Art of Electronics 3rd ed. Figure 1.86
green: current trough inductor
blue: capacitor's voltage
red: current trough resistor
yellow: voltage of capacitor
Resonant charging (lower circuit) is lossless (with ideal components) compared with the 50% efficiency of resistive charging.
Charging is complete after tf, equal to a half-cycle of the resonant frequency f=1/sqrt(2*pi*L*C)
The series diode terminates the cycle, which would otherwise continue to oscillate between 0 and 2Vin.
With resonant charging the capacitor charges up to 2x of the charging voltage (minus diode drop).
