TABLE OF CONTENTS Converter systems invariably require feedback. For example, in a typical dc-dc converter application, the output voltage v( t) must be kept constant, regardless of changes in the input voltage v g( t) or in the effective load resistance R. This is accomplished by building a circuit that varies the converter control input [i.e., the duty cycle d( t)] in such a way that the output voltage v( t) is regulated to be equal to a desired reference value v ref In inverter systems, a feedback loop causes the output voltage to follow a sinusoidal reference voltage. In modern low-harmonic rectifier systems, a control system causes the converter input current to be proportional to the input voltage, such that the input port presents a resistive load to the ac source. So feedback is commonly employed.
A typical dc-dc system incorporating a buck converter and feedback loop block diagram is illustrated in Fig. 7.1. It is desired to design this feedback system in such a way that the output voltage is accurately regulated, and is insensitive to disturbances in v g( t) or in the load current. In addition, the feedback system should be stable, and properties such as transient overshoot, settling time, and steady-state regulation should meet specifications. The ac modeling and design of converters and their control systems such as Fig. 7.1 is the subject of Part II of this book.
