At first glance, the buck converter (Fig. 10.1) looks like a very attractive topology for creating a LDD. Compared to other topologies, it contains a minimal number of parts: just one power switch Q1, one filter inductor Lf, and one freewheeling diode D1. It can work in a continuous conduction mode with PWM and regulate the average current within a wide range. By using a corresponding inductor Lf, the current ripple in the LD could be minuscule. Moreover, the converter has a high dynamic output impedance due to this inductor.
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