Construction and Working
Voltage doubler is basically a circuit, consisting of two semi- conductor PN diodes (rectifiers) and two capacitors, arranged in the form of bridge construction. The capacitors and rectifiers are arranged as shown in the figure.
The two capacitors, C1 and C2 are connected in series with each other and also with the load. In voltage doubler circuit the alternating current will first flow in a clockwise pattern and then in anti clockwise (Indicated by arrows in the diagram). When the current flows in a clockwise direction, the rectifier R1 will charge the capacitor C1 till the voltage reaches the peak of the positive voltage wave. In the similar manner, then the current flows in an anticlockwise direction, the rectifier R2 will charge the capacitor C2, till the voltage reaches the peak of the negative voltage wave.
As both the capacitors are in series with each other and the load, the opposite voltages generated in both of them will add up and discharged to the load. Thus a doubling effect will be produced, delivering a voltage which is twice the input. However, it is to note that the system will work only if the load is very small. In case the load increases, the doubling effect will not be produced.
Similar circuits are used to increase the voltage almost four times the input voltage, but only if the load current is very small. In many applications transformers are also used. However, they are expensive and do not provide the right quality of current.