Power Supply Design Question

rjon17469 · 29th December 2004, 07:17 PM

I have a question regarding the use of caps in a power supply:

I understand that caps are used in the power supply for both filtering and smoothing AC to DC. However, do the caps have to be connected from the rail to ground, or can they just be connected to both rails?

See attachment for schematics.

Thanks in advance!

Reece

Tensop · 29th December 2004, 07:30 PM

if you connect rail to rail you will need a capacitor with twice the voltage rating

rjon17469 · 29th December 2004, 07:35 PM

Quote:

Originally posted by Tensop
if you connect rail to rail you will need a capacitor with twice the voltage rating

Beyond that, it would work? To get similar results, would I also need double the capacitance?

Reece

ingvar ahlberg · 29th December 2004, 08:16 PM

No it will not work very good. The caps are filters, reservoirs and stabilizers to make the supply as stiff as possible. With the caps "floating" in respect to system ground the rails will start to fluctuate and it will affect signal and propably something will be destroyed.

rjon17469 · 29th December 2004, 08:21 PM

Quote:

Originally posted by ingvar ahlberg
No it will not work very good. The caps are filters, reservoirs and stabilizers to make the supply as stiff as possible. With the caps "floating" in respect to system ground the rails will start to fluctuate and it will affect signal and propably something will be destroyed.

Got it. Thanks!

IanAS · 29th December 2004, 08:25 PM

Quote:

Originally posted by rjon17469
do the caps have to be connected from the rail to ground

Normally the ground IS the joint between the main res caps. Coupled to the centre tap of the Tx. of course.

In Dual Rail applications anyway.

jacco vermeulen · 29th December 2004, 09:08 PM

Quote:

Originally posted by ingvar ahlberg
No it will not work very good

http://www.passlabs.com/np/MPA_PS_D0.pdf

byteboy · 29th December 2004, 09:46 PM

See:

cap discussion

Quote:

http://www.passlabs.com/np/MPA_PS_D0.pdf

Good to know someone has some same idea like me.........

Not tried it yet though, would like to know if this realy works..........

darkfenriz · 30th December 2004, 12:10 AM

I think it is OK to use only rail-to-rail caps in BRIDGE amp, isn't it?
otherwise I wouldn't use it

rjon17469 · 30th December 2004, 01:28 AM

I'm not going to put the caps rail to rail.

Thanks for all your help. I was curious for the power supply design I was making.

Reece

29th December 2004, 08:16 PM	#4
ingvar ahlberg diyAudio Member Join Date: Feb 2004 Location: Kungsbacka on the Swedish westcoast	No it will not work very good. The caps are filters, reservoirs and stabilizers to make the supply as stiff as possible. With the caps "floating" in respect to system ground the rails will start to fluctuate and it will affect signal and propably something will be destroyed. __________________ Ingvar

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29th December 2004, 07:30 PM	#2
Tensop diyAudio Member Join Date: Jul 2003 Location: Chapel St.	if you connect rail to rail you will need a capacitor with twice the voltage rating

30th December 2004, 12:10 AM	#9
darkfenriz diyAudio Member Join Date: Jun 2004 Location: Warsaw	I think it is OK to use only rail-to-rail caps in BRIDGE amp, isn't it? otherwise I wouldn't use it

30th December 2004, 01:28 AM	#10
rjon17469 diyAudio Member Join Date: Aug 2004 Location: IL	I'm not going to put the caps rail to rail. Thanks for all your help. I was curious for the power supply design I was making. Reece

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