Inductance

Thread Starter

Chillum

Joined Nov 13, 2014
546
Hi, will a higher inductance inductor effect a circuit rated for a lower inductance inductor, say for 12V operation we require 100uH, but for a 36V operation we need 150uH, do I have to build 2 circuits one for 12V input and one for 36V input or would the 36V input work with the 12V input.

If inductors are like capacitors, then I'm guessing there'll be no problem.

Please advise
 

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Kermit2

Joined Feb 5, 2010
4,162
The circuit diagram is incomplete. there are no active devices shown nor any connection between the two power sources. the current changes from the series inductor will be delayed in relation to the voltage level changes, so the different vslues may be very important. without the whole circuit we can only guess if such a substitution is allowable.
 

Thread Starter

Chillum

Joined Nov 13, 2014
546
HUH!? heres the veroboard layout for this circuit (traced with colour to show energy), maybe that'll help. Actives is shown by that Battery called Vout battery Vin is connected to LM2576 in pin 1 and output pin 2.
I can assure you it works, I've built one. The square on the SIL5 pakage is pin 1, square is positive, and circle is negative, and square on the diode is the line on the package. VeeCAD is the software usedswitchingRegulatorColoursV2.png
 

Kermit2

Joined Feb 5, 2010
4,162
my apologies. i mistook the LM2576 for a 5 pin connector. (small viewscreen on this phone).
the chances are good you will not have a problem with a single value inductor for both high and low voltage, test it out and see what you get with a 150uH instead of the 100. shouldnt see any change i would think.
 

Thread Starter

Chillum

Joined Nov 13, 2014
546
thank you kermit2 that's what I hoped for, getting parts later this week then I'll report back with my findings
 

crutschow

Joined Mar 14, 2008
34,282
An inductor is not rated for voltage (except for the insulation breakdown voltage) but it is rated for maximum current before the core saturates. So it's the current rating of the inductor versus the maximum inductor circuit current that you need to be most concerned about.
 

Thread Starter

Chillum

Joined Nov 13, 2014
546
output voltage 36-2=34 variable to 1V input voltage 36 or 12 its the or part i'm worried about, If I build for 36, will it work for 12?
 

Thread Starter

Chillum

Joined Nov 13, 2014
546
your'e not reading!
INPUT 36 or 12
OUTPUT 36-2=34 variable to 1
34V out is obviously for 36V in, 12V in will OUTPUT less than 10
 

ronv

Joined Nov 12, 2008
3,770
Then why didn't you say that? :D
To properly calculate it you need input, output voltage and current for each.
What do you plan to do about the adjustment?
 

ronv

Joined Nov 12, 2008
3,770
You will be able to get a little over 1 amp out of it with 12 volts in and 10 volts out and a 150Uh. inductor.
You should check the data sheet for your diode. It's to small.
The voltage on the input cap is to low for 36 volt operation.
R1 doesn't need to be so big. When the pot is set to a low value the output voltage will be low.
http://www.ti.com/lit/ds/symlink/lm2576.pdf
 

Thread Starter

Chillum

Joined Nov 13, 2014
546
please help me pick diode, fort777.co.za have 300v but no stock, Mantech I don't know what to pick 'cause those labelled fast is only 30V: http://www.mantech.co.za/Stock.aspx?Query=schottkyand

EDIT Is the diode to be rated for output or input voltages?

What do you gain with fast recovery, None of the 5 suppliers in the Cape (Cape Town) have fast recovery Schottky diodes rated higher than 30V fort777.co.za had one but it was discontinued so NOTHING. The table 1 has a normal side and a fast recovery side, why fast recovery when you can have normal, now I have to go with the 1N5822 because it's the only one I can get. Mean Well (the makers of my 36V PSU, says the V+ ADJ can get me down to 32V, for diode selection
[
B. The reverse voltage rating of the diode should be at least 1.25
times the maximum input voltage.
]
32x1.25=40, the rating on my diode, cutting it fine, but when working with such a low amount of components available, thats what I got
 
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