The rectifier circuit of Fig. 4-7aserves as a simple voltage doubler, having an
output of twice the peak value of the source. For ideal diodes, C1 charges to Vm through D1 when the source is positive; C2 charges to Vm through D2 when the source is negative. The voltage across the load resistor is the sum of the capacitor voltages 2Vm . This circuit is useful when the output voltage of a rectifier must
be larger than the peak input voltage. Voltage doubler circuits avoid using a
transformer to step up the voltage, saving expense, volume, and weight.
The full-wave rectifier with a capacitive output filter can be combined with
the voltage doubler, as shown in Fig. 4-7b. When the switch is open, the circuit
is similar to the full-wave rectifier of Fig. 4-6a, with output at approximately
Vm
when the capacitors are large. When the switch is closed, the circuit acts as
the voltage doubler of Fig. 4-7a. Capacitor C
1
charges to Vm
through D1when