Research On Key Techniques Of High Power Density DC/DC Power Module

DC/DC power modules are widely used in medical,communication and manufacturing.The development trend of power modules mainly includes high reliability,high power density,and high efficiency to for practical application.Compared with the common topologies,this paper studies a high-power-density cascading DC-DC converter topology with high-voltage/wide-voltage range input and low-voltage/high-current output,and carries out key techniques for this topology.Firstly,this paper carries out the design of a single module,studies the main power topology of the circuit and analyzes the working principle of the two-stage circuit.Two PIC16FXXX chips are used for controlling.The normal operation of the DC/DC converter,control signal output,working status detection,fault protection and other functions need to be completed by the chip.On this basis,a prototype is built to verify the topology and control system.Secondly,the efficiency analysis and thermal simulation of the experimental prototype are carried out.According to the idea of finite element analysis,the key components of the module are determined,and the power loss of the front and rear stage circuit under full load are calculated.The loss model of the cascade topology is established,and the efficiency curve with the input voltage is plotted.According to the actual size of the prototype and the relative position of the device,a thermal simulation model is built in the software Flotherm,and the mesh is divided into thermal simulation.The result of the thermal simulation is close to that of the actual thermal imaging,which can be used as the basis for device selection and PCB layout.Finally,for the application of high voltage/wide range input,a modular input series output parallel combination DC-DC converter based on two-stage structure and its voltage equalization control strategy are proposed.The modular unit adopts a two-stage topology of open-loop fixed-frequency LLC and closed-loop Buck,which combines high performance with serial and parallel combination.By constructing the voltage equalizing bus and indirectly sampling the input voltage of the module,the signals are superimposed on the reference voltage and the feedback voltage respectively,so that the module unit realizes the input voltage equalization self-regulation while maintaining good output voltage precision.Combined with the small signal model,the stability of the system is theoretically analyzed and verified by simulation.Finally,a combined ISOP converter consisting of three modular units is built in the lab to verify the strategy.