Hi, I am working on a project to take an input AC voltage , Vi, and keep it's output, Vo, held at a fixed 5.00V. I've studied a few ways to achieve this using a few AGC circuits. I am unable to get them to work properly and I believe it is due to my misunderstanding of the control loop. I'm using the AD633 Multiplier IC as a Varaible Gain Amplifier. I'm using the AD736 RMS-DC converter as my "detector" stage. And I'm using a difference amplifier as my error feedback. The transfer function of the AD633 as it is configured in my circuit is: (Vi*Verr)/10. For the sake of simplicity, I omitted the division from the transfer function, leaving the AD633 to just: Vi*Verr. I need my dynamic range to be quite wide: 5V - 7.5V.
My problem is that if I make my Vref = 6V, so that my error becomes 1 to satisfy a non zero output, the output isn't being adjusted to satisfy my dynamic range requirements as I change inputs. I plan to put peak limiting circuitry in on the output of this to correct the huge spikes occurring as AGC circuit is settling. How do I design this to the range that I need? Do you have any suggestions for how I can treat this more like a negative feedback control loop and solve mathematically for steady state error and such?
My problem is that if I make my Vref = 6V, so that my error becomes 1 to satisfy a non zero output, the output isn't being adjusted to satisfy my dynamic range requirements as I change inputs. I plan to put peak limiting circuitry in on the output of this to correct the huge spikes occurring as AGC circuit is settling. How do I design this to the range that I need? Do you have any suggestions for how I can treat this more like a negative feedback control loop and solve mathematically for steady state error and such?