[sdiy] BUCK stepup converter module... output goes way too high on startup !!!

[Jean-Pierre Desrochers]

Hi all,

 

I'm using this type of stepup voltage regulator to generate +15vdc and
+30vdc

>From an incoming single +9vdc power adapter.

These BUCK'S converters generate very good regulated voltage outputs but I
noticed

that on power up they 'need' to rise up to around +48vdc

Before settling down to their trimmed voltages.

Well these 2 voltages will supply a DSP module @ +15vdc (not more !!!)
and a dual opamp TL072 that has a maximum allowed supply voltage of +/-
18vdc (36vdc overall).

I tried putting a 16v zener diode in parallel with the trimmed +15vdc

But the BUCK goes wild (input current rise up to around 2.5 amp and stays
there !!)

I also tried to put an RC circuit at the input (33ohms + 100uf) of one of
these BUCKs

But again the modules rise its input current to 'try' stabilize the
regulation..

Even with 100ohms resistors and 16v zeners.. the BUCKs won't start
and finalise their outputs (inrush current installs).

 

So.. I'm stuck with this problem..

Any possible solutions ???



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