I'm using a cheap chinese XL6009 adjustable converter module to boost 5 V to 12 V. To test this converter, I used a 5 V supply, a 120 Ω ohm load to draw 100 mA current (100 mA at 12 V is the requirement of my target circuit), hooked up a DMM to monitor the voltage and an analog current meter in series with the load, and connected an oscilloscope across the load. It was drawing about 0.25 A from the source (a regulated lab supply), to give an efficiency of 96%, but the results were not particularly promising (here, V/div = 50 mV and T/div = 0.5 µs): .
I housed the converter in a metal enclosure, and there was a definite improvement in the ripple characteristics (here, V/div = 10 mV and T/div = 0.5 µs):
Even then, these 40 mV spikes will eventually kill the capacitors in my target circuit.
Just to test, I ramped up the boost converter to 15 V and then hooked it up to a 7812 with 1 m wires running from the enclosure of the converter to the breadboard on which I have my regulator. The input side filter capacitor is 470 µF and the output side one is 22 uF (I tried many combinations but it didn't make much difference). I can't embed more images directly, so it's here (V/div = 5 mV and T/div = 0.5 µs): https i imgur com M43un2W jpg (sorry).
What am I doing wrong and how can I fix it?