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Old 26th September 2011, 10:07 AM   #1
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Default LM4780 Power Supply

Hello all,

I'm collecting all the parts for a new chip amplifier; I decided on two LM4780 parallel boards.
I already ordered the two boards (ebay), the two LM4780 chips, I already have two massive heatsinks and I'm working on the aluminum chassis.
While waiting for the ordered parts, I'm trying to define the power supply.
This project should be a "low cost" one, and I'd like to re-use what I have on hands; for this reason I'd like to use, as the power source, a transformer I already have, a 230V/18V 300W toroid.
The transformer, however, has only a secondary winding, so the only way I can use it is doubling the oupout using a voltage doubler, as shown below:

PS Schematic

I will use two (or more) schottky diodes, and about 50mF of capacitor per rail.
The PS will power two LM4780, paralleled two by two.
Will it work?
Do you see any problem, will the PS output voltage good enough for two amplifiers?
Did anybody here used this schematic in the past?
Please let me know your thought.

Ciao, Giovanni
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Old 26th September 2011, 01:50 PM   #2
AndrewT is offline AndrewT  Scotland
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I would suggest adding a big inductor into the hot lead between C1 & C3 and similarly between C9 & C11.

These two inductors could cost as much as the correct transformer.
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