UCC28750 has dedicated fault pin
to disable IC by external signal. In high power
application, the main power stage controller uses MCU or has house keeping IC,
so customer can disable Aux power when the PSU triggers the protection or the
sequence requirement. Customer can short FLT pin to
GND to disable IC easily by MCU GPIO signal.
The main power stage like PFC and
LLC or PSFB is very noisy and Auxpower can be modular at daughter card then
closes to the main power stage components. UCC28750
is CCM controller, and is less sensitive than QR flyback controller, because QR
flyback controller needs to sense the Auxwinding voltage to achieve the valley
switching and input and output voltage detection.
IC supports the power boost mode
to increase the switching frequency up to two times so IC can avoid the
transformer saturation during peak load, and the IC control law as Figure 4-1. In Auxpowr application, the main output
loading is bias power for Fan, and has peak load requirement to speed up the
thermal dissipation.
UCC28750 is the economical
flyback controller in TI.