4-50
Figure 4-48A.—Voltage tripler. POSITIVE ALTERNATION
The other half of the input cycle is shown in view B. C2 is charged to twice the input voltage, or 400
volts, as a result of the voltage-doubling action of the transformer and C1. At this time, C2 and C3 are
used as series-aiding devices, and the output voltage increases to the sum of their respective voltages, or
600 volts. R1 and R2 are proportional according to the voltages across C2 and C3. In this case, there is a
2 to 1 ratio.
Figure 4-48B.—Voltage tripler. NEGATIVE ALTERNATION
The circuit shown in figure 4-49 is that of a full-wave voltage doubler. The main advantage of a
full-wave doubler over a half-wave doubler is better voltage regulation, as a result of reduction in the
output ripple amplitude and an increase in the ripple frequency. The circuit is, in fact, two half-wave
rectifiers. These rectifiers function as series-aiding devices except in a slightly different way. During the
alternation when the secondary of the transformer is positive at the top, C1 charges to 200 volts through
CR1. Then, when the transformer secondary is negative at the top, C2 charges to 200 volts through CR2.
R1 and R2 are equal value, balancing resistors that stabilize the charges of the two capacitors. Resistive
load RL is connected across C1 and C2 so that R
L
receives the total charge of both capacitors. The output
voltage is +400 volts when measured at the top of R
L, or point "A" with respect to point "B." If the output
is measured at the bottom of RL, it is
-
400 volts. Either way, the output is twice the peak value of the ac
secondary voltage. As you can imagine, the possibilities for voltage multiplication are extensive.
