UCC28950_15 Datasheet, PDF (51/74 Pages) Texas Instruments – UCC28950 Green Phase-Shifted Full-Bridge Controller With Synchronous Rectification

www.ti.com
UCC28950
SLUSA16C – MARCH 2010 – REVISED NOVEMBER 2015
8.2.2.10.1 Voltage Loop Compensation Recommendation
For best results in the voltage loop, TI recommends using a Type 2 or Type 3 compensation network (Figure 50).
A Type 2 compensation network does not require passive components C_Z2 and R_Z2. Type 1 compensation is not
versatile enough for a phase shifted full bridge. When evaluating the COMP for best results, TI recommends
placing a 1-kΩ resistor between the socpe probe and the COMP pin of the UCC28950.
V_OUT
V_REF
C_Z2
R_I
R_D
R_Z2
R
EA+
+
EA-
C_Z1
R_Z1
1 k:
C_P1
R
When evaluating COMP, for best results put
a 1-k: resistor between COMP and probe.
Figure 50. Type 3 Compensation Evaluation
Compensating the feedback loop can be accomplished by properly selecting the feedback components (R5, C1
and C2). These components are placed as close as possible to pin 3 and 4 of the UCC28950. A Type 2
compensation network is designed in this example.
Calculate load impedance at 10% load (R_LOAD):
V²
R
LOAD
=
OUT
P
OUT
´
0.1
=
2.4 W
(127)
Approximation of control to output transfer function (G_CO(f)) as a function of frequency:
G_CO(f ) »
DV_OUT
DV_C
= a1´ CTRAT ´ ^RLOAD
R_CS
´
æ
ç
è
1+ 2pj ´
1+ 2pj
f ´ ESR_COUT
´ f ´ R_LOAD ´
´ C_OUT
C_OUT
ö
÷
ø
´
1+
S(f )
2p ´ f_PP
1
+
æ
ç
è
S(f )
2p ´ f_PP
ö²
÷
ø
(128)
Double pole frequency of G_CO(f):
F
f
PP
»
SW
2
= 50kHz
(129)
Angular velocity:
S(f ) = 2p ´ j ´ f
(130)
Copyright © 2010–2015, Texas Instruments Incorporated
Product Folder Links: UCC28950
Submit Documentation Feedback
51