An Autotuning Method Based on System Identification for Digitally Controlled Synchronous Buck Converter

To improve the dynamic performance of buck converter and ensure the stability of the system for a wide input range and uncertain peripheral power stage device parameters, including parameters drift due to aging, a new autotuning method based on system identification (SI) is proposed. In the proposed algorithm, first, the power stage parameters are estimated by SI. Second, a corresponding compensated range is obtained based on the power stage parameters. Third, all sets of PID controller parameters are calculated based on three principles: 1) maintaining user-specified stability margin; 2) considering integral-based no-limit-cycling criteria; and 3) ensuring single-crossover-frequency operation. Fourth, an optimal set of PID controller parameters required a minimum closed-loop output impedance among those of the above all sets of compensation parameters are chosen. The algorithm based on field-programmable gate array (FPGA) is verified in a 5-V input to 1-V/5-A output prototype. Compared with a normal compensated method, which compensates the poles with zeros completely under the same setting phase margin, the maximum undershoot and overshoot voltages are reduced from 130 to 80 mV, 110 m to 70 mV; and the response time reduces from 120 to 80 μs and 100 to 80 μs, respectively. Moreover, stability and good transient response are achieved by using the proposed method for the system with different power stage parameters simulating device parameters drift due to aging.