DPA family, high output voltage ripple (>200mV)
Hello! I constructed a scheme based on DPA42*. So there are 5 power units on yhe board, 4 are for 15V each, and the last one has 8V 1A and 15V 0.1A outputs. Linear regulators (78L05 and 78L12) are used after all components. There is approximately the same situation with output ripple ( 200-300 mV). I tested units separately and found they don't influence on each other.
I designed it with PI EXPERT and implemented components the programm recomended. I tried a lot but couldn'd fix it. What else can I do?
Comments
I ordered new low ESR capacitors but they don't help at all to improve situation. Any ideas,please?
Hi,
High ripple can often be a result of improper measurement technique or measurement setup.
One way to minimize error being introduced by the measurement setup is to use the technique described in the report DER120. Please use the link below to access the report. Please see page.19 of the report.
http://www.powerint.com/sites/default/files/PDFFiles/der120.pdf
Regards
PI-Sarek
I tried
1)RC filters in parallel with output diodes, ( R=22 Ohm - 1K, C=220nF -0,1uF)
2)LC after filters (L=2uH - 400uH, C=22uF)
3)LArger capacitors after output diodes ( up to 1000uF)
4) phase boost in feedback (RC-chain)
5) larger resistor in serial with optocoupler
In helped but just a little-little bit/ Noise is still about 200-250mV in both directions, so it's value is about 400-450mV