Optimum Design of Switching Regulators by means of Computer-Aided-Design Technique

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Switching regulators consist of two stages; one is a power conversion stage, and the other is a feedback-control stage. Several kinds of circuits such as buck, boost and buck-boost converters are used as the power conversion stage. On the other hand, a multi-loop control method is proposed as opposed to a conventional control method. In this multi-loop control method, not only the output voltage, which is the conventional feedback signal but also the reactor current, or the output current, or the differential value of output voltage are used as controlled variables.In this research, at first, a design method for an output filter composed of a reactor and a smoothing capacitor has been investigated which has much influence on the stability of boost and buck-boost converters. The characteristics of the power-conversion stage can be obtained precisely by the state-space-averaging method except the skin effect and proximity effect of reactor, and the effect of parasitic inductances of the … More circuit. Therefore, the design method for the output filter has been accomplished by using the predetermined expressions of the static and dynamic characteristics in the conventional case that the output voltage is an only control variable. However, the dynamic stability which is a constraint to the design of LC filter strongly depends on the method of feedback control. Especially, the stability of switching regulators can be improved considerably by adopting the multi-loop feedback technique. This research has investigated the multi-loop feedback technique where a reactor current is sensed equivalently by integrating the voltage across the transformer in the buck-boost converter, and it has been clarified analytically and experimentally that the multi-loop feedback technique can expand the stable region of the converter and miniaturize the smoothing capacitor. Furthermore, it is shown that the multi-loop feedback technique is superior for the stability improvement and the noise immunity to the conventional PD(proportional+differential) control technique used widely. Next, a basic characteristic has been revealed analytically for a resonant converters which has the prominent features such as high efficiency and low noise at high switching frequency of MHz, and these results are essential materials to develop the CAD system for switching converters. Less