Chip Efficiency Question

SignQuest

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I'm hoping someone here and answer this, what could be a basic question and to make sure I'm not going insane.

Over the last couple of years I've had a LED MFG in China custom make LED modules for us for the Sign Industry for backlighting. They are 2LED, 3LD, & 4LED modules. We started out using more efficient 11 V chips for a 12V LED System. They were deemed to be 150 lm/w or so.

(Typical LED Module)
High-Lumen-DC12V-1-2W-SMD-Samsung-LED-Module-beam-angle-160-degree-.jpg


This is where I may need to be corrected, and I need to make sure I'm not going insane.

We wanted to go with using newer higher efficiency 11V Chips to 160 lm/w into the modules...for more light for the same input power.

If the wattage of the modules is the same, say a small 3LED module .72 watts each. In using the 160lm/w module, it should have a higher light output than the previous 150 lm/w module right?.

I'm having other issues with this company I'm using, and I'm thinking they're having financial problems. In our last order without asking authorization they made the module wiring to 20 AWG, from the previous 18 AWG, Only when I discovered it. It was "Ooops, sorry we now have a new standard". They refunded some money. Also, the company didn't renew their UL Listing last Nov and I had to get on their case that the listing needs to be current, which they did but it took them a few months. I'm thinking they were starting to

Now I have this issue.

I know it's always a risk specifying out to overseas, and it's hard to hand hold form here in the states.

So, with this latest batch that they just sent me which is said to be a 11V 160 lm/w chips. I put the newer modules in a test cabinet with a translucent white face to see where the lighting on the acrylic face is compared to the previous batch (Averaging LUX High's and Low's), and had a drop in luminance. About 10% drop from the previous.

When I asked about this here is the reply I received.

Thank for your follow up.

Actually if higher Lumens, the efficiency will be lower.
If higher efficiency, the lumens will be lower.

And the Lumens test results related with the LED Power supply incoming. If higher LED Power, the Lumens will be also higher.

Hope it can helps you.

Is this true when upgrading the same voltage chip, and rating from a150 lm/w?
 

Dave_H

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Looks to me that the 3-LED module in image, powered from 12v (I am guessing 11v is minimum accounting for power supply tolerance and line drop), is about the best you can do for "module" efficiency; assuming 3-series and resistor limiting (can see them). You could get high efficiency on 12v 2-LED or 4-LED modules but only with voltage conversion design, which is probably not the case for most of these modules due to cost and complexity.

12v/1.2W means 100mA current, however only about 9v (and 0.9W) will be delivered to the LEDs, so about 75% efficient in that sense. You would need to derate LED efficacy by that, to get the true lumens/watt. If the LEDs are 160 lumens/watt, this would work out closer to 120 lumens/watt at the module level (dc power in -> light out).

To actually get 160 lumens/watt (module) the LEDs need to be over 200 lumens/watt; certainly possible with some recent Samsung LM301B LEDs or similar.

Dave
 

WarriorOfLight

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@SignQuest
You should keep one general Thing in mind, a higer Power of the LED Module will result in a higher heating of the Module. The Power dissipation will not ne that good in my opinion because of the plastic housing.

You should not go too high with the at all Power consumption of a module. Most of the Power will result in a higher temperature of the Module.

Using a more efficiant LED should be fine, increasing the Overall Power consumpion may be at some point of the Power consumption a problem.
 

SignQuest

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Looks to me that the 3-LED module in image, powered from 12v (I am guessing 11v is minimum accounting for power supply tolerance and line drop), is about the best you can do for "module" efficiency; assuming 3-series and resistor limiting (can see them). You could get high efficiency on 12v 2-LED or 4-LED modules but only with voltage conversion design, which is probably not the case for most of these modules due to cost and complexity.

12v/1.2W means 100mA current, however only about 9v (and 0.9W) will be delivered to the LEDs, so about 75% efficient in that sense. You would need to derate LED efficacy by that, to get the true lumens/watt. If the LEDs are 160 lumens/watt, this would work out closer to 120 lumens/watt at the module level (dc power in -> light out).

To actually get 160 lumens/watt (module) the LEDs need to be over 200 lumens/watt; certainly possible with some recent Samsung LM301B LEDs or similar.

Dave
@SignQuest
You should keep one general Thing in mind, a higer Power of the LED Module will result in a higher heating of the Module. The Power dissipation will not ne that good in my opinion because of the plastic housing.

You should not go too high with the at all Power consumption of a module. Most of the Power will result in a higher temperature of the Module.

Using a more efficiant LED should be fine, increasing the Overall Power consumpion may be at some point of the Power consumption a problem.
My notifications for replies for this forum sent to not be working.


Thank you for the replies.

That module I posted was just one I took off the net, I don't want to publicly post our module.

I have two companies overseas configuring our modules. One is excellent, making our newer modules more efficient, the other is the one I'm questioning what hey might be using, maybe they downgraded somehow.

@Dave_H , so if I understand you right. In one of our modules, the one in question. If it's a 12V .72w module, and each chip or diode is 11V we're getting about 90% efficiency?

And also, it seems like if we got 160 lm/w for our modules from one company from our previous rated 150 lm/w, they did it right. Would that mean if I'm correct about the 90% efficiency above that they chose a chip or diode that was rated for 180 lm/w? 180x90%

If this is the case, the second company had to have used a lower grade 11v diode/chip?
 

Dave_H

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The meaning of efficiency (and LED efficacy) is getting a bit fuzzy.

Bare LEDs themselves have efficacy which is lumens/watt.

Module will have overall efficiency lumens/watt based on LEDs (efficacy lumens/watt) combined with percent power actually delivered to the LEDs (which can vary by design and power conditions). I am not sure how the industry specifies this.

There are no 11v white LEDs, their forward voltage (vf) is around 3v each but varies with batch, temperature, and current. Three in series gives around 9v. As mentioned above I think 11v is the minimum operating voltage for nominal 12v system, you would need to confirm with vendor(s). Other than that, comparison of 12v to 11v is moot.

Is the vendor specifying 150 or 160 lumens/watt for the overall module, or just the LEDs they use? (suspect latter)

Whether the module is nominally 12v/0.72W (60mA) or 12v/1.2W (100mA) its overall efficiency (power delivered to the LEDs) will be about the same, if they are wired the same (e.g. 3 series).

Increasing LEDs from 150 to 160 lumens per watt, assuming nothing else changes, is less than 10% improvement. I'd be surprised anyone would perceive this.

Two small resistors are visible through the plastic case, but can't read the markings.

Only other thing I can suggest is compare brightness for modules under the same input voltage conditions.

Dave
 
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