Datasheet

UCC28250
SLUSA29C –APRIL 2010– REVISED JULY 2011 www.ti.com
Design Steps
Step 1, Power Stage Design
The power stage design in this example is standard and the same as that for symmetrical half bridge converter of
voltage mode control. From the standard design, these components are determined. This includes Q1 through
Q4, C1, C2, CT1, D1 and D2, D3, T1, T2 and T3, and U6. Their design is standard. Also, design associated to
current sensing and protection is also standard. This includes CT1, D1, D2, R5 and C5.
Step 2, Feedback Loop Design
D3 (TLV431) with U6, R6, R9, R10, R12, R13, C11 and C12 are composed of standard type 3 feedback loop
compensation network and output voltage set point. Their design is also standard.
Table 1. Specifications for the Design Example
PARAMETER MIN TYP MAX UNITS
V
IN
Input voltage 36 48 72
VDC
V
OUT
Output voltage 3.3
P
OUT
Outpu power 75 W
I
OUT
Output load current 23 A
C
OUT
Load capacitance 5000 µF
f
SW
Switching frequency 150 kHz
P
LIMIT
Over-power limit 150%
η Efficiancy at full load 90%
Isolation 1500 V
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