# Conduction Mode Questions

Discussion in 'Homework Help' started by crazyengineer, May 23, 2012.

1. ### crazyengineer Thread Starter Member

Dec 29, 2010
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Hello! I'm preparing for my power electronics course in the fall. However, I keep coming across the terms discontinuous conduction mode and continuous conduction mode. Can anyone please explain to me more indetail the difference between these modes? What are they referring to when the mode is either continuous or discontinuous?

2. ### Jony130 AAC Fanatic!

Feb 17, 2009
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We have a very simply case here.
Continious Current Mode (CCM) means that current through inductor flows continuously throughout the switching period (always >0).

Discontinuous Current Mode (DCM) means that current through inductor reaches zero before the end of the switching period (when switch is OFF)

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3. ### t_n_k AAC Fanatic!

Mar 6, 2009
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It's true that current conduction is often subject to inductance such as as in switching circuits. The analysis of a circuit is often done on the basis of whether the conduction is continuous or dis-continuous. There are instances where current flow is dis-continuous & where inductance isn't a contributing factor. For example the diode current in an AC-to-DC rectifier with load filter capacitance is often dis-continuous.

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4. ### t_n_k AAC Fanatic!

Mar 6, 2009
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My last comment on rectfiers needs some qualification. Without a load filter capacitance the diode current still goes to zero for a small fraction of the AC cycle. With load filter capacitance included the zero current interval can become substantial. The diode current resembles more a series of pulses rather than unipolar half sinusoidal waves - as with a bridge rectifier supplying a purely resistive load.