it is all the day that I try to obtain a plot voltage V.S. currente
in this small circuit that I am try to designe
http://dunsscoto2.googlepages.com/FOLDBACK.pdf
the simulator gives me error and it says that current generator does
not converge
the someone more expert than me knows like resolving this problem?
I unfortunately am not practical of spice... and electronics in
general...
I have begun to use it from a few days in for construct
my first little dual power supply:
http://groups.google.it/group/sci.elect ... ce4a1d5d29

dunsscoto2@gmail.com wrote:
> it is all the day that I try to obtain a plot voltage V.S. currente
> in this small circuit that I am try to designe
> http://dunsscoto2.googlepages.com/FOLDBACK.pdf

That circuit won't work. R7 will prevent regulating
the voltage delivered to the load. For example, say
your load draws 100 mA. The voltage delivered to the
load will be the output of the 7805 (5 volts) minus
the 2.2 voltage drop in the 22 ohm resistor. ( 22 ohms
times .1 amps = 2.2 volts). If the load changes, the voltage
delivered to it will change - and it will always be below
5 volts. You need to do your current sensing on the input
side of this circuit, but it still fails. I suggest abandoning
it altogether and using one you can find in the datasheet.
But first, you *must* define how much current you want from the
circuit. You can't work out the component values without that.

Ed


> the simulator gives me error and it says that current generator does
> not converge
> the someone more expert than me knows like resolving this problem?
> I unfortunately am not practical of spice... and electronics in
> general...
> I have begun to use it from a few days in for construct
> my first little dual power supply:
> http://groups.google.it/group/sci.elect ... ce4a1d5d29
>

ehsjr ha scritto:

> dunsscoto2@gmail.com wrote:
> > it is all the day that I try to obtain a plot voltage V.S. currente
> > in this small circuit that I am try to designe
> > http://dunsscoto2.googlepages.com/FOLDBACK.pdf
>
> That circuit won't work. R7 will prevent regulating
> the voltage delivered to the load. For example, say
> your load draws 100 mA. The voltage delivered to the
> load will be the output of the 7805 (5 volts) minus
> the 2.2 voltage drop in the 22 ohm resistor. ( 22 ohms
> times .1 amps = 2.2 volts). If the load changes, the voltage
> delivered to it will change - and it will always be below
> 5 volts. You need to do your current sensing on the input
> side of this circuit, but it still fails. I suggest abandoning
> it altogether and using one you can find in the datasheet.
> But first, you *must* define how much current you want from the
> circuit. You can't work out the component values without that.
>
yes
you have reason
I have made the calculations newly and I have understood that he is
unusable
that I did not only understand because spice did not want to simulate
it
hour there are successful with a variable resistore as loaded
I would have intentional for the escape to 5V one protection similar
to this with the same currents
http://www.edn.com/article/CA624950.html
http://www.edn.com/contents/images/624950f2.pdf
I will try in an other way
thanks ehsjr!