Do PI parts have a UL, CSA or other safety agency file number?

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One question we see periodically from users is a request for the UL file number for PI parts.

The UL (or other safety agency) file number for a component indicates that it has met the safety requirements for that class of component. Components where this is a requirement are opto-couplers, Y and X class capacitors, fuses and (materials used in the construction of) transformers. All of these components either bridge the isolation barrier or provide a critical safety function.

Like most components on the primary, high voltage, side of a power supply UL certification is not required for a component that does not bridge the isolation barrier from primary to secondary. Examples include power MOSFETs, rectifier diodes and input electrolytic capacitors. However when parts are used that do not have certification and do not meet the operational spacing specified in UL60950 (or similar international variants) the power supply with be tested for single point faults.

Here single adjacent pins or PCB traces that do not have a sufficient creepage or clearance distance will be short circuited. The power supply under this single fault must not fail in a way that damages the isolation barrier or causes fire (emission of incandescent material). Short circuiting adjacent pins on PI parts generally either causes no damage or causes the input fuse to open - considered a safe failure. In addition the plastic compound used to mold PI parts is UL 94V0 rated meeting the safety flammability requirement.

Does this mean none of the Power Intergration parts are certified through any safety agency?

Yes, because there are no safety standards for MOSFETs or control IC's or similar non-safety-critical parts. (How would you get 1mm between the drain and source of a MOSFET?)


In UL/etc testing, the parts whose failure could cause a safety hazard need UL recognition (or VDE etc.); other parts don't.


You can't even find a common mode choke for a filter with safety certification, even though that component directly carries full line voltage. For a common mode choke, they are built with enough creepage and clearance to not be subject to failure in your product's evaluation. For a MOSFET or electrolytic capacitor or PI IC, the safety certification of your product will involve short circuiting the affected pins and making sure that the product does not fail in a hazardous manner.

Good and accurate answer.  The only product where this is not completely true is CapZero.  Here the product was tested to comfirm compliance to a specific set of requirements for X cap discharge components.  Details are on the product page 





In addition to the CapZero product line, Power Integrations products using the FluxLink™ isolation technology, like the InnoSwitch family, meet global safety ratings and are certified to UL1577/TUV60950CB and the more stringent CQC 5000m Chinese safety standard.


How do I access this compliance evidence (UL file numbers) for products that claim compliance (ie the InnoSwitch family)?

Hi Arie,

Thank you for reaching out to us through this page. If may I suggest, please create a "new" ticket for your inquiry. If you find that your inquiry is related to this thread then you may include this link in your "new" post. We will be waiting for your post.

Thank you and Regards,

PI-Lupin the Third