Design and Implementation of On-board Electrical Power ... - OUFTI-1

duty cycle is determined by the output voltage. In other kinds of converters, the duty cyclecan be determined by the input voltage if a stabilized input voltage is needed, by the inputcurrent, or by the output current.Figure 5.1: Block diagram of an output voltage controlled converter.”Buck” converter [16]PrincipleThe power stage of the buck converter is composed of a switch, an inductor, and a capacitor(Fig. 5.2). The switch is in position 1 during a time interval DT s (phase 1), and in position2 during an interval D ′ T s (phase 2), with D ′ = 1 − D. D is called the duty cycle. T s is theswitching period, and f s = 1/T s is the switching frequency. The voltage V s is equal to theinput voltage V in when the switch is in position 1 and equal to zero when the switch is inposition 2.Figure 5.2: Power stage of a buck converter.The DC component of V s is equal to DV in . The inductor and the capacitor form a lowpassfilter. As a consequence, the DC voltage V out on the load R is equal to DV in . The Buckconverter is able to convert a voltage to a lower voltage, with a better efficiency than linearconverters, especially if the difference between V in and V out is important. The ratio betweenthe output voltage and the input voltage is49