Research On Efficiency Optimization And Loop Characteristics Of Two-stage DC/DC Power Supply Module

In rencent years, the rapid progress of information technology has been promoting related network power industry to flourish. Because of the adoption of distributed power architecture in the network power system, the DC/DC power supplies fed by a backplane bus therein must adapt to a wide range of input voltage, and be designed in industry-standard modular in order to achieve N+1 redundant parallel operation to improve the reliability of power system. Benefit from the semiconductor industry being still in "Moore's Law Times", the performance of semiconductor power devices improve significantly, while their costs continue to decrease. Therefore, the DC/DC power modules adapting to a wide range input voltage have tended to use two-stage DC/DC architecture. For the medium-to-large output power modules, more attention should be paid to their thermal and dynamic performances, which requires key consideration about efficiency optimization in the design process, and more precise model analysis of the loop characteristics to guide the control parameter configuration. In a word, the research of these two aspects in this paper is of theoretical significance and engineering value.A full-brick two-stage DC/DC power module consisting of synchronous BUCK and full bridge topologies is developed in this paper, which adapts to 36V~75V wide range input voltage and 28V/30A output, utilizing ADP1043A (taking advantage of its multiple configurable PWMs by accurate timing, and its ability to coordinately control a two-stage DC/DC) to implement full digital control.In the respect of efficiency optimization, the current sharing design of parallel winding about the center-tapped planar transformer, the suppression of parasitic body diode reverse recovery in synchronous rectifier, and the achievement of soft-switching in full-bridge are studied in this paper. Additionally, the influence of synchronous BUCK output inductance on the efficiency of the BUCK stage is demonstrated, obtaining the optimal value of filter inductance at the rated input voltage, which improves the efficiency of BUCK stage and inhibits the reverse recovery of the free-wheeling tube to some extent.Based on the three-terminal PWM switch circuit average method and the model of cascade two-port network, a small-signal model of two-stage DC/DC considering the parasitic resistance is developed, the loop characteristics involving ADP1043A is analyzed, and the filters is optimized, so as to provide a theoretical basis for the controller parameter configuration under voltage-mode control. In addition to that, the characteristic of input-voltage feed-forward is analyzed, and effective improvement is made to the flyback topology of auxiliary power supply for access to the input-voltage feed-forward.Finally, an efficiency of over 95% at full load and 95.7% at half load is illustrated by the test results of this full-brick prototype, with the implementation of better dynamic performance as well.