suggestions for LED driver

[selvam12345]

I am building a battery powered LED lamp with 4X1.2V rechargeable batteries, and 3X3W LEDs I am trying hard to find a driver which could do the job of connecting them together

the LEDs I have are,

LED, HIGH POWER, 5000K, 70CRI, 275LM
Series: LUXEON TX
LED Colour: White
Luminous Flux @ Test: 369lm
Forward Current @ Test: 1A
Forward Current If Max: 1.2A
Forward Voltage @ Test: 2.86V.

could anyone please help me what should be the specifications of the driver??

 

[BradtheRad]

Your battery pack will range between 4 and 6 V. The ideal way to maintain constant brightness is by using a boost converter (with current regulation).

It is good if you arrange the led's in series, and supply them with 8.8 V at 1A. A boost converter would step up the battery pack voltage.

Did you rule out the idea of using 3 batteries? That is the amount that will power an led adequately. The supply will be about 3.6 V. It would be feasible to install a simple 1A current regulator on each led (if you do not mind wasting power through resistive drop).

 

[Audioguru]

I don't know how you are going to cool or mount these tiny powerful LEDs. Their maximum continuous current is 1A but all the specs are with a current of 700mA then it heats to 85 degrees C.

The forward voltage is not 2.86V. It might be 2.86V. At 700mA/85 degrees C it is anywhere from 2.5V to 3.0V. Its forward voltage is 0.1V higher when its chip is cool at room temperature.

 

[selvam12345]

Your battery pack will range between 4 and 6 V. The ideal way to maintain constant brightness is by using a boost converter (with current regulation).

It is good if you arrange the led's in series, and supply them with 8.8 V at 1A. A boost converter would step up the battery pack voltage.

Did you rule out the idea of using 3 batteries? That is the amount that will power an led adequately. The supply will be about 3.6 V. It would be feasible to install a simple 1A current regulator on each led (if you do not mind wasting power through resistive drop).

I have found a couple of drivers, which seem to fit my design of 4X1.2V batteries

the problem here is all these drivers are meant for applications(flahlights) here only one LED is used
now, should i use the one which provides a constant current of 1A (**broken link removed** connect the LEDs in series

or

should I go for a driver which provides 3A and connect the LEDs in parellel (https://dx.com/p/t6-2500-3000ma-3-m...or-diy-flashlight-4-5-18v-128269#.UyBWW_mSxWY)

 

[selvam12345]

Thanks for the reply, I have mounted them on 8cm (diameter) X 4cm height cylindrical an aluminium heat sink so i think it should take care of the heat dessipation.

further, the specifications given in the manufacturer's site says the rating to be 1000(test)-1200mA(max) could it still be 700mA i do not understand why are you saying it could be 700mA.

P.S I am a electronics novice biologist forgive my ignorance.

 

[Audioguru]

the specifications given in the manufacturer's site says the rating to be 1000(test)-1200mA(max) could it still be 700mA i do not understand why are you saying it could be 700mA.

Many of the spec's on the datasheet for the LED are done only at a current of 700mA.
The datasheet lists an Applications Brief AB106 that details how and has calculations for cooling the device. I did not read it.

- - - Updated - - -

I have found a couple of drivers, which seem to fit my design of 4X1.2V batteries

the problem here is all these drivers are meant for applications(flahlights) here only one LED is used
now, should i use the one which provides a constant current of 1A (**broken link removed** connect the LEDs in series

This cheap thing has no spec's. It does not say it boosts the voltage, 3-6-9V might be its input voltage but it does not say its output voltage. When the voltage from your four battery cells drop to only 4V then it might barely light only ONE LED, not more.
I think it is made to blink an LED on and off in Morse Code (SOS).

or should I go for a driver which provides 3A and connect the LEDs in parellel (https://dx.com/p/t6-2500-3000ma-3-m...or-diy-flashlight-4-5-18v-128269#.UyBWW_mSxWY)

You CANNOT connect LEDs directly in parallel because one might have a forward voltage of only 2.5V and another might be 3.0V. The 2.5V one will take ALL THE CURRENT and quickly burn out then the other one will also burn out a little later. Cheap Chinese flashlights use LEDs that are measured then grouped to all be exactly the same.

 

[BradtheRad]

This simulation shows methods of powering 3 led's. The led's are similar but they could possible have slightly different volt/amp response.

On the left the 3 led's are in parallel, a single resistor represents a single driver. It can work if you make sure each led carries equal current. This might be done by installing extra resistors inline.

In the middle, three drivers are used to power 3 led's in parallel. Each driver needs to be tailored to the led's volt/current response.

On the right, a boost converter drives 3 led's in series. It can be regulated to whatever current you desire. (This may or may not be one of the drivers you linked to.)



The led drivers which you linked to have specs which are indefinite, and you cannot be certain they'll do what you want. If you wish to try them out, that is fine, and you might want to get a few of both, to experiment.

 

[kam1787]

what's your main objective; brightest light, or longest battery life? constraints? size? weight?