Limit DC Voltage's Current Supply

Hello,

I'm trying to do a "simple" setup of charging a capacitor in Simulink.

I'd like to figure out how to limit the current the DC Voltage Supply can source.

Problem:

• Power source 1kV at 1 Watt
• 1uF capacitor in series with 2k Ohm Resistor
• Plot time vs. voltage of capacitor from 0V to 900 V

Answer 1

[ADragon]

Hi Bryan, you can do this easily is Simscape, though you will have to use a controlled voltage source instead. AD

[Bryverine]

With this setup, the supply will just start low and grow in potential (see top figure). Shouldn't the voltage remain the same and the current vary?

Sorry if this is stupid, but I guess I expected the current to look like the bottom figure (not to scale).

[ADragon]

No, not stupid. I may not have given you exactly what you are looking for. Do you have a power limit or a current limit? At t=0, capacitor voltage will be zero, so you will just have the resistor. 1 mA will only give you 2V drop across the resistor. So, having a current limit, the power supply will be 2V at t=0. The model I showed previously has a power limit. At t=0, Vsupply = 44.72V and I= 22.36 mA. The circuit is in balance and Power = 1W.

[Bryverine]

Ah, I see. I guess I didn't write the question quite right!

I was considering DC/DC converters that list power and output current for the converted output voltage. The one I have been looking at lists 1Watt, 1KV out, and 1mA out.

This feels like it should be an easy model, I'm just not sure which components to use.

[ADragon]

Ok. I have not dealt with DC/DC converters on a very deep level, but I think you will need some more complexity in your model. There is a DC/DC converter block in the Simscape Electronics library that you can check out. Perhaps this will provide what you are expecting. Or, you can build your own circuit based on the circuit in the documentation.

[Bryverine]

Interesting, I will give that a try! I was hoping to just start after the DC/DC converter to avoid adding extra "unnecessary" complexity.

EDIT: I can't get it to work. I found a current limiter block, but I can't seem to get it to work either. Could this current limiter block be the way to solve my problem if I could implement it properly?