Hi guys, I am trying to charge a super capacitor with LM2596 for its high efficiency and higher output current compared to linear regulators. My question is that how to set it as current charging mode until the capacitor reaches the output voltage? I am asking this question because the capacitor is huge and I don't want to use a current limiting resistor which gives me very big time constant (t=RC). From this trickle charger based on LM317 (http://www.circuitstoday.com/battery-charger-circuit-using-lm317) I find the charging current can be set to maximum most of the charging period. Can this applied to LM2596 the same?

 

Hi, and welcome to the forum.

I designed a simple switcher to be a constant current regulator with a voltage limit using a LM2576-adj, which is functionally very similar to your LM2596 (different switching frequency). When the switch is in the down position it functions as a constant voltage regulator. When the switch is in the up position it functions as a constant current regulator. (Amp out = 1.2/ (R8 + variable resistor)) D1, a zener diode, sets the max voltage out, (Max out = zener voltage plus 1.2 V) Use the component values dictated in the app note. You will need to use the LM2596-adj for this circuit.

 

Try this part- designed to do just that.