TL431: Are there any range limit of Cz and Rz value for TL431 stable operation?

Kazuya Nakai59

Guru 21915 points

Part Number: TL431

Hello guys,

One of my customers is designing a flyback power supply using TL431AIDBZ.

They are going to use similar circuit to the attached schematic.

They have the following question at this moment.

Could you please give me your reply for them?

Q. This is a question about TL431 stability not flyback power supply stability.

Also it is about Cz and Rz connected between CATHODE and REF terminal in the attached schematic.

Are there any range limit of Cz and Rz value for TL431 stable operation?

Your reply would be much appreciated.

Best regards,

Kazuya.

7723.Schematic.pdf

over 4 years ago

0 Zarni Tun over 4 years ago

TI__Prodigy 110 points

Hello Kazuya,

The values of these two components depend on the design of the flyback system; hence, the flyback team might be able to provide you with what you are looking for. Please see the links below for a P2P compatible flyback device using TL431 in a similar way and their corresponding values for their design. Hope this helps.

https://www.ti.com/tool/PMP2187

https://www.ti.com/lit/pdf/slur196

Best,

Zarni

0 Kazuya Nakai59 over 4 years ago in reply to Zarni Tun

Guru 21915 points

Hello Zarni,

Thank you very much for your reply.

I understood TI doesn't have any data about the range of Cz and Rz connected between CATHODE and REF terminal for TL431 own stable operation.

Could I ask you a few additional questions as the follows?

Q1. Does TL431 has a model for Pspice for TI?

Q2. If Q1 answer is yes, can the phase margin with Cz and Rz be simulated using the model on Pspice for TI?

Q3. If Q1 answer is no, is there any way to simulate the phase margin with Cz and Rz?

Thank you again and best regards,

Kazuya.

0 Masoud Beheshti61 over 4 years ago in reply to Kazuya Nakai59

TI__Mastermind 18781 points

Please kindly see the simulation models and details here. Thank you.

TL431 data sheet, product information and support | TI.com

0 Kazuya Nakai59 over 4 years ago in reply to Masoud Beheshti61

Guru 21915 points

Hello Masoud and Zarni,

Thank you very much for your supports.

I will check the page for a simulation.

Thank you again and best regards,

Kazuya.

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TL431: Are there any range limit of Cz and Rz value for TL431 stable operation?