Figure 19: 200W Evaluation Board Circuit.

T= primary: 75 turns of litz wire 20 x 32 AWG (0.2mm)

secondary: 8 turns of # 27AWG (0.15mm)

core: B1ET3411A THOMSON - CSF

gap: 1.4mm for a total primary inductance of 0.7mH

NOTE:

Start Up Circuit

drawing current from the rectified mains. In the evaluation board

instead the start up circuit composed by (Q2+R19+R15+Dz) has

been designed to perform a fast and effective supply in all the

conditions. Once that the L4981A/B has started, the reference

voltage available at pin 6 by R20 and Q3, ensures Q2 to be turned

off.

Programmable Under voltage Lockout

The PCB allows to insert a couple of resistor (R22, R23) to modify

the threshold input voltage. Please refer to fig. 16 and table1.

L4981A - L4981B

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