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That's a pretty big boost, not buck convertor to drive a TL072. Have you looked at the much smaller MT3608 based designs which are cheaper and should be able to handle a small load far better.</div>
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Also I always put a series 2N5551 as a capacitance multiplier with a Zener to ground across the capacitor to reduce the switching noise to negligable amounts.<br>
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<div dir="ltr" id="divRplyFwdMsg"><span style="font-family: Calibri, sans-serif; font-size: 11pt; color: rgb(0, 0, 0);"><b>From:</b> Synth-diy <synth-diy-bounces@synth-diy.org> on behalf of Jean-Pierre Desrochers <jpdesroc@oricom.ca><br>
<b>Sent:</b> 16 February 2024 16:45<br>
<b>To:</b> 'Synth DIY' <synth-diy@synth-diy.org><br>
<b>Subject:</b> [sdiy] BUCK stepup converter module... output goes way too high on startup !!!</span>
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<p style="margin: 0cm; font-family: "Calibri", sans-serif; font-size: 11pt;">Hi all,</p>
<p style="margin: 0cm; font-family: "Calibri", sans-serif; font-size: 11pt;"> </p>
<p style="margin: 0cm; font-family: "Calibri", sans-serif; font-size: 11pt;">I’m using this type of stepup voltage regulator to generate +15vdc and +30vdc</p>
<p style="margin: 0cm; font-family: "Calibri", sans-serif; font-size: 11pt;">From an incoming single +9vdc power adapter.</p>
<p style="margin: 0cm; font-family: "Calibri", sans-serif; font-size: 11pt;">These BUCK’S converters generate very good regulated voltage outputs but I noticed</p>
<p style="margin: 0cm; font-family: "Calibri", sans-serif; font-size: 11pt;">that on power up they ‘need’ to rise up to around +48vdc</p>
<p style="margin: 0cm; font-family: "Calibri", sans-serif; font-size: 11pt;">Before settling down to their trimmed voltages.</p>
<p style="margin: 0cm; font-family: "Calibri", sans-serif; font-size: 11pt;">Well these 2 voltages will supply a DSP module @ +15vdc (not more !!!)<br>
and a dual opamp TL072 that has a maximum allowed supply voltage of +/- 18vdc (36vdc overall).</p>
<p style="margin: 0cm; font-family: "Calibri", sans-serif; font-size: 11pt;">I tried putting a 16v zener diode in parallel with the trimmed +15vdc</p>
<p style="margin: 0cm; font-family: "Calibri", sans-serif; font-size: 11pt;">But the BUCK goes wild (input current rise up to around 2.5 amp and stays there !!)</p>
<p style="margin: 0cm; font-family: "Calibri", sans-serif; font-size: 11pt;">I also tried to put an RC circuit at the input (33ohms + 100uf) of one of these BUCKs</p>
<p style="margin: 0cm; font-family: "Calibri", sans-serif; font-size: 11pt;">But again the modules rise its input current to ‘try’ stabilize the regulation..</p>
<p style="margin: 0cm; font-family: "Calibri", sans-serif; font-size: 11pt;">Even with 100ohms resistors and 16v zeners.. the BUCKs won’t start<br>
and finalise their outputs (inrush current installs).</p>
<p style="margin: 0cm; font-family: "Calibri", sans-serif; font-size: 11pt;"> </p>
<p style="margin: 0cm; font-family: "Calibri", sans-serif; font-size: 11pt;">So.. I’m stuck with this problem..</p>
<p style="margin: 0cm; font-family: "Calibri", sans-serif; font-size: 11pt;">Any possible solutions ???</p>
<p style="margin: 0cm; font-family: "Calibri", sans-serif; font-size: 11pt;"><img id="x_Image_x0020_5" style="width: 13.5625in; height: 13.3958in; margin-top: 0px; margin-bottom: 0px;" data-outlook-trace="F:1|T:1" src="cid:fd464dca-ba5d-4d05-9971-02bb4dcdc202"></p>
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