Finally some testing!
Typically 5V on the ST is around 1.2 - 1.8amps.. Here I am loading 4.5amps.
12V almost nothing uses it anymore, but I am loading with 2amps.
Efficiency isn't great at these high loads on both rails, but approx 88% which is a lot better than my previous design. 88% is still very good anyway.
5V only load on 2.5amps is about 92% efficiency. Lower loads around 1.5A are probably even better efficiency. Maybe around 95%. So its about as good as things get!
( as a side note, my PSU may say 15.1V (well it did when I re-tested) , but actually on the PCB its 14.1V, so if anyone uses the meter readings from below, will get worse figures than I calculated. But these are only quick tests anyway.)
- IMG_3284.JPG (75.62 KiB) Viewed 5934 times
EDIT:
..and the ripple & noise on the 5V rail under 4.5amps load..
- 5v______.png (80.84 KiB) Viewed 5932 times
Pretty much 20mV p-p ( 0.02V) total ripple and noise (mostly noise) So really pleased about that figure. Actuall ripple is almost nothing, about 2mV (0.002V).
Note - x10 probes used in the above test.
EDIT2:
Efficiency figures are done powered from my bench power supply, so this does not include efficiency loss in the main toroidal transformer (which are generally very high efficiency anyway) and does not include efficiency loss across the bridge rectifier. Though I have used schottky diodes for lowest voltage drop and highest efficiency possible. So the entire design really cannot be made any more efficient than it currently is now anyway.
EDIT3:
The crowbar protection on my old PSU was on the 5V and 12V rails.. On this new PSU it is also on the main DC input from the rectifier (about 15VDC) with a trip of about 20VDC. This was talked about before, but should there be any nasty mains surges which may last a while, or enough to overcharge the main reservoir capacitor, the fuse will blow to protect the 5V and 12V regulator circuits and of course the computer attached.
The trip voltages for 5V and 12V are approximately half a volt higher. So should the 5 V rail go higher than approximately 5.5V, will blow the fuse and cut power. Of course in reality there should be no circumstances where this could happen unless there was huge catastrophic failure like someone drops a screwdriver across the PCB etc!
EDIT 4:
Small change from previous designs was to use normal through-hole resistors for the voltage feedback network. I did this as the PCB can get warm over time and I did not want to risk "cooking" smaller SMT resistors over time. So I used general through-hole resistors on the 5V regulator and will lift them the PCB a couple of millimetres to allow some airflow around them. The problem with resistors and indeed the parts, is as the temperature profile changes, so does the output voltage. So wanted to minimise this drift by keeping the resistors out of the heat path as much as possible.