need a small power supply - Electronic Circuits Projects Diagrams Free

escin · 7th August 2004, 08:54 AM

i need a small power supply for my peak charger.i need 12v 7amp power supply.it must be small.help me... A.S.A.P (as soon as possible)

Exo · 7th August 2004, 09:33 AM

what is small for you?

7Amps using a normal mains transformer (and required capacitors for smoothing) is not gooing to be really small...

samcheetah · 7th August 2004, 07:50 PM

7 Amps can never be small!!!!!!!!!! that is if u go for a linear PSU

u r gonna need a BIGGG transformer (probably a toroid one), a BIGGG cap, and a BIGGG heatsink. and maybe u would have connect transistors in parallel to get that much current. and all of them will require a BIGGGG surface area to dissipate heat.

so u see it cant be small. but u could go for a switcher. that might reduce the size somewhat.

ante · 7th August 2004, 11:08 PM

Escin,

If you have an old PC power supply lying around, will that be too big and heavy for you?

Ante :roll:

*railmanxaero* · 8th August 2004, 04:55 AM

An old PC power supply is 7 amps? I didn't know that.
Maybe you can modify the PC power supply by taking the circuit board out of the case and custom making your own new case. It wouldn't that small but it might work.

Sebi · 8th August 2004, 08:02 AM

L4970 can do this...

ante · 8th August 2004, 10:51 AM

Most old ATX supply’s have 8 Amps or more and if you don’t use much current from the 5 Volts line you can get a little bit more than the rating from the 12 Volts line. And it is much lighter than a transformer for 12Volts 8Amps.

Ante :roll:

Sebi · 9th August 2004, 07:22 AM

Yes, the PC PSU also a good solution, i've built a 12A 14.4V accu-charger from PC PSU. But the feedback originally on 5V output, so the 12V out not work properly without heavy 5V load.
After rewiring the feedback to 12V out with additional 10k pot. the output adjustable. Also possible the current limiting.

ante · 9th August 2004, 04:06 PM

Sebi,

I have tested different supplies and been as high as 47 Ohms as a load for the 5 V line but I prefer to use a 10 Ohm 10 Watt resistor that have worked fine so far on 4 or 5 supplies. On some of the later models there are a power good signal required also.

Ante :roll:

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7th August 2004, 08:54 AM	(permalink)
escin	need a small power supply i need a small power supply for my peak charger.i need 12v 7amp power supply.it must be small.help me... A.S.A.P (as soon as possible) __________________ make me sick with project

7th August 2004, 09:33 AM	(permalink)
Exo	what is small for you? 7Amps using a normal mains transformer (and required capacitors for smoothing) is not gooing to be really small...

7th August 2004, 07:50 PM	(permalink)
samcheetah	7 Amps can never be small!!!!!!!!!! that is if u go for a linear PSU u r gonna need a BIGGG transformer (probably a toroid one), a BIGGG cap, and a BIGGG heatsink. and maybe u would have connect transistors in parallel to get that much current. and all of them will require a BIGGGG surface area to dissipate heat. so u see it cant be small. but u could go for a switcher. that might reduce the size somewhat.

7th August 2004, 11:08 PM	(permalink)
ante	Escin, If you have an old PC power supply lying around, will that be too big and heavy for you? Ante :roll:

8th August 2004, 04:55 AM	(permalink)
railmanxaero	An old PC power supply is 7 amps? I didn't know that. Maybe you can modify the PC power supply by taking the circuit board out of the case and custom making your own new case. It wouldn't that small but it might work. __________________ Hate me because I hate everything

8th August 2004, 10:51 AM	(permalink)
ante	Most old ATX supply’s have 8 Amps or more and if you don’t use much current from the 5 Volts line you can get a little bit more than the rating from the 12 Volts line. And it is much lighter than a transformer for 12Volts 8Amps. Ante :roll:

9th August 2004, 07:22 AM	(permalink)
Sebi	Yes, the PC PSU also a good solution, i've built a 12A 14.4V accu-charger from PC PSU. But the feedback originally on 5V output, so the 12V out not work properly without heavy 5V load. After rewiring the feedback to 12V out with additional 10k pot. the output adjustable. Also possible the current limiting.

9th August 2004, 04:06 PM	(permalink)
ante	Sebi, I have tested different supplies and been as high as 47 Ohms as a load for the 5 V line but I prefer to use a 10 Ohm 10 Watt resistor that have worked fine so far on 4 or 5 supplies. On some of the later models there are a power good signal required also. Ante :roll: