Yet Another Inrush Current Limiter

Here is yet another inrush current limiter. The circuit is straightforward, and component values need not be precise. Also attached are two plots: one showing the line current with the limiter and the second without the limiter. Needless to say, the large current/voltage transients encountered without limiting are not good for the life of the filter caps or other components.

I have implemented this circuit and variants thereof for both inrush limit and output connect, where the latter was used to prevent turn-on transients from appearing at the amp/preamp output. The circuit also implements asymmetric turn-on and turn-off characteristics, such that a transient line power loss results in a reset and full delay time to relay close.
 

Attachments

  • Inrush_Limiter.JPG
    Inrush_Limiter.JPG
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  • InrushCurrentWithLimiter.JPG
    InrushCurrentWithLimiter.JPG
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  • InrushCurrentNoLimiter.JPG
    InrushCurrentNoLimiter.JPG
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