| High efficiency and high reliability module power supply is widely used in aeronautics,aerospace and defense military industry.In the low-voltage power supply system of weapons and equipment,the output voltage of power source fluctuates widely,while the stability of voltage is required by the later-stage equipment.Based on this background,a DC power module with 1/4 brick size,16V～40V input voltage and 28V/300 W output is developed.Influenced by the current international political and economic situation,the power module developed in this paper is designed based on domestic devices.First,the current-fed topology contains only one second-order filter.The input voltage can be pre-regulated by the front voltage regulator circuit,which facilitates the device selection and optimal filter design of the back-stage converter.There are no problems such as slow dynamic response and large size of the traditional two-stage topology.Therefore,the current-fed Buck cascade converter is selected as the research object.On the basis of detailed analysis of the working principle of the topology,the working modes of the diode rectifier and the synchronous rectifier in light load are compared.To solve the problem of high loss in light load of the synchronous rectifier structure,the average inductance current is used as the control value to synchronize the energy or energy-losing side rectifier driver so that the converter works in DCM mode in light load.The drive control sequence of the front Buck and the secondary rectifier is designed to prevent the system from damaging the circuit due to energy backfilling when switching on and off.Secondly,in order to improve the dynamic response of the system,the circuit uses a voltage-current double-loop structure controlled by peak current.The peak current control principle of current-fed converter is analyzed in detail,and slope compensation is designed to eliminate subharmonic oscillation.The basic modeling method is used to model the small signal of the converter,and the current loop is combined with the power level according to the average inductance current equation.An accurate model of the equivalent power level of the current-fed Buck cascade converter is established,and a fifth-order compensator is designed to compensate and correct the system.To achieve high-precision peak current control,a low-delay differential amplification current sampling circuit is designed based on a high-bandwidth,low-offset operational amplifier.Then,the inductance,transformer and filter capacitance parameters of the main power circuit are calculated according to the parameters.The drive circuit,protection circuit and auxiliary power circuit are designed for the system,and the devices used are selected domestically.In addition,in order to reduce the internal noise of the power module and improve the heat dissipation capacity,the device layout and power wiring of the PCB layout are optimized.Finally,based on the design,an experimental prototype of DC power module is developed,and its conversion efficiency is kept above 92% in the full input voltage range and full load condition.The correctness of the theoretical analysis and the feasibility of the scheme are verified according to the final experimental and test results. |
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