AN2852

Main characteristics and circuit description

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bus and D is the duty cycle. For stability reasons related to the topology, the IC limits the

maximum duty cycle at 50%. The current in the primary tank circuit is read by the controller

thanks to the sense resistors R81 and R82. The self supply is basically obtained thanks to

an auxiliary winding on the AHB transformer. A small charge pump on the auxiliary windings

of the PFC inductor helps during the startup phase. A pin dedicated to startup sequencing, a

spare latched protection (dedicated here to output overvoltage protection), the soft-start

function, the overload protection, an interface with the PFC controller and the integrated

high-voltage startup generator complete the features of the L6591. All the functions and

protections are detailed in the following sections.