UCC256403: Problems with burst mode

Ralf Hoffmann

Part Number: UCC256403

With different dimensioning I either get no burst functions at low load and high input voltage or the power supply does not start up but remains in ‘continuous burst mode’.

Is it possible to have your circuit diagram and the associated Excel tool discretely checked here (without publication) ?

5 months ago

0 Mike O' 5 months ago

TI__Guru* 75505 points

Hello,

Your inquiry has been received and is under review.

Regards,

0 Mike O' 5 months ago in reply to Mike O'

TI__Guru* 75505 points

Hello,

The following link will bring you to an excel design tool that can be used to review your schematic and setup the burst mode for the UCC256403 controller.

https://www.ti.com/tool/download/SLUC675

The following link will bring you to an application note that discusses the most common questions and answers with the UCC256403 LLC controller. The information in this application note also should help in resolving your burst mode issues.

https://www.ti.com/lit/pdf/sluaal2

Regards,

0 Ralf Hoffmann 5 months ago in reply to Mike O'

Prodigy 40 points

Hi Mike,
I know these applications.
My problem is that I think I have filled in the design tool correctly, but the burst mode is not activated, although the signal at the FB pin has fallen below the corresponding threshold and continues to fall.
This causes the output voltage to rise to unacceptable levels.

In the lower voltage range, the power supply works very well from no load to overload.
Only at higher voltages do I need a minimum load to prevent overvoltages at the output.

It would be nice if someone could check my completed Excel file and point out any errors in my thinking.

0 Mike O' 5 months ago in reply to Ralf Hoffmann

TI__Guru* 75505 points

Hello,

Your inquiry has been received and is under review.

Regards,

0 Mike O' 5 months ago in reply to Mike O'

TI__Guru* 75505 points

Hello,

If your burst mode is not engaging most likely your BMTL/BMTH is 0.4 disable burst mode.

I would rest the resistor divider on the BW pin so this does not occur.

Regards,

Power management

Power management forum

UCC256403: Problems with burst mode