Two-stage DC/DC Converter For Low-frequency Pulsed Load Applications

Power supply system is an important part of spacecrafts and defense equipments,and it is the key to ensuring the safe,stable and reliable operation of various loads.One type of load such as new radar exhibits strong pulsed load characteristics because of its own operating states and operating modes,which means the peak power is much higher than the average power during load operation and this kind of loads has a short duty cycle,narrow pulses,and fast start-stop speed.Such strong pulsed loads’ characteristics are obviously different from traditional loads’,which bring many challenges to the efficient,stable and reliable operation of various aerospace power systems.In order to eliminate the adverse impacts of pulsed power on the power system and achieve lowfrequency pulsed power decoupling,this paper analyzes the configuration of power decoupling techniques.Based on this,a pulsed power decoupling scheme based on a two-stage DC/DC converter is adopted.By disposing the decoupling capacitor on the intermediate DC bus provided by the twostage power supply,and allowing the bus voltage working in widely fluctuated state,this scheme can buffer the pulsed power and reduce the capacity requirement of the decoupling capacitor.Aiming at coping with the challenges brought by the periodic wide fluctuation of the decoupling capacitor voltage,a dual half-bridge phase-shift DC/DC converter is selected as the front-end converter.The working principle and characteristics of the converter are analyzed in detail,and key parameters and design methods are given.Besides,in order to suppress the input current ripple,the front-end converter’s model is established,and the output voltage and input current dual-closed-loop control scheme is adopted.Then,the regulators of inner and outer loop are designed,and the output voltage feed-forward control is adopted to further suppress the input current ripple.Moreover,the alternating phase-shift control method is adopted to realize the thermal stress equalization of the front-end converter.For the back-end DC/DC converter,this paper gives the selection basis of circuit topology and control strategy.The dual Buck topology is adopted,and the key parameters and design methods are given.The output voltage and the inductor current dual-closed-loop control scheme is adopted and the regulators of inner and outer loop are designed.Finally,an experiment prototype of pulsed power supply with two-stage decoupling scheme is fabricated and tested and its average power is 320 W.The experimental results under different load conditions show that the two-stage pulsed power supply scheme studied in this paper can effectively achieve the decoupling of pulsed power,which verifies the correctness of the theoretical analysis and controller design in this paper.Besides,the result of efficiency comparison indicates that the two-stage decoupling scheme has the advantage of high efficiency.