led driver question

[doctaq]

this is the driver in question
http://www.dealextreme.com/details.dx/sku.13690

someone on thier board suggested that it might be possible to increase the current by replacing a resistor, does this seem feasable?

the driver runs at 320ish ma and output voltage is 16-26v, is there some resistor i could look for here that correlates to those values? what value and power should i use to replace it if i am trying to get the current up to 700ish ma?

 

[purduephotog]

Re: led driver question DX SKU 13690

this is the driver in question
http://www.dealextreme.com/details.dx/sku.13690

someone on thier board suggested that it might be possible to increase the current by replacing a resistor, does this seem feasable?

the driver runs at 320ish ma and output voltage is 16-26v, is there some resistor i could look for here that correlates to those values? what value and power should i use to replace it if i am trying to get the current up to 700ish ma?

Trying to understand the new boards.

They have a viper22a chip on them, which can be seen here:
http://pdf1.alldatasheet.net/datasheet-pdf/view/25604/STMICROELECTRONICS/VIPER22A.html

In it there is a statement of FB (feedback) linked to source, from 0-1V, provides maximum current. On the bottom of the board there is indeed a link to the FB pin from a SRC pin, but there is a capacitor in between- and I don't have a capacitance meter.

I suppose I'll have to make a jig to secure the board, and possibly fire it up to make some measurements.

The viper22a chip tho does say something to the effect of a 320ma current limit- which might mean no go at increasing any current. That leaves running them in parallel which I find rather scary.

 

[purduephotog]

Well, I decided to go for broke.

Yes, it is, at least with the new ones which contain a viper22a chip.

On the bottom of the viper22a chip there is a FB pin- It is linked to a source via a chip, Cx. Soldering across this chip will double the current.

HOWEVER:

The unit will overheat and shut down in about 30 seconds, and the current will go from 750ma to 710ma, then terminate. When it cools down, it'll come back on at 730ma, and repeat. I haven't solved the heat sink issues yet... perhaps soldering a copper slug across the drain area (which seems to be the hottest part) will solve it.