Clearances in non-isloated offline 230VAC linear LED driver PCBs?

[treez]

How much clearance between copper (in mm) is needed concerning the positive DC Bus voltage net and the net of the thermal (centre) pad of the DT3001 230VAC Offline Linear LED driver IC?...

The schematic is shown on the 20th page of the following…

DT3001 Offline Linear LED driver IC:
http://www.seoulsemicon.com/_upload/Goods_Spec/Acrich2-Applicationnote.pdf

Also, how much clearance would you say was needed between the DC Bus positive net and the DC Bus negative net? (of the HV bus after the bridge rectifier)

The attached PCB layout shows that the via that carries the DC Bus positive trace to the DT3001 is given a full 1mm of clearance to the bottom thermal copper pour (which is connected to the thermal centre pad of the DT3001 IC). This unfortunately cuts up this copper pour and so can we make this clearance less distance?

 

[marce]

I would suggest you acquaint yourself with IPC-2221B section 6.2 onwards and especially table 6.1 (Electrical conductor spacing), as well as any relevant IEE/UL/ related specs. Also look up creepage and clearance, the relevant site will be obvious.

 

[treez]

Thanks pg 53
**broken link removed**

..our contractor says that there is another table for when these voltages are no isolated from mains electricity...and the clearances are greater in this case, due to the fact that the mains can suffer high overvoltage transients up to 6kV.....as you know, MOVs can fight this , but a 275VAC MOV will let through up to 900V.

 

[FvM]

You're apparently referring to overvoltage category in safety standards. Suggest to review the stuff yourself instead of quoting from hearsay.

You should however consider that it makes little sense to provide an insulation strength between two IC nodes that is a large multiple of the semiconductor breakdown voltage. It's just impossible to achieve the voltage with the IC in place.