VOLTAGE DOUBLER CIRCUIT (Developed by Greinacher in 1990):Both full wave and half wave rectifier circuits produced DC voltage less than AC maximum voltage. For higher DC voltage, voltage doubler circuit is used.During negative half cycle, the capacitor C1 is charge through diode D1 to voltage Vmax. During the next half cycle the terminal Y of the capacitor C1 rises to Vmax and hence the terminal X attains a potential 2Vmax. Thus, capacitor C2 is charged to 2Vmax through D2. Normally, the voltage across the load is less than 2Vmax depending upon the time constant of the circuit,capacitor C2 and the load RL.

Terminal X: node between C5 and D7Terminal Y: node between C5 and R3