Illuminator SMD - overdriving 1W Luxeon?

[mike101]

I just assembled Lambda's Illuminator SMD with a 1W HD Luxeon today. Before I applied epoxy to the pill I connected a DMM, the new and old pills and some batteries in series to see how much current they would draw from the battery. Below were the results;

Illuminator SMD + 1W HD Luxeon:
1 Panasonic CR123, 2.95V - few used (no load) -------------- 1.5A (app.)
2 GP Ultra Alkaline, 2.85V - some used (no load) ------------- 1.43A (app)
2 Eveready Super Heavy Duty, 2.75V - drained (no load) ----- 0.5A (app.)

ILL Pill + 1W LD Luxeon:
(Same batteries as above)
1 Panasonic CR123, 2.95V (no load) --------------- 1.18A (app.)
2 GP Ultra Alkaline, 2.85V (no load) ---------------- 1.10A (app)
2 Eveready Super Heavy Duty, 2.75V (no load) ----- 0.42A (app.)

The Illuminator SMD was burning hot in the first and second sets of battery while the ILL Pill was just slightly warm. The ILL Pill could be same hot if using fresh batteries. All readings were only approximate due to the bad contact of the DMM probe and dropped rapidly as the power consumed.

My questions are:
- Is the performance of my assemble typical to other ILL SMD/ILL Pill?
- Is the circuit current regulated or voltage regulated?
- If the ILL SMD draws 1.5A (Iin) from 2 AA fresh batteries, how much current (Iout) is it feeding the LED?
- Is the 1W LED overdriven?
- If it is overdriven, can I do some minimum mod to limit the current?
- If the inductor is not saturated (I can't figure whether the heat comes from the LED only or also from the inductor), can the pill drive a 3W Luxeon (3V x 1.5A x 75% eff.)?

I know these pills are of very simple circuit due to the low cost, but I still don't want the Luxeon burnt. And if the efficiency is acceptable, it would be a low cost 3W driver. Any advice?

 

[mike101]

I just got this email reply from Lambda, thanks.

[ QUOTE ]
The inductor is heavily saturated in the SMD circuit, and makes the output
switching transistor in the IC generate some heat. This can be controlled by
using a low value sense resistor between pin 6 and pin 7; the comparator
will limit current when the difference between pin 6 and pin 7 reaches
300mv. Example, a 0.3 ohm resistor would current limit at 1.0A, and a 0.6
ohm resistor would current limit at 500mA. The inductor needs to be larger
value, which is too physically large for 2AA pill use, to prevent saturation
due to the circuit frequency of operation.

The IC can be set to both to current and/or voltage regulate. See the
MC34063A data sheet for details.

Running wide open as in the SMD circuit, it's just a boost circuit with some
inherent regulation.

3W Luxeon is fine for use on the SMD.

Average current out is ~500mA from the circuit.

Kevin


[/ QUOTE ]