50V input, 100V output problem

Thread Starter

joemmech

Joined Jan 22, 2010
32
Hi All. I am trying to design a circuit that has a 50V input and the output is 100V. Can anyone give me an idea on how to make the circuit? I need help on this, I started this morning but until now I cannot think of any circuit that will have a 50V input and the output is 100V.
 

SgtWookie

Joined Jul 17, 2007
22,201
Is your input AC or DC?

If AC, a transformer is going to be your easiest solution.

If DC, you're going to need a DC-DC converter.

Whatever your output current requirement is, you will need more than twice that for your input current; as there will be at least some loss during the conversion. Some converter designs can get better than 90% efficiency.

So, if you have a 90% efficient converter, for each amp of output that you need at 100v, you will need 50v x 100v/(50V*90%) = 2.222...Amperes input current at 50v.
 

bertus

Joined Apr 5, 2008
19,939
Hello,

I moved the thread here.
As count_volta already told you , you posted in the wrong forum.
Please take care to choose the right forum.

Greetings,
Bertus
 

Thread Starter

joemmech

Joined Jan 22, 2010
32
Sorry if it was place in the wrong forum. As I tried to enter this thread to the forum I encountered an Internal Server Error and I wasn't able to check it again if it was place in the correct forum. Anyway, my input is a DC supply. Our current set-up requires only a 25V output, we didn't have a problem with it since our input is 50V. Now, we are required to have a 100V output but the problem is our maximum input is only 50V. In addition to this, our circuit is already placed in a Laid-out board so we are looking for a way in which the revision that we are going to do won't make a big change in our circuit.
 

SgtWookie

Joined Jul 17, 2007
22,201
So, you need 100V out.
AC or DC out?

What current do you need for the output at 100v?

What is the current input at 50v?

How much space do you have left on the board for this?
 

Thread Starter

joemmech

Joined Jan 22, 2010
32
Our current setup is designed to have a 1Amp input at 50V and the output current can reached up to 120Amps DC depending on the requirement.
 

SgtWookie

Joined Jul 17, 2007
22,201
Let's see - you have 1A input at 50V DC, and you want 100V out at 120A.

Were you planning on including a small nuclear power plant on the board to generate all this extra power required? Because you'll need at least 240A input with a 100% efficient DC-DC converter, and that's just not going to happen.

Or were you talking extremely short bursts of 120A, with a long period of recovery in between?
 

Thread Starter

joemmech

Joined Jan 22, 2010
32
It is just a short burst of 120A. I think it is just around 1ms to 2ms burst. In our setup we are using a capacitor so that we can achieve this high current.
 

Thread Starter

joemmech

Joined Jan 22, 2010
32
Yes, it is only a short burst of 120A. I think it is only around 1ms - 2ms. In our current setup we are using a capacitor bank to achieve this current. Our problem is that in our setup we only have a 50V supply to charge the capacitor bank and we want to have an output of 100V.
 

SgtWookie

Joined Jul 17, 2007
22,201
OK, so you have 50v 1A input, and you have a 60uF capacitor that you need to charge up to 100v in 12 seconds or less? Is that about right?

Or perhaps I'm confusing this thread with another one. :confused:

What is the total capacitance that you need to charge to 100V?

How much time do you have to charge up these capacitors?
 

Thread Starter

joemmech

Joined Jan 22, 2010
32
You are right SgtWookie. We charge the capacitor for 12seconds. The capacitor we are using is also about 60uF. We expect that the time to charge the capacitor to 100V is double compare to the time to charge the capacitor to 50V. What we are doing will be applied to Mosfets.
 

SgtWookie

Joined Jul 17, 2007
22,201
Well, this still doesn't make much sense.

If you have a 1A constant current limited to 50v available, it only takes 3mS to charge a 60uF cap to 50v.

If you have a 50v supply that is limited to a maximum of 1A current via a 50 Ohm resistor, then the cap will be charged to over 49V in under 12mS.

How many of these 60uF caps are you charging that it takes 12 seconds? One thousand of them?

And you say that you're applying the output to MOSFETs - a MOSFET is a switch, not a load - unless you are testing the MOSFETs for some reason.
 

myforwik

Joined Feb 15, 2010
11
If you want little pulses like that you should be able to get away with a simple voltage doubler and a switching circuit.
 

Thread Starter

joemmech

Joined Jan 22, 2010
32
This is for the UIS Test for Mosfets. This is the methodology of the test:
http://www.greatwallsemi.com/AppNotes/UIS.pdf

The Vdd value that we will be using is 100V,120A. That is the application of what we are doing. The maximum current 120A is only a ~3ms pulse but we are not using the 120A always since there are some devices that has a lower current specs for the UIS.
 

Thread Starter

joemmech

Joined Jan 22, 2010
32
Guys I think you are confused with what I am trying to do here. Our circuit can already supply a maximum of 120A what ever the input voltage is so we don't have a problem with that anymore. Our main concern is the input voltage, from 50V,1A we want to make it into 100V,1A. Our first solution is to use a transformer so that we can step up the voltage but this will make our circuit look bulky, if we can find a solution where it won't make our circuit look bulky then it will be much better.
 
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