On 6/8/16 6:19 AM, paul swed wrote:
The units were never intended for a slow ramp
I assume it runs into a meta stable condition
Neither on or off and then corruption
Glad you're can repair them
On Tuesday, June 7, 2016, Bob Camp <[email protected]> wrote:
Interesting, we just had a similar issue on a circuit here at work..
someone slowly brought the supply voltage up on a bunch of DC/DC
converters, and some didn't start. This was in initial checkout of a new
board.
Switch it on with a bang, and it works just fine.
So for some of these things there's apparently a minimum dv/dt.
I've seen this before with DC/DC converters.. if the voltage drops too
low, they draw too much current - because they're basically constant
power devices- and the overcurrent trip shuts them down. There's a
delicate interplay between the overcurrent and undervoltage trips,both
of which have some sort of time constant, and I suspect that for a lot
of circuits, the "slow ramp up of input voltage" isn't something they
are designed for. Once it's up and running, when the supply sags, the
UV trip works just fine, tripping before the OC trip goes.
Linear regulators.. they may be not the most efficient thing in the
world, but they have a lot less "weird" behavior. (although I've had
linear regulators go into thermally driven oscillation)
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