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|5th September 2005, 11:51 AM||#1|
clean psu design attempt
i've build an headphone amplifier (http://headwize.com/projects/showfil...szeke1_prj.htm). It's a class A amp, i'm now shure about the power consuption, but **should** be less than 10W (2 chan).
now, since it is very sensible to the power supply quality, i decided to build myself one to get rid oh the hum
i tried to design it myself, basically it's a transformer+recitifier bridge and filter, followed by an lm317 regulator (as taken from the datasheet), a capacitance multiplier (http://sound.westhost.com/project15.htm) to reduce ripple and a couple of capacitors for energy reserve
the schematic is attached
i'd like to build a nice unit, with a voltmeter panel on the front, and regulate the voltage with a pot (R1, under the lm317), so I can use it for different projects
i'd like to have from +12V to about +20V on the load
now i need help with calculations, here's what i did:
from the datasheets of lm317:
to have high current out (typ 2.2A), Vin-Vout <= 15V
for the lm317 to work, Vin-Vout >= 3V, let's have 4V
so, 4 < Vin-Vout < 15
now i want 12<Vout<20 (i know i loose something on the capacitance multiplier, but i'll survive ...)
4 < Vin - 12 < 15 => 16 < Vin < 27
4 < Vin - 20 < 15 => 24 < Vin < 35
the most restrictive are
*** 24 < Vin < 27 ****
let's have 25V ...
to have this, i need a transformer with 25 / sqrt(2) = 17.67V
=> the transformer should be a 18V
is all this right???
are there any big errors on the schematic?
dc output shouldn't be more than 20V @ 1A, so, considering losses in the psu, how many VA should the transformer be?
i've never designed a psu before, so I just combined different elements and did some math ...
thanks in advance
|5th September 2005, 11:54 AM||#2|
i forgot ...
for the transistor in the capacitance multiplier section, what should I get? the article in sound.westhost.com suggests a darlington ...
what models are easily reperible out there?
|7th September 2005, 07:27 AM||#5|
comunque ho provato con lo spice, e ho visto che ha tempi di carica piuttosto alti ... per adesso vado solo con il regolatore, poi vedr˛
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