BUCK QUASI-RESONANT ZVS CONVERTER WITH LINEAR FEEDBACK CONTROL: A COMPARISON WITH CURRENT-MODE CONTROL

摘要

Quasi-resonant (QR) DC-DC converters can be controlled with either voltage-mode, or current-mode control, which leads to similar advantages to those that occur in the case of PWM converters. In this paper, a linear feedback control law for QR-ZVS converters is compared with current-mode control. Instead of using the instantaneous value of the current, the linear feedback control uses the average of the inductor current. This is an advantage, since a noiseless and non-distorted sample of the current becomes more difficult to obtain with high switching frequency. Optimal control techniques are used to design a linear quadratic regulator (LQR) for a buck QR-ZVS converter. The method is based on averaged small-signal models and it is shown that the dynamic responses with the LQR can be similar to those obtained by current-mode control. Experimental results from a 1 MHz QR-ZVS buck converter with a LQR are presented.