The requirement for protection from 1000VAC Vin make this design problematic, as the primary switch will have to withstand at least 1400 VDC in its off state. This will require use of a stackfet design. Search the Power Integrations main web site for options using a stacked fet arrangement. The input filter capacitors will also have to withstand at least 1400 VDC if the maximum overvoltage condition is sustained. The input AC rectifier bridge will also need to be rated for this overvoltage condition, as well as any surge protection device placed across the AC line. The high voltage surge suppression components will be less effective for clamping  line surge events during normal operation.

Some good news, we have a new product with 1700V capability - details are here

https://www.power.com/products/innoswitch/innoswitch3-aq

Thank you ,

I do calculation for that and i am gating Warning while higher Voltage input apply , turn on time is too low in this case .

please advice your suggestion on Transformer design in this case , is that ok to go with warning in calculation ? ( I think as per my design specification i have very less (5-10W)

power design create issue and give warning message )

Regards,

Nikunj Mehta

Try increasing the transformer VOR (reflected voltage) to increase the minimum on time.

How far are you trying to push the input voltage? I want to try a spreadsheet myself to see the problem areas.

As per the application it looks like more then 350VAC ( or 440VAC) can feed about 10-15 min , as per the calculation and design our design can work / sustain large vin at least for 30min . ( Application - Street Light control unit , in rural / industry area electric pool supply is unstable and voltage can fluctuate randomly , so we have to design SMPS accordingly. ) 

Alternative Plan :- if it can't work efficiently then we can set burn out detection Vin voltage as 310VAC , and stop the switcher , make sure that our Design protect up to 440VAC or 600VAC Vin supply .( and yes Switcher work with efficiency 85-90% on Vin as universal range / 85 - 300VAC ) .

I ran a preliminary design using the 1700V Innoswitch for 85-440VAC input and 5V, 7W output power. The only caveat I could see is a rather low primary inductance due to using an oversized Innoswitch for this low power application. You may be able to get around this by designing the converter for higher power (say 15W or so), and using the supply at 7W anyway. Another option would be to use a stack fet design using a Tinyswitch or Linkswitch  so that the device is better optimized for the low power output of your application. The largest disadvantage of this approach would be that you lose the synchronous rectifier capability, which will lower efficiency. Losing the synchronous rectifier may not be that much a problem with a low power design like this one.