Voltage doubler or not?

I got a quick question! Is the circuit depicted in the link indeed a voltage doubler or is it just a bridge rectifier with smoothing capacitors?

• Link is broken. – Matt Young Feb 22 '13 at 0:20
• Link doesn't work. – NickHalden Feb 22 '13 at 0:20

It's a standard full BR with smoothing capacitors (with the option of using the center tap as circuit ground and having positive/negative rails)

One type of voltage doubler that looks a little similar is this:

Note that the above is assuming nothing about the transformer winding ratio, only whether the secondary voltage is doubled by the following circuitry.

• Maybe you could explain the importance of the number of windings on each coil. – Grady Player Feb 22 '13 at 1:00
• @GradyPlayer - the number of windings is irrelevant to my answer. It only focuses on whether the secondary voltage is doubled by the following cap/diode arrangement (e.g. if the ratio is 1:1 in the example circuit in my answer the voltage is doubled), which I assume is what the OP is asking. – Oli Glaser Feb 22 '13 at 7:52
• Whoever downvoted - what was the reason? If you think I have made a mistake please let me know. – Oli Glaser Feb 22 '13 at 7:56
• I certainly did not. Though I don't think that if that transformer were 1:1 it would not be a doubler, but just a normal rectifier. – Grady Player Feb 22 '13 at 14:22

The circuit pictured is a fancy BR circuit, because of the center tap connection, I would suspect that is only slightly better than just seperating the output lines with a capacitor, the more typical application with a center tap is to have a common ground with both + and - voltages out of the rectifier.

also with center tap, you can make a full wave rectifier with just 2 diodes (rather than the normal 4)

The reason that it isn't a doubler is that there aren't 2 times as many coils on the load side of the transformer (if the drawing is to scale.)

It is also possible with multiple taps to have multiple potentials eg., -15 -7, 0, +7, +15 (ish unregulated, VAC).

• Transformer schematics generally do not indicate the turns ratio, only sometimes whether it's step up or step down. Having two times as many coils on the secondary side would be no confirmation of the ratio being 1:2. This makes sense if you think about how would you draw for example, a 3000:1 turns ratio - there needs to be some text to indicate this, not the number of turns shown. – Oli Glaser Feb 22 '13 at 9:41