Study Of Isolated Buck-Boost Bi-directional DC/DC Converter With Digital Phase-shift Control Method

The isolated Buck-Boost bi-directional DC/DC converters promising for low voltage and high current on the low voltage (LV) side and high voltage conversion ratio applications. Energy management and control of converters need to be implemented by digital processor. The isolated Buck-Boost Converters include isolated Current-fed and Voltage-fed converter which current-fed converter on the LV side and the voltage-fed converter on the HV side, and include Boost integrated voltage-fed converter which boost integrated voltage-fed converter on the LV side and the voltage-fed converter on the HV side.The isolated Current-fed and Voltage-fed converter, it is well known that any current-fed type converter has no capability to limit the switch current during start-up before the output bus voltage has been established and sharp voltage spike appears at devices due to the leakage inductance. A novel phase-shift control scheme for bi-directional dc/dc converter is proposed in this paper. High voltage spike problem and star-up problem which are inherent in current-fed converters are resolved, zero-current-switching (ZCS) is achieved for all the switches at current-fed side, and zero-voltage-switching (ZVS) is also achieved at voltage-fed side. The control scheme of converter is implemented by Si8250 MCU, the operating principle and the experimental verifications are presented in this paper.The isolated boost integrated voltage-fed converters promising for medium applications. It also can construct a multi-input converter, which composed a stand-alone photovoltaic generating system combine with photovoltaic cell in this paper. A novel stand-alone photovoltaic lighting system of electrode-less lamp is proposed in this paper. Compared with the traditional stand-alone photovoltaic lighting system, this system merely use one Multi-input DC/DC converter control the battery charge or discharge effectively, protect battery and prolong its natural life. Energy management and digital control of converter are implemented by one MCU. The system is analyzed in detail, and the experimental verifications are also presented.