Reviews - Pico PSU Round Up
Sample Provided by: Logic Supply (By jonny on Wed, Nov-10-2010)

Page 3 - Load testing our power bricks

When using a PicoPSU at home, the first thing we need to do is convert AC power to DC, so the first thing we're going to test is the power bricks. This is so we can see what kind of efficiency we get, as this will effect the efficiency we get once the DC to DC power supplies are plugged in, and what our ripple looks like, hoping that maybe the DC to DC power supply can filter out some additional ripple.

We're going to use the same testing methodology on these power bricks and the PicoPSU's that we use on full size desktop power supplies. The SunMoon SM-8800 puts an artificial load on multiple DC output rails at the same time. The output power and input power are measured and efficiency calculated, as well as power factor. We use an oscilloscope to measure the AC ripple on each rail.

The first PSU to go onto the load tester is the EDAC 102W...

EDAC EA11203A 12V power brick

Test #

+12V

DC Watts/
AC Watts

Eff.

Power
Factor

Simulated system load tests

Test
1

2A

24.6W/
30.3W

81%

.95

12.34V

Test
2

4A

48.9W/
57.4W

85%

.98

12.23V

Test
3
6A
72.8W/
85.5W
85%
.99
12.14V
Test
4
8A
96.3W/
116.2W
83%
.99
12.04V

Note the +12V output starts off very high. Under nearly full load, it drops to 12.04V. Voltage regulation isn't what we're used to seeing with an ATX power supply as the +12V drops 2.5% going from test 1 to test 4. That said, we are talking about a power supply that is much smaller than an ATX power supply as well. We should also note the efficiency here. Not bad at all as it's consistently above 80 Plus, but nothing too spectacular.

Now let's have a look at the ripple. Ripple is the small variations in the DC voltage that was not successfully filtered out of the AC coming into the power supply. We want as little ripple as possible coming from the power supply, because any ripple that the power supply doesn't clean up, the components that the power supply is feeding power to will need to suppress.

Oscilloscope Measurements for EDAC EA11203A

 

Test 1

Test 2

Test 3

Test 4

+12V




During test 1, we only see about 20mV peak to peak. This gradually grows to 50mV, 70mV and then finally 100mV by the time we hit test 4. Within spec, but again not what we're used to seeing with an ATX power supply. Again, though, we're talking about a much smaller package that doesn't have the same amount of room for filtering stages like a full size ATX power supply does.

Now it's time for the EA11203A's big brother to jump onto the load tester. Let's test the EA11803A-120.

EDAC EA11803A-120 12V power brick

Test #

+12V

DC Watts/
AC Watts

Eff.

Power
Factor

Simulated system load tests

Test
1

2A

23.9W/
29.7W

80%

.87

11.98V

Test
2

4A

47.7W/
55.8W

85%

.95

11.93V

Test
3
6A
71.2W/
82.4W
86%
.97
11.88V
Test
4
8A
94.6W/
109.5W
86%
.98
11.83V
Test
5
10A
117.8W/
136.8W
86%
.98
11.78V

Although we're asking more power from this unit, the regulation is actually much better as it only dropped 1.6%. We also see here that this power supply is a bit more efficient than the 102W unit. For whatever reason, the power factor is a little lower on this unit, never once hitting .99.

Now let's have a look at the ripple:

Oscilloscope Measurements for EDAC EA11803A-120

 

Test 1

Test 2

Test 3

Test 4

Test 5

+12V





The ripple suppression is substantially better here. There is less ripple and noise. Even at the highest load, the ripple is only 50mV.

Now, let's fire up the FSP 19V power supply. Even though this PSU is higher wattage than the last one, we have to lower the current on our loads a little because the higher +19V voltages are going to result in higher wattages (V * A = W).

FSP120-AAB 19V power brick

Test #

+19V

DC Watts/
AC Watts

Eff.

Power
Factor

Simulated system load tests

Test
1

1A

18.9W/
23.34W

81%

.95

18.93V

Test
2

2A

37.8W/
43.4W

87%

.98

18.92V

Test
3
4A
75.4W/
85W
89%
.99
18.87V
Test
4
6A
112.8W/
128W
88%
.99
18.80V

This is a HUGE improvement over either of the EDAC unit. Voltage regulation is much better holding at .06%! Efficiency is also much better. Now let's see how it does with the ripple:

Oscilloscope Measurements for FSP120-AAB

 

Test 1

Test 2

Test 3

Test 4

+12V




The Ripple here looks very similar to that of the 102W EDAC's, if only slightly better. Test 1 is about 30mV, test 2 is about 40mV, test 3 is about 60mV and, finally, test 4 is 90mV. Still not as good as the 120W EDAC.

Now let's plug the DC to DC power supplies into our power bricks and see what happens....



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