Search Engine

70 Threads found on Current Mode Loop
PWM dimming frequency is 200Hz. I change duty cycle from 10% to 1% with 10 steps equally separated, such as 10%, 9%, 8%,.....1%, within 3s. It looks flickering in the run, maybe especially at the middle of this run. What may happen? jitter of duty cycle, or overshoot of current in LED?
Hello, The LTspice simulation of a 28vin to 1V5 out, 20A out, Dual Buck converter (each buck switches at 200khz and is in CCM, current mode) shows a crossover frequency of 14000 Hertz and phase margin of 63 degrees. The excel calculation of this circuit (also attached), gives it as 9600Hz for crossover, and 53 degrees for phase margin. ?So slig
Most likely you have a large common mode noise interfering with a differential current source, sense. Try a large CM balun or ferrite sleeve or twin coupled choke to the twisted pair to raise CM impedance and thus CMRR but keep DM impedance relatively low compared to Zc(f) If that fails, reduce area of loop with a smaller gap . water has (...)
Every pin voltage should either be GND (0 ... 0.3V) or VCC (VCC - 0.3V .... VCC). Any other value shows either activity or a floating signal. Both increases power down current. It's a bit different with 8051 processors. Port 1 - 3 are open drain with weak pull-ups, the outputs must be programmed to '1' (the power-up state) and not
Hello The attached is a power supply involving eight current mode (CCM) bucks all in parallel, driving into the same load. Its easy to get the Feedback loop bode plots (& calculate gain and phase margin and crossover) for one buck supplying into one load, but how is it done for eight in parallel? Vin=28v vout = 1v5 iout = 136.8A (...)
HELLO!!!!! I want connect two microsources namely (microturbine,and DC SOURCES) with different capacities ( P1=35kW,P2=20KW) but i am using droop controller with PI.And every microsources has voltage loop ,current loop and power loop . Anyone who knows a method which i can use for achieving a good way of (...)
Hello, In a current mode flyback, compensated with a type 2 error amplifier, it is a fact that the error amplifier's high frequency pole should always be at a lower frequency than the frequency of the power stage ESR in order to assure you avoid instability Is this true? ie, ensuring the above won't assure stability but is a good and
Hi, I want to implement a digital controller for a switch mode power supply in Orcad pspice. The controller will take voltages and current values as inputs and create the control signal using intelligent algorithms (state machines, digital control techniques etc). Therefore I need a block that runs a code for processing these values (ie. C
The ZXLD1370 LED driver datasheet says that it regulates its switching frequency to 400KHz (bottom of page 5 of datasheet) However, page 14 of the datasheet states the following??.. **The control loop also regulates the switching frequency by varying the level of hysteresis (the ripple in the inductor current). The hysteresis has a d
For a Full Bridge SMPS in current mode, as opposed to Voltage mode, we can say that with current mode, we no longer suffer the double pole of the output LC stage, because current mode control cancels out one of these poles, meaning that we can more easily compensate the (...)
This is the case with regular sampling PWM, but for natural sampling PWM the phase response is very small (and can lead or lag, depending on specific conditions). I don't think that the difference matters in this relation. The sampling time can be considered as fixed for a small signal disturbance, also with natural sampling. Yo
Hi everyone, I've been trying to implement a compensated closed-loop current mode(CM) controlled boost converter using the SIMPLIS engine. However, I am having convergence issues with the simulator. Here are the converter specs I followed: Vi = 12V, Vo=18V, Io=1A, fs=100khz. To have a solid understanding of CM, I used primitive (...)
The following is a flyback with vin = 250V, VOUT = 30V, pout=22.5w, fsw=97khz, CCM, current mode. The only way to measure an effective feedback loop gain/phase plot is to put the two opamp buffers (U3 and U2) either side of the feedback loop injection resistor, R7. Do you agree? (schematic attached) The ?standard? (...)
Hello, I have the small signal feedback loop transfer function for a CCM, current mode, buckboost. (Basso book page 232,fig 2A-22) I need to adjust it so that it can be used for a flyback... -So does vout become vout*.? -does Cout become Cout*.? -does Rout become Rout.? -does Cout's ESR become ESR/[(Ns/Np)^
Presume you are transiting to DCM by decreasing the load current. Modulator gain increases with decreasing current.
You 'll notice that the oscillation occurs beyond voltage loop transient frequency. Most likely, it's brought up in the current loop. So as suggested in your previous thread, don't use uncoupled inductors together with current mode control.
Hello, The following sepic led driver regulates its own input current. spec: vin= 5 to 8v vout = 5 to 40v pout = 1 to 5w has overvoltage protection. Coupled sepic inductor. F(sw) = 30KHz - 125KHz Its peak current mode, but the main negative feedback loop is closed around the input (...)
In a bipolar stepper driver, you can measure the current with low-side shunts. You may have noticed that stepper drivers are often operated in constant current mode. In this case, measuring shunts and a current control loop will be already present in the driver circuit.
hi I am doing my course project on clock and data recovery. In that in phase aquisition loop phase detector is implemented by current mode logic.The problem is when i gave phase detector error output signal to v-i converter(Differential amplifier is one of stage used for voltage to cuurent converter) it is switching in only one side (...)
I have to calculate 1. current in each branch, 2. voltameter result 3. electromotive force (EMS) mode and 4. power bilance. And need to use four methods: Node Voltage Analysis (Node potential method) Superposition Method loop current Analysis Kirchoff's Rules Analysis I hope you can rede something or give me (...)
Hi all, I need to design a closed loop DC-DC boost converter. The specifications are: I/P Voltage: 1.8 V ? 10% O/P Voltage: 3.3 V (regulated) Load current (Max) = 100 mA The converter operates in DCM mode (full load range) L = 5 nH C = 2 nF Fsw = 200 MHz Before I really implement it in transistor level, I want to verify (...)
According to the datasheet, the device is operating in current mode. This means, there's no way to set a constant duty cycle.
Hi my friends Can i use formulas of "AN-1162" for calculate current-mode compensation network? if no, Can you give me a practical reference like AN1162 to design stable feedback loop for current-mode? I use UC3845 and TSM101A for design constant current power supply.
Considering current mode CCM full bridge smps. Why is the feedback loop easier to compensate if the duty cycle at maximum load is low (eg ~0.25-0.35)?
Well if you're designing the IC then you have more latitude to deal with the problem. Are you implementing any kind of input current shaping feedback loop at all? Average current mode control would probably deal with this issue entirely. Another possibility might be to also modulate on time along with frequency, so that (...)
77088 vdsat is very large ,will this cause any problem? this bias is used in vco. thanks very much.
Hello everybody, I need some help regarding how to go with the design of peak current mode control of boost converter. I cannot find a good reference which can really help in a recommended design procedure . So Questions like How to choose slope compensation ? how to implement current loop Finally how to implement (...)
Hello, I wish to make out a feedback loop for a CCM current mode full bridge 250W. It has TL431 /opto feedback but not with the fast lane. Basically the TL431 has been set up like a type 3 opamp. then thers the opto with secondary side led resistor and a pullup resistor on the primary side, in the standard way controller is (...)
First I recommend reading the following appnotes from venable tech: For loop compensation, you need to decide on what loop bandwidth and phase margin you need. For a given supply circuit, there are practical limitations on what can be achieved.
Audible noise usually indicates unstable feedback loop, or e.g. subharmonic frequencies that can occur in a current mode converter without suitable slope compensation.
loop current ought to result in differential mode noise, but not all current returns, some goes out the output, and the imbalance might appear to have some common mode component. To the extent that AC ground current and input current are in phase (likelier during edges (...)
Discontinuous mode means you won't have a RHP zero, or any subharmonic oscillation in current mode control. Also you get input power limiting via volt-time product limiting.
Think about a master / slave mode and a one-wire current setpoint word sent/received every N clocks. Master is the voltage mode loop and slaves are current mode.
Good day To start, I'm new and a novice to power electronics!! I build a flyback converter and the control circuit used a open loop controller. I'm using a input of 220V 50Hz and the output I need to achieve is 15.8V 1.3A for a 20W LED. I'm using the discontinious mode flyback converter. The problem is that I need a close loop controller to (...)
thanks for your replay. first of all, i will caculate the system loop transfer function when L,C current gain, slope compensation, loading is given, i will get poles/zeros, Q, and gain, then i will simulate error amplifier transfer function, and also get poles/zeros and gain, at last i will get the overall transfer function, it shows the PM >60 deg
i design an 2MHz 2.5v~5.5v input 2A output current, but when i caculator the voltage loop compensation Rc and Cc, found Rc too huge up to 2M, and Cc too small less than 2p, and i add to matlab simulation, that not stable, anyone can tell me why???
The input signals to the comparator in a current-mode buck converter are not digital pulses. But it's correct to use a comparator in this place, and you should not compensate it rather than make it fast. The output of the comparator is in fact a "digital" on-off signal, what should be the purpose of compensating a comparator? There's
The current mode control loop transfer function has a DC gain term that is proportional to Rout/Rsense. I've seen datasheets often give the formula for Rout as Rout = Vout/Iout. What if the load is actually a current source with an output impedance of R_cur_src. In this case, would we continue to use: Rout = (...)
Hi, The transient simulation of a open loop OTA shows that the output current is not proportional to input voltage, also the output voltage has decaying. The OTA has high linear range so the linearity shouldn't be the problem. I put one simulation waveform. Check the lower waveform. The input signal is sinewave and load is capacitor. I think
Could someone please clearly explain the operation of a current mode controller in an SMPS? Comparison with the voltage mode controller would be greatly appreciated. thanks ! Kanishuw
current mode means, that the inductor respectively switch peak current is controlled by an inner control loop. It doesn't necessarily involve a particular relation of this value and other process values, e.g. output current, secondary transformer current, whatever. A voltage (...)
Hi, I am using PIC 18F1330 microcontroller for my battery charging application. Here I am controlling Battery current in CC mode & Battery voltage in CV mode in closed loop. But here in CV mode my battery current & Pulse is varying. Below are the details of my code. (...)
hello, how did u get 87% efficiency with KiloAmp pulses happening? i wouldn't have thougt voltage mode was worth thinking about...unless its got current limiting...but u say no current sensing anywhere? in some countries, no engineer help any other at all, the poor guy who designed that probz now sacked and slogging away 16 hours a (...)
Hi, I am working on Peak current mode DC-DC converter.I am using OPAMP based current sesing technique to sense the High side switch current when the switch is ON.The technique seems to work very well until the offset is introduced in the OPAMP.Due to this, the loop saturates as the OPAMP -ve terminal can (...)
voltage mode is slower than current mode...............and often used with smps's with lc filters in output............. you wont manage to get good phase margin and gain margin if you go to high in freq for your UGXF. also, having ugxf for any converter means you are more susceptible to noise. if your ugxf is near F(sw)/2 then (...)
the pwm ic voltage mode can be seen a 1/vm model (vm is pwm ic ramp voltage peak value). if the pwm ic is current mode,how to build the model?
Do you agree with me that this is outrageous? Not at all. You may want to learn about operation principles of current mode controllers. After reading some of your posts discussing various application circuits: You should rather doubt your level of knowledge than considering all engineers to be fools.
Can someone give me a clue about the maximum duty cycle and minimum on time of voltage-mode DC-DC buck converter? I konw there is maximum duty cycle and minimum on time for current-mode DC-DC converter, they are dependent on CLK signal, but for voltage-mode, it seems has nothing to do with CLK signal, so does this mean there (...)
hi i want to simulate a current mode DCDC controller control loop in frequency domain for an openloop bode diagram, and for a closed loop output impedance. how can i model the current control loop? the model has to reflect the (...)
I am designign a DC DC current mode buck , but the load transient is too large, what parameter can effect the behavior ? Error Amp gm ? or bandwidth , or compensation network RC, or zero , pole? Does any article discuss this topic ? And if load transient improves , usually the stability becomes worse, what is the best trade-off ?