If it's only one or two volts and 1 A, then only a couple Watts will be dissipated in the linear regulator, which is OK with an appropriate heatsink.
A word of caution about mounting a 100 W LED on a bike (I assume you mean bicycle): you really want to make sure that you have appropriate optics and diffusers in front of that LED so that the light comes from a large surface area (like car headlights) and not from a very small, 1 cm\$^2\$ point source. Otherwise you will badly blind anyone coming towards you, maybe even damaging their retinas, possibly causing an accident which may also involve you.
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\$\begingroup\$ Thanks for your answer, but I wonder can I use mosfet to do so? And it is the for the headlight of motorcycles, and I'm using collimator lens to focus the light and end the risk \$\endgroup\$ Jul 28, 2015 at 11:36
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1\$\begingroup\$ For a MOSFET-based circuit you can have a look here: instructables.com/id/Circuits-for-using-High-Power-LED-s/… \$\endgroup\$– DamienDJul 28, 2015 at 11:41
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\$\begingroup\$ Thank you once again! Exactly found out what I was looking for \$\endgroup\$ Jul 28, 2015 at 12:42