Texas Instruments UCD3138PSFBEVM-027 User Manual page 36

Description of the Digital Phase-Shifted Full-Bridge Converter
Reporting a fault includes the appropriate setting of the PMBus alert line, status byte, and status word.
Faults and warnings are reset by toggling the unit off and then on. Alternatively, as long as the system
does not latch off, the Clear Faults button clears any faults or warnings (see
warnings are also cleared by toggling the control line the on-off switch.
12.4.6.2 Cycle-By-Cycle Current Limit
Current transformer T2 senses the primary-side current.
is used for cycle-by-cycle current limit, peak-current-mode control, or flux balancing of the main
transformer. The primary-peak current is limited within the primary MOSFET current ratings by the cycle-
by-cycle current limit. R31 and C17 are used as a low-pass filter before the current signal feeds to the
UCD3138. The current signal is sent into UCD3138 through AD06 to create cycle-by-cycle current-limit
control. To prevent switching spikes from triggering the comparator, a blanking time is programmed.
36
Using the UCD3138PSFBEVM-027
Figure 31. Faults and Warnings
Figure 32. Cycle-by-cycle Current-Limit Sensing Circuit
Copyright © 2013, Texas Instruments Incorporated
Figure
Figure 32 shows the sensing circuit. This current
Submit Documentation Feedback
www.ti.com
31). Faults and
SLUUAK4 – August 2013