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luca72c  
#1 Posted : Monday, January 5, 2015 5:41:47 PM(UTC)
luca72c

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Italy

Hello,
i am arguing why 9V power transformers are suggested to feed Placid HD power supply for Buffalo III boards.
Wouldn't it be better to use a lower voltage transformer, like a 7V one? Placid HD regulator would get 7V x 1,4 = 9,8V rectified current, that should be enough for outputting 5,25V... am i wrong? A 6V transformer should be enough too...
By increasing transformer voltage we have more power to dissipate, causing the heat to increase too.
There is a specific reason to use 9V transformers instead of 7V or lower?
Russ White  
#2 Posted : Tuesday, January 6, 2015 12:44:40 AM(UTC)
Russ White

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Technically all of those should work OK, the little bit extra headroom for regulator does help a bit in terms of performance at the cost of a somewhat less efficiency. :) Still anything from 6-9V or so would be fine.
luca72c  
#3 Posted : Tuesday, January 6, 2015 1:22:04 AM(UTC)
luca72c

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Thank you for your answer.
You mean using 9V instead of 7V would make regulator output more stable? Or less subject to ripple/noise?
I can stand the less efficiency if performance would be better..
Russ White  
#4 Posted : Tuesday, January 6, 2015 2:33:46 AM(UTC)
Russ White

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Yes - you will get slightly better regulation with 9V instead of 7V just because the CCS will have a bit more headroom. This difference is not at all huge - but still there is no advantage to the smaller voltage. :)
luca72c  
#5 Posted : Tuesday, January 6, 2015 9:51:37 AM(UTC)
luca72c

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Italy

You're right, i forgot Placid HD is a shunt power supply.
Thank you again and Happy New Year!
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