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So I'm currently trying out a project using a USB power source to drive an Arduino Nano board and several 3W LEDs.

Specific conditions the project needs to fulfill are:

  • The power supply's standard output is restricted to 5V/1A.
  • The LEDs and arduino need to be powered in parallel
  • Prefer to keep the overall size of the end product small (perhaps around the size of a flashlight).

So far I've managed to rule out powering the arduino with the on-board USB input and instead use a power supply only USB cable.

I currently plan to use at least one of these DC-DC boost converter modules to boost the 5V/1A output to at least 12V/1A before futzing with anything else.

The questions I have are:

  1. Is it possible to place a couple of these boosters in a series to increase the voltage still further?
  2. What would I need to add to supply 1A of current to all of the LEDs off of the single output?

And if there's anything I'm missing, can someone point out the errors?

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    \$\begingroup\$ If you look at the power of your supply: 5*1=5W it will never be able to power the 3*3W. You could turn down the brightness. You will also not be able to create 12V/1A from 5V/1A, without another source... \$\endgroup\$ – Douwe66 Feb 7 '17 at 9:17
  • \$\begingroup\$ Other than the error that you want a DC-DC switcher to magically convert a 5 W power input to a 12 W power output? If you need more voltage then use a power supply with a higher voltage output. Every supply will have an efficiency of 80-90% so if you have 5 V/1 A input then at 12 V the most you will get is 0.9*(5/12) = 375 mA \$\endgroup\$ – Andrew Feb 7 '17 at 9:24
  • \$\begingroup\$ Yeah...sorry, my brain wasn't properly working when I started this line of thought because I had people wanting to use a USB powerbank to drive the whole assembly. Side note: Given that USB-C allows up to a 15W supply (5V/3A?) it would be possible, if using a USB-C compatible powerbank to setup a way to drive both the Nano and the LEDs, right? \$\endgroup\$ – Noboru Akimoto Feb 8 '17 at 6:36
  • \$\begingroup\$ A 3W LED is a class of LED, it does not mean the LED could be driven or would be driven with 3 Watts of power. Thermal management generally prevents driving an LED at its max current. In a manufacturers series of 3 Watt LEDs there is usually only one LED that can be driven with 3 Watts but still it is rarely driven at 3 Watts. Calculate actual power requirements. You can drive the 3 Watt LEDs just not at their full 3 Watt output. Many, if not most, are driven at 1 Watt or less. \$\endgroup\$ – Misunderstood May 12 '17 at 20:24
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It's possible to use a boost converter for generating 12V, and it's also possible to use several of them in series.
But it doesn't help in your case, because you can't generate 9W from a 5W power supply.

Consider also the efficiency of the booster. They promise "up to 94%", but I would rather assume about 80..85%*.

Next thing:
The booster in your link generates a constant output voltage. You can drive the LEDs with a constant voltage converter, but especially for High Power LEDs I would recommend a constant current converter, as the forward voltage is temperature dependent.

After all:
If you are sticked to the power supply, use a constant current buck driver and drive only one LED.
If you need the power of more LEDs, then use a stronger power supply (and nevertheless switch to a constant current driver).

*) In a series connection of several boosters, you would have to multiply all efficiencies, so the overall efficiency was much lower.

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It is not possible to do the task with your 5 Watts power supply, at least while LED's are on full power. DC boost converters will not help you in this case, because your problem is not with the voltage.

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  • \$\begingroup\$ PWM doesn't help in this case, as you would still have to supply the peak current during ON time. What you could do is time multiplexing (what requires a more complex control circuit), so that each LED works at specified peak current, but only for 1/3 of the period - of course the overall light output is the same as of just one LED at full power. \$\endgroup\$ – mic Feb 7 '17 at 11:49
  • \$\begingroup\$ @mic yeah, you are right. Editing \$\endgroup\$ – C K Feb 7 '17 at 11:51
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    \$\begingroup\$ Thanks guys. I can now tell people to stop bothering me to use the 5W power supply for this project. (And sorry, I had a complete brain freeze when I posted this. Thank you for being so tolerant in answering this.) \$\endgroup\$ – Noboru Akimoto Feb 8 '17 at 6:34

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