Re: Power supply softstarts

Sorry is there any schematic avaiable in order to implement the soft
start circuit. I would like add an soft start circuit at my ps

I have found the next page what circuit you think is suitable in order
to made soft start.
http://sound.westhost.com/project39.htm

Look like people is burning geckos beacause they are not incoporating
the soft start circuit.
Is there any recommendation from Mariss ?

Thanks in Advance




--- In CAD_CAM_EDM_DRO@yahoogroups.com, "turbulatordude"
<dave_mucha@y...> wrote:

>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Graham Stabler" <eexgs@n...
>
> wrote:
> >
> >
> > I asked a lecturer in electrical enginnering about this, despite
> > being a lecturer he is very practical ;)
> >
> > "I KVA is about 4 amps. A big supplly current. Toroidal
> transformers
> > have an excellent efficiency due to having no small air gaps in
> their
> > magnetic circuit. Unfortunately this means that they can retain
> flux
> > on swiths off of the supply. If they are switched on at voltage
> zero
> > such that the rate of change of flux required causes the
> transformer
> > flux to grow in the same direction as the residual flux then
> > saturation quickly occurs as the flux is offset by the residual
> > value. The only current limit is then the resistance of the

primary

> > winding and the very low leakage reactance. Hence bang. 1KVA

should

> > not be enough to blow the fuse though normally.
> >
> > The very big capacitor with no current limit on the input will
> > compound the problem of current surge as again there is little to
> > limit the current.
> >
> > The simplest solution would be additional primary resistance on a
> > timer as Ron (enother chap I asked) says."
> >
> > So I will go for some form of power resiter on the primary,

shorted

> > by some means after some time. No need for ebay parts, I have a
> > budget :P
> >
> > Cheers,
> >
> > Graham
>
> Sounds like a good plan.
>
> If you read up on the thermistos, they are similar to resistors but
> vary with temperature, and are much less expensive than power
> resistors.
>
> Regardless, once you bypass it, who cares.
>
> My questions is why the gigantic capacitor ?
>
> Most of the calculations I have done on the power supplies yields
> capacitors in the 10k to 20k uF range, Never the 100k Uf range.
>
> Dave