| Abstract |
Optimal control techniques are used to design a linear quadratic regulator (LQR) for quasi-resonant
(QR) switching DC-DC converters with voltage-mode control. The method presented in the paper is
based on small-signal models that were obtained as an extension of the state-space averaging models
of PWM converters. These models show that the LQR structure has some similarities with currentmode
control, since they both introduce feedback paths for the inductor current and the output
capacitor voltage. However, whereas the feedback gains of current-mode control are fixed, with the
LQR these gains can be calculated in order to minimise a quadratic cost function. Moreover, it is
possible to design the LQR and the power stage of the QR converter interactively. Small-signal
models of the QR converters are reviewed and the optimal LQR for voltage-mode control is
presented. The process was experimentally tested and results from a prototype of a 1 MHz buck QRZVS
converter with a LQR are presented. |
