LM5155: Schematic review

Gary Zeng

Intellectual 1430 points

Part Number: LM5155
Other Parts Discussed in Thread: TL431

Tool/software:

Hi TI expert,

Could you please help review below schematic?

LM5155 flyback 24V in 5V4A out.pdf

24V input and 5V/4A output

6 months ago

0 Moritz 6 months ago

TI__Mastermind 19015 points

Hi Gary,

Thanks for reaching out.

To do an efficient review it would be helpful if you could provide The datasheet of the used transformer, as well as the filled out quickstart calculator for this device:

https://www.ti.com/tool/download/SNVC240

I am looking forward for your response.

Best regards

Moritz

0 Gary Zeng 6 months ago in reply to Moritz

TI__Intellectual 1430 points

Hi Moritz，

Thanks for your reply.

The transformer is same as LM5155's ti demo board:

LM5155EVM-FLY

0 Moritz 6 months ago in reply to Gary Zeng

TI__Mastermind 19015 points

Hi Gary,

I found the following things:

- 100Ohms for the gate resistor is too high. I recommend to start with 0 ohms and then incrrease if necessary.

- The TL431 should be biased properly. For this you can use a 10 k resistor like shown below:

- You should use an output capacitor at the auxilary winding.

Best regards

Moritz

Power management

Power management forum

LM5155: Schematic review

LM5155EVM-FLY