# Half Wave Voltage Doubler using Diodes

Voltage multipliers use clamping action to increase peak rectified voltages without theÂ necessity of increasing the transformerâ€™s voltage rating. Multiplication factors of two,Â three, and four are common. Voltage multipliers are used in high-voltage, low-currentÂ applications such as cathode-ray tubes (CRTs) and particle accelerators.

Voltage Doubler

Half Wave Voltage Doubler

A voltage doubler is a voltage multiplier with a multiplication factor of two. A half-wave voltage doubler is shown in Below Figure. During the positiveÂ half-cycle of the secondary voltage, diode D1 is forward-biased and D2 is reverse-biased.Â Capacitor C1 is charged to the peak of the secondary voltage (Vp) less the diode drop with theÂ polarity shown in part (a). During the negative half-cycle, diode D2 is forward-biased and D1Â is reverse-biased, as shown in part (b). Since C1 canâ€™t discharge, the peak voltage on C1 addsÂ to the secondary voltage to charge C2 to approximately 2Vp. Applying Kirchhoffâ€™s lawÂ around the loop as shown in part (b), the voltage across C2 is

VC1 â€“ VC2 + Vp = 0

VC2 = Vp + VC1

Neglecting the diode drop of D2, VC1 = Vp. Therefore,

VC2 = Vp + Vp = 2Vp

Under a no-load condition, C2 remains charged to approximately 2Vp. If a load resistanceÂ is connected across the output, C2 discharges slightly through the load on the nextÂ positive half-cycle and is again recharged to 2Vp on the following negative half-cycle. TheÂ resulting output is a half-wave, capacitor-filtered voltage. The peak inverse voltage acrossÂ each diode is 2Vp. If the diode were reversed, the output voltage across C2 would have theÂ opposite polarity.