EP-91 12 V, 1 A, Universal Input Supply
7-Feb-2006
17 OVP Operation Verification
While the EP-91 is in normal operation, monitor the output with a storage oscilloscope.
To cause an overvoltage condition to occur, short circuit the optocoupler LED (as shown
below) to open the feedback control loop. The oscilloscope will capture the output
voltage rising until the increasing voltage across VR2 causes it to conduct, and the
TNY278 device latches off. To reset the OVP latch, the AC input power must be
removed long enough to allow the input bulk capacitors to fully discharge.
Short these points to
test OVP functionality
Figure 33 – Point on PCB to Apply Short Circuit to Trigger OV Shutdown.
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