© 2012 Fairchild Semiconductor Corporation
13
FEBFL7730_L20H008A • Rev. 0.0.2
6.4.
Open/Short-LED Protections
In short-LED condition, the OCP level is reduced from 0.7V to 0.2V because the FL7730
lowers the OCP level when V
S
voltage is less than 0.4V during output diode conduction
time. The output current in the short-LED condition is less than 1.5A, which doesn’t
damage any external components.
Figure 16.
Short-LED Condition – V
IN
[220V
AC
], C1 [V
CS
], C2 [V
DD
], C3 [V
IN
], C4 [I
OUT
]
In open-LED condition, output voltage is limited around 32V by OVP in V
DD
. The output
over-voltage protection level can be controlled by turn ratio of auxiliary and secondary
windings.
Figure 17.
Open-LED Condition – V
IN
[220V
AC
], C1 [V
CS
], C2 [V
DD
], C3 [V
IN
]
