Author Topic: LED Inrush current causing Overload status  (Read 4024 times)

Offline FluidPowerTom

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LED Inrush current causing Overload status
« on: September 17, 2016, 01:46:12 AM »
I've had this issue on a few applications wherein a supposedly 1A or less LED causes an overload error due to inrush current.  I've investigated this issue and verified that I can get a 12VDC 1A LED to pull as much as 5A very briefly.  I've got this issue on systems using a MC050-110 with 3A outputs as well as a MC038-010 using 10A outputs (trying to control 4 of these LEDs).  There doesn't seem to be a programming solution to this.

Has anyone got a good solution on this?  I'm thinking I'll try one of those simple inrush current limiters that you can buy for a few bucks or less.

I've optimistically tried ramping the duty cycle, but of course that basically means starting at a lower voltage which pulls more current.
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Hydra-Power Systems - Distributor - Pacific Northwest

Offline jashom1

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Re: LED Inrush current causing Overload status
« Reply #1 on: September 19, 2016, 05:53:53 AM »
Hi,

I have had this issue as well where an MC050-010 would drive a LED beacon, but an MC024 would not drive the same one, both with 3A capability.  It was solved by placing a 1 ohm resistor in series to take that inrush current out.

Apparently if multiple PVG's were powered from one output it had the same issue, so Danfoss developed a power cable for the PVG's with this 1 ohm resistor in series.  This was good enough proof for me.  Once the LED beacon was up and running there was minimal voltage drop across the resistor.

Cheers,

John.

bgtwuk

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Re: LED Inrush current causing Overload status
« Reply #2 on: September 24, 2016, 12:49:31 PM »
We often use a NTC thermister in series with the load. It limits load when cool and quickly warms up and allows full current.

Avalable at any electronics distributor.

Bgtwuk

Offline FluidPowerTom

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Re: LED Inrush current causing Overload status
« Reply #3 on: September 26, 2016, 05:35:02 PM »
Yep that's what we ended up going with was a NTC Thermistor.
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Hydra-Power Systems - Distributor - Pacific Northwest

Offline oiltronic

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Re: LED Inrush current causing Overload status
« Reply #4 on: September 29, 2016, 01:31:07 AM »
I like that solution.  Hopefully the LED's internal power supply decays slower than the NTC thermistor cools off, such that quickly cycling the LED off & on again doesn't draw too much current.

Offline Marbek_Elektronik

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Re: LED Inrush current causing Overload status
« Reply #5 on: October 01, 2016, 04:30:19 PM »
Have you used the PWM Output or the digital output?
Digital outputs can drive up to 17A for a very short time . So you can drive capacitors. (Infineon, PROFET® BTS 728 L2)
The PWM outputs are driven by MosFets and controlled by controller, if the current is more than 3A, they switch off with error.

Comes the error really by driving LEDs or by normal lamps?
Because mormal lamps have a high current (10..15x) by swithing on for some µs.
But LEDs have no inrush current. Or is there a capacitor?
Marbek Elektronik, Dipl.-Ing. Bernd Konrad
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