PA100 power supply..

[deepanger]

trying to make some experiments with the lm3886 IC for the 1st
time, and ofcourse the main prob. is to build a PS.
iwanna build a liner one (use in home) but till now i cant decide
what parts i need and with which specs. (trans. ,bridge rec...etc)
so anyone can help??!

ill build it to drive that schematic in the national lm3886 bridging
notes pdf, called PA100 (100watt into 4ohm), with +-28V. ps.

whats the specs. of the transformer? and can i use a normal
one instead of a toroidal?, and so on for the bridge rectifier
and caps...etc

thanks alot.

 

[deepanger]

anyone?

 

[crown300]

If you look at the LM3886 datasheet, on page 16 you will notice two formulas for the power transformer - equation (5) and (6). I plugged the info into my trusty HP caculator and it shows that for 100W and 4 ohms you need 28.3 volts and 7.1 amps.
Power = V*I = 28.3*7.1= 201 Watts.
I believe that for a bridged configuration you need twice that = 400 Watts.
For the price, use one of the universal 25 amp bridge rectifiers (the ones in a 25 mm square).

If the chip gets warm with no signal input it may be oscillating.

How hard is it to get electronic parts in Egypt? Can you mail order from europe(?) or any local parts stores?

 

[deepanger]

If you look at the LM3886 datasheet, on page 16 you will notice two formulas for the power transformer - equation (5) and (6). I plugged the info into my trusty HP caculator and it shows that for 100W and 4 ohms you need 28.3 volts and 7.1 amps.
Power = V*I = 28.3*7.1= 201 Watts.
I believe that for a bridged configuration you need twice that = 400 Watts.
For the price, use one of the universal 25 amp bridge rectifiers (the ones in a 25 mm square).

If the chip gets warm with no signal input it may be oscillating.

How hard is it to get electronic parts in Egypt? Can you mail order from europe(?) or any local parts stores?

doesnt the trans. is rated in VA ?!
i mean shouldnt the Power Factor be considered in this calculations?
all ive reached that to get +-28V. ive to use a 20-0-20 trans. with
min. about 200VA and if i take a PF. of 0.8 :

Imax= 200/40*0.8 = 6.25A.
right?? or am writing a mess!?

about elec. parts here in egypt ,, itsnt that hard to find the very
common parts.. but if trying to search for high quality or abit
unfamiliar ICs i think u gonna suffer,, ilive in alexandria (2nd city)
i gonna search 1st in cairo (the capital) and its no way in here
i think i ll try to search for something online..

dont u know any good sites to buy from?
thanks..

 

[crown300]

Power is measured in "Watts" which is caculated by multiplying Volts times Amps (V*I).
I have never used Power Factor in my transformer calcs and I don't think that it is mentioned it in the Zen data.

So far I have gotten my parts from DigiKey - except the Piltron xfmr from Canada.

 

[deepanger]

Power is measured in "Watts" which is caculated by multiplying Volts times Amps (V*I).
I have never used Power Factor in my transformer calcs and I don't think that it is mentioned it in the Zen data.

So far I have gotten my parts from DigiKey - except the Piltron xfmr from Canada.

and what about the VA unit ,ithink its the most used in the
trans. power rating!, if u checked the ESP pages about the amp.
PS u gonna find that most of the ratings are in VA not in watt..