Hi
I have a 18V/18A DC power supply. I want to use this power supply to generate a 1Ampere CURRENT SQUARE WAVE. The load that I am driving is of 200Ohms approximately.

I used a transistor with its base given a square pulse from the function generator. The load is connected on the collector. Emitter is grounded. Transistor is repeatedly going in CUT-OFF and SATURATION. But in this way the maximum current that I am getting is (18V/200ohms) which is quite less.

Now I am not getting how to increase this current using the SAME DC power supply. Problem which I am facing is that potential across load will be (200x1=200V) so how to handle this with 18V DC power supply.
Should I use transformer?

Any help would be appreciated.

Sincerely
Richeek

 

What frequency?

 

Ideally it should go as high as possible. But for now 100KHz is good enough.

 

Is your load purely resistive, or are there reactive components? ie: inductive; capacitive.

 

For now I just want the concept. So any frequency would do. I guess I need to have something like a transformer but I have never used the transformer for this type of operation(I just use them to step down mains power supply). So not sure about that.

 

It is a purely resistive load. I should have mentioned all these things in the first post itself. My mistake.

 

If the load is purely resistive, you might be able to do it using a toroidal transformer. You'll probably need around 12a or so current in the primary winding, and you'll need an H-bridge that will handle that much current.

 

How will I generate 12A current? Could you please elaborate more on this? I was also thinking of transformer but do not know up to what frequency it can go and how much current can I get from it?

 

You will need an H-bridge that is rated for around 30A @ 20v, and you will need to wind your own toroidal transformer. The H-bridge will need to be able to switch pretty quickly. The high current will be on the primary side of the toroidal transformer. The secondary side will have around 200v RMS current at 1A. You'll need somewhere around a 1:12 ratio for the turns.

The higher the frequency, the smaller the toroidal transformer can be - up to a point. Then you wind up with power dissipation problems.

 

Thank you very much for the information. Instead of making one can I buy this type of transformer? That would be lot easier for me. Also are there any other solutions to this problem?

 

You'd be better off to start with a 200v DC power supply that is capable of at least 1A output.

 

Ohm's law:

I = V/R, 200V/200Ω = 1A

Resistance and voltage dictate current.