Hoffman Amplifiers Tube Amplifier Forum

Other Stuff => Solid State => Topic started by: kagliostro on November 17, 2013, 04:38:45 am

Title: Is this an inrush current limiter ??
Post by: kagliostro on November 17, 2013, 04:38:45 am

Some time ago I did a search about a mosfet circuit to be used as inrush current limiter

now I've found on my PC the attached schematic

I'm not sure about it, but I think that it is an inrush current limiter (and so I labeled it that way)

Please can someone confirm if the purpose of the circuit is that ?

Many Thanks

K

Title: Re: Is this an inrush current limiter ??
Post by: sluckey on November 17, 2013, 06:41:35 am

Yes, you could call it that. Or call it a 'soft start' circuit. When you apply B+ to the input, C1 slowly charges exponentially thru R1. This voltage on C1 takes about 5 R1C1 time constants to fully charge to the applied B+ level. This voltage is applied to the gate of the source follower MOSFET. The voltage on the source follows the gate voltage. So, the overall effect is that the output voltage slowly rises to the input voltage level. You can slow this action even more by increasing either R1 or C1.

Title: Re: Is this an inrush current limiter ??
Post by: kagliostro on November 17, 2013, 07:06:06 am

Many Thanks Steve

Franco