Effects of non-ideal compensators for the high-bandwidth low-standby-power computer v-core converter applications

The stringent requirements on both the control bandwidth and the supply standby current make it tough to design the IC controllers for the v-core converters in future computer applications. The effects of the non-ideal characteristics of the finite gain-bandwidth product and non-zero output impedance of an operational amplifier (OP) are investigated for such a purpose. The results show surprising behavior, including the possibility of generating new complex poles and a positive zero in the compensator gain transfer function. That may affect the converter feedback stability margin. Increasing the OP bandwidth performance may alleviate this problem but that is usually achieved at the expense of supply standby power which is increasingly a critical consideration. The results developed in this paper allow better optimization of the OP used in a controller IC. Several commonly-used compensator types are analyzed. Simulations and experimental results are used for verification. Two practical DC converter examples are used for illustration.