sepic converter for power regulation

[nfored]

I have a cree u2 "1a" and a nanjg 105c driver 3.04a constant current. I tried to power this with a 3s lipo through a sepic buck convert tuned to 4.2 volts.

After soldering everything together I powered it on for less than 2 seconds to ensure connections. I was blinded by the awesome of the led. Thats when the awesome stopped that two seconds fried my sepic converter which now only generates heat and no longer produces output voltage.

My question is should I be using something else to step down the voltage? Or should this have been fine and maybe I just got a bad sepic?

I see now that it says the input current max is 2A but I am not sure how I would limit the input? It also says output is 20watts so if my noob understanding of electricity is correct 3.04A x 4.2V = 12.76 or 13watts.


The reason I am not just using a single cell lipo os weight. This is going on a hexacopter for aerial flood light and I would like to avoid the 60 grams of weight to house a dedicated 1s and a cradle. I already have a largely underused 3s on the hex.

Driver
http://m.ebay.com/itm/191062917478?cmd=VIDESC

Led
http://m.ebay.com/itm/201081234658?cmd=VIDESC

Sepic concert
http://m.ebay.com/itm/221406191403?cmd=VIDESC

 

[AnAppleSnail]

You can do some interesting tricks with AMC7135-style drivers like that.

Wire 2 LEDs in series with the driver. Connect this string to the battery and drive the third LED with the driver. Since this is a voltage-dropping driver, all the LEDs in series with the driver will see the same current as the driver and the third LED. At least this lets you add the minimal weight of two more LEDs, rather than extra electronics.

 

[nfored]

That's interesting I would have to add weight in the form of heat sinks for the other 2 leds. However using the existing led as base line, the added weight would be smaller than adding a 1s battery. My thought on this setup would be power draw. If all 3 are seeing 3a then my understanding is that would need 9000mah to give me 1 hour of light.

Thanks for the awesome idea

 

[Toaster79]

3 XM-Ls at 1A will produce more light than one at 3A and they would also need way les heatsinking, meaning your heatsinks would be way smaller and lighter, mounted on the hexacopter they would also have constant airflow.

 

[Conte]

Haha, well, your noob understand of how to calculate wattage is correct, however,

A 3.04a draw from the driver is still greater then the 2a rating of the converter.
And that's 3.04 that it provides to the LED, depending on the efficiency of the driver, it may consume a bit more current then that.
It says 2a input, but you would read that as suggesting that it's output ability will have the same limits.

20watts means what it could handle say, 20volts @ 1 amp, or 10 volts at 2a, but not 1v at 20a, or 2v at 10a even tho' they all work out to the same wattage.


You simply need a higher rated converter, or a lower rated driver. In your case, since you blew the converter, you need to find a higher rated converter.

The only was to limit what you already have is to pull 3 of the 7135 chips off the driver so that it pulls less current from the converter.
Those chips will pass 0.380ma each. That's why there are 8 of them to pass 3.04a to the LED. 5 of them will pass 1.9a to the driver which might still be pushing it depending on the driver efficiency. I would pull 4 for a total of 4 to be safe.

Again, none of this matters if the converter is blown. Mind you the fact that it is generating heat but not output suggests that it might still work, but that you blew a fuse somewhere on the circuit. You may be able to repair it.

 

[Toaster79]

You would be better off buying a decent buck driver like taskled bflex.

 

[nfored]

Thank you so much for all the very detailed response that where very informative and very respectable given my lack of knowledge.


Would this work
http://www.amazon.com/dp/B00GZBWWZO/?tag=cpf0b6-20
Input voltage: DC 4-38V
Output voltageC 1.25-36V continuously adjustable
Output current :0-5A (recommended for use within 4.5A)


Or guess could really bump up to
http://www.amazon.com/dp/B00C4QVTNU/?tag=cpf0b6-20

• Input Voltage: DC 4.5-30V
• Output Voltage: DC 0.8-30V
• Output Current: 0-12A, 100W (if enhance heatsink, can reach 200W)

 

[Conte]

Question on my mind is; What are you building. Whatever it is, it's escalating quickly, hah.

It's going to start to get bulky.
They do make drivers that would do what you want without the need of a converter.

Also, you may .be able to skip the driver even and just Use the converter. The driver is essentially He same thing as that converter just with a fixed output and input.

You're using a regulator to run a regulator.

My guess is 4.5A will be good, but I won't know for sure until my Qlite finally shows up in the mail. Then I can Measure it.

 

[nfored]

Question on my mind is; What are you building. Whatever it is, it's escalating quickly, hah.

It's going to start to get bulky.
They do make drivers that would do what you want without the need of a converter.

Also, you may .be able to skip the driver even and just Use the converter. The driver is essentially He same thing as that converter just with a fixed output and input.

You're using a regulator to run a regulator.

My guess is 4.5A will be good, but I won't know for sure until my Qlite finally shows up in the mail. Then I can Measure it.

I am building a Spot light on my Hexacopter. I started out by using a UF2200 flashlight that I stripped down which worked find until I messed up and ruined the driver with sloppy soldering.

I basically have the copper slug with the reflector strapped to a Servo attached directly under on of the props. I then have a Switch connected to my Receiver that turns on or off the power to the led. I have been seeing a lot of fixed current/fixed voltage converters which I thought might be a better choice.

 

[DIWdiver]

Thank you so much for all the very detailed response that where very informative and very respectable given my lack of knowledge.


Would this work
http://www.amazon.com/dp/B00GZBWWZO/?tag=cpf0b6-20
Input voltage: DC 4-38V
Output voltageC 1.25-36V continuously adjustable
Output current :0-5A (recommended for use within 4.5A)


Or guess could really bump up to
http://www.amazon.com/dp/B00C4QVTNU/?tag=cpf0b6-20

• Input Voltage: DC 4.5-30V
• Output Voltage: DC 0.8-30V
• Output Current: 0-12A, 100W (if enhance heatsink, can reach 200W)

One like this would handle everything by itself: http://www.ebay.com/itm/5A-LED-Driv...209?pt=LH_DefaultDomain_0&hash=item5d4b488079

Taskled drivers would be smaller and lighter though. The bFlex is discontinued, but the b3Flex, h6Flex, H6CC, or HyperBuck would all work well.

 

[Conte]

One like this would handle everything by itself: http://www.ebay.com/itm/5A-LED-Driv...209?pt=LH_DefaultDomain_0&hash=item5d4b488079

Taskled drivers would be smaller and lighter though. The bFlex is discontinued, but the b3Flex, h6Flex, H6CC, or HyperBuck would all work well.

There you go, that looks like exactly what you need.

Dial it in for 3.3v @ 3a and you're rocking.

 

[nfored]

Man that task driver rocks thermal shutdown and every thing. I am sold you guys rock.