Compensator design for control loop

[bhuvankanade12@gmail.com]

Dear All,
I am new in feedback system designing & designing a control loop with op-amp.
I have come across concept of COMPENSATOR Designing to stabilize system & implementing poles & zeroes in system for that. 8-O
But how to design it & not able to find any good document on this topic ?:-(
Can u suggest me some links for that which will be help full for compensator designing using op-amp?
:?:

 

[varunkant2k]

I am sure you must be knowing opamp comensation. Would you tell us in more brief , what kind of control loop you are working.
Generally, System is made single pole system in your required bandwidth for the compensation.

 

[bhuvankanade12@gmail.com]

I am sure you must be knowing opamp comensation. Would you tell us in more brief , what kind of control loop you are working.
Generally, System is made single pole system in your required bandwidth for the compensation.

Thanks varunkant2k,

Ya i want to build an error amplifier which compares reference voltage & monitored voltage, finally controls the output voltage.
I have searched & come across a ckt but not able to understand it how they have designed it & avoid over-under shoots.
After some goggling i have noticed its an compensator so would like to
understand it & how to design it.
Is there any documents for it ??
I am attaching ckt diagram. but components values are not exact.

Thanks once again....

 

[varunkant2k]

As much I understood, this is precision full wave rectifier. It just make a dc shift to your monitored voltage. SO this is giving you an error voltage, now you can control this by using PWM circuit or by directly controlling the output switch.
Now your question " regarding compensation" . The circuit already employes type II compenstaion ( forget this). Circuit feedback adds 2 zero and 2 poles to stabilize the OPAMP close loop.
There will be certain poles at the OPAMP output, you just need to adjust feedback R and C to make the system stable. ( to make 1 pole in the unity gain bandwith or 2 pole at rare case)
This you can do by cancelling few poles from created zero form feedback r/c combination.

 

[LvW]

Dear All,
I am new in feedback system designing & designing a control loop with op-amp.......

Question: What does it mean "control loop with op-amp"?
1.) Are you designing a classical control loop consisting of a device to be controlled, a controller (compensator) and an opamp as error amplifier?
2.) Or is your question related to an opamp with gain fixing feedback only?

 

[bhuvankanade12@gmail.com]

As much I understood, this is precision full wave rectifier. It just make a dc shift to your monitored voltage. SO this is giving you an error voltage, now you can control this by using PWM circuit or by directly controlling the output switch.
Now your question " regarding compensation" . The circuit already employes type II compenstaion ( forget this). Circuit feedback adds 2 zero and 2 poles to stabilize the OPAMP close loop.
There will be certain poles at the OPAMP output, you just need to adjust feedback R and C to make the system stable. ( to make 1 pole in the unity gain bandwith or 2 pole at rare case)
This you can do by cancelling few poles from created zero form feedback r/c combination.

Thanks a lot for your prompt reply .........
This is very useful information. :-D
To adjust feedback R & C is an trial & error method, because i have tried it.
Is there any short cut method ??:roll:

So would like to study & design it.........
But how to decide which type of compensator to be used in which system ??
is there any rule of thumb ??
Is there any design procedure for that if i want tu design it from scratch ?
Any document or link which will help me to design & understand it.:roll:

---------- Post added at 14:38 ---------- Previous post was at 14:31 ----------

Question: What does it mean "control loop with op-amp"?
1.) Are you designing a classical control loop consisting of a device to be controlled, a controller (compensator) and an opamp as error amplifier?
2.) Or is your question related to an opamp with gain fixing feedback only?

I want control a device.
& op-amp is used as an error amplifier & compensator.
So i would like to design it & understand type of compensator & its designing.
i.e type 1,type 2 & type 3 compensator.
Is there any document or link which will guide me to design compensator & designing procedure ??

thanks

 

[LvW]

Within a control loop a compensator is used to correct/shape the loop gain with the aim to give the closed loop the desired behaviour (stable and with good control properties).
That means: Without knowledge of all loop components (transfer functions, pole/zero distribution) it is not possible to select a particular compensator device.
In this context: What is the meaning of the circuit provided with your first posting? This is not a simple error amplifier. Why do you have selected this type of circuit?

 

[bhuvankanade12@gmail.com]

Within a control loop a compensator is used to correct/shape the loop gain with the aim to give the closed loop the desired behaviour (stable and with good control properties).
That means: Without knowledge of all loop components (transfer functions, pole/zero distribution) it is not possible to select a particular compensator device.
In this context: What is the meaning of the circuit provided with your first posting? This is not a simple error amplifier. Why do you have selected this type of circuit?

Is this not a simple error amplifier with compensator then what is the functioning of it ?? :shock: :sad:
During my study i have come across sample circuit whose application is similar to mine. So should be able to use this circuit as it is.
But i am facing problems in over shoot, under shoot, response time and all, I am not able to tackle it until i know how to design it.
So looking forward for your help & support.
Thanks in advance.

 

[LvW]

As mentioned already, without knowledge of the device to be controlled (transfer functon) it does not make sense to select an error amplifier and to discuss its properties. Sorry.

 

[bhuvankanade12@gmail.com]

As mentioned already, without knowledge of the device to be controlled (transfer functon) it does not make sense to select an error amplifier and to discuss its properties. Sorry.

Dear Sir,

My controlled device is MOSFET & want to control its drive.
So that i can control terminal voltage & current of MOSFET & use it as DC Load.
That is DC Electronic load.
I am mainly stuck in designing of compensator in CV mode.
So would like to design it......
Is there any design procedure, technical documents, method for that if i want to design it from scratch ?


Thanks a lot....