Selecting the wrong power supply for your COB or LED Board setup can fry your lights on power up or increase the risk of hazardous behaviors. Verify the Voltage and current values of your power supply and setup before wiring and double check all your electrical connections before power up.


Only use Constant Current led drivers

photo :  supplyledlight  on  flicker

Leds are electronic parts that are designed to be powered using constant current power supplies. These drivers are specified by their :

  • Current output or Rated current : The current they will push into the circuit, this value will be imposed to the circuit by the power supply.

  • Voltage Output or Constant current region : The Range of voltage at which the power supply can operate. This value is fixed by the circuit and the power supply will adapt to it

  • Power : In Watts, is just Current Max * Voltage Max.

  • Dimming Options : Some power supply (eg meanwell B and AB types) can be dimmed by using a resistor, 10V analog or PWM.

Meanwell are leaders on the constant current led drivers market, we only use this brand and have not tested other suppliers.

We usually order our power supplies on Digikey, they stock lots of references, prices are fair and their shipping is quick.

Know What you are trying to light up

Voltage and Current needs of a setup cannot be guessed and must always calculated from specifications. Ask and the guy who sold/gave you the parts or google any inscription on it and find its description/datasheet. The information you are looking for is :

  • Forward Voltage (Vf) : The voltage that needs to be applied to the part to light it

  • Absolute maximum current (Imax) : Go over and you fry your part

  • (not necessarily) Nominal current : Current at which the part is tested and usually its maximum efficiency.

photo :  Wikipedia

photo : Wikipedia

Design your circuit

If you have multiple times the same part you can use one power supply to light everything. For beginners we recommend to stick to simple serial and parallel circuits.

  • Series : When in series the voltage of the leds adds up but the current needs stay the same. Powering 2 leds in series is like powering one led with a forward voltage of 2*Vf and a current max of Imax. 3 leds in series is like 3*Vf and still Imax … N leds : N*Vf and Imax.

  • Parallel : When in parallel the current of the leds adds up but the voltage need stays the same. Powering 2 leds in parallel is like powering one led with a current max of 2*Imax and a forward voltage of Vf, 3 leds in parallel is like 3*if and still Vf …N leds : N*Imax and Vf

  • Both : Do not try if you do not fully understand what you are doing. First calculate the equivalent led of the parts in series (strips), then calculate the global equivalent led of those strips in parallel. Example is equivalent to powering one big panel with a forward voltage of 2*Vf and a max current of 2*If.

Choose your PSU & Start Growing

With the calculated forward voltage of your circuit you can pick your power supply :

  • Voltage range : Must include the Forward Voltage of your circuit. Leds and Cobs forward voltage changes a little during use, insure that you have a margin of a few volts to 10%.

  • Current output : Can be anything below the max current of your setup. The more current you will supply the led, the brighter it will shine. Usually people tend to max out the light from their part.

  • Power : a consequence of your voltage and current choice. A good indication on how much your system will burn in energy and need to dissipate in heat. Led Boards larger than a standard paper sheet can usually handle up to 75W without heatsink. Cobs always need heatsink if you don’t have one, get a CPU heatsink, glue the COB with thermal glue and power the fan with 12V.

Example : to power some CXA3050, which have a forward voltage of 37V and a max current of 2.5A.

  • HLG-120H-48B for one cob : voltage range : 24 to 48V so 37V is ok and current (2.5A) will be at max.

  • HLG-240H-C2100A for two cobs in series (like one cob with Vf = 2*37V=74V and Imax still 2.5A) : Voltage range : 59 to 119V so 74V is ok and current (2.1A) will not be at max (but still works ;)).

  • HLG-240H-48 for two cobs in parallel (like one cob with Imax = 2*2.5A=5A and Vf still 37V) : 24 to 48V so 37V is ok and current (5A) will be at max.

photo :  u/HardLiquor_  on  reddit

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