Mixed-signal PI controller in current-mode DC-DC buck converter for automotive applications

This paper proposes a fully-integrated solution for the PI compensation circuits in current-mode DC-DC converters used in automotive applications. In such applications, the switching frequencies are low and hence conventional PI compensation circuits employ large capacitors. The proposed analog/mixed-signal PI comprises an analog proportional amplifier and a digital integrator. The analog proportional amplifier provides the required response time and maintains system stability. The digital integrator block is used to eliminate the output voltage steady-state error. Simulink is used to model the proposed DC-DC buck converter on the system level. The proposed system is verified by full system level simulation. The digital part is synthesized with HDL coder and laid-out using 0.35 μm CMOS technology. The estimated silicon area of the proposed solution is about 0.1 mm
²
. This result highlights the simplicity and the capacity for integration of the proposed control loop along with its potential for seamless implementation into pre-existing solutions with minor modifications.