Creepage distances for offline SMPS

[opampsmoker]

Hi
Can I just check that in an offline SMPS in UK,EU,USA, the primary to secondary conductor creepage distance should be >=8mm?

We have a student with us whose father is a Top Expert Chief Power Electronics Engineer, and he says the rules have just changed and its now 5mm.

Also, this student has layed out a 70W Offline Flyback for us. He has L,N & E connections to the primary mains input connector. The earth is then tracked onto the PCB and picks up the Y capacitors at the primary side. ...Also, this earth copper is then tracked to the primary FET heatsink PTH's to which the plastic TO220FP FET is affixed. However, he has then continued to track this earth on the bottom layer from primary to secondary side. First this earth connects to the secondary diode heatsink’s PTH holes. (TO220 diode). Then this earth continues throughout the secondary side where it connects to a PTH to which the earthed metal “cage” is soldered into. This cage is “holy” and is to reduce radiated emissions as it kind of “box covers” the top PCB side of the entire SMPS.

…So, the earthed copper is on primary and secondary sides. However, on both primary and secondary sides this earthed copper tracking/pouring is less than 1mm away from primary and secondary metal conductors.

He says his father told him that all this is right and the regs have just changed.

However, do you agree this is not the case, and his SMPS is very bad?

 

[gophert]

Thanks for sharing here. This is exactly what this website is for - second-guessing designs developed by children of "Top Expert Chief Power Electronics Engineer"*. We are here to help. Certainly don't bother to higher professionals, the osmotic knowledge gained by your student designer is much higher than any normal engineer, the student is, after all, the child of "Top Expert Chief Power Electronics Engineer". Although we are here to help, I don't know why you think us who are not children of "Top Expert Chief Power Electronics Engineer" might have better knowledge.

Please let us know what major area of study this child of "Top Expert Chief Power Electronics Engineer" might be? From my experience, children of people with very powerful titles like this usually have majors like, French Art History, Comparative Literature, General Studies, Recreational Sports and Mindfulness.

* I looked on LinkedIn and realized there is less than one person with this title,Top Expert Chief Power Electronics Engineer, so you should be very pleased to have his/her child designing a system for you

 

[AnalogKid]

Schematic? Layout images?

ak

 

[gophert]

Schematic? Layout images?

ak

Use your imagination.
Also, any answer can also be creative writing.

 

[shortbus=]

Still think this guy is flyback under a new name.

 

[JimB]

Still think this guy is flyback under a new name.

He certainly is.

JimB

 

[Mickster]

And ‘zenerbjt’ too...

 

[shortbus=]

He certainly is.

JimB

If that is so and you moderators know it, is that an allowed thing? Most forums if someone leaves under one name they aren't allowed to rejoin under another.

 

[ChrisP58]

Hi
Can I just check that in an offline SMPS in UK,EU,USA, the primary to secondary conductor creepage distance should be >=8mm?

We have a student with us whose father is a Top Expert Chief Power Electronics Engineer, and he says the rules have just changed and its now 5mm.

.....

What does the current version of the applicable safety standard say? That's what matters.

The 60950 standard has been replaced with 62368, so it's quite possible that things have changed, and that your student is correct. But YOU need to read it and make sure what YOU think is acceptable for the operational conditions.

 

[ChrisP58]

What does the current version of the applicable safety standard say? That's what matters.

It looks like the 60950 standard has been replaced with 62368, so it's quite possible that things have changed, and that your student is correct. But YOU need to read the standard and make sure that YOU know that the spacing is sufficient for the operational conditions.

 

[MacIntoshCZ]

However, do you agree this is not the case, and his SMPS is very bad?

1kV = 1mm in "normal" circumstances...
325V * 5 = 1625V; It should be ok.
also PC817: in mm

 

[MacIntoshCZ]

BTW i would like to ask if those standarts are free to use in US? Cause in CZ i need to pay for reading it, and extra pay for printing it...

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