| The adaptability of input and output voltage range is one of the important indexes to evaluate the performance of DC power supply.Wide output range DC converter has been widely applied in the fields of spacecraft electric propulsion power supply,electric vehicles,special equipment power supply and so on.In the face of many challenges brought by the wide output voltage range,such as the huge voltage/current stress of the devices,the sharp increase of conduction/switching loss and so on,how to achieve high efficiency,high power density power supply and wide output voltage range has become a key problem to be solved.Firstly,a semi-active rectifier isolated converter is studied for wide output range applications.By introducing active switches into the secondary-side rectifier circuit of isolated step-down converters,the control freedom of the converter is increased,and it has the ability of step-up regulation,so that the converter can realize the step-up and step-down transformation.By adopting optimized dual phase-shifting control,the converter can realize soft switching over the whole output range,and the efficiency is improved.The operation principle and characteristics of the converter are analyzed in detail,mathematical model is established,and verified by simulation and experiment.Secondly,it is difficult for one single power module to achieve ultra wide output range and high efficiency over the whole output range when it is applied in ultra wide voltage range applications,and to resolve the contradiction,the power supply with online variable output technique composed of several semi-active rectifier isolated buck boost converters are proposed.The connection types of output ports would be changed according to the instantaneous value of output voltage,which can meet the operation requirements of low-voltage large current mode and high-voltage small current mode at the same time,and avoid the problem of huge voltage current stress and low efficiency caused by ultra wide output voltage range.In this paper,the realization method of online variable output structure switching circuit is analyzed in detail,and different systems are compared from two dimensions of output range and device stress.One system composed of four DC modules is taken as an example and analyzed in detail.Analysis and experimental results shows the system can reduce the stresses of devices,improve equipment utilization rate and change connection types of outpouts online,then ultra wide output range and high conversion efficiency would be achieved.Finally,to avoid current/voltage sharing control between different modules,a variable output structure three-phase DC/DC converter is studied.Automatic output voltage and current sharing can be achieved no matter in parallel mode or series mode by ultilizing the couple of three phases and adopting common phase shift control,and no more current/voltage sharing control is needed.Operation principle and characteristics are analyzed in detail.Analysis and experimental results also shows the converter can achieve automatic output voltage and current sharing. |
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