LNK306

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Dear Sir, I read a document "3-Phase AC/BLDC High Voltage Power Stage Board" from Freescale semiconductor company. They used LNK306 (please see the picture) after the bridge rectifier and the input of LNK306 is DC voltage (320 V DC). Is this configuration possible? We were looking a way to produce 18 V DC from 320-560 V DC servo driver bus voltage for the gate driver ICs. Best Regards, Vedat

Yes such a configuration is possible.

Have a look at the product family page:
http://www.powerint.com/en/products/linkswitch-family/linkswitch-tn

and appnotes, where such a "buck converter" (the name of the topology) is described:
http://www.powerint.com/sites/default/files/product-docs/an37.pdf

I also presume that Freescale tests their published circuits as well as Power Integrations does! They added C409 - I'm not sure why - it might be a kludge for a layout related problem.

Dear Sir, You mean the capacitor in the red circle, don you? We will add ir if your design does not workproperly best regards,
Hi, i am working in a desing using that IC, and that capacitor must be there, at least i think that for what i read in the AN-37: "If the total system capacitance is >100 µF or the output voltage is >12 V, then during startup the output may fail to reach regulation within 50 ms, triggering auto-restart operation. This may also be true when the load is not resistive, for example, the output is supplying a motor or fan. This is not applicable for the LNK302 as it does not have the auto-restart function. To increase the startup time, a soft-start capacitor can be added across the feedback resistor" I hope u find this usefull, i also want to suggest you to read the AN37 which is a design guide for this LinkSwitch family.