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

[René Schmitz]

Maybe use an NPN emitter follower as a pass element instead of the 
resistor. Doesn't load the converter, and you don't need heavy duty 
zeners either.

I.e. Vout from the boost converter, via resistor 1k to the transistor 
base, zener from base to gnd to delimit the voltage.


Best,

  René


Am 16.02.2024 um 17:45 schrieb 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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