PFS712 load vs. power supply

Hi,

PFS712 is a universal input device, which can deliver upto 225W at 90V AC input.

For PFS device lowest input voltage is the worst case condition, if the PFS device could deliver the certain amount of power at lowest input voltage then it can deliver the same amount of power at highest input voltage as well.

Since your operating input voltage range is 180V AC to 230V AC, I would recommend you to use PFS726EG device which can deliver the required ouput power (450W) over the given input voltage range.

Regards,

PI-NANO

Hello,

thank you for answer. But in our case somethimes the lowest voltage can be 150V AC, therefore we chose the

PFS71x family to operate. What can happen if more power is desired like PFS71x is specified? Would be just

more power dissipations or some other thermal current protection will activate?

When I am looking data sheets, there is no difference mentioned between devices, except, that Rdson of integrated

MOSFET is different, what lead to more power dissipation! 

thanks and best regards 

Hi,

If you use a low power rated device, PFS device will enter into power limit mode and might not be able to deliver the required 400W. If you are in final stage of your design, I would suggest you to replace the PFS part with PFS716 part (provided all other components are rated for 400W in the design already).

Regards,

PI-NANO

Hello,

so If I understand correctly we can use PFS operating near PEAK output power, but above lower supply

limit. So PFS716 operating with 400W output power and power supply ranging 150 - 230V AC can operate

stable and will maintanin stable output voltage and harmonic distorsion within limits like for FPS714 measured in

RDR-236 application note.

When you mentioned, that device can enter into power limit mode, the output will be fully disconnected, or output

voltage will be lower then calculated 380V?

You also mentioned FPS716 design for 400W, but I can only find design of FPS714 (347W output.)! Could you send me a link to this design please!

Thanks an best regards,

Hi,

Yes, PFS716 can deliver 400W ouput power and it can maintain regulation..

As you keep on increasing the load, the output voltage will go down once the device enters into power limit mode.

At this point of time we have reference design for PFS714. But unfortunately we don't have a reference design for PFS716. But the design procedure is same as PFS714.

You can use PIXls designer to design with PFS716. PIXls designer is a free downloadable software available Power Integration's website. You can find the PIXls designer at following location.

http://www.powerint.com/en/design-support/pi-expert-design-software

Regards,

PI-NANO

Hello,

thank you for a tip. I downloaded SW and checked our design. On design schematics I have noticed, that

there is Csn1 capacitor which should be used for universal design > 350W. This capacitor is in paralell with

PFC fast diode!

Do you ahev any guideline for value/type of this capacitor, because I can notfind it in design.

regards,

Toni

Hi,

Csn1 is used to snub the voltage spike on PFC MOSFET. You may not be required to use this capacitor If the loop area is small. But I recommend you to have a place holder for this capacitor. If you observe a voltage spike the drain, then I suggest you start with a 22pf / 1KV, NPO capacitor and optimize it further after checking the waveform on bench.

Regards,

PI-NANO