Development Of Secondary Power Supply For Vehicles

With the progress and the development of the automobile industry, on-vehicle electrical equipments are used more popular and power consumption is becoming more larger than ever before, even the total power of some additional vehicle equipment can be tens of kilowatts. In order to ensure that the vehicle electrical equipments work safely, continuously and reliably, it is necessary to put higher and stricter requirement on the quality of the power supply. As the on-vehicle power supply system works independently, it is required higher efficiency in order to avoid the waste of power and increase battery life. For battery DC converter system, the phase-shifted full bridge ZVS circuit topology is used, with the controller TMS320F28335, which can make the control be high-speed, flexibility and intelligent. The efficiency of the converter can be increased with the soft switching technology.The thesis makes a deep research on phase-shifted full bridge ZVS converter. Phase-shifted full bridge ZVS converter is a DC/DC converter with excellent properties. The switching devices of two legs of the converter all work at ZVS condition, which results in less switching loss. The features such as constant frequency control, simple circuit structure, conform to the development trend of miniaturization and high frequency. The operational principle and characteristic of the phase-shifted full bridge ZVS converter are analyzed in detail. The circuit simulation and configuration are also given in the thesis.The thesis adopts a revised phase-shifted full bridge converter. A passive auxiliary circuit has been added into the traditional converter. The revised converter uses the energy stored in the auxiliary inductor to achieve ZVS over almost full load range, which makes the resonant inductor relatively small. So, there is no severe duty ratio loss and severe voltage ringing across the output rectifier. As the duty ratios of the auxiliary inductor and the transformer are complementary, the amplitude of the current in the auxiliary inductor can be self-adaption change depending on load condition, which avoids unnecessary circuit losses.Finally, on the basis of theoretical analysis and software simulation, a3.4kW engineering prototype of phase-shifted full bridge ZVS converter is designed. The experimental results show that the revised phase-shifted full bridge converter can work excellently, achieving ZVS over almost full load range.