Bridge Rectifier Grounding

[kittydog42]

I have made a power supply where I am taking in 24VAC from a transformer, and converting it to 10VDC, through a bridge rectifier and a switching regulator circuit. The 10VDC is being used to generate a 0-10V signal with a pot to control an actuator motor position. The actuator motor uses the same 24VAC for it's power that is used for the power supply. There are only 3 terminals on the actuator - 10VDC signal, 24VAC power, and common ground. My question is, will I have any problems if I connect the zero voltage output of the DC power supply to the neutral of the 24VAC transformer? Also, should I ground the neutral output of the transformer as I was planning? This whole circuit works fine when applying 24VDC power to the input, but I don't want to try it with AC without finding an answer to this question.

 

[crutschow]

What is the "neutral" connection on your transformer?

Normally you can not ground the transformer output of a bridge rectifier (2 transfomer output leads) if you ground one side of the DC output.

If you use the 24VAC output at the same time, it can not share the DC common.

If you draw the circuit, you'll see the problem.

A possible solution is to generate the DC with a half-wave rectifier from one of the transformer leads which then allows you to use the other transformer lead for both the AC common and the DC common. Of course that generates significantly more DC ripple (requiring a larger filter capacitor) and adds a DC component to the transformer current which can lead to transformer saturation, but may be ok if the required DC current is a small percentage of the rated transformer AC current (probably no more than 10%).