Transformerless Buck Converter

I've been trying to wrap my head around getting 110Vac down to usable DC. The best starting point seems to be ~24V.

Above a few amps, transformers make sense. Switching converters have the potential to draw extremely high current in short bursts.

But transformers are expensive, so I've been looking at alternatives.

Bridge

Not much here, first stage is a bridge rectifier and a ripple cap. That gets us a very noisy 110Vdc.

Isolation

Transformer provide electrical isolation. But we can have that too. Take two (or more) capacitors. At any point one of the caps is connected to Vin and the rest are connected to Vout. This may not be necessary because it's basically the same thing that happens in the next step.

Step Down Bank

I'm going to convert 110Vdc to 27.5Vdc using switching and two banks of capacitors.

Each bank will have 4 1000uF 50V capacitors. The bank is controlled with a signal, Q or !Q. When Q, the capacitors are in series and charging. When !Q, the capacitors are in parallel and discharging.

I did a control circuit and for each capacitor I need 3 transistors. The TO-220 TIP120 Darlington pair looks good. They're about $0.17 a piece and the cap is about $0.13, so each 'unit' costs about $0.63 bringing in the two banks at around $5. I can drive the whole thing with a 555.