# Charging capacitor bank with current limiting circuit

Posted on Feb 7, 2014

A useful current limiting circuit (shown below), that allows me to select a maximum current through a load. The circuit is set to give a 480 mA max current. As the load resistance increases, the SER of the limiting circuit drops away. The following plot shows current through the load versus load resistance. . . However, what happens if I want to charge a

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capacitor bank using this circuit. Where would I put it Current needs to flow through R_sense to cause a voltage drop in order for the circuit to function. If I just add a capacitor after the sense resistor. . . Then the voltage of the cap jumps up to 4. 8 volts immediately (which I`m guessing would draw a massive current, fry my supply, and negate the point of the current limiting circuit) This looks pretty logical to me. If a cap is connected to an ideal voltage source, it will get an infinite current and be at 4. 8 V instantaneously. What do I need to do in order to reproduce the effect shown in Oli`s lowest plot For the second simulation with the cap at the top, you need to set the cap voltage to 0V initially. I did this by setting the voltage at the MOSFET drain to 4. 8V, the. ic V(n001) 4. 8 you can see next to the cap is the SPICE command to do this. This means both ends of the cap are at 4. 8V hence there is no voltage across it. I`m not sure how you do this in Circuit Lab, if you can link to your circuit maybe I (or someone else more familiar with it) can help. Oli Glaser Sep 5 `12 at 13:03 Okay, thanks. Unfortunately it seems there is no way to do this in CircuitLab yet. They suggest using a time controlled switch switching at T=0 as a workaround. CircuitLab is pretty, but it`s not as sophisticated as SPICE - if you are planning on doing plenty of EE, then I`d advise getting to know SPICE (LTSpice is a great free...

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