Hi,
I am trying to debug a LM5118-based power supply:
In most cases, it works perfectly fine. However, it does not reliably start, if the output voltage is not zero.
For example, imagine that the power supply is turned off at time 0. Ten seconds later, the output voltage has decayed from 12V to 3V. The unit is sturned back on and one of two things happen:
- Not much happens. The output voltage stays at approximately 3V.
- The output voltage slowly creeps upward, and a couple of seconds later suddenly jumps to 12V.
The exact behavior seems to be dependent on the particular unit being tested. In most cases the output voltage "problem range" is 2-3.5V. Either less or more than that, and the power supply starts fine. But, I have seen several units that won't start until the output voltage is 0.5V or less.
Any ideas/suggestions?
Thanks!
Bart