How can we increase soft start time for VIPER319XDTR?

[Kshah.21]

Dear sir,

We have followed STEVAL-VP319X1B development board schematic for converting 110V/230V AC to 5V DC. In one of board we found that inrush current limiting resistor is burn out. We have followed same part number for resistor which is in development kit BOM. Can you suggest how we can increase soft start time.

Thanks

Kadam

[Kshah.21]

Hi Peter Bensch,

If you used in any reference design, can provide suggestive PTC part number.

However with 10E 3W (R24), so far we haven't seen any burning issue.

Thanks

Kadam

[Peter BENSCH]

If a PTC is an option, please contact PTC manufacturers as the correct part should be carefully selected.

Regards

/Peter

[Kshah.21]

Hi Peter Bensch,

We are planning to use PTC : PTCEL17R600MBE.

Please share your thought for PTC.

I have attached datasheet for your reference.

Thanks

Kadam

[Kshah.21]

Hi Peter Bensch,

PTC is quite costly as compare to inrush resistor (metal oxide, flame proof).

Currently we are using 10E, 5W resistor (ROX5SSJ10R).

I have attached datasheet for reference.

Do you feel tuning compensating network tuning can help us?

Thanks

Kadam

[Peter BENSCH]

With this PCTEL there are probably only PTCEL17R600MBE or PTCEL13R600LBE in question, because the hold current is just sufficient, but you must then also take its losses into account.

On the other hand, a 5W resistor is of course also an option if its size is not a problem.

Tuning the compensation network unfortunately does not help at all with inrush current, but can improve the phase margin and other parameters depending on the input and output parameters.

Regards

/Peter