Pulsed Power Circuit

Discussion in 'Power Electronics' started by beginnerDesigner, Sep 15, 2016.

1. beginnerDesigner Thread Starter New Member

Sep 15, 2016
3
0
Hi,

I am trying to model a circuit to represent charging a capacitor then a switch flipping and discharging through a resistor. I am able to get the capacitor to charge to the voltage I need, but there's not enough energy when I discharge. I've increased the capacitor size hoping to get more charge but that just lowers the voltage. Are there any ideas on how to get the energy in the capacitor increase within a limited time and not decrease the voltage?

2. AlbertHall Well-Known Member

Jun 4, 2014
1,359
256
You will need to increase the charge current.

3. beginnerDesigner Thread Starter New Member

Sep 15, 2016
3
0
Ok thanks. I'll try to figure out how to do that.

if I want Q = 1.65 kJ and V = 25 kV...Q = V*C so C = 1,650/25,000 = 66 mF. Now if I want to charge that in 20 us, I know that tao = R*C and a full charge (1.65 kJ) is at 5*tao right? So tao = 4 us.

So R = tao/C
R = 4us/66mF
R = 60.6 micro-ohms.

When I plug this in, the voltage is limited to somewhere 400-600 volts. Far less than expected. Any ideas why or how I could tackle this problem?

4. AlbertHall Well-Known Member

Jun 4, 2014
1,359
256
The maths is right. Though the charging current of about 380,000 amps from a 25kV source is very scary.
What are 'plugging' all this into?

5. beginnerDesigner Thread Starter New Member

Sep 15, 2016
3
0
I'm just simulating it in spice. lol this isn't real. I'm just trying to figure out why my theoretical circuit wasn't working right.

6. AlbertHall Well-Known Member

Jun 4, 2014
1,359
256
This is the LTspice version of the charging which seems to behave properly.