I am working on adding a super-capacitor to one of my 5V lines. Foolishly I tried adding the super-capacitor directly to the 5V line, but it over stresses my regulator to charge it all at once.
I am trying to design a very simple charging/ discharging circuit. Would this be the proper way to charge a large (2.2F 5.5V) super-capacitor?
What you have will work, although D12 is pointless. The problem is that when the cap is discharging onto the 5 V line, there will be a drop across D13. Using a Schottky as you show is a good idea, but the drop will still be around 1/4 volt. Another problem is that the voltage will go lower over time with the amount of charge drained from the cap.
You might consider putting the energy backup capacity before the power supply. That might allow the stored energy to be used more efficiently, and the voltage will stay regulated for a while.
If you charge your capacitor through a resistor, the charging efficiency will be less than 50%. You should try charging your capacitor through an inductor if you are designing a power circuit.
The circuit below may not apply to your circuit because of its complexity, but you can use the forward converter topology as seen as a general solution to the efficiency problem. The major losses are only on the diodes if the MOSFET is driven properly and the transformer is designed correctly.
simulate this circuit – Schematic created using CircuitLab
