Inrush Current Limiting

Paul Litwinovich paull at WSHU.ORG
Mon Oct 4 22:34:38 EDT 1999

Guy AC5HL wrote:

(snip)>This brings up an interesting point for an inrush current limiting
>I have been looking for a slow turn on device (other than current limiting
>thermisters which come on pretty quick and don't do any good if already
>heated up).

Simple fix, build a delay circuit which could be as simple as an RC network,
to close a relay or turn on a triac across the thermister a second or two
after power is applied. This will allow the thermister to cool so it is
ready to do it's job again even when the power has been on for a while and
then briefly interupted.
This is a common practice in the switch mode power supply industry. It also
adds to efficiency by not wasting power heating a thermister while the
supply is running.

15 years in switch mode power supply design,
now playing radio and having much more fun!
Paul Litwinovich

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