LNK305 Specification Buck or Boost-Buck?

Posted by: St7ven on 09/06/2016

Hi,

I was looking for an AC/DC solution then I found the LNK305. Now, I need to choose the topology. Between all topologies presented, the buck-boost shows this specification "Fail-safe – output is not subjected to input voltage if the internal MOSFET fails".

I do not understand what it really means. What kind of internal fail can occurs? and how can it affect the output voltage (overvoltage?).

Thank you,

https://ac-dc.power.com/sites/default/files/product-docs/linkswitch-tn_family_datasheet.pdf (page 6)

Comments

Hi St7ven,

Thank you for looking into our LinkSwitch family of devices.

The "internal MOSFET fails" meant that for whatever reason if in case the faillure mode is a shorted MOSFET the input will not go directly to the output because inherently for this topology the buck-boost inductor is across the line, it will short-out and blow the fuse. Further, when this shorted MOSFET happen the diodes are reverse biased and will block the rectified DC voltage from reaching the output.

Let me know if you need further clarification.

Regards,

PI-Picard

I am thinking of making a TOP switch offline buck in inverting mode which is another name for buck boost, hence it will be fail safe in event of switch failure and will guard the lower voltage down stream electronics from further damage and fireworks.

Hi Kanwar,

I agree.

Regards,

PI-Picard