When designing a PCB for a low-voltage circuit that connects to the mains, how much clearance must be used between the mains or primary side and the low-voltage or secondary side? This may sound like a trivial question but, unfortunately, it isn't. A typical example would be a mains-switching relay controlled by a microcontroller.

Common Safety Standards

For a product to be eligible for certification safety standards and norms must be applied. Here are a few "popular" ones:
  • IEC 60065 – Audio, video and similar electronic apparatus
  • IEC 60335-1 – Household and similar electrical appliances
  • IEC 60950-1 – Information technology equipment
  • IEC 62368-1 – Audio/video, information and communication technology equipment

In Part 1 of a series of three videos on determining the clearance and creepage distances for a PCB design we will have a quick look at these standards.

Video: PCB Design Creepage and Clearance 


Resources & Links

- IEC 62368-1 draft 4b
- IEC 62368-2 draft 4a
- Clearance & Creepage Part 1
- Clearance & Creepage Part 2
- Clearance & Creepage Part 3