# Variable current circuit for High Power LED

#### Samk

Nov 27, 2017
3
Specs of LED(BXRA-56C5300H 50W) are 23.5 Vf and 2.1 A typical current.
Led max rated current is 4 A @ 28.5 V only for pusling at 10% duty cycle.

My actual project has 64 such LEDs and will be powered with 24 V 67 A DC supply to 32 such LEDS so equivalent 2.09 A current for each LED string connected in parallel to supply.

I want the LED should be operating at this rated current of 2.1 A for 99% of time and must be able to switch (digitally controllable) must draw 4A with 10% duty cycle and switch back to regular 2.1 A current.

I do have heatsinks for these LEDs as they will be dissipating lot of heat. Can anyone suggest me circuit for this and explain .

Thank you!

#### BobK

Jan 5, 2010
7,682

Calculate the wattage of each and see if you see a problem there.

Bob

#### Samk

Nov 27, 2017
3

Calculate the wattage of each and see if you see a problem there.

Bob
Bob,
I am using two such supplies . One supply is powering 32 LEDs.

Can you suggest how can I make led drive 4 A on demand using three batteries of 12 V 150 Ah rating

#### BobK

Jan 5, 2010
7,682
You cannot just hook up 32 of these LEDs in parallel and have them share the current equally. You need current control for each of them, or each string of them in series, which would be preferred in this case. 24V is not enough headroom to allow you to control the current at ~23.5V.

And now you have added 3 12V batteries, where did that come from?

I see no problem with supplying 4A at 28.5V 10% duty cycle from 3 12V 150AH batteries. All you need is a PWM controller on top of the 64 current control circuits.

I am curious as to why you want to do this.

I am also curious as to how you are going to get rid of 3000W of heat. That is enough to heat several rooms of my house in a New England winter.

Bob

#### Samk

Nov 27, 2017
3
You cannot just hook up 32 of these LEDs in parallel and have them share the current equally. You need current control for each of them, or each string of them in series, which would be preferred in this case. 24V is not enough headroom to allow you to control the current at ~23.5V.

And now you have added 3 12V batteries, where did that come from?

I see no problem with supplying 4A at 28.5V 10% duty cycle from 3 12V 150AH batteries. All you need is a PWM controller on top of the 64 current control circuits.

I am curious as to why you want to do this.

I am also curious as to how you are going to get rid of 3000W of heat. That is enough to heat several rooms of my house in a New England winter.

Bob

Bob,
I understand current can't be equally shared so current control is needed for each LED.

Since the power supply which I am using has capacity of providing only 24 V and 67 A I was thinking to use SLA just for purpose of providing more wattage when I am required to pulse LED to max rating of 4 A.

I am open to your suggestion. As I mentioned I will be running led at rated current of 2.1 A most of the time and would have to run at 4A current when required which can be controlled via digital control signal.

I am thinking how can I achieve this.

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