# High power LED power/driver question.

#### KarelSoel

Aug 18, 2021
1
I have 8 high power "3Watt" LEDs setup in series. They Are 3.2-3.8V, 700mA. If I did the math correctly. I have to get a power supply that is 30.4V @ 700mA. Is this correct? Also, I'm Confused as to weather or not I need a driver. I've google searched it, but I'm still slightly confused as to the purpose of a driver. Anyone know where I can get a power supply with this rating?

Any help is appreciated.

Thanks

#### Harald Kapp

##### Moderator
Moderator
Nov 17, 2011
12,713
I have to get a power supply that is 30.4V @ 700mA.
At least.
I'm Confused as to weather or not I need a driver
I'm still slightly confused as to the purpose of a driver.
You'll need some form of current limiting. Otherwise the LED current is not controlled and can lead to thermal runaway, burning your LEDs.
Either a series resistor or a constant current LED driver. Both will require a higher input voltage than computed above.
Example: Using a 2.2 Ω / 2 W resistor the voltage drop will be dV = 2.2 Ω ×0.7 A = 1.54 V, therefore the output of the power supply needs to be 30.4 V + 1.54 V = 32 V.

#### Bluejets

Oct 5, 2014
5,985
I have 8 high power "3Watt" LEDs setup in series.

Any particular reason why they must be in series?
There are other arrangements which would lower the voltage requirements.

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