Voltage Multiplier - Voltage Doubler and Tripler

Voltage Doubler and Tripler

A voltage doubler uses two stages to approximately double the DC voltage that would have been obtained from a single-stage rectifier. An example of a voltage doubler is found in the input stage of switch mode power supplies containing a SPDT switch to select either 120 volt or 240 volt supply. In the 120 volt position the input is typically configured as a full-wave voltage doubler by opening one AC connection point of a bridge rectfier, and connecting the input to the junction of two series-connected filter capacitors. For 240 volt operation, the switch configures the system as a full-wave bridge, re-connecting the capacitor center-tap wire to the open AC terminal of a bridge rectfier system. This allows 120 or 240 volt operation with the addition of a simple SPDT switch.

A voltage tripler is a three-stage voltage multiplier. A tripler is a popular type of voltage multiplier. The output voltage of a tripler is in practice below three times the peak input voltage due to their high impedance, caused in part by the fact that as each capacitor in the chain supplies power to the next, it partially discharges, losing voltage doing so.

Triplers were commonly used in color television receivers to provide the high voltage for the cathode ray tube (picture tube). Many 1970s TV sets used open triplers, and the individual diode sticks could be replaced if they failed.

Triplers are still used in high voltage supplies such as copiers, laser printers and bug zappers.