# Polarized capacitors in voltage doubler

Consider this voltage doubler:

.

I simulated the circuit using NON-polarized capacitors and WITHOUT the transformer as in this schematic:

and the output voltage (at C1) was still doubled. I have a couple of questions about this:

1. Why would people want to use polarized capacitors?

2. What is the purpose of the transformer?

Finally, after playing around with the circuit,

1. What happens if I reverse the orientation of both diodes? It seems that it inverts the sign of the output voltage, but this is only possible using non-polarized capacitors, which brings me back to my first question.

1) Why would people want to use polarized capacitors?

Because, usually, they have more capacitance per volume and are cheaper. Search for values like 1000uF, 2200uF, 4700uF or even bigger of ceramic ones and will find the answer. If your value is low, you don't need polarized caps.

2) What is the purpose of the transformer?

If the purpose of circuit is only a voltage doubler, its for isolation. But you may achieve bigger voltages ratio with the transformer. An isolation transformer is a safety device. Since the right part of circuit is floating, if you touch only at one point of the circuit you will not be electrocuted. In spite off, for example, if you touch the positive side of the last capacitor it will be grounded and the negative will be -V.

3) What happens if I reverse the orientation of both diodes? It seems that it inverts the sign of the output voltage, but this is only possible using non-polarized capacitors, which brings me back to my first question.

If you reverse the diodes you must reverse also the capacitors.

Also, generally, non polarized capacitors have lower inductance and resistances. So they act faster and are better suited for high frequencies circuits.

• +1. Note also the polarity of the first capacitor. When the transformer secondary goes negative the diode will clamp the + side of the cap at -0.7 V. From then on, in normal operation it will always be positive with respect to the left-hand side. Obviously, if you reverse the diodes you reverse the caps too. Feb 10, 2016 at 10:33