Posted on February 20, 2015 at 01:33 We are using VIPER17 in our products as a standby power supply for a couple of years in mass production. Recently we faced a problem that if the mains is off and on again this power supply can not start-up. Mains has to be off for a long time (more than hour) for this power supply to be able to start-up. The problem is not related to the heat, input voltage or load conditions. Replacing IC with another from old stock fixed this problem. Increasing the value of C
DD
(
to pin 5)
also fixed this problem. Our tests show:
-
after mains was OFF for a long time (>2Hr), discharge current I
DDch
was 2.4mA and unit started successfully .
-
if Mains was OFF for short time (but bulk capacitor is still charged) , discharge current I
DDch
was 3.43mA
and unit could not start.
-
if Mains was OFF a bit longer time (bulk capacitor was fully discharged) , discharge current I
DDch
was 2.95mA and unit could not start.
Any suggestions why the value of
I
DDch
is changing?
