20-40V 2-10A DC Power Supply

[Krumlink]

I have been searching for a way to make a simple 20 to 40 Volt power supply that can supply several amp's, for the ZVS Flyback Driver. If I can get AT LEAST 20V and AT LEAST 2 Amps, Then I can be happy

I have seen people rewind their MOT's, but How can I do this without doing that?

 

[dknguyen]

What's an MOT? Are you trying to step around using the mains? It doesn't seem overly difficult if you use the mains (transformer and bridge rectifier)...uh and a switching converter. That might be harder.

 

[Krumlink]

Yeah, That is my ideal solution and the one that I want to do. Any suggestions

An MOT is a Microwave Oven Transformer.

 

[dknguyen]

THe diode rectifier and transformer are simple, but unless you get a variable transformer (variac or w/e? whic his really expensive), I don't know how to build a variable switch mode power supply. I'd just buy one personally except it might be hard to find a 20-40V one. The variable voltage part is the hard one for me.

 

[Krumlink]

No, Not variable voltage, just within that range.

 

[dknguyen]

Oh, then that's easy. Just make a bridge diode rectifier with 4 large diodes (or buy one component that has them all together, though power levels may be lower), get a big...REALLY big, like 1000uF or even 4700uF capacitor, and just choose a transformer that will step down the 120VAC mains to a voltage low enough that the voltage you want will be created by the bridge rectifier+capacitor.

You can only pull 1500W max out of a wall socket though (and efficiency is not 100%, so 40V@10A is out of the question, but 2A is very possible at any of your voltages.

 

[picbits]

40v at 10 amps is only 400 watt - easily achievable from a decent toroid. You would also need some capacitors waaay bigger than 1000uf (read as 20,000 uf upwards depending on how much ripple you can live with).

I'm building almost a 1kw linear power supply at the moment out of 6 toroidal transformers.

I'm also desiging a digitally controlled variable power supply from 0-30v and 0-10amp output to go with it.

It will have:

Fixed +5, +12, +15, +18 and +24 volts at 1A
Fixed -5, -12, -15, -18 and -24 volts at 1A
0-30v at 0-10 Amps x 2 (digitally controlled + RS232 monitoring)
0 to -30v at 0-3 Amps
12 / 24 volts switchable unregulated at 12 amps
+/- dual rail power at 30-0-30v at 6 amps.

 

[Hero999]

I probably doesn't even need to be regulated.

How about a 250VA 24V transformer with a bridge rectifier and huge filter capacitor with a variac on the primary to vary the voltage?

 

[dknguyen]

40v at 10 amps is only 400 watt - easily achievable from a decent toroid. You would also need some capacitors waaay bigger than 1000uf (read as 20,000 uf upwards depending on how much ripple you can live with).

Whoops! I don't know how I ended up with 4000W from 40V@10A!

 

[Krumlink]

Hero, I don't have any 240V Plugs in my house except for the basement, and I wanted this thing just to be able to plug into any 120AC outlet. I like the Toroid Idea, How would I progress with that?

 

[Nigel Goodwin]

Hero, I don't have any 240V Plugs in my house except for the basement, and I wanted this thing just to be able to plug into any 120AC outlet. I like the Toroid Idea, How would I progress with that?

Just buy a transformer of the voltage and current you want, toroids of various voltages are freely available, and quite reasonable cost. Then a large bridge rectifer, and some nice large electrolytics.

 

[kchriste]

I'll just add to the above: try and find a transformer locally and save on shipping!
NOTE: You can combine two identical 12VAC transformers to get your 24VAC.

 

[Hero999]

Hero, I don't have any 240V Plugs in my house except for the basement, and I wanted this thing just to be able to plug into any 120AC outlet. I like the Toroid Idea, How would I progress with that?

I didn't say 240V, I said 250VA.

 

[Krumlink]

In my house we have 240VAC, I know you said 250VAC.

Anyways, does anybody have a schematic for the Toroidal PS?

 

[dknguyen]

In my house we have 240VAC, I know you said 250VAC.

Anyways, does anybody have a schematic for the Toroidal PS?

I read VA...anyways. You know what VA (volt-amps) is right? It's a measure of power when you've combined the real and imaginary power together. The power output for AC isn't constant- it's a periodic sinusoidal and if the voltage and current aren't in sync, the real power you get is less than the VA. As it oscillates the imaginary power and real power periodically increase and decrease, but always combine to be the same VA. https://en.wikipedia.org/wiki/Volt-ampere

It's just a transformer feeding into a diode bridge which feeds into a capacitor that sits in parallel with the load. Whether the transformer is toroidal or not doesn't really change the schematic.

 

[Hero999]

In my house we have 240VAC, I know you said 250VAC.

No I didn't, please re-read my reply.

 

[Krumlink]

ANYWAYS!

Does anybody have a schemmy for it?

 

[dknguyen]

Like I said, it's nothing more than transformer feeding a diode bridge feeding a capacitor:
http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/rectbr.html

 

[Krumlink]

Sorry the link is broke.

I know how to hook up a transformer with a rectifier and stuff, but what about the toroidal PS?

 

[dknguyen]

Sorry the link is broke.

I know how to hook up a transformer with a rectifier and stuff, but what about the toroidal PS?

How is a toroidal PS any different from a PS that uses a regular transformer? A toroidal PS is just a PS that uses a toroidal transformer- no difference in the wiring, just the specific type of component being used.

Odd...the link works just fine for me. See if this specific image from the link works. THe inductor is optional:
http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/ietron/rectbr3.gif