output over voltage at turn-on
We have a TOP244R design from a vendor.
The output is 15V but at turn-on, often times, it will go all the way up to 18V & stay flat for several hundred usec. Then is slews down to 15v. Sometimes it will just be peaking to 18 V or so & then exponentially decay to 15v.
It is the flat 18V that seems intriguing. Our OV detection shuts down the system on power up when this happens.
Anyone seen this & found a fix or reason?
-bougnoul
Comments
sounds intriguing!
soft finish !
will try.
thnx
-bougnoul
Can't believe I am evoking this same topic again after almost 2.5 years!
In some of the units out there in systems, we have been told the 15V module using TOP242 will drift up after several hrs of operation( ambient temp is high...65deg C +). As it sits just below our "upper threshold" limit, it will finally go above that. The the supervisory ckt kicks in & shuts the whole system down gradually.
This has been a nuisance in the system all these years.
Some "wise fat cat" had analyzed & expressed a deep statement that " the feedback pin is not sourced with enough current from the high resistive value in the opto circuit".
Well, we use much lower value than the model gives us due to other design considerations.
Any idea why this is happening?
We have in place the fix mentioned earlier in this post.
very much appreciate a feedback.
-b
You need a "soft-finish" circuit. Virtually all our designs use one.
Assuming you have a TL431 in your feedback, place a small 10 uF / 16V electrolytic right across Cathode to Anode.