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Flyback PFC output goingabove 42V

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treez

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Hello,
Our LT3799 based 15W Flyback PFC converter is giving an output which is rippling from 36V to 44V. (at 100Hz)

Since the output voltage goes above 42V (42V is the SELV level), does this mean that it is too dangerous to allow semi-skilled test technicians to work on it?

Does touching 44V in one hand and ground on the other mean you die from electrocution, because its above the 42V SELV level?
Does touching 41V in one hand and ground on the other mean you don't die from electrocution, because its below the 42V SELV level?
 

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Don't no which standard you are referring to, but SELV maximum DC level isn't 42 V, rather 60V.
 
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treez

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So does that mean that if someone holds 60V in one hand, and the common in the other, then they will not get a heart attack?.....I presume this is the basis of the SELV rating.?

https://en.wikipedia.org/wiki/Extra-low_voltage

it looks to me from wiki that as long as one has proper mains isolation, and no return path through earth ground available, then one can be allowed to touch significantly more than 60VDC?...say up to 80VDC?
 
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In fact I was asking for the applied standard because I may be unware of recent changes. My reference is IEC1010 that says

30 Veff
42.4 Vpeak
or
60 VDC

The regulation is based on the assumption that (low frequent) AC is more dangerous than DC because it can cause ventricular fibrillation.

There are additional regulations for critical zones with the risk of widespread skin contact (e.g. work inside tanks) or wet work places.
 
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treez

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it can cause ventricular fibrillation, but not if its less than 60VDC or less than 42VAC (50Hz)..?

Sorry to ask, but the regs just don't say that its connected to a risk of death, but surely it must be?

I went to an interview with IBM, for working on their server power supplies, and the interviewers looked at me very doubtfully when I said that I thought a properly isolated 50VDC was safe to touch.
 

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Thje critical parameter for pathological effects is current, not voltage. In so far there's no clear voltage limit, regulations are based on certain assumptions of skin resistance, contact area etc.
 
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