12/15/2009 - 2 - www.onsemi.com
AC Source
Vadj
Iadj
AC out
115 Vac
WATTS
DVM
+
-
volts
DVM
+
-
amps
+
-
AC in
DC out
Board Under Test
(Required if not
in AC source)
+
-
Adj
Electronic
Load
O'scope
Test Procedure:
1. Connect UUT (Unit Under Test) to the test setup. Switch the electronic load on, set to
constant resistance mode and the load adjust to high resistance/zero load; switch all of the
digital meters on (assuming they are wired properly for voltage and current sensing); turn
the oscilloscope on with sensing in AC mode and 200 mV per division vertical and a
sweep rate of 5 mS per division. Connect the scope probe to the demo board’s output
terminals.
2. With the AC source OFF, set the current limit on the AC source to 500 mA and the
output voltage to 115 Vac.
3. Turn on the AC source. At no load, the power supply demo board output voltage should
be between 54 and 58 volts on the DVM.
4. Adjust the electronic load from no load slowly up until the output voltage reduces to
between 36.5 and 37.5 volts. The output current should be within the range of 332 to 368
mA. Record the measured load current for future reference. Input power should be less
than 16.8 watts. Figure 1 shows a typical voltage/current regulation curve for this driver
operating at 115 Vac input. The output ripple on the oscilloscope should be less than 1.5
V peak-to-peak including spikes.
5. Increase the load slowly and the current should remain constant within +/- 5 mA of the
recorded value as voltage reduces with increased load (constant current output
characteristic.) The current should remain within +/-5 mA of the value measured in step
4 above from 50 volts down to about 11 volts output. Adjust the electronic load back to
36.5 to 37.5 volts.
6. Reduce the AC input to 90 Vac and verify current is within +/- 5 mA of the value
recorded in step 4 above.
