Ripple noise in switching PS is too high! Help!

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digitalheart

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I've finished a switching power supply module but it runs so bad! Ripple at output is too high, about 1V-1.5V. ( My output Voltage is 5V) I used Flyback Converter Topology. Major components include:
- Flyback Transformer use core type ERR35L
- Mosfet N channel type 2SK1464
- PWM is UC3845B
- Output diode is CTB-34D

Please help me to show the mistakes i've made!
(You can review my design if you're using Orcad software)

Best Regard!
 

If I were you I would change the format of the file inside the ZIP from file.dsn to something more popular such as jpg, gif, pdf and so on ..
I can't open it ..
Regards,
IanP
 

IanP said:
If I were you I would change the format of the file inside the ZIP from file.dsn to something more popular such as jpg, gif, pdf and so on ..
I can't open it ..
Regards,
IanP
Click to expand...

Sorry! I'll do that. First, I thought like you too. But that diagram is too large so I can't. Now It's OK. I cut the Rectification Block and captured it to .JPG file.

Thank for you care, IanP! Thank you very much!
 

I think you have problem with D303.
You can consider two options: 1st, to connect them in parallel and connect both anodes to (9), (8) and (7) transformer pins for half wave rectification, or 2nd, and I think this will be better option, to use only 2 output windings and connect them in Centre-Tap configuration for full wave rectification ..
Also, what I would do, you have L303 inductor consisting of 2 coils. Try to connect one inductor on the positive rail, and the other on the 0V rail ..
Regards,
IanP
 

Thank you! I'll try to follow your advices! Anyway, Do you think that problem occured because the N-FET is unsuitable, maybe?
 

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