Voltage
doubler circuit using NE555
The circuit diagram
of a very simple voltage doubler using NE555 timer is shown here. Here IC NE555
is wired as an astable mutivibrator operating at around 9KHz. The base of the
two transistors (Q1 and Q2) is shorted and output of the astable multivibrator
(pin 3) is connected to it. When the output of astable multivibrator is low, Q1
will be OFF and Q2 will be ON. The negative terminal of the capacitor C3 will be
shorted to ground through T2 and it will be charged to the input supply
voltage. When the output of the astable multi vibrator is high, transistor Q1
will be ON and transistor Q2 will be OFF. The capacitor C4 will be charged to
the voltage across capacitor C3 plus the input supply voltage (that is double
the input voltage). This is how the circuit works.
This voltage doubler
circuit can deliver only up to 50mA output current and above that current limit
the output voltage will be dramatically reduced. The actual output voltage will
be around 19V for a 12V DC input and also the output voltage will be a bit
unstable. Anyway, for low current applications this circuit is well enough.
· The circuit can be assembled on a vero board.
· The output current should not be allowed to
exceed 70mA.
· IC1 must be mounted on a holder.
