UCC28600_14 Datasheet, PDF (23/32 Pages) Texas Instruments – 8-Pin Quasi-Resonant Flyback Green-Mode Controller

UCC28600
www.ti.com
SLUS646J – NOVEMBER 2005 – REVISED JULY 2011
Begin the design of the R²CD using the same procedure as designing an RCD snubber. Then, add the damping
resistor, R_SNUB2. The procedure is as follows:
Pick
DV_SNUB
V_R
+
between 0.5
and
1
(6)
Select a capacitor for ΔV_SNUB:
C_SNUB
+
ǒ_VR
I _cs(peak)2L _LEAK
) DV_SNUB^Ǔ2 *
V_R2
(7)
Pick R_SNUB to discharge C_SNUB:
ǒ Ǔ ǒ Ǔ R_SNUB1 +
1
2
)
V_R
DV_SNUB
1
C_SNUB
f
1
S(max)
*
L_LEAKI_CS(peak)
DV_SNUB
(8)
2
é
é
ùù
( ) P R_SNUB1
=
æ
çè
V_R
+
DV_SNUB
2
2
ö
÷ø
´
ê
ê₁₊
ê
êë
æ
èç
1
3
ö
ø÷
´
ê
ê
ê
êë
1
V_R
V_SNUB
+
1
2
úú
úú
úú
úû úû
R_SNUB1
(9)
Pick R_SNUB2 to dampen the L_LEAK-C_SNUB resonance with a Q that is between 1.7 and 2.2:
R_SNUB2
+
DV_SNUB
I_CS(peak)
(10)
È¡
È£
ȧȧȧȢ _{ǒ Ǔ}ȧȧȧȤ _{PǒRSNUBǓ + ICS(peak)2RSNUB2}
1
3
L_LEAKf_S(max)
V_R
)
DV_SNUB
2
(11)
For the original selection of ΔV_SNUB,
Ǹ Q +
2V_R
DV_SNUB
)
1
(12)
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