# Voltage multiplier balancing issues

#### SiCEngineer

Joined May 22, 2019
238
Hi All,

I am designing an SMPS and have an issue with my output voltages. I am using a voltage quadrupler to boost my transformer output by 4x. I will attach a schematic of the multiplier rectifier to this thread.

My issue is that, although I expect 800V and 400V at my output for the two loads, they are quite imbalanced. I get 829V and 407V, which is quite the difference. I have tried multiple changes to my schematic but the imbalance seems to remain. The diodes are ideal, as are the capacitors.

Any suggestions for these discrepencies would be appreciated!

Capacitors are 100nF each.

#### KeithWalker

Joined Jul 10, 2017
1,216
Hi All,

I am designing an SMPS and have an issue with my output voltages. I am using a voltage quadrupler to boost my transformer output by 4x. I will attach a schematic of the multiplier rectifier to this thread.

My issue is that, although I expect 800V and 400V at my output for the two loads, they are quite imbalanced. I get 829V and 407V, which is quite the difference. I have tried multiple changes to my schematic but the imbalance seems to remain. The diodes are ideal, as are the capacitors.

Any suggestions for these discrepencies would be appreciated!

Capacitors are 100nF each.
What are the values of R6 and R7? Your circuit is not symmetrical so why would you expect it to be balanced?
R6 is connected across the positive supply but there is no resistor connected across the negative supply. R7 is connected between positive and negative.

#### SiCEngineer

Joined May 22, 2019
238
What are the values of R6 and R7? Your circuit is not symmetrical so why would you expect it to be balanced?
R6 is connected across the positive supply but there is no resistor connected across the negative supply. R7 is connected between positive and negative.
I have one resistor across the positive and negative supply to get 4x the output voltage of transformer. The other resistor is connected across just the positive supply so that I get 2x the output voltage of the transformer. I originally had this as two secondary windings each feeding a full wave voltage multiplier, with one resistor connected across one voltage multiplier and the other resistor connected across both of the voltage multipliers. In that configuration, I didn’t have this issue. But the Essence of what I was trying to do is the same, but without the extra secondary winding. So I’m unsure what is different.

The resistor values are 10.5kOhm for the 400V output and the 800V output resistor is 270Ohm.

#### AlbertHall

Joined Jun 4, 2014
10,387
All four capacitors are 100nF?
What frequency is this circuit running at?
Is the resistor across the 800V output really 270Ω (3A, 2.4kW)?

#### SiCEngineer

Joined May 22, 2019
238
All four capacitors are 100nF?
What frequency is this circuit running at?
Is the resistor across the 800V output really 270Ω (3A, 2.4kW)?
The frequency is 180kHz. I think I have those two mixed up and the 800V output resistor is 10.5kOhm.

#### AlbertHall

Joined Jun 4, 2014
10,387
The frequency is 180kHz. I think I have those two mixed up and the 800V output resistor is 10.5kOhm.
For the 400V output 270Ω would still be 1.5A, 600W. If that is so those must be pretty impressive 100nF capacitors.

#### SiCEngineer

Joined May 22, 2019
238
For the 400V output 270Ω would still be 1.5A, 600W. If that is so those must be pretty impressive 100nF capacitors.
How would I calculate the appropriate capacitors in that case?

#### AlbertHall

Joined Jun 4, 2014
10,387
How would I calculate the appropriate capacitors in that case?
Are you sure that your circuit actually produces 407V across a 270Ω resistor?