POWER ELECTRONICS – PAGE 16
Continuous & Discontinuous Conduction Mode
1️⃣ What is Conduction Mode?
Conduction mode depends on whether load current becomes zero or not.
- CCM: Current never becomes zero
- DCM: Current becomes zero before next triggering
2️⃣ Continuous Conduction Mode (CCM)
Current flows continuously throughout cycle.
- Occurs when L is large
- Energy stored in inductor keeps current flowing
- Smoother current waveform
- Better power factor
Conduction angle = 180° (or more in RL case)
3️⃣ Discontinuous Conduction Mode (DCM)
Current becomes zero before next cycle.
- Occurs when L is small
- Load current drops to zero
- Higher ripple
- Poor power factor
4️⃣ Critical Condition
Boundary between CCM and DCM is called:
Critical Inductance (Lc)
If:
- L > Lc → CCM
- L < Lc → DCM
5️⃣ Waveform Comparison
CCM:
- Current never touches zero
- Smooth waveform
DCM:
- Current falls to zero
- Gap appears in waveform
🎯 GATE / PSU Important Points
- Identify waveform type
- Understand role of inductance
- Know effect on average voltage
- Critical inductance concept
Very Important: Increasing inductance shifts operation from DCM to CCM.
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