So I used a common 230vAC to 12vDc (1AMP) wall adapter with dc jack like thisenter image description here

and converted to 5v using a dc to dc buck converter same as based on lm2596s enter image description here
But the adapter LED starts blinking (normally the LED should just light up ) even if the output is not connected to anything.
My Question: Why is it happening and what can I do to overcome this issue?
update 1: I have tried using a 12vDC 20Amps SMPS and it works well.But not with the 12VDC 1Amps adapter


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Since the input capacitor has a low ESR the surge current may be up to 12V/ESR.

If the supply starts up with the Buck connected then a slow start might work with a suitable ICL, Inrush Current Limiter.

Ic = C dV/dt Choose 1A or get a variety of values with a 12~22 Ohm minimum R @ 25°C

TI's standard design shows 27uF 40 mOhm for Cin. Thus if the 12V output is cycling On and OFF with the Buck regulator connected, 12V/40mOhm = 300A ( in theory ) but in practice limited by supply.

enter image description here


  • Use a 1A ICL for a 1A source.
  • use a DC source with a soft-start and larger surge capacity such as a 19V 65W Laptop charger.
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    \$\begingroup\$ what software did you use to create the schematic and waveform? \$\endgroup\$ – Amrith May 28 at 11:25
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    \$\begingroup\$ so @ Sunnyskyguy ,Your point is that if I add ICL I can prevent the blinking(indicating high current flow).Also can you please explain the waveform Thank you very much for your answer \$\endgroup\$ – Amrith May 28 at 11:35
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    \$\begingroup\$ @Amrith The schematic/waveform are probably made on TI's webench \$\endgroup\$ – Huisman May 28 at 12:32

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