powersupply design question

casiomax · 22nd May 2008, 04:18 AM

will this design work?

sneih · 22nd May 2008, 04:41 AM

i think it's great idea..... but still waiting the answer from others

danielwritesbac · 22nd May 2008, 06:27 AM

Since that's a dual secondaries transformer, why don't you use dual rectifiers? See photo.

Hey, the big caps can be nice, but you might want to add a pair of 2200uF or 3300uF. Those charge/discharge fast. Refer to CarlosFM 2004 design.

Oh yes, here's a dual rectifier photo.

Mooly · 22nd May 2008, 06:57 AM

Hi,
Depends what you mean by work. It will give -/+25 volts DC. Is that what you want ? You need diodes with a high surge current rating for big caps like those and with at least a 100 volt P.I.V. rating.
Regards Karl

glennb · 22nd May 2008, 08:02 AM

Make sure the phasing of the transformers is correct otherwise it will just be a paralleled half wave rectifier. ie. the ripple frequency will be the mains frequency rather than double the mains frequency.

You have taken one step towards improving the basic PS design. The 10nF across the diodes cuts out most of the switching noise. The next step is adding some film caps across the main reservoir caps, anything from 0.1uF to 10uF is typical. There are many more steps beyond...

AndrewT · 22nd May 2008, 08:39 AM

use a light bulb for the first power up.
and again every time you modify the project.

casiomax · 22nd May 2008, 10:11 AM

Yes, my target was to get +/- 25volts powering up my split supply amp. But is there any difference between single supply and split supply amp?

I build a chip amp TDA2005 with a single supply, would it make any difference with a split supply design?

ok, now this bridge diode, i believe any 5amp rating bridge should suffice, would it? as for the filter caps, usually 2200uF 50v would be ok.

casiomax · 22nd May 2008, 10:11 AM

as suggested, i've revised the schematics:

AndrewT · 22nd May 2008, 10:14 AM

Diode ratings?
use dual 35A installed inside a bridge rectifier. i.e. two each way.

AndrewT · 22nd May 2008, 10:17 AM

+-25V and 2200uF smoothing does not sound right for an 8ohm speaker.

The peak current into a resistive load is [Vpsu-Vloss]/Rload~=[25-4]/8=2.6amps peak.
Into a reactive speaker load the peak current can be two to three times this value i.e. approaching 7Apk.
The ripple on 2200uF will be enormous.

22nd May 2008, 04:18 AM	#1
casiomax diyAudio Member Join Date: May 2008	powersupply design question will this design work?

22nd May 2008, 08:02 AM	#5
glennb diyAudio Member Join Date: May 2004 Location: Melbourne	Make sure the phasing of the transformers is correct otherwise it will just be a paralleled half wave rectifier. ie. the ripple frequency will be the mains frequency rather than double the mains frequency. You have taken one step towards improving the basic PS design. The 10nF across the diodes cuts out most of the switching noise. The next step is adding some film caps across the main reservoir caps, anything from 0.1uF to 10uF is typical. There are many more steps beyond... __________________ Glenn.

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22nd May 2008, 04:41 AM	#2
sneih diyAudio Member Join Date: May 2008	i think it's great idea..... but still waiting the answer from others

22nd May 2008, 06:57 AM	#4
Mooly diyAudio Moderator Join Date: Sep 2007	Hi, Depends what you mean by work. It will give -/+25 volts DC. Is that what you want ? You need diodes with a high surge current rating for big caps like those and with at least a 100 volt P.I.V. rating. Regards Karl

22nd May 2008, 08:39 AM	#6
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	use a light bulb for the first power up. and again every time you modify the project.

22nd May 2008, 10:11 AM	#7
casiomax diyAudio Member Join Date: May 2008	Yes, my target was to get +/- 25volts powering up my split supply amp. But is there any difference between single supply and split supply amp? I build a chip amp TDA2005 with a single supply, would it make any difference with a split supply design? ok, now this bridge diode, i believe any 5amp rating bridge should suffice, would it? as for the filter caps, usually 2200uF 50v would be ok.

22nd May 2008, 10:14 AM	#9
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Diode ratings? use dual 35A installed inside a bridge rectifier. i.e. two each way.

22nd May 2008, 10:17 AM	#10
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	+-25V and 2200uF smoothing does not sound right for an 8ohm speaker. The peak current into a resistive load is [Vpsu-Vloss]/Rload~=[25-4]/8=2.6amps peak. Into a reactive speaker load the peak current can be two to three times this value i.e. approaching 7Apk. The ripple on 2200uF will be enormous.