Which components need UL Approval

[engineer1000]

I'm trying to find a linear regulator LM7805 with UL approval. I can't find a single one with UL approval . We are thinking about trying to get a product UL approved but it is very sketchy which components need UL approval and which don't. I've been told only safety critical components, but that could be any component depending upon the design, so I'm really confused You would think that UL would have a search engine with all approved components stored in it but they don't. It seems to me at the moment that engineers are kept in the dark so UL can make more money. Can anyone help???

 

[FvM]

I've been told only safety critical components, but that could be any component depending upon the design.

There's a second point besides "safety critical". An UL approval makes only sense for components that are able to provide safety in an application, e.g. safe insulation, current or voltage limiting. That's clearly not the case for a simple voltage regulator. It must be expected to fail and the circuit has to be designed in a way, that the component failure doesn't bring up a safety risk, e.g. fire hazard or exposure of dangerous voltages.

 

[engineer1000]

There's a second point besides "safety critical". An UL approval makes only sense for components that are able to provide safety in an application, e.g. safe insulation, current or voltage limiting. That's clearly not the case for a simple voltage regulator. It must be expected to fail and the circuit has to be designed in a way, that the component failure doesn't bring up a safety risk, e.g. fire hazard or exposure of dangerous voltages.

Thanks for that. So I think that you are saying that the LM7805 doesn't need UL approval as if this component became faulty the design should be such that the fault would not cause a safty risk or fire hazard

 

[FvM]

Yes. Good design practice, e.g. keeping component maximum ratings with sufficient margin would be presumed.

Most likely, the 7805 is part of a circuit with limited supply power (< 150 W), guaranteed by suitable UL approved fuses. If the circuit has a safety function itself, or isn't operated with limited power, it becomes part of the approval.

This are only basic rules of thumb that I remember from previous UL involvement. The experts can tell you more regarding your actual design.