Modeling and simulation of low duty ratio buck synchronous converter under large load current switching

This paper presents the spice simulation of low duty ratio synchronous Buck converter under large load switching conditions. The voltage regulator module (VRM) in this category uses multiphase synchronous Buck converter for supplying large load currents. The low duty ratio Buck converter causes larger peak-peak ripple, therefore, the two-loop control scheme is used for achieving desired voltage and current performance. The input and output voltages in the VRM simulation are respectively 8.5 V and 1V respectively. The simulation circuit uses a single phase equivalent circuit for simulation with double capacitors in the input and output circuits to account for actual values used per phase. The simulation circuit uses a parasitic inductor at the input side to account for the copper trace and the module connector pin. The output circuit uses an inductor L2 of 0.38 uH to reduce The dc average equivalent circuit of a single phase converter (also known as the dc transformer) is shown in Fig. 2.D is the duty ratio. I_O is the load current. Figure 3 shows the two phases of the Buck converter with all parasitic components. the output current ripple. The load current swing is considered 12 A which is equivalent to 24 Amp switching in the actual 2-phase module. The simulation shows that by selecting low ESR capacitors a 0.06% output voltage transient can be achieved for 13-25 Amp load switching.