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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
As previously mentioned, the presumptions are unclear, for a buck converter in ccm you get the behavior described Easy peasy. It can be easily derived with pencil and paper method, similarly you should be able to determine why your simulation gives different results when you compare with theoretical behavior.
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