Stacked output on MPX2002

Applications
1

Hello, I am using the MPX2002 to design a flyback converter with dual outputs and plan to use stacked outputs to improve cross-regulation. The first output is 12V, and the second output is 5V, with the 12V stacked on top of the 5V.

The input voltage range is 100Vac to 240Vac, and the output specifications are 5V/6A and 12V/3.75A. The transformer turns ratio is PRI: SEC1: SEC2: AUX = 39: 3: 2: 5. The 5V output is used for primary feedback control.
Below is a simulated circuit diagram.

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I have conducted practical circuit testing. The results show that at 5V/0A and 12V/0A, the 12V output keeps increasing while the 5V remains regulated. Adding a dummy load of 0.2A to the 12V output causes both outputs to malfunction.
I am unsure if this is correct and would like to know if the MPX2002 is suitable for dual stacked outputs.

Thank you!

3

Hi,

Can you give the 5V output some minimum load? You can see whether it helps.

Sincerely,
Fox

4

Hi, Fox. I’m glad you responded to this post.

I have tried adding small loads to both the 5V and 12V outputs, but it still enters protection mode.
Do you have any other suggestions?"

Thank you!