Electronics > Projects, Designs, and Technical Stuff
AGC without phase shift
mikerj:
--- Quote from: sanwal209 on February 14, 2019, 02:06:01 pm ---I have tried to simulate couple of AGC in Tina TI but it does introduce phase shift
--- End quote ---
Show your circuit. Do you really mean you are seeing significant phase shift between input and output signals, or are you actually talking about the response time of the AGC circuit? A simple JFET AGC circuit should introduce negligible phase change at such low frequency.
sanwal209:
Hi Guys,
Sorry for late response, Let me explain the requirements.
Main scope of project is to convert single phase to three phase output. Output should be sync with the input phase. Yes, I know we can simply make inverter and do the job but our output current requirment is 1mA@220V. With this power rating inverter will be an over kill. Output is used to excite the coils so that other sensor board will be able sense.
Solution i thought is to downgrade 220Vmains to 1V(or less) fed it into two phase shift register and i result we will have low voltage 3 phase output which then fed into power amplifier and output of power amplifier will drive transformer to create isolated 3phase output.
AGC is required to keep constant voltage output after downgrading 220V mains so that any fluctuation will not effect the output.
I have attached some circuits which i simulated and got the phase shift.
Jeroen3:
You can do this digitally. Just use a phase locked loop with a DAC waveform generator.
https://dsp.stackexchange.com/questions/52981/synchronize-a-software-waveform-generator
sanwal209:
Yes, Everything can be done on digital level but we want to do it in analog as we dont have resources for firmware development.
Marco:
Opamp peak detector -> low pass filter -> drive the output of the low pass filter every so slowly to 1V by changing the gate voltage of a JFET variable attenuator with an opamp circuit, negative feedback and very very low bandwidth.
This will have the response time on the order of seconds and there's no real way to avoid it without going digital, no phase shift though.
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