Attack of the ripple monster? Building a Homebrew Benchtop Power Supply using a RuiDeng DPS 5005
I’ve had a bench top power supply for a while - it’s invaluable to be able to dial in the required voltage and also see what sort of power draw your circuit has. My old supply was linear - so it was heavy and bulky!
I’d seen a few projects where people built their own bench top power supplies using the RuiDeng DPS 5005 - so I set out to do the same. After spending ages scouring AliExpress, I found a suitable enclosure (220*195*80mm Iron metal enclosures for electronics junction box diy electrical instruments box) and some very compact 300w switch mode power supplies (Dual Output Power Supply 48V 12V Led Stage Lights Driver Led Moving Head Power Supply 300W SMPS).
The power supplies were well specced, but the reason they are so compact is because they have a fairly high ripple voltage (advertised at 480mV p-p). With that in mind, I set out to build my PSU.
Cutting holes for the fan and to mount the two SMPS:
Both SMPS in place (with thermal grease underneath)
Fan clearance - its pulling air in from the bottom and it goes out through the top past both SMPS.
Top down with wiring
Close up of wiring
Cutting holes for the two DPS 5005
All up and running - pushes 500w without getting warm!
What about ripple?
At full power - 50v ~250w - we get 314mV p-p and 21mV Rms:
At 25v ~60w we get 178mV p-p and 25mV Rms.
At 12v ~15w we get 112mV p-p and 15.6mV Rms
At 5v ~2.5w we get 82 mV p-p and <10mV Rms
Adding two large capacitors on the output doesn’t help at all - here we have 50v again with two 1500uF caps:
So there you have it - a capable compact power supply, but watch out for the ripple monster!
