High Ripple Voltage Problem 36W 18V 2A
Hi everyone,
My design 18V 2A output using TOP246YN. design working well. but output ripple is too high.
Under 2A Load output ripple is 2V and no load condition 600mV.
Transformer :E25
Frequency: 132Khz
Primary Inductance : 245uH
Primary turns 18+18 (sandwich)
Sec Turns: 6
Bias turns:5
5T primary shield and flux band applied
Feedback with TL431
also I tried different Transformer turns ratio 72T primary and different primary incductances eg. 500uH, 800uh, 1.5mh to 3.5mH.
Unfortunately I couldn't reduce the output ripple. What should I do diffrent from above.
Best regards,
Ali AYKAN
Comments
Dear Spock,
Thank you very much your interest. I attached the files you requested.
My previous tests was DC coupled. May be this is wrong test method.
I sent both AC and DC coupled wave forms.
Best regards,
Ali AYKAN
You can try to reduce the gain by increasing resistor R9.
The design is probably unstable... cant tell for sure because you have a large time base... Can you perhaps capture the AC coupled ripple to show only 4 switching cycles (at around 5 or 10 us per division)
There are a few more things we can try... but try this first.
I tried for R9 1.3K 1.5K 1.8K and 2K. It didn't effect the ripple.
5us waveform is attached.
Can you try the following to see if the ripple goes down1) Change C12 with a 1 uF capacitor. This will slow down the loop considerably and add phase margin.2) Change C9 to 10 uF (general purpose electrolytic cap is ok)3) Repeat this with L2 shorted ( I want to remove the post filter and make sure that it is not introducing the problem. Do you see such a high ripple at all loads and at all line conditions? Or tis there a specific load line combination that this pops up?
2 V ripple seems very high.
I'd like to see a few things before I can pass judgement or offer improvements.
1) Pls send me a complete schematic of the design
2) A PI Expert or PIXls design file
3) Output Voltage ripplr waveform (AC coupled)