cupoftea
Advanced Member level 5
Hi,
The max duty cycle of this UCC28085 full bridge driver is 49% (translates to 98% "real" duty cycle).
Do you agree, this is absurd?
In no way should you ever operate a Full bridge that could, at any time, go to 98% duty...because it would mean one fet turning on very soon after the other fet turned off....and the ringing in the leakage inductance could mean the on-coming fet turns on whilst the diode of the off-going fet is conducting the leakage ring ....giving a massive reverse recovery current spike...which will eventually lead to power supply failure.
You can get round it by massive snubbing of the primary, but surely adding a duty cycle clamp is the way to go? (unless of course, dare i say, the aim is to make PSU's that fail sooner, then they are re-purchased, quids in!)
Do you agree with this?
UCC28085
The max duty cycle of this UCC28085 full bridge driver is 49% (translates to 98% "real" duty cycle).
Do you agree, this is absurd?
In no way should you ever operate a Full bridge that could, at any time, go to 98% duty...because it would mean one fet turning on very soon after the other fet turned off....and the ringing in the leakage inductance could mean the on-coming fet turns on whilst the diode of the off-going fet is conducting the leakage ring ....giving a massive reverse recovery current spike...which will eventually lead to power supply failure.
You can get round it by massive snubbing of the primary, but surely adding a duty cycle clamp is the way to go? (unless of course, dare i say, the aim is to make PSU's that fail sooner, then they are re-purchased, quids in!)
Do you agree with this?
UCC28085