Buck-boost, 3v to 6.4v in, white LED drive out, 3A, how to handle the high end of Vin with a buck-boost

lslonim

Other Parts Discussed in Thread: LM3550, LM3409, LM3410

I need to run a while LED (output voltage range from 2.5-4.5v 4A surge, 3A steady state) from a battery source that can range from 3v to 6.4v in. So it's a buck-boost. I haven't been able to find a buck-boost that has a Vin higher than 5, with an absolute max of 5.5. The 6.4v is going to drop under load but it will still be above 5.5. I was wondering if I should just put a load resistor in series and bypass it when the Vin drops enough. Does anyone have any suggestions?

Thanks,

Lloyd

over 5 years ago

0 Sean Zhou over 5 years ago

TI__Mastermind 22745 points

Hi Sir,

The most similar device from our product line is the LM3550, but the recommend supply voltage range is from 2.5V to 5.5V. Maybe you can add a diode between power supply and LM3550

Sean

0 lslonim over 5 years ago in reply to Sean Zhou

Expert 1710 points

Sean,

Thanks for replying. The chip you mentioned can only do 200ma continuous, can you suggest one that can do 3A continuous?

Thanks,

Lloyd

0 Sean Zhou over 5 years ago in reply to lslonim

TI__Mastermind 22745 points

Hi Lloyd,

I don't have the good recommendation for such high current LED driver, I will forward to another product line, maybe they have some good suggestions.

Sean

0 Irwin Nederbragt over 5 years ago in reply to Sean Zhou

TI__Mastermind 28655 points

Hello Lloyd,

Unfortunately we have the same limitation. The LM3410 is the closest part our group has and it is limited on the input to 5.5V as well. It also cannot handle 3A. You could develop a circuit to limit the input but that will cause quite a bit of loss at 3A output. A resistor will not work since it will pull the input up to 6.4V when the load is off. You could also look at using a voltage output boost to increase the input voltage then use the LM3409 as a buck LED driver.

Best Regards,

0 lslonim over 5 years ago in reply to Irwin Nederbragt

Expert 1710 points

Thanks guys, I appreciate the help.

Lloyd

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Buck-boost, 3v to 6.4v in, white LED drive out, 3A, how to handle the high end of Vin with a buck-boost