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Power Integrations Engineer Power Integrations ModeratorVery low ripple SMPS
I'm quite new to SMPS design, so hopefully somebody experienced will help me here.
I need to design a PSU for audio gear with the following parameters:
V1: +30V, 50ma; ripple 0.5mV
V2: -10V, 250mA; ripple 0.15mV
From what I found on the site, all designs offer ripple not less then several dozen mV. Can you guys direct me to some particular design that will suite my needs and offer low ripple?
Thanks!
2 replies | Created on Sep 3, 2010 11:24 AM by dontsov
dontsov
If you use TL431 feedback Put a series trimpot to the capacitor between feedback loop between the cathode and reference pin of the TL431 and by adjusting this values you can reach what you want or change the resistor series to optocoupler again by trimpot.
Adjust the ripple for the worst case so it will work in other conditions.
kemred | 35 posts Is it acceptable for the design to have 0.5 mV ripple in the range of >10 kHz or so, and say, 50 mV at 120~1000 Hz? If so all you need is a 2-stage output filter and careful layout.
If you need it to have <0.5 mV ripple even at 120 Hz, then a "boosted" ripple filter aka "capacitance multiplier" should work. See attached schematic. It will filter out 100 Hz ~ 500 kHz ripple. If the 120 Hz ripple is still large, increase the capacitor values.
Layout technique is paramount in getting rid of output "spikes" that ring in the multi MHz range. No amount of filtering will clean that up if you have a poor layout.
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| capacitance multiplier.gif | 5.36 千字节 |
PI-Tucker | 290 posts 
