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NCP1028 Constant current LED driver. Which parts of the circuit to I need to ground? why is the current reaching kA?

My project aims to find out what happens when LED driver is connected to a triac dimmer, but I'm getting nowhere. The problem with which I have been struggling for months now, is that I can't make out why doesn't the circuit work as it should. I have followed th schematic of a ON semiconductor NCP1028LED Evaluation Board ( ) and used similar schematics awailable in NI page as an example, but it turns out that that is faulty too. First of all the diode rectifier is not right, one of the diodes needs to be rotated and whit that fixed it's still not working as it should. 

I need help! 

Big thanks in advance to anyone who tries to help 

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Message 1 of 13

I have focused in on the problem a bit

I've isolated the power supply and removed the ground from there. After that the simulation works a bit better but I still have peaks of current. 

I've found that the current must come from the filter after the rectifier as seen on this picture - the current probe is connected to the rectifier minus and the voltage comes from the plus side.

I've tried different filter options but I get the same result with all of them. 




There must be something else 

can someone please tell me whats causing the current peaks? 

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Message 2 of 13



I do not believe removing the ground from the power source is a good idea.


It seems that both of your circuits are working and I am getting this results:





Randy @Rscd27@
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Message 3 of 13

What is the expected behaviour?

Randy @Rscd27@
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Message 4 of 13
It's a led driver, the current should be in mA. The problem is that the filter after the rectifier isn't keeping the voltage leveled and is causing current peaks.
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Message 5 of 13

What is your OS? What is your Multisim version? 


I am getting a different behaviour and I have Windows 7 with Multisim 14.0.1

Randy @Rscd27@
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Message 6 of 13
Multisim 13 windows 10. Aren't you getting current peaks? What's the wattage you get?
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Message 7 of 13

I believe that Multisim 13 on Windows 10 could cause troubles based on this official document:


Only Multsim 14.0 or higher is supported on Windows 10. I am getting this results



If you want you can tell me wich oututs do you want and I can do a transient analyses.

Randy @Rscd27@
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Message 8 of 13

I upgraded my multisim to 14 and still ge the same results 

Problems I'm having:


Why is the sine wave like this at that point (before the rectifier)? if I ground one point then the wave is normal, but the current reaches kA again


The Current and wattage in the filter and the rectified voltage, why? in reality the combined wattage of the entire circuit would be around 1W.


Why don't I get wattage from the wattmeter? 



Also I discovered that NCP1028 has an average wattage of 47W which I believe isn't quite right either



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Message 9 of 13

Hello rauno.


I want to let you know that your questions are more related to the circuit functionality than an actual error in Multisim. I am not sure how the circuit should work. So there is not much that I can do for you. If you were getting an error it would be different.

Randy @Rscd27@
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Message 10 of 13