PSU regulaton - Electronic Circuits Projects Diagrams Free

windozeuser · 27th March 2006, 06:08 PM

I am currently building a new power supply for my laptop. I have a 12.8 volt transformer, 50 Volt 6A Rectifier, and two 1000 uF capacitors. The problem is I need regulation, whats the simplest way to regulate this supply? Most IC regulators I've seen can't handle the current I need which is 4amps. Can I use a zener diode, and are the capacitors enough filtering?

Thanks

The laptop specs are 10.6 volts @ 3.5 amps. But I can run it at 12.8 volts at 4A works perfectly!

Synapse · 28th March 2006, 03:08 AM

Use a normal regulator (7812) with a Pass Transistor to get higher output current.

Google will get you circuits

windozeuser · 29th March 2006, 06:17 PM

I'm using an Adjustable Voltage Regulator LM317T which has a maximum output current of 1.5A. How would I increase this to say 4A with a 5A surge? Would I need transistors? Can I buy them at radioshack if possible?

Roff · 29th March 2006, 07:16 PM

Use LM338K, which is good for 5 amps. You will also need about 30,000uF to get the unregulated ripple down to about a volt, which is about all you can tolerate. Don't forget a big heatsink, because you will be dissipating 12-15 watts in the regulator. You might want to think about a switching regulator, which would be much more efficient.

Oznog · 29th March 2006, 07:33 PM

It can probably run at 12v since I expect it has a switching regulator inside. But it may not be working as well as it should. You may be risking blowing up the computer's internal regs.

As noted, this is a crapload of heat for a linear reg. This is basically impractical to run this way. It would take a huge power transistor, heatsink, and makes a ton of heat. The alternative of a switcher is often a tricky beast but it's a more reasonable solution.

IMHO this whole project is not practical. Just get a new supply on eBay? It will be far cheaper, safer, and better packaged. There's just too much risk of blowing the laptop and laptops usually need easily portable supplies. If it's a new computer you certainly don't want to damage it, if it's ancient then eBay will have those supplies for next to nothing.

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27th March 2006, 06:08 PM	(permalink)
windozeuser	PSU regulaton I am currently building a new power supply for my laptop. I have a 12.8 volt transformer, 50 Volt 6A Rectifier, and two 1000 uF capacitors. The problem is I need regulation, whats the simplest way to regulate this supply? Most IC regulators I've seen can't handle the current I need which is 4amps. Can I use a zener diode, and are the capacitors enough filtering? Thanks The laptop specs are 10.6 volts @ 3.5 amps. But I can run it at 12.8 volts at 4A works perfectly!

28th March 2006, 03:08 AM	(permalink)
Synapse	Use a normal regulator (7812) with a Pass Transistor to get higher output current. Google will get you circuits

29th March 2006, 06:17 PM	(permalink)
windozeuser	I'm using an Adjustable Voltage Regulator LM317T which has a maximum output current of 1.5A. How would I increase this to say 4A with a 5A surge? Would I need transistors? Can I buy them at radioshack if possible?

29th March 2006, 07:16 PM	(permalink)
Roff	Use LM338K, which is good for 5 amps. You will also need about 30,000uF to get the unregulated ripple down to about a volt, which is about all you can tolerate. Don't forget a big heatsink, because you will be dissipating 12-15 watts in the regulator. You might want to think about a switching regulator, which would be much more efficient. __________________ Ron

29th March 2006, 07:33 PM	(permalink)
Oznog	It can probably run at 12v since I expect it has a switching regulator inside. But it may not be working as well as it should. You may be risking blowing up the computer's internal regs. As noted, this is a crapload of heat for a linear reg. This is basically impractical to run this way. It would take a huge power transistor, heatsink, and makes a ton of heat. The alternative of a switcher is often a tricky beast but it's a more reasonable solution. IMHO this whole project is not practical. Just get a new supply on eBay? It will be far cheaper, safer, and better packaged. There's just too much risk of blowing the laptop and laptops usually need easily portable supplies. If it's a new computer you certainly don't want to damage it, if it's ancient then eBay will have those supplies for next to nothing. __________________ I thought what I'd do was I'd pretend I was one of those deaf-mutes.