Power amp - Voltage doubler supply - Why not used?

knutn · 13th March 2011, 07:09 PM

For power amplifiers it is quite common practice to use a separate high current supply for the output current buffer and a separate high voltage supply for the input and VAS stages. Some uses a separate transformer for the latter. An alternative, however, is to use a voltage doubler.

The attachment shows my planned full wave voltage doubler. But I have not seen it used. What do you think? Am I missing a point somehow, since the solution is not used, or is it?

Andrew Eckhardt · 13th March 2011, 07:21 PM

All the extra capactiors, no need for that much extra voltage, and the regulation/isolation of the high voltage supplies is still limited by the output loading of the high current supply.

knutn · 13th March 2011, 07:48 PM

I would think it is a good practice to have a regulated voltage for the input and VAS stage. When using MOSFET's, then a 10 V (min) extra voltage is needed above the output buffer supply. I would think a couple of extra capacitors would be a reasonable price?

Andrew Eckhardt · 13th March 2011, 07:54 PM

It could work out OK for the voltages posted and with regulators, but you can see that by the time you get to 50 volt power rails, 100 volt driver supply is just pretty much out of hand. So for higher power amps you probably wont see it.

knutn · 13th March 2011, 08:13 PM

Quote:

Originally Posted by Andrew Eckhardt

It could work out OK for the voltages posted and with regulators, but you can see that by the time you get to 50 volt power rails, 100 volt driver supply is just pretty much out of hand. So for higher power amps you probably wont see it.

I agree on that, but I thought most designers used regulated supply for the voltage stages.

darkfenriz · 13th March 2011, 08:23 PM

I used one, when I built an amp with a fellow Norwegian guy.
I works fine, but the one I built was a lot simpler: a hint: use +-24V as a reference for boost bridges, save some capacitors at the expense of 50Hz ripple.

Elvee · 13th March 2011, 08:58 PM

Anyway, real men design circuits (including amplifiers) to operate on single, non regulated rails.

Multiple supplies are an expedient for the weak and feeble-minded.

darkfenriz · 14th March 2011, 12:15 PM

I have my own suspicions about guys who like to emphasise what 'real men' do or do not.

13th March 2011, 07:48 PM	#3
knutn diyAudio Member Join Date: Mar 2006 Location: Oslo	Regulated supply for the voltage amplifier? I would think it is a good practice to have a regulated voltage for the input and VAS stage. When using MOSFET's, then a 10 V (min) extra voltage is needed above the output buffer supply. I would think a couple of extra capacitors would be a reasonable price?

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13th March 2011, 07:21 PM	#2
Andrew Eckhardt diyAudio Member Join Date: Nov 2005 Location: PA	All the extra capactiors, no need for that much extra voltage, and the regulation/isolation of the high voltage supplies is still limited by the output loading of the high current supply.

13th March 2011, 07:54 PM	#4
Andrew Eckhardt diyAudio Member Join Date: Nov 2005 Location: PA	It could work out OK for the voltages posted and with regulators, but you can see that by the time you get to 50 volt power rails, 100 volt driver supply is just pretty much out of hand. So for higher power amps you probably wont see it.

13th March 2011, 08:23 PM	#6
darkfenriz diyAudio Member Join Date: Jun 2004 Location: Warsaw	I used one, when I built an amp with a fellow Norwegian guy. I works fine, but the one I built was a lot simpler: a hint: use +-24V as a reference for boost bridges, save some capacitors at the expense of 50Hz ripple.

13th March 2011, 08:58 PM	#7
Elvee diyAudio Member Join Date: Sep 2006	Anyway, real men design circuits (including amplifiers) to operate on single, non regulated rails. Multiple supplies are an expedient for the weak and feeble-minded.

14th March 2011, 12:15 PM	#8
darkfenriz diyAudio Member Join Date: Jun 2004 Location: Warsaw	I have my own suspicions about guys who like to emphasise what 'real men' do or do not.

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