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Any help would be appreciated as I am new to LED drivers. I have a very basic understanding of electronics and I'm not up to designing my own driver yet.

I have tried to power this LED with a Meanwell LDD-1200 from 5 or 6 lithium batteries but the voltage varies as the batteries discharge and the LDD uses 3V dropping the output voltage.

If someone doesn't mind sould you please design a circuit for me?

If a driver already exists that isn't too expensive or too large (i intend to use this LED for mounting biking, i have only one functioning cochlear and i rely on vision for balance at night)

The short of it: I am wanting to drive a Cree CXA1512 LED @ 1200ma with a dimming control.

The Long of it: I would like a Switch Mode (I hear that switch mode produces the least heat) Constant Current (1200ma) driver with dimming if possible (not necessary but preferable).

The CXA1512 runs at 18V and max current is 1200ma.

Intended battery pack would either be 5 or 6 lithium cells (3.7V 3200ma) in series OR parallel depending on whether a buck or a boost system would be best/easiest.

For dimming I'd like a potentiometer. I'd like to stay away from micro controllers.

Would it also be possible for the design to be scalable? I.E. change a few component values to run a string of 4 cree XML leds, which differ in current and voltage. Or make the circuit adjustable so one could adjust the CC value and then the voltage to suit.

I was originally trying to fit the circuit into an existing bike LED light shell but I realise that the circuit may need to fit on the battery pack instead, however the smaller the form factor the better.

Thankyou for you time in advance.

Roy

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First impression:

The below figure from datasheet says that, it has a forward voltage drop of about 20 V at room temperature, and will be more at lesser temperature.

LM43602 or TPS54231 can switch the output to about 21 V from a input of 23 to 25 V. I would use 8 battery cells (total voltage of ~29 V to ~23 V)

enter image description here

STCS1 or similar rated constant current LED driver (1.5 A max) if the power section is only for driving LED section.

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  • \$\begingroup\$ I seems that you are suggesting that I use a setup that has a voltage drop across the driver to set output voltage. Forgive me if I'm wrong. I'm after a design that isn't dependant on input voltage. \$\endgroup\$ – Xenocatalyst Jul 9 '15 at 5:59
  • \$\begingroup\$ Forgive me if i was not clear. the suggested STCS1 IC (for example), can operate with wide varying input voltages (16 to 40 V), and can provide constant current (1.2 amps ) independent of varying input voltage. Another point was to increase the voltage to more than 24 V to accommodate huge forward drop(~20 V) of the LED. \$\endgroup\$ – Umar Jul 9 '15 at 6:57
  • \$\begingroup\$ Thanks, for the STCS1 I gather from reading the data sheet that i can regulate the current by changing the resistor Rfb to approx 0.083 ohms. \$\endgroup\$ – Xenocatalyst Jul 13 '15 at 10:57
  • \$\begingroup\$ So it can be powered up by applying Vcc to pin EN, OR a pwm signal to pin PWM. What i dont know is how is the voltage regulated (or does this adjust automatically) and how to apply PWM. Any Chance you'd be able to help me out with a circuit diagram? \$\endgroup\$ – Xenocatalyst Jul 14 '15 at 0:08
  • \$\begingroup\$ The STCS1 is not a good candidate for driving LED current of 1.2 A. We have to keep the input voltage difference between the LED drop (~19 V) and input supply 6 cells = 22.2V) very close. The power dissipation math says that the temperature of the IC rises and can be up to 150 deg C. I should put a big heat sink (it works) or have to find other better one. I will come back. RFB vale was right. PWM can be used to create dimming effect. EN pin needs to be high for the circuit to function. It can be used to turn off and turn on the LEDs. \$\endgroup\$ – Umar Jul 14 '15 at 3:48

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