Research On The Control Method For Wide Range Soft-switch DC/DC Converter

In the oil exploitation, a kind of wide-range adjustable output voltage converter isneeded, it should support the equipments in the thousands kilometers long well, startwith low voltage and work with high voltage, and it also should meet the requirements,such as high voltage, high efficiency, high precision, fast dynamic response, high powerdensity and low EMI. The phase-shifted full-bridge zero-voltage converter is selected,and based on the required system characteristics under wide range load, the circuitparameters is designed, the system small-signal model is established. The controlmethod which can result in higher efficiency is analyzed.The current and voltage expressions of components is presented by analysing thecircuit operating process. It’s discussed that the reason that the topology can’t achievewide range soft-switch. Finally the control method which combine variable frequencyand auxiliary circuit is chosen. Then the needed frequency is figure out under differentload. The Pspice simulation model is established, the validity of this method is checked.The control method that can not only improve the efficiency but also achieve soft-switch under different load is discussed. The relationship between frequency anddifferent kinds of loss is presented, the PLECS simulation model which is used to provethe validity of the relation between the frequency and the magnetic loss is established.The system efficiency model including the total loss and the output power is putforward. According to the results above, the optimized frequency that can result inhigher efficiency and soft-switch under different load is figured out. And based on theminimum on-time, the highest frequency under different load and the frequencycharacteristic of the magnetic material, the optimized frequency is regulated to make thesystem operate steadily.Based on the analysis above, a power converter is developed, experimental testsare conducted, detailed data analysis is presented. The experimental results show thatthis convertor can not only achieve soft-switch but also get higher efficiency under thestated load range, and the system has good dynamic characteristics.