Power supply design - Electronic Circuits Projects Diagrams Free

FusionITR · 10th March 2006, 07:31 AM

I want to incorporate a switching power supply that can supply 5V at around 5A in a project. I know how to make simple linear power supply but I have never designed a switching power supply that can supply high current.

What do I need to know (tutorials?) thats different from regular linear power supplies? Does the transformer current rating have to be equal or more than 5A to make a 5A regulated DC supply? I looked up some high current transformers and they are expensive, but I see switching power supplies on ebay selling for around 20 bucks, so am I missing something about the size of the transformered needed?

General information needed here.

Thanks.

akg · 10th March 2006, 08:00 AM

Quote:

Originally Posted by FusionITR

I want to incorporate a switching power supply that can supply 5V at around 5A in a project. I know how to make simple linear power supply but I have never designed a switching power supply that can supply high current.

What do I need to know (tutorials?) thats different from regular linear power supplies? Does the transformer current rating have to be equal or more than 5A to make a 5A regulated DC supply? I looked up some high current transformers and they are expensive, but I see switching power supplies on ebay selling for around 20 bucks, so am I missing something about the size of the transformered needed?

General information needed here.

Thanks.

There are ICs specificaly manufactured for SMPS appln. it is better to use them if ur not intending to learn from scratch.

aiva · 10th March 2006, 09:32 AM

If you can spend some money you can use prefabricated block. "http://www.aimtec.ca/ame30.html" for example.

There are quite many firms making such devices.

Russlk · 11th March 2006, 01:48 AM

This URL may give you some info: http://www.smps.us/

k7elp60 · 11th March 2006, 02:16 PM

With any power supply watts out = watts assuming 100% efficiency. One of the advantages of a switching power supply is you don't need a transformer to step the line voltage down to the needed voltage. But since you want 5V @ 5A the power out is still 25 watts. If you started with 25 volts the current requirement would be somewhere near 1A. I say somewhere as there is some ineffiency in the power supply. If you start at line voltage of 120V the current in is approximately = P/E or 25/120 or
about 0.2A.
One problem with switching power supplies over linear power supplies is that the switching power supply needs a minimum load. There are ways to overcome this also.
If you want line voltage isolation I would recommend using a higher voltage transformer(higher than normal for a 5V supply) and then a buck regulator. For example if you use a 24V secondary transformer the load current will be a little greater than 1A.

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

10th March 2006, 07:31 AM	(permalink)
FusionITR	Power supply design I want to incorporate a switching power supply that can supply 5V at around 5A in a project. I know how to make simple linear power supply but I have never designed a switching power supply that can supply high current. What do I need to know (tutorials?) thats different from regular linear power supplies? Does the transformer current rating have to be equal or more than 5A to make a 5A regulated DC supply? I looked up some high current transformers and they are expensive, but I see switching power supplies on ebay selling for around 20 bucks, so am I missing something about the size of the transformered needed? General information needed here. Thanks.

10th March 2006, 09:32 AM	(permalink)
aiva	If you can spend some money you can use prefabricated block. "http://www.aimtec.ca/ame30.html" for example. There are quite many firms making such devices.

11th March 2006, 01:48 AM	(permalink)
Russlk	This URL may give you some info: http://www.smps.us/ __________________ see my website: www.geocities.com/russlk

11th March 2006, 02:16 PM	(permalink)
k7elp60	With any power supply watts out = watts assuming 100% efficiency. One of the advantages of a switching power supply is you don't need a transformer to step the line voltage down to the needed voltage. But since you want 5V @ 5A the power out is still 25 watts. If you started with 25 volts the current requirement would be somewhere near 1A. I say somewhere as there is some ineffiency in the power supply. If you start at line voltage of 120V the current in is approximately = P/E or 25/120 or about 0.2A. One problem with switching power supplies over linear power supplies is that the switching power supply needs a minimum load. There are ways to overcome this also. If you want line voltage isolation I would recommend using a higher voltage transformer(higher than normal for a 5V supply) and then a buck regulator. For example if you use a 24V secondary transformer the load current will be a little greater than 1A. __________________ The great thing about electronics is unlimited ways to do the job. The only limit is one\'s imagination. I generally think my way is best. Show me a different way. I have an open mind.