Edit: 22/11/19 - updated navigation link

 

Following the rather disastrous last PCB update, I had it remade with a footprint that could take a 50uH inductor - and 10uH if I wanted to experiment.  Required a little jiggery pokery to fit the other parts around it but I also took the opportunity to rework some of the silk screen, layout, addition of a TVS on the input (D3) and re-size the mounting holes.

It’s all soldered up and back to working again thank goodness - I’m still kicking myself for misreading the 50nH inductor - with a controllable output voltage and current and nothing overheating or blowing. 

 

So the big reveal - has this improved?  For some reason, the scope has stopped recognising the USB key that’s plugged in so excuse the photos of the screen (and the dust!!)  I suspect something wrong with the firmware but that’s a problem for another day.  These readings were measured at the output capacitor with the short-wire ground probe, AC coupled, BW limited, 1x.

 

1.5A / 15V

10Ohm load with no voltage or current limiting:

 

0.050A / 0.5V

10Ohm load with current limited to 0.050A and voltage following:

 

I think I’ve every reason to be happy with these results right?  Mean Pk-Pk ripple voltage of 0.288mV and a max of 1.04mV from a Vin of 24V to an output of 0.5V is worth writing home about, right?

I’ll do more testing - soak testing, voltage overshoot and so on - but I’ve described these on previous posts so I’ll only repost if I see problems, or someone specifically wants to see them.

 

I’m on to encasement next.  I see the light at the end of the tunnel at last!

 

Next: Part 13 - Encasement and Wrap Up

Back: Part 12 - Design revisited: reworking the layout and PCB