Power management

Power management forum

State TI Thinks Resolved
Locked Locked
Replies 5 replies
Answers 1 answer
Subscribers 63 subscribers
Views 563 views
Users 0 members are here

Support feedback

Options

Options

Related

LM51561: Soft start configuration

Oba

Genius 17895 points

Part Number: LM51561

Hello,

My customer has a question for LM51561 datasheet.
In the latest datasheet(SNVSBI6), there are equation (3) and (4).
It says that (3) is for boost topology and (4) is for SPEIC topology.

Which one should be used for flyback topology?

Regards,
Oba

over 2 years ago

0 Bryan Radix over 2 years ago

TI__Expert 3490 points

Hi Oba,

Thanks for reaching out. I would advise you to take a look at the LM5156 Quickstart Calculator Tool, it can be very helpful in the design of the customer's circuit.
Would your customer be implementing primary side regulation (PSR) or secondary side regulation (SSR)?

Thank you and best regards,
Bryan

0 Oba over 2 years ago in reply to Bryan Radix

TI__Genius 17895 points

Hello Bryan,

They want to use SSR architecture.
SNVC240 looks like using CCM. But they want to use it with DCM.
So they doesn't use SNVC240.

Regards,
Oba

0 Bryan Radix over 2 years ago in reply to Oba

TI__Expert 3490 points

Hi Oba,

Thanks for the feedback. If you'd be interested in another tool, I could point you to the Flyback Calculator.
It supports DCM as well as secondary side regulation with isolated optocoupler compensation.

Thank you and best regards,
Bryan

0 Oba over 2 years ago in reply to Bryan Radix

TI__Genius 17895 points

Hello Bryan,

Sorry for my late response.
The Flyback Calculator you mentioned deosn't answer for Tss calculation.
Could you tell me how to calcutlate Tss for flyback DCM?

Regards,
Oba

0 Stefan Schauer over 2 years ago in reply to Oba

TI__Guru 65091 points

Hi Oba,

there is an application report discussing softstart for flyback:

https://www.ti.com/lit/pdf/snvaa44

Note: CCM or DCM does not have an (significant ) impact on the softstart time.

Best regards,

Stefan