LED's don't have an "IN-RUSH" current. Motors do. Incandescent light bulbs do. Other forms of electronics do, but LED's don't.

And LED CC Drivers do, but not much in the overall scheme of things...

 

LED's don't have an "IN-RUSH" current. Motors do. Incandescent light bulbs do. Other forms of electronics do, but LED's don't.

Ya on a system level though the LED drivers would have an in-rush from the battery

 

Ya on a system level though the LED drivers would have an in-rush from the battery

Not really, if they're powered by DC, there should be no inrush, the inrush is to charge the capacitors in an AC to DC.

 

For LEDs rated at 3.3V @ 100 mA and using a 12V supply, the calculator is not rubbish, only misunderstood.

I don’t know what “the calculator“ you are referring to, but the TS referred to this one. Not only is it mislabeled “LED Inrush” omitting the word driver and giving LEDs a new property they never had before, but the very silly formula used simply multiplies the rated maximum current of the driver by 100.

So, the calculator under discussion is, in fact, rubbish.

 

I don’t know what “the calculator“ you are referring to, but the TS referred to this one. Not only is it mislabeled “LED Inrush” omitting the word driver and giving LEDs a new property they never had before, but the very silly formula used simply multiplies the rated maximum current of the driver by 100.

So, the calculator under discussion is, in fact, rubbish.

I used the https://calculator.academy/led-voltage-calculator/ and posted an accurate screen copy of the result.

The Inrush calculator, I presume uses the load capacitance of each diode so that when using thousands of them in an LED Matrix all turned on at once you might get a 100x surge from the ESR of the diode capacitance relative to the incremental Rs of the diode. It is not important or this calculator should NoT BE used for single LEDs or small arrays, which was not stated. It is valid to have many current sources , one for each string in a 2D matrix. So if I have interpreted the meaning correctly, it isn't rubbish. Only the assumptions are not clear.

 

Do you understand better or still disagree.?

For example, you would not be using the inrush calculator if you did not know when you get inrush into large capacitance loaded matrices.

Nor would you be using an inverter to power DC LEDs unless it was an AC to CC string driver with multiple strings like powering the outside of a building with LEDs.

"It also has implications for how a power supply converts AC mains electricity into lower DC voltages; and how much load an inverter can handle before it fails. "

 

It‘s really worse than you make it. The formula (shown at the bottom of the page) is:
\[ I_C = SSC\ \times\ 100\ \times\ D \]
Where SSC is Steady State Current and D is the number of drivers. In other words, it uses a blind coefficient of 100 for any driver. So, if I have an LED driver that can provide 10A, my calculated inrush is 1000A!

Ya on a system level though the LED drivers would have an in-rush from the battery

I found the explanation of the LED "inrush" almost amusing, if it had not been such a piece of garbage presented as correct. No explanation of how an LED heats up as it starts operating. BUT it is exactly the sort of thing I expect to see on the cartoon channel.
And I am not familiar with the "Load Capacitance" of an LED. I am not sure about it, I may have missed reading it on an LED spec sheet. It is an interesting concept. I am trying to imagine "a matrix with thousands of LEDs" but nothing appears. Can anybody else recall seeing the term elsewhere??
I mean relative to an actual LED of any size or power level.

 

. Can anybody else recall seeing the term elsewhere??

Yes. Look up the inrush current for Meanwell AC to CC LED drivers

https://www.meanwell.com/newsInfo.aspx?c=1&i=794 then use a soft start current limiter.
instead of half peak voltage with an inrush rating about 10x the CC output DC current, try it at peak voltage and verify your inverter does not clamp OFF from OCP.


https://www.meanwell.com/webapp/product/search.aspx?prod=ELGC-300

Never assume a well intended tool is wrong until you know all the assumptions.

We engineers tend to make bad conclusions if based on missing or wrong assumptions using good logic. Yet good Logitions want to verify all assumptions first. In this case the OP did not understand the assumptions, nor the rest of us.

 

I used the https://calculator.academy/led-voltage-calculator/ and posted an accurate screen copy of the result.

The Inrush calculator, I presume uses the load capacitance of each diode so that when using thousands of them in an LED Matrix all turned on at once you might get a 100x surge from the ESR of the diode capacitance relative to the incremental Rs of the diode. It is not important or this calculator should NoT BE used for single LEDs or small arrays, which was not stated. It is valid to have many current sources , one for each string in a 2D matrix. So if I have interpreted the meaning correctly, it isn't rubbish. Only the assumptions are not clear.

What? The variables it accepts are:

• The steady state capacity of the driver(s) in A (SSC)
• The number of drivers (D)

It then calculates “inrush current” using:

\[ I_C = SSC\ \times\ 100\ \times\ D \]

Nowhere is it concerned with ESR, number of diodes, or anything else. It just assumes you have N identical drivers of capacity X and does a brainless multiplication. It is rubbish.

 

Yes. Look up the inrush current for Meanwell AC to CC LED drivers

https://www.meanwell.com/newsInfo.aspx?c=1&i=794 then use a soft start current limiter.

OK, certainly a driver circuit, with a rectifier and filter. I mean for an actual LED.
AND I agree with the analysis in post #29.!!!

ALSO, I stand by my comment about the "Cartoon Channel."

 

Yes. Look up the inrush current for Meanwell AC to CC LED drivers

https://www.meanwell.com/newsInfo.aspx?c=1&i=794 then use a soft start current limiter.

Inrush current for power supplies is not “LED Inrush Current”, the inrush of an LED driver, as in any power supply, is caused by the filtering components (capacitive and inductive). It has nothing to do with the LEDs and what the supply is powering isn’t the issue.

From the page you linked:

When the AC power system powers on a capacitive or inductive load, such as switching power supply, there is a temporary inrush current peak, which may cause AC circuit breakers to trip even though the continuous current draw is well below the breaker ratings.

Just as the “LED Inrush Calculator“ makes no reference to LEDs, the Meanwell inrush current concerns are about the power supply not the load.

 

ok, i agree this " For example, an SMD package may have a much lower inrush current than an LDMOS device because SMD packages perform better at higher temperatures. " this example is irrelevant rubbish.

LDMOS are for RF amplifers with lower Ciss and Coss and SMD is a package used for FETs but not RF amplifiers and are not relevant to LEDs. What is relevant I thought was that capacitance in diodes and FETs are proportional to total power rating regardless of N devices, but not simply current.

Agree or disagree with my assertions?

 

I honestly didn't read all the "rubbish". But I did send a note to the site owners to remove it.

maybe it was generated by CHatGPT (LOL)

 

I found the explanation of the LED "inrush" almost amusing, if it had not been such a piece of garbage presented as correct. No explanation of how an LED heats up as it starts operating. BUT it is exactly the sort of thing I expect to see on the cartoon channel.
And I am not familiar with the "Load Capacitance" of an LED. I am not sure about it, I may have missed reading it on an LED spec sheet. It is an interesting concept. I am trying to imagine "a matrix with thousands of LEDs" but nothing appears. Can anybody else recall seeing the term elsewhere??
I mean relative to an actual LED of any size or power level.

Hi,

LED's, just like diodes, have an equivalent parallel capacitance. Basically anything and everything in nature that has a distance between two nodes has at least some capacitance due to the electrostatic space constant. That means it can be just two spheres or two wires or two of anything and it will have an equivalent internodal capacitance. Even space itself has this property.
With diodes the capacitance is very small, but does play a part in the recovery specifications. With LED's I would assume it to be the same, but we don't usually reverse bias an LED like we do with diodes when they are about to turn off.
The thing is, it is bound to be small, but as well all know, 'small' is relative to everything else which we assume is then 'large'. If we connect a lot of small capacitors in parallel we end up with one big value capacitor, and of course it depends on how many we connect in parallel.
The only way to find out is to look on the data sheet I guess, or look up how to measure this.

Now normally this would not affect a regular driver unless there were a lot of LED's I suspect, but something more esoteric would be a picosecond driver which has to take into account a lot more about the dynamics of the LED or laser diode. In that case there would be a lot more concern about turning it on fast and therefore how much current it would take at the instant of turn-on.

What I cannot believe is that there is a hard and fast rule that applies to every circuit with LED's that allows us to calculate the initial current surge. That's got to be impossible I would think.

 

Well I've been doing some digging and had a brief chat to an acquaintance who builds large scale LED-based advertising hoardings and displays, stadium lighting, etc. and he said there's no such thing as LED In-rush current. The capacitance is so small its not even sampled as a parameter. If anything LEDs draw more current hot than cold, the forward voltage drops about 1.9mV per °C, or about 0.2v at 100C for a typical 6v 10W COB module. ca For stadium lighting there is considerable in-rush current to the AC/DC drivers, they typically use 48v 20A drivers (8 x 6v 10W modules x 12 strings = 960W) but they have power factor correction and a soft start facility so its not as bad as it could be - a 1000W driver on 240v AC is 5A operating and about 15% more on start-up. He also said that if your LED driver has a startup current '100s' of times its run current, throw it away and get a decent one!

Elsewhere, another specialist lighting company contrast banks of 'dimmable' 230v LEDs with 24v LEDs and note that their scalable dimming technology is better suited to the latter in part due to the 'inrush current' of the 230v device.

 

Oh the issue with drivers and not necessarily LED's, even wall warts have an inrush current. You can even hear the spark sometimes when you plug one in. I suspect it is the internal filter capacitor used on modern wall warts. The older style with a 60Hz transformer probably has much less inrush current.