Voltage Doubler Issue

[lesabb]

I've drawn 2 schemo in LTSpice and performed simulations. Can anyone explain to me why one of them gives me the correct 34V and 68V but the other gives me the double voltage twice?

Thanks

L

[Zero999]

That's what you should expect.

Trace the circuit out, using conventional current flow charging the capacitors and you'll come to the same conclusion.

Don't forget the 0V nodes are joined together.

[Jolle]

In the second schematic you have connected the "negative" terminal of the voltage source to the node between C1 and C2 which will be at approx 34 V.

When the voltage source goes positive the final voltage at the "positive" terminal of V1 will therefore be the 34V plus the actual voltage of the source - giving you the 68V you simulate in LTspice...

Does that make sense?

[lesabb]

I understand the doubling part. What I don't get is why the bottom portion also gives 68v when it's not in a "doubler" configuration.

[SeanB]

It is being fed voltage on the common ground connection by the upper negative doubler, so floats down ( the bridge rectifier diodes are reverse biased fully there so do nothing to prevent this) to be the -34V from the doubler. As your measurement is referenced to this it looks like it has doubled to 68V.

Basically the top section is a half wave rectifier with positive and negative outputs, and you are then trying to connect the negative rail to the bridge rectifier.

[lesabb]

I get it! Thanks!