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60 Threads found on edaboard.com: Ccm Dcm
Let us assume that we have built a particular PID for a buck DC-DC converter considering the continuous conduction mode(ccm) of operation. In this case, the combined response of switch and the filter of the buck is a second order system and thus we need PID. Consider a situation where the load current drastically reduces and take a case where bu
in a real current mode buck converter, the peak inductor current is determined by the error amplifier output voltage level into the pwm comparator......you could have a certain buck converter with 0.2 duty cycle with say 10 amps peak inductor current, or you could have a buck with D = 0.8 but with only 1A peak inductor current....or vice versa, i
Please calculate power stage gain of continuous time equivalent circuit and realize that it will increase and be current dependent in dcm. Respectively a voltage controller that is stable in ccm can become unstable in dcm with insufficient gain margin.
Hello, While modelling the buck converter, which model best describes both ccm and dcm of operation? I'm trying to model in MATLAB for a ccm and dcm combined buck model. Can anyone help me with the best way here? Thanks, Rama
We have to design a flyback with the following spec? Vout = 8v Iout = 6A Fsw = 66khz Vin = 85-265VAC We would choose to do this as a ccm design, giving us a peak secondary current of 9.7 Amps. However, a certain semiconductor?s proprietory calculation software has implemented this as a dcm flyback with a NP/NS = 37/3 and LP=360uH. T
If one is designing a Current mode ccm flyback, then when the load gets lighter, such that it goes into dcm, then this dcm is always stable in current mode. (as long as it had been stable in ccm) In a ccm Voltage Mode Flyback, lightening the load such that it goes into dcm can actually (...)
Hello, The attached (LTspice sim and pdf schematic and excel design doc) show a dcm Full Bridge SMPS with Vin=390vdc Vout = 400vdc Pout = 100w Fsw = 100khz dcm The actual exact leakage inductance value in the transformer plays a big part in the design calculation. This is because the secondary side transformer leakage inductance appears
Hello, Do you agree that this 100W Full Bridge SMPS is in both ccm and dcm at the same time? Due to the magnetising current being very large compared to the power current, the current in the output inductor indicates ccm operation, but the primary current indicates dcm operation. (LTspice sim attached, also pdf schem and (...)
Hello, We are doing a Current mode, dcm Full Bridge SMPS, VIN=390VDC (PFC output) ; VOUT=400VDC max; Pout=100W max ; Application=100W LED lamp (V(LED) = 340-400VDC at 250mA); F(sw) = 100KHz Dimmable down to 10W. Mains isolation We have chosen to do the Full Bridge as a dcm Full Bridge. The reason for dcm is
As long as the converter is operating in ccm or BCM, the state space model does not depend on switching frequency at all, it's just a function of duty cycle. If you're operating across a wide load/line range which requires you use both dcm and ccm, then you will have to measure the transfer function over that wide range.
So if I try to take the absolute value of the current waveform before I take the average, the result seems correct to me now, the efficiency number in heavy load looks the same but in light load there are significant different in ccm/dcm mode, dcm efficiency is higher than ccm in light load. But I am not sure I am doing the (...)
Depends on dcm or ccm operation. No effect in ccm (continuous mode), but duty cycle is changing the loop gain in dcm, calculate yourself.
I agree dcm is a better choice for your application and it is easy to design. I think dcm has smaller transformer, Fast transient responce, Lower Stress on Diode and Mosfet, Lower EMI on other hand ccm has lower ouput capacitor, Lower ripple current, good cross regulation for multiple ouput flyback converter.
First of all excuse me for my English. What's difference between dcm & ccm overall bandwidth in flyback or forward converter? Dose overall bandwidth in ccm is narrow than dcm? or in other word compensation network at ccm is faster than dcm?
I presume that you don't yet fully understand how a buck converter works, otherwise you won't be suprised that the output voltage is not 5 V. To give a small hint, there's a point of discontinuous conduction (dcm) versus continuous conduction mode (ccm) operation. The simplidied duty cycle to output voltage translation is only valid in ccm, (...)
Comparing dcm and ccm flybacks, both in current mode, which has the higher gain of the feedback loop?...(assuming all other things equal.)
what is a non linear load? you need a certain amount of current drawn to cause ccm, but this has nothing to do with whether the load is linear or not, just how much current it is drawing. if the converter is bidirectional, then of course, when the current crosses through zero the current will pass through the dcm range before becoming ccm (...)
use a ccm method battery needs a constant current
You would need to state-space-average the switching portions to do a small signal analysis. But because the conduction mode can change, so can the model fundamentals - a tricky problem if indeed your design will see both ccm and dcm.
Critical conduction mode (CRM) means to operate a switched mode converter (e.g. buck or boost) at the boundary between continous conduction mode (ccm) and discontinuous conduction mode (dcm). The term should be clear with a few clicks on your internet browser. CRM can serve different purposes, soft switching (ZVS or ZCS) seems to be among it acc
I'm studing the flyback SMPS. The documents about flyback say about the difference between ccm mode and dcm mode, for example, primary and secondary current, transformer inductance, etc. But I cannot find any information about the difference in the topology. What is the difference? Are they same in topology, only difference in transformer ind
On page 1 of the HV9860 datasheet it says that the HV9860 is for dcm . Why is it only for dcm? Surely it can be used with ccm also? (especially if the duty cycle was <0.5 as then no slope compensation is needed) HV9860 DATASHEET
Hi, I am about to design a MPPT buck controller with a PIC micro controller. I want to implement Incremental Conductance algorithm. My question is what current value we have to use for the MPPT calculation? Because input current for the buck is pulsating (i.e. it a trapezoidal wave from in ccm or triangular in dcm ). I think using average
As shown in Brads simulation (but not analyzed in technical terms), the buck converter changes from dcm (discontinuous conduction mode) to ccm (continuous conduction mode) when increasing the frequency, which changes also the duty cycle to output voltage relation. The expectable "regular" buck converter voltage is Vout = duty cycle*Vin - Voltage
Consider a SEPIC and a flyback, each with a 1:1 coupled inductor, and each driving the same load , in either dcm or ccm, whichever you prefer. (same source resistor , output divider and control chip etc). Consider also that K=1 for the coupled inductors. ...Now note that the diode current and FET current in this SEPIC and the flyback are e
Dear All, I am designing a buck converter having the following spec: Vin=12V?10% Vout=5V(reg.) 4A≦ILoad≦20A Vripple≦50mV Now I want the converter to operate in a mixed-mode i.e. in both ccm and dcm, but the questi
It might be that your linear model is stable because it's allowed to ignore the true limits of the forward converter (duty cycle is limited to between 0% and 50%). Also the switching simulation may not be operating in ccm/dcm as expected.
The most common reason to get instabilities at low loads is the transition from ccm to dcm. Did you consider the respective gain variation?
Notice in all three types it is possible for the coil to be left conducting long enough that it reaches maximum current and acts as a resistor. That is, with a low enough frequency, and a long enough duty cycle. Perhaps it also makes a difference whether the coil is in ccm, or dcm, etc. There is a phase during dcm where the coil is idle a
But i didn't decide about continuous conduction mode or discontinuous conduction mode. Why i must use ccm ? or dcm ? What will change if i use ccm or dcm ? Which one is more benefit for for me? dcm is what you might use if you have an inductor which is larger than your load calls for. Or in case you (...)
I have to wonder if it has to do with the fact that you have two voltage feedback loops, which isn't normal in a flyback converter. Can you verify whether just one or both optocouplers are conducting when the oscillation happens? Also what is the frequency of the oscillation? When oscillating, does the converter operate in dcm or ccm? It migh
dcm mode is preferable in some situations where you have to operate over a wide line/load operating range (since with dcm the transmitted power is roughly proportional to the square of duty cycle, where as with ccm it's roughly proportional to duty cycle, to the first order), or you're operating at low power levels (where losses due to (...)
Hi everyone, I need your help in designing and controlling a DC to DC flyback converter that operate in both ccm & dcm. where to start? and what is special about these kind of converters? and will i find a ready-made transformer for such a converter? how to choose the right MOSFET? what parameters will play the role of deciding the operation mo
is it also because a dcm flyback can ALWAYS be stabilised by reducing the gain of the compensation error amplifier?.....whereas a ccm flyback may go unstable if the error amp gain is either increased or decreased?
The advantage of coupled inductors is in no-load operation. With uncoupled inductors, an unloaded output inductor goes to dcm and is no longer averaging the input voltage, the output voltage rises up to the input peak voltage. Coupled inductors share the flux between windings and keep the ccm mode waveform as long as one output is sufficiently load
I think if you observe the current waveforms for both of these mode, it would be easy to understand and appreciate. In short: Note that since all of the energy in the inductor discharges in each switching cycle during an interval shorter than the (1 – D) conduction time, the peak current in the diode must be higher in dcm than in ccm. If th
which of the following incurs the most FET switching loss? :- 1.....FET turn off in dcm flyback 2.....FET turn on in dcm flyback which of the following incurs the most FET switching loss? :- A.....FET turn off in ccm flyback B.....FET turn on in ccm flyback which of the following incurs the most FET switching (...)
The 2mm Gap will have more gap related losses, The reflected voltage on primary looks very small (54~55V) due to the selected ratio (3.21) QR flyback will be more efficient compared to normal ccm or dcm current mode flyback as it gives an zero voltage operation for primary FET & no ultrafast recovery diode required on the secondary as the operat
Hi all I designed current mode boost converter and it operates in BCM mode.(Boundary conduction) And since it is not ccm operation so I think there's no need slope compensation circuit. Isn't it? But my concern is circuit can operate with ccm mode during start-up...etc.. So in steady-state, slope compensation function is not needed. But
Hello friends. I would like to know what are the criteria that we consider to choose whether we want to operate a buck dc-dc converter in continuous inductor current mode or discontinuous mode. I have designed a buck dc-dc converter for battery a bank og lead acid batteries that I intend to connect in parallel
Hello, Please may I first state: ccm = continuous conduction mode dcm = discontinuous conduction mode do you believe some points made in "Puzzler 3" on the website are incorrect or incomplete or at least biased unfairly in favour of ccm? Puzzler 3:- For e
as the picture,the current wave ccm and dcm,how to calculate the avg,rms ? (mosfet and diode's avg,rms) thanks !
I have a simple synchronus voltage mode PWM Buck regualtor 5V to 2.5V design with load at 2.5A, it operates in ccm and it's stable. However, when the load is reduced to 250mA, the regulator is operating in dcm and it's unstable. Anyone know why and how to solve this issue.
Can anyone pls elaborate when we should choose ccm and when dcm specifically related to current mode and voltage mode control schemes for Buck and Boost type converters. Thanks a lot Arin
i have a forward Synchronous Rectifiers dc to dc converter,it's no load input current too large i observe the converter's secondary mosfet no load wave whitch go into the dcm mode,not ccm mode after renew the transformer,it's no load input current decreace about 40mA and the conver secondary mosfet wave is ccm mode in secondary mosfet's (...)
Dear All: I have some questions about dcm and ccm in DC/DC converter. Why dcm mode does not need compensation ? Does anyone know the reason ? Thanks
Friends, When a converter is operated such that it operates in ccm and dcm depending on load, my understanding is that duty cycle will have to change when the converter is in dcm as compared to when it is in ccm. Furthermore, since M(=Vout/Vin) is a function of the load in dcm, the control will have to be (...)
A flyback converter can be operated in either discontinuous current mode (dcm) or continuous current mode (ccm). With the same output power, a converter in ccm exhibits smaller peak inductor currents than one in dcm. why ? what is the relationship , or say , formula , between power and inductor current?
Could you write some others details about the converter e.g. topology (Buck, Boost, ...), feedback type (voltage mode, current mode, ...), functioning mode (ccm, dcm, ...), voltage on input/output and so on... Do you've some circuit schematic? Bye
Good day! PFC has two topology : dcm or ccm. Application of each topology is dcm for low~medium power & ccm for high power. But I don't know why. what characteristics make it?? Regards. Added after 12 minutes: And I have another question about dcm. In dcm topology, there are (...)