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?

 

You will need to increase the charge current.

 

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?

 

When I plug this in, the voltage is limited to somewhere 400-600 volts. Far less than expected.

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?

 

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.

 

This is the LTspice version of the charging which seems to behave properly.