Part Number: UCC29950
Dear Service Team from TI,
I have been dealing with the above mentioned IC UCC29950 for some weeks now. My basic application is 185-230VAC input and 260VADC output with a power up to 500W. At the moment I have the problem that I cannot control GD1 and GD2 in any way, as soon as I connect these pins to the pulse transformer 78602/9C or to the driver IC UCC27714. I have taken both possibilities from the reference description and from application instructions. It is therefore not a self-invented design.
Meanwhile I have passively adjusted the feedback pin regulation by setting a fixed voltage value of 1.5V (by means of a voltage divider on the primary side), so that I just want to have a fixed switching frequency. Furthermore I proceeded by removing (C4022, C4012, R4011, R4019 --> see wiring diagram), so that I have no energy transfer.
The effect of the circuit is as follows:
As soon as I disconnect GD1 and GD2 from the output stage, the PFC stage is active and GD1 and GD2 are generated with a fixed frequency. Once the power stage is connected, UCC29950 is directly inactive. It doesn't matter if the transformer T4001 and C4022+C4012 are connected or not.
First I assumed an overload of the drivers. This case has not been confirmed. I also checked the active components.
Here they have the two necessary files, which I send them. If you have any questions, please do not hesitate to contact me.
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