The stacked power system: a new power conditioning architecture for mainframe computer systems

A comprehensive system-level analysis is presented, and a systematic design procedure for a stacked power system is established. An effective load impedance of each converter is identified, incorporating all subsystem interactions in the system. Using the effective load impedances, the system is decoupled into three individual converters. The effective load impedance of the decoupled converter is simplified to a resistive value, an equivalent resistive load. The control loop of each converter is designed individually using its equivalent resistive load. It is shown that this design procedure offers a good small-signal performance and very stable transient responses for the entire system. To verify analysis results and to illustrate the design approach, computer simulations are performed in both frequency and time domain. Frequency-domain simulations are performed using ASTAP with a small-signal model of the system. Time-domain simulations are performed using EASY5 with an exact nonlinear model of the system