Variable Voltage Supply

Variable Voltage supply I am building. Three outputs and a digital readout.

I learned that the linear regulators will be extremely inefficient, especially when doing something like stepping 20V down to 5v. I should use a switched regulator (similar to a Class D amp). The lm2679 seems good. MC34063AP seems better.

I ordered some LM2575T, use the schematic on the top of page 24: http://www.ti.com/lit/ds/symlink/lm1575.pdf