Can anyone explain what is doing this diode-capacitor branch on a Boost converter?
When the switch closes, the bottom of C1 is connected to ground, and D1 charges C1. When the switch opens, the inductor causes the votage at the bottom of C1 to rise. This allows C1 to discharge through D2 into the load. Note that, in the DC case, C1 never charges up, since the inductor is a perfect short circuit, and draws infinite current. But since E is an ideal voltage source, it can simultaneously put out infinite current AND produce a voltage across zero resistance.