WEBENCH® Tools/UCC28C43-EP: UCC28C43-EP

Murali Harikrishnan1

Part Number: UCC28C43-EP
Other Parts Discussed in Thread: TL431

Tool/software: WEBENCH® Design Tools

Flyback 33V 2.6A TI.TSC WBDesign 33V Flyback.pdfI have a web bench design for a 75V to 395V DC input and output of 33V@2.6A with opto feedback DCM

I have replicated the design in Tina TI (Free and Cloud)

1. The design does not startup with the opto configured as per web bench design. There could be an opto model issue which i am not sure off.

2. It does startup if the Vref on the opto is dropped as done by R8

3. The output is not regulated with opto feedback.

4. With various design constraints the opto proposed to be used is SFH-617A-2x009T

4. With a direct feed back from output 1 (R4 and R5 ) instead of opto output. The system has an output but not constant. This could be because of the compensation network values not being matched to non isolated design.

The web bench design and TINA simulation attached.

over 6 years ago

0 Murali Harikrishnan1 over 6 years ago

Prodigy 80 points

The above post does not shoe the simulation file so reattaching7127.Flyback 33V 2.6A TI.TSC

0 Praveen Badiger over 6 years ago in reply to Murali Harikrishnan1

TI__Expert 8365 points

Hi Murali,

We have forwarded your query to the concerned team. We will get back to you.

Thanks & Regards,
Praveen

0 Peter Meaney over 6 years ago in reply to Praveen Badiger

TI__Mastermind 31580 points

Hi Murali,

The output voltage is rising in the simulation file, when the output voltage hits about 33.6V the voltage on the TL431 drops but I do not see any change in the current on the transistor side of the opto-coupler.

You need to check that the opto-model is correct by measuring to current on the both side of the part to ensure they match which they should do if the CTR is equal to 1.

I would simplify the circuit firt to ensure the basic circuit is operational. I see that the connection to the primary side error amplifier is taken from the collector side of the opto in the TINA circuit but it should come from the emitter side as shown in the webench schematic.

Regards

Peter

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