Digital PFC Description
12.3 EVM Hardware – Introduction
12.3.1
PFC Pre-Regulator Input
The power entry section, PFC pre-regulator input, as shown in
, consists of EMI input filter, AC
voltage sense circuit and inrush relay control circuit. The series resistor R3 limits the inrush current. The
inrush control relay K1, controlled by the UCD3138 controller, is used to bypass this resistor. The
controller measures input and output voltages and decides the appropriate time for closure of this relay.
Input AC voltage is scaled and conditioned, and the sensed signal is applied to the UCD3138 ADC input
AD_07 and AD_08.
also shows a DC voltage regulator D3, which converts the 12 V into 3.3 V
to provide the bias for on-board 3.3 V.
Figure 31. AC Power Filtering, Inrush Current Limit and AC Voltage Sense
29
SLUU885B – March 2012 – Revised July 2012
Digitally Controlled Single-Phase PFC Pre-Regulator
Copyright © 2012, Texas Instruments Incorporated
