I am designing a device which has two AC input signals. The Input signals are as follows.

A - AC Signal A
B - AC Signal B
Com - Shared Neutral for above inputs

Voltages of these signals could be anywhere between 12V-35V(rms,50Hz). These signals are used as both power and control signals for the device. The functionality of the circuit is like following.

AC signal applied between A and Com - Do Task X
AC signal applied between B and Com - Do Task Y
AC signal applied between both A,Com and B,Com - Do Task Y (Same as above)

Since it's hard to work with AC unregulated signals I wish to convert them to DC signals(and also DC power for the circuit will be drawn from the signals) and probably implement the rest of the circuit with logic gates or transistors. For this reason I need them to be rectified and share a common ground. I have designed following circuit with two bridge rectifiers and common ground, but it's no good. When AC is applied to Com and B, on the negative half cycle current conducts through the rectifier of signal A. I would be extremely grateful if someone could guide me for a better implementation.

I have also tried to create some other designs but couldn't make it to functional one.

Edit: I prefer a design without a center tap transformer

Current circuit design


I have modified the design with the suggestions from @Kyle B and now I have a +Vcc GND -Vcc type power supply which is absolutely fine for my design.

Edit: With the excitement of voltage outputs I forgot to measure currents. When I measured them later it turned out to be order of hundreds which suggested an open circuit. Later I found out there is indeed and open circuit through diodes in this circuit. So this design not longer valid and I'm back to any new suggestions again :-(

new schematic design

output waveform

  • \$\begingroup\$ A, B and Com are connected to a center tap transformer ... one bridge rectifier between A and B ... Com connected to ground ... the two outputs of the bridge rectifier are the + and - ..... \$\endgroup\$
    – jsotola
    Dec 15, 2020 at 5:54
  • \$\begingroup\$ @jsotola thanks for the response. That is a design I have considered. But I prefer an implementation without a transformer (considering cost and size). Is there any other method? \$\endgroup\$
    – Anuradha
    Dec 15, 2020 at 6:01
  • \$\begingroup\$ Is it possible to change the phase of one of your input AC signals??? If you can flip one 180 degrees, you won't have this problem. \$\endgroup\$
    – Kyle B
    Dec 15, 2020 at 6:05
  • \$\begingroup\$ And... If you're simulating this, are your phases correct to "reality"??? \$\endgroup\$
    – Kyle B
    Dec 15, 2020 at 6:05
  • \$\begingroup\$ @KyleB hi, The signals are meant to be supplied from a same source with switches so I don't think there could be much phase difference. I'm not sure if putting a phase difference will work since it's not essential to be same sources are connected at once? \$\endgroup\$
    – Anuradha
    Dec 15, 2020 at 6:10

2 Answers 2


Flip the bridge rectifier around

TY for the points ;)


It seems to me the simplest method would be to use half wave rectifiers (diodes) and use a common ground for inputs and outputs. That way you can have both outputs moving in the same polarity and completely independent.


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