Controll current of PWM signal

[Nikola010]

I started some project, and i wonder how to controll current when it isnt a clear DC voltage, it is PWM since i control motor and i use PID regulation. Can this circuit do the work or it must be modified and how to modified it? Ofcourse i send L741 output to and gate with PWM i have and than output of and gate controll that transistor.

 

[chuckey]

You do not state your problem very well. Your circuit seems to be a ultra high current amplifier trying to pass current into Rs - .1 ohms - is this correct? You talk about a motor, I can not see it on your circuit. You talk about current controlling PWM, is this in generating the PWM?
Frank

 

[crutschow]

You are showing a linear constant-current circuit which is not normally used with PWM. For PWM control of the current, you use the voltage across Rs to control the duty-cycle of the PWM modulator and use the PWM signal to drive the transistor gate (with a suitable gate driver circuit).

Note that you need a free-wheeling diode (cathode to plus) across the motor when you drive it with a PWM signal.

 

[dick_freebird]

You can control whatever you can feed back. Begin with
what you want, and how you will sense it. PWM happens
at the back, usually, and you need to figure out how to
get the quantity of interest, to where the front (error amp)
can "see" it and thus control it.

 

[Nikola010]

I am sorry i wasnt clear enough. I have big circuit, and i wanted to implement this circuit in it. There is H bridge actually and H bridge goes through resistor of 0.1ohm to ground. My question is if i use PWM on gates will this circuit on picture do the job to controll current eaven if it is pulsing not constant? Will op-amp sense voltage good?

 

[crutschow]

Why are you not using the PWM signal to control the current?

 

[Nikola010]

Why are you not using the PWM signal to control the current?

Becouse only way i know to do that, when i dont know voltage, becouse it will be from 20 to 100V, is on that principe of that schematic.
And second i allready used pin for PWM on PIC and i have that pic

 

[crutschow]

You need to post a schematic of your PWM circuit. What is controlling the PWM duty-cycle?

 

[picgak]

I started some project, and i wonder how to controll current when it isnt a clear DC voltage, it is PWM since i control motor and i use PID regulation. Can this circuit do the work or it must be modified and how to modified it? Ofcourse i send L741 output to and gate with PWM i have and than output of and gate controll that transistor.

Inverting input should be Ref voltage , You should connect a diode in series with the output for the above cct to work. PWM signal should be connected after the diode

 

[crutschow]

Inverting input should be Ref voltage , You should connect a diode in series with the output for the above cct to work. PWM signal should be connected after the diode

What Ref voltage?
What's the purpose of the diode?
You can't connect a PWM signal after the diode. If you do then the op amp circuit won't do anything.