ABSTRACT:
This paper presents a new soft-switching technique for
the current-fed full-bridge DC-DC converter that enables zero voltage switching
of the input side inverter switches. To achieve this, the secondary side
voltage doubler rectifier has to be realized with active switches. Two control
channels synchronous with the control signals of the inverter switches are
added for driving those switches. Zero voltage switching achieved is assisted with
the body diodes that conduct current during soft-switching transients as a
result of the leakage inductance current shaping from the secondary side. Moreover,
the converter does not suffer from voltage overshoots thanks to natural
clamping from the secondary side. Theoretical predictions were verified with simulation.
KEYWORDS:
1.
Zero-voltage switching
2.
Current-fed DC-DC converter
3.
Full-bridge
4.
Soft-switching
5.
Switching` control method
SOFTWARE: MATLAB/SIMULINK
CIRCUIT DIAGRAM:
Fig.
1. Galvanically isolated full-bridge current-fed DC-DC converter with controlled
output rectifier stage.
EXPECTED SIMULATION RESULTS:
Fig.
2. Simulated current and voltage waveforms along with control signals
of
the input and output side switches.
Fig.
3. Experimental current and voltage waveforms.
CONCLUSION:
The novel ZVS
technique intended for the galvanically isolated full-bridge current-fed DC-DC
converter with the controlled output rectifier stage were presented. It enables
full ZVS in the input side current-fed inverter assisted with the leakage
inductance and body diodes. Moreover, partial ZCS is provided in the secondary
side assisted with the leakage inductance. Simulation study corroborates the
theoretical predictions made. Experimental prototype operation was quite similar
to the simulation model created in PSIM. Nevertheless, the prototype features
oscillations caused by parasitic elements of the circuit and reverse recovery
of the body diodes the input side MOSFETs. Further research will be aimed
towards derivation of design guidelines that take into account reverse recovery
effect and, consequently, result in high efficiency and low parasitic
oscillations.
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[3]
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[4]
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