AN-9750 Datasheet, PDF (5/13 Pages) Fairchild Semiconductor – High-Power Factor Flyback Converter for LED Driver with

AN-9750
APPLICATION NOTE
Over-Voltage Protection (OVP)
The OVP prevents damage in over-voltage conditions. If the
V_DD voltage exceeds 23V at open-loop feedback condition,
the OVP is triggered and the PWM switching is disabled. At
open-LED condition, V_DD reaches V_{DD_OVP}. Then, auto-
restart sequence causes a delay, limiting output voltage.
Over-Temperature Protection (OTP)
The built-in temperature-sensing circuit shuts down PWM
output if the junction temperature exceeds 150°C. There is
hysteresis of 10°C.
Figure 13. Waveforms at Short-LED Condition
At short-LED condition, V_S is low due to low output voltage.
Then, OCP level is changed to 0.2V to reduce output current.
© 2011 Fairchild Semiconductor Corporation
Rev. 1.0.3 • 5/15/12
5
www.fairchildsemi.com