Bright then dead - DC current regulator question

[toren]

Maybe one of you pros can answer this. Do any of the LED circuits available output a constant current for the life of the batteries you're using? With 2-3xAAA and a MicroPuck I get over an hour of really bright light, then many hours of slowly dimming light. I don't mind some dimming, it's nice to have a low battery warning before it dies, but is there a circuit out there that keeps this down around an hour or less? Is this only possible with a step-down convertor?

Thanks for any recommendations

 

[Doug Owen]

Sure they do. A (true) *regulator* does just that, regulates or controls it's output to keep it constant. The micropuck, however, is a *converter* (that is it runs 'open loop', out of regulation, so the output tracks the input).

Regulators can be either step up or step down. As can simple converters. Proper regulators are fairly rare as they in general cost more and most customers don't understand the difference well enough to be willing to pay for it.

Doug Owen

 

[Roy]

Here is the runtime plot for the VIP on medium power.

Is this the kind of plot that you wanted?

 

[rdshores]

What IC is used in the above circuit and what is the current draw through the Luxeon at "medium" power? It looks sort of like a BadBoy.
Thanks.

 

[xenopus]

[ QUOTE ]
Doug Owen said:
Sure they do. A (true) *regulator* does just that, regulates or controls it's output to keep it constant. ...

Proper regulators are fairly rare as they in general cost more and most customers don't understand the difference well enough to be willing to pay for it.

Doug Owen

[/ QUOTE ]

Yup -- ours maintain better than 0.2% current regulation then flash to alert the user that the batteries need replacement or recharging, but most consumers don't really need such regulation unless they are looking for repeatability in experiments etc.

Piers!

 

[toren]

Thanks Everyone, very helpful.

Roy, that plot is excellent! Where would one find the "VIP"?

If anyone else can recommend some true regulators please chime in.

 

[Roy]

Brouse through this collection of runtime plots and you should find several with that flat profile.

The VIP is one of MrBulk's limited run creations that is not currently produced. Check in the two B/S/T forums and you might find one for sale.