AN2485

Main characteristics and circuit description

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mainly by the film capacitor C7 which allows for a less costly electrolytic to bear only the DC

part.

At start-up the L6563 is powered by the Vcc capacitor (C12) that is charged via the resistors

R3 and R4. The L4 secondary winding (pins #8-11) and the charge pump circuit (R5, C10,

D5 and D4) generate the Vcc voltage powering the L6563 during normal operations.

The divider R32, R33 and R34 provides the L6563 multiplier with the information of the

instantaneous voltage that is used to modulate the boost current. The instantaneous voltage

Forward) pin. Divider R9, R10, R11, R12, and R13 is dedicated to sense output voltage

while divider R6, R7, R8, and R24 is dedicated to protect the circuit in case of voltage loop

failures. The Line-Modulated FOT is obtained by the timing generator components D6, C15,

R15, C16, R16, R31, and Q3.

The board is equipped with an input EMI filter designed for a 2-wire input mains plug. It is

composed of two stages, a Common Mode Pi-filter connected at the input (C1, L1, C2, C3)

and a Differential Mode Pi-filter after the input bridge (C4, L3, C5). The board also offers the

possibility to easily connect a downstream converter and test the interface signals managed

by the L6563.