A new frequency compensation scheme for current-mode DC/DC converter

This paper presents a new frequency compensation scheme for current-mode DC/DC converters. The proposed compensation scheme includes the miller capacitance control unit and dynamic zero control unit. The miller capacitance control unit uses a small compensated capacitance Cm to establish a big capacitance. Therefore, the system´s transient response is improved as the fast charge or discharges on the small on-chip capacitance Cm. The dynamic zero control unit uses a NMOS which operates in triode region to act as a voltage controlled linear resistor. As the control voltage varies with the load current, it will generate a dynamic zero to cancel the pole ω₁. Therefore, the system´s stability is greatly improved. Simulated in a 0.18-μm CMOS process, the proposed compensation scheme achieves full range alternating current stability from 0 to 450mA load current and improves the transient response with 150mV voltage variation and 10μS settling time for a 250mA load step.