1. Modeling of Dc-dc Boost Converter in Discontinuous Conduction Mode
Hafez Sarkawi (D1)
2016/06/20

2. Presentation Outline Introduction DCM Operation
General Dc-dc Converter Averaged State-space DCM Model
Dc-dc Boost Converter DCM Model
Conclusion and Future Works

3. Presentation Outline Introduction DCM Operation
General Dc-dc Converter Averaged State-space DCM Model
Dc-dc Boost Converter DCM Model
Conclusion and Future Works

4. 1) Introduction
The purpose of the dc-dc boost converter circuit is to draw power from the dc voltage source, and supply power to the load at a higher dc voltage value.
This task is accomplished by first closing the switch to store energy in the inductor, and then opening the switch to transfer that energy to the capacitor, where it is available to the load.
The discontinuous conduction mode (DCM) occurs when the converter is at light load (low current).
Fig. 1 Dc-dc boost converter circuit

5. Presentation Outline Introduction DCM Operation
General Dc-dc Converter Averaged State-space DCM Model
Dc-dc Boost Converter DCM Model
Conclusion and Future Works

6. 2) DCM Operation
DCM operation : the inductor current rises in the first interval when the switch is turned on, reaches a peak right before the switch is to be turned off, and resets to zero at the end of the second interval and remain zero until next switching occur.
Fig. 2 Inductor current waveform in DCM
Fig. 3 Three different modes for the DCM boost converter

7. Presentation Outline Introduction DCM Operation
General Dc-dc Converter Averaged State-space DCM Model
Dc-dc Boost Converter DCM Model
Conclusion and Future Works

8. 3) General Dc-dc Converter Averaged State-space DCM Model
Piecewise-linear state-space model for the three different modes:
Averaged model using SSA for above modes

9. Presentation Outline Introduction DCM Operation
General Dc-dc Converter Averaged State-space DCM Model
Dc-dc Boost Converter DCM Model
Conclusion and Future Works

10. 4) Dc-dc Boost Converter DCM Model
State vector chosen for the dc-dc boost converter:
State and input matrices:
Averaged SSA DCM model:
(1)
Needs to be eliminated. Solution:
Reflect using current and voltage

11. 4) Dc-dc Boost Converter DCM Model (Cont.)
Average inductor current
Peak inductor current
Subs. d2 into (1)
New averaged SSA DCM model:
(2)

12. 4) Dc-dc Boost Converter DCM Model (Cont.)
DC analysis
Small signal analysis
Subs.
Using standard linearization techniques to (2), small signal model is given by:
into (2) and solved for and

13. Presentation Outline Introduction DCM Operation
General Dc-dc Converter Averaged State-space DCM Model
Dc-dc Boost Converter DCM Model
Conclusion and Future Works

14. 4) Conclusion and Future Works
Modeling of dc-dc boost converter operating in DCM has been presented.
Future works will deal with the application of these modeling for dc-dc zeta converter and apply robust control technique to stabilize the converter.

15. Thank you!
Hafez Sarkawi (D1)
2016/06/20