Experiment No. 3
AIM:- Design and implement voltage multiplier circuits.
APPARATUS:- Switching diodes – 1N4007, Capacitors, Signal generator, Variable AC supply,
bread board, Wires, CRO
THEORY:Voltage multiplier is in actuality a modified capacitor filter circuit (rectifier circuit) which makes
a DC output voltage that is two or more than two times the AC peak input. In this experiment, we
can look into full-wave voltage doubler, half-wave voltage doubler, voltage tripler and finally
quadrupler.
Half Wave Voltage Doubler
The input wave form, circuit diagram and output waveform is shown in figure 1. Here, all
through the positive half cycle, the forward biased D1 diode conducts and diode D2 will be in off
condition. In this time, the capacitor (C1) charges to VSmax (peak 2o voltage). All through the
negative half cycle, the forward biased D2 diode conducts and D1 diode will be in off condition.
In this time C2 will start charging.
Throughout the next positive half cycle, D2 is at reversed biased condition (open circuited). In
this time C2 capacitor gets discharged through the load and thus voltage across this capacitor gets
dropped.
But when there is no load across this capacitor, then both the capacitors will be at charged
condition. That is C1 is charged to VSmax and C2 is charged to 2VSmax. Throughout the
negative half cycle the C2 gets charged yet again (2VSmax). In the next half cycle, a half wave
which is filtered by means of capacitor filter is obtained across the capacitor C2. Here, ripple
frequency is same as the signal frequency. The DC output voltage of the order of 3kV can be
obtained from this circuit.
Fig.(1) Circuit diagram
Fig.(A) Input Waveform
Fig.(B) Output Waveform
OBSERVATION TABLE:Sr no.
Input voltage Vpp
Output voltage Vpp
Voltage Tripler and Quadrupler
Using the method of extension of half-wave voltage doubler circuit, any voltage multipliers
(Tripler, Quadrupler etc) can be created. When both the capacitor leakage and load are small, we
can achieve tremendously high DC voltages by means of these circuits that include several
sections to step-up (increase) the DC voltage.
Here; all through the first positive and negative half cycle is same as that of half-wave voltage
doubler. Throughout the next positive half cycle, D1 and D3 conducts and C3 charges to
2VSmax. Throughout the next negative half cycle, D2 and D4 conducts and C4 charges to
2VSmax. When more diodes and capacitors are added, every capacitor will get charged to
2VSmax. At the output; odd multiples of VSmax can be attained, if measured from the top of
transformer 2o winding and even multiples of VSmax can be attained, if measured from bottom of
2o winding of transformer.
Fig.Circuit diagram
OBSERVATION TABLE:Sr no.
Input voltage
Vpp
V
Output voltage
(Tripler) Vpp
PRECAUTIONS: 1. Loose and wrong connections are to be avoided.
2. The output waveforms should be obtained.
3. Parallax error should be avoided
RESULT:-
CONCLUSION:-
Output voltage
( Quadruple ) Vpp