This application note describes the LinkSwitch-II product LNK605DG in a tapped-inductor non-isolated buck converter configuration that is used in LED driver applications. A tapped buck topology is ideal for converters with a high ratio of voltage input to voltage output: It provides current multiplication on the output, making it possible to use this variant of a buck topology in applications requiring output currents greater than twice the device current limit.
This topology lends itself to a smaller PCB size, a smaller inductor core size, and greater efficiency (80%, worst-case load) than an isolated ﬂyback converter. EMI filtering is simpler due to less common-mode noise generation. This topology normally requires a clamp circuit on the primary side. However, by virtue of the 700 V MOSFET integrated to U1, the clamp circuitry is not necessary.