In article <31EEC08C.7F1A@eduserv.rug.ac.be>, Vandenbruaene Jon
<jjvdenbr@eduserv.rug.ac.be> wrote:
>
> I am making a +80/-80 power supply with 317's and 337's. It must give
> a current of about 1A max. How do I make it short-circuit proof,
> because when the output is a short, the input terminal is at 80 V
> and the output at 0 V, and the 317 can only have a 40 V input-output
> difference so it will be broken. (I only use voltages between
> 80V and 40V, so it is not really a "normal" power supply)
>
> I also want to put in a adjusting current-limiter-function, so I can
> change the max. current from 100mA to 1A.
What you need is a 'following pre-regulator. The attached UUE/GIF file shows
the idea. The two resistors define a point half way between input voltage
and output. The power transistor 'follows' this point so that it shares
voltage and power with the regulator proper.
You can put current limit around this follower.
If you need more details please contact me.
<iimage A>
RiscOS filetype : 695
--
/| Richard Torrens - 4qd@argonet.co.uk
/ |
/ | 4 Q D
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Date: Fri, 19 Jul 1996 17:17:17 BST
Original Subject: Re: How do I make a 80V power supply with 317's and short ci...