Quantitative feedback synthesis for non-linear switched-mode uncertain regulators†

The dynamically non-linear nature of switching power supplies makes if difficult to predict their transient waveforms and thereby ensure that the system operates reliably ; i.e. that peak voltage, current and power stress levels do not exceed component design limits. Significant component uncertainty, line and load variations are important troublesome factors. There has recently been developed a ‘ quantitative feedback theory ’ (QFT) which permits analytical design of feedback systems for such highly non-linear uncertain devices. This paper applies QFT to the switching power supply problem. A preliminary study involving the turn-on transient of a buck-boost regulator confirms that QFT can be successfully applied to switching regulator design, The technique accommodates large component, load and line variations, guaranteeing performance within a specified range of acceptable responses under turn-on/turn-off and step-load transients.