UCC2803: Flyback AC/DC converter, Tina-Ti

Hi Hong,

What I can do for that?

Thanks and Regards

Abhishek Kumar

Hi,

You need to review the datasheet to check protection setup on each pin, then probe each pin to see which pin shows over its threshold. For example, CS pin.

Hii,

I have reviewed the datasheet, couldn't find any solution. That's why posting here. Please give any sure solution.

Thanks

Hi,

check CS pin waveform.

Hi,

Couldn't find any solution.

Hi,

Besides, your Vcc looks into UVLO off. So check Vcc at the point when VREF turns off.

Hii,

Uploading all pins and output voltage waveform screenshots, also attaching simulation file. I tried to resolve the issues as you suggested but couldn't get the result. If it is possible then run the simulation I am uploading here, then suggest where I am doing wrong.

Thanks

1323.UCC2803.TSC

Hii, 

I had done some mistakes in previous simulation. This is the updated one and got these waveforms. Please consider it final simulation. 

Thanks

Hi,

There are no waveforms or tina model attached to your latest message. I assume you are now ok with your simulation. Otherwise please provide your waveform and tina model. 

Hii,

Uploading the simulation file and waveform screenshot,

Thanks

2072.UCC2803.TSC

Hi,

I have found the issue of your model. VCC hit UVLO off (3.6V) to cause shut down and start up repeatedly. You can measure your simulation result of VCC to confirm. It looks C3 = 15uF is not big enough so cannot provide bias long enough to get AUX to take over. You may try increase C3 from 15uF to bigger such as 30 uF, 50uF, 100uF, 150 uF to find which one can provide long enough time. Also you can reduce R3 from10 to 1 to try to see if AUX can take over quicker and avoid VCC UVLO off.

Hi

Still getting the same error.

Hi,

can you measure the waveform of your aux winding output to check if the aux output too low?

Hi,

please provide the simulation waveform each time with the parameter value change so I can know what else to try.

Hii,

I have checked VCC voltage waveform, it is not going lower than 3.6 V (turn off threshold), and also the aux winding output is not too low. I have already uploaded the simulation file. Please run it on your system so that we can resolve the issue sooner.

Thanks

Hi,

I cannot have time to run simulation for you - that is your work. That is why you need to provide your simulation waveform to show what you claim to me then I can provide my suggestion what to do next.

Hi,

Also, each time when you send to me with your new simulation waveform please also sent to me with your updated model and let me know what you have changed compare to the last time.

Hii,

Changed C3 to 50 uF but still getting the same error. Uploading simulation waveform. Also ran the simulation for C3 values of 30 uF, 100 uF, and 150 uF and getting the same waveform.

I know you don't have enough time to run the simulation but this hit and trial method will take longer to solve the issue.

Thanks

I will take a look. I think you should try to resolve the issue as well. I can only support this way due to my time limitation. I will look at your result to make suggestions.

Thanks, Hong. I am trying but getting no solution and also running out of time.