Flyback Active Clamp Circuit

user1586218

Part Number: UCC2893

To create an active clamp circuit of a flyback type power supply circuit by using a UCC 2893.
I calculate with PSPICE, but the operation waveform is unstable and does not converge.
It is considered that the cause is the constant of the resistance and the constant of the capacitor in the part surrounded by the blue dotted line around the UCC 2893.

Do you know anything?

over 3 years ago

0 Hong Huang over 3 years ago

TI__Guru 58665 points

Hi,

Do you mean your simulation circuit not stable? why do you think the unstable due to the constant of R or C in that blocked area?

0 user1586218 over 3 years ago

Prodigy 200 points

Thank you!

First, what I call instability is the circled part of the waveform.
The circled part shows that the main switch FET is turned off, then turned on immediately after a short interval, and then turned off again.
This condition with frequent short turn-on is called unstable.
Changing the resistor and capacitor constants slightly improved this unstable behavior, but nothing better.
I don't know exactly how to set the resistor and capacitor, so could you point out where the problem is?

0 Hong Huang over 3 years ago in reply to user1586218

TI__Guru 58665 points

Hi,

I am not sure your reason is valid or not as I cannot read your circuit. Can you re-send your circuit with better resolution? Also, can you provide your simulation circuit so I can open it in PSpice to see if any clue why FET on/off?