PFC SPM
®
Design Guide
© 2005
Rev. 1.0.1-2012
Fairchild Semiconductor – System Engineering Group
4
Over Voltage Protection
OV (Over Voltage) protection can be also implemented by dual protection. The DC-link voltage
changes slowly because of its large capacitance. So OVP does not need fast response. Therefore it is
optional to activate the OVP of PFC controller.
[OVP Level 1 - PFC controller]
OVP level 1 suppresses voltage overshoot in transient situation. It
doesn’t generate fault out signal.
[OVP Level 2 – PFC SPM®]
The voltage level of OVP level 2 is higher than that of OVP level 1.
When OV situation happens, the PFC SPM stops operating and generates fault out signal during fault-out
duration time(set by C
FOD
). And then it works again.
Under Voltage Protection
IGBT gate will be interrupted when control voltage drops below UV trip level, and the protection will be realeased
automatically if the control voltage recovers to the UV reset level.
Fig.2 Timing chart of protection function
