More Power Out Than In???

LED_ASAP

LED_ASAP

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It could be that your converter has multiple operating modes, and you are not getting the right numbers in the way you measured the voltage and current.

One thing happened to me was that when I was playing with the TI chips, the soft start feature clamped the power at something like 40%, until I disconnected the LS to measure the current, then it went up to full power---and I was shocked to find the efficiency to be over the roof :)

Just put in two small resistor, like 0.1ohm, one in series with the LED, one in series with the battery, and re-measure the numbers.
 
thefish

thefish

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LED_ASAP said:
It could be that your converter has multiple operating modes, and you are not getting the right numbers in the way you measured the voltage and current.

One thing happened to me was that when I was playing with the TI chips, the soft start feature clamped the power at something like 40%, until I disconnected the LS to measure the current, then it went up to full power---and I was shocked to find the efficiency to be over the roof :)

Just put in two small resistor, like 0.1ohm, one in series with the LED, one in series with the battery, and re-measure the numbers.

Ok I put a 0.33 Ohm resistor in series with the LED and I get a 3.3mV drop so that would imply a 1mA current, but there is no way or it would not be powering the LED I think.
 
EngrPaul

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thefish said:
Ok I put a 0.33 Ohm resistor in series with the LED and I get a 3.3mV drop so that would imply a 1mA current, but there is no way or it would not be powering the LED I think.

try 10 mA :)
 
thefish

thefish

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EngrPaul said:
try 10 mA :)

Oops thats right 10mA... then I can come to 1 of 2 conclusions...

A) My driver is not working right (should be CC 350mA)
B) This driver is not working right and the LED is really efficient (seams bright for 20mA)
 
macforsale

macforsale

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Last edited:
A

AdamW

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You have Duracell's new battery.

It's the 1.21 gigawatt flux capacitor in AA size.










Come on, you had to know that people would joke about the perpetual motion/ free energy nature of your post!
 
thefish

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macforsale said:
Use your scope across the .33 ohm resistor to get an idea of waveform. Just make sure to keep your grounds isolated between the unit under test and the scope. Putting ground clip on one side is OK if that circuit is isolated from the ground of the scope. Keep the leads short to keep the ringing down and to be able to set a trigger point that gives you a stable picture without the "ghosting" in your 1st post.

I have tried that and it seams like as soon as I clear up the ring a secondary wave shows up on the same trace... it is very strange, I am all out of ideas how to get a good image of the wave form... the gorunds are not linked as the circuit is running off of an AA battery and the scope is connected to the mains.
 
macforsale

macforsale

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Last edited:

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