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Hi all,
I've been tasked to perform what my company calls a tech refresh on a power supply circuit board, essentially this involves addressing minor issues, obsolescence, small tweaks and adjustments based on operational history. This also includes a PCB re-layout.
This circuit board utilizes an LM3481 with a SEPIC topology, I've heard from colleagues who have experience with this board that the SEPIC converter performs terribly.
I'm seeking the help of the experts to identify any glaring design issues. I have a feeling there are fundamental schematic errors that are causing the poor performance (or none at all).
The design Targets:
Input voltage range: 5 - 28 VDC
Output voltage: 12 VDC
Output current: 500 ma
A couple issues I have noticed right away:
1) The two inductors are different values. All the design notes that I have seen use identical values.
2) The Compensation resistor and capacitor are swapped according to the examples shown in the design notes.(R51 and C38) in attachment.
Thanks in advance!!
Garret,
Thank you very much for your response.
C47 is a 150uF, 16V cap, and for whatever reason, is only installed on the 28V PCB variant (SEPIC is supposed to be designed to work with three different input voltages: 5 VDC, 12 VDC, and 28 VDC).
Regarding the performance issues, we have a lot of noise on the output.
Feel free to let me know if you have any other questions
Thanks,
Levi
Can anyone determine a ball park figure of the ACTUAL MAX output current from the SEPIC circuit in the original post?