Constant Current and Heat Generation

InspectHerGadget

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Apr 17, 2014
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247
Every time I read about CC on the forums or in a review, it is always portrayed as a positive.

I can see the point that you get constant light although, it doesn't seem worthwhile if it shortens run times OR generates significantly more heat.

Heat is a big problem in most lights as they drive them to the maximum. You can certainly turn them down or off to cool but if you want to use it on maximum then heat is an issue.

I wonder how much extra heat it generates? Every Watt that doesn't go into producing light will be wasted as heat. The exact amount is hard to calculate from graphs, but looking at graphs of lights like the Niwalker Vostro BK-FA02, it seems that it runs much longer, other things being equal compared to CC lights.

I suspect that CC circuits produce a lot of extra heat but I'd like someone to comment.
 

vicv

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Mar 22, 2013
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Not all constant current regulators burn off the extra voltage as heat. Just linear driver. Mostly single li ion cell lights. Almost all 2 cell use a buck regulator and dont add heat.
 

reppans

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Mar 25, 2007
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If you're comparing current regulation to PWM at maximum output, my understanding is that they are equivalent at maximum output. PWM is only used for the lower modes to dim the light.
 

InspectHerGadget

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Apr 17, 2014
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I'm listening. My question was really motivated by looking at the graphs that Selfbuilt did on the review of the Niwalker Vostro BK-FA02 with the MT-G2 emitter. I looked at the graph and compared to other lights it seemed to be last longer at maximum output than lights that tried to maintain output. Have a look and see what you think.

The Vostro uses PWM at lower modes to dim the light as reppans said.

The Vostro has some impressive run times. It may be that some of this efficiency comes from the huge heat sink it has that maybe allows it to run at a lower temperature than other lights which have smaller heat sinks and run hotter. Heat is a killer of efficiency of LED lights so it must be a major factor in efficiency.
 

InspectHerGadget

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Apr 17, 2014
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An mtg2 requires 2 cells as well so they're buck drivers. And it's a very efficient led

Yes but some of the other lights compared use the same emitter. The Vostro still looks mighty good so still trying to figure out why.

I looked again and there are quite a few things to factor in so maybe have to be careful in drawing any conclusions.

You are right about the MT-G2, it is a real killer emitter in so many ways, the tint, the power and the efficiency and it can still throw well enough to please most people with the bigger reflectors.

I have the ET MX25L3 so I was specifically comparing the ET SX25L3 with the FA02, taking into account the difference in batteries it still looks like the FA02 has an advantage. This is the graph in Selfbuilts review of the SX25L3 I am basing my comments on. The difference isn't huge admittedly.
 
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InspectHerGadget

Enlightened
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Apr 17, 2014
Messages
247
I think I've confused everyone by not using the correct terminology.

What I was referring too was fully regulated output as opposed to direct drive. The FA02 uses direct drive on the highest mode so the output decreases as the battery voltage drops whereas torches like my MX25L3 and the SX are fully regulated so that the output is constant aside from the step down.

My apologies.
 
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