Soft Start/Inrush Limit for 0_30Vin design with PMOS/Transistor/OpAMP?

[TuAtAu]

Hi Guys,

Do you all have any idea to design a PMOS with either 1 of Transistor/Op Amp/any active element to have the soft-start or inrush current limits control?

I tried some with a sense resistor series with the power line, and use a PNP to sense the voltage drop on that resistor and turn off the PMOS once it is over some current.
But the Vin expected to have 30V and 4A input, the series resistance will have a quite significant voltage drop to reduced the efficiency and line regulation.

Any other thoughts?

Thanks

 

[FvM]

An example of a 0.2A/15V current limiter using a rail-to-rail OP. Dimensioning has to be adjusted respectively, MOSFET Vgs rating might require additional voltage limiting or limited OP supply range. Voltage input is on the right circuit side.

 

[TuAtAu]

An example of a 0.2A/15V current limiter using a rail-to-rail OP. Dimensioning has to be adjusted respectively, MOSFET Vgs rating might require additional voltage limiting or limited OP supply range. Voltage input is on the right circuit side.

Hi FvM,

I did the simulation and the softstart seems work! So thank you!

But! there is another question that I wish to ask:
https://www.edaboard.com/threads/292428/#post1250511

 

[FvM]

I can't recognize that the circuit works at all. Apart from unrealistic supply timing and LT1218 being essentially too slow for this application, the OP doesn't even work with much slower overcurrent events.

You also didn't care for MOSFET maximum Vgs rating.