| Summary: | 碩士 === 國立雲林科技大學 === 電機工程系碩士班 === 101 === A mixed mode control full-bridge dc-dc converter with variable output function is presented on a microcontroller and an analog controller in this paper. The implemented converter achieves zero voltage switching and reduces duty cycle loss, circulating loss and the switching voltage stress by introducing a resonant inductance and clamping diodes. Moreover, the use of synchronous rectification in the secondary side of the transformer actually reduces the conduction loss, and the overall efficiency is improved.
The analog controller, Texas Instruments UCC28950, is adopted to implement phase shift pulse width modulation and synchronous rectification. The Renesas Electronic Microcontroller RX62T is used to perform a variable reference voltage which is sent to analog controller to control output variable voltage. They construct the mixed mode control system with programmable output voltage, so the system could operate on high frequency, and the system size also could be reduced.
This thesis describes the operating principle of the circuit, design procedure of entire circuit and zero voltage switching of operating conditions. And the experimental results show the proposed 1120W zero-voltage switching phase-shifted full-bridge dc-dc converters is workable, moreover, it prove that the power switch can achieve zero voltage switching in the specifications. The efficiency at 20% load is higher than 80% , and at full load, the efficiency can reach 96%. The results confirm that implemented converter actually conforms the standard of Energy Star.
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