Digital Predictive V²C Peak Controlled Buck Converter With Current Observer

To solve issues of increased cost, noise, and delay caused by current sensors in traditional <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$V^{2}C$</tex> control, a digital predictive <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$V^{2}C$</tex> peak control algorithm with the current observer is proposed. Firstly, based on the geometric characteristics of inductor current and output voltage ripples, the peak and valley values of inner loop feedback voltage are stable within the same switching cycle, which effectively eliminates the subharmonic oscillation that occurs under trailing-edge modulation. The control voltage of the inner loop can be followed by inner loop feedback voltage within two switching cycles. Secondly, a current observer is constructed based on the ripple characteristics of the inductor current, which estimates the inductor current according to the input voltage, output voltage, and duty cycle. Furthermore, the discrete-time nonlinear model of the Buck converter system under the proposed algorithm is derived, and the critical equivalent series resistance (ESR) value for system stability is calculated using Jacobian matrices. Simulink simulation results demonstrate the correctness of the theoretical derivation of the critical capacitor ESR. With low capacitor ESR <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(20\mathrm{m}\Omega)$</tex>, the converter system with the proposed algorithm remains stable and exhibits good dynamic response performance, while <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$V^{2}$</tex> peak control occurs low-frequency oscillation. Compared with voltage-mode control, the dynamic response time for load change is reduced by 55.56%, and for line voltage change is reduced by 66.67%.