4 DESIGNING FEEDBACK CONTROLLERS IN SWITCH-MODE DC POWER SUPPLIES
In most applications discussed in Chapter 1, power electronic converters are operated in a controlled manner. The need for doing so is evident in electric drives used in transportation to control speed and position. The same is also true in photovoltaic systems, where we should operate at their maximum power point to derive the maximum power. In wind turbines, the generator speed should be controlled to operate the turbine blades at the maximum value of the turbine coefficient of performance. In DC-DC converters, with or without electrical isolation, the output voltage needs to be regulated at a specified value with a narrow tolerance. In this chapter, the fundamental concepts for feedback control are illustrated by means of regulated DC-DC converters.
4.1 INTRODUCTION AND OBJECTIVES OF FEEDBACK CONTROL
As shown in Figure 4.1, almost all DC-DC converters operate with their output voltage regulated to equal their reference value within a specified tolerance band (for example, 
around its nominal value) in response to disturbances in the input voltage and the output load. This regulation is achieved by pulsed-width-modulating the duty ratio 
of their switching power-pole. In this chapter, we will design the feedback ...
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