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

[The SynthiMuse]

Hi Jean-Pierre
It might be a load issue. Most buck regulators need a minimum load of about
5% to 10% of their max rating.
It could be that you're not loading it appropriately and it's struggling to
establish on startup.
Not a solution, but if you give it an appropriate resistive load, it might
give you an insight in to the problem.
Best wishes
Gerry


On Fri, 16 Feb 2024, 16:50 Jean-Pierre Desrochers, <jpdesroc at oricom.ca>
wrote:

> 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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