FAN3506 Datasheet, PDF (8/16 Pages) Fairchild Semiconductor – PC SMPS Secondary Side Control IC

FAN3506
4. Programmable Shunt Regulator
IK
V5
V12
15
2
3
16 VREF
PWM IC
(KA38XX) 8
1
2
PC300-2
PC300-1
R1
0.11k
IK
15
R3
R4
10k
39k
R2
1k
C1
103
C2
224
16
VREF
R5
4.7k
R6
1k
The core of the circuit equals to KA431(LM431) and Vref1 is trimmed to ±2% (2.45V ~ 2.55V) and it is for corrective output
voltages (+5V/+12V). + 5V/ + 12V output voltages are determined by the resistor ratio of R3, R4, R5, R6.
A photo coupler is used in order to control PWM IC in the primary side. R1 determines the bias current of the shunt regulator
and 110Ω is appropriate value. The resistor value can be changed by set condition and requirements.
C1 and R2 , C2 are the compensation circuit for stability.
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