Questions tagged [control-loop]

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4 votes
2 answers
121 views

Operational amplifier using power supply current as output [closed]

I have come across a circuit (I am not allowed to share it) with an opamp that uses a special output. The opamp's output is loaded with a resistor and has no other connection. It is the current drawn ...
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0 votes
0 answers
37 views

Buck loop transfer function

I saw two types of buck loop transfer function from two sheets, and the difference is the second type didn't consider H(s) from compensation network. Here is the first type, error-amp with ...
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0 votes
1 answer
55 views

Differences in current loop transmitter

I'm studying loop powered transmitters (the 4-20mA thing), because I need to make one. I've found two different reference design which mostly use the same technique but with some slight difference. ...
0 votes
1 answer
164 views

Please help me clear up this confusion regarding gain margin and phase margin and unity feedback

I understand the physical significance of gain and phase margin. However, I would like some clarification regarding the mathematical aspects. Videos such as the following: https://www.youtube.com/...
0 votes
2 answers
199 views

Grinding on PI/PID controller at specific PWM

I've modified a previous PI controller of a design team on that is working on high speed motor applications to include the D, which didn't solve this issue. The PID loop takes actual speed, and ...
0 votes
0 answers
51 views

what is the open and closed loop function of this system?

i found this in the text book. i solved by: 1- found the closed loop function of just the part of B(p) and its "feedback", let's call it B'(p). 2- after that i did H(p) = A(p) / ( 1 + A(p) * ...
3 votes
2 answers
151 views

Comparator as operational amplifier

Using an operational amplifier as a comparator was asked quite a lot times here, but how does it behave the way around? I've a really cheap one in my circuit with low hysteresis and a MOSFETt push/...
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1 vote
1 answer
95 views

Is it possible to find the voltage gain of the constant gain block of this control system?

I'm looking at the following circuit and I don't know how to find the gain of the constant gain block. The only information I'm given are the Bode plots (magnitude and phase) of the two transfer ...
  • 31
0 votes
1 answer
1k views

How to prevent algebraic loop in the control loop simulation?

I have been developing a simulation of the field oriented control of the three phase induction motor. The simulation is developed in the Scilab/Xcos (v5.5.2) which is a free of charge Matlab/Simulink ...
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1 vote
0 answers
41 views

Solving PLL Loop BW Transfer Function

𝑍(𝑠)= (1+𝑠.𝐢2.𝑅2)/(𝑠.(𝐴3.𝑠^3+𝐴2.𝑠^2+𝐴1.𝑠+𝐴0) C2 = 0.0000001F R2 = 1000 Ohm A0 = 0.000000106034 A1 = 1.27859848E-12 A2 = 4.5011166848E-18 A3 = 4.31278848E-24 G(𝑠)= (𝐾𝑝𝑑.πΎπ‘£π‘π‘œ.𝑍(𝑠...
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0 votes
0 answers
61 views

Dutycycle DCDC control

I will start with that, i already ask for this question in other topic but i didn't have any anwser about my question link. Please don't go too far in explaning difficult thing not realated with my ...
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0 votes
1 answer
114 views

Closed loop equation initial value

I am doing math for a closed loop equation. I know the transfer function for a closed loop system is: (Image copied from "Loop Gain and its Effect on Analog Control Systems" by Gabino ...
  • 59
2 votes
2 answers
579 views

Nyquist stability criterion for positive feedback

it is known that the stability of a system with negative feedback may be analized through the Nyquist stability criterion, which is based on observing the number of turns around the point (-1;0) in ...
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3 votes
1 answer
343 views

PFC controller - How does it work?

I would like to better understand how a PFC controller works, especially PFC which work in CCM mode. I found the following documentation from International Rectifier: https://www.infineon.com/dgdl/an-...
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0 votes
2 answers
3k views

Confusion regarding root locus. Open loop or close loop?

Which transfer function ,open loop or close loop do we use/need as a pre req to perform root locus analysis? I have also attached a snapshot of the relevant webpage of university of Michigan. I have ...
  • 477
1 vote
2 answers
787 views

MOSFET as heating element for a RaspberryPi

I developed a PID autotuning algorithm that I want to test outside of a simulation environment. For this purpose, I got temperature sensors to send data to a RaspberryPi. Now I need something to ...
  • 115
2 votes
1 answer
148 views

Trouble understanding Loop Filter in a PLL

I'm currently trying to understand the function of a loop filter. But where I'm stuck is that I know the output of the charge pump is a series of current pulses whose width is proportional to the ...
3 votes
2 answers
846 views

What does Dominant pole/Pole mean related to capacitors and filters or Electronics in general for intuitive understanding

I am trying to understand the feedback compensation techniques of DC-DC Buck converters. And I drift to more and more small questions which make me want to understand the basics of poles/zeroes/...
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0 votes
1 answer
195 views

Poles and Zeros of a Transfer Function

I am trying to understand the physical meaning of poles and zeros of a transfer function. Can someone help me how to understand the Figure 2b in the link below? What does the height of the cone ...
  • 3,422
2 votes
1 answer
1k views

Loop compensation of a Buck Converter

I have a buck converter. TPS54260 Vin = 7V-20V Vout = 5V Iload=600mA. I realise that there is a similar question in this forum but I was not able to get clarity. I want to understand what do you ...
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0 votes
2 answers
710 views

Cascaded current control

I have a actuator capable of measuring motor current and position via an encoder on the output shaft. The motor is a brushed DC motor running through a gearbox. My questions is in regards to the use ...
2 votes
2 answers
1k views

Transfer function of phase change controlled with capacitance

We have an RLC series circuit with sinusoidal voltage source of frequency \$\omega\$. The normal transfer function of current to voltage is: $$ G(s) = \frac{I(s)}{V(s)} = \frac{1}{R+s L+ \frac{1}{s C}}...
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0 votes
2 answers
503 views

Loop bandwith and open-, closed- loop gain in ADIsimPLL

I'm want to use ADIsimPll to calculate the loop filter properties for a PLL I want to build. I read some things in the programs help topics which I find somehow strange. Maybe you guys can help me out ...
0 votes
1 answer
120 views

Any transfer function has the same denominator 1+T

Sometime ago, I came across some theory saying that in a control loop any transfer functions such as ...
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0 votes
2 answers
162 views

What exactly am I messing up in this control loop?

I am creating a simple control loop for a safety door for a machine. When the door is opened, the machine turns off. When its closed, the machine can operate. The way I have it set up now is that we ...
-1 votes
1 answer
149 views

feedback loop for a single stage offline flyback that is powering 2 independent LED strings

I have a design that is a offline, single stage flyback, powering two different LED strings. The output of this converter is about 50W and the output voltage can range from 20V-45V. I'm using ST ...
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0 votes
2 answers
680 views

How to find the closed loop transfer function of the LT1619 current mode controller

I am trying to figure out what would be the closed loop transfer function of the LT1619 controller. This is the first step I want to make in order to design the feedback loop. What I already know ...
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1 vote
3 answers
482 views

Interpreting the open loop gain of a linear power supply

This question is related to a question asked earlier regarding a linear power supply build. It turns out that the circuit is oscillating quite badly; an issue not uncommon in feedback circuits. I've ...
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0 votes
1 answer
583 views

How do I get a closed-loop PID controller from a transfer function?

I have the transfer function below: $$T_c(s) = \frac{s+k_i}{m_0s^3+s+k_i}$$ It is assumed that \$k_p=1\$ and \$k_d=0\$. I am given that \$x_l(t)=[x_l(t),y_l(t)]^T\$ is the trajectory and the ...
1 vote
2 answers
941 views

Positive feedback with constant transfer functions

If I have a control loop with positive feedback, the closed loop transfer function expression is: $$\frac{Y(s)}{X(s)} = \frac{P(s)}{1-P(s)H(s)} $$ where \$P(s)\$ is the direct loop transfer function ...
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7 votes
1 answer
207 views

What is a Jaffe-Rechtin PLL?

Eberhardt Rechtin and Richard Jaffe (both involved in NASAs DSN) published this paper (paywalled) on PLL-design and -performance back in 1955. It is referenced quite often, so I wanted to understand ...
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1 vote
0 answers
70 views

Digital PLL reference noise rejection

I have a fully digital implementation of a PLL. The problem that I have is the white noise coming from the PFD (you can view it as input jitter). I would like to filter it a lot, but an implementation ...
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1 vote
3 answers
17k views

Why does the opamp output voltage saturate?

simulate this circuit – Schematic created using CircuitLab Vout = Vin (1 + R2/R1) According to this positive feedback topology - made an error here, it's Vout = Vin(-R2/R1) (edit) Now I read ...
0 votes
1 answer
834 views

DC-DC boost converter using multisim. Output voltage keeps changing with input voltage

Link to circuit schematic simulation The circuit is from the above link. There is some problem with the control loop. The output voltage doesnt stay constant within the input range of 12-24v for ...
1 vote
1 answer
590 views

Loop Bandwidth of PLL

How is the loop bandwidth of a PLL calculated? Is it the area under the Transfer Function vs. Frequency plot?
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6 votes
1 answer
1k views

Loop compensation design of buck converter

I am trying to design loop compensation with type-3 error amplifier for a buck converter. I'm a student and very inexperienced in this subject. Please bear with me. Here is the general procedure ...
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2 votes
2 answers
2k views

Root locus of discrete time system

I have a question about a probably easy task, but I can't find the right K. I have the loop with an adjustable gain element given: $$Q(z) = \frac{H(z)}{1+ K\cdot G(z)H(z)} $$ I have given: $$H(z) ...
2 votes
2 answers
459 views

Where is the pole introduced by the RC circuit?

I've implemented a circuit under a suggestion which solves stability issues when driving a MOSFET with an high capacitance, using an OpAmp. Now, the circuit suggested is this one, in which is modeled ...
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9 votes
4 answers
9k views

How to achieve very accurate/fine rotation with motor

I am running an experiment where I need to rotate a lightweight dial (<5 grams, so very low torque requirement, and fairly slowly), but need to do very accurate, fine steps of 0.03 degrees. ...
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0 votes
1 answer
83 views

Software control system. Which one is it?

I wrote a software which replaces a discrete closed loop PI control circuit and now I was wondering what kind of control system is this equivalent to? This code drives the PWM which regulates the R_DS,...
6 votes
1 answer
3k views

How to improve current control loop in power supply?

I'm working on MCU programmable bench power supply. Its range is 0-50V and 0-3A programmed in 10mV and 10mA increments. It will be published as open hardware and source code that anyone can use it if ...
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0 votes
3 answers
748 views

Step response to feedback loop with disturbance

When using step response to a feedback loop with disturbance. Why do we analyze the step response of the disturbance D and the step response of the input R separately. Instead of considering them ...
1 vote
1 answer
722 views

loops with C18 Compiler on mplabide for 18f4550

I am facing trouble with glowing multiple LED simultaneously on a 18f4550 micro-controller under the same " while(1) ". I am new programming. [C18 compiler with Mplab ide.] I was able to alternate ...
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3 votes
2 answers
601 views

Confusion in feedback for switchmode dc/dc converter

I have a slight confusion in how the feedback pin works. The "\$V_{ref} \times (1 + R_1 / R_2)\$" seems like a shortcut to me, and I have trouble understanding how to feed a voltage in to it, to say ...
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7 votes
4 answers
7k views

Does this voltage regulator use "on-off" control, or is it a voltage follower?

In Electronics A2 (GCE), we are currently studying voltage regulators. An example voltage regulator circuit is provided using an op-amp and a power MOSFET. I would judge this to be a voltage ...
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