Why my power supply works at a lower input voltage?

[codestar]

Hi,
I have made a power supply that takes 12 V input. This input goes to LM2576 regulator. The LM2576 gives a 5 V output which goes into LM1117 regulator which has a 3.3 V output.

The 3.3V output is used to run an AR9331 router.

The problem is that when I provide 12 V input to my power supply as required the router fails to boot. However, when I give 9V or even as low a 5.5 V input to my power supply the router boots perfectly.

Can anyone provide any clues as to why this might be happening? The LM2576 is designed to work for input voltages well above 12 V and for currents up to 3A.

Thanks.

 

[BigBoss]

Have you ever checked the Output Voltage (+3.3V) ? with an accurate DMM and Oscilloscope ??
There may be some spikes,noises etc.

 

[KlausST]

Hi,

The most often self made SMPS issues:
* wrong PCB layout
* saturating inductor

Klaus